The design and fabrication of a cytomorphic double network hydrogel

Abstract

Wearable and implantable biosensors are emerging as promising devices for the continuous monitoring of individuals in the context of sports and health. The successful development and deployment of these devices could yield tremendous health benefits to the general population. Biosensors have to perform in complex biological environments that contain a wide variety of biomolecules that can interact with the biosensor in an undesirable way, affecting the biosensor performance and lifetime. Among these interactions, the blockage of bioreceptors by biomolecules (biofouling) and the non-specific adsorption of biomolecules to the sensor are two major processes that limit the successful deployment of biosensors.
This thesis presents a novel cytomorphic double network hydrogel (CDNH) structure to address biofouling and the non-specific adsorption of biomolecules. The CDNH mimics the functioning of a cell, the best biosensor ever created in nature. Cells have a membrane that separates the interior and outer world. The cell membrane selectively allows specific molecules to pass to the interior, where the biorecognition and metabolic processes happen. The CDHN comprises a structural hydrogel hemisphere to mimic the inner cell cytoskeleton and an outer network to mimic the cell membrane. The inner network is a poly (ethylene glycol) diacrylate (PEGDA) hydrogel with a large pore size. With the open structure of the inner network, the aim is to improve the diffusion of the target molecules to the bioreceptors (aptamers). Furthermore, the aim is to reduce steric hindrance for the binding of the target molecules to the bioreceptors. The outer network is a polyacrylamide hydrogel with a very dense mesh (nanopores). The outer network aims to function as a size exclusion filter, selectively allowing only small biomarkers to access the sensing site. By separating the dense outer network from the open structured inner network, the CDNH aims to reduce biofouling and ANSM while still ensuring adequate diffusion of the target biomarkers to the receptors and binding of the target biomarkers to the receptors.
Integration of the CDNH with a relatively simple 2-electrode sensor was achieved which enabled the electrical characterization (EIS) of the CDNH, providing crucial insights into the electrical behaviour of the CDNH in an electrochemical solution.
Overall, this work presents the foundation for a novel structure that is expected to improve biosensing drastically, contributing to the realization of continuous sports and health monitoring.