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Naked siRNAs are sensitive to enzymatic degradation, phagocytic entrapment, quick renal excretion, membrane impermeability, endosomal escape, and off-target effects. Designing a safe and efficient nanocarrier for siRNA delivery to the target site without toxicity remains a significant hurdle in gene therapy. CA is a unique derivative of hydroxyapatite and a highly pH-sensitive nanocarrier with strong particle aggregation and a high polydispersity index. Strontium (Sr 2+ ), a group two divalent metal in the periodic table, has been reported for substituting calcium (Ca 2+ ) ions from the apatite lattice and limiting particle growth/aggregation. This study used strontium chloride hexahydrate (SrCl 2 ·6H 2 O) salt to develop a Sr-substituted CA (Sr-CA) nanocarrier with ∼30 nm size, spherical shape, less aggregation, homodispersity, and a fair anionic charge. Sr-CA demonstrated a large surface area-to-volume ratio, an improved cargo loading efficiency, and enhanced cellular uptake in HEK-293 cells. Moreover, Sr-CA is a pH-responsive nanocarrier responsible for its long physiological stability, efficient endosomal escape, and optimal cargo delivery within cells. These NPs have differential effects on MAPK1, MAP2K4, PIK3Ca, CAMK4, and p53 gene expression in HEK-293 cells without showing any significant cytotoxicity in cell growth properties. Gene silencing by Sr-CA-mediated siRNA delivery against MAPK1, MAP2K4, PIK3Ca, and CAMK4 genes significantly decreased the level of target gene expression and cell survival, demonstrating successful intracellular siRNA delivery in HEK-293 cells. Additionally, biocompatibility testing confirmed the biological safety of the Sr-CA nanocarrier in mice. These findings suggest that Sr-CA nanocarriers are a promising siRNA delivery system, combining high efficiency with pH-sensitive release and excellent biocompatibility, making them a viable option for future therapeutic applications.

Purpose: To evaluate the effectiveness of CO 3 Ap granules in the mandibular bone defects by using computed tomography (CT) images., Methods: This study was retrospective case series of mandibular bone defect reconstruction using CO 3 Ap granules. Six patients with jawbone cysts treated by simultaneous grafting CO 3 Ap granules after cyst enucleation were enrolled. Patients without grafting CO 3 Ap granules were excluded. Mandibular bone height including buccolingual bone height, the change of perpendicular distance between the buccolingual line to the alveolar ridge, and the three-dimensional volume of remaining CO 3 Ap granules were analyzed using CT images obtained at 3, 6, 12, 18, and 24 months postoperatively., Results: Postoperative CT images showed that cortical and cancellous bone-like structures were formed on the grafting area periphery and inside the defect, respectively, with gradual resorption of the CO 3 Ap granules. Furthermore, there was no evidence of leaving bone defect even at the center of the lesion when the defect was successfully reconstructed by filling it with CO 3 Ap granules. The percentage volume of remaining CO 3 Ap granules to the volume at 3 months postoperatively were 76.1 ± 13.1%, 35.8 ± 22.5%, 25.0 ± 13.0%, and 9.9 ± 6.4% at 6, 12, 18, and 24 months postoperatively, and the volume reduction rate increased significantly within 12 months postoperatively., Conclusion: Grafting CO 3 Ap granules after the enucleation of a jawbone cyst is a good reconstructive treatment option for postoperative prosthetic treatment because CO 3 Ap granules are gradually replaced by new bone while preserving the contour of the mandibular bone., Clinical Trial Number: Not applicable., Competing Interests: Declarations. Ethics approval: The study was conducted following the Declaration of Helsinki. The Tokushima University Human Investigations Committee approved this study (approval no. 4339). Consent to participate: Informed consent was obtained in the form of opt-out on the website. Those who rejected were excluded. Consent to publish: Informed consent for publication was obtained in the form of opt-out on the website. Those who rejected were excluded. Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Aims: This preclinical study aimed to evaluate the periodontal tissue regenerative capacities of poly (lactic acid/caprolactone) (PLCL) bilayer membrane in one-wall intrabony defects in dogs. No study has assessed the efficacy of PLCL bilayer membrane for periodontal regeneration therapy despite the fact that PLCL bilayer membrane has proved efficient for bone regeneration., Methods: In five beagle dogs, the bilateral mandibular second and fourth premolars were extracted 8 weeks before the experimental surgery. Standardized bone defects (5 mm in height and 6 mm in width) were surgically created on the mesial and distal roots of the bilateral third premolars in the mandible. The test groups were set up as follows: (i) carbonate apatite (CO 3 Ap) + PLCL, (ii) CO 3 Ap, (iii) xenograft (DBBM) + collagen membrane (CM), and (iv) DBBM. The control group was left empty. Radiological, histologic and histomorphometric characteristics were compared 8 weeks after surgery., Results: No infectious complications were detected at any of the tested sites. The test groups exhibited a greater height and volume of the newly formed bone than the control group. They also showed a greater height of the newly formed cementum than the control group. However, the results were not statistically significant. The newly formed periodontal ligaments were inserted into newly formed bone and cementum in the test groups., Conclusion: The combined use of PLCL bilayer membrane and CO 3 Ap demonstrated comparable performance for periodontal tissue regeneration in one-wall intrabony defects compared to conventional therapies., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Bone graft granules are valuable tools for ridge area bone grafting owing to their ease of manipulation and interconnected porous structure. Guided bone regeneration (GBR) using barrier membranes is commonly used for alveolar ridge augmentation; however, the surgical procedures are technically complicated. In this study, we fabricated bioresorbable mesh domes (BMDs) using two types of Vicryl mesh (woven and knitted types) containing carbonate apatite granules. BMD samples were prepared in three groups: upper sides made from the woven type (UW) and lower sides made from the woven type (LW) (the UW/LW group), upper sides made from the woven type (UW) and lower sides made from the knitted type (LK) (the UW/LK group), and upper sides made from the knitted type (UK) and lower sides made from the knitted type (LK) (the UK/LK group). The samples were subsequently implanted into rabbit calvaria, and radiomorphometric and histological analyses were conducted. The UK/LK group exhibited enhanced appositional bone formation because the knitted mesh on the skin side prevented the infiltration of a substantial amount of fibrous tissue. This increase in bone formation could be attributed to the interaction between granules and osteoprogenitors that pass through the mesh from the host bone. Conversely, the UW/LW and UW/LK groups presented limited appositional bone formation. Compared with knitted mesh, woven mesh might tend to be absorbed over a short span, allowing fibrous tissue invasion and inhibiting new bone formation. Additionally, BMDs could retain granules in a targeted location and avoid displacement of the granules to unintended locations., (© 2024. The Author(s).)

Rapid bone regeneration is crucial for restoring alveolar bone and oral functions following periodontal diseases. However, the development of effective biomedical materials for this purpose remains insufficient. While bone autografts can enhance bone regeneration, they are invasive to healthy areas. Specifically, for alveolar bone regeneration, the implanted material must possess adequate mechanical strength. Moreover, local administration is preferred for older adults, who are a primary target population, to maintain their quality of life. We developed a silica-substituted carbonate apatite (CO 3 Ap-silica) block as newly bone substitute with a bone growth factor, featuring the major inorganic component of mature bone to enhance bone regeneration. CO 3 Ap-silica block stimulated the bone remodeling process at the implantation site and demonstrated significantly better bone regeneration compared to currently used carbonate apatite substitutes. Therefore, this new material is expected to advance technologies for restoring occlusal function after periodontal disease., Competing Interests: Authors declare no financial interest and no conflict of interest., (© 2024 The Author(s).)

