Highly tunable protein microspheres for drug delivery

Abstract

It is well-known that protein amyloid aggregation has profound implications in several neurodegenerative diseases. In contrast, a natural role for amyloid structures as protection, adhesion and storage materials in living system is also reported, promoting protein aggregates as an interesting platform for the design of multifunctional biomaterials. Among the broad range of different amyloid structures protein particulates deserve special attention; they are spherical protein aggregates with radius ranging from hundreds of nm to few um which are readily formed in solution at pHs values near the isoelectric point of the protein they are made of. Interestingly, particulate appears to be a generic aggregation state for globular proteins and they are not related to any disease. Moreover, they can be produced from easily available and low-cost proteins. All this makes these microspheres a good candidate for different applications as biomaterials. Here we present an experimental study in which particulates are formed from alpha-lactalbumin, a well-known model protein from bovine milk. Microparticles with modified ability of uptaking small molecules or with modified surface layers can be created allowing material functionalization without using complex chemical procedures. Using a combination of bulk spectroscopies and quantitative fluorescence microscopy methods, we highlighted particulates features both at the level of the structure and size as well as their stability and capability to load molecules. These features can be tuned by modifying solution conditions. Our results show how general laws regulating protein macromolecular assembly can be exploited to create a platform for the development of a new generation of biocompatible materials for drug delivery.