Next generation in-situ sensing on-a-chip (μSoC)

Abstract

Organ-on-chips (OoCs) are micro-fabricated cell culture platforms that mimic the function and structure of human organs. Limitations arose in the use of OoCs when they lacked sensing abilities and real-time monitoring. Throughout this thesis, an attempt is being made to address these complications by developing an \textit{in situ} glucose sensor for OoCs in collaboration with Bi/ond. The foundation of this proof-of-concept is an etalon, consisting of two reflective layers separated by a dielectric layer that allows light to enter and resonate between the reflective layers. The dielectric layer for this purpose will be microgels, with particular emphasis on the biomedical potential of the thermoresponsive polymer poly-(N-isopropylacrylamide) (pNIPAAm).
This sensor was developed on silicon and PDMS substrate using evaporation of Cr/Au, spin-coating pNIPAAm-co-10%-AAc and pNIPAAm-co-10%, and mid or post process modification with APBA. Plasma treatment was employed to create a monolithic layer, resulting in a successfully completed fabrication process verified through SEM. Reflectance spectroscopy confirmed the functionality and response, along with an effective generation of a calibration curve for glucose for both substrates and modification processes. The post process approach emerged as more preferable while exhibiting resilience to sterilization procedures that even improved its response to glucose due to removal of unbound APBA during sterilization. Post process samples were used to detect changes in glucose levels in cell medium that had been in contact with C2C12 mouse myoblast cells over 1-, 3-, and 7-day periods. The results showed that the concentration of glucose declined approximately 16 mg/dL after day 1, 130 mg/dL after day 3 and 227 mg/dL after day 7, in comparison to the control measurement. Additionally, there was optical confirmation of the non-toxic effects of the microgel-beads on cell culturing. The investigation of this proof-of-concept of glucose responsive microgel-based etalons was successful, and the next stage would involve integrating this sensor into a chip of Bi/ond.