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Working together to spot cancer
15 April 2009
UK scientists have designed a method to detect prostate cancer using surface-enhanced resonance Raman scattering. Duncan Graham, from the University of Strathclyde in Glasgow, and his colleagues, combined the technique with a biological method called an enzyme-linked immunosorbent assay, or ELISA, to detect prostate specific antigen, whose elevated levels in serum indicate the cancer's presence.
ELISA is used to detect antigen levels in patients after prostate removal to ensure that all malignant tissue has been removed. Blood serum samples are fixed to a surface then a specific antibody is washed over the surface to bind to any antigen in the samples. Linked to the antibody is an enzyme dyed with a reagent that fluoresces when the antibodies bind to their antigens. This is normally detected by fluorescence spectroscopy, but only one target at a time can be detected due to the large spectral overlap of dyes used for different targets.
Raman scattering shows the presence of prostate specific antigen in enzyme-linked immunosorbent assays
Raman spectroscopy is used to investigate molecular bonding and can provide a unique vibrational 'fingerprint' for target molecules. For molecules that produce weak Raman signals, a highly scattering neighbouring surface such as gold can increase their response - this is surface-enhanced resonance Raman scattering (SERRS).
The team analysed antigen levels in human serum samples using ELISA, but in the final step used gold nanoparticles with SERRS to measure antigen concentration. They were able to detect picograms per millilitre antigen levels, lower than the current limit of nanograms per millilitre in cancer screening. Richard Van Duyne, an expert on SERRS from Northwestern University, Evanston, US, cautions that there are several other competing high-sensitivity approaches to measuring prostate specific antigen, such as surface plasmon resonance, but he agrees that SERRS has a 'bright future in solving biomedical problems'.
Graham says he hopes that in the future, he will be able to use SERRS to detect multiple proteins that indicate the presence of disease.
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Link to journal article
Quantitative SERRS immunoassay for the detection of human PSA
Ross Stevenson, Andrew Ingram, Hing Leung, Donald C. McMillan and Duncan Graham, Analyst, 2009, 134, 842
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