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Hydroxyapatite coated metallic implants favorably combine the required biocompatibility with the mechanical properties. As an alternative to the industrial coating method of plasma spraying with inherently potential deleterious effects, sol-gel methods have attracted much attention. In this study, the effects of intermediate silk fibroin and silk sericin layers on the protein adsorption capacity of hydroxyapatite films formed by a particulate sol-gel method were determined experimentally. The preparation of the layered silk protein/hydroxyapatite structures on glass substrates, and the effects of the underlying silk proteins on the topography of the hydroxyapatite coatings were described. The topography of the hydroxyapatite layer fabricated on the silk sericin was such that the hydroxyapatite particles were oriented forming an oriented crystalline surface. The model protein (bovine serum albumin) adsorption increased to 2.62 µg/cm 2 on the latter surface as compared to 1.37 µg/cm 2 of hydroxyapatite on glass without an intermediate silk sericin layer. The BSA adsorption on glass (blank), glass/c-HAp, glass/m-HAp, glass/sericin/c-HAp, and glass/sericin/m-HAp substrates, reported as decrease in BSA concentration versus contact time., (© 2021. The Author(s).)

An essential criterion for the selection of resorbable bioceramics is their ability to degrade inside human body within a reasonable time frame. Furthermore, if the bioceramic can release beneficial ions, such as strontium, as it degrades, recovery time might be shortened. The present study demonstrates that strontium-containing calcium sulfate (Sr,Ca)SO 4 can fulfill these criteria. A long-term in vitro degradation analysis for 12 weeks using sintered (Sr,Ca)SO 4 discs in phosphate buffered solution (PBS) was conducted. The sintered (Sr,Ca)SO 4 disc was then implanted into defects in the distal femur of rats. The degradation rate of (Sr,Ca)SO 4 discs showed a strong dependence on the Sr content. Similar results were observed between the long-term in vitro degradation analysis and the in vivo evaluation. The sintered (3.8%Sr,Ca)SO 4 disc lost more than 80% of its initial weight after soaking in PBS with shaking at 37 °C for 12 weeks. After 12 weeks in vivo, the remaining volume of the (3.8%Sr,Ca)SO 4 disc within the bone defect was ~25%. Over the same time period, new bone was formed at a relative volume of 40%. This study demonstrates the potential of (Sr,Ca)SO 4 bioceramic, and the benefits of using a long-term degradation test during the evaluation of resorbable bioceramics.

A novel bone scaffold containing bioceramic and biopolymer materials with an osteoinductive simvastatin molecule was developed to enhance bone regeneration. An oxidized cellulose nanofiber (OCNF)-Gelatin (Gel) hydrogel was loaded into a biphasic calcium phosphate (BCP) ceramic in which simvastatin was entrapped, resulting in a scaffold with both osteoconductive and osteoinductive properties. The fabricated scaffold showed interconnected porosity with micro- and macroporous orientation. After loading the OCNF-Gel (HG), the mechanical stability of the ceramic BCP scaffold was increased suitable for the application of hard tissue regeneration. Fourier-transform infrared spectroscopy showed that simvastatin was successfully coated on the BCPHG scaffolds. OCNF, with its slower degradation, may contribute to the sustained release of drug from the scaffold. Initially simvastatin was released from the scaffold at high levels, then was constantly and gradually released for up to 4 weeks. Pre-osteoblast MC3T3E1 cells were seeded on the scaffolds to investigate cell viability, morphology, and differentiation. The simvastatin-loaded BCPHG-S scaffolds showed better cell proliferation and spreading compared to other scaffolds. Immunostaining assays showed the expression of proteins responsible for osteogenic differentiation. Alkaline phosphatase and osteopontin were more highly expressed in the BCPHG-S scaffold than in other scaffolds. These results suggest that simvastatin-loaded BCPHG scaffolds provided physiological environments suitable for better osteogenic differentiation., (© 2019 Wiley Periodicals, Inc.)

Drug delivery technology is a promising way to enhance the therapeutic efficacy of drugs. The purpose of this study is to evaluate the physical and chemical properties of hydroxyapatite ceramic microspheres loaded with doxycycline (HADOX), their effects on in vitro osteoblast viability, and their antimicrobial activity, and to determine the effects of DOX on the healing of rat sockets after tooth extraction. The internal microsphere porosity was sensitive to the treatment used to adsorb DOX onto microsphere surface; HA microspheres without DOX presented 26% of pores, whereas HADOX0.15 microspheres presented 52.0%. An initial drug release of 49.15 μg/ml was observed in the first 24 hr. The minimal inhibitory concentration (MIC) tested against Enterococcus faecalis demonstrated that bacterial growth was inhibited for up to 7 days. Results of cell viability and cell proliferation did not indicate statistical differences in the metabolic activity of HADOX samples relative to HA without DOX microspheres (p > .05). After 1 week, a discreet inflammation reaction was observed in the control group, and after 6 weeks, newly-formed bone was observed in the HADOX0.15 (p < .05). The HADOX did not interfere in the bone repair and controlled the early inflammatory response. HADOX could be a promising biomaterial to promote bone repair in infected sites., (© 2019 Wiley Periodicals, Inc.)

A novel bioglass composition (BGMS10), containing strontium and magnesium and characterized by an ultra-high crystallization temperature, is here employed for the first time to produce different composites with the addition of specific amounts of hydroxyapatite. After an investigation of the samples' bioactivity in vitro in a simulated body fluid solution (SBF) - according to a widely used protocol -, the biocompatibility of the new materials was tested with respect to murine fibroblasts both by direct and indirect tests, in order to evaluate possible cytotoxic effects of the materials' eluates. Although none of the samples were cytotoxic and their bioactivity in SBF increased with the increasing amount of the glass in the composite, thus showing the best performance in the case of pure BGMS10 glass, the findings of the biological investigation did not confirm those arising from the SBF assay. Surprisingly, while the composites with the lowest glass amount showed an enhanced biocompatibility in direct tests, on the contrary their biological responsiveness is typically lower in the indirect ones, based on filtered materials' extracts. This fact could be ascribed to the high release of particulate from the composites, which are more porous than the glassy samples: in fact, such pronounced dissolution may affect both the cell viability and the absorbance readings used in the colorimetric assays. The pure BGMS10 glass showed the best biological response only in the cell proliferation test (which is an indirect contact test), being able to stimulate cell proliferation in particular after 24 h. For these reasons, when considering bioactive glasses and bioglass-based composites, the results of direct cell culture assays should be integrated with those obtained by indirect ones, while the findings regarding the in vitro bioactivity in SBF should be interpreted with great care., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Microneedle arrays (MNAs) are a promising mean to administer vaccines. Without the need of highly trained personnel, MNAs can be applied to deliver vaccines into the dermis, which is well equipped to initiate potent immune responses. While vaccination using dissolving microneedle arrays has been extensively investigated, the use of solid nanoporous MNAs (npMNAs) to deliver vaccines remained largely unexplored. In this report we investigated whether npMNAs with an average pore size of 80 nm, can be used for influenza vaccination based on recombinant hemagglutinin (HA) protein of the 2009 pandemic H1N1 (pH1N1) virus. Fluorescently labeled HA loaded in the npMNAs was effectively delivered into the skin of mouse ears, as a result of a diffusion-based process. Compared to intramuscular immunization, intradermal HA vaccination of mice using npMNAs elicited high levels of HA antigen specific antibodies, with pH1N1 hemagglutination inhibition and neutralization activity. Moreover, mice vaccinated with pH1N1 HA loaded npMNAs were completely protected against a potentially lethal challenge with mouse adapted pH1N1 virus. These results illustrate that intradermal subunit vaccine immunization using npMNAs is a promising approach to facilitate effective vaccination., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Chronic osteomyelitis and infected bone defects are substantial challenges faced by orthopaedic surgeons. In this study, vancomycin was loaded into mesoporous bioactive glass (MBG) to form a local antibiotic delivery system and then a bone tissue-engineering scaffold combining MBG and poly-(L-lactic-co-glycolic acid) (PLGA) was prepared by freeze-drying fabrication. In vitro degradation and water contact angle analysis suggested that the MBG-incorporated PLGA scaffold exhibited controlled degradability, stabilizing the pH of the surrounding environment and improved the hydrophilicity. Moreover, the presence of MBG provides a well-interconnected pore structure, to which human bone marrow-derived mesenchymal stem cells can attach, spread and proliferate, promoting upregulation of the expression of osteogenic markers. Thus, MBG/PLGA scaffolds exhibit better cytocompatibility and osteoblastic difierentiation properties compared with pure PLGA scaffolds. Vancomycin-loaded scaffolds have been found to yield sustained release that lasts for more than eight weeks in vitro. We tested the antibacterial performance of vancomycin-loaded scaffolds against Staphylococcus aureus, the most common bacteria isolated from infected bone. In vitro experiments demonstrated that loading vancomycin onto the scaffold promoted antibacterial activity and inhibited biofilm formation without deleterious effect on cytocompatibility. In conclusion, the novel inorganic-organic composites are considered potential materials for the treatment of infected bone defects.

