Search

Allicin, the active compound of garlic extract, is a naturally sourced biomolecule, which promotes a vast range of health benefits. However, the limited stability of allicin restricts its applications in tissue engineering. Additionally, the detailed effects of allicin in bone health are yet to be explored. Our work reports on the fabrication of a novel allicin-loaded hydroxyapatite drug delivery system with enhanced biological properties. The fabricated system shows excellent antibacterial efficiency against

Classification of proteins into their respective functional categories remains a long-standing key challenge in computational biology. Machine Learning (ML) based discriminative algorithms have been used extensively to address this challenge; however, the presence of small-sized, noisy, unbalanced protein classification datasets where high sequence similarity does not always imply identical functional properties have prevented robust prediction performance. Herein we present a ML method,Ensemble method for enZymeClassification (EnZymClass), that is specifically designed to address these issues. EnZymClass makes use of 47 alignment-free feature extraction techniques as numerically encoded descriptors of protein sequences to construct a stacked ensemble classification scheme capable of categorizing proteins based on their functional attributes. We used EnZymClass to classify plant acyl-ACP thioesterases (TEs) into short, long and mixed free fatty acid substrate specificity categories. While general guidelines for inferring substrate specificity have been proposed before, prediction of chain-length preference from primary sequence has remained elusive. EnZymClass achieved high classification metric scores on the TE substrate specificity prediction task (average accuracy score of 0.8, average precision and recall scores of 0.87 and 0.89 respectively on medium-chain TE prediction) producing accuracy scores that are about twice as effective at avoiding misclassifications than existing similarity-based methods of substrate specificity prediction. By applying EnZymClass to a subset of TEs in the ThYme database, we identified two acyl-ACP TE, ClFatB3 and CwFatB2, with previously uncharacterized activity inE. colifatty acid production hosts. We incorporated modifications into ClFatB3 established in prior TE engineering studies, resulting in a 4.2-fold overall improvement in observed C10titers over the wildtype enzyme.EnZymClass can be readily applied to other protein classification challenges and is available at:https://github.com/deeprob/ThioesteraseEnzymeSpecificityAuthor SummaryThe natural diversity of proteins has been harnessed to serve specialized applications in various fields, including medicine, renewable chemical production, and food and agriculture. Acquiring and characterizing new proteins to meet a given application, however, can be an expensive process, requiring selection from thousands to hundreds of thousands of candidates in a database and subsequent experimental screening. Using amino acid sequence to predict a protein’s function has been demonstrated to accelerate this process, however standard approaches require information on previously characterized proteins and their respective sequences. Obtaining the necessary amount of data to accurately infer sequence-function relationships can be prohibitive, especially with a low-throughput testing cycle. Here, we present EnZymClass, a model that is specifically designed to work with small to medium-sized protein sequence datasets and retain high prediction performance of function. We applied EnZymClass to predict the presence or absence of a desired function among acyl-ACP thioesterases, a key enzyme class used in the production of renewable oleochemicals in microbial hosts. By training EnZymClass on only 115 functionally characterized enzyme sequences, we were able to successfully detect two plant acyl-ACP thioesterases with the desired specialized function among 617 sequences in the ThYme database.

Load-bearing bone substitutes must be designed to stimulate bone formation and allow crosstalk between the two primary skeletal cells, bone-forming osteoblasts, and bone-resorbing osteoclasts. Compared to the dense implants, surface-modified, additively manufactured porous implants have shown osteogenic potential. Surface modification of metal implants by plasma-sprayed hydroxyapatite (HA) coating, show better clinical applicability due to their significant osteogenic potential, through better osteoblast proliferation and osseointegration. This study investigates additively manufactured porous metallic surface and plasma-sprayed HA-coated Ti on the proliferation and differentiation of monocytic cells into osteoclasts and their resorptive activity. Our results reveal that porous Ti6Al4V and porous Ta enhanced TRAP activity, compared to the control (p

