Elastic Bioresorbable Polymeric Capsules for Osmosis-Driven Delayed Burst Delivery of Vaccines

Single-administration vaccine delivery systems are intended to improve the efficiency and efficacy of immunisation programs in both human and veterinary medicine. In this work, an osmotically triggered delayed delivery device was developed that was able to release a payload after a delay of approximately 21 days, in a consistent and reproducible manner. The device was constructed out of a flexible poly(epsilon-caprolactone) photo-cured network fabricated into a hollow tubular shape, which expelled approximately 10% of its total payload within 2 days after bursting. Characterisation of the factors that control the delay of release demonstrated that it was advantageous to adjust material permeability and device wall thickness over manipulation of the osmogent concentration in order to maintain reproducibility in burst delay times. The photo-cured poly(epsilon-caprolactone) network was shown to be fully degradable in vitro, and there was no evidence of cytotoxicity after 11 days of direct contact with primary dermal fibroblasts. This study provides strong evidence to support further development of flexible biomaterials with the aim of continuing improvement of the device burst characteristics in order to provide the greatest chance of the devices succeeding with in vivo vaccine booster delivery.

Automated summary

This study focused on developing an osmotically triggered delayed delivery device to improve the efficiency of single-administration vaccine delivery systems. Factors controlling the release delay were characterized, with adjustments in material permeability and device wall thickness shown to be advantageous for maintaining reproducibility. The photo-cured poly(epsilon-caprolactone) network showed full degradability in vitro and no cytotoxicity after direct contact with dermal fibroblasts for 11 days, supporting further development of flexible biomaterials for in vivo vaccine booster delivery.