Molly Stevens and colleagues at Imperial College London have been developing a new type of enzyme test that could aid in the early detection of many diseases, such as HIV and some types of cancer. The test, which uses nanoparticles linked together by peptide groups, is extremely sensitive and can almost detect a single enzyme.
Stevens tells Nature News:
“Normally when you detect a biomarker related to a disease, you’re detecting the presence of that protein, but we’re actually using the protein itself as an inherent amplification step, because each enzyme will cut through many molecules time and time again so you’re getting an amplification of the signal. We can go down to zeptograms per milliliter.”
In a test developed by Stevens for the detection of PSA in men after radical prostectomy, peptide chains were attached to gold particles 10 nanometers wide. The peptide chains link the gold nanoparticles together and the nanoparticle-peptide aggregates are blue in solution. After the addition of nACT-PSA to the solution, peptide bonds are cleaved leaving a positive charge at the end of the peptide chain. Electrostatic repulsion disperses the nanoparticles resulting in a color change, in the case of this test, from blue to red.
Additional peptide chains could be developed for the detection of enzymes associated with other disease states. Stevens and colleagues have already developed peptides specific for HIV proteases and are currently working to find markers of oral cancer in saliva.
The work was presented by Molly Stevens at the American Chemical Society meeting in San Francisco on March 21st.
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