With an increasing life expectancy and aging population, orthopedic defects and bone graft surgeries are increasing in global prevalence. Research to date has advanced the understanding of bone biology and defect repair mechanism, leading to a marked success in the development of synthetic bone substitutes. Yet, the quest for functionalized bone grafts prompted the researchers to find a viable alternative that regulates cellular activity and supports bone regeneration and healing process without causing serious side-effects. Recently, researchers have introduced natural medicinal compounds (NMCs) in bone scaffold that enables them to release at a desirable rate, maintains a sustained release allowing sufficient time for tissue in-growth, and guides bone regeneration process with minimized risk of tissue toxicity. According to World Health Organization (WHO), NMCs are gaining popularity in western countries for the last two decades and are being used by 80% of the population worldwide. Compared to synthetic drugs, NMCs have a broader range of safety window and thus suitable for prolonged localized delivery for bone regeneration. There is limited literature focusing on the integration of bone grafts and natural medicines that provides detailed scientific evidences on NMCs, their toxic limits and particular application in bone tissue engineering, which could guide the researchers to develop functionalized implants for various bone disorders. This review will discuss the emerging trend of NMC delivery from bone grafts, including 3D-printed structures and surface-modified implants, highlighting the significance and potential of NMCs for bone health, guiding future paths toward the development of an ideal bone tissue engineering scaffold. STATEMENT OF SIGNIFICANCE: To date, additive manufacturing technology provids us with many advanced patient specific or defect specific bone constructs exhibiting three-dimensional, well-defined microstructure with interconnected porous networks for defect-repair applications. However, an ideal scaffold should also be able to supply biological signals that actively guide tissue regeneration while simultaneously preventing post-implantation complications. Natural biomolecules are gaining popularity in tissue engineering since they possess a safer, effective approach compared to synthetic drugs. The integration of bone scaffolds and natural biomolecules exploits the advantages of customized, multi-functional bone implants to provide localized delivery of biochemical signals in a controlled manner. This review presents an overview of bone scaffolds as delivery systems for natural biomolecules, which may provide prominent advancement in bone development and improve defect-healing caused by various musculoskeletal disorders.

Natural medicines have long been used to treat physiological ailments where both ginger (gingerol) and garlic (allicin) are key players in immune system promotion, reduction in blood pressure, and lowering inflammation response. With their efficacy in bone healing, these compounds have great value as medicinal additives in bone scaffolds for localized treatment to support tissue formation, along with providing their natural therapeutic benefits. Utilization of 3D-printed (3DP) bone tissue engineering scaffolds as drug delivery vehicles for ginger and garlic extracts enables patient specificity in bone defect applications with enhanced osseointegration. Our objective is to understand their combined efficacy on osteogenesis when released from 3DP calcium phosphate bone scaffolds designed with a bimodal pore distribution. With a porous core and dense exterior, the resulting scaffolds have good mechanical integrity with 10 ± 1 MPa compressive strengths. Results show that ginger + garlic extracts released from bone scaffolds enhance their osteogenic potential through on site drug delivery. Both compounds exhibit exponential drug release profiles which fit Weibull distribution equations. The release of ginger extract also increases osteoblast proliferation by 59%. Both compounds show decreased osteoclast resorption activity, with a greater than 20% reduction in pit area on sample surfaces. Ginger + garlic extract induces a twofold increase in early osteoid tissue formation in vivo at week 4, in addition to a 30% increase in total bone area and a 90% increase in osteocytes with respect to control 3DP tricalcium phosphate scaffolds. Late-stage bone healing at week 10 reveals healthy angiogenic tissue, a twofold higher bone mineralization, and significant enhancement of type I collagen formation in the presence of ginger and garlic extracts. Naturally sourced ginger and garlic extracts provide osteogenic promotion and improved bone tissue in-growth in a patient-specific 3DP scaffold biomedical device for low load-bearing bone tissue engineering and dental applications.

