Carbon Dots (CDs) application in biomedicine has been increasing, due to their properties of high photoluminescence, biosafety and low cost, which allows for possible applications in bioimaging and as a drug carrier. However, their synthesis strategies are quite flexible, as tuning reaction precursors and synthesis procedures can lead to an endless number of CDs with distinct properties and applications, which difficult their rational development.

In this work [1,2], we performed a systematic evaluation of the effect of three representative bottom-up strategies (hydrothermal, microwave-assisted, and thermal heating) on the properties of CDs prepared from the same precursors (glucose and urea). In this way, the CDs were thoroughly evaluated in terms of structure, morphology and photoluminescent properties. To screen their potential as drug carriers, the biosafety of these CDs was tested against the normal breast cell line MCF-10A, as drug carriers need to be compatible with healthy cells to minimize harmful side-effects.

The characterization results demonstrated a similar size range and composition for all CDs. While hydrothermal synthesis generates CDs with lower fluorescence and synthesis yields, and present an emission more dependent on surface states, they have the most promising viability profile of MCF-10A when compared with microwave-assisted and thermal-heating CDs, which present better fluorescence properties and better efficiency towards nitrogen-doping.

Our results suggest these CDs have potential to proceed further investigation in animal models as imaging candidates or biosensing tools as well as drug carriers for a future application in medicine.