Quantum dots ate the small semiconductor nanoparticles that become brightly fluuorescent with sharply defined colours, giving tremendous promise as biomedical imaging agents but inclusive of one problem-most of them are made from cadmium and selenium which are potentially hazardous materials. However a collaborative effort between reasearchers of Stanford University and Xiamen University in China has been able to produce a stable ,biocompatibel quantum that appears to have the desired set of properties needed for bio-medical imaging.
The team led by Sanjiv Gambhir School of Medicine and Zen Cheng of Xiamen University reported their work in the journal Nano Letters.
The Quantum Dot
The investigators searched for semiconducting materials that had the desired optical properties of fluorescing at the near – infrared region of the spectrum and yet were not potentially toxic. To solve the biocompability problem.They created a nanoparticle with an indium phosphide core and a zinc sulphide shell.The resulting quantum dots fluoresced brightly at 710 nanometers, a wavelenth of light that can be seen within the body as they can pass through biological tissues.The researchers,to improve the pharmacological properties of the dots,they coated the nanoparticles with biocompatible polymer known as dendrimer. This polymer coating also served as a attachment point for a 3 amino acid peptide arginine,i.e, aspartic acid-also known as RGD, that attacks and targets many types of tumours.
Working of the quantum dot
By experiments with cancer cells and tumor-bearing animals , the researchers demonstrated that these nanoparticles clearly imaged tumors known to bind to RGD. Because of their small size, the quantum dots entered the tumors through the leaky blood vessels that surround tumors. Biodistribution tests showed that approximately 60 percent of an injected dose of the new quantum dots was cleared from the body within a day, and that 100 percent clearance was achieved within one week. And most important thing is that animals which are dosed with these nanoprobes do not suffer any kind of side-effects.
(Source-Physorg)
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