Bioprinting of cellular aggregates, such as tissue spheroids, to form three-dimensional (3D) complex-shaped arrangements, has posed a major challenge due to lack of robust, reproducible and practical bioprinting techniques. Here, we demonstrate 3D aspiration-assisted freeform bioprinting of tissue spheroids by precisely positioning them in self-healing yield-stress gels, enabling the self-assembly of spheroids for fabrication of tissues. The presented approach enables the traverse of spheroids directly from the cell media to the gel and freeform positioning of the spheroids on demand. We study the underlying physical mechanism of the approach to elucidate the interactions between the aspirated spheroids and the gel’s yield-stress during the transfer of spheroids from cell media to the gel. We further demonstrate the application of the proposed approach in the realization of various freeform shapes and self-assembly of human mesenchymal stem cell spheroids for the construction of cartilage and bone tissues.

Hydroxyapatite-coated titanium alloys have been a popular choice as bone implants for load-bearing applications for the compositional similarity of hydroxyapatite to natural bone. The limited osteoinductive properties exhibited by the hydroxyapatite (HA) coatings have led to the incorporation of growth factor or dopants for improved osseointegration. This study aims to investigate the effects of a naturally occurring aloe vera gel extract, acemannan, in doped hydroxyapatite coatings on the

Biofabricated tissues have found numerous applications in tissue engineering and regenerative medicine in addition to the promotion of disease modeling and drug development and screening. Although three-dimensional (3D) printing strategies for designing and developing customized tissue constructs have made significant progress, the complexity of innate multicellular tissues hinders the accurate evaluation of physiological responses in vitro. Cellular aggregates, such as spheroids, are 3D structures where multiple types of cells are co-cultured and organized with endogenously secreted extracellular matrix and are designed to recapitulate the key features of native tissues more realistically. 3D Bioprinting has emerged as a crucial tool for positioning of these spheroids to assemble and organize them into physiologically- and histologically-relevant tissues, mimicking their native counterparts. This has triggered the convergence of spheroid fabrication and bioprinting, leading to the investigation of novel engineering methods for successful assembly of spheroids while simultaneously enhancing tissue repair. This review provides an overview of the current state-of-the-art in spheroid bioprinting methods and elucidates the involved technologies, intensively discusses the recent tissue fabrication applications, outlines the crucial properties that influence the bioprinting of these spheroids and bioprinted tissue characteristics, and finally details the current challenges and future perspectives of spheroid bioprinting efforts in the growing field of biofabrication.

Calcium phosphate (CaP)-based ceramics are a popular choice for bone-graft applications due to their compositional similarities with bone. Similarly, Bioactive glass (BG) is also common for bone tissue engineering applications due to its excellent biocompatibility and bone binding ability. We report tricalcium phosphate (TCP)-BG (45S5 BG) composite scaffolds using conventional processing and binder jetting-based 3D printing (3DP) technique. We hypothesize that BG's addition in TCP will enhance densification via liquid phase sintering and improve mechanical properties. Further, BG addition to TCP should modulate the dissolution kinetics in vitro. This work's scientific objective is to understand the influence of random vs. designed porosity in TCP-BG ceramics towards variations in compressive strength and in vitro biocompatibility. Our findings indicate that a 5 wt% BG in TCP composite shows a compressive strength of 26.7 ± 2.7 MPa for random porosity structures having a total porosity of ~47.9%. The same composition in a designed porosity structure shows a compressive strength of 21.3 ± 2.9 MPa, having a total porosity of ~54.1%. Scaffolds are also tested for their dissolution kinetics and in vitro bone cell materials interaction, where TCP-BG compositions show favorable bone cell materials interactions. The addition of BG enhances a flaky hydroxycarbonate apatite (HCA) layer in 8 weeks in vitro. Our research shows that the porous TCP- BG scaffolds, fabricated via binder jetting method with enhanced mechanical properties and dissolution properties can be utilized in bone graft applications.