Introduction: For deep intrabony defects or Class II furcation involvements (FI), periodontal tissue regenerative therapy combined with bone graft materials and a barrier membrane is recommended. The objective of this study was to assess the safety and efficacy of using carbonate apatite (CO 3 Ap) granules and absorbable poly(lactic acid/caprolactone) (PLCL) membranes for periodontal regeneration in the treatment of intrabony defects and mandibular Class II FI., Methods: This prospective pilot clinical study, conducted at a single center with a single-arm design, aimed to assess the safety and efficacy of CO 3 Ap and PLCL membranes in patients with periodontitis. A total of 9 patients with 10 teeth, including seven deep intrabony defects and three Class II FI, were treated with CO 3 Ap granules and PLCL membranes. Clinical parameters such as probing pocket depth (PPD), clinical attachment level (CAL), bleeding on probing (BOP), tooth mobility (Mo), Plaque Index (PI), and Gingival Index (GI) were assessed at baseline, 6 and 12 months post-surgery. Radiographic analysis was performed using dental X-rays and cone beam computed tomography (CBCT) images taken at baseline, 6, and 12 months post-surgery., Results: Postoperative healing was uneventful in most of the cases. In some cases, membrane exposures were observed. However, there were no signs of inflammation, such as abnormal bleeding, pain, swelling, or pus. These exposures eventually healed well in the end. The mean reductions in PPD at 6 and 12 months were 4.5 ± 1.6 mm and 4.9 ± 1.4 mm, respectively, while the mean gains in CAL were 4.4 ± 1.7 mm at 6 months and 4.6 ± 1.2 mm at 12 months. Radiographic analysis showed improvements in linear bone height within intrabony defects and in the vertical subclassification of FI in Class II FI., Conclusions: Despite the limitations of this study, periodontal regenerative therapy using CO 3 Ap granules and a PLCL membrane demonstrated promising clinical safety and efficacy for treating intrabony defects and mandibular Class II furcation involvement., Competing Interests: This study received funding from GC Corporation (Tokyo, Japan). The funder had an involvement with the study design, interepretation of data., (© 2024 The Author(s).)

Introduction: Dysregulated calcium homeostasis and consequentially aberrant Ca 2+ signalling could enhance survival, proliferation and metastasis in various cancers. Despite rapid development in exploring the ion channel functions in relation to cancer, most of the mechanisms accounting for the impact of ion channel modulators have yet to be fully clarified. Although harnessing small interfering RNA (siRNA) to specifically silence gene expression has the potential to be a pivotal approach, its success in therapeutic intervention is dependent on an efficient delivery system. Nanoparticles have the capacity to strongly bind siRNAs. They remain in the circulation and eventually deliver the siRNA payload to the target organ. Afterward, they interact with the cell surface and enter the cell via endocytosis. Finally, they help escape the endo-lysosomal degradation system prior to unload the siRNAs into cytosol. Carbonate apatite (CA) nanocrystals primarily is composed of Ca 2+ , carbonate and phosphate. CA possesses both anion and cation binding domains to target negatively charged siRNA molecules., Methods: Hybrid CA was synthesized by complexing CA NPs with a hydrophilic polysaccharide - hyaluronic acid (HA). The average diameter of the composite particles was determined using Zetasizer and FE-SEM and their zeta potential values were also measured., Results and Discussion: The stronger binding affinity and cellular uptake of a fluorescent siRNA were observed for HA-CA NPs as compared to plain CA NPs. Hybrid CA was electrostatically bound individually and combined with three different siRNAs to silence expression of calcium ion channel and transporter genes, TRPC6 , TRPM8 and SLC41A1 in a human breast cancer cell line (MCF-7) and evaluate their potential for treating breast cancer. Hybrid NPs carrying TRPC6 , TRPM8 and SLC41A1 siRNAs could significantly enhance cytotoxicity both in vitro and in vivo. The resultant composite CA influenced biodistribution of the delivered siRNA, facilitating reduced off target distribution and enhanced breast tumor targetability., Competing Interests: Ezharul Hoque Chowdhury is affiliated with Nanoflex LLC. The authors report no conflicts of interest in this work., (© 2024 Uddin et al.)

Both the composition and architecture of artificial bone govern bone regeneration. Herein, carbonate apatite (CAp), which has a similar mineral composition to bone, was prepared by immersing calcium carbonate (CaCO 3 ) in a phosphate solution with varying acidification levels (pH 6.0) to pH 8.9, to reveal the influence of pH on the composition and architecture of the resultant CAp granules. The composition, crystal morphology, and architecture of resultant CAp granules was well-characterized by X-ray diffraction, scanning electron microscopy, mercury intrusion porosimetry and so on. Consequently, the rate of compositional transformation from CaCO 3 to CAp was much higher at pH 6.0 and pH 7.0 than pH 8.0 and pH 8.9. The pH of the phosphate solution did not affect the macroarchitecture of the resultant CAp granules. In contrast, the composition, crystal morphology, microarchitecture, and degradation behavior of the resultant CAp granules were affected by pH of the phosphate solution. In particular, the open-pore distributions and volumes of the CAp granules prepared at pH 6.0-8.9 were changed to reflect the microarchitecture of the samples. Therefore, this study revealed that the pH-controlled elution precipitation reaction is useful for controlling the composition, crystal morphology, microarchitecture, and degradation behavior of the resultant CAp, while preserving its macroarchitecture. Our findings provide fundamental insights into the design of artificial bones for bone regeneration., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wang, Shimabukuro, Kishida, Yokoi and Kawashita.)

The newly developed mineral carbonated apatite has recently been proposed as a bone graft material for bone regenerative treatment in implant therapy. This case series details the clinical and radiographic outcomes of ridge preservation and ridge augmentation using only carbonated apatite as bone graft material for implant treatment. Twenty patients (36 sites) who required bone regeneration and implant placement were retrospectively assessed. Simultaneous carbonated apatite implant placement was performed using the simultaneous ridge preservation or augmentation approach on 24 sites in 13 patients with sufficient bone quantity for primary stabilization based on preoperative evaluation results. A staged ridge preservation or augmentation approach was used for the remaining 12 sites in seven patients with insufficient bone quantity. The mean regenerated bone height for each treatment method was as follows: simultaneous preservation, 7.4 ± 3.3 mm; simultaneous augmentation, 3.6 ± 2.3 mm; staged preservation, 7.2 ± 4.5 mm; and staged augmentation, 6.1 ± 2.7 mm. The mean regenerated bone width for each treatment method was as follows: simultaneous preservation, 6.5 ± 2.9 mm; simultaneous augmentation, 3.3 ± 2.5 mm; staged preservation, 5.5 ± 1.7 mm; and staged augmentation, 3.5 ± 1.9 mm. Ultimately, the use of carbonated apatite alone as a bone graft material in implant therapy resulted in stable and favorable bone regeneration.

Bone defects represent an everyday challenge for clinicians who work in the fields of orthopedic surgery, maxillofacial and oral surgery, otorhinolaryngology, and dental implantology. Various bone substitutes have been developed and utilized, according to the needs of bone reconstructive surgery. Carbonate apatite has gained popularity in recent years, due to its excellent tissue behavior and osteoconductive potential. This systematic review aims to evaluate the role of carbonate apatite in bone reconstructive surgery and tissue engineering, analyze its advantages and limitations, and suggest further directions for research and development. The Web of Science, PubMed, and Scopus electronic databases were searched for relevant review articles, published from January 2014 to 21 July 2023. The study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Eighteen studies were included in the present review. The biological properties and medical applications of carbonate apatite (CO 3 Ap) are discussed and evaluated. The majority of articles demonstrated that CO 3 Ap has excellent biocompatibility, resorbability, and osteoconductivity. Furthermore, it resembles bone tissue and causes minimal immunological reactions. Therefore, it may be successfully utilized in various medical applications, such as bone substitution, scaffolding, implant coating, drug delivery, and tissue engineering.

Purpose: Maxillary molars have low alveolar bone height diameter due to the presence of the maxillary sinus; thus, a sinus lift may be required in some cases. Changes in the volume of bone substitutes can affect the success of implant therapy. Therefore, this study aimed to compare the changes in the volume of two different bone substitutes-one based on carbonate apatite and the other on octacalcium phosphate-used in maxillary sinus floor elevation., Methods: Nineteen patients and 20 sites requiring maxillary sinus floor elevation were included in the study. Digital Imaging and Communications in Medicine data for each patient obtained preoperatively and immediately and 6 months postoperatively were used to measure the volume of the bone grafting material using a three-dimensional image analysis software. The immediate postoperative volume of octacalcium phosphate was 95.3775 mm 3 per piece of grafting material used. It was multiplied by the number of pieces used and converted to mL to determine the immediate postoperative volume., Results: The mean resorption values of carbonate apatite and octacalcium phosphate were 12.7 ± 3.6% and 17.3 ± 3.9%, respectively. A significant difference in the amount of resorption of the two bone replacement materials was observed (P = 0.04)., Conclusions: The results of this study indicate that both bone substitute materials tend to resorb. The two bone grafting materials that are currently medically approved in Japan have not been in the market for a long time, and their long-term prognosis has not yet been reported. Further clinical data are warranted., (© 2024. The Author(s).)

