# Fluorescence Transduction of Liquid Crystal Ordering Transitions for Biosensing

## TL;DR

This paper introduces a new fluorescence-based method to detect biosensing events by converting liquid crystal ordering changes into measurable optical signals.

## Contribution

A novel fluorescence transduction scheme for liquid crystal biosensors using AIE motifs and dynamic covalent chemistry.

## Key findings

- The method detects Salmonella with a limit of 102 cells/mL in about 1 hour.
- Fluorescence ON/OFF states correlate with LC droplet configurations.
- A ratiometric reference dye improves reliability against experimental variability.

## Abstract

Liquid crystal (LC)
ordering transitions are exquisitely sensitive
to molecular interactions at aqueous interfaces and have long served
as the basis for optical biosensors. However, the readout of these
transitions has almost exclusively relied on polarized-light optical
microscopy, which limits quantification and hinders practical deployment.
Here, we report a fluorescence-based transduction scheme that converts
LC ordering transitions to quantitative optical outputs. Our strategy
employs amphiphilic block copolymers bearing aggregation-induced emission
(AIE) motifs that undergo dynamic covalent conjugation with IgG antibodies
through reversible imine chemistry. In complex LC emulsions, polymer
surfactants localize differently depending on droplet LC configuration:
accumulation at monopolar defects concentrates AIE units to generate
a bright ON state, whereas redistribution along the LC/water interface
in the radial configuration suppresses emission to yield an OFF state.
Recognition of Salmonella enterica serovar Typhimuriumone
of the most prevalent foodborne pathogensreversibly perturbs
this equilibrium, producing rapid (∼1 h) ON/OFF fluorescence
responses with detection limits down to 102 cells/mL. Incorporation
of a ratiometric reference dye further enhances robustness against
experimental variability. This work establishes the fluorescence transduction
of LC ordering transitions as a generalizable and portable sensing
paradigm, bridging soft matter design with real-world diagnostics.