doi:10.1038/nindia.2017.40 Published online 15 March 2017
By heating dried mango leaf extract, researchers have synthesized fluorescent graphene quantum dots that can be used for bioimaging and as intracellular temperature-sensing probes1.
Existing fluorescent materials, such as organic dyes, metal clusters and quantum dots, are toxic to biological cells and unstable when exposed to light.
In search of a biocompatible fluorescent material, scientists led by Rohit Srivastava from the Indian Institute of Technology (IIT) in Mumbai prepared fluorescent graphene quantum dots by heating dried mango leaf extract in a domestic microwave oven. They then explored the quantum dots’ potential for bioimaging and temperature-sensing in specific mice cells.
When incubated with the mice cells, the quantum dots easily permeated the cell membrane without disrupting the proliferation and viability of the cells. This shows that the dots are biocompatible.
The dots’ fluorescence intensity peaked at 25oC and then decreased when the temperature rose to 45oC. The dots lost 95% of their fluorescence intensity within a temperature change of 20°C, indicating their suitability for detecting minute temperature variation inside cells.
The quantum dots also retained their fluorescence intensity up to fifth cycle of temperature-variation experiments.
“Since the quantum dots emit red light, this property could potentially be exploited to make light-emitting diodes from a natural source like mango leaves. Such diodes can function as temperature sensors,” says lead author, Mukesh Kumar Kumawat.
1. Kumawat, M. K. et al. Graphene quantum dots from Mangifera indica: application in near-infrared bioimaging and intracellular nanothermometry. ACS. Sustainable. Chem. Eng.5, 1382-1391(2017)