Biodegradable Nanoparticles as Vaccine Adjuvants and Delivery Systems: Regulation of Immune Responses by Nanoparticle-Based Vaccine - Polymers in Nanomedicine - page 55

g -PGA is a very promising biodegradable polymer that is produced by various
strains of Bacillus . Potential applications of g -PGA as thickener, cytoprotectant,
humectant, biological adhesive, fluoculant, or heavy metal absorbent, etc. have
been reported. This review describes the preparation of polymeric nanoparticles
composed of g -PGA and their pharmaceutical and biomedical applications. The
production of g -PGA has already been established on the industrial scale because it
can be produced easily and extracellularly in high yield by culture of bacteria in a
fermenter. Moreover, various molecular weights of g -PGA can be obtained com-
mercially. g -PGA by itself is shown to be weakly or non-immunogenic and safe.
Amphiphilic g -PGA nanoparticles have potential use as a new adjuvant instead of
alum, and the nanoparticles are very suitable for use as vaccine delivery systems.
These systems are expected to be introduced into clinical studies in the near future.
There is a growing interest in identifying the relationship between the size of
nanoparticles and their adjuvant activities, but the results from recent studies
remain controversial. Many investigators are in agreement that the size of the
particles is crucial to their adjuvant activities. Some factors that may affect
the conflicting findings include: (1) the polymeric materials used to form the
nanoparticles, (2) the nature of the antigen used, (3) the methods of antigen
conjugation, and (4) the immunization route. To clarify the influence
of nanoparticles on adjuvant activity, there is a need to more comprehensively
compare immune responses induced by precisely size-controlled nanoparticles
prepared with the same materials and loaded with the same antigens by the proper
method.
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