Aspiration-assisted freeform bioprinting (AAfB) has emerged as a promising technique for precise placement of tissue spheroids in three-dimensional (3D) space enabling tissue fabrication. To achieve success in embedded bioprinting using AAfB, an ideal support bath should possess shear-thinning behavior and yield-stress to facilitate tight fusion and assembly of bioprinted spheroids forming tissues. Several studies have demonstrated support baths for embedded bioprinting in the past few years, yet a majority of these materials poses challenges due to their low biocompatibility, opaqueness, complex and prolonged preparation procedures, and limited spheroid fusion efficacy. In this study, to circumvent the aforementioned limitations, we present the feasibility of AAfB of human mesenchymal stem cell (hMSC) spheroids in alginate microgels as a support bath. Alginate microgels were first prepared with different particle sizes modulated by blending time and concentration, followed by determination of the optimal bioprinting conditions by the assessment of rheological properties, bioprintability, and spheroid fusion efficiency. The bioprinted and consequently self-assembled tissue structures made of hMSC spheroids were osteogenically induced for bone tissue formation. Alongside, we investigated the effects of peripheral blood monocyte-derived osteoclast incorporation into the hMSC spheroids in heterotypic bone tissue formation. We demonstrated that alginate microgels enabled unprecedented positional accuracy (∼5%), transparency for visualization, and improved fusion efficiency (∼97%) of bioprinted hMSC spheroids for bone fabrication. This study demonstrates the potential of using alginate microgels as a support bath for many different applications including but not limited to freeform bioprinting of spheroids, cell-laden hydrogels, and fugitive inks to form viable tissue constructs.

Hydroxyapatite-coated titanium alloys have been a popular choice as bone implants for load-bearing applications for the compositional similarity of hydroxyapatite to natural bone. The limited osteo...

The objective of this study was to understand the effects of ceramic polymer composite and pH of the surrounding vicinity on the release kinetics of doxorubicin. Different concentrations of polymers with polycaprolactone (PCL), poly glycolic lactic acid (PLGA), and a blend of PCL–PLGA with hydroxyapatite (HA) were investigated for doxorubicin release at physiological pH of 7.4 and an acidic pH of 5.0 caused by immediate surgery. Burst release of 20% was observed from bare HA at pH 7.4 over a week, whereas all the polymer incorporated discs showed sustained release. The hydrophilic–hydrophobic and hydrophobic–hydrophobic interactions between the polymer and the drug altered by the surrounding pHs were found to be pivotal in controlling the release kinetics of drug. No cytotoxicity of the drug at a concentration of 50 µg per disc was observed at early time points when cultured with osteoblast cells; however, the same drug dosage inhibited osteosarcoma cell viability. This study mainly bases on the comprehension of the effects of chemistry, environment, and polymer–drug interactions, leading to a beneficial understanding towards the design of drug delivery devices.

Osteoporosis is one of the most commonly identified bone disorders, which leads to an enhanced risk of bone fracture, especially for the older population. Hydroxyapatite (HA) coated titanium (Ti) alloys have been used widespread for load bearing applications like hip or knee replacements owing to their compositional similarity to natural bone; however, incorporation of osteoinductivity is still a challenge. The objective of this study is to evaluate the effects of SiO2 and ZnO as dopants in HA coated Ti alloys on cellular osteoporotic conditions mimicked by an in vitro osteoblast and osteoclast coculture model. HA, Si-HA, and Zn-HA coatings showed adhesive bond strengths of 25.7 ± 1.9 MPa, 23.8 ± 2.3 MPa, and 22.9 ± 3.5 MPa, respectively. To study the effects of doped HA coatings on the simulated osteoporotic cellular condition, human mesenchymal stem cells (hMSCs) and monocytes (THP-1) were seeded simultaneously in a ratio of 1:4, respectively. Gene expressions studies were carried out with marker genes ...

