Surface and Rheological Effects of Mucus/Mucin Coupled with Chitosan-Coated Gold Nanoparticles

We have examined surface-functionalized gold nanoparticles (Au NPs) within mucin/mucus matrices to gain a better understanding of the mechanical and chemical interactions, as these systems are model nanoparticle-based therapeutics.  Specifically, glycol-chitosan (GC) surface moieties were added to the Au NPs using a one-pot synthesis method where glycol-chitosan acts as both a stabilizer and a reducing agent. Particle size distributions, stability, and structure of the ‘as synthesized’ Au NPs and glycol-chitosan modified Au NPs (GC-Au) were measured using dynamic light scattering (DLS) and ultraviolet visible spectroscopy (UV-Vis). After confirming the successful synthesis of GC-Au nanoparticles, mucin aliquots were added to the GC-Au nanoparticle solution.  Changes in the particle size were monitored using DLS to examine complex formation and binding interactions between the GC-Au nanoparticles and mucin. By varying pH, complexation time, concentration, and temperature, the stability of the mucin-chitosan Au nanoparticle complexes was evaluated.  Morphological characteristics of these hybrid systems were examined using TEM, and net-surface charge effects of the nanoparticle interacting with mucin was characterized by z-potential measurements. In addition, we have examined the bulk rheological effects for synthetic mucus solutions—based on pig gastric mucin (PGM) and different stabilizers—in response to GC-Au nanoparticle addition at different concentrations. This work provides foundational information on interactions between surface-functionalized nanoparticles and biopolymers, which is important in developing next-generation biomedical therapeutics and theranostics.