Thin-film amorphous silicon photodiodes with integrated fluorescent filters for monitoring live-cell G-protein coupled receptors (GPCR)

This work demonstrates the feasibility of using miniaturized thin-film amorphous silicon (a-Si:H) photodiodes with an integrated fluorescence filter to detect GPCR signalling in mammalian cells. Activation of HEK293T cell endogenous muscarinic M1 GPCR is monitored by following the intracellular calcium (iCa²⁺) transient rise upon agonist addition, making use of Ca²⁺ specific fluorophores. For macroscale experiments (50 μL culture volume), photodiodes with an area of 2 mm² were fabricated and proved efficient to detect the iCa²⁺ fluxes with the same accuracy as standard fluorescence microscopy. Microscale experiments (50 nL cell culture), rely on microfluidic channels for cell culture that can be integrated with an array of 200 × 200 μm² a-Si:H photodiodes. Whereas fluorescence microscopy confirmed the GPCR activation in the microscale environment, the miniaturized 200 x 200 μm² photodiodes presented the appropriate electronic and optical characteristics for iCa²⁺ fluorescence monitoring.