Vignesh Muthuvijayan

In recent years, there has been an increasing focus on inorganic nanomaterials for various applications, such as catalysis, thermal energy storage, biomedical imaging, drug delivery, and tissue engineering. Amongst these, Mesoporous Silica Nanoparticles (MSNs) possess an orderly mesoporous structure, large surface area, and pore volume. Hence, MSNs have shown tremendous potential for drug delivery and tissue engineering. In this work, we have studied the potential of pure MSNs for bone tissue engineering applications. Our results show that MSNs were successfully synthesized using a modified sol-gel method. ATR-FTIR spectra, powder XRD pattern, and thermogravimetric analysis confirmed the physicochemical nature of the MSNs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal the orderly arrangement and size of the mesoporous structure. In vitro cytotoxicity assays performed using NIH/3T3 fibroblast cells and MG-63 osteosarcoma cells show the cytocompatibility of the synthesized pure MSNs. Furthermore, we confirmed the biocompatibility of the MSNs using in vivo zebrafish toxicity studies. Our results show that MSNs were biocompatible at concentrations as high as 1 mg/ml. Osteogenic activity of the synthesized MSNs were evaluated using alkaline phosphatase (ALP) activity and real-time PCR analysis for the period of 7 days. ALP activity and expression of the osteocalcin gene were significantly higher in the presence of MSNs. Alizarin Red S staining also confirmed the increased calcium mineral deposition in the presence of MSNs. The MSNs showed highest osteogenic activity at 1 mg/ml concentration. Using the chick chorioallantoic membrane assay, we have also shown that the MSNs exhibit proangiogenic activity. Our results show that in the presence of 1 mg/ml MSNs, the number of blood vessels was 3 to 4-fold higher than the control. Based on the in vitro and in vivo biocompatibility, osteogenic and proangiogenic activities, it is evident that these MSNs can serve as an ideal new generation biomaterial that can aid in vascularized bone formation.

Synthetic bone grafts are being developed to overcome the limitations of conventional treatments for bone defects. In this study, we have fabricated bioactive binary and novel ternary interpenetrating polymer network (IPN) scaffolds using a combination of natural and synthetic polymers. The binary IPN scaffolds were prepared using Konjac glucomannan (KGM) and polyvinyl alcohol (PVA). In the novel ternary IPN scaffolds, polycaprolactone (PCL) was added to PVA and KGM. SEM images showed that these scaffolds were microporous with good interconnectivity. Compression testing confirmed that both the scaffolds are mechanically strong, with the ternary scaffolds having moduli comparable to the natural bone. In vitro cytocompatibility studies performed with NIH/3T3 fibroblasts cells and MG-63 osteosarcoma cells demonstrated the non-toxic and osseointegrating nature of the scaffolds. Confocal images confirmed that the cells migrated into the interconnected pores of the scaffolds. RT-PCR analysis showed that both binary and ternary scaffolds enhanced the expression of the major bone marker genes, viz., ALP, BMP-2, COLLAGEN-1, and OSTEOCALCIN. However, the expression of these osteogenic markers was significantly enhanced in the ternary scaffolds compared to the binary scaffolds. In vivo chick chorioallantoic membrane (CAM) assay shows that these scaffolds possess excellent pro-angiogenic properties. Hence, these desirable biological properties, coupled with the suitable physicochemical properties, make these IPN scaffolds ideal for treating bone defects.