Fluorescent Mn:ZnCdS@ZnS and CdTe Quantum Dots Probes on SiO₂ Microspheres for Versatile Detection of Carcinoembryonic Antigen and Monitoring T4 Polynucleotide Kinase Activity

Versatile fluorescent quantum dots (QDs) probes on SiO₂ microspheres were prepared and used for detection of carcinoembryonic antigen (CEA) and monitoring T4 polynucleotide kinase (PNK) activity by integrating with amplification strategy. The highly fluorescent Mn:ZnCdS@ZnS and CdTe QDs showed different emission peaks. The amino-modified SiO₂ microspheres with good morphology and no fluorescence interference were designed to link DNA and fabricate multiple branched QDs probes. First, CEA-induced target recycle amplification technique was combined with the Mn:ZnCdS@ZnS QDs labeled P2 signal probe for sensitive detection of CEA. Then, the formed DNA S1–DNA3 double strands further polymerized and proceeded exonuclease-cleavage reaction in the presence of T4 PNK, the released DNA fragments were used to trigger assembly of multibranched CdTe QDs-DNA signal probe (P1) by hybridization chain reaction (HCR), and achieved a greatly amplified fluorescence detection of PNK. The detection limits for CEA and PNK were 0.1 pg/mL and 0.001 U/mL, which was comparable to the reported methods. It is for the first time that the multiple branched QDs probes was coupled with HCR and cycling amplification strategy for versatile fluorescence detection of CEA and PNK activity. It shows great potential for early clinical diagnosis of cancer and the nucleotide kinase-target drug discovery.