a human - safe fluorescence particle that can be used for fluorescence detection instruments or act as a safe simulant for mimicking the fluorescence properties of microorganisms . the particle comprises a non - biological carrier and natural fluorophores encapsulated in the non - biological carrier . by doping biodegradable - polymer drug delivery microspheres with natural or synthetic fluorophores , the desired fluorescence can be attained or biological organisms can be simulated without the associated risks and logistical difficulties of live microorganisms .