In this study, bone tissue engineered scaffolds fabricated via powder-based 3D printing from hydroxyapatite (HA) and calcium sulphate (CaSO 4 ) powders were investigated. The combination of using a fast resorbing CaSO 4 based powder and the relatively slower HA powder represents a promising prospect for tuning the bioresorption of 3D printed (3DP) scaffolds. These properties could then be tailored to coincide with tissue growth rate for different surgical procedures. The manufactured scaffolds were infiltrated with poly(ε‑caprolactone) (PCL). The PCL infiltrated the inter-particle spacing within the 3DP structures due to the nature of a loosely-packed powder bed and also covered the surface of ceramic-based scaffolds. Consequently, the average compressive strength, compressive modulus and toughness increased by 314%, 465% and 867%, respectively. The resorption behaviour of the 3DP scaffolds was characterised in vitro using a high-throughput system that mimicked the physiological environment and dynamic flow conditions relevant to the human body. A rapid release of CaSO 4 between Day 0 and 28 was commensurate with a reduction in scaffold mass and compressive properties, as well as an increase in medium absorption. In spite of this, HA particles, connected by PCL fibrils, remained within the microstructure after 56 days resorption under dynamic conditions. Consequently, a high level of structural integrity was maintained within the 3DP scaffold. This study presented a porous PCL-HA-CaSO 4 3DP structure with the potential to encourage new tissue growth during the initial stages of implantation and also offering sufficient structural and mechanical support during the bone healing phase., (Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.)

Porous ceramics doped with silicon and pure β-TCP were analyzed in terms of internal microstructure, cell behavior, and the percentage of newly formed bone. Additionally the materials were tested to determine which of the two had better properties to load and release vancomycin hydrochloride. Internal pore distribution and porosity were determined through high pressure mercury porosimetry and the specific surface area was measured by the Brunauer Emmet-Teller method. The proliferation and viability of the human osteoblast-like cell line MG-63 was studied to validate both materials. The materials were tested on eight New Zealand rabbits which created defects, 10 mm in diameter, in the calvaria bone. After 8 and 12 weeks a histological and histomorphometric analysis was performed. Si-β-TCP showed a higher porosity and specific surface area. The cytocompatibility test revealed acceptable results in terms of proliferation and viability whereas the percentage of new bone was higher in Si-β-TCP with a two-time study being statistically significant with 12 weeks of healing (p < 0.05).The vancomycin loaded within the ceramic scaffolds were burst released and the material had the ability to inhibit bacterial growth. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2307-2315, 2018., (© 2017 Wiley Periodicals, Inc.)

There is increasing interest in biodegradable ceramic scaffolds for bone tissue engineering capable of in situ delivery of ionic species favoring bone formation. Strontium has been shown to be osteogenic, but strontium-containing drugs such as strontium ranelate, used in Europe for the treatment of osteoporosis, are now restricted due to clinical evidence of systemic effects. By doping fluorapatite-based glasses with strontium, we developed ceramic scaffolds with fully interconnected macroporosity and cell size similar to that of cancellous bone, that are also capable of releasing strontium. The crystallization behavior, investigated by XRD and SEM, revealed the formation of akermanite and fluorapatite at the surface of strontium-free glass-ceramic scaffolds, and strontium-substituted fluorapatite at the surface of the strontium-doped scaffolds. At 8 weeks after implantation in a rat calvarial critical size defect, scaffolds doped with the highest amount of strontium led to the highest mineral apposition rate. A significantly higher amount of newly-formed bone was found with the strontium-free glass-ceramic scaffold, and possibly linked to the presence of akermanite at the scaffold surface. We demonstrate by energy dispersive XRF analyses of skull sections that strontium was present in newly formed bone with the strontium-doped scaffolds, while a significant amount of fluorine was incorporated in newly formed bone, regardless of composition or crystallization state., Statement of Significance: The present work demonstrates the in vivo action of strontium-containing glass-ceramic scaffolds. These bone graft substitutes are targeted at non load-bearing bone defects. Results show that strontium is successfully incorporated in newly formed bone. This is associated with a significantly higher Mineral Apposition Rate. The benefits of in situ release of strontium are demonstrated. The broader scientific impact of this works builds on the concept of resorbable ceramic scaffolds as reservoirs of ionic species capable of enhancing bone regeneration., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The bone-induction capacity of a porous biphasic calcium phosphate (pBCP) using heterotopic implantation in mouse (mHI-model) and its efficacy as substitute for autograft in mandibular critical-size defect in rabbit (rabMCSD-model) was investigated. In mHI-model, pBCP was implanted into the thigh muscles and bone formation was histomorphometrically and immunohistochemically evaluated. In rabMCSD-model, 13 mm bone defects were treated with pBCP or autograft and bone repair comparatively evaluated by radiographic and histomorphometric methods. In mHI-model, formed bone and immunolabeling for bone morphogenetic protein-2 and osteopontin were observed in 90% of pBCP implanted samples after 12 weeks. In rabMCSD-model neither statistically significant difference was found in newly formed bone between pBCP and autograft groups at 4 weeks (18.8 ± 5.5% vs 27.1 ± 5.6%), 8 weeks (22.3 ± 2.7% vs 26.2 ± 5.1), and 12 weeks (19.6 ± 4.7% vs 19.6 ± 2.3%). At 12 weeks, the stability and contour of the mandible were restored in both treatments. Near tooth remaining, pBCP particles were covered by small amount of mineralized tissue exhibiting perpendicular attachments of collagen fiber bundles with histological characteristic of acellular cementum. Within the limitations of this study, it was concluded that pBCP is osteoinductive and able to stimulate the new formation of bone and cementum-like tissues in rabMCSD-model, suggesting that it may be an alternative to treatment of large bone defect and in periodontal regenerative therapy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1546-1557, 2018., (© 2017 Wiley Periodicals, Inc.)

The high alkali content bioactive glasses commonly used to regenerate bone in dental, orthopedic, and maxillofacial surgeries induce some cytotoxicity in surrounding tissues. The present study aims the ability of some alkali-free bioactive glasses compositions, recently developed by our research group, to stimulate human mesenchymal stem cells (hMSCs) differentiation into osteoblasts in comparison to 45S5 Bioglass ® . The obtained results demonstrated that alkali-free bioactive glasses possess higher stimulating towards differentiation of hMSCs in comparison to the control 45S5 Bioglass ® . The von Kossa assay demonstrated that all bioactive glasses studied were able to induce the appearance of calcium deposits even when the cells were cultured in DMEM, proving that these biomaterials per se induce hMSCs cell differentiation. It was also observed that in both cell culture medium used (DMEM, and osteogenesis differentiation medium) alkali-free bioactive glasses clearly induced the appearance of more calcium deposits than the 45S5 Bioglass ® , indicating their greater ability to induce cell differentiation. In summary, these results indicate that alkali-free bioactive glasses are a safe and valid alternative to 45S5 Bioglass ® . © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2360-2365, 2017., (© 2016 Wiley Periodicals, Inc.)