The association of the receptor binding domain (RBD) of SARS-CoV-2 viral spike with human angiotensin converting enzyme (hACE2) represents the first required step for viral entry. Amino acid changes in the RBD have been implicated with increased infectivity and potential for immune evasion. Reliably predicting the effect of amino acid changes in the ability of the RBD to interact more strongly with the hACE2 receptor can help assess the public health implications and the potential for spillover and adaptation into other animals. Here, we introduce a two-step framework that first relies on 48 independent 4-ns molecular dynamics (MD) trajectories of RBD-hACE2 variants to collect binding energy terms decomposed into Coulombic, covalent, van der Waals, lipophilic, generalized Born electrostatic solvation, hydrogen-bonding, π-π packing and self-contact correction terms. The second step implements a neural network to classify and quantitatively predict binding affinity using the decomposed energy terms as descriptors. The computational base achieves an accuracy of 82.2% in terms of correctly classifying single amino-acid substitution variants of the RBD as worsening or improving binding affinity for hACE2 and a correlation coefficient r of 0.69 between predicted and experimentally calculated binding affinities. Both metrics are calculated using a 5-fold cross validation test. Our method thus sets up a framework for effectively screening binding affinity change with unknown single and multiple amino-acid changes. This can be a very valuable tool to predict host adaptation and zoonotic spillover of current and future SARS-CoV-2 variants.

Contains fulltext : 238919.pdf (Publisher’s version ) (Closed access) In the sphere of liver tissue engineering (LTE), 3D bioprinting has emerged as an effective technology to mimic the complex in vivo hepatic microenvironment, enabling the development of functional 3D constructs with potential application in the healthcare and diagnostic sector. This review gears off with a note on the liver's microscopic 3D architecture and pathologies linked to liver injury. The write-up is then directed towards unmasking recent advancements and prospects of bioprinting for recapitulating 3D hepatic structure and function. The article further introduces available stem cell opportunities and different strategies for their directed differentiation towards various hepatic stem cell types, including hepatocytes, hepatic sinusoidal endothelial cells, stellate cells, and Kupffer cells. Another thrust of the article is on understanding the dynamic interplay of different hepatic cells with various microenvironmental cues, which is crucial for controlling differentiation, maturation, and maintenance of functional hepatic cell phenotype. On a concluding note, various critical issues and future research direction towards clinical translation of bioprinted hepatic constructs are discussed.

Conventional top-down approaches in tissue engineering involving cell seeding on scaffolds have been widely used in bone engineering applications. However, scaffold-based bone tissue constructs have had limited clinical translation due to constrains in supporting scaffolds, minimal flexibility in tuning scaffold degradation, and low achievable cell seeding density as compared with native bone tissue. Here, we demonstrate a pragmatic and scalable bottom-up method, inspired from embryonic developmental biology, to build three-dimensional (3D) scaffold-free constructs using spheroids as building blocks. Human umbilical vein endothelial cells (HUVECs) were introduced to human mesenchymal stem cells (hMSCs) (hMSC/HUVEC) and spheroids were fabricated by an aggregate culture system. Bone tissue was generated by induction of osteogenic differentiation in hMSC/HUVEC spheroids for 10 days, with enhanced osteogenic differentiation and cell viability in the core of the spheroids compared to hMSC-only spheroids. Aspiration-assisted bioprinting (AAB) is a new bioprinting technique which allows precise positioning of spheroids (11% with respect to the spheroid diameter) by employing aspiration to lift individual spheroids and bioprint them onto a hydrogel. AAB facilitated bioprinting of scaffold-free bone tissue constructs using the pre-differentiated hMSC/HUVEC spheroids. These constructs demonstrated negligible changes in their shape for two days after bioprinting owing to the reduced proliferative potential of differentiated stem cells. Bioprinted bone tissues showed interconnectivity with actin-filament formation and high expression of osteogenic and endothelial-specific gene factors. This study thus presents a viable approach for 3D bioprinting of complex-shaped geometries using spheroids as building blocks, which can be used for various applications including but not limited to, tissue engineering, organ-on-a-chip and microfluidic devices, drug screening and, disease modeling.

