Microsphere Solid‐State Biolasers

Biolasers obtained from biomaterials are attracting a wealth of interest for their potential as future biosensors with enhanced sensitivity, and advanced cell tracking. Here, miniature biolasers are reported, which are formed by bovine serum albumin (BSA) protein and biosourced polysaccharides derived from land plants such as cellulose and pectin. Using a green processing route aided by simple emulsions, solid‐state microspheres with diameters of 15–100 µm are fabricated and utilized as whispering gallery mode lasers with thresholds of a few µJ mm^–2 and quality factors of up to 3000. Furthermore, BSA microlasers are found to be compatible with cell growth and resistant to the aqueous environment of cell culture media. This environmentally friendly and biocompatible design shows promise for future implantable biosensing devices opening a path between laser science and medicine.