Enhanced BMP-2-Mediated Bone Repair Using an Anisotropic Silk Fibroin Scaffold Coated with Bone-like Apatite

The repair of large bone defects remains challenging and often requires graft material due to limited availability of autologous bone. In clinical settings, collagen sponges loaded with excessive amounts of bone morphogenetic protein 2 (rhBMP-2) are occasionally used for the treatment of bone non-unions, increasing the risk of adverse events. Therefore, strategies to reduce rhBMP-2 dosage are desirable. Silk scaffolds show great promise due to their favorable biocompatibility and their utility for various biofabrication methods. For this study, we generated silk scaffolds with axially aligned pores, which were subsequently treated with 10× simulated body fluid (SBF) to generate an apatitic calcium phosphate coating. Using a rat femoral critical sized defect model (CSD) we evaluated if the resulting scaffold allows the reduction of BMP-2 dosage to promote efficient bone repair by providing appropriate guidance cues. Highly porous, anisotropic silk scaffolds were produced, demonstrating good cytocompatibility in vitro and treatment with 10× SBF resulted in efficient surface coating. In vivo, the coated silk scaffolds loaded with a low dose of rhBMP-2 demonstrated significantly improved bone regeneration when compared to the unmineralized scaffold. Overall, our findings show that this simple and cost-efficient technique yields scaffolds that enhance rhBMP-2 mediated bone healing.

Evaluation of Corrosion Behavior and In Vitro of Strontium-Doped Calcium Phosphate Coating on Magnesium

This study investigated the biocompatibility of strontium-doped calcium phosphate (Sr-CaP) coatings on pure magnesium (Mg) surfaces for bone applications. Sr-CaP coated specimens were obtained by chemical immersion method on biodegradable magnesium. In this study, Sr-CaP coated magnesium was obtained by immersing pure magnesium in a solution containing Sr-CaP at 80 °C for 3 h. The corrosion resistance and biocompatibility of magnesium according to the content of Sr-CaP coated on the magnesium surface were evaluated. As a result, the corrosion resistance of Sr-CaP coated magnesium was improved compared to pure magnesium. In addition, it was confirmed that the biocompatibility of the group containing Sr was increased. Thus, the Ca-SrP coating with a reduced degradation and improved biocompatibility could be used in Mg-based orthopedic implant applications.

Highly efficient biphasic calcium-phosphate coating procedure with an enhanced coating yield and protein incorporation rate

A biphasic calcium-phosphate (CaP)-coating is a promising surface modification for functionalizing various endosseous biomaterials. However, its biomedical application is limited by its low coating yield and incorporation inefficiency. We developed a highly concentrated (4.5×) supersaturated calcium-phosphate solution (SCPS) and compared its physicochemical properties with those of 1× SCPS. One milliliter of 4.5× SCPS formed a thick (110 μm) continuous coating on a titanium disc (4×4×1 mm), compared to the thin (29 μm) 1× SCPScoating. On X-ray diffraction analysis, the 4.5× SCPS-coating had characteristic dicalcium-phosphate dehydrate and apatite peaks, in contrast to the apatite-only of 1× SCPS-coating. Under acidic condition (pH 4.5), the 4. × 5SCPS-coating released significantly less Ca2+ than the 1× SCPS-coating. FITC-bovine serum albumin incorporation in the 4.5× SCPS-coating (81.20±6.42%) was significantly higher than in the 1× SCPS-coating (21.86±1.90%). Thus, this modified coating procedure holds promise for biomedical applications.