Purpose: After tooth extraction, preservation of the alveolar ridge by socket grafting attenuates bone resorption. Runt-related transcription factor 2 (RUNX2) and SP7/Osterix (OSX) are transcription factors playing an important role in osteoblast differentiation. The purpose of this study was to evaluate the effects of carbonate apatite (CO 3 Ap) on osteoblast-related gene and protein expression after socket grafting., Methods: Alveolar bone and new bone after CO 3 Ap grafting were collected at the time of implant placement. Levels of mRNA for RUNX2, SP7/OSX, bone morphogenetic protein 2 (BMP2), BMP7 and platelet derived growth factor B were determined by real-time PCR. Immunostaining was performed using antibodies against RUNX2, SP7/OSX, vimentin and cytokeratin. To evaluate bone resorption rates, cone-beam CT (CBCT) imaging was performed after socket grafting and before implant placement., Results: CBCT imaging showed that the average degree of bone resorption at the CO 3 Ap graft site was 7.15 ± 3.79%. At the graft sites, levels of SP7/OSX and BMP2 mRNA were significantly increased. Replacement of CO 3 Ap with osteoid was evident histologically, and in the osteoid osteoblast-like cells were stained for SP7/OSX and vimentin., Conclusion: These results show that gene expression of both SP7/OSX and BMP2 can be induced by CO 3 Ap, suggesting that increased expression of SP7/OSX and vimentin may be involved in the BMP pathway.

Proper analysis of urinary stone composition is a cornerstone for diagnosis, targeted treatment and recurrence prevention of urolithiasis. The aim of this study was to determine the composition, frequency and distribution of mixed stones according to gender and age of patients. A total of 42,519 urinary stones from 30,311 men and 12,208 women submitted between January 2007 and December 2020 were studied. Most urinary calculi consisted of two components (50.9%), followed by stones of a single constituent (27.1%) and three-component stones (21.9%), while four-component stones were only rarely identified (0.1%). Among all stones, 49.8% consisted of whewellite (COM), weddellite (COD), and mixtures of COM and COD, 33.8% were pure carbonate apatite (CA) and mixtures of CA with COM and/or COD, while 7.6% were composed of uric acid anhydrous (UAA), uric acid dihydrate (UAD), and mixed UAA and UAD. The remaining 8.8% of calculi were rare single-component stones and rare mixtures of various constituents. The number of stone components was inversely associated with age (p < 0.001). The proportion of men decreased significantly with the number of stone constituents, from 3.01:1 for single-component stones to 1.0:1 for four-component urinary calculi (p < 0.001). The vast majority of urinary calculi consisted of two or more components in varying proportions. While age was inversely associated with the number of stone constituents, the proportion of women increased significantly from single-component to four-component urinary calculi. A significant proportion of mixed stones could present a challenge for diagnosis and targeted recurrence prevention., (© 2024. The Author(s).)

Scaffolds having appropriate mechanical strength and providing a proper microenvironment for osteogenesis are expected to be effective alternatives to autografts for bone regeneration. In this study, ant-nest type porous (ANP) scaffolds consisting of CO 3 Ap were fabricated using calcium carbonate powder or slurry and two types of polyurethane foam through a dissolution-precipitation reaction. ANP-type, three-dimensional, interconnected porous CO 3 Ap scaffolds were fabricated by burning out the struts of polyurethane foams embedded in CaCO 3 , followed by compositional transformation from CaCO 3 to CO 3 Ap. The types of polyurethane foam and impregnation methods of CaCO 3 into polyurethane form affected the geometry of the resulting ANP structures. Mechanical and in vivo biological performances of these scaffolds relied on the geometry of the ANP structures. The ANP structures displayed had a clear structural advantage in bone regeneration, owing to the promotion of cell and tissue migration throughout the scaffolds. In particular, ANP-structured scaffolds, which had highest porosity, interconnectivity, and smallest strut thickness, had a mechanical strength comparable to cancellous bone, formed more new bone, were highly resorbed, resulting in cancellous bone-like bone tissue regeneration at 12 weeks of healing. The results suggest that bone regeneration after the migration of cell and tissue into the entire scaffolds is affected by strut thickness preferentially over porosity and interconnectivity. ANP-structured CO 3 Ap scaffolds are attractive for bone regeneration., (© 2023 Wiley Periodicals LLC.)

Introduction: This study was designed to determine the mineral composition of calculi in nephrocalcinosis with nephrolithiasis, diagnose the underlying disease, and monitor the course of renal function in patients with nephrocalcinosis-nephrolithiasis., Methods: Renal calculi extruded in a series of 8 patients with nephrocalcinosis were analysed using Fourier transmission infrared spectrometry. In 4 patients, next-generation sequencing using a nephrocalcinosis-nephrolithiasis panel was performed to determine the nature of the underlying disease. In addition, longitudinal analysis of renal function was performed in all patients., Results: Seven patients revealed carbonate apatite as the sole constituent of renal calculi. One patient showed a mixed composition of dicalcium phosphate dihydrate/carbonate apatite at first analysis yet in subsequent episodes also had calculi composed of pure carbonate apatite. Further molecular analysis displayed distal renal tubular acidosis in 2 of 4 patients who consented to sequencing. No known genetic defect could be found in the other two cases. In line with prior reports, decline of renal function was dependent on underlying disease. Distal renal tubular acidosis revealed a progressive course of renal failure, whereas other causes showed stable renal function in long term analysis., Conclusion: Nephrocalcinosis with nephrolithiasis is a rare condition with heterogeneous aetiology. Yet mineral composition of renal calculi predominantly consisted of pure carbonate apatite. This uniform finding is similar to subcutaneous calcifications of various origins and might propose a general principle of tissue calcification. Progressive decline of renal function was found in distal renal tubular acidosis, whereas other conditions remained stable over time., (© 2024 The Author(s). Published by S. Karger AG, Basel.)

Autologous bone grafting is the primary method for treating alveolar clefts. However, bone grafting materials are desired as alternatives to autogenous bone to reduce surgical invasiveness. Here, we present an animal study evaluating the effect of carbonate apatite (CA) on the spontaneous eruption of permanent teeth. The bone grafting materials included CA, natural bovine bone (BB), and hydroxyapatite (HA). In 15 8-week-old male beagle dogs, the left mandibular deciduous premolars (DP) two and three were extracted and subsequently filled with CA, BB, and HA. The animals were euthanized after a predetermined number of days, and samples were collected for microcomputed tomography and histological evaluation. Spontaneous eruption of the succeeding permanent teeth (P3 and P4) was observed in the CA group at 14 weeks. Delayed eruption of the succeeding permanent teeth was observed in the BB and HA groups. CA could serve as a viable alternative to autogenous bone for treating alveolar clefts.

This study radiologically and histologically compared two bioresorbable bone substitutes with different compositions carbonate apatite (Cytrans ® Granules; CGs) and β-tricalcium phosphate (β-TCP) for vertical bone augmentation on a rat skull using a polytetrafluoroethylene (PTFE) tubes. This PTFE tube was placed at the center of the skull, fixed with Super Bond, and augmented with CGs or β-TCP granules. Specimens with surrounding tissue were harvested at 4, 8, and 12 weeks postoperatively, and radiological and histological evaluations were performed. The bone volume to total volume ratio (BV/TV) of the β-TCP-implanted group was markedly higher than that of the CG-implanted group at 4 and 12 weeks postoperatively. Compared to CGs, β-TCP exhibited the ability to form blood vessels into the graft material for a short period after transplantation, as well as an elevated production of collagen into β-TCP granules during the bone formation process.

Maxillary sinus augmentation with a lateral approach (MSA) is a well-established treatment. In this prospective study, we evaluated risk factors for postoperative bone graft displacement and reported the clinical application of long-term resorbable L-lactic acid/-caprolactone (PLA/PCL) as a barrier membrane to cover the open window in the lateral wall in MSA. Twenty-four patients underwent MSA according to the relevant criteria; CT data obtained before and 1 week (1 w) and 5-6 months (5 m) post-MSA, bone height changes, bone height reduction rates at 1 w and 5 m post-MSA, bone graft displacement measurements, and risk factors were examined. All patients showed bone height increments ( p < 0.005). However, no difference was observed between 1 w and 5 m post-MSA. Bone graft displacement was observed in eight patients; the reduction rate from 1 w to 5 m post-MSA was 8.38% ± 4.88%. Sex, septa, maxillary sinus floor-palatal bone distance, and maxillary sinus floor-maxillary ostium distance were associated with bone graft displacement ( p < 0.05). The height from the maxillary sinus floor to the palatal bone and the sinus angle influenced the augmentation degree ( p < 0.05). The PLA/PCL membrane is compared favorably with other membranes and may be useful as a barrier membrane for the MSA open window.

