posted on 2024-06-06, 09:14authored byPeng Bao, Kyle Phillips, Rasmita Raval
Liquid crystal (LC) biosensors have received significant
attention
for their potential applications for point-of-care devices due to
their sensitivity, low cost, and easy read-out. They have been employed
to detect a wide range of important biological molecules. However,
detecting the function of membrane proteins has been extremely challenging
due to the difficulty of integrating membrane proteins, lipid membranes,
and LCs into one system. In this study, we addressed this challenge
by monitoring the proton-pumping function of bacteriorhodopsin (bR)
using a pH-sensitive LC thin film biosensor. To achieve this, we deposited
purple membranes (PMs) containing a 2D crystal form of bRs onto an
LC-aqueous interface. Under light, the PM patches changed the local
pH at the LC-aqueous interface, causing a color change in the LC thin
film that is observable through a polarizing microscope with crossed
polarizers. These findings open up new opportunities to study the
biofunctions of membrane proteins and their induced local environmental
changes in a solution using LC biosensors.