SERS access to tumour cells: Nanoparticle highlights

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  • Published: May 1, 2012
  • Author: David Bradley
  • Channels: Raman
thumbnail image: SERS access to tumour cells: Nanoparticle highlights

Drug binding

A team in China has demonstrated how putative drug compounds bind to human serum albumin (HSA) when bound to silver nanoparticles using surface enhanced Raman scattering (SERS) spectroscopy. The studies help explain how HSA has such great facility to bind and transport a range of compounds. 

A team in China has demonstrated how putative drug compounds bind to human serum albumin (HSA) when bound to silver nanoparticles using surface enhanced Raman scattering (SERS) spectroscopy. The studies help explain how HSA has such great facility to bind and transport a range of compounds.

Wei Zhang and Xueyuan Bai, Daqing Zhao and Yu Zhao of the Changchun University of Chinese Medicine, Yingping Wang of the Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences and Bing Zhao of Jilin University also in Changchun, have investigated two extracts of traditional Chinese medicine, kaempferol and galangin in their quest to exploit SERS.

Kaempferol is a natural flavonol present in many plants, including tea, broccoli, grapefruit, and other fruits and vegetables, it has been investigated in longevity research but has no proven pharmacological applications beyond herbal remedies. Similarly, galangin from the lesser galangal (Alpinia officinarum), is likewise a flavonol and although is present in certain TCM products has not been demonstrated to have any activity other than in preliminary in vitro studies where it was shown to slow the proliferation and growth of breast tumour cells. There is limited evidence that they may have anti-bacterial, anti-inflammatory and anti-viral activity. Nevertheless, natural products with even limited physiological activity might act as useful leads in the quest for novel pharmaceuticals.

Both molecules have a similar chemical skeleton - indeed they are homologues of 2-phenylchromone - and bind to the same site on human serum albumin (HSA). HSA the most abundant protein in blood plasma has a remarkable ability to transport a wide range of compounds including fatty, acids, hormones and pharmaceuticals. However, when adsorbed on to colloidal silver particles, the plane of galangin is distorted while the plane of kaempferol remains unchanged. The team's experiments have allowed them then to investigate the behaviour of these two compounds as they interact with HSA in high concentration.

Tracing SERS

Previous studies have focused on UV-Vis fluorescence or Fourier-transform infrared (FTIR) spectroscopy. The team explains that the SERS spectra were obtainable even at trace concentration under physiological conditions of the model drug compounds because of the enhanced sensitivity compared to the more conventional spectroscopic techniques. The technique reveals how the two molecules bind to HSA revealing that at low galangin concentration the coplanarity of the rings in galangin is distorted but at high concentration the binding is very similar as both molecules lodge in a specific hydrophobic subdomain of the protein regardless of the planarity of their rings or otherwise.

The study demonstrates the power of SERS for these kinds of targeted examinations of pharmaceutical-like compounds in their interactions with a major transport protein in blood. The approach could offer new ways to investigate how drugs are transported that is simply not possible with other spectroscopic techniques.

"Our next step with this research may be more efficiently enhanced substrates used to detect the interactions between pharmaceutical molecules and Human Serum Albumin using surface enhanced Raman spectroscopy in different exciting lines," Yu told SpectroscopyNOW.

Related Links

Spectrochim Acta A: Mol Biomol Spectrosc, 2012, 92, 234-237: "SERS spectroscopy of kaempferol and galangin under the interaction of human serum albumin with adsorbed silver nanoparticles"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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