Every year pharmaceutical companies use significant resources to mitigate aggregation of pharmaceutical drug products. Specifically, peptides and proteins that have been denatured or degraded can lead to adverse patient reactions such as undesired immune responses. Current methods to detect aggregation of biological molecules are limited to costly and time consuming processes such as high pressure liquid chromatography, ultrahigh pressure liquid chromatography and SDS-PAGE gels. Aggregation of pharmaceutical drug products can occur during manufacturing, processing, packaging, shipment and storage. Therefore, a facile in solution detection method was evaluated to visually detect denatured glutathione peptides, utilizing gold nanoparticle aggregation via 3-Aminopropyltreithoxysilane. Glutathione was denatured using a 70 °C water bath to create an accelerated heat stressed environment. The peptide, gold nanoparticle and aminosilane solution was then characterized via, UV-Vis spectroscopy, FTIR spectroscopy, dynamic light scattering and scanning electron microscopy. Captured images and resulting absorbance spectra of the gold nanoparticle, glutathione, and aminosilane complex demonstrated visual color changes detectable with the human eye as a function of the denaturation time. This work serves as an extended proof of concept for fast in solution detection methods for glutathione peptides that have experienced heat stress.

Utilizing ultraviolet photochemical reduction of gold(III) chloride trihydrate (HAuCl4), a new kind of synthesis of a highly dense gold nanoparticle film on a p-type silicon wafer was conducted. Through scanning electron microscopy and atomic force microscopy, the gold nanoparticle film was confirmed to be 90 nm thick, with an average gold nanoparticle size of 125 nm in diameter. To explore applications in surface enhanced Raman spectroscopy (SERS), a protein model of streptavidin and pegylated biotin functionalized to the surface of gold nanoparticle films was employed. Observations indicate that there was a proximity induced excitation of localized surface plasmons due to the densely packed gold nanoparticle film. Excitation of the localized surface plasmons leading to hot spots of SERS activity on the gold nanoparticle film allowing it to act as an eco-friendly and highly sensitive SERS substrate for biomedical diagnostic applications.

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