EFFECTS OF ELEMENT-DOPED NANOPARTICLES IN BONE TISSUE ENGINEERING APPLICATIONS

Abstract

Chitosan/gelatin scaffolds have a wide range of applications in the tissue engineering field. However this combination of polymers does not provide all the properties of bone scaffolds such as mechanical strength, degradation, osteoconductivity and osteoinductivity. So, nanoparticles are blended with chitosan gelatin polymer solution to enhance its properties. In the present study, the nanocomposite scaffold was developed using chitosan (C), gelatin (G), cerium oxide nanoparticles (CNPs), cerium doped hydroxyapatite (CeHAP), silver doped hydroxyapatite (AgHAP) and zinc doped hydroxyapatite (ZnHAP) nanoparticles, where chitosan (C) show structural resemblance to glycosaminoglycan (GAG) and is biocompatible, biodegradable, antimicrobial and non-toxic; gelatin possesses RGD sequence promoting cell adhesion, CNP shows the antioxidant property, CeHAP supports angiogenesis, AgHAP provides the antimicrobial property with mechanical strength and ZnHAP provides osteoinductivity and aids in bone formation. The lyophilization technique is a versatile method for the fabrication of 3D porous scaffolds. In the first study, chitosan-gelatin-cerium oxide nanoparticles (CG-CNPs) nanocomposite scaffolds were fabricated. The dissemination of CNPs helps in the deposition of the apatite layer with the improved antimicrobial properties. All CNPs incorporated scaffolds were cytocompatible on MC3T3-E1 cells. In-ovo and histology studies showed that CNPs containing scaffolds are osteoconductive with quick bone healing. The physicochemical and biological properties of the developed nanocomposite scaffolds revealed CG scaffolds containing 500 μg/ml cerium oxide nanoparticles were the most promising scaffold for bone repair. In the second study, the effects of CeHAP nanoparticles on CG scaffolds were explored in bone tissue engineering applications. The compressive strength and surface roughness of the CG-CeHAP nanocomposite scaffold were enhanced as compared to the control samples. All scaffolds were porous and were biocompatible on Wharton Jelly stem cells. CAM assay revealed CeHAP300 nanocomposite scaffolds (300 μg/ml CeHAP nanoparticles) as an ideal scaffold supporting angiogenesis with more number of blood vessels. In the third study, implant failure is the main hurdle affecting the regeneration of bone defects after surgery, which is mainly caused due to contamination by micro-organisms. The incorporation of AgHAP in CG scaffolds resulted in increased mechanical strength with the improved antimicrobial properties. In addition to that, favorable viability of Wharton jelly stem cells with clear visualization of blood vessels in the CAM area makes CG-AgHAP3 (1.5 wt% AgHAP nanoparticles) suitable for bone tissue engineering. In the fourth study, ZnHAP nanocomposite scaffolds were fabricated to improve osteoinductivity. The better mechanical strength and deposition of large apatite crystals were observed due to ZnHAP nanoparticles in the CG-ZnHAP nanocomposite scaffolds. The presence of more viable cells with better proliferation and differentiation revealed the biocompatible nature of the nanocomposite scaffolds. Also, the H & E staining and cell attachment assay of the CAM based scaffold of CG-ZnHAP3 nanocomposite scaffolds (3 wt% ZnHAP nanoparticles) depicted the best angiogenesis property of scaffolds. Therefore, it could be indicated that CNP, CeHAP, AgHAP and ZnHAP-incorporated CG nanocomposite scaffolds are suitable for bone tissue-engineering applications.