Biodegradable guided bone regeneration (GBR) membranes consist primarily of collagen and aliphatic polyesters. This study assessed the comparative efficacy of a poly(l-lactic-caprolactone) [P(LA/CL)] membrane versus that of a collagen membrane in GBR. Patients requiring GBR simultaneously or before dental implant placement in edentulous regions were randomly assigned to one of two membranes. Within each membrane, they were subdivided into 3 groups: dental implants were placed simultaneously with GBR in groups A and B, and 180 days post-GBR in group C. The augmented bone width was measured at 1, 3, and 6 mm from the implant's neck (groups A and B) or the reference line (group C), utilizing cone-beam computed tomography images, immediately and 150 days post-surgery. A histological study was performed to evaluate bone formation in group C. No adverse events were observed. In the collagen group, the absorbed ratios of the augmented bone were 40.9 ± 36.7%, 29.4 ± 30.1%, and 11.1 ± 22.0% at 1, 3, and 6 mm, respectively; the ratio at 6 mm was significantly lower than that at 1 mm ( p = 0.0442). In the P(LA/CL) group, those were 26.2 ± 27.3%, 17.1 ± 19.7%, and 13.3 ± 16.4% at 1, 3, and 6 mm, respectively, with no significant difference at each point. No significant inter-membrane differences were observed. The bone augmentation potential of the P(LA/CL) membrane matched that of the collagen membrane. P(LA/CL) could be used as a safe and effective membrane in GBR.

Carbonate apatite (CO 3 Ap) is a major inorganic bone component and an effective bone substitute. To clarify the function of CO 3 Ap, we compared differences among CO 3 Ap, hydroxyapatite (HAp), and β-tricalcium phosphate (β-TCP) by focusing on mesenchymal stem cells (MSCs) that have a role in wound healing. For in vivo experiments, maxillary molars were removed and the bone substitute was inserted. MSC accumulation around extraction sockets was significantly promoted in CO 3 Ap and β-TCP groups. For in vitro experiments, MSCs were cultured with bone substitutes. The differentiation potential and amount of calcium deposition were significantly lower in CO 3 Ap and HAp groups than in the β-TCP group. Increases in insulin-like growth factor-I and vascular endothelial growth factor were found only in the CO 3 Ap group. CO 3 Ap-filled extraction sockets accumulated MSCs, and MSCs cultured in the presence of CO 3 Ap produced large amounts of growth factors. These results suggest that CO 3 Ap promotes healing of tooth extraction sockets.

Carbonate apatite (CO 3 Ap) is a bioceramic material with excellent properties for bone and dentin regeneration. To enhance its mechanical strength and bioactivity, silica calcium phosphate composites (Si-CaP) and calcium hydroxide (Ca(OH) 2 ) were added to CO 3 Ap cement. The aim of this study was to investigate the effect of Si-CaP and Ca(OH) 2 on the mechanical properties in terms of the compressive strength and biological characteristics of CO 3 Ap cement, specifically the formation of an apatite layer and the exchange of Ca, P, and Si elements. Five groups were prepared by mixing CO 3 Ap powder consisting of dicalcium phosphate anhydrous and vaterite powder added by varying ratios of Si-CaP and Ca(OH) 2 and 0.2 mol/L Na 2 HPO 4 as a liquid. All groups underwent compressive strength testing, and the group with the highest strength was evaluated for bioactivity by soaking it in simulated body fluid (SBF) for one, seven, 14, and 21 days. The group that added 3% Si-CaP and 7% Ca(OH) 2 had the highest compressive strength among the groups. SEM analysis revealed the formation of needle-like apatite crystals from the first day of SBF soaking, and EDS analysis indicated an increase in Ca, P, and Si elements. XRD and FTIR analyses confirmed the presence of apatite. This combination of additives improved the compressive strength and showed the good bioactivity performance of CO 3 Ap cement, making it a potential biomaterial for bone and dental engineering applications.

The composition of carbonate apatite (CO 3 Ap) aids bone regeneration. Other features, such as porosity and pore interconnectivity of artificial bone, also govern bone regeneration. In general, a trade-off exists between the porosity and mechanical strength of artificial bone. Therefore, this suggests that the interconnected pores in the ant-nest-type porous (ANP) structure of artificial bone accelerate bone regeneration by minimizing the sacrifice of mechanical strength. The unique structure of polyurethane foam has the potential to endow CO 3 Ap with an ANP structure without forming excess pores. This study investigated the efficacy of polyurethane foam as a porogen in providing ANP structure to CO 3 Ap artificial bone. The polyurethane foam was completely decomposed by sintering and the resulting CO 3 Ap displayed ANP structure with a compressive strength of approximately 15 MPa. Furthermore, in vivo experiments revealed that the migration of cells and tissues into the interior of CO 3 Ap through the interconnected pores accelerated bone regeneration in the ANP-structured CO 3 Ap. Thus, this indicates that using polyurethane foam as a porogen endows the CO 3 Ap artificial bone with an ANP structure that accelerates bone regeneration., (© 2022 Wiley Periodicals LLC.)

Objective: This study aimed to histologically compare periodontal regeneration of one-wall intrabony defects treated with open flap debridement, β-tricalcium phosphate (β-TCP), and carbonate apatite (CO 3 Ap) in dogs., Methods: The mandibular third premolars of four beagle dogs were extracted. Twelve weeks after the extraction, a one-wall bone defect of 4 mm × 5 mm (mesio-distal width × depth) was created on the distal side of the mandibular second premolar and mesial side of the fourth premolar. Each defect was randomly allocated to open flap debridement (control group), periodontal regeneration utilizing β-TCP, or CO 3 Ap. Eight weeks after the surgery, histologic and histometric analyses were performed., Results: No ankylosis, infection, or acute inflammation was observed at any of the experimental sites. Newly formed bone and cementum were observed in all experimental groups. The mineral apposition rate of the alveolar bone crest was higher in the CO 3 Ap group than in the control and β-TCP groups. The ratio of the new bone area was significantly higher in the CO 3 Ap group than in the control group ( P  < 0.05). The bone contact percentage of the residual granules was significantly higher in the CO 3 Ap group than in the β-TCP group ( P  < 0.05)., Conclusion: Although this study has limitations, the findings revealed the safety and efficacy of CO 3 Ap for periodontal regeneration in one-wall intrabony defects in dogs, and CO 3 Ap has a better ability to integrate with bone than β-TCP., Competing Interests: This study received funding from GC Corporation (Tokyo, Japan). The funder had the following involvement with the study design, interpretation of data. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 The Japanese Society for Regenerative Medicine. Production and hosting by Elsevier B.V.)

We have developed an autologous transplantation method using adipose tissue-derived multi-lineage progenitor cells (ADMPCs) as a method of periodontal tissue regeneration that can be adapted to severe periodontal disease. Our previous clinical study confirmed the safety of autologous transplantation of ADMPCs and demonstrated its usefulness in the treatment of severe periodontal disease. However, in the same clinical study, we found that the fibrin gel used as the scaffold material might have caused gingival recession and impaired tissue regeneration in some patients. Carbonate apatite has a high space-making capacity and has been approved in Japan for periodontal tissue regeneration. In this study, we selected carbonate apatite as a candidate scaffold material for ADMPCs and conducted an in vitro examination of its effect on the cellular function of ADMPCs. We further performed autologous ADMPC transplantation with carbonate apatite as the scaffold material in a model of one-wall bone defects in beagles and then analyzed the effect on periodontal tissue regeneration. The findings showed that carbonate apatite did not affect the cell morphology of ADMPCs and that it promoted proliferation. Moreover, no effect on secretor factor transcription was found. The results of the in vivo analysis confirmed the space-making capacity of carbonate apatite, and the acquisition of significant new attachment was observed in the group involving ADMPC transplantation with carbonate apatite compared with the group involving carbonate apatite application alone. Our results demonstrate the usefulness of carbonate apatite as a scaffold material for ADMPC transplantation.

