Bioactive glasses and glass‐ceramics versus hydroxyapatite: Comparison of angiogenic potential and biological responsiveness

Synthesis and evaluation of nanosystem containing chondroitinase ABCI based on hydroxyapatite

The bacterial enzyme chondroitinase ABCI (chABCI), which has been isolated from Proteus Vulgaris, is crucial in the treatment of spinal cord injuries. However, due to its short lifespan, the maintenance and clinical application of this enzyme are very constrained. In this study, the immobilization of this enzyme on hydroxyapatite has been carried out and assessed with the aim of enhancing the characteristics and efficiency of chABCI. Hydroxyapatite particles (HAPs) are a potential candidate for drug-delivery carriers because of their excellent biocompatibility, shape controllability, and high adsorption. The use of the nanometer scale allows efficient access to the enzyme's substrate. It demonstrates important biological application capabilities in this way. Field emission gun-scanning electron microscopy (FEG-SEM), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), in vitro release study, and cytotoxicity test were used to characterize the drug nanosystem's properties. According to the findings, electrostatic bindings was formed between charged groups of the enzyme and hydroxyapatite nanoparticles. The results also demonstrated that immobilized chABCI on hydroxyapatite has beneficial properties, such as more manageable drug release, minimal toxicity and side effects, and a high potential to enhance the efficacy of drug delivery and decrease the need for repeated injections.

Composite PLGA–Nanobioceramic Coating on Moxifloxacin-Loaded Akermanite 3D Porous Scaffolds for Bone Tissue Regeneration

Silica-based ceramics doped with calcium and magnesium have been proposed as suitable materials for scaffold fabrication. Akermanite (Ca2MgSi2O7) has attracted interest for bone regeneration due to its controllable biodegradation rate, improved mechanical properties, and high apatite-forming ability. Despite the profound advantages, ceramic scaffolds provide weak fracture resistance. The use of synthetic biopolymers such as poly(lactic-co-glycolic acid) (PLGA) as coating materials improves the mechanical performance of ceramic scaffolds and tailors their degradation rate. Moxifloxacin (MOX) is an antibiotic with antimicrobial activity against numerous aerobic and anaerobic bacteria. In this study, silica-based nanoparticles (NPs) enriched with calcium and magnesium, as well as copper and strontium ions that induce angiogenesis and osteogenesis, respectively, were incorporated into the PLGA coating. The aim was to produce composite akermanite/PLGA/NPs/MOX-loaded scaffolds through the foam replica technique combined with the sol–gel method to improve the overall effectiveness towards bone regeneration. The structural and physicochemical characterizations were evaluated. Their mechanical properties, apatite forming ability, degradation, pharmacokinetics, and hemocompatibility were also investigated. The addition of NPs improved the compressive strength, hemocompatibility, and in vitro degradation of the composite scaffolds, resulting in them keeping a 3D porous structure and a more prolonged release profile of MOX that makes them promising for bone regeneration applications.

Osteogenic and Angiogenic Potency of VEGF165-Transfected Canine Bone Marrow Mesenchymal Cells Combined with Coral Hydroxyapatite in Vitro

BACKGROUND

To explore the osteogenic and angiogenic potential of human vascular endothelial growth factor 165 (hVEGF165) gene-transfected canine bone marrow mesenchymal stem cells (BMSCs) combined with coral hydroxyapatite (CHA) scaffold.

METHODS

We constructed a lentiviral vector and transfected canine BMSCs with the best multiplicity of infection. Osteogenesis was induced in the transfected groups (GFP-BMSCs group and hVEGF-BMSCs group) and non-transfected group (BMSCs group), followed by the evaluation of alkaline phosphatase (ALP) activity and alizarin red S staining. Cells from the three groups were co-cultured with CHA granules, respectively to obtain the tissue-engineered bone. MTT assay and fluorescence microscopy were employed to assess cell proliferation and adhesion. The expression of osteogenic and angiogenic related genes and proteins were evaluated at 7, 14, 21, and 28 days post osteoinduction in cell culture alone and cell co-culture with CHA, respectively using RT-PCR and ELISA.

