Alginate/chitosan microparticles for gastric passage and intestinal release of therapeutic protein nanoparticles.

Enzymes with intracellular activity have significant potential to treat diseases. Protein nanoparticles (NPs) considerably enhance intracellular delivery of enzymes. We have previously shown that a Salmonella effector enzyme, AvrA, delivered by NPs is capable of modulating inflammatory signals in a murine dextran sulfate sodium (DSS) colitis model. The NPs were instilled intrarectally, limiting delivery to the distal colon. Localized intestinal delivery of protein therapeutics via the oral route is a highly attractive alternative approach. However, the harsh conditions in the gastrointestinal tract can severely reduce protein function. The approach described here is to deliver therapeutic protein NPs encapsulated within gastro-protective microparticles (MPs) made from alginate and chitosan that subsequently release NPs in the small intestine and colon. A flow focusing microfluidic device was used to form alginate droplets encapsulating protein NPs. Droplets were then simultaneously crosslinked with calcium and coated with chitosan. Protein NPs encapsulated within crosslinked alginate/chitosan MPs were protected and retained their activity after incubation in simulated gastric fluid (SGF). Subsequent incubation in simulated intestinal fluid (SIF) induced release of bioactive protein NPs. Oral administration of AvrA NPs encapsulated in alginate/chitosan MPs delivered protein to intestinal epithelia and reduced clinical and histological scores of inflammation in a murine DSS-induced colitis model. Altogether, NPs in alginate/chitosan MPs are a potential oral delivery vehicle for protein therapeutics.