Carbonate apatite (CO 3 Ap) granules are useful as a bone substitute because they can be remodeled to new natural bone in a manner that conforms to the bone remodeling process. However, reconstructing large bone defects using CO 3 Ap granules is difficult because of their granular shape. Therefore, we fabricated CO 3 Ap honeycomb blocks (HCBs) with continuous unidirectional pores. We aimed to elucidate the tissue response and availability of CO 3 Ap HCBs in the reconstruction of rabbit mandibular bone defects after marginal mandibulectomy. The percentages of the remaining CO 3 Ap area and calcified bone area (newly formed bone) were estimated from the histological images. CO 3 Ap area was 49.1 ± 4.9%, 30.3 ± 3.5%, and 25.5 ± 8.8%, whereas newly formed bone area was 3.0 ± 0.6%, 24.3 ± 3.3%, and 34.7 ± 4.8% at 4, 8, and 12 weeks, respectively, after implantation. Thus, CO 3 Ap HCBs were gradually resorbed and replaced by new bone. The newly formed bone penetrated most of the pores in the CO 3 Ap HCBs at 12 weeks after implantation. By contrast, the granulation tissue scarcely invaded the CO 3 Ap HCBs. Some osteoclasts invaded the wall of CO 3 Ap HCBs, making resorption pits. Furthermore, many osteoblasts were found on the newly formed bone, indicating ongoing bone remodeling. Blood vessels were also formed inside most of the pores in the CO 3 Ap HCBs. These findings suggest that CO 3 Ap HCBs have good osteoconductivity and can be used for the reconstruction of large mandibular bone defects. The CO 3 Ap HCB were gradually resorbed and replaced by newly formed bone., (© 2022. The Author(s).)

Bone augmentation using artificial bone is an important option in dental defect prostheses. A bone substitute using carbonate apatite (CO 3 Ap), an inorganic component of bone, was reported to have promising bone formation and bone replacement ability. However, the osteoinductivity of artificial bone is less than autogenous bone (AB). In this study, CO 3 Ap with AB is demonstrated as a clinically effective bone substitute. For in vitro experiments, an osteoclast-like cell (RAW-D) was cultured in the presence of AB, CO 3 Ap, or both (Mix), and the number of osteoclasts was evaluated. Osteoblasts were also cultured under the same conditions, and the number of adherent cells was evaluated. For in vivo experiments, a few holes were created in the rat tibia and AB, CO 3 Ap, or Mix were added. At 0, 14, and 21 days, the tissue morphology of the wound area was observed, and the thickness of the cortical bone was measured. In vitro, Mix did not increase the number of osteoclasts or osteoblasts. However, in vivo, the rate of bone replacement remarkably increased with Mix on dome-shape. A bone-grafting material combining osteoinductive AB with abundant artificial bone is expected to be clinically easy to use and able to form bone.

The present study investigated the osteoclast differentiation potential and paracrine effects of osteoclasts on osteoblast differentiation when the cells were cultured directly on two bone substitutes (BSs): deproteinized bovine bone mineral (DBBM) and carbonate apatite (CO 3 Ap). Human primary osteoclasts cultured on the BSs were assessed by tartrate-resistant acid phosphatase (TRAP) and actin ring staining. Thereafter, the mRNA levels of osteoclastic differentiation markers were quantified by real-time PCR. Osteoblast behaviors in response to conditioned media collected from osteoclast cultures were investigated. Interestingly, mature osteoclasts were occasionally observed on the surface of the CO 3 Ap granules, whereas very few and small osteoclasts were observed on DBBM. Similarly, real-time PCR analysis showed higher mRNA levels of osteoclast markers, including cathepsin K and TRAP, in the cells cultured on CO 3 Ap than in those cultured on DBBM. Furthermore, compared to DBBM, CO 3 Ap promoted osteoblast differentiation in human primary osteoblasts, whereas few paracrine effects of osteoclasts cultured with either BS were observed on the osteoblast differentiation potential. These limited results showed that CO 3 Ap provided a favorable surface for osteoclast differentiation, as well as osteoblasts, compared to DBBM in vitro., (© 2022 Wiley Periodicals LLC.)

The objective of this study was to clarify the efficiency of a combination of stem cells from human deciduous teeth and carbonate apatite in bone regeneration of calvarial defects. Immunodeficient mice ( n = 5 for each group/4 groups) with artificial calvarial bone defects (5 mm in diameter) were developed, and stem cells from human deciduous teeth (SHEDs) and carbonate hydroxyapatite (CAP) granules were transplanted with an atelocollagen sponge as a scaffold. A 3D analysis using microcomputed tomography, and 12 weeks after transplantation, histological and immunohistochemical evaluations of markers of bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF), and cluster of differentiation (CD) 31 were performed. In the 3D analysis, regenerated bone formation was observed in SHEDs and CAP, with the combination of SHEDs and CAP showing significantly greater bone regeneration than that in the other groups. Histological and immunohistochemical evaluations showed that combining SHEDs and CAP enhanced the expression of BMP-2, VEGF, and CD31, and promoted bone regeneration. This study demonstrates that the combination of SHEDs and CAP transplantation may be a promising tool for bone regeneration in alveolar defects.

The porous architecture of artificial bones plays a pivotal role in bone ingrowth. Although salt leaching methods produce predictable porous architectures, their application in the low-temperature fabrication of ceramics remains a challenge. Carbonate apatite (CO 3 Ap) blocks with three ranges of pore sizes: 100-200, 200-400, and 400-600 μm, were fabricated from CaCO 3 blocks with embedded Na 2 HPO 4 crystals as a porogen and accelerator for CaCO 3 -to-CO 3 Ap conversion. CaCO 3 blocks were obtained from Ca(OH) 2 compacts with Na 2 HPO 4 by CO 2 flow at 100% humidity. When carbonated under 100% water humidity, the dissolution of Na 2 HPO 4 and the formation of hydroxyapatite were observed. Using 90% methanol and 10% water were beneficial in avoiding the Na 2 HPO 4 consumption and generating the metastable CaCO 3 vaterite, which was rapidly converted into CO 3 Ap in a Na 2 HPO 4 solution in 7 days. For the histological evaluation, the CO 3 Ap blocks were implanted in rabbit femur defects. Four weeks after implantation, new bone was formed at the edges of the blocks. After 12 weeks, new bone was observed in the central areas of the material. Notably, CO 3 Ap blocks with pore sizes of 100-200 μm were the most effective, exhibiting approximately 23% new bone area. This study sheds new light on the fabrication of tailored porous blocks and provides a useful guide for designing artificial bones., (© 2022 Wiley Periodicals LLC.)

Introduction and Objectives: Infection-associated renal stones are commonly composed of magnesium-ammonium-phosphate (MAP) and carbonate apatite (CA). The clinical implications of these two different, but closely related stone types, are unknown. We sought to compare the clinical, microbiologic, and metabolic characteristics of patients with MAP and CA stone types. Methods: We retrospectively reviewed the medical records of patients from two centers (one in the United States and one in Israel) who underwent ureteroscopy or percutaneous nephrolithotomy between 2012 and 2020 and identified patients with a predominant stone analysis component of CA or MAP and clinical data supporting an infection stone. We analyzed and compared demographic data, medical history, postoperative fever, stone and urinary microbiology, and 24-hour urine studies. Results: A total of 79 and 75 patients met the inclusion criteria for the MAP and CA cohorts, respectively. No significant difference was found in patient demographics or comorbidities between the MAP and CA cohort. Female predominance was noted in both. Although there were no significant differences in 24-hour urine parameters between the cohorts, hypercalciuria was common in both cohorts (38% and 32% of patients in the MAP and CA cohorts, respectively). Gram-negative bacteria were more common in the MAP stone cultures. Postoperative fever was significantly more common in the MAP cohort (14.7% vs 3.8%, p  < 0.016). Conclusions: MAP and CA stone formers share similar demographic characteristics with a clear female predominance. MAP stones patients appear more likely to develop postoperative fever, possibly related to a higher occurrence of gram-negative bacteria in the stone cultures of the MAP cohort. Although there were no significant differences among metabolic parameters, hypercalciuria was noted in approximately a third of the cohort. The clinical significance of this finding is yet to be determined.

Carbonate apatite (CO 3 Ap) is an inorganic component of bone and replaces by natural bone after implantation into the bone defect. Because of this unique characteristic, CO 3 Ap granules have been used in the dental field. However, washing out of granules from the bone defect area is an issue. The aim of this study was to set CO 3 Ap granules by mixing CO 3 Ap granules with acidic phosphate solutions and evaluate the influence of the pH and ion components of the solutions. When Na + was the counter ion, the amount of precipitated dicalcium phosphate dihydrate (DCPD) was small and the setting ability disappeared with increasing pH of the solutions. Alternatively, when the counter ion was Ca 2+ , the amount of precipitated DCPD was high and the setting ability was observed even at high pH. These results suggest the presence of Ca 2+ in the acidic phosphate solution is a key for fabricating CO 3 Ap granular cement.

