1. Ph.D Theses
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Item Synthesis and Biomechanical Studies of Nano Bioceramic Reinforced Hydrogel Composites For Cartilage Tissue Implants(National Institute of Technology Karnataka, Surathkal, 2022) B.Y., Santosh Kumar; G. C., Mohan KumarCartilage damage is persistent and disease, which is having a great shock on people’s daily activity. Thus, repair or replacement has become an effective way to relieve pain. The technological advancement in biomaterials is not enough to overcome the challenges to develop a new material to replace defected Articular Cartilage (AC). The designed material is to fulfil the physical and mechanobiological properties of soft tissue. Hydrogels have drawn much attention as implant biomaterial due to their similarity with native articular cartilage. However, the discrepancy in mechanical properties, durability together with inadequacy to integrate with the surrounding tissue hinder the clinical application. Here, we reported the utilisation of bioceramics as a reinforcement to prepare a novel natural and synthetic polymer composite hydrogel by a physical crosslinking process. The reinforcement content was optimised and it was found that the introduction of bioceramic alters the physical, mechanical and biological properties by cumulative crosslinking in the hydrogel network. More significantly, the introduction of bioceramics in the hydrogel increases the compression strength and they exhibit time-dependent, rapid self-recoverable and fatigue resistant behaviour based on the cyclic loading-unloading compression test. The storage modulus is much higher than the loss modulus, demonstrates they are elastic dominant rather than fluid-like structure. Besides, the antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans microbes and the cell viability towards MG-63 osteoblast and L929 fibroblast-like cells provide a positive lane for developing the substitute biomaterial for cartilage tissue implants.Item Preparation and Characterization of Chitosan Based Polymer Membranes for Water Purification Application(National Institute of Technology Karnataka, Surathkal, 2013) A, Rajesha Kumar; Isloor, Arun M.; Trivedi, Darshak RFor membranes to be competitive with conventional technology, a membrane process needs to operate with a high rate of flux, high degree of selectivity and high resistance to fouling. Chitosan is an excellent membrane material due to its good film forming nature, hydrophilicity, chemical stability and easy chemical modification. The membranes prepared from pure chitosan cannot offer sufficient mechanical stability for application in flow processes. To overcome this problem, techniques of polymer coating and blending have been employed by researchers. Blended chitosan membranes not only display superior mechanical properties but also they are benefited from the intrinsic advantages of each polymer involved in the blend. Chitosan was blended with polysulfone to prepare PSf/CS ultrafiltration membranes. The chemical modification of chitosan has been carried out in the thesis, N-succinyl chitosan (NSCS) and N-propylphosphonyl chitosan (NPPCS) are the two derivatives prepared, among the two, NPPCS is the novel derivative synthesized. Further, these two derivatives were blended with polysulfone to prepare PSf/NSCS and PSf/NPPCS UF membranes. UF membranes were subjected to permeation, antifouling and heavy metal rejection study. Titanium dioxide nanotubes (TiO2NT) were synthesized and incorporated into PSf/CS blend to prepare PSf/CS/TiO2NT UF and NF membranes. PSf/Poly (isobutylene-alt-maleic anhydride) (PIAM) blend nanofiltration membranes were modified by changing coagulation bath with cross-linked chitosan solution. The nanofiltration membranes were subjected to salt rejection study. The PSf/CS, PSf/NSCS and PSf/NPPCS UF membranes showed enhanced permeation and antifouling property compared to pristine PSf UF membrane. Even the UF process was efficient in the rejection of heavy metal ions effectively. Membranes showed a maximum of >90% rejection for Cu, Cd and Ni at very low pressure via polymer enhanced ultrafiltration (PEUF) process. All the nanofiltration membranes showed improved flux and antifouling properties. A maximum of 46 % NaCl rejection was observed in case of PSf/CS/TiO2 membrane with 8 % of nanotube content. Changing the coagulation bath with cross-linked chitosan solution emerged as a best technique to improve salt rejection property of PSf/PIAM membrane.Item Study of new chitosan based derivatives for removal of heavy metals from wastewater(National Institute of Technology Karnataka, Surathkal, 2017) K, Balakrishna Prabhu; Saidutta, M. B.; Isloor, Arun MHeavy metals (such as Cu, Pb and Cr) are harmful contributors to pollution of fresh and marine aquatic bodies. Adsorption is a very efficient and popular technique used in wastewater treatment. Chitosan is a biopolymer derived from chitin, an abundantly occurring natural polymer in nature. As an adsorbent, use of chitosan in natural form is constrained by its inferior mechanical, chemical and swelling properties. In this study, four new chitosan derivatives were synthesized by grafting four ligands on chitosan with a view of improving its characteristics. Each ligand had a single pyrazole ring with two additional nitrogen atoms which are potential binding sites for heavy metal sequestration. Batch studies were carried out to determine the optimum pH for adsorption, the most fitting isotherm, the most fitting kinetic model and the relevant thermodynamic parameters. The maximum monolayer adsorption capacities obtained were 63.5 mg/g for Cr (VI), 91.7 mg/g for Pb (II) and 45.6 mg/g for Cu (II). The probable mode of adsorption was chemisorption. The pseudo-second order model fitted experimental kinetic data very well. The FTIR study revealed that amine, imine and hydroxyl groups participated in metal sequestration. The major decrease in the swelling property of the prepared derivatives makes them a promising choice for applications in practical water treatment contacting equipment. Polysulfone membranes blended with the new chitosan derivative CTSL-2 were prepared. The hydroxyl, amine and the imine functional groups present in the additive evidently increased the hydrophilicity of the surface of the blended membranes as confirmed by contact angle measurements. The contact angle of the blended membrane having 2 wt % additive was 62.55 ± 1 as compared to 70.01 ± 1 for neat polysulfone membrane. The blended membranes also showed a significant improvement in maximum pure water flux (351 Lm-2h-1 against 24 Lm-2h-1 of neat membrane). The BSA anti-fouling test exhibited improved anti-fouling characteristic of blended membrane (FRR of 56%). In the metal rejection study, the maximum rejections observed were 36%, 29% and 61% respectively for the three metals Pb (II), Cu (II) and Cr (VI). Overall, the incorporation of additive in polysulfone membranes demonstrated significant improvement in the permeation properties investigated.