Polydopamine-Coated Porous Microspheres Conjugated with Immune Stimulators for Enhanced Cytokine Induction in Macrophages

Polydopamine-coated porous microsphere (PPM) is investigated as a simple and versatile immobilization strategy for immune-stimulating biomolecules to enhance delivery efficiency and immune-stimulating effects such as cytokine induction in macrophages. The PPMs, with diameters of about 2 mu m, exhibit simultaneous and efficient incorporation of biomolecules (nucleotides and proteins), which is comparable to that achieved using microspheres carrying biomolecules internally by virtue of their porous structure. Ovalbumin-conjugated PPMs are internalized into macrophages efficiently and selectively via the phagocytic pathway, without any noticeable toxicity. Internalized CpG oligodeoxynucleotide (ODN)-conjugated PPMs (PPM-CpG) greatly enhance the induction of selected cytokines (TNF-alpha and IL-6) in RAW 264.7 cells compared to that by the soluble CpG ODN and ionic complexes. Therefore, PPMs generated in this study may serve as effective carriers of immunestimulating biomolecules such as diverse toll-like receptor agonists.