This dissertation presents the fabrication of a silicate-based nanocomposite hydrogel with outstanding shear-thinning properties, viscoelastic behaviour, and water retention capacity. Due to their adaptable mechanical properties, bioavailability, and water retention capacity, these nanocomposite hydrogels have been extensively used for biomedical applications. Laponite nanoparticles are among the most utilized silicate-based minerals. These clay nanoparticles are composed of platelets that are positively charged on the edges and negatively charged on the surface. The high aspect ratio of the polyanionic surface of the Laponite nanoparticles can absorb and trap ionic functional groups with non-covalent interactions.
These silicate-based nanocomposite hydrogels are produced by dispersing Laponite nanoparticles in deionized water, forming a homogenous colloid. The uniform dispersion of these nanoparticles in aqueous solutions forms a “house of cards” structure, which eliminates particle aggregation and improves their surface interaction with ionic compounds. The fabrication process is followed by the addition of the stable colloid to various organic and inorganic mixtures including, chitosan, alginate, graphene oxide, and gelatin. The chemical, physical, and mechanical properties of these nanocomposites are experimentally evaluated.
Silicate-based nanocomposite hydrogels offer unique rheological characteristics, which facilitate the injection process while preserving the mechanical integrity of the construct following extrusion. The injectability of these nanocomposites was assessed by evaluating their shear-thinning properties through multiple rheological analyses. As per the definition of shear-thinning, the viscosity of nanocomposites is directly affected by the applied shear stress; the viscosity of these compositions decreases under shear stress and reverts to the original viscosity after removal of the force. Accordingly, nanocomposite hydrogels with shear-thinning properties can be utilized for extrusion-based 3D printing and for depositing drugs in localized tissue without the jeopardy of being washed away by circulating blood.
In addition, the large number of surface interactions and cationic exchange capacity of Laponite nanoparticles improve electrostatic interactions between the nanocomposite components and a wide range of ionic compounds. Accordingly, these chemical properties facilitate the incorporation of stimuli-responsive materials into the polymeric structure of the nanocomposite, allowing for the utilization of these hydrogels in on-demand drug delivery applications. These properties of the silicate-based nanocomposite hydrogels are investigated through swelling and release studies, Fourier transforms infrared spectroscopy (FTIR), and zeta potential measurements. The results of these experiments indicate that the non-covalent electrostatic interactions and chemical properties of these hydrogels improve the solubility and loading efficiency of therapeutic agents.
Silicate-based nanocomposite hydrogels may also be utilized for developing electrical conductive bioinks for extrusion-based three-dimensional (3D) printing. Adjusting the viscosity and shear-thinning properties of the hydrogel plays a significant role in the printability of a bioink. For instance, a highly viscous bioink disrupts extrusion, while a bioink with a low viscosity results in the formation of droplets instead of the desired cylindrical filaments. Optimized formulations of the nanocomposite hydrogels are investigated by conducting various mechanical property measurements. Consequently, the unique chemical and rheological properties of the proposed hydrogels make them superior candidates for drug delivery and tissue engineering applications.