The first example of an all-organic oligofluorene truxene based distributed feedback laser for the detection of a specific protein-small molecule interaction is reported. The protein avidin was detected down to 1μgmL(-1) using our biotin-labelled biosensor platform. This interaction was both selective and reversible when biotin was replaced with desthiobiotin. Avidin detection was not perturbed by Bovine Serum Albumin up to 50,000μgmL(-1). Our biosensor offers a new detection platform that is both highly sensitive, modular and potentially re-usable.