Peer reviewed article authored by (Chang HI, Yeh MK). Read article or submit your manuscript for publishing.

Vaccination, which provides effective, safe infectious disease protection, is among the most important recent public health and immunological achievements. However, infectious disease remains the leading cause of death in developing countries because several vaccines require repeated administrations and children are often incompletely immunized. Microsphere-based systems, providing controlled release delivery, can obviate the need for repeat immunizations. Here, we review the function of sustained and pulsatile release of biodegradable polymeric microspheres in parenteral and mucosal single-dose vaccine administration. We also review the active-targeting function of polymeric particles. With their shield and co-delivery functions, polymeric particles are applied to develop single-dose and mucosally administered vaccines as well as to improve subunit vaccines. Because polymeric particles are easily surface-modified, they have been recently used in vaccine development for cancers and many infectious diseases without effective vaccines (e.g., human immunodeficiency virus infection). These polymeric particle functions yield important vaccine carriers and multiple benefits.

Peer reviewed article authored by (Hsieh DS, Lu HC, Chen CC, Wu CJ, Yeh MK). Read article or submit your manuscript for publishing.

Fluorescein isothiocyanate-conjugated bovine serum albumin (FITC-BSA)-loaded polyethylene glycol (PEG)-modified liposomes and lipoparticles with high protein entrapment were developed. The lipid formula of the liposomes contained PEGylated lipids and unsaturated fatty acids for enhancing membrane fluidity and effective delivery into cells. The preparation techniques, lipid content, and PEG-modified lipoparticle ratios were evaluated. The PEG-modified lipoparticles prepared by ethanol injection extrusion (100 nm pore size) achieve a population of blank liposomes with a mean size of 125 ± 2.3 nm and a zeta potential of —12.4 ± 1.5 mV. The average particle size of the PEG-modified lipoparticles was 133.7 ± 8.6 nm with a zeta potential of +13.3 mV. Lipoparticle conformation was determined using transmission electron microscopy and field-emission scanning electron microscopy. The FITC-BSA encapsulation efficiency was dramatically increased from 19.0% for liposomes to 59.7% for lipoparticles. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results confirmed the preparation process, and an 8-hour leaching test did not harm the protein structure. Once prepared, the physical and chemical stability of the PEG-modified lipoparticle formulations was satisfactory over 90 days. In vitro retention tests indicated that the 50% retention time for the protein-containing lipoparticles was 7.9 hours, substantially longer than the liposomes at 3.3 hours. A Caco-2 cell model was used for evaluating the cytotoxicity and cell uptake efficiency of the PEG-modified lipoparticles. At a lipid content below 0.25 mM, neither the liposomes nor the lipoparticles caused significant cellular cytotoxicity (P < 0.01) and FITC-BSA was significantly taken up into cells within 60 minutes (P < 0.01).

Yersinia pestis F1 antigen-loaded poly(DL-lactide-co-glycolide)/polyethylene glycol (PEG) (PLGA/PEG) microspheres were produced using a water-in-oil-in-water emulsion/solvent extraction technique and assayed for their percent yield, entrapment efficiency, surface morphology, particle size, zeta potential, in vitro release properties, and in vivo animal protect efficacy. The Y. pestis F1 antigen-loaded microspheres (mean particle size 3.8 µm) exhibited a high loading capacity (4.5% w/w), yield (85.2%), and entrapment efficiency (38.1%), and presented a controlled in vitro release profile with a low initial burst (18.5%), then continued to release Y. pestis F1 antigen over 70 days. The distribution (%) of Y. pestis F1 on the microspheres surface, outer layer, and core was 3.1%, 28.9%, and 60.7%, respectively. A steady release rate was noticed to be 0.55 µg Y. pestis F1 antigen/mg microspheres/day of Y. pestis F1 antigen release maintained for 42 days. The cumulative release amount at the 1st, 28th, and 42nd days was 8.2, 26.7, and 31.0 µg Y. pestis F1 antigen/mg microspheres, respectively. The 100 times median lethal dose 50% (LD₅₀) of Y. pestis Yokohama-R strain by intraperitoneal injection challenge in mice test, in which mice received one dose of 40 µg F1 antigen content of PLGA/PEG microspheres, F1 antigen in Al(OH)₃, and in comparison with F1 antigen in Al(OH)₃ vaccine in two doses, was evaluated after given by subcutaneous immunization of BALB/c mice. The study results show that the greatest survival was observed in the group of mice immunized with one dose of F1 antigen-loaded PLGA/PEG microspheres, and two doses of F1 antigen in Al(OH)₃ vaccine (100%). In vivo vaccination studies also demonstrated that F1 vaccines microspheres had a protective ability; its steady-state IgG immune protection in mice plasma dramatic increased from 2 weeks (18,764±3,124) to 7 weeks (126,468±19,176) after vaccination. These findings strongly suggest that F1-antigen loaded microspheres vaccine offer a new therapeutic strategy in optimizing the vaccine incorporation and delivery properties of these potential vaccine targeting carriers.