Protein denaturation driven random laser as a probe for thermal biosensing

This study demonstrates the tuning of Random Laser (RL) emission using the phase transition in Bovine Serum Albumin (BSA). A silica capillary filled with a Rhodamine B (RhB)-BSA solution served as the lasing medium, showing strong temperature-dependent behaviour. The peak emission wavelength exhibited a significant blue shift of ∼1.25 nm/°C between 30 and 50 °C, while from 50 to 70 °C the shift is less pronounced, and a reduction in the number of lasing modes is observed with temperature, which indicates the altered feedback and gain conditions. UV-Vis studies showed significant changes in absorption as the temperature was increased from 30 °C to 70 °C. Secondary structure analysis from the CD data showed nearly a fourfold decrease of α-helix content in this temperature range, confirming the denaturation of BSA with temperature. PFT analysis of the random lasing emission showed a decrease of cavity path length from 5.65 μm to 0.67 μm which shifted the supported lasing modes toward shorter wavelengths. The combined effect of protein unfolding and the thermo-responsive nature of RhB offers a controllable means for tuning random lasing. The results underscore a facile approach for thermo-optic modulation of biopolymer-dye random lasing with implications in bio-opto-microlasers, protein conformational probing, remote temperature sensing, and temperature-responsive displays.