Photothermal lateral flow immunoassay using microfiber long-period grating

Paper-based biosensors are important analytical tools in biological and chemical fields. To increase the detection limit and range, here we demonstrated a microfiber long-period grating (mLPG) based biosensor for lateral flow immunoassay (mLPG-LFIA). Compared to conventional paper-based biosensor, the mLPG with strong evanescent wave functions as an ultrasensitive tool for detecting the refractive index changes induced by the localized plasmonic heating of antibody-conjugated gold nanoparticles. The LFIA concentration level is encoded into the refractive index modulation and can be subsequently read by measuring the spectral shift of the mLPG. As proofof-concept demonstration, quantitative analysis of heavy-metal chromium-ion concentrations ranging from of 0.195 to 200 ng/mL is performed, and a detection limit of 0.219 ng/mL is achieved. The proposed technique is sensitive, easy-to-use, and can serve as a powerful tool to analyze trace chemicals or biochemicals for application in the area of medicine, foods safety and environment monitoring.

Automated summary

The study demonstrated a microfiber long-period grating (mLPG) based biosensor for lateral flow immunoassay to enhance detection limit and range. The mLPG showed strong evanescent wave functions and was sensitive in detecting refractive index changes induced by gold nanoparticles. The technique proved to be sensitive, easy-to-use, and effective in analyzing trace chemicals or biochemicals for various applications.