Despite many studies, the impact of ceramic particles on cell behavior remains unclear. The aim of the present study was to investigate the effects of nano-sized ceramic particles on fibroblastic cells. Fibroblasts (dermal fibroblasts freshly isolated from skin samples and WI26 fibroblastic cells) were cultured in a monolayer in the presence of alumina or cerium-zirconia particles (≈50 nm diameter) at two concentrations (100 or 500 μg ml -1 ). Fluorescent alumina particles were also used. The following properties were analyzed: cell morphology, cytoplasmic ceramic incorporation (using confocal and transmission electron microscopy) and migration (using a silicon insert). Sedimentation field-flow fractionation (SdFFF) was also used to evaluate the rate of incorporation of ceramic particles into the cells. Finally, after treatment with various concentrations of ceramic particles, fibroblasts were also included in a collagen type I lattice constituting a dermal equivalent (DE), and the collagen lattice retraction and cell proliferation were evaluated. In monolayer conditions, the presence of both alumina and cerium-zirconia ceramic particles did not cause any deleterious effects on cultured cells (dermal fibroblast and WI26 cells) and cell fate was not affected in any way by the presence of ceramic particles in the cytoplasm. Confocal (using fluorescent alumina particles) and electron microscopy (using both alumina and cerium-zirconia particles) showed that ceramic particles were internalized in the WI26 cells. Using fluorescent membrane labeling and fluorescent alumina particles, a membrane was observed around the particle-containing vesicles present in the cytoplasm. Electron microscopy on WI26 cells showed the presence of a classical bilayer membrane around the ceramic particles. Interestingly, SdFFF confirmed that some dermal fibroblasts contained many alumina ceramic particles while others contained very few; in WI26 cells, the uptake of alumina ceramic was more homogeneous. In DE, collagen lattice retraction and cell proliferation were unchanged when WI26 fibroblastic cells contained alumina or cerium-zirconia ceramic particles. Our data suggest that ceramic particles are internalized in the cells by endocytosis. The presence of ceramic particles in the cytoplasm has no affect on cell behavior, confirming the excellent biocompatibility of this material and anticipating a minimal harmful effect of potential wear debris.

Titanium (Ti 4+ ) containing materials have been widely used in medical applications due to its associated bioactivity in vivo. This study investigates the replacement of Si 4+ with Ti 4+ within the system SiO 2 -Na 2 O-CaO-P 2 O 5 to determine its influence on glass structure. This strategy was conducted in order to control the glass solubility to further improve the cellular response. Ti 4+ incorporation was found to have little influence on the glass transition temperature (T g  = 520 ± 8°C) and magic angle spinning-nuclear magnetic resonance (MAS-NMR) shifts (-80 ppm) up to additions of 18 wt %. However, at 30 wt % the T g increased to 600°C and MAS-NMR spectra shifted to -88 ppm. There was also an associated reduction in glass solubility as a function of Ti 4+ incorporation as determined by inductively coupled plasma optical emission spectroscopy where Si 4+ (1649-44 mg/L) and Na + (892-36 mg/L) levels greatly reduced while Ca 2+ (3-5 mg/L) and PO43- (2-7 mg/L) levels remained relatively unchanged. MC3T3 osteoblasts were used for cell culture testing and it was determined that the Ti 4+ glasses increased cell viability and also facilitated greater osteoblast adhesion and proliferation to the glass surface compared to the control glass. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1703-1712, 2016., (© 2015 Wiley Periodicals, Inc.)

Periodontal disease is associated with the destruction of periodontal tissues, along with other disorders/problems including inflammation of tissues and severe pain. This paper reports the synthesis of meloxicam (MX) immobilized biodegradable chitosan (CS)/poly(vinyl alcohol) (PVA)/hydroxyapatite (HA) based electrospun (e-spun) fibers and films. Electrospinning was employed to produce drug loaded fibrous mats, whereas films were generated by solvent casting method. In-vitro drug release from materials containing varying concentrations of MX revealed that the scaffolds containing higher amount of drug showed comparatively faster release. During initial first few hours fast release was noted from membranes and films; however after around 5h sustained release was achieved. The hydrogels showed good swelling property, which is highly desired for soft tissue engineered implants. To investigate the biocompatibility of our synthesized materials, VERO cells (epithelial cells) were selected and cell culture results showed that these all materials were non-cytotoxic and also these cells were very well proliferated on these synthesized scaffolds. These properties along with the anti-inflammatory potential of our fabricated materials suggest their effective utilization in periodontital treatments., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Over the past few years, nanoparticles and their role in drug delivery have been the centre of attraction as new drug delivery systems. Various forms of nanosystems have been designed, such as nanoclays, scaffolds and nanotubes, having numerous applications in areas such as drug loading, target cell uptake, bioassay and imaging. The present study discusses various types of nanoparticles, with special emphasis on ceramic nanocarriers. Ceramic materials have high mechanical strength, good body response and low or non-existing biodegradability. In this article, the various aspects concerning ceramic nanoparticles, such as their advantages over other systems, their cellular uptake and toxicity concerns are discussed in detail.

Novel chitosan-polyvinyl pyrrolidone/45S5 Bioglass® (CS-PVP/BG) scaffolds were prepared via foam replication and chemical cross-linking techniques. The pristine BG, CS-PVP coated BG and genipin cross-linked CS-PVP/BG (G-CS-PVP/BG) scaffolds were synthesized and characterized in terms of chemical composition, physical structure and morphology respectively. Resistance to enzymatic degradation of the scaffold is improved significantly with the use of genipin cross-linked CS-PVP. The bio-effects of scaffolds on MC3T3-E1 osteoblast-like cells were evaluated by studying cell viability, adhesion and proliferation. The CCK-8 assay shows that cell viability on the resulting G-CS-PVP/BG scaffold is improved obviously after cross-linking of genipin. Cell skeleton images exhibit that well-stretched F-actin bundles are obtained on the G-CS-PVP/BG scaffold. SEM results present significant improvement on the cell adhesion and proliferation for cells cultured on the G-CS-PVP/BG scaffold. The drug release performance on the as-synthesized scaffold was studied in a phosphate buffered saline (PBS) solution. Vancomycin is found to be released in burst fashion within 24h from the pristine BG scaffold, however, the release period from the G-CS-PVP/BG scaffold is enhanced to 7days, indicating improved drug release properties of the G-CS-PVP/BG scaffold. Our results suggest that the G-CS-PVP/BG scaffolds possess promising physicochemical properties, sustained drug release capability and good biocompatibility for MC3T3-E1 cells' proliferation and adhesion, suggesting their potential applications in areas such as MC3T3-E1 cell stimulation and bone tissue engineering., (Copyright © 2015. Published by Elsevier B.V.)

Iron-bioceramic composites have been developed as biodegradable implant materials with tailored degradation behavior and bioactive features. In the current work, in vivo bioactivity of the composites was comprehensively studied by using sheep animal model. Five groups of specimens (Fe-HA, Fe-TCP, Fe-BCP composites, and pure-Fe and SS316L as controls) were surgically implanted into medio proximal region of the radial bones. Real-time ultrasound analysis showed a decreased echo pattern at the peri-implant biodegradation site of the composites indicating minimal tissue response during the wound healing process. Peripheral whole blood biomarkers monitoring showed a normal dynamic change of blood cellular responses and no stress effect was observed. Meanwhile, the released Fe ion concentration was increasing along the implantation period. Histological analysis showed that the composites corresponded with a lower inflammatory giant cell count than that of SS316L. Analysis of the retrieved implants showed a thicker degradation layer on the composites compared with pure-Fe. It can be concluded that the iron-bioceramic composites are bioactive and induce a preferable wound healing process., (© 2014 Wiley Periodicals, Inc.)

