Smart particles of polymer gel that can sieve rare proteins from the blood could allow cancer to be diagnosed at an earlier stage.
Researchers looking for ways to make earlier diagnoses of cancer are concentrating on finding new 鈥渂iomarkers鈥� 鈥� molecules which indicate the presence of tumours before any symptoms show. Among the top candidates are small proteins that tumours shed into the blood. The trouble is that these are present in only minute quantities and so get masked by larger, more common blood proteins, such as albumin.
Researchers can strip the larger proteins from blood samples, but this tends to remove biomarkers as well because they often bind to the larger proteins. 鈥淢ethods that deplete the major proteins throw the baby out with the bath water,鈥� says Emanuel Petricoin of the at George Mason University in Manassas, Virginia, who helped create the smart hydrogel particles.
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The particles, about 1 micrometre in diameter, solve this problem by removing a particular biomarker from blood, and leaving any large proteins behind. They do this because they can be 鈥渂aited鈥� with different chemicals that allow them to trap only certain types of proteins.
Last year the researchers showed that their selectively pulled small proteins out of test solutions (Nano Letters, ). Now they have used the particles to extract a known cancer biomarker from samples of blood serum. 鈥淲e have proved the concept,鈥� says team member Alessandra Luchini.
At the American Association for Cancer Research meeting in San Diego, California, last week, Luchini described how the researchers spiked serum with traces of platelet-derived growth factor (PDGF), bound to albumin. PDGF is a biomarker associated with growth of the blood vessels that feed a developing tumour. The hydrogel particles removed the biomarker from its albumin carrier 鈥� effectively lifting the baby out of the bath water 鈥� and concentrated it from levels that were previously below the limits of detection. The particles also protected PDGF from attack by a protein-digesting enzyme, which is important because blood contains similar enzymes.
Cancer 鈥� Learn more about one of the world鈥檚 biggest killers in our comprehensive special report.