The reconstruction of critical-sized segmental bone defects is a key challenge in orthopedics because of its intractability despite technological advancements. To overcome this challenge, scaffolds that promote rapid bone ingrowth and subsequent bone replacement are necessary. In this study, we fabricated three types of carbonate apatite honeycomb (HC) scaffolds with uniaxial channels bridging the stumps of a host bone. These HC scaffolds possessed different channel and micropore volumes. The HC scaffolds were implanted into the defects of rabbit ulnar shafts to evaluate the effects of channels and micropores on bone reconstruction. Four weeks postoperatively, the HC scaffolds with a larger channel volume promoted bone ingrowth compared to that with a larger micropore volume. In contrast, 12 weeks postoperatively, the HC scaffolds with a larger volume of the micropores rather than the channels promoted the scaffold resorption by osteoclasts and bone formation. Thus, the channels affected bone ingrowth in the early stage, and micropores affected scaffold resorption and bone formation in the middle stage. Furthermore, 12 weeks postoperatively, the HC scaffolds with large volumes of both channels and micropores formed a significantly larger amount of new bone than that attained using HC scaffolds with either large volume of channels or micropores, thereby bridging the host bone stumps. The findings of this study provide guidance for designing the pore structure of scaffolds., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Shibahara, Hayashi, Nakashima and Ishikawa.)

Background: Low bone quantity and quality are serious problems that affect the prognosis of implants in the cosmetic field. Therefore, artificial bone substitutes are frequently used. However, whether there is a difference in the effect of either bone substitute on soft tissue healing is unclear given their greatly different absorbability. In this study, we used hydroxyapatite (HAp) and carbonate apatite (CO 3 Ap) as bone substitutes to analyze the epithelial and connective tissue healing after tooth extraction., Methods: In vitro, oral mucosa-derived epithelial cells (OECs) collected from 4-day-old Wistar rats were seeded on HAp or CO 3 Ap and evaluated for adhesion, proliferation, migration, apoptosis, and morphology. Fibroblasts (FBs) were also analyzed for their ability to express collagen. In vivo, the extraction of maxillary right first (M1) and second molars (M2) of 6-week-old male Wistar rats was performed, followed by insertion of HAp or CO 3 Ap granules into the M1 and M2 sites. The oral mucosal healing process was then evaluated histochemically after 7 and 14 days., Results: In vitro, high collagen expression by FBs in the CO 3 Ap group was observed and the surface analysis showed spreading of the FBs on the CO 3 Ap surface. However, the activity of OECs was suppressed on CO 3 Ap. Two weeks after CO 3 Ap implantation, soft tissue healing was observed, and recovery of the connective tissue was observed on the remaining CO 3 Ap., Conclusions: Our results suggest that the formation of soft tissues, including connective tissue, was promoted by CO 3 Ap in the extraction socket within a short period., (© 2022. The Author(s).)

Porous architecture in bone substitutes, notably the interconnectivity of pores, is a critical factor for bone ingrowth. However, controlling the pore interconnectivity while maintaining the microarchitecture has not yet been achieved using conventional methods, such as sintering. Herein, we fabricated a porous block using the crystal growth of calcium sulfate dihydrate, and controlled the pore interconnectivity by limiting the region of crystal growth. The calcium sulfate dihydrate blocks were transformed to bone apatite, carbonate apatite (CO 3 Ap) through dissolution-precipitation reactions. Thus, CO 3 Ap blocks with 15% and 30% interconnected pore volumes were obtained while maintaining the microarchitecture: they were designated as CO 3 Ap-15 and CO 3 Ap-30, respectively. At 4 weeks after implantation in a rabbit femur defect, new bone formed throughout CO 3 Ap-30, whereas little bone was formed in the center region of CO 3 Ap-15. At 12 weeks after implantation, a large portion of CO 3 Ap-30 was replaced with new bone and the boundary with the host bone became blurred. In contrast, CO 3 Ap-15 remained in the defect and the boundary with the host bone was still clear. Thus, the interconnected pores promote bone ingrowth, followed by replacement of the material with new bone. These findings provide a useful guide for designing bone substitutes for rapid bone regeneration., (© The Author(s) 2022. Published by Oxford University Press.)

Carbonate apatite (CO 3 Ap), an inorganic component of human bone, has been clinically applied as an artificial bone substitute. In this study, the effects of the CO 3 content in CO 3 Ap on the replacement by new bone were studied by fabricating CO 3 Ap granules containing 0.9-8.3 wt% of CO 3 . The dissolution rate of CO 3 Ap in a weak acidic solution, mimicking the Howship's lacunae, was rapid for the CO 3 Ap granules containing a larger amount of CO 3 . Histological analyses demonstrated the rapid resorption in CO 3 Ap and replacement by natural bone tissue when the CO 3 content was increased. Therefore, the CO 3 content in CO 3 Ap is a key factor that influences the replacement of the bone tissue., (© 2021 John Wiley & Sons Ltd.)

Fracture-related infections require both treatments for bacteria removal and bone reconstruction. The use of combined broad-spectrum antibacterial silver compounds and artificial bone with high osteogenic activity is considered to be an effective strategy for achieving these treatments in one surgery. However, silver compounds are toxic for living tissues even at low concentrations. Herein, we investigated the no-observed-effect level (NOEL) of silver phosphate (Ag 3 PO 4 ) in a bone substitute composed of carbonate apatite (CO 3 Ap), a bone mineral, using in vitro and in vivo experiments. In vitro experiments demonstrated that the CO 3 Ap artificial bone containing ≥0.1 wt % Ag 3 PO 4 exerted antibacterial effects against Staphylococcus epidermidis , while those containing ≤0.3 wt % Ag 3 PO 4 did not affect cellular adhesion, proliferation, differentiation, and calcification of osteoblast-like MC3T3-E1 cells. In vivo experiments demonstrated that the CO 3 Ap artificial bone containing ≤0.3 wt % Ag 3 PO 4 replaced a new bone to the same levels as those without Ag 3 PO 4 4 weeks after implantation into the bone defect of the rabbit femur condyle. However, the CO 3 Ap artificial bone containing 0.3 wt % Ag 3 PO 4 caused an inflammatory reaction, whereas those containing ≤0.1 wt % Ag 3 PO 4 did not. Thus, both bone regeneration and infection control without any adverse effects were achieved using the CO 3 Ap artificial bone containing 0.1 wt % Ag 3 PO 4 , indicating that the NOEL of Ag 3 PO 4 was 0.1 wt %. Our results provide an effective strategy for the treatments of fracture-related infections.

Hypothesis: The air-solution interface of supersaturated calcium hydrogen carbonate (Ca(HCO 3 ) 2 ) represents the highest saturation state due to evaporation/CO 2 -degassing, where calcite crystals are expected to nucleate and grow along the interface. Hence, it should be possible to form a free-standing mineral-only calcium carbonate (CaCO 3 ) microfilm at the air-solution interface of Ca(HCO 3 ) 2 . The air-solution interface of phosphate buffered saline (PBS) could represent a phase boundary to introduce a hybrid microstructure of CaCO 3 and carbonate-rich dicalcium hydroxide phosphate (carbonate-rich hydroxylapatite)., Experiments: Supersaturated Ca(HCO 3 ) 2 was prepared at high pressure and heated to form CaCO 3 microfilms, which were converted to bone-like microfilms at the air-solution interface of PBS by dissolution-recrystallisation. The microfilms were characterised by scanning electron microscopy, 3D confocal microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, laser Raman microspectroscopy, and X-ray photoelectron spectroscopy. An in situ X-ray diffraction (XRD) system that simulates the aforementioned interfacial techniques was developed to elucidate the microfilms formation mechanisms., Findings: The CaCO 3 and bone-like microfilms were free-standing, contiguous, and crystalline. The bone-like microfilms exhibited a hybrid structure consisting of a surface layer of remnant calcite and a carbonate-rich hydroxylapatite core of plates. The present work shows that the air-solution interface can be used to introduce hybrid microstructures to mineral microfilms., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Exosomes are secreted from a variety of cells and transmit parental cell-derived biomolecules, such as nucleic acids and proteins, to recipient cells in distant organs. In addition to their important roles in both physiological and pathological conditions, exosomes are expected to serve as natural drug carriers without any cytotoxicity, immunogenicity, or tumorigenicity. However, the use of exosomes as drug delivery tools is limited due to the low uptake efficiency of the target cells, insufficient release of the contents from the endosome to the cytosol, and possible adverse effects caused by the delivery to non-target cells. In the present study, we examined the effects of the modification of exosomes with carbonate apatite or a lactose-carrying polymer. Using newly generated monitoring exosomes that contain either firefly luciferase or fused mCherry/enhanced green fluorescent protein, we demonstrated that the modification of exosomes with carbonate apatite improved their release from the endosome into the cytosol in recipient cells. Meanwhile, the modification of exosomes with a lactose-carrying polymer enhanced the selective delivery to parenchymal hepatocytes. These modified exosomes may provide an efficient strategy for macromolecule therapy for incurable diseases that cannot be treated with conventional small-molecule compounds., Competing Interests: Declaration of competing interest We declare that we have no known competing financial interests or personal relationships with other people or organizations that could inappropriately influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

