Crystalline poly(L-lactide) (PLLA) nanoparticles were prepared by aminolysis of electrospun PLLA nanofibers and subsequently labeled by a fluorescent colorant. The size of the nanoparticles could be controlled by either the conditions of the aminolysis reaction or the diameter of the original electrospun fiber. The latter method resulted in higher yield. Although the as-spun nanofibers were generally amorphous, the nanoparticles showed high crystallinity in the typical α-form of PLLA crystals, as revealed by X-ray diffraction and differential scanning calorimetry. Gel-permeation chromatography was used to determine the molecular weight of the formed particles in relation to aminolysis time. After aminolysis, PLLA nanoparticles spontaneously generated amine groups on the surface, which are available for further modifications. In this study the amine groups were reacted with isothiocyanate groups, and fluorescein-5'-isothiocyanate was successfully attached to the PLLA nanoparticles. Smaller particles showed significantly higher fluorescein binding density. Through this simple 'top-down' routine, it was possible to create nanoparticles with tailorable size and specific surface functions. Such materials could serve in bioimaging or nanomedicine applications.
Keywords: AMINOLYSIS; ELECTROSPINNING; FLUORESCENT LABELING; NANOPARTICLES; POLY(L -LACTIDE).