Poly(lactide)-bl-poly(ethylene glycol) monomethyl ether diblock copolymer (PLA-PEG-OMe) was prepared according to the literature [47] and [48]. Dichloromethane (CH2Cl2), acetonitrile, HPLC grade water, triethylamine (TEA), and trifluoroacetic acid (TFA) were BMN 673 chemical structure purchased from VWR International (Radnor, PA, USA). Dimethylsulfoxide (DMSO) was purchased from Sigma–Aldrich. Fluorescamine was purchased from Tokyo Chemical Industry America (Waltham, MA, USA). Cellgro PBS 1X (PBS) was purchased from Mediatech, Inc. (Manassas, VA, USA). PLGA-R848 polymer was prepared by Princeton Global Synthesis. Polyvinyl alcohol was purchased

from EMD Millipore (Billerica, MA, USA). All of the SVP were prepared using a double emulsion find more water/oil/water system [49]. Briefly, the polymers were prepared at 10% wt/vol in CH2Cl2, and OVA was prepared at 50 mg/mL in PBS. In formulations without OVA, we substituted the OVA aqueous phase with PBS. Emulsification via sonication was performed using a Branson Digital Sonifier model 250 equipped with a model 102 C converter and a 1/8? tapered microtip from Branson Ultrasonics (Danbury, CT, USA). Centrifugation was carried out using a Beckman Coulter J-30I centrifuge with

a JA-30.50 rotor (Beckman Coulter, Brea, CA, USA). The primary emulsion was carried out in a thick walled glass pressure tube with an aqueous to organic phase ratio of 1:5. Following a brief sonication step, Emprove PVA 4–88 aqueous solution was added to the polymer organic solution (at a volume ratio of 3:1 PVA to organic phase), unless vortex mixed, and emulsified by sonication. The resultant double emulsion was then transferred

into a beaker under stirring containing 70 mM phosphate buffer pH 8.0 at a volume ratio of 1 part double emulsion to 7.5 parts buffer. The organic solvent (CH2Cl2) was allowed to evaporate for 2 h under stirring, and the nanoparticles were recovered via centrifugation at 75,600 rcf with two wash steps. PBS was used for the wash solutions and the final resuspension media. The washed SVP suspension was stored at -20 °C. Determination of OVA loading was performed using the fluorescamine test from Udenfriend et al. [50]. R848 and CpG loading were each determined by SVP hydrolysis followed by reversed-phase HPLC analysis. Briefly, nanoparticle solutions were centrifuged, and the pellets were subjected to base hydrolysis to release the adjuvant. R848 hydrolysis was carried out at room temperature using concentrated ammonium hydroxide. Results were quantified from the absorption of R848 at 254 nm using mobile phases comprised of water/acetonitrile/TFA. For CpG analysis, NaOH was used at elevated temperature, with results quantified from the absorption of CpG at 260 nm. The HPLC mobile phases for CpG analysis used acetonitrile/water/TEA. The SVP concentration was determined gravimetrically. Briefly, aliquots of SVP were centrifuged at 108,800 rcf to pellet out the nanoparticles.