Biomimetic Strontium Substituted Calcium Phosphate Coating for Bone Regeneration

Cellulose acetate (CA)/strontium phosphate (SrP) hybrid coating has been proposed as an effective strategy to build up novel bone-like structures for bone healing since CA is soluble in most organic solvents. Strontium (Sr2+) has been reported as a potential agent to treat degenerative bone diseases due to its osteopromotive and antibacterial effects. Herein, bioactive hybrid composite SrP-based coatings (CASrP) were successfully produced for the first time. CASrP was synthesized via a modified biomimetic method (for 7—CA7dSrP, and 14 days—CA14dSrP), in which the metal ion Sr2+ was used in place of Ca2+ in the simulated body fluid. Energy-dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the SrP incorporation chemically in the CASrP samples. Atomic absorption spectroscopy (AAS) supported EDX data, showing Sr2+ adsorption into CA, and its significant increase with the augmentation of time of treatment (ca. 92%—CA7dSrP and 96%—CA14dSrP). An increment in coating porosity and the formation of SrP crystals were evidenced by scanning electron microscopy (SEM) images. X-ray diffraction (XRD) evidenced a greater crystallinity than CA membranes and a destabilization of CA14dSrP structure compared to CA7dSrP. The composites were extremely biocompatible for fibroblast and osteoblast cells. Cell viability (%) was higher either for CA7dSrP (48 h: ca. 92% and 115%) and CA14dSrP (48 h: ca. 88% and 107%) compared to CA (48 h: ca. 70% and 51%) due to SrP formation and Sr2+ presence in its optimal dose in the culture media (4.6–9 mg·L−1). In conclusion, the findings elucidated here evidence the remarkable potential of CA7dSrP and CA14dSrP as bioactive coatings on the development of implant devices for inducing bone regeneration.

Amorphous–Crystalline Calcium Phosphate Coating Promotes In Vitro Growth of Tumor-Derived Jurkat T Cells Activated by Anti-CD2/CD3/CD28 Antibodies

A modern trend in traumatology, orthopedics, and implantology is the development of materials and coatings with an amorphous–crystalline structure that exhibits excellent biocopatibility. The structure and physico–chemical and biological properties of calcium phosphate (CaP) coatings deposited on Ti plates using the micro-arc oxidation (MAO) method under different voltages (200, 250, and 300 V) were studied. Amorphous, nanocrystalline, and microcrystalline statesof CaHPO4 and β-Ca2P2O7were observed in the coatings using TEM and XRD. The increase in MAO voltage resulted in augmentation of the surface roughness Ra from 2.5 to 6.5 µm, mass from 10 to 25 mg, thickness from 50 to 105 µm, and Ca/P ratio from 0.3 to 0.6. The electrical potential (EP) of the CaP coatings changed from −456 to −535 mV, while the zeta potential (ZP) decreased from −53 to −40 mV following an increase in the values of the MAO voltage. Numerous correlations of physical and chemical indices of CaP coatings were estimated. A decrease in the ZP magnitudes of CaP coatings deposited at 200–250 V was strongly associated with elevated hTERT expression in tumor-derived Jurkat T cells preliminarily activated with anti-CD2/CD3/CD28 antibodies and then contacted in vitro with CaP-coated samples for 14 days. In turn, in vitro survival of CD4+ subsets was enhanced, with proinflammatory cytokine secretion of activated Jurkat T cells. Thus, the applied MAO voltage allowed the regulation of the physicochemical properties of amorphous–crystalline CaP-coatings on Ti substrates to a certain extent. This method may be used as a technological mechanism to trigger the behavior of cells through contact with micro-arc CaP coatings. The possible role of negative ZP and Ca2+ as effectors of the biological effects of amorphous–crystalline CaP coatings is discussed. Micro-arc CaP coatings should be carefully tested to determine their suitability for use in patients with chronic lymphoid malignancies.

Systematic Review and Meta-Analysis of the Effectiveness of Calcium-Phosphate Coating on the Osseointegration of Titanium Implants

Ca-P coatings on Ti implants have demonstrated good osseointegration capability due to their similarity to bone mineral matter. Three databases (PubMed, Embase, and Web of Science) were searched electronically in February 2021 for preclinical studies in unmodified experimental animals, with at least four weeks of follow-up, measuring bone-to-implant contact (BIC). Although 107 studies were found in the initial search, only eight experimental preclinical studies were included. Adverse events were selected by two independent investigators. The risk of bias assessment of the selected studies was evaluated using the Cochrane Collaboration Tool. Finally, a meta-analysis of the results found no statistical significance between implants coated with Ca-P and implants with etched conventional surfaces (difference of means, random effects: 5.40; 99% CI: −5.85, 16.65). With the limitations of the present review, Ca-P-coated Ti surfaces have similar osseointegration performance to conventional etched surfaces. Future well-designed studies with large samples are required to confirm our findings.