Indian scientists have discovered how everyday molecules like amino acids and salts influence the behaviour of gold nanoparticles, a finding that could pave the way for more reliable biosensors, improved diagnostic tools and advanced drug delivery systems.
Gold nanoparticles are widely used in optical technologies because of their unique interaction with light. Their colour and optical properties change depending on whether they remain isolated or form clusters. While this makes them useful in biosensors and imaging, uncontrolled clustering has posed a longstanding challenge for researchers.
A team from the S N Bose National Centre for Basic Sciences, Kolkata — an autonomous institution under the Department of Science and Technology (DST) — has now identified how to regulate this process.
Led by Prof. Manik Pradhan, the scientists experimented with two molecules: Guanidine Hydrochloride (GdnHCl), a strong salt commonly used in labs, and L-Tryptophan (L-Trp), an amino acid naturally found in proteins and linked with relaxation and sleep.
When GdnHCl was introduced, gold nanoparticles rapidly clumped together into dense clusters. However, the presence of L-Trp alongside GdnHCl disrupted this process, resulting instead in looser, branched structures — a phenomenon the researchers termed “frustrated aggregation.”
“This is like the nanoparticles want to stick together tightly, but the amino acid keeps interfering,” the study noted.
The team — comprising Soumyadipta Chakraborty, Dr Jayeta Banerjee, Indrayani Patra, Dr Puspendu Barik, and Prof. Pradhan — employed Evanescent Wave Cavity Ringdown Spectroscopy (EW-CRDS), a cutting-edge optical technique, to monitor the changes in real time. The method revealed that L-Trp stabilises guanidinium ions, slowing aggregation and allowing more open, stable structures to form.
The study, published in the journal Analytical Chemistry, offers fresh insights into fundamental nanoscience and demonstrates how advanced optical tools can probe delicate processes with unprecedented sensitivity.
