High-throughput analysis of protein stability in polyanhydride nanoparticles

Polyanhydrides are a class of surface eroding biomaterials with applications in vaccine and drug delivery. With the complexity and fragile nature of many protein molecules used in therapeutic treatments and vaccines, devices capable of protecting and preserving the functionality of these proteins are essential. In addition, the half-lives of many vaccine antigens and therapeutic proteins are often short, especially at elevated temperatures. In this work a high-throughput methodology has been developed to rapidly assess the effects of polymer chemistry and the various steps during protein delivery (i.e. encapsulation, storage and release) from polyanhydride nanoparticles on the stability of a model protein, bovine serum albumin. Additional factors including microenvironment pH were also investigated in this multi-parametric approach to evaluate protein stabilization. The findings indicate that the microenvironment pH caused by the acidic polymer degradation products was the most detrimental factor affecting protein stability. Nanoparticles based on 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane and 1,6-bis(p-carboxyphenoxy)hexane maintained protein antigenicity over a range of temperatures for 1 month. These nanoparticles were also successful in preserving protein structure and emerged as viable candidates for use in future drug/protein delivery applications. The combinatorial approach developed in this work allowed for a 25-fold decrease in time and a 10-fold decrease in the amount of materials needed for the investigation of protein stability when compared to conventional methods.