Initial design and physical characterization of a polymeric device for osmosis-driven delayed burst delivery of vaccines

Achieving the combination of delayed and immediate release of a vaccine from a delivery device without applying external triggers remains elusive in implementing single administration vaccination strategies. Here a means of vaccine delivery is presented, which exploits osmosis to trigger delayed burst release of an active compound. Poly(epsilon-caprolactone) capsules of 2mm diameter were prepared by dip-coating, and their burst pressure and release characteristics were evaluated. Burst pressures (in bar) increased with wall thickness (t in mm) following P-burst=131(.)t+3(.)4 (R-2=0.93). Upon immersion in PBS, glucose solution-filled capsules burst after 8.7 +/- 2.9 days. Copolymers of hydrophobic epsilon -caprolactone and hydrophilic polyethylene glycol were synthesized and their physico-chemical properties were assessed. With increasing hydrophilic content, the copolymer capsules showed increased water uptake rates and maximum weight increase, while the burst release was earlier: 5.6 +/- 2.0 days and 1.9 +/- 0.2 days for 5 and 10wt% polyethylene glycol, respectively. The presented approach enables the reproducible preparation of capsules with high versatility in materials and properties, while these vaccine delivery vehicles can be prepared separately from, and independently of the active compound. Biotechnol. Bioeng. 2015;112: 1927-1935. (c) 2015 Wiley Periodicals, Inc.