Facile preparation of polydiacetylene-based uniform porous fluorescent microspheres for potential immunoassay applications

Fluorescent microspheres are prepared by attaching self-assembled polydiacetylene (PDA) vesicles with carboxyl side groups onto the substrate amino-modified poly(glycidylmethacrylate) (APGMA) microspheres. The characterization by SEM, confocal microscopy and flow cytometry demonstrated that the final resulting microspheres are highly uniform both in size (with a diameter of 5 gm) and in fluorescence emission (coefficient of variance < 3%). The Brunauer-Emmett-Teller (BET) surface area of these spheres is 114 m(2) g(-1). In addition, there are evenly distributed pores with an average size of 20.6 nm on the spheres. These spheres are found to have good thermal stability and photostability, and do not suffer from fluorophore leaching. Fluorescein isothiocyanate (FITC) labelled bovine serum albumin (BSA) as a representative biomolecule can be easily attached onto the fluorescent microspheres. All these characteristics possessed by the APGMA-PDA spheres allow them to be directly used as carriers of biomolecules in lab-on-a-chip immunoassay systems.