DEVELOPMENT OF BIOPOLYMERS BASED HYDROGELS FOR VARIOUS APPLICATIONS

Abstract

In this thesis, the research aims on the synthesis of tamarind kernel gum (TKG) and carboxymethyl tamarind kernel gum (CMTKG) based hydrogels and utilized different nanocomposite hydrogels for mainly drug delivery applications. Various inorganic fillers such as silver nanoparticles, zinc nanoparticles, and zeolites has been incorporated into hydrogels and used in different applications such as drug delivery and dye removal applications. This thesis has been summarized in 6 chapters. Chapter 1 outlines different aspects regarding the properties, synthesis, and applications of hydrogels. This chapter gives insight about the hydrogels, their classification, and their methods of synthesis. The chapter also discusses the introduction of biopolymers, especially Tamarind Kernel Gum (TKG) and its derivative, Carboxymethyl Tamarind Kernel Gum (CMTKG), which can be used to synthesize hydrogels for different applications. The chapter also focuses on the applications of hydrogels, such as drug delivery systems, tissue engineering, wound healing, dye removal, agricultural, metal ion removal, biosensors, textile, and food industry. In Chapter 2, a novel hydrogel network based on carboxymethyl tamarind kernel gum/poly (sodium acrylate) was synthesized by using polyethylene glycol diacrylate (PEGDA) as a cross-linker. Zinc Oxide nanoparticles (ZnO NPs) were prepared via hydrothermal synthetic method and developed ZnO NPs were embedded within CMTKG/poly(sodium acrylate (PSA) hydrogel for the controlled release studies of ciprofloxacin drug. Various techniques such as FTIR, XRD, FESEM, and TEM were used to characterize the synthesized ZnO NPs, pure hydrogel, and hydrogel nanocomposites. Various parameters such as drug loading, drug entrapment, gel content, and porosity were estimated for all the synthesized hydrogel nanocomposites. The swelling and rheological studies revealed that ZnO NPs embedded hydrogel composites exhibited increased swelling tendency and thermal stability. The antibacterial action of CMTKG-based hydrogel nanocomposites was studied using E. coli (gram-negative) bacteria with the help of the disc diffusion method. The result showed that the incorporation of ZnO NPs enhanced the antimicrobial action of ciprofloxacin-loaded CMTKG-based hydrogels. The kinetic modelling of drug release viii was done using Higuchi and Korsmeyer - Peppas model. The higher value of Regression coefficient (R2 ) close to unity indicated that the mechanistic pathway of drug release from the hydrogels was more fitted in the Korsmeyer-Peppas model followed by Fickian diffusion. Chapter 3, deals with the green synthesis of novel silver nanoparticles (Ag NPs) embedded TKG/PSA nanocomposite hydrogel without the use of any toxic materials. The developed hydrogels were characterized using XRD, FTIR, U V-visible, FE-SEM, and TEM techniques. Doxycycline was chosen as a model drug for release studies using TKG/PSA and Ag/TKG/PSA nanocomposite. The observation is that Ag/TKG/PSA hydrogel nanocomposite showed a pH-dependent swelling which is higher at pH 7.4 than at pH 1.2. Similarly, the cumulative drug release percentage using silver nanocomposite is higher at pH 7.4 than at pH 1.2. Also, the presence of Ag NPs decreased the swelling ratio of TKG/PSA hydrogel, which controls the Doxycycline drug's release rate. In addition, the Doxycycline release kinetics studies indicated that the drug release data was fitted in the Korsmeyer-Peppas model with a higher R2 value. Thus, Ag/TKG/PSA nanocomposite showed satisfactory results for sustainable release of Doxycycline drug. Chapter 4, describes the synthesis of hydrogel films comprising of CMTKG, polyvinyl alcohol (PVA), and guar gum (GG) using glutaraldehyde (GTA) as cross-linker. The synthesized hydrogel films were evaluated in terms of equilibrium swelling ratio, moisture content, thickness, wetting analysis, thermal analysis, and mechanical analysis. The tensile strength of the films lie in the range of 95.80 to 149.07 MPa while elongation at break value lies in the range of 1.51 to 5.20%. The synthesized hydrogel films were characterized by techniques such as FTIR, FE-SEM, TGA, and DTA. The ciprofloxacin (CFX) drug was embedded in the best-swelled hydrogel film and in vitro drug release behavior was studied at alkaline pH 7.4 phosphate buffer solution. It was found that the maximum drug release was to be 73 % after 24 hours at pH 7.4. Moreover, the release data was fitted in various kinetic models such as the First-order, Higuchi, and Korsmeyer-Peppas models. The best-fitted Korsmeyer-Peppas model suggested that the release of the drug follows Fickian diffusion and the value of diffusion exponent (n) was determined to be 0.38. Chapter 5 deals with the synthesis of zeolite-loaded CMTKG based hydrogels as a potential adsorbent for the removal of crystal violet dye. Initially, the crosslinked hydrogel of CMTKG with sodium methacrylate (SMA) was prepared via a free radical mechanism using a methylene bisacrylamide (MBA) cross-linking agent and potassium persulfate (KPS) as initiator. In this way, various formulations of hydrogels were prepared by varying the content of zeolite. The swelling capacity of all the synthesized hydrogels was investigated and the composition of hydrogel which exhibited maximum swelling wasused for the characterization and dye removal experiment. Crystal violet (CV) was chosen as a model dye for the dye removal experiment. The structure of zeolite and zeolite-embedded hydrogel was elucidated by XRD, FTIR, and SEM-EDX analysis tools. The adsorption experiment was investigated by varying the CV concentration, hydrogel amount, temperature, dye solution pH, adsorption time, and ionic strength. The Langmuir and Freundlich isotherm models were used to fit the adsorption data and it was noticed that the data fitted well with the Langmuir model. The hydrogel's maximum dye adsorption efficiency was found at 123.60 mg g -1 . The adsorption kinetic studies were followed by pseudo-first-order and intraparticle diffusion kinetic models. In addition, regeneration studies were performed for the best adsorbent hydrogel using ethanol solvent and the result concluded the desorption efficiency of hydrogel (82%) over four desorption cycles. Overall, the synthesized hydrogel material was used as an effective adsorbent for removing hazardous cationic dye from polluted water.