B-type carbonate apatite (CAp) coatings were formed on as-cast and T4-treated Mg- x Zn ( x = 1, 5, and 7 wt %) alloys containing various sized Zn-rich second phase to improve the corrosion resistance and biocompatibility. The CAp coating grew uniformly on the alloys with a thickness of 1.1-1.3 μm and did not show cracks or pores on 30 μm-sized second-phase particles. The CAp coating retarded corrosion of Mg-Zn substrates for the first 3-5 days in Hanks' solution. Polarization resistance of the CAp-coated alloys was 10-90 and 1-70 times higher than the uncoated and hydroxyapatite (HAp)-coated alloys, respectively. The corrosion rate of CAp-coated alloys was greatly affected by the substrate alloys once the coatings were partly broken. The CAp-coated alloys showed 40-60 and 25-45% lower 14-day average corrosion rates than the uncoated and HAp-coated alloys, respectively, in the immersion test. The CAp coating significantly enhanced the viability of osteoblastic MC3T3-E1 cells on the Mg-Zn alloys for 72 h compared to the uncoated and HAp-coated alloys. The cell densities on CAp-coated alloys were similar for 72 h regardless of substrate alloys. Therefore, the CAp coating can be a superior coating candidate for corrosion-control and biocompatibility improvement for biodegradable Mg alloys.

Critical-size segmental defects are formidable challenges in orthopedic surgery. Various scaffolds have been developed to facilitate bone reconstruction within such defects. Many previously studied scaffolds achieved effective outcomes with a combination of high cost, high-risk growth factors or stem cells. Herein, we developed honeycomb scaffolds (HCSs) comprising carbonate apatite (CO 3 Ap) containing 8% carbonate, identical to human bone composition. The CO 3 Ap HCSs were white-columned blocks harboring regularly arranged macropore channels of a size and wall thickness of 156 ± 5 μm and 102 ± 10 μm, respectively. The compressive strengths of the HCSs parallel and perpendicular to the macropore channel direction were 51.0 ± 11.8 and 15.6 ± 2.2 MPa, respectively. The HCSs were grafted into critical-sized segmental defects in rat femurs. The HCSs bore high-load stresses without any observed breakage. Two-weeks post-implantation, calluses formed around the HCSs and immature bone formed in the HCS interior. The calluses and immature bone matured until 8 weeks via endochondral ossification. At 12 weeks post-implantation, large parts of the HCSs were gradually replaced by newly formed bone. The bone reconstruction efficacy of the CO 3 Ap HCSs alone was comparable to that of protein and cell scaffolds, while achieving a lower cost and increased safety., (© 2021 Wiley Periodicals LLC.)

Bone apatite is not hydroxyapatite (HAp), it is carbonate apatite (CO 3 Ap), which contains 6-9 mass% carbonate in an apatitic structure. The CO 3 Ap block cannot be fabricated by sintering because of its thermal decomposition at the sintering temperature. Chemically pure (100%) CO 3 Ap artificial bone was recently fabricated through a dissolution-precipitation reaction in an aqueous solution using a precursor, such as a calcium carbonate block. In this paper, methods of fabricating CO 3 Ap artificial bone are reviewed along with their clinical and animal results. CO 3 Ap artificial bone is resorbed by osteoclasts and upregulates the differentiation of osteoblasts. As a result, CO 3 Ap demonstrates much higher osteoconductivity than HAp and is replaced by new bone via bone remodeling. Granular-type CO 3 Ap artificial bone was approved for clinical use in Japan in 2017. Honeycomb-type CO 3 Ap artificial bone is fabricated using an extruder and a CaCO 3 honeycomb block as a precursor. Honeycomb CO 3 Ap artificial bone allows vertical bone augmentation. A CO 3 Ap-coated titanium plate has also been fabricated using a CaCO 3 -coated titanium plate as a precursor. The adhesive strength is as high as 76.8 MPa, with excellent tissue response and high osteoconductivity., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

The objective of this study was to investigate a bone graft substitute containing carbonate apatite (CO 3 Ap) to analyze bone replacement and the state of bone formation in vitro and in vivo compared with autogenous bone (AB) or control. An osteoclast precursor cell line was cultured with AB or CO 3 Ap, and morphological analysis using scanning electron microscopy and a tartrate-resistant acid phosphatase activity assay were performed. The right maxillary first and second molars of Wistar rats were extracted and compensated by AB or CO 3 Ap granules. Following implantation, the bone formation state was evaluated after 3, 5, 7, 14, and 28 days of surgery by micro-computed tomography and immunohistostaining. The osteoclast-like cell morphology was typical with many cell protrusions in the AB and CO 3 Ap groups. Additionally, the number of osteoclast-like cells formed in the culture increased in each group; however, there was no significant difference between the AB and CO 3 Ap groups. Five days after tooth extraction, osteoclasts were observed near CO 3 Ap. The bone thickness in the CO 3 Ap group was significantly increased than that in the control group and the bone formation in the CO 3 Ap group increased by the same level as that in the AB group. CO 3 Ap is gradually absorbed by osteoclasts in the extraction socket and is easily replaced by alveolar bone. The process of bone replacement by osteoclasts is similar to that of autologous bone. By observing the process of bone replacement in more detail, it may be possible to gain a better understanding of the bone formation and control the amount of bone after surgery.

Carbonate apatite (CO 3 Ap) fabricated by a dissolution-precipitation reaction from a precursor exhibits excellent osteoconductivity and is readily replaced by bone. In the present study, a fully interconnected porous CO 3 Ap block was fabricated by hydrate expansion and carbonation of CaO granules, and the resulting CaCO 3 was then converted to CO 3 Ap. When CaO granules were exposed to 100% humidity CO 2 in a closed vessel, the CaO granules were hydrated and expanded to form a porous Ca(OH) 2 block. The block was then carbonated to form a porous CaCO 3 block, which was then immersed in a Na 2 HPO 4 solution to convert it to a porous CO 3 Ap block. The resulting CO 3 Ap block possessed a fully interconnected porous structure. Histological analyses 4 and 8 weeks after implantation in rabbits revealed that the porous CO 3 Ap block resulted in more significant material resorption and bone formation than the dense CO 3 Ap block. Therefore, it was concluded that a fully interconnected porous CO 3 Ap block fabricated by the hydrate expansion of CaO granules has potential value as a bone substitute.

