Preparation of cross-linked, multilayer-coated fluorescent microspheres with functional groups on the surface for bioconjugation.

Abstract

This study is to develop a method for preparing fluorescent microspheres with steady and strong fluorescence as well as the surface functionality for bioconjugation. Layer-by-layer technique was employed to introduce poly(phenylenevinylene) (PPV) precursor, diazoresin (DAR), and polyanion, including poly(acrylic acid) (PAA) and poly(sodium-p-styrenesulfonate) (PSS), onto the substrate polystyrene-divinylbenzene microspheres with sulfonic groups on the surface (SPSDVB). The conversion of PPV precursor into fluorescent PPV as well as the cross-linking reaction between DAR and polyanion, were accomplished simultaneously in the following thermal treatment. After optimizing the DAR concentration, the selection of polyelectrolytes and the coating sequence, the cross-linked multilayer coated PPV microspheres, SPSDVB-(PPV/PSS/DAR/PAA) spheres, were prepared. These spheres were found to have uniform size with a clear core-shell structure and display even and strong fluorescence, based on the characterization by flow cytometry, microscopy, and photophysics. They were found to be stable and highly resistant to common solvents and even "dissociation agent", as well as possess good thermal stability and photostability. The feasibility of conjugating biomolecules on the surface of spheres was also demonstrated.