RESULTS

The hVEGF165 gene was transfected into BMSCs successfully. Higher ALP activity and more calcified nodules were found in the hVEGF-BMSCs group than in the control groups (p < 0.001). Cells attached and proliferated in CHA particles. Both cells cultured alone and cells co-culture with CHA expressed more osteogenic and angiogenic related genes and proteins in the hVEGF-BMSCs group compared to the GFP-BMSCs and BMSCs groups (p < 0.05).

CONCLUSION

High expression of hVEGF165 in BMSCs potentially promote the osteogenic potential of BMSCs, and synergically drive the expression of other osteogenic and angiogenic factors. hVEGF-BMSCs co-cultured with CHA expressed more osteogenic and angiogenic related factors, creating a favorable microenvironment for osteogenesis and angiogenesis. Also, the findings have allowed for the construction of a CHA-hVEGF-BMSCs tissue-engineered bone.

Improvement of Drug-Loading Properties of Hydroxyapatite Particles Using Triethylamine as a Capping Agent: A Novel Approach

Particles that modify delivery characteristics are a focus of drug-loading research. Hydroxyapatite particles (HAPs) have excellent biocompatibility, shape controllability, and high adsorption, making them a potential candidate for drug-delivery carriers. However, there are still some defects in the current methods used to prepare HAPs. In order to avoid agglomeration and improve the drug-loading properties of HAPs, the present study provides a novel triethylamine (TEA)-capped coprecipitation template method to prepare HAPs at room temperature. In addition, pure water and anhydrous ethanol were used as solvents to investigate the capping effect of the small-molecule capping agent TEA during the synthesis of HAPs. The results showed that the HAPs prepared in the TEA ethanol system had a smaller particle size (150–250 nm), better dispersion and higher crystallinity. The results were significantly different from those of the conventional preparation methods without TEA. However, the hydroxyapatite crystal would agglomerate to a certain extent after being stored for a period of time, forming micro/nano-sized agglomerates of nanocrystals. FITR analysis and SEM observation showed that the capping effect of TEA promoted the formation of a smaller template and dispersed HAPs were quickly formed by dissolution and reprecipitation processes. The drug-loading experiments showed that the HAPs prepared in the TEA ethanol system had high drug-loading capacity (239.8 ± 13.4 mg·g−1) as well as an improved drug-release profile demonstrated in the drug-release experiment. The larger specific surface area associated with the smaller particle size was beneficial to the adsorption of drugs. After drying at 60 °C, TEA was evaporated from the HAPs which agglomerated into larger micron particles with more drug encapsulated. Thus, the effect of a sustained release was achieved. In the present research, a novel approach was developed by using triethylamine as the capping agent to prepare micro/nano-sized agglomerates of HAP nanocrystals with improved drug loading, which is predicted to have potential application in drug delivery.

Inorganic Agents for Enhanced Angiogenesis of Orthopedic Biomaterials

Aseptic loosening of a permanent prosthesis remains one of the most common reasons for bone implant failure. To improve the fixation between implant and bone tissue as well as enhance blood vessel formation, bioactive agents are incorporated into the surface of the biomaterial. This study reviews and compares five bioactive elements (copper, magnesium, silicon, strontium, and zinc) with respect to their effect on the angiogenic behavior of endothelial cells (ECs) when incorporated on the surface of biomaterials. Moreover, it provides an overview of the state-of-the-art methodologies used for the in vitro assessment of the angiogenic properties of these elements. Two databases are searched using keywords containing ECs and copper, magnesium, silicon, strontium, and zinc. After applying the defined inclusion and exclusion criteria, 59 articles are retained for the final assessment. An overview of the angiogenic properties of five bioactive elements and the methods used for assessment of their in vitro angiogenic potential is presented. The findings show that silicon and strontium can effectively enhance osseointegration through the simultaneous promotion of both angiogenesis and osteogenesis. Therefore, their integration onto the surface of biomaterials can ultimately decrease the incidence of implant failure due to aseptic loosening.

