SURGICAL COTTON MICROFIBERS BASED SCAFFOLDS FOR BONE TISSUE ENGINEERING

Abstract

Commonly skeletal diseases, trauma, degenerative spinal diseases, fall fractures, and tumor resections create bone loss and defects. Bone loss or damage usually causes intolerable pain and affects day-to-day life and even sometimes may cause death. Worldwide the number of bone damage/fractures due to traumatic and accidental injuries has been growing exponentially. Currently available treatments for bone repairing are slow, and often full functional recovery is not achieved. Hence, a potential solution to fix the above problems is the development of engineered structures through the combination of scaffolds, cells, and growth factors. Scaffold, for bone tissue engineering (BTE), has to be biodegradable, biocompatible, porous, mechanically strong, and should show cell proliferation and differentiation along with many other characteristics. Since one material is unable to provide all of these properties, different materials should be combined together to fabricate a scaffold. In this study I developed scaffolds consisting of surgical cotton cellulose microfibers (C), gelatin (G), chicken egg white (EW), nanoceria (NC) and chicken eggshell derived nanohydroxyapatite (nHA), where the cotton microfibers used as a novel skeleton in the scaffolds. Cotton microfibers could address the issues that have been remained in case of cotton nanofibers (CNF) such as large scale production and toxicity in terms of human health. Gelatin, a naturally occurring biopolymer that is a derivative of collagen, was used to provide a stable structure to the cellulose microfibers. EW (high quality protein) was supposed to offer the scaffold with several cell attachment sites. The bone-bonding properties were improved by adding nHA into the scaffolds. Oxidative stress at the location of the surgical wounds and bone fracture slows the bone healing process. The principal source of oxidative stress is an increase in ROS levels. Due to the redox-modulating behavior, nanoceria can scavenge the ROS. The scaffolds were fabricated using the very simple freeze drying method. In Chapter 3, paper scaffolds were fabricated. Coating with various gelatin concentrations enhanced the physicochemical and mechanical properties of the scaffolds significantly compared to plain paper sheets. In vitro studies, by seeding MG-63 cells over the scaffolds, revealed an enhancement in cell viability and their attachment as compared to the unmodified scaffold: this indicates a huge perspective of the paper-based scaffold as a bioactive, well-designed and economical stand for BTE application.In Chapter 4, 3D microporous C, CC and CCG-scaffolds of cotton microfibers, citric acid and gelatin were developed by casting and freeze-drying techniques. According to the findings, crosslinking of cotton microfibers with citric acid produced a stable 3D porous scaffold (CC) as compared to uncrosslinked cellulose (C) scaffold. Gelatin-modified CCG scaffold outperformed CC scaffold in terms of mechanical, physiochemical, and biocompatibility characteristics. In chapter 5, a quaternary (CGEWnHA) scaffold was developed using cellulose microfibers (C), gelatin (G), egg white (EW), and nanohydroxyapatite (nHA). EDC/NHS crosslinking system was used to fabricate the scaffolds and their physico-chemical, mechanical and biological properties were studied. When compared to a single protein, the synergistic integration of gelatin and egg white into the scaffold improved the above properties. The CGEWnHA demonstrated the most desirable properties for a prospective bone tissue engineering scaffold. CGEWnHA exhibited a spongy form, outstanding stability in PBS and culture media as compared to CCG scaffold. In chapter 6, the problem, related to high oxidative stress due to free radical generation during bone healing, has been addressed by developing a CG-NCs scaffolds; incorporating NC in the CG. Incorporation of NC has increased the mechanical properties. Additionally, CG-NCs depict competent cell attachment, proliferation and viability.The results for osteogenic differentiation studies (i.e. ALP activity and ARS staining) have indicated that CG-NCs scaffolds hold potential to deposit minerals by cells. Finally, the results for free radical scavenging functionality demonstrate that CG-NCs are capable of reducing free radicals. The study's findings conclusively show that cellulose microfiber-based scaffolds could be a viable option for bone repair, even though the fabricated scaffolds still require more in-depth investigation on in-vivo and large animal model studies. New materials i.e., paper sheet from surgical cotton, CCG, CGEWnHA and CG-NCs were developed and studied for their basic bone tissue engineering application potential and would be vital for applications in bone tissue-engineering in future regenerative therapies. CGEWnHA scaffold showed the most magnificent properties among the developed 3 D scaffolds such as CCG, CGEWnHA, and CG-NCs.