Introduction: Cancer is one of the top-ranked noncommunicable diseases causing deaths to nine million people and affecting almost double worldwide in 2018. Tremendous advancement in surgery, chemotherapy, radiation and targeted immunotherapy have improved the rate of cure and disease-free survival. As genetic mutations vary in different cancers, potential of customized treatment to silence the problem gene/s at the translational level is being explored too. Yet delivering therapeutics at the required dosage only to the affected cells without affecting the healthy ones, is a big hurdle to be overcome. Scientists worldwide have been working to invent a smart drug delivery system for targeted delivery of therapeutics to tumor tissues only. As part of such an effort, few organic nanocarriers went to clinical trials, while inorganic nanoparticles (NPs) are still in development stage despite their many customizable properties. Carbonate apatite (CA), a pH sensitive nanocarrier has emerged as an efficient delivery system for drugs, plasmids and siRNAs in preclinical models of breast and colon cancers. Like hydroxyapatite (HA) which serves as a classical tool for delivery of genetic materials such as siRNA and plasmid, CA is an apatite-based synthetic carrier. We developed simplified methods of formulating CA-in-DMEM and a DMEM-mimicking buffer and HA in a HEPES-buffered solution and characterized them in terms of size, stability, protein corona (PC) composition, cytotoxicity, siRNA delivery efficiency in breast cancer cells and siRNA biodistribution profile in a mouse model of breast cancer., Methods: Particle growth was analyzed via spectrophotometry and light microscopy, size was measured via dynamic light scattering and scanning electron microscopy and confirmation of functional groups in apatite structures was made by FT-IR. siRNA-binding was analyzed via spectrophotometry. Stability of the formulation solutions/buffers was tested over various time points and at different temperatures to determine their compatibility in the context of practical usage. Cellular uptake was studied via fluorescence microscopy. MTT assay was performed to measure the cytotoxicity of the NPs. Liquid chromatography-mass spectrometry was carried out to analyze the PC formed around all three different NPs in serum-containing media. To explore biodistribution of all the formulations, fluorescence-labeled siRNA-loaded NPs were administered intravenously prior to analysis of fluorescence intensity in the collected organs and tumors of the treated mice., Results: The size of NPs in 10% serum-containing media was dramatically different where CA-in-DMB and HA were much larger than CA-in-DMEM. Effect of media was notable on the PC composition of all three NPs. All three NPs bound albumin and some common protease inhibitors involved in bone metabolism due to their compositional similarity to our bone materials. Moreover, CA also bound heme-binding proteins and opsonins. Unlike CA, HA bound different kinds of keratins. Difference in PC constitution was likely to influence accumulation of NPs in various organs including those of reticuloendothelial system, such as liver and spleen and the tumor. We found 10 times more tumor accumulation of CA-in-DMB than CA-in-DMEM, which could be due to more stable siRNA-binding and distinct PC composition of the former., Conclusion: As a nanocarrier CA is more efficient than HA for siRNA delivery to the tumor. CA prepared in a buffer containing only the mere constituents was potentially more efficient than classical CA prepared in DMEM, owing to the exclusion of interference attributed by the inorganic ions and organic molecules present in DMEM.

Objective: The aims of this study is to investigate the matrix metalloproteinase-2 (MMP-2) levels and the toxicity evaluation to determine the safety of carbonate apatite material that will be used as an endodontic sealer., Methods: Carbonate apatite as endodontic sealer material is fabricated with a size of 2 × 2 × 1 mm, sterilized, and then implanted in the subcutaneous area on the murine back. Total of 28 rats was divided into 2 groups: the implantation group and the control group (positive and negative). We observed behavior, macroscopic and microscopic images (through hematoxylin-eosin/HE staining) and MMP-2 levels in the serum (through ELISA examination) to determine the reaction of implant material in experimental animals., Results: Behavioral test shows impaired motor function within 2-24 h in all rats, autonomic behavioral test does not show any disturbance, macroscopic images show appearance of tumor and rubor within 2-72 h in all rats, microscopic images shows an increase in the mean neutrophils number with the highest point located in the 24 h (3.92×10 3 /μL) and lymphocytes with the highest point in the 14 days (15.31×10 3 /μL). The average value of MMP-2 levels of the negative control group was 1.33 ng/ml, 1.29 ng/ml of the positive control group, and 7.32 ng/ml of the implantation group. Level of MMP-2 in rats with visible implants increased on day 3 (0.75 ng/ml), day 10 (1.49 ng/ml) and day 14 (17.67 ng/ml)., Conclusion: The implantation of carbonate apatite material did not cause behavioral disorders or abnormalities in the tissues surrounding of the implant site and did not show signs of toxicity or death., (© 2020 The Author(s).)

Corrosion-control coatings which can enhance bone formation and be completely replaced by bone are attractive for biodegradable Mg alloys. Carbonate apatite (CAp) and hydroxyapatite (HAp) coatings were formed on Mg-4 wt% Y-3 wt% rare earth (WE43) alloy as a corrosion-control and bioabsorbable coating in the coating solution with various concentrations of NaHCO 3 . The incorporation of carbonate group in apatite structure was examined using X-ray diffraction and Fourier transform infrared spectroscopy. Rat osteoclast precursor and MC3T3-E1 osteoblast cells were cultured on the CAp- and HAp-coated WE43 to examine the osteoclastic resorption and the alkaline phosphatase (ALP) activity, respectively. Mg ions in the used medium were quantified to examine the corrosion-control ability. The NaHCO 3 addition in the solution resulted in the formation of B-type CAp in which the phosphate group of apatite structure was substituted with the carbonate group. The osteoclastic resorption was observed only for the CAp coatings as the cracking of the coatings and the corrosion of substrate WE43 strongly localized under osteoclast cell bodies. The CAp and HAp coatings significantly enhanced the ALP activity of osteoblasts. The CAp-coated WE43 specimens showed 1/5 smaller amount of Mg ion release than the uncoated WE43 on the first day of culturing osteoblasts. For the subsequent 22 days, the Mg ion release was reduced to 1/2 by the CAp coatings. In the presence of osteoclasts, the CAp coatings showed slightly lower corrosion protectiveness than the HAp coating. It was demonstrated that the CAp coatings can be a bioabsorbable and corrosion-control coating for biodegradable Mg alloys., Competing Interests: No potential conflict of interest was reported by the authors., (© 2020 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Since bone apatite is a carbonate apatite containing carbonate in an apatitic structure, carbonate content may be one of the factors governing the osteoconductivity of apatitic bone substitutes. The aim of this study was to evaluate the effects of carbonate content on the osteoconductivity of apatitic bone substitutes using three commercially available bone substitutes for the reconstruction of alveolar bone defects of a beagle mandible with simultaneous dental implant installation. NEOBONE, Bio-Oss, and Cytrans that contain 0.1, 5.5, and 12.0 mass% of carbonate, respectively, were used in this study. The amount of newly formed bone in the upper portion of the alveolar bone defect of the beagle's mandible was 0.7, 6.6, and 39.4% at 4 weeks after surgery and 4.7, 39.5, and 75.2% at 12 weeks after surgery for NEOBONE, Bio-Oss, and Cytrans, respectively. The results indicate that bone-to-implant contact ratio was the largest for Cytrans. Additionally, the continuity of the alveolar ridge was restored in the case of Cytrans, whereas the continuity of the alveolar ridge was not sufficient when using NEOBONE and Bio-Oss. Both Cytrans and Bio-Oss that have a relatively larger carbonate content in their apatitic structure was resorbed with time. We concluded that carbonate content is one of important factors governing the osteoconductivity of apatitic bone substitutes., (© 2019 Wiley Periodicals, Inc.)

The treatment of vertical bone defects caused by severe periodontal disease requires the regeneration of periodontal tissue. Although various bone substitutes have been clinically applied to vertical bone defect correction, the evaluation of these materials in periodontal tissue remains incomplete. The purpose of this study was to examine the bone regeneration abilities of various bone substitutes including Cytrans, Cerasorb, Neobone and Bio-Oss in a 3-wall bone defect animal model. All of these bone substitutes showed a similar healing ability to periodontal ligament and cementum. However, Cytrans showed the fastest bone healing ability compared with the other materials at 4 weeks post-transplantation. In addition, the recruitment of osteoclasts and endothelial cells was observed in Cytrans grafts at 4 weeks, but only detected at 8 weeks in the other materials. These results suggest that Cytrans promotes faster bone healing by inducing bone remodeling and angiogenesis.

Carbonate apatite (CO 3 Ap) granules are known to show good osteoconductivity and replaced to new bone. On the other hand, it is well known that a porous structure allows bone tissue to penetrate its pores, and the optimal pore size for bone ingrowth is dependent on the composition and structure of the scaffold material. Therefore, the aim of this study was to fabricate various porous CO 3 Ap granules through a two-step dissolution-precipitation reaction using CaSO 4 as a precursor and 30-, 50-, 120-, and 205-μm diameter microfibers as porogen and to find the optimal pore size of CO 3 Ap. Porous CO 3 Ap granules were successfully fabricated with pore size 8.2-18.7% smaller than the size of the original fiber porogen. Two weeks after the reconstruction of rabbit calvarial bone defects using porous CO 3 Ap granules, the largest amount of mature bone was seen to be formed inside the pores of CO 3 Ap (120) [porous CO 3 Ap granules made using 120-μm microfiber] followed by CO 3 Ap (50) and CO 3 Ap (30). At 4 and 8 weeks, no statistically significant difference was observed based on the pore size, even though largest amount of mature bone was formed in case of CO 3 Ap (120). It is concluded, therefore, that the optimal pore size of the CO 3 Ap is that of CO 3 Ap (120), which is 85 μm., (© 2019 Wiley Periodicals, Inc.)