S,O-doped carbon nitride as a fluorescence probe for the label-free detection of folic acid and targeted cancer cell imaging

A novel nanoprobe based on S,O-doped carbon nitride quantum dots (S,O-CNQDs) was designed and synthesized. The as-prepared S,O-CNQDs exhibits good biocompatibility and strong fluorescence at excitation 360 nm. It is found that folic acid (FA) could efficiently quench the flu-orescence of S,O-CNQDs. The obtained S,O-CNQDs is capable of acting as a sensitive and selective probe for FA detection in the range 5.0-83.3 lM with a detection limit of 90 nM. The as-prepared probe has been successfully utilized for the detection of FA in various real samples with satisfactory recoveries (98.8-107 %) and small relative standard deviation (<5%). The reaction mechanism between S,O-CNQDs and FA has been discussed. In addition, FA-S,O-CNQDs formed through a classical cross-linking reaction between FA and S,O-CNQDs easily accesses and penetrates into HepG2 cells with high folate receptors expression. FA-S,O-CNQDs with low cytotoxicity and good biocompatibility shows great potential in FA detection and targeted imaging of cancer cells. (c) 2022 The Authors. Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

A novel nanoprobe based on S,O-doped carbon nitride quantum dots was synthesized and demonstrated for the detection of folic acid (FA). The nanoprobe showed good biocompatibility and strong fluorescence at 360 nm excitation. It exhibited high sensitivity and selectivity towards FA in the concentration range of 5.0-83.3 μM, with a detection limit of 90 nM. The nanoprobe was successfully applied for FA detection in real samples with satisfactory recoveries and low relative standard deviation. The FA-S,O-CNQDs formed through a classical cross-linking reaction showed great potential in FA detection and targeted imaging of cancer cells.