Local Sensing of Absolute Refractive Index During Protein-Binding using Microlasers with Spectral Encoding

Soraya Caixeiro, Casper Kunstmann-Olsen, Marcel Schubert, Joseph Hill, Isla R.M. Barnard, Matthew D. Simmons, Steven Johnson, Malte C. Gather

Research output: Contribution to journalArticlepeer-review

5 Citations (SciVal)


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, it is shown 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. Antibody-functionalized microlasers selectively detect protein binding, as demonstrated for Immunoglobulin G and C-reactive protein, and have the ability to resolve different stages of the multilayer surface modification. Moreover, by continuously monitoring single lasers, the possibility of real-time monitoring of binding dynamics between antigens in solution phase and the immobilized antibodies is demonstrated. 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. It is envisioned 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 heterogeneous cell populations.

Original languageEnglish
Article number2300530
JournalAdvanced Optical Materials
Issue number13
Early online date11 Apr 2023
Publication statusPublished - 4 Jul 2023

Bibliographical note

Funding Information:
This work received financial support from EPSRC (EP/P030017/1), the Humboldt Foundation (Alexander von Humboldt Professorship) and European Union's Horizon 2020 Framework Programme (FP/2014‐2020)/ERC grant agreement no. 640012 (ABLASE). M.S. acknowledges funding by the Royal Society (Dorothy Hodgkin Fellowship, DH160102; Research Grant, RGF∖R1∖180070; Enhancement Award, RGF∖EA∖180051).


  • immunoassays
  • microfluidics
  • microlasers
  • refractive index sensing
  • whispering gallery modes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics


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