On the synthesis of tailored biomimetic hydroxyapatite nanoplates through a bioinspired approach in the presence of collagen or chitosan and l-arginine

Additive manufacturing of hydroxyapatite-chitosan-genipin composite scaffolds for bone tissue engineering applications

Additive manufacturing holds promise for the fabrication of three-dimensional scaffolds with precise geometry, to serve as substrates for the guided regeneration of natural tissue. In this work, a bioinspired approach is adopted for the synthesis of hybrid hydroxyapatite hydrogels, which were subsequently printed to form 3D scaffolds for bone tissue engineering applications. These hydrogels consist of hydroxyapatite nanocrystals, biomimetically synthesized in the presence of both chitosan and l-arginine. To improve their mechanical properties, chemical crosslinking was performed using a natural crosslinking agent (genipin), and their rheology was modified by employing an acetic acid/gelatin solution. Regarding the 3D printing process, several parameters (flow, infill and perimeter speed) were studied in order to accurately produce scaffolds with predesigned geometry and micro-architecture, while also applying low printing temperature (15 °C). Following the printing procedure, the 3D scaffolds were freeze dried in order to remove the entrapped solvents and therefore, obtain a porous interconnected network. Evaluation of porosity was performed using micro-computed tomography and nanomechanical properties were assessed through nanoindentation. Results of both characterization techniques, showed that the scaffolds' porosity as well as their modulus values, fall within the corresponding range of the respective values of cancellous bone. The biocompatibility of the 3D printed scaffolds was assessed using MG63 human osteosarcoma cells for 7 days of culturing. Cell viability was evaluated by MTT assay as well as double staining and visualized under fluorescence microscopy, while cell morphology was analyzed through scanning electron microscopy. Biocompatibility tests, revealed that the scaffolds constitute a cell-friendly environment, allowed them to adhere on the scaffolds' surface, increase their population and maintain high levels of viability.

Mechanical Enhancement of Cytocompatible 3D Scaffolds, Consisting of Hydroxyapatite Nanocrystals and Natural Biomolecules, Through Physical Cross-Linking

Bioinspired scaffolds mimicking natural bone-tissue properties holds great promise in tissue engineering applications towards bone regeneration. Within this work, a way to reinforce mechanical behavior of bioinspired bone scaffolds was examined by applying a physical crosslinking method. Scaffolds consisted of hydroxyapatite nanocrystals, biomimetically synthesized in the presence of collagen and l-arginine. Scaffolds were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), microcomputed tomography, and nanoindentation. Results revealed scaffolds with bone-like nanostructure and composition, thus an inherent enhanced cytocompatibility. Evaluation of porosity proved the development of interconnected porous network with bimodal pore size distribution. Mechanical reinforcement was achieved through physical crosslinking with riboflavin irradiation, and nanoindentation tests indicated that within the experimental conditions of 45% humidity and 37 °C, photo-crosslinking led to an increase in the scaffold’s mechanical properties. Elastic modulus and hardness were augmented, and specifically elastic modulus values were doubled, approaching equivalent values of trabecular bone. Cytocompatibility of the scaffolds was assessed using MG63 human osteosarcoma cells. Cell viability was evaluated by double staining and MTT assay, while attachment and morphology were investigated by SEM. The results suggested that scaffolds provided a cell friendly environment with high levels of viability, thus supporting cell attachment, spreading and proliferation.

The Significance and Utilisation of Biomimetic and Bioinspired Strategies in the Field of Biomedical Material Engineering: The Case of Calcium Phosphat-Protein Template Constructs

This review provides a summary of recent research on biomimetic and bioinspired strategies applied in the field of biomedical material engineering and focusing particularly on calcium phosphate-protein template constructs inspired by biomineralisation. A description of and discussion on the biomineralisation process is followed by a general summary of the application of the biomimetic and bioinspired strategies in the fields of biomedical material engineering and regenerative medicine. Particular attention is devoted to the description of individual peptides and proteins that serve as templates for the biomimetic mineralisation of calcium phosphate. Moreover, the review also presents a description of smart devices including delivery systems and constructs with specific functions. The paper concludes with a summary of and discussion on potential future developments in this field.

