  Characterizing the anchoring properties of smectic liquid crystals (LCs) in
contact with bacterial solutions is crucial for developing biosensing
platforms. In this study, we investigate the anchoring properties of a smectic
LC when exposed to Bacillus Subtilis and Escherichia coli bacterial solutions
using interfaces with known anchoring properties. By monitoring the optical
response of the smectic film, we successfully distinguish different types of
bacteria, leveraging the distinct changes in the LC's response. Through a
comprehensive analysis of the interactions between bacterial proteins and the
smectic interface, we elucidate the potential underlying mechanisms responsible
for these optical changes. Additionally, we introduce the utilization of
topological defects; the focal conic domains (FCDs), at the smectic interface
as an indicative measure of the bacterial concentration. Our findings
demonstrate the significant potential of smectic LCs and their defects for
biosensing applications and contribute to our understanding of bacteria- LC
interactions, paving the way for advancements in pathogen detection and
protein-based sensing.
