Enzyme Catalyzed Alginate Nanogels for Drug Delivery

Developing nanoscale carriers for the delivery of therapeutics is an important topic of investigation in current biomedical research. As opposed to traditional drug delivery systems, nanoscale systems offer enhanced tissue and cell permeation in addition to reducing drug elimination from the body. Biological based therapeutics such as DNA and proteins are now widely employed in medical applications and research has focused on using nanoscale drug delivery systems to administer these more effectively. Current synthesis methods of nanoscale biotherapeutic carriers face significant challenges. Among these are creating carriers with: sizes between 10-200 nm, low polydispersity, and non-cytotoxic materials. In this thesis, a nanocarrier synthesis method that meets these criteria is demonstrated using enzymatic methods to create monodisperse carriers that are 100 nm or less in size from entirely non-synthetic components. In the past, enzymatic synthesis of carriers has been limited due to the sensitivity and specificity of enzyme reactions to the presence of certain functional groups, substrates, temperatures, and pH’s. In the following work, we use the enzyme laccase to serve as a catalyst for the growth of hydrogel nanoparticles. It is known that laccase has the ability to convert iron (II) cations to iron (III) cations. Additionally, the biologically derived polymer called alginate exhibits crosslinking in the presence of iron (III) to form an aqueous polymer gel matrix. Using these three components, alginate polymer, laccase enzyme, and iron (II) sulfate, nanoscale hydrogel carriers were synthesized. Furthermore, we found that the size and polydispersity of the particles could be controlled through limitation of the enzyme activity. Dynamic light scattering, UV-Visible spectroscopy, Small Angle Neutron Scattering, and Atomic force microscopy were used to characterize the particle’s size, dispersity, growth rate, and growth mechanism. Using 0.36 mM iron (II) sulfate, monodisperse particles with a radius of 40 nm were formed. Increasing iron concentration increased the size and speed of the formation of the particles which resulted in their aggregation after reaching 100 nm in size. Here we have achieved simple synthesis of biodegradable nanogel particles with a hydrodynamic radius of 100 nm and below whose size can be tuned and exhibits low polydispersity.