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Abstract

The field of bioelectronics has come a long way in terms of its capabilities and outreach. Beginning with simple metallic electrodes and nanoscale field-effect transistors for biosensing or cellular stimulation the materials choices and design for bioelectronic architectures has evolved tremendously. Amongst the factors that led to such progress include the strategic identification of materials that would enable formation well-coupled junction with the cellular environment. Materials with a reduced mismatch of mechanical properties and optical or electronic properties allowing transduction of an external stimulus to cell responsible stimuli have been crucial in the development. Though the development of fundamental biophysical perspective has progressed the applicability of these across scales of the cellular environment, from invitro cultures to invivo organs have been slow. These have been attributed to three shortcomings. 1. Lack of knowledge of cellular signaling pathways activated by bio-electronic stimulation, 2. Design of material architectures for forming tissue level interfacing with low cytotoxicity, long term stability, and mechanical compatibility, 3. A platform for simultaneous sensing and stimulation. Seamless integration is the ultimate goal in bioelectronics wherein we overcome the three main difficulties discussed above, to expand proof-of-concept ideas into biomedical devices. Among the three main shortcomings, we plan to address the first two in this work. The consequences of bioelectronic stimulation have been observed to be in four different modes - Thermal, capacitive, mechanical and electrochemical -subject to the electronic structure of the nanomaterial, mechanical properties, and nature of the external stimulus. On a cellular level, each of these modes can induce their specific transduction pathways, which could have consequences leading to adaption or apoptosis of cells to such a perturbation. Systems leading to adaptation would be due to genetic or proteomic changes in the cellular system the utility of which could be used in disease cure. Similarly controlling apoptosis and its underlying mechanism could be utilized for developing specific cancer therapies and wound healing. Besides the adaptation of cells to stimulation-induced cellular perturbations, it could also be exploited via biomimicking nanomaterials that possess structure and properties similar to biological materials. Furthermore, to generalize our study it is important to move beyond adaptive and apoptotic signaling to study modulation of signaling synchronization between specific cell types. Such studies are important specifically from a neuromedicine perspective and form the foundation to address diseases in memory, learning or neurodegenerative disease. Hence studying artificial neuronal networks with various modes of stimulation provide a preliminary foundation in this aspect. Designing architectures that can simultaneously be mechanically and biologically compatible, along with optoelectronic activity for stimulation are tricky keeping materials choices fixed. Thus, to satisfy the existing demands -the design of hybrid biointerfaces with a mechanically soft component and an optoelectronically active component is a proposed strategy. To achieve the development of such hybrid biointerfaces the use of conventional material synthetic processes is insufficient as most synthesis techniques are dynamically stable for, they are optimized for specific synthetic pathways and mechanisms. Thus, we require multistep synthetic strategies or unconventional non-equilibrium synthetic processes for the development of such hybrid materials. This thesis explores unconventional non-equilibrium synthetic methods like laser ablation synthesis, cavitation synthesis and self-assembly for the design of semiconductor-based hybrid interfaces with specialized properties to modulate various signaling processes in a variety of biological systems.

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