Hydroxyapatite (HA) is widely used as a bioactive ceramics as it forms a chemical bond with bone. However, the drawback to using this material is its inferior mechanical properties. In this research, surface corrosion and disintegration of nanoscaled HA in a dog were studied, and the mechanism by which phase-pure HA dissolved in vivo was investigated. Biological properties of HA in vivo are affected by the grain-boundary dissolution followed by a surface corrosion and microstructural disintegration. This kind of dissolution process, apparently evidenced at the grain boundary, causes particle generation, which indicates that both long-term bone in-growth and mechanical properties can dramatically deteriorate. Implant dissolution by osteoclasts in vivo is also observed on the surface of hydroxyapatite. Implant surface showed an aggressive corrosion by an osteoclast resorption. Severe and deeper dissolution underwent close to osteoclast resulting in formation of smaller and more round particle shape.

The progress in bone cancer surgery and multimodal treatment concept achieve only modest improvement in the overall survival, due to failure in clearing out residual cancer cells at the surgical margin and extreme side-effects of adjuvant postoperative treatments. Our study aims to propose a new method based on cyclodextrin polymer (polyCD) functionalized hydroxyapatite (HA) for achieving a high local drug concentration with a sustained release profile and a better control of residual malignant cells via local drug delivery and promotion of the reconstruction of bone defects. PolyCD, a versatile carrier for therapeutic molecules, can be incorporated into HA (bone regeneration scaffold) through thermal treatment. The parameters of polyCD treatment on the macroporous HA (porosity 65%) were characterized via thermogravimetric analysis. Good cytocompatibility of polyCD functionalized bioceramics was demonstrated on osteoblast cells by cell vitality assay. An antibiotic (gentamicin) and an anticancer agent (cisplatin) were respectively loaded on polyCD functionalized bioceramics for drug release test. The results show that polyCD functionalization leads to significantly improved drug loading quantity (30% more concerning gentamicin and twice more for cisplatin) and drug release duration (7 days longer concerning gentamicin and 3 days longer for cisplatin). Conclusively, this study offers a safe and reliable drug delivery system for bioceramic matrices, which can load anticancer agents (or/and antibiotics) to reduce local recurrence (or/and infection)., (© 2014 Wiley Periodicals, Inc.)

Infection remains a significant problem associated with biomedical implants and orthopedic surgeries, especially in revision total joint replacements. Recent advances in antibiotic-releasing bone void fillers (BVF) provide new opportunities to address these types of device-related orthopedic infections that often lead to substantial economic burdens and reduced quality of life. We report improvements made in fabrication and scalability of an antibiotic-releasing polycaprolactone-calcium carbonate/phosphate ceramic composite BVF using a new solvent-free, molten-cast fabrication process. This strategy provides the ability to tailor drug release kinetics from the BVF composite based on modifications of the inorganic substrate and/or the polymeric component, allowing extended tobramycin release at bactericidal concentrations. The mechanical properties of the new BVF composite are comparable to many reported BVFs and validate the relative homogeneity of fabrication. Most importantly, fabrication quality controls are correlated with favorable drug release kinetics, providing bactericidal activity to 10 weeks in vitro when the polycaprolactone component exceeds 98% w/w of the total polymer fraction. Furthermore, in a time kill study, tobramycin-releasing composite fragments inhibited S. aureus growth over 48 h at inoculums as high as 10(9) CFU/mL. This customizable antibiotic-releasing BVF polymer-inorganic biomaterial should provide osseointegrative and osteoconductive properties while contributing antimicrobial protection to orthopedic sites requiring the use of bone void fillers., (© 2013 Wiley Periodicals, Inc.)

Osteomyelitis is a bacterial disease that can become chronic, and treatment often includes a surgical operation to remove infected bone. The aim of this study was to develop and investigate in vitro bone filling composite materials that release ciprofloxacin to kill any remaining bacteria and contain bioceramic to help the bone to heal. Three composites of poly(L-lactide-co-ε-caprolactone), β-tricalcium phosphate and ciprofloxacin were compounded using twin-screw extrusion and sterilized by gamma irradiation. Drug release and degradation of the composites were investigated in vitro for 52 weeks. The composite with 50 wt% of β-TCP had the most promising ciprofloxacin release profile. The ceramic component accelerated the drug release that occurred in three phases obeying first-order kinetics. Inhibition zone testing using bioluminescence showed that the released ciprofloxacin had effect in eradicating a common osteomyelitis causing bacteria Pseudomonas aeruginosa. During the in vitro degradation test series, molar weight of the polymer matrix of the composites decreased rapidly. Additionally, (1)H-NMR analysis showed that the polymer had blocky structure and the comonomer ratio changed during hydrolysis. The tested composites showed great potential to be developed into bone filler materials for the treatment of osteomyelitis or other bone related infections.

Purpose: The aim of this study is to describe the role of bone marrow aspirate in treatment of the benign bone lesions by comparing two groups of patients (16 patients in each group) with benign bone lesions treated with surgical curettage and filling the defect with either composite ceramic graft hydrated with bone marrow aspirate "group 1" or composite ceramic graft alone without a bone marrow aspirate "group 2"., Materials and Methods: The mean age was 19.7 years (group 1) and 18.5 years (group 2). The mean size of the cavitary bone lesions was 29.2 cm(2) (group 1) and 25.9 cm(2) (group 2). The mean follow-up period was 47 months., Results: The percentage of ceraform resorption had increased from 31.3% at 6 months to 75.4% at 36 months for group 1 patients and from 20.9% at 6 months to 60.3% at 36 months for group 2 patients. The percentage of bone trabeculation through the cavitary defects had increased from 30.3% at 6 months to 85.5% at 36 months for group 1 patients and from 18.9% at 6 months to 72.0% at 36 months for group 2 patients. The mean of the percentage of ceraform persistence at 36 months after its implantation was 24.6% for group 1 patients and 39.7% for group 2 patients., Conclusion: Adding bone marrow aspirate to ceraform biphasic ceramic had hastened the rate of its resorption and had decreased the rate of its persistence.

There are several degradation mechanisms of resin-composite restorations and possible deleterious effects created by leached components cannot be ignored. Additionally, the surface integrity influences the long-term clinical performance of resin-composite restorations and can be affected by several factors. Novel technologies have been proposed, but there is a lack of information considering the degradation resistance of such materials. The aim of this study was to investigate the degradation resistance of silorane (SIL), pure-ormocer (ORM) and dimethacrylate (ELS and GRD) resin-based dental composites. Water sorption and solubility tests were adapted from ISO4049, color change trough the CIELab parameters after 24h and 30d immersion in distilled water. Knoop hardness readings were performed at the aforementioned periods and the percentage of hardness decrease was considered. Results were analyzed with one-way ANOVA followed by Tukey's test (P = 0.05). SIL and GRD produced lower water sorption than ORM and ELS. SIL presented the lowest solubility. All materials demonstrated acceptable results for color stability. SIL demonstrated the more stable surface, when considering surface hardness, in aqueous environment. It can be concluded that i) silorane and ormocer-based materials did not produced higher color stability than dimethacrylates in distilled aqueous media; and ii) silorane-based materials exhibited lower water solubility and lower hardness decreases after water immersion than dimethacrylate-based resin-composites, while the pure-ormocer-baed material not.

Three types of ceramic scaffolds with different composition and structure [namely synthetic 100% hydroxyapatite (HA; Engipore), synthetic calcium phosphate multiphase biomaterial containing 67% silicon stabilized tricalcium phosphate (Si-TCP; Skelite) and natural bone mineral derived scaffolds (Bio-oss)] were seeded with mesenchymal stem cells (MSC) and ectopically implanted for 8 and 16 weeks in immunodeficient mice. X-ray synchrotron radiation microtomography was used to derive 3D structural information on the same scaffolds both before and after implantation. Meaningful images and morphometric parameters such as scaffold and bone volume fraction, mean thickness and thickness distribution of the different phases as a function of the implantation time, were obtained. The used imaging algorithms allowed a direct comparison and registration of the 3D structure before and after implantation of the same sub-volume of a given scaffold. In this way it was possible to directly monitor the tissue engineered bone growth and the complete or partial degradation of the scaffold. Further, the detailed kinetics studies on Skelite scaffolds implanted for different length of times from 3 days to 24 weeks, revealed in the X-ray absorption histograms two separate peaks associated to HA and TCP. It was therefore possible to observe that the progressive degradation of the Skelite scaffolds was mainly due to the resorption of TCP. The different saturation times in the tissue engineered bone growth and in the TCP resorption confirmed that the bone growth was not limited the scaffold regions that were resorbed but continued in the inward direction with respect to the pore surface.