With an increasing life expectancy and aging population, orthopedic defects and bone graft surgeries are increasing in global prevalence. Research to date has greatly advanced the understanding of bone biology and defect repair mechanism, leading to a marked success in the development of synthetic bone substitutes. Yet, the quest for a functionalized bone grafts prompted the researchers to pursue a viable and safer alternative that regulates cellular activity, and supports bone regeneration and healing process without causing serious side-effects and tissue toxicity. In this context, researchers have found a novel treatment regimen by introducing naturally derived medicinal compounds (NMSs) in bone tissue engineering scaffold that enables them to release at a desirable rate and concentration, maintains a sustained release allowing sufficient time for tissue in-growth, and guides bone regeneration process with minimized risk of tissue toxicity. NMCs are gaining popularity in western countries for the last two decades and is now being used by 80% of the population worldwide, according to an estimation by WHO. In contrast to synthetic drugs, NMCs have a broader range of safety window and thus presented as suitable for prolonged localized delivery for bone tissue regeneration. There is limited literature focusing on the integration of bone grafts and natural medicines that provides detailed scientific evidences on each NMCs, their toxic limits and particular application in bone tissue engineering, which could guide the researchers to develop functionalized implants for various bone disorders. This review will discuss the emerging trend of NMC drug delivery from tissue engineering scaffold, including both 3D printed structures and surface modified implants, highlighting the significance and potential of NMCs for bone health, guiding future paths toward the development of an ideal bone tissue engineering scaffold.

Calcium phosphate materials are widely used as bone-like scaffolds or coating for metallic hip and knee implants due to their excellent biocompatibility, compositional similarity to natural bone and controllable bioresorbability. Local delivery of drugs or osteogenic factors from scaffolds and implants are required over a desired period of time for an effectual treatment of various musculoskeletal disorders. Curcumin, an antioxidant and anti-inflammatory molecule, enhances osteoblastc activity in addition to its anti-osteoclastic activity. However, due to its poor solubility and high intestinal liver metabolism, it showed limited oral efficacy in various preclinical and clinical studies. To enhance its bioavailability and to provide higher release, we have used poly (e-caprolactone) (PCL), poly ethylene glycol (PEG) and poly lactide co glycolide (PLGA) as the polymeric system to enable continuous release of curcumin from the hydroxyapatite matrix for 22 days. Additionally, curcumin was incorporated in plasma sprayed hydroxyapatite coated Ti6Al4V substrate to study in vitro cell material interaction using human fetal osteoblast (hFOB) cells for load bearing implants. MTT cell viability assay and morphological characterization by FESEM showed highest cell viability with samples coated with curcumin-PCL-PEG. Finally, 3D printed interconnected macro porous β-TCP scaffolds were prepared and curcumin-PCL-PEG was loaded to assess the effects of curcumin on in vivo bone regeneration. The presence of curcumin in TCP results in enhanced bone formation after 6 weeks. Complete mineralized bone formation increased from 29.6 % to 44.9% in curcumin-coated scaffolds compared to pure TCP. Results show that local release of curcumin can be designed for both load bearing or non-load bearing implants with the aid of polymers, which can be considered an excellent candidate for wound healing and tissue regeneration applications in bone tissue engineering.

Calcium phosphate (CaP) ceramics show significant promise towards bone graft applications because of the compositional similarity to inorganic materials of bone. With 3D printing, it is possible to create ceramic implants that closely mimic the geometry of human bone and can be custom-designed for unusual injuries or anatomical sites. The objective of the study was to optimize the 3D-printing parameters for the fabrication of scaffolds, with complex geometry, made from synthesized tricalcium phosphate (TCP) powder. This study was also intended to elucidate the mechanical and biological effects of the addition of Fe(+3) and Si(+4) in TCP implants in a rat distal femur model for 4, 8, and 12 weeks. Doped with Fe(+3) and Si(+4) TCP scaffolds with 3D interconnected channels were fabricated to provide channels for micronutrients delivery and improved cell-material interactions through bioactive fixation. Addition of Fe(+3) into TCP enhanced early-stage new bone formation by increasing type I collagen production. Neovascularization was observed in the Si(+4) doped samples after 12 weeks. These findings emphasize that the additive manufacturing of scaffolds with complex geometry from synthesized ceramic powder with modified chemistry is feasible and may serve as a potential candidate to introduce angiogenic and osteogenic properties to CaPs, leading to accelerated bone defect healing.

