Carbon dots (C-dots) are light-emitting (luminescent) nanoparticles that can be used to track biological processes inside cells. They are less toxic than similar alternatives, making them more suitable for use in live biological systems, but the light-emitting properties of those currently made are not ideal.

Typical transmission electron microscopy (TEM) images of Carbon dots. © IOP / STAM

Typical transmission electron microscopy (TEM) images of Carbon dots. © IOP / STAM

A variety of approaches have been used to make C-dots, but most require coating of the particles with other molecules to achieve useful luminescence. Now, work led by Amita Pathak at the Indian Institute of Technology has produced water-soluble C-dots that selectively emit light across the entire visible range without any surface coating.

The researchers produced these C-dots by breaking down the carbohydrate dextrin with microwaves.

The resulting C-dots emitted different colours of light when excited by specific wavelengths, even without coating them. Exactly how this multi-coloured luminescence arises is unclear, but it allows precise control of the light emission that can be tailored to specific needs.

To ensure that the C-dots were not toxic, the team added different concentrations of the nanoparticles to cultured cells. After three days, they determined how many cells had survived. Increasing concentrations of C-dots made little difference to cell survival, showing that the C-dots are not toxic and could therefore be used in live tissue.

The properties of these new C-dots make them ideal for a variety of bioimaging applications and for medical diagnostics. The same researchers have already begun to look at how they may be used to investigate interactions between drugs and cells.

The carbogenic material changes structure with ageing time after centrifugal separation. Various shapes such as star, flower, flower garland, cluster of flower garlands and leaf have been observed after ageing for 16, 24, 48, 62 and 120 hours © IOP / STAM

The carbogenic material changes structure with ageing time after centrifugal separation. Various shapes such as star, flower, flower garland, cluster of flower garlands and leaf have been observed after ageing for 16, 24, 48, 62 and 120 hours © IOP / STAM

References:

Nagaprasad Puvvada, B N Prashanth Kumar, Suraj Konar, Himani Kalita, Mahitosh Mandal and Amita Pathak (2012) “Synthesis of biocompatible multicolor luminescent carbon dots for bioimaging applications” Science and Technology of Advanced Materials Vol. 13 p. 045008

DOI: http://dx.doi.org/10.1088/1468-6996/13/4/045008

Download the original paper in PDF format here.

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