Composite Scaffolds for Bone Tissue Regeneration Based on PCL and Mg-Containing Bioactive Glasses

Simple Summary

Polycaprolactone (PCL) is a bioresorbable and biocompatible polymer that has been widely used in long-term implants. However, when it comes to regenerative medicine, PCL suffers from some shortcomings such as a slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of ceramics such as bioactive glasses into the PCL matrix has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity, which are suitable for bone tissue engineering. The use of conventional approaches (such as solvent casting and particulate leaching, phase separation, electrospinning, freeze drying, etc.) in realizing these composite scaffolds strongly affects the control of both the internal and the external architecture of scaffolds, including pore size, pore morphology, and overall structure porosity. Accordingly, 3D printing was used in this study because of the benefits offered over conventional methods, such as high flexibility in shape and size, high reproducibility, capabilities of precise control over internal architecture down to the microscale level, and a customized design that can be tailored to specific patient needs. The optimization of the scaffold structure was previously investigated in terms of architecture through the combination of the Taguchi method and CAD drawing, and, in this study, it was investigated by varying the composition of the composite material.

Abstract

Polycaprolactone (PCL) is widely used in additive manufacturing for the construction of scaffolds for tissue engineering because of its good bioresorbability, biocompatibility, and processability. Nevertheless, its use is limited by its inadequate mechanical support, slow degradation rate and the lack of bioactivity and ability to induce cell adhesion and, thus, bone tissue regeneration. In this study, we fabricated 3D PCL scaffolds reinforced with a novel Mg-doped bioactive glass (Mg-BG) characterized by good mechanical properties and biological reactivity. An optimization of the printing parameters and scaffold fabrication was performed; furthermore, an extensive microtopography characterization by scanning electron microscopy and atomic force microscopy was carried out. Nano-indentation tests accounted for the mechanical properties of the scaffolds, whereas SBF tests and cytotoxicity tests using human bone-marrow-derived mesenchymal stem cells (BM-MSCs) were performed to evaluate the bioactivity and in vitro viability. Our results showed that a 50/50 wt% of the polymer-to-glass ratio provides scaffolds with a dense and homogeneous distribution of Mg-BG particles at the surface and roughness twice that of pure PCL scaffolds. Compared to pure PCL (hardness H = 35 ± 2 MPa and Young’s elastic modulus E = 0.80 ± 0.05 GPa), the 50/50 wt% formulation showed H = 52 ± 11 MPa and E = 2.0 ± 0.2 GPa, hence, it was close to those of trabecular bone. The high level of biocompatibility, bioactivity, and cell adhesion encourages the use of the composite PCL/Mg-BG scaffolds in promoting cell viability and supporting mechanical loading in the host trabecular bone.

Evaluations of hydroxyapatite and bioactive glass in the repair of critical size bone defects in rat calvaria

To overcome the morbidity of autogenous graft removal and limitations of allogeneic and xenogeneic grafts, a great interest exists in the development of biomaterials of synthetic origin.

OBJECTIVE

The aim of this study was to evaluate the biological behavior of a novel bioactive glass (60% SiO2- 36% CaO-4% P2O5) as bone substitute in critical calvaria defects of rats, in comparison to hydroxyapatite.

METHODS

Sixty male Wistar rats were divided in three groups, according to the treatment: Control Group (C) - blood clot; Hydroxyapatite (HA) - particulate hydroxyapatite (≤0,5 mm); and Bioactive Glass (BG) - particulate bioactive glass (0.04-1 mm).

RESULTS

From the intergroup analysis, it was observed that Group C presented a greater newly formed bone area (NBA) when compared to Groups HA and BG. In addition, Group HA showed higher NBA when compared to Group BG at 30 and 60 days (P < 0.05). Immunohistochemistry revealed that groups HA and BG presented high and moderate osteocalcin immunolabeling respectively. Group HA displayed a greater number of TRAP-positive cells compared to Groups C and BG at 30 and 60 days (p < 0.05).

CONCLUSION

From these results, we can conclude that the resorption rate of hydroxyapatite is higher than the novel bioactive glass, which maintained significant higher volume until the last experimental period. Both of the tested biomaterials acted as osteoconductors during bone repair, and their physical characteristics importantly influenced this process.