In the last few years the biomedical research field has shown a growing interest towards nanostructured mesoporous silica materials, whose chemical composition is silica and present nanometric pores. These bioceramics exhibit two important features: they can regenerate osseous tissues--the bond bioactivity of these materials has been confirmed by the formation of biological-like nanoapatites on their surface when in contact with physiological fluids--and they are able to act as controlled release systems. Drugs in the nanometre scale can be loaded on those matrices and then locally released in a controlled fashion. It is possible to chemically modify the silica walls to favour the adsorption of certain biomolecules such as peptides, proteins or growth factors. It is even possible to design smart biomaterials where the drug is released under an external stimulus. Thus, looking at all those properties, a question arises: Have these bioceramics good expectations to be used in clinical medical practice? Their biocompatibility, bioactivity, capacity to regenerate bone and ability to act as controlled release systems of biologically active species have been confirmed. In fact, their preliminary in vitro and in vivo essays have been positive. Now it is the time to adequate all these properties to the actual clinical problems, and to evaluate their efficiency in comparison with materials already known and currently employed such as bioglasses.

Carbonate-substituted hydroxyapatite (CHA) is more osteoconductive and more resorbable than hydroxyapatite (HA), but the underlying mode of its action is unclear. We hypothesised that increased resorption of the ceramic by osteoclasts might subsequently upregulate osteoblasts by a coupling mechanism, and sought to test this in a large animal model. Defects were created in both the lateral femoral condyles of 12 adult sheep. Six were implanted with CHA granules bilaterally, and six with HA. Six of the animals in each group received the bisphosphonate zoledronate (0.05 mg/kg), which inhibits the function of osteoclasts, intra-operatively. After six weeks bony ingrowth was greater in the CHA implants than in HA, but not in the animals given zoledronate. Functional osteoclasts are necessary for the enhanced osteoconduction seen in CHA compared with HA.

Characterizations of hydroxyapatite (HA), biphasic calcium phosphate (BCP) and beta tricalcium phosphate (beta-TCP) ceramic particles were carried out using X-ray diffusion (XRD), Scanning electron micrograph (SEM), Particle Sizer and Zeta potential analyzer. Competitive adsorption of bovine serum albumin (BSA) and lysozyme (LSZ) on the three calcium phosphates were investigated by polyacrylamide gel electrophoresis (PAGE) method. The results showed that HA, BCP and beta-TCP ceramic particles with irregular shapes and similar size distributions all had negative surface net charges in pH7.4 phosphate buffered saline (PBS) solution and exhibited alike behaviors of BSA and LSZ adsorption. LSZ had higher affinity for calcium phosphate ceramics than BSA and its adsorption on them didn't be almost influenced by the increasing of BSA concentration in the solution. Electrostatic interaction played an important role on the competitive adsorption of BSA and LSZ on the surface of calcium phosphate ceramic particles.

Bioabsorbable and functionally graded apatite (fg-HAp) ceramics were designed using bovine bone by the calcination and partial dissolution-precipitation methods. The fg-HAp ceramics that were developed had gradual distributions of the degree of crystallinity and the grain size of single-phase hydroxyapatite from the surface layer of the pore wall to the bulk structure region. Calcination at 1073 K gave a specific surface area of 30 m2 x g-1 and porosities of 60-80%. The pore structure of the fg-HAp was classified into two regions: a macro-pore region (100-600 microm) originating from spongy bone and a micro-pore region (10-160 nm) related to body fluid permeation and blood permeability. By implantation in subcutaneous tissue of rat, it was confirmed that body fluid permeated the bulk region of the fg-HAp ceramics through the micro-pores. The volumetric populations occupied by body fluid were 60% at 4 weeks and 68% at 8 weeks in the ceramics explants, indicating drastic bioabsorption, although the body fluid was found to be immunopositive for an albumin as the main serum protein in blood. On the fg-HAp ceramics developed here, the bioabsorption rate could be controlled by careful selection of the calcination temperature. These ceramics can be applied as new biomimetic ceramics exhibiting surface and bulk degradations and cellular absorption by giant cells., ((c) 2005 Wiley Periodicals, Inc)

Novel bioactive and biodegradable glass ceramics with high mechanical strength in the (50-x/2)CaO. SiO(2)--xB(2)O(3) (4.2 < or = x < or = 17.2) system were investigated. The systems consisted of three phases: monoclinic wollastonite, calcium metaborate, and amorphous borosilicate matrix. The glass ceramics containing 4.2 mol% and 8.4 mol% B(2)O(3) showed high bulk density and a dense microstructure. Mechanical strengths of the glass ceramics were higher than those of other bioactive ceramics: high compressive strength (2813 MPa), bending strength of 212 MPa, and fracture toughness of 3.12 MPa. m(1/2). The glass-ceramic formed apatite layer on their surface in the simulated body fluid and showed significant biodegradation. The degree of apatite formation in the glass ceramics depended on the calcium metaborate content and borosilicate glassy matrix. Additional calcium metaborate and borosilicate glassy matrix increased the apatite formation rate on the surface. It might be likely that calcium metaborate causes supersaturation of Ca ions, for its high solubility in SBF and the water-reactive borosilicate glassy matrix formed Sibond;OH groups on the surface to provide nucleation sites for apatite formation. Also, through in vitro test for the biocompatibility of the CaO--SiO(2)--B(2)O(3) glass ceramics, no cytotoxicity of the glass ceramics were found. The results on bioactivity and noncytotoxicity indicated that glass ceramics in the (50-x/2)CaO. SiO(2)--xB(2)O(3) (4.2 < or = x < or = 17.2) system could be useful as a biodegradable bone replacement material., (Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 79-89, 2004)

Zinc is an essential trace element that has stimulatory effects on bone formation. Recently, we developed zinc-releasing calcium phosphate ceramics in order to add the pharmacologic effect of zinc to calcium phosphate ceramics. In our previous study, we showed that the optimum zinc content for promoting bone formation was 0.316 wt %. Therefore a zinc composite ceramic of zinc-containing beta-tricalcium phosphate and hydroxyapatite, with a zinc content of 0.316 wt %, was chosen for long-term implantation. Cylindrical rods of the zinc composite ceramic were implanted in rabbit femora for 2 to 60 weeks. Using computer-aided image analysis, a histomorphometric study was carried out to investigate bone formation and resorption around the implants. The control was a composite ceramic of beta-tricalcium phosphate and hydroxyapatite without zinc. The addition of zinc to the implant demonstrated both favorable and unfavorable effects on bone remodeling. The favorable effect was enhanced bone apposition to the implant surface, demonstrated by a significant increase in intramedullary bone apposition rate at 6 weeks and in cortical bone apposition rate at 24 and 60 weeks (p < 0.05). The unfavorable effect was increased bone resorption, demonstrated by a significant increase in medullary cavity area at 60 weeks (p < 0.05). In order to utilize the favorable effect and avoid the unfavorable effect of zinc, either a reduction in zinc content in the zinc composite ceramic or the selection of implantation sites that do not have excessive exposure to bone marrow are required., (Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 468-474, 2003)

