Fluorescent carbon dots with real-time nucleolus-monitoring capability for gene delivery and biosensing of NO2– and pH

Scheme S1. Schematic diagram of G-CDs’ preparation and applications in nucleolar targeting, gene delivery, and sensing of NO 2 – and pH. • Green fluorescent carbon dots were synthesized from citric acid and 3,5-diaminobenzoic acid. • As-prepared carbon dots have been utilized for targeting nucleolus and carrying exogenous DNA molecule into nucleolus. • The carbon dots have been employed to detect NO 2 – and pH in living cells. To achieve gene therapy, DNA, one of the most commonly used therapeutic nucleic acids, is typically employed to transfer into the nucleous. However, it remains extremely challenging to seek vectors with high transfection efficiency and low toxicity to introduce DNA into the nucleolus. Herein, we have designed and developed green fluorescent carbon dots (G-CDs) for nucleolus targeting, gene delivery, and biosensing of NO 2 – and pH. G-CDs were synthesized by a simple hydrothermal mean using 3,5-diaminobenzoic acid and citric acid as precursors. As-prepared G-CDs not only possess bright green fluorescence with respectable fluorescence quantum yield of 41%, but also exhibit low cytotoxicity and superior biocompatibility. Interestingly, G-CDs display accurate nucleolus targeting characteristic due to the response of G-CDs to DNA in the nucleolus. More unexpectedly, G-CDs could effectively deliver exogenous ROX-labelled DNA into the nucleolus of HeLa cells, which is the first time that fluorescent CDs are used as nanocarriers to transfer DNA to nucleolus. What’s more, G-CDs have been expanded to visually monitor NO 2 – and pH fluctuations in living cells.