Local sensing of absolute refractive index during protein-binding using microlasers with spectral encoding

TL;DR

This paper demonstrates the use of polymer microsphere lasers as spectral sensors for real-time, multiplexed detection of protein binding events through refractive index changes, enhancing biosensing capabilities.

Contribution

It introduces a novel photonic sensing method using spectral signatures of microlasers for multiplexed, real-time biomolecular detection and surface modification analysis.

Findings

Successful detection of protein binding via spectral shifts.

Real-time monitoring of binding dynamics.

Enhanced multiplexing in flow cytometry.

Abstract

Multiplexed, specific and sensitive detection of antigens is critical for the rapid and accurate diagnosis of disease and the informed development of personalized treatment plans. Here, we show that polymer microsphere lasers can be used as photonic sensors to monitor and quantify direct surface binding of biomolecules via changes in the refractive index. The unique spectral signature of each individual laser can be used to find their size and effective refractive index which adds a new encoding dimension when compared to conventional fluorescent beads. We utilize antibody-functionalized microlasers to selectively detect protein binding. Different stages of the multilayer surface modification can be resolved, and protein binding is demonstrated for two different proteins, IgG and CRP. Moreover, by continuously monitoring single lasers, we demonstrate the possibility of real-time monitoring of binding dynamics between antigens in solution phase and the immobilized antibodies. For multiplexed detection, the microlasers are employed in a flow cytometer configuration, with fast spectral detection and identification of microlasers with and without antigen binding. We envision that by combining microlasers with well-established surface modification chemistries and flow geometries, the multiplexing ability of microbead immunoassays can be strongly increased while also opening avenues for single cell profiling within heterogenous cell populations.