This study aims to improve the interfacial bonding between the osseous host tissue and the implant surface through the application of doped calcium phosphate (CaP) coating on 3D printed porous titanium. Porous titanium (Ti) cylinders with 25% volume porosity were fabricated using Laser Engineered Net Shaping (LENS™), a commercial 3D printing technique. The surface of these 3D printed cylinders was modified by growing TiO2 nanotubes first, followed by a coating with Sr2+ and Si4+ doped bioactive CaP ceramic in simulated body fluid (SBF). Doped CaP coated implants were hypothesized to show enhanced early stage bone tissue integration. Biological properties of these implants were investigated in vivo using a rat distal femur model after 4 and 10 weeks. CaP coated porous Ti implants have enhanced tissue ingrowth as was evident from the CT scan analysis, push out test results, and the histological analysis compared to porous implants with or without surface modification via titania nanotubes. Increased osteoid-like new bone formation and accelerated mineralization were revealed inside the CaP coated porous implants. It is envisioned that such an approach of adding a bioactive doped CaP layer on porous Ti surface can reduce healing time by enhancing early stage osseointegration in vivo. Keywords: 3D printing, Porous cylinders, Surface modification, Titania nanotubes, in vivo osseointegration, Accelerated healing

This study intends to analyze the effects of doxorubicin and sodium bicarbonate release with polycaprolactone (PCL) coating on calcium phosphate system which is a bone like material, on the cell viability and proliferation of osteosarcoma and osteoblast. Increased systematic pH concentrations locally by the release of sodium bicarbonate diminished acidosis and hence, alleviated malignancy. In our studies, we have shown that the same of dosage of doxorubicin inhibited both osteoblast and osteosarcoma cell attachment and viability whereas, sodium bicarbonate abated osteosarcoma cell proliferation. Sodium bicarbonate also inhibited osteoblast cell proliferation in the early time points, however, the cell viability increased after the initial burst release of the molecule. Polymer coating on calcium phosphate-based implants, as carriers of drug, can minimize chances of toxic effects of higher oral drug dosage in the body, and also help in delivering effective doses of drugs, locally to the target tissues, as compared to the oral drug delivery approach. A coating of PCL was thus incorporated to control the initial burst release of bicarbonate, which enhanced the osteoblast cell viability, but was capable of diminishing osteosarcoma cell proliferation. The novelty and clinical significance of this study lies in the understanding of unique delivery using encapsulated naturally occurring and more benign sodium bicarbonate, for usage after excision of the cancerous bone, without any adverse effects on normal bone cells.

Conventional top-down approaches in tissue engineering involving cell seeding on scaffolds have been widely used in bone engineering applications. However, scaffold-based bone tissue constructs have had limited clinical translation due to constrains in supporting scaffolds, minimal flexibility in tuning scaffold degradation, and low achievable cell seeding density as compared with native bone tissue. Here, we demonstrate a pragmatic and scalable bottom-up method, inspired from embryonic developmental biology, to build three-dimensional (3D) scaffold-free constructs using spheroids as building blocks. Human umbilical vein endothelial cells (HUVECs) were introduced to human mesenchymal stem cells (hMSCs) (hMSC/HUVEC) and spheroids were fabricated by an aggregate culture system. Bone tissue was generated by induction of osteogenic differentiation in hMSC/HUVEC spheroids for 10 d, with enhanced osteogenic differentiation and cell viability in the core of the spheroids compared to hMSC-only spheroids. Aspiration-assisted bioprinting (AAB) is a new bioprinting technique which allows precise positioning of spheroids (11% with respect to the spheroid diameter) by employing aspiration to lift individual spheroids and bioprint them onto a hydrogel. AAB facilitated bioprinting of scaffold-free bone tissue constructs using the pre-differentiated hMSC/HUVEC spheroids. These constructs demonstrated negligible changes in their shape for two days after bioprinting owing to the reduced proliferative potential of differentiated stem cells. Bioprinted bone tissues showed interconnectivity with actin-filament formation and high expression of osteogenic and endothelial-specific gene factors. This study thus presents a viable approach for 3D bioprinting of complex-shaped geometries using spheroids as building blocks, which can be used for various applications including but not limited to, tissue engineering, organ-on-a-chip and microfluidic devices, drug screening and, disease modeling.

