Identifying cancer, with single-cell specificity, by imaging differentially expressed molecular receptors using fluorescent nanocrystals is one of the most promising biomedical applications of nanotechnology.

Bright and tunable

The Amrita group has produced sub-nanometric atomic clusters of gold by stabilizing a few tens of gold atoms (~25–28) within a biopolymer matrix of bovine serum albumin protein. X-ray photoemission spectroscopy and electron microscopy studies carried out in collaboration with Prof. T Pradeep's lab at IIT, Chennai, showed that these gold nanoclusters have an intermediate composition between bulk and molecular regimes. The otherwise overlapped metallic energy bandgap is modified to include discrete electronic states and leads to semiconductor-like phenomena, such as fluorescence.

Although such atomic clusters are generally unstable for any practical applications, the researchers have successfully optimized the reaction conditions for conjugating with molecular receptor specific targeting ligands to identify cancer biomarkers on a malignant cell membrane.

"The development of non-toxic fluorescent nano-biolabels using molecular clusters of metals like gold is a novel concept that opens up new opportunities in biomedical research, particularly in the area of cancer detection and therapy," commented Prof. Manzoor Koyakutty, who led the research at the Amrita Centre.

The cancer specificity is demonstrated using a nasopharyngeal oral cancer cell line KB, which over-expresses folate receptors compared with that of the control.

"The team is currently investigating the in vivo application of these novel fluorescent clusters for simultaneous cancer imaging and therapy including gene-silencing of mutated signaling pathways in cancer," said Prof. Shantikumar Nair, director of the Amrita Centre for Nanoscience and Molecular Medicine.

Full details of the study can be found in the journal Nanotechnology.