DESIGN AND DEVELOPMENT OF SILK PROTEIN-BASED COMPOSITE MATERIALS FOR BIOMEDICAL APPLICATIONS

Abstract

Biomedical engineering combines fundamental knowledge and problem-solving skills from engineering and medical science to design various types of biomaterials for healthcare applications. Biomaterials and their composites are currently used in a variety of applications such as diagnostics, imaging and therapy, as well as implants, stents, pacemakers, tissue engineering, and controlled drug delivery systems. In order to be used in biomedical applications, a biomaterial must be easily fabricated into various formats and have bio-active, bio-compatible, immuno-compatible, mechanical stable, and tunable degradation properties. Researchers focused on exploiting biomaterials for better interaction with biological systems in order to overcome the drawbacks associated with the use of metals, ceramics, and synthetic materials. The challenging concerns with the fabricated synthetic polymers, such as their bio-compatibility, tuneable bio-degradability, formation of neo-tissue after implantation, and porosity, limit their utility. Thus, to overcome these limitations, naturally occurring silk proteins (such as fibroin and sericin) have been used as a biomaterial for various biomedical and tissue engineering applications. In the present thesis work, Bombyx mori silk cocoons derived proteins (fibroin and sericin) were blended with synthetic polymers such as polyvinyl alcohol (PVA), poly caprolactone (PCL) and other natural polymer such as alginate have been used for fabrication of various forms of scaffolds such as nanofibers and porous beads for biomedical and tissue engineering applications. Along with the growing literature on therapeutic role of silk proteins in biomedical applications such as wound healing. The layer by layer dual proteins (fibroin and sericin) blended with PVA and PCL based nanofibrous scaffold was fabricated using electrospinning. Further, the antibacterial drug (silver (I) sulfadiazine) loaded triple layered nanofibrous scaffold was fabricated and its antibacterial efficacy was validated against Gram negative (E. coli DH5α) and Gram positive (S. aureus) bacteria. The biocompatibility and wound healing properties of triple layered nanofibrous scaffold was further validated using in vitro assays (MTT, live and dead, cell adhesion and in vitro scratch assays) against NIH-3T3 cells. Furthermore, wound healing potential of drug loaded nanofibrous scaffold was investigated in mice model (Balb/c). The role of silk proteins in tissue engineering applications such as development of three-dimensional porous scaffold for in vitro cancer model was investigated. In this work, silk fibroin blended with other natural polymer such as alginate has been used for fabrication of lyophilized porous sodium alginate/silk fibroin alginate beads using ion crosslinking method. Further, These lyophilized beads were used to develop three dimensional lung cancer model after validation of its biocompatibility against normal lung epithelial cells (L132) using in vitro assays ( MTT, cell adhesion , live and dead) . Further, 3D in vitro lung cancer model was developed using non-small lung cancer cells (A549) and the FDA approved drug was tested against A549 cells cultured in both two dimensional (2D) and 3D in vitro cancer model. Furthermore, superparamagnetic nanoparticles (SPIONs) loaded porous sodium alginate and silk fibroin composite beads was fabricated using ion-crosslinking method. The magnetization properties of spions loaded beads was further investigated. The bio-compatibility of alone spions and spions loaded beads was validated using in vitro assays and the effect of static magnetic field with varying intensities were elucidated by in vitro assay (live and dead) against lung cancer cells (A549) in 2D and 3D cancer models. In summary, the present study illustrates the role of silk proteins and its composites in fabrication of nanofibrous scaffold for wound healing studies and porous beads for development of in vitro cancer models for screening of drugs (such as anti-cancer) and mechano-transduction studies (magneto-apoptotic studies).