Poly(Lactic Acid) Magnetic Microparticle Synthesis and Surface Functionalization

Iron oxide nanoparticles have been employed for a variety of biomedical applications in both the diagnostic and therapeutic realm, and the number of applications continues to grow. In this letter, magnetic nanoparticles were synthesized via aqueous coprecipitation and subsequently coated in oleic acid to confer colloidal stability in organic solvents. The synthesized nanoparticles were encapsulated within poly(lactic acid) via a double-emulsion synthesis. Following the microparticle synthesis, surface functionalization experiments were performed to gain an understanding of the surface chemistry and the potential ability to conjugate biomacromolecules to the particle surface for use in biomedical applications. The ability to specifically bind to histidine-tagged proteins was assessed through the flow cytometry analysis of histidine-tagged green fluorescent protein after incubation with the particles. The magnetic separation of proinflammatory proteins was assessed using enzyme-linked immunosorbent assays to monitor cytokine depletion from known concentrations of tumor necrosis factor-alpha. Lastly, a fluorescently tagged protein molecule was bound to the surface, which allowed the particles to be observed visually under a fluorescent microscope. The particles described here have the potential for numerous biomedical applications including biomacromolecule isolation, cell separation, heavy metal toxin removal, and as a fluorescent imaging modality.