Synthesis of gold nanoparticles for biomacromolecular recognition
Gold nanoparticles have been widely known for many centuries. Until the 1990’s, gold nanoparticles were able to be synthesized in aqueous solutions with little functionalization of the nanoparticle due to the synthetic procedures that existed. In 1994 a synthetic technique was developed by Brust-Schiffrin which provided for the production of gold nanoparticles that could be easily obtained. Murray further developed this synthesis to provide for nanoparticles with many different functional groups and with various sizes. These nanoparticles synthesized through this method would afford for systems that would be capable of providing for biomacromolecular surface recognition; where the characteristics needed for surface recognition include the need for a large complementary surface with multiple recognition units for specificity.
Using the Brust-Schiffrin and Murry techniques we synthesized a gold nanoparticle which was functionalized with mercaptoundecanoic acid. This nanoparticle provided a water soluble nanoparticle which was easily synthesized and had pH solubility dependence. This nanoparticle was used effectively to bind α-chymotrypsin.
The mercaptoundecanoic acid functionalized nanoparticle when bound to the enzyme afforded a denatured chymotrypsin which was released by the addition of a surfactant with some activity towards the substrate, succinyl-Phe-Ala- p-nitroanilide. It was found that this released enzyme had new specificity towards other substrates with limited or no activity on substrates with larger peptide side chains. The released enzyme was observed to have the most activity towards the substrate, benzoyl-Tyr-p-nitroanilide.
A gold nanoparticle was synthesized that was functionalized by 2-(10-mercapto-decyl)-malonic acid. This provided for a nanoparticle that bound α-chymotrypsin and effectively inhibited the enzyme with little denaturation of the enzyme. The electrostatic nature of this complexation was probed by observing the effect of NaCl concentration upon the binding of the nanoparticle to the enzyme. Higher salt concentrations were observed to completely disrupt the binding, thus affording no inhibition of the enzyme’s activity. The nanoparticle-enzyme preformed complex was observed to be completely disrupted upon the addition of high salt concentrations. The released enzyme was observed to have 90% of the activity of native chymotrypsin.