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Multiple sclerosis (MS) is an autoimmune, demyelinating disease of the central nervous system that can cause loss of motor function and is thought to result, in part, from chronic inflammation due to an antigen-specific T cell immune response. Current treatments suppress the immune system without antigen specificity, increasing the risks of cancer, chronic infection, and other long-term side effects. In this study, we show treatment of experimental autoimmune encephalomyelitis (EAE), a model of MS, by coencapsulating the immunodominant peptide of myelin oligodendrocyte glycoprotein (MOG) with dexamethasone (DXM) into acetalated dextran (Ac-DEX) microparticles (DXM/MOG/MPs) and administering the microparticles subcutaneously. The clinical score of the mice was reduced from 3.4 to 1.6 after 3 injections 3 days apart with the coencapsulated microparticulate formulation (MOG 17.6 μg and DXM 8 μg). This change in clinical score was significantly greater than observed with phosphate-buffered saline (PBS), empty MPs, free DXM and MOG, DXM/MPs, and MOG/MPs. Additionally, treatment with DXM/MOG/MPs significantly inhibited disease-associated cytokine (e.g., IL-17, GM-CSF) expression in splenocytes isolated in treated mice. Here we show a promising approach for the therapeutic treatment of MS using a polymer-based microparticle delivery platform.

We propose the use of a new biopolymer, acetalated dextran (Ac-DEX), to synthesize porous microparticles for pulmonary drug delivery. Ac-DEX is derived from the polysaccharide dextran and, unlike polyesters, has tunable degradation from days to months and pH neutral degradation products. Ac-DEX microparticles fabricated through emulsion techniques were optimized using a variety of postprocessing techniques to enhance the respirable fraction for pulmonary delivery. Tangential flow filtration resulted in a maximum 37% respirable fraction for Ac-DEX porous microparticles, compared to a 10% respirable fraction for poly(lactic-co-glycolic acid) (PLGA) porous microparticles. Ac-DEX microparticles were of an optimum diameter to minimize macrophage clearance but had a low enough theoretical density for deep lung penetration. Transepithelial electrical resistance (TEER) measurements showed that the particles did not impinge on a monolayer of lung epithelial cells in either air or liquid conditions. Also, the release of the chemotherapeutic camptothecin was shown to be tunable depending on Ac-DEX degradation time and molecular weight, and drug release was shown to be bioactive over a range of concentrations. Our results indicate that both release kinetics and fraction of burst release of drug from Ac-DEX porous microparticles can be tuned by simply changing the Ac-DEX polymer properties, affording a large range of formulation options for drug delivery to the pulmonary cavity. Overall, Ac-DEX porous microparticles show promise as an emerging carrier for pulmonary delivery of drugs to the alveolar region of the lung, particularly for the treatment of lung diseases.

Non-ionic surfactant vesicles, or SPANosomes (SPs), comprised of cationic lipid and sorbitan monooleate (Span 80) were synthesized and evaluated as siRNA vectors. The SPs had a mean diameter of less than 100 nm and exhibited excellent colloidal stability. The SP/siRNA complexes possessed a slightly positive zeta potential of 12 mV and demonstrated a high siRNA incorporation efficiency of greater than 80%. Cryogenic transmission electron microscopy (cryo-TEM) imaging of the SP/siRNA indicated a predominantly core-shell structure. The SP/siRNA complexes were shown to efficiently and specifically silence expression of both green fluorescent protein (GFP) (66% knockdown) and aromatase (77% knockdown) genes in breast cancer cell lines. In addition, the cellular trafficking pathway of the SP/siRNA was investigated by confocal microscopy using molecular beacons as probes for cytosolic delivery. The results showed efficient endosomal escape and cytosolic delivery of the siRNA cargo following internalization of the SP/siRNA complexes. In conclusion, Span 80 is a potent helper lipid and the SPs are promising vehicles for siRNA delivery.

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