Researchers in Ireland have made nanoscale crystals that can be used to image components inside living cells. Yurii Gun'ko and colleagues from the University of Dublin prepared crystals of cadmium telluride (CdTe) that can enter white blood cells and illuminate the cell machinery. 

Nano-sized CdTe crystals are examples of quantum dots. Quantum dots (QDs) are fluorescent semiconductor nanocrystals, which give off light at particular wavelengths, depending on their size and composition. Gun'ko's group wanted to develop QDs that could be used to image cells. To do this they fine tuned the known method for making CdTe QDs so that they emitted more light. 

Traditional methods for detecting biological compounds involve tagging them with radioactive markers or fluorescent dyes. These tags have complications, such as high cost and deteriorating activity on prolonged exposure to light. In contrast, QDs are relatively stable to light and offer considerable advantages for bio-labelling, said Gun'ko.

The enhanced light emission of Gun'ko's QDs and their potential use in specific bio-labelling was down to the improved synthetic method adopted by the group. Organic sulfur-containing ligands were attached to the surface of the QDs, to improve their stability inside living cells. Also, the QD surfaces were patterned by a technique called photoetching which increased their fluorescence. 

Gun'ko said that the research demonstrates the great potential of CdTe QDs as probes for in vitro labelling in living cells. This will be especially important in medicine for the detection of specific biomolecules and cell components, he said. 'In the long term this research might enable us to understand pathways of penetration by small toxic particles and viruses into immune cells and help in diagnostic recognition and treatment of cancer, HIV and other diseases.'

Katherine Vickers