S. N. SN, Lakshmipathy M, Sagadevan S, Mohammad F, Al-Lohedan HA, Paiman S, Oh WC. Nanoformulations of core–shell type hydroxyapatite-coated gum acacia with enhanced bioactivity and controlled drug delivery for biomedical applications

In this work, nanospherical hydroxyapatite (HAP) was prepared that has combined properties of controlled drug delivery, biocompatibility, and antibacterial activity to have applications in the biomedical sector.

Preparation, characterization and antibacterial properties of 6-deoxy-6-arginine modified chitosan

In this study, 6-deoxy-6-arginine modified chitosan (DAC), was synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and elemental analysis. The arginine was grafted onto C6 groups of chitosan. Antibacterial activity of DAC against gram-negative bacteria Escherichia coli (E. coli) and gram-positive bacteria Staphylococcus aureus (S. aureus) were investigated at concentration between 0.02 mg/mL and 10 mg/mL. Cell viability assessment was estimated in vitro with Caco-2 and L929 cells. Water solubility of DAC at different pH was also evaluated. The results showed that the minimum inhibitory concentration (MICs) of DAC against S. aureus and E. coli were 0.078 mg/mL and 0.312 mg/mL, respectively. The minimum bactericidal concentration (MBC) against S. aureus and E. coli was 0.625 mg/mL. The cytotoxicity of chitosan and DAC was not significantly different. It demonstrated that DAC might be a potential safe antibacterial agent.

Drug Leaching Properties of Vancomycin Loaded Mesoporous Hydroxyapatite as Bone Substitutes

Infections after bone reconstructive surgery become an authentic therapeutic and economic issue when it comes to a modern health care system. In general; infected bone defects are regarded as contraindications for bone grafting. Since the pathogens develop a biofilm on the inner surface of the bone; local delivery of antibiotics becomes more important. The present work focuses on the synthesis of Mesoporous Hydroxyapatite (MPHAP) loaded with drug Vancomycin (Van) and to investigate its loading and leaching ability in phosphate buffer solution (PBS), to be used for post-operative infections. The effect of pore size on MPHAP was analyzed using different fatty acids as organic modifiers. The impacts of various fatty acids chain length on the morphology and pore size were studied. A simple impregnation technique with optimized conditions ensured a high antibiotic loading (up to 0.476 + 0.0135 mg/mL), with a complete in vitro release obtained within 50 h.

A Biomimetic Alternative to Synthetic Hydroxyapatite: "Boron-Containing Bone-Like Hydroxyapatite" Precipitated From Simulated Body Fluid

BACKGROUND

Biological hydroxyapatite (HA), has several mechanical and physical advantages over the commercially available synthetic apatite (CAP-HA). The aim of this in vivo study was to investigate the effect of osteoinductive "bone-like hydroxyapatite" obtained from simulated body fluid (SBF) combined with osteoinductive "boron" (B) on bone healing.

MATERIALS

Bone like nanohydroxyapatite (SBF-HA) was precipitated from 10× simulated body fluid (10×SBF). Thirty Sprague-Dawley rats were randomly divided into 5 experimental groups (n = 6 each). The groups were involving blank defect, chitosan, SBF-HA, SBF-HA/B, and CAP-HA. Two biparietal round critical sized bone defect was created using a dental burr. The rats were sacrificed respectively at the end of second and fourth months after surgery and their calvarium were harvested for further macroscopic, microtomographic, and histologic evaluation.

RESULTS

The SBF-HA/B group demonstrated the highest mineralized matrix formation rates (30.69 ± 3.73 for the second month, 62.68 ± 7.03 for the fourth month) and was significantly higher than SBF-HA and the CAP-HA groups. The SBF-HA/B group demonstrated the highest mineralized matrix formation rates (30.69 ± 3.73 for the second month, 62.68 ± 7.03 for the fourth month) and was significantly higher than SBF-HA and the CAP-HA groups. In means of bone defect repair histologically, the highest result was observed in the SBF-HA/B group (P < 0.001).

CONCLUSIONS

The "bone-like hydroxapatite" obtained from simulated body fluid is worth attention when both its beneficial effects on bone healing and its biological behavior is taken in consideration for further bone tissue engineering studies. It appears to be a potential alternative to the commercially available hydroxyapatite samples.

Synthesis of protein/hydroxyapatite nano-composites by a high-gravity co-precipitation method

A high-gravity co-precipitation strategy was introduced to the fabrication of protein/hydroxyapatite nano-composites with improved protein adsorption efficiencies and enhanced biocompatibilities.