Type I topoisomerases (TOPOI), a potential diagnostic biomarker and a target for chemotherapeutic agents, play essential roles in DNA replication, transcription, chromosome segregation, and recombination. It is essential to develop analytical methods for accurate detection of TOPOI in biological fluids for early diagnosis of diseases. Here we show an assay for TOPOI on the basis of the target-induced self-assembly of graphene oxide (GO) sheets onto hydroxycamptothecin-functionalized upconversion nanoparticles (HCPT-UCNPs). The dipole-dipole coupling of HCPT-UCNPs (donor) and GO (acceptor) regulated by TOPOI enables Förster resonance energy transfer between the donor and the acceptor. Integration of minimal autofluorescence and highly specific affinity into the developed nanosensor allows reliable detection of TOPOI in the nanomolar range with the detection limit of 0.29 nM. The detection of TOPOI in breast cancer cells with recoveries from 96.3 to 103.7% shows the availability of the proposed assay in complicated samples.

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I型拓扑异构酶（TOPOI）是潜在的诊断性生物标志物，也是化学治疗剂的靶标，在DNA复制，转录，染色体分离和重组中起着至关重要的作用。开发准确检测生物流体中TOPOI的分析方法对疾病的早期诊断至关重要。在这里，我们显示了基于目标诱导的自氧化石墨烯（GO）片在羟基喜树碱官能化的上转换纳米颗粒（HCPT-UCNPs）上自组装的TOPOI检测方法。由TOPOI调节的HCPT-UCNPs（供体）和GO（受体）的偶极-偶极耦合使Förster共振能在供体和受体之间转移。将最小的自发荧光和高度特异性的亲和力整合到已开发的纳米传感器中，可在纳摩尔浓度范围内以0.29 nM的检测限可靠地检测TOPOI。乳腺癌细胞中TOPOI的检出率从96.3％增至103.7％，表明该方法可用于复杂样品。

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