Applications of porous metallic implants to enhance osseointegration of load-bearing implants are increasing. In this work, porous titanium implants, with 25 volume% porosity, were manufactured using Laser Engineered Net Shaping (LENS™) to measure the influence of porosity towards bone tissue integration in vivo. Surfaces of the LENS™ processed porous Ti implants were further modified with TiO2 nanotubes to improve cytocompatibility of these implants. We hypothesized that interconnected porosity created via additive manufacturing will enhance bone tissue integration in vivo. To test our hypothesis, in vivo experiments using a distal femur model of male Sprague-Dawley rats were performed for a period of 4 and 10 weeks. In vivo samples were characterized via micro-computed tomography (CT), histological imaging, scanning electron microscopy, and mechanical push-out tests. Our results indicate that porosity played an important role to establish early stage osseointegration forming strong interfacial bonding between the porous implants and the surrounding tissue, with or without surface modification, compared to dense Ti implants used as a control.

For decades, research has been attributed to the monoculture of either mesenchymal stem cells (MSCs) or monocytes to differentiate into osteoblasts (OBs) and osteoclasts (OCs) respectively, however, this is far from being realistic. For improved research in the field of biomaterials, the balance between OBs and OCs needs to be investigated simultaneously on in vitro models for a better understanding and prediction of the bone remodeling process in vivo. The study aims to investigate the effects of Mg+2 and Sr+2 dopant in hydroxyapatite coating on the simultaneous differentiation of human MSCs and Tamm Horsfall Protein 1 (THP-1) monocytes into OBs and OCs respectively. We hypothesize that a cultivation regime can be established to show simultaneous proliferation and differentiation of the MSCs and monocytes into OBs and OCs. Also, the presence of Sr+2 and Mg+2 will induce faster bone remodeling and demonstrate enhanced osteogenic properties. Doped hydroxyapatite coatings were fabricated on CpTi substrates using plasma spray coating technique and the influence of dopants on the in vitro OB−OC co-culture was studied by specific marker genes, namely OPG, RANKL, RUNX2, and ACP5. Comparison amongst the expressions of genes reveals the differentiation of the primary cells as early as 5-day time-point. Downregulation of RUNX2 and ACP5 in the doped HA coated samples at 15-day time-point are a proof of the effective role of the dopants in the enhancement of bone remodeling. This study shows the possibility of simultaneous culturing of human OB and OC precursors and demonstrates the efficacy of dopants in the pace change of bone remodeling for bone tissue engineering applications.

In this study, the effects of 3D-printed SiO2 and ZnO-doped tricalcium phosphate (TCP) scaffolds with interconnected pores were evaluated on the in vivo bone formation and healing properties of a rabbit tibial defect model. Pure and doped TCP scaffolds were fabricated by a ceramic powder-based 3D printing technique and implanted into critical sized rabbit tibial defects for up to 4 months. In vivo bone regeneration was evaluated using chronological radiological examination, histological evaluations, SEM micrographs, and fluorochrome labeling studies. Radiograph results showed that Si/Zn-doped samples had slower degradation kinetics than the pure TCP samples. 3D printing of TCP scaffolds improved bone formation. The addition of dopants in the TCP scaffolds improved osteogenic capabilities when compared to the pure scaffolds. In summary, our findings indicate that the addition of dopants to the TCP scaffolds enhanced bone formation and in turn leading to accelerated healing.

The idea behind this introductory chapter is to help the reader to get a brief overview of different biomaterials, devices, and their applications in various treatment options toward bone disorders. It is written in a language that can be understood by most researchers even if they do not have much of a background in materials science or bone biology. The biomaterials field is very dynamic, interdisciplinary, and almost every day some forms of new discoveries are being made by researchers around the world. However, our aim toward this chapter was to present materials that are more mature and have seen the light of clinical success. We have briefly discussed both synthetic and natural materials used in the fields of orthopedics and dentistry. We have highlighted some of their advantages as well as potential concerns. Finally, a brief narrative is presented emphasizing clinical applications of different biomaterials.