Bioinspired fluorescence, being widely explored for imaging purposes, faces challenges in delivering bright biocompatible sources. While quite a few techniques have been developed to reach this goal, encapsulation of high-quantum yield fluorescent dyes in natural biological forms suggest achieving superior light-emitting characteristics, approaching amplified spontaneous emission and even lasing. Here we compare gain capabilities of highly concentrated Rhodamine B solutions with a newly synthesized biocompatible peptide derivative hybrid polymer/peptide material, RhoB-PEG1300-F6, which contains the fluorescent covalently bound dye. While concentration quenching effects limit the maximal achievable gain of dissolved Rhodamine B, biocompatible conjugation allows elevating amplification coefficients towards moderately high values. In particular, Rhodamine B, anchored to the peptide derivative material, demonstrates gain of 22–23 cm−1 for a 10−2 M solution, while a pure dye solution possesses 25% smaller values at the same concentration. New biocompatible fluorescent agents pave ways to demonstrate lasing in living organisms and can be further introduced to therapeutic applications, if proper solvents are found.

Optical bound states in the continuum (BICs) have recently attracted a great deal of attention as an efficient way to localize and manipulate light at nanoscale. Traditionally, generation of BICs has relied on using artificial structures where suppression of radiative losses leads to very high Q factors. Here, we show that BICs may play an important biological role by boosting light−matter interactions in a biogenic nanostructure: tapetum reflector of a shrimp eye. Enveloping photosensitive units of the retina (rhabdoms), this system contains quasiperiodic arrays of spherical core−shell nanoparticles which include concentric lamellae of single-crystal isoxanthopterin nanoplates arranged around a hollow core. The radial alignment of the plates gives rise to the spherical anisotropy of the nanoparticles which provides access to quasi-BIC modes in a full visible domain. Thus, a tapetum reflector hosting BICs maximizes light interactions with rhabdoms, enhancing the eye's sensitivity. Our findings suggest that BICs, previously associated with man-made structures only, can be generated in biogenic structures, performing crucial optical functionalities in living organisms.

Laser beams, capable to control the mechanical motion of micron-scale objects, can serve as a tool, enabling investigations of numerous interaction scenarios under full control. Beyond the pure electromagnetic interactions, giving rise to conventional gradient forces and radiation pressure, environment-induced thermal effects can play a role and, in certain cases, govern the dynamics. Here we demonstrate a thermocapillary Marangoni effect, which is responsible for creating long-range few hundreds of nano-Newton forces, acting on a bubble around a ‘gilded vaterite’ nanoparticle. Decorating calcium carbonate spherulite (the vaterite) with gold nanoseeds allows tuning its optical absorption and, as a result, controlling its temperature in a solution. We demonstrate that keeping a balance between electromagnetic and thermal interactions allows creating of a stable micron-scale bubble around the particle and maintaining its size over time. The bubbles are shown to remain stable over minutes even after the light source is switched off. The bubbles were shown to swim toward laser focus over 400 of micrometer distances across the sample. Optothermal effects, allowing for efficient transport, stable bubble creation, and particle-fluid interaction control, can grant nano-engineered drug delivery capsules with additional functions toward a theragnostic paradigm shift.