An analysis of 238Pu in the whole body donation to the U.S. Transuranium and Uranium Registries (USTUR) is presented. This donor accidentally inhaled an unusual physical form of plutonium, predominantly the 238Pu isotope in the form of a highly insoluble ceramic. Along with six other workers accidentally exposed at the same time, this donor excreted little or no 238Pu in his urine for several months. Subsequently, however, and, with no further intakes, the urinary excretion of 238Pu by all of these workers increased progressively. Such a pattern of increasing urinary excretion of plutonium resulting from a single acute inhalation was unknown at the time. The subject of this study provided a unique opportunity to analyze not only the pattern of urinary excretion for 17 y following this unusual intake but also the complete distribution of 238Pu in his donated body tissues and skeleton at death. Radiochemical analyses of tissues from this whole body donation were used to perform critical tests of the applicability and accuracy of the respiratory tract model and the systemic biokinetic models for plutonium currently recommended by the International Commission on Radiological Protection. The respiratory tract model was applied to analyze the donor's long-term urinary excretion pattern. The facility provided by this model to represent progressive transformation of insoluble particles in the lungs into a more soluble form, applied in conjunction with the systemic biokinetic model, predicted the total amount of 238Pu measured in the donor's body to within 17% accuracy. The measured division of 238Pu between the donor's lungs and systemic organs was predicted to within 10%. Small adjustments to several rate constants in these models provided precise predictions of the absolute amounts of 238Pu in the lungs, thoracic lymph nodes, liver, red bone marrow, skeleton (including the distribution of 238Pu between trabecular and cortical bone matrices derived from the radiochemical analyses), kidneys, testes, and muscle. The resulting individual-specific parameters were applied to evaluate the equivalent dose rates and cumulative doses received by the donor's organs and the overall effective dose. Whereas these individual modifications to the ICRP models provided a more accurate representation of the distribution of dose between the donor's organs, it was determined that the ICRP models provided an adequate estimate of the overall effective dose.

The present work investigates, in situ, the in vitro bioactivity of partially crystallized 45S5 Bioglass (BG) as a function of immersion time in a simulated body fluid (SBF) using atomic force microscopy (AFM). The results obtained for the crystallized BG were compared to those of hydroxyapatite c- and a-faces. The calcium phosphate layer grows on the crystallized 45S5 B by multiple two-dimensional nucleation and fusion of these two-dimensional islands, which is essentially the same mode as for the hydroxyapatite c-face. The surface of the crystallized 45S5 BG was almost fully covered with a dense and compact calcium phosphate layer after 24 h. The calcium phosphate formation on the crystallized BG arises from a low surface energy of the surface layer and/or an effect of the layer to lower the resistance when the growth units of calcium phosphate incorporate into the growing island. These results indicate that the crystallized 45S5 BG is suitable to be used as a filler for polymeric matrix bioactive composites, as it maintains a high bioactivity associated with a stiffer behavior (as compared to standard BG)., (Copyright 2002 Wiley Periodicals, Inc.)

Canasite glass-ceramics were modified by either increasing the concentration of calcium in the glass, or by the addition of P2O5. Samples of these novel materials were placed in simulated body fluid (SBF), along with a control material (commercial canasite), for periods ranging from 12 h to 28 days. After immersion, surface analysis was performed using thin film X-ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopy equipped with energy dispersive X-ray detectors. The concentrations of sodium, potassium, calcium, silicon, and phosphorus in the SBF solution were measured using inductively coupled plasma emission spectroscopy. No apatite was detected on the surface of commercial canasite, even after 28 days of immersion in SBF. A crystalline apatite layer was formed on the surface of a P2O5-containing canasite after 5 days, and after 3 days for calcium-enriched canasite. Ion release data suggested that the mechanism for apatite deposition was different for P2O5 and non-P2O5-containing glass-ceramics., (Copyright 2001 John Wiley & Sons, Inc.)

Tricalcium phosphate ceramics (TCPs) are increasingly used as bone substitutes. They demonstrate good biocompatibility and degrade relatively slowly. New glass ceramics based on calcium alkali orthophosphates (Ca(2)KNa(PO(4))(2)) were developed that degrade faster than TCP but could have reduced biocompatibility due to their high solubility. Therefore, they were modified by a neutralizing surface treatment. The aim of this study was to evaluate the biocompatibility of some of these ceramics, GB1a, GB9, and GB14, which differ in the amount of added Na, K, Mg, or Si ions, with standard and modified surfaces. The in vitro cytotoxicity of the ceramics GB1a, GB9, and GB14 was determined by the agar diffusion and filter test and the microculture tetrazolium (MTT) assay. In order to investigate the influence of surface modification, these three ceramics were compared to their surface-treated counterparts, GB1aN, GB9N, and GB14N. GB1a, the ceramic with the highest in vitro solubility, showed the strongest toxic influence in all cell culture tests. GB9 and GB14 produced better results. In contrast, the counterparts with modified surfaces exhibited no (GB9N, GB14N) or weak (GB1aN) signs of cytotoxicity. It is concluded that the toxicity of the ceramics GB1a, GB9, and GB14 depends on their solubility. A positive influence of the surface treatment on in vitro biocompatibility was demonstrated. Therefore, the surface-treated glass ceramics could be promising materials for bone replacement., (Copyright 2001 John Wiley & Sons, Inc. J Biomed Mater Res 55: 285-294, 2001)

The effect of the ionic products of Bioglass 45S5 dissolution on the gene-expression profile of human osteoblasts was investigated by cDNA microarray analysis of 1,176 genes. Treatment with the ionic products of Bioglass 45S5 dissolution increased the levels of 60 transcripts twofold or more and reduced the levels of five transcripts to one-half or less than in control. Markedly up-regulated genes included RCL, a c-myc responsive growth related gene, cell cycle regulators such as G1/S specific cyclin D1, and apoptosis regulators including calpain and defender against cell death (DAD1). Other significantly up-regulated genes included the cell surface receptors CD44 and integrin beta1, and various extracellular matrix regulators including metalloproteinases-2 and -4 and their inhibitors TIMP-1 and TIMP-2. The identification of differentially expressed genes by cDNA microarray analysis has offered new insights into the mode of action of bioactive glasses and has proven to be an effective tool in evaluating their osteoproductive properties., (Copyright 2001 John Wiley & Sons, Inc.)

Because the inhalation of asbestos, a naturally occurring, inorganic fibrous material, is associated with lung fibrosis and thoracic cancers, concerns have been raised about the possible health effects of synthetic vitreous fibers (SVFs). SVFs include a very broad variety of inorganic fibrous materials with an amorphous molecular structure. Traditionally, SVFs have been divided into three subcategories based on composition: fiberglass, mineral wool (rock, stone, and slag wools), and refractory ceramic fiber. For more than 50 years, the toxicologic potential of SVFs has been researched extensively using human epidemiology and a variety of laboratory studies. Here we review the research and its impact on hazard classification and regulation of SVFs. Large, ongoing epidemiology studies of SVF manufacturing workers have provided very little evidence of harmful effects in humans. Several decades of research using rodents exposed by inhalation have confirmed that SVF pulmonary effects are determined by the "Three D's", fiber dose (lung), dimension, and durability. Lung dose over time is determined by fiber deposition and biopersistence in the lung. Deposition is inversely related to fiber diameter. Biopersistence is directly related to fiber length and inversely related to fiber dissolution and fragmentation rates. Inhaled short fibers are cleared from the lung relatively quickly by mobile phagocytic cells, but long fibers persist until they dissolve or fragment. In contrast to asbestos, most of the SVFs tested in rodent inhalation studies cleared rapidly from the lung (were nonbiopersistent) and were innocuous. However, several relativley biopersistent SVFs induced chronic inflammation, lung scarring (fibrosis), and thoracic neoplasms. Thus, biopersistence of fibers is now generally recognized as a key determinant of the toxicologic potential of SVFs. In vitro dissolution of fibers in simulated extracellular fluid correlates fairly well with fiber biopersistence in the lung and pulmonary toxicity, but several exceptions suggest that biopersistence involves more than dissolution rate. Research demonstrating the relationship between biopersistence and SVF toxicity has provided a scientific basis for hazard classification and regulation of SVFs. For a nonhazardous classification, legislation recently passed by the European Union requires a respirable insulation wool to have a low lung-biopersistence or be noncarcinogenic in laboratory rats. U.S. fiberglass and mineral wool industries and the Occupational Health and Safety Administration (OSHA) have formed a voluntary Health and Safety Partnership Program (HSPP) that include: a voluntary permissible exposure level (PEL) in the workplace of 1 fiber/cc, a respiratory protection program for specified tasks, continued workplace air monitoring, and, where possible, the development of fiber formulations that do not persist in the lung. RCF manufacturers have implemented a Product Stewardship Program that includes: a recommended exposure guideline of 0.5 fibers/cc; a 5-year workplace air monitoring program; and research into the development of high-temperature-resistant, biosoluble fibers.

