Tailoring of a bionic bifunctional cellulose nanocrystal-based gold nanocluster probe for the detection of intracellular pathological biomarkers

Gold nanoclusters with excellent fluorescence intensity, stability and biocompatibility have promising application prospects in the field of detection. Inspired by the growth behavior of sea squirts adhered to ropes, a novel bionic bifunctional cellulose nanocrystal (CNC)-based gold nanocluster probe was effectively constructed by directionally growing gold nanoclusters on CNCs modified with a specific DNA sequence. The constructed probe has excellent fluorescence properties and stability. The "ON or OFF" conversion mode of fluorescence was designed to detect different pathological markers in cells. In the "ON" mode, the probe readily combined with various sulfhydryl group containing markers (acetylcholinesterase, cysteine and glutathione) to produce fluorescence quenching and realize detection, the corresponding detection limits were as low as 0.015 mU/mL, 0.028 μM and 0.228 μM, respectively. Interestingly, the fluorescence of the probe could be regulated to the OFF mode via the assembly of the graphene oxide structure in accordance with Förster resonance energy transfer. The fluorescent probe with OFF mode could selectively recognize the carcinoembryonic antigen biomarker of malignant tumours via fluorescence enhancement, and its limit of detection was as low as 0.54 ng/mL. The as-developed novel strategy has positive significance for the early diagnosis of malignant tumours.