Biosensing and bioimaging of cancer cells with pH and temperature dependent carbon quantum dots

Herein, we report on the preparation, purification, and preliminary characterization of multicolor fluorescent carbon nanoparticles (CNPs) obtained from Over-oxidation of multi-walled carbon nanotubes (MWCNTs). Different CNPs fluoresce with different colors under a single-wavelength excitation. The CNPs are water soluble particles and interestingly enter into the cells without any further functionalization, and they are tractable with using their fluorescence property. Since these carbon nanoparticles do not show cellular toxicity, they have potential to be used for labeling and imaging cells, and also can be used as a drug delivery agent. At the present study, CNPs were prepared after heating MWCNTs with HNO3 and H2SO4 for 72h. After that, the optical properties of the CNPs were considered in their aqueous solutions. Apart from the excitation-dependent photoluminescence behavior, examining CNPs in a broad range of pH showed that the pH value of the solution affected the photoluminescence of the CNPs. So that the fluorescence intensity of the nanoparticles increased significantly upon changing pH from a neutral to either an acidic or a basic solution. In addition, the temperature profile study of photoluminescence property of CNPs showed that photoluminescence of the CNPs was also sensitive to temperature. As it known the cancer cells have higher temperature and acidic condition in compared with normal cells, the mentioned environment-sensitive property of prepared CNPs can be exploited for cancer cells sensing and labeling.