The aim of this work was to develop a calcium phosphate cement (CPC) providing controlled release of the antibiotic gentamicin sulfate (GS) over at least 1 week. The CPC was made of beta-tricalcium phosphate [beta-TCP; beta-Ca(3)(PO(4))(2)], monocalcium phosphate monohydrate [MCPM; Ca(H(2)PO(4))(2). H(2)O] and water. Release of GS was controlled by admixture of poly(acrylic acid) (PAA). The effects on the GS release kinetics of the molecular weight of PAA, of the amount of admixed PAA, and of the pH of the release medium were investigated. A typical cement sample weighed 3.6 g and contained 100 mg of GS and between 0 and 150 mg of PAA. In the following, PAA content is expressed as the weight ratio, lambda, with respect to GS. At a low PAA content in the CPC (lambda < 0.7), GS was released over 1-2 days according to a square-root-of-time kinetics, but not all GS was released. The unreleased GS fraction increased from 0 to 58% with an increase of PAA content (up to lambda = 0.7). At high PAA content (lambda > 0.7), GS was released over a period of up to 8 days according to a combination of a square-root-of-time and a zero-order kinetics. The total GS fraction released increased again from 58 to 100% with an increase of the amount of PAA (up to lambda = 1.5). These observations were explained by molecular interaction between PAA and GS resulting in gel formation. The maximum fraction of GS released from the cement was indeed a function of the solubility of the PAA-GS (coacervate) complex in the release medium. Thus, GS release was controlled by two mechanisms: (1) diffusion of free GS molecules through the porous cement (square-root-of-time kinetics); and (2) dissociation of GS from the PAA-GS complex (zero-order kinetics). The first mechanism was predominant at low lambda, whereas the second mechanism became important at high lambda and later release times. As the solubility of the PAA-GS complex decreased with an increase in PAA molecular weight, the higher molecular weight PAA yielded more prolonged release periods of up to 8 days. Interestingly, the use of 450 kDa PAA at lambda = 1.00 provided an almost constant release profile over a period of 7 days. Gel formation between PAA and GS was explained in terms of hydrogen bonding of PAA carboxyl groups with GS amino groups. The molar ratio between carboxyl groups and amino groups in the gel was estimated to be approximately 1.9. In conclusion, admixture of PAA into calcium phosphate cement appeared to be a very elegant tool to control the release of the antibiotic over a period of 7 to 8 days., (Copyright 2000 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 89:1262-1270, 2000)

Synthetic vitreous fibers (SVFs) are a broad class of inorganic vitreous silicates used in a large number of applications including thermal and acoustical insulation and filtration. Historically, they have been grouped into somewhat artificial broad categories, e.g., glass, rock (stone), slag, or ceramic fibers based on the origin of the raw materials or the manufacturing process used to produce them. In turn, these broad categories have been used to classify SVFs according to their potential health effects, e.g., the International Agency for Research on Cancer and International Programme for Chemical Safety in 1988, based on the available health information at that time. During the past 10-15 years extensive new information has been developed on the health aspects of these fibers in humans, in experimental animals, and with in vitro test systems. Various chronic inhalation studies and intraperitoneal injection studies in rodents have clearly shown that within a given category of SVFs there can be a vast diversity of biological responses due to the different fiber compositions within that category. This information has been further buttressed by an in-depth knowledge of differences in the biopersistence of the various types of fibers in the lung after short-term exposure and their in vitro dissolution rates in fluids that mimic those found in the lung. This evolving body of information, which compliments and explains the results of chronic animal studies clearly show that these "broad" categories are somewhat archaic, oversimplistic, and do not represent current science. This new understanding of the relation between fiber composition, solubility, and biological activity requires a new classification system to more accurately reflect the potential health consequences of exposure to these materials. It is proposed that a new classification system be developed based on the results of short-term in vivo in combination with in vitro solubility studies. Indeed, the European Union has incorporated some of this knowledge, e.g., persistence in the lung into its recent Directive on fiber classification., (Copyright 2000 Academic Press.)

Introduction and Objectives: A number of man-made vitreous fibers (MMVF) have been developed over the years to replace asbestos fibres in its uses as insulating material. Concerns have been raised that these man-made fibers may also pose a significant health hazard when inhaled during their manufacture and application. As will be discussed in this brief overview, dose, dimension and durability of fibrous particles are key parameters with respect to the induction of adverse pulmonary effects, including carcinogenicity as well as non-cancer effects. In particular, fiber biopersistence plays a most important role for pulmonary pathogenicities, and consequently biopersistence receives greatest attention in the search of new fibrous materials., Methods and Results: Tests to evaluate fiber biopersistence include the administration of fibers by a short-term inhalation (5 days) or intratracheal instillation into rats. Advantages of the inhalation methodology include the even distribution throughout the lung administered by a physiological process. A disadvantage of this method is the limited respirability of long fibers in the rat whereas they are well respirable by humans. Such long fibers ( > 20 microm) have the greatest potential for tumorigenicity and need special consideration in connection with the evaluation of fiber biopersistence. Enrichment of the inhaled aerosol by these long fibers needs to be considered in order to deposit enough of them in the lower respiratory tract of the rat. In contrast, the advantage of the instillation technique is that these long fibers can be delivered to the lung. However, the major disadvantages of intratracheal instillations are the potential of the administered fibers to form clumps and aggregates in the airways and the induction of a major inflammatory response when high-bolus doses are administered. This could influence fiber dissolution in the lungs significantly., Conclusions: At the same delivered lung dose, a fiber of low biopersistency has the least effect and is, therefore, less likely to induce lung or pleural tumors even under chronic exposure conditions. Respective animal studies with more fibers of different biopersistence have confirmed this general principle. It is very important that, when evaluating and interpreting fiber effects observed in experimental animals, species differences with respect to respirability, lung retention and mechanisms of responses are considered.

We show that available experimental data from long-term experiments are consistent with the hypothesis that the oncogenic potential of man-made fibers is determined completely by their biopersistence. We present an analysis of these data within the initiation-promotion-progression paradigm of carcinogenesis. Our method of analysis takes explicit account of the temporal pattern of fiber burden in the rat lung, and suggests that fibers act as initiators in the lung. We estimate a dose-dependent initiation parameter and show how it can be transported to human populations for assessment of the risk of lung cancer following exposure to man-made fibers.

This study investigated the in vivo performance of two composite injectable bone substitutes (IBS), each with different calcium-phosphate particles granulometries [40-80 (IBS 40-80) and 200-500 microm (IBS 200-500)]. These biomaterials were obtained by associating a biphasic calcium-phosphate (BCP) ceramic mineral phase with a 3% aqueous solution of a cellulosic polymer (hydroxy-propyl-methyl-cellulose). Both materials were injected for periods of 2, 3, 8, or 12 weeks into bone defects at the distal end of rabbit femurs. Quantitative results on new bone formation, BCP resorption, and staining for tartrate-resistant acid phosphatase (TRAP) activity were studied for statistical purposes. Measurements with scanning electron microscopy and image analysis showed that the final rates of newly formed bone were similar for both tested IBS after 12 weeks of implantation. Bone colonization occurred more extensively during early implantation times for IBS 40-80 than for IBS 200-500. For the latter, BCP degradation occurred regularly throughout the implantation period, whereas it was very intensive during the first 2 weeks for IBS 40-80. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than for IBS 200-500 regardless of implantation time. With the granulometry of either mineral phase, both tested IBS supported extensive bone colonization, which was greater than that previously reported for an equivalent block of macroporous BCP. The resorption-bone substitution process seemed to occur earlier and faster for IBS 40-80 than for IBS 200-500. Both tested IBS expressed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability., (Copyright 1999 John Wiley & Sons, Inc.)

