Polymeric Adjuvants for Vaccine Delivery

Effective and controlled release of active components is crucial in vaccine and drug delivery applications. Previous research has shown that pH and temperature responsive amphiphilic pentablock copolymers and surface eroding polyanhydride nanoparticles show promise as vaccine adjuvants for controlled and sustained release of protein or DNA. This research has further investigated the use of pentablock copolymers and polyanhydride particles in combination to form a hydrogel matrix in order provide controlled and sustained release of model protein ovalbumin (OVA). In order to investigate the effect of structural changes in the hydrogel matrix on the release of OVA, the composition of hydrogel components, loaded OVA amount (free or encapsulated in polyanhydride particles), and molecular weight of pentablock copolymer were varied as parameters. The weight percent of polyvinyl alcohol (PVA) was tested for 20% and 30%. Molecular weight of the pentablock copolymer was also varied giving hydrogels with a low molecular weight (~ 17 kDa) or high molecular weight (~ 25 kDa) copolymer. Lastly, OVA protein was incorporated into hydrogels either in a free form (1 mg/mL solution in phosphate buffered saline (PBS)), encapsulated in polyanhydride nanoparticles (CPTEG:CPH-50:50), or a combination of the two. For all trials, the total OVA amount was maintained at 60 μg per 1 mL volume of hydrogel, and release profiles were observed for 4 days. Overall, release profiles of OVA from hydrogels confirmed the gradual and smooth release of protein with time. They also showed that the amount of protein released from 20% PVA hydrogels was greater than the protein released from 30% hydrogels due to structural differences of the matrices. Lastly, the encapsulated OVA versus free OVA clearly influenced total protein amount released and varied with % PVA and molecular weight of copolymer.