Degradation of three types of sintered calcium phosphate ceramic spheres was investigated in vitro at low pH conditions (LPC) and in an in vivo model, that is, injection into a mouse peritoneal cavity. Degradation was observed under both conditions. The rate of degradation depended on the type of ceramic, with beta-TCP degrading faster than HA and HA degrading faster than FA. Degradation was characterized by dissolution of the necks and the formation of cracks and irregularities in the grains. Intraperitoneal injection of the spheres into a mouse peritoneal cavity led to the formation of foreign body granulomas in which degradation could be observed. The in vivo degradation pattern was similar to that observed in vitro, but longer implantation times resulted in a further degradation. Small fragments rich in Ca and P were present in inclusion bodies. Calcium phosphate crystals sometimes also were observed in mitochondria, many of which were subject to lysis. We observed that ceramic type and implantation period also were related to the number of dead cells in the granulomas. Furthermore, extracellular deposits were seen between cells and ceramic spheres. Ca and P and also Fe were detected in these deposits. The presence of Fe is indicative of a lysosomal origin and thus of exocytotic activity., (Copyright 1999 John Wiley & Sons, Inc.)

Calcium phosphate ceramics recently have been used for administering therapeutic agents in bone. The present work investigated the efficacy of macroporous biphasic calcium phosphate (MBCP) implants as a matrix for local delivery of human growth hormone (hGH). An initial study showed that the release of 5 microg of hGH loaded onto MBCP cylinders was rapid during the first 48 h and sustained for a total of 11 days. The biological integrity of hGH (88.2%) was checked using a specific bioassay (cellular proliferation of hGH-sensitive Nb2 cells) in comparison with a radioimmunoassay to calculate the proportion of bioactive hGH released. MBCP cylinders then were loaded with 1, 10, and 100 microg of hGH and implanted into rabbit femurs (n = 16) to determine hGH effects on bone ingrowth and ceramic resorption, as evaluated by scanning electron microscopy and image analysis. Results indicated that hGH increased bone ingrowth and ceramic resorption significantly in comparison with contralateral and control implants. Biochemical parameters monitored in rabbit plasma showed that hGH did not produce detectable systemic effects. Thus the use of MBCP appears to be effective for local delivery of hGH and for increasing bone ingrowth.

A ceramics preparation (Cleansand-205), which was coated with a mixture of the oxides of Si, Al, Ti, and Ag, was found to inactivate Lactobacillus phage PL-1 suspended in a buffer solution. The inactivation of phage was dependent on the amounts of Cleansand-205 added, and the reaction obeyed almost first-order reaction kinetics. The phage inactivation was considerably accelerated by the presence of light.

A newly produced bioceramic, beta-Ca2P2O7 with addition of Na4P2O7.10H2O (SDCP), has been implanted into the femoral condyle of rabbits. Within 6 weeks after implantation, most of the bioceramic is replaced by new woven bone. On the contrary, block from hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), which are osteoconductible, do not resorb within a short period of time. We believe that the biodegradable behaviour of SDCP may occur in two steps. The first and most important step is the digestion of particles and migration of the particles by phagocytosis. The object of this study is to examine the change in morphologies, chemical compositions and crystal structure of SDCP after soaking in distilled water for a certain period of time. The SDCP ceramic was also co-cultured with leucocytes to observe how the SDCP particles were digested by the leucocytes, so that the mechanism of biodegradable behaviour of SDCP ceramic in vivo might be clarified. Four types of sintered calcium phosphate ceramics were tested in the experiment: SDCP, pure beta-Ca2P2O7 (DCP), HA and beta-TCP. They wee soaked in distilled water at 37 degrees C for up to 30 days. The microstructure and morphology of crystals deposited on the surface were observed using scanning electron microscopy. Sodium, calcium and phosphorus ion contents in the supernatant solution were detected by atomic absorption analysis and ion coupled plasma. In summary, HA and DCP showed no significant evidence of dissolution in distilled water. In static distilled water, calcium ions may be released from beta-TCP into solution during the initial 7 days and then converted into HA by reprecipitation. The results showed that the SDCP was firstly dissolved into small grains or fragments by the solution. The small fragments should be so small as to be digested by the phagocytes in a physiological environment.

Purpose: This study was undertaken to determine the resorption rate of porous ceramic implants. The hypothesis was that implants placed in soft tissues would degrade more rapidly than implants placed in bone., Materials and Methods: To test this hypothesis, implants were manufactured by applying a thin coating of hydroxylapatite onto an interconnected, porous calcium carbonate substrate. Control implants were made entirely of hydroxylapatite with identical microstructure. Two adult dogs received a total of 56 implants placed in the femur, skeletal muscle, and subcutaneous tissues. After killing the animals at 4 months, the specimens were removed, embedded in plastic, sectioned, and either stained for light microscopic examination or subjected to quantitative image analysis using a scanning electron microscope., Results: Contrary to the hypothesis, the rate of degradation was faster for implants placed in bone than in soft tissue. Within the 4 months, degradation was 24% to 63% in bone, depending on the composition. However, it was not statistically significant in either intramuscular or subcutaneous tissue. A surprising observation was that bone ingrowth occurred in 67% of the implants placed in soft tissues. On average, it was 4.3% in intramuscular sites and 6.6% in subcutaneous sites. This bone was histologically normal in 71% of the implants containing bone., Conclusion: This study demonstrates that porous ceramic implants composed of hydroxylapatite on calcium carbonate will degrade more rapidly in bone defects than in soft tissue sites. In addition, implants with interconnected porosity and surfaces of hydroxylapatite will become ingrown with bone even after placement in soft tissues. The exact mechanisms for both of these phenomena are not understood.

The surfaces of bioactive Ca-P ceramics immediately change when exposed to proteinaceous solutions. The dissolution behavior and protein interactions of these bioactive materials at the bone/implant interface need to be investigated to understand their material-cellular interactions fully. In this study, FT-IR/ATR techniques were used to study the in situ phosphate release kinetics of Ca-P coatings. The net loss of phosphate molecules from coatings was slower in saline solutions compared with alpha-MEM solutions. Coatings exposed to alpha-MEM solutions containing fibronectin released phosphate molecules slower than coatings exposed to alpha-MEM solutions containing albumin. Conformational changes in fibronectin and albumin adsorbed onto Ca-P and uncoated germanium surfaces were also investigated using FT-IR/ATR spectroscopy. Analysis of changes in the amide I bands indicated that there was a greater loss of beta-sheet structure in adsorbed fibronectin on Ca-P coatings when compared with bare germanium surfaces. Although albumin did change its structure upon adsorption on both Ca-P and germanium, unlike fibronectin, adsorbed albumin structure was similar on Ca-P coatings and germanium. Furthermore, with time the conformation of adsorbed fibronectin and albumin appeared to be very stable on Ca-P coatings, whereas albumin adsorbed to germanium exhibited an increase in ratio of alpha-helix to beta-turn.

There is now a substantial body of experimental data on the pulmonary biopersistence of man-made vitreous silicate fibers (MMVSF), but human data are seriously lacking. Our knowledge in this field is essentially limited to a few reports of measurements of fibers retained in lung tissue samples taken at autopsy from workers manufacturing these products. Three types of exposure were studied: fibrous glass, mineral wool, and refractory ceramic fibers. Overall, the available data do not provide evidence for substantial long-term retention of fibers in the human lung after occupational exposure to MMVSF dusts. A word of caution, however; the amount of data supporting the previous statement is much greater for fibrous glass than for either mineral wool or refractory ceramic fibers. There is no human data on the key question of the kinetics of pulmonary clearance of inhaled MMVSF.