丝氨酸蛋白酶在生物学中起着至关重要的作用，并通过抑制剂（如从扭曲叶豆种子中提取的丝氨酸蛋白酶抑制剂EcTI）来对其活性进行调控，该抑制剂具有抗癌活性。本研究旨在将EcTI与量子点（QDs）共轭，量子点是具有出色光学特性的荧光染料，并研究QDs-EcTI纳米探针与癌细胞的相互作用。共轭物的评估是通过荧光相关光谱学（FCS）和荧光微孔板法（FMA）进行的。还分析了QDs与EcTI相互作用后EcTI的抑制活性。从FCS的结果来看，共轭物的动力学直径约为裸QDs的4倍，这表明共轭成功。FMA进一步证实了这一点，相对荧光度达到了裸QDs或EcTI单独时的约3815%。与QDs相互作用后，EcTI的抑制活性仍然完整。通过流式细胞术分析，大约62%的MDA-MB-231细胞和90%的HeLa细胞被QD-EcTI共轭物标记，表明它们的细胞膜拥有不同的蛋白酶水平，而EcTI对其具有亲和性。总之，QD-EcTI是一种有价值的纳米工具，可使用基于荧光的技术研究该抑制剂与癌细胞之间的相互作用，以揭示癌症生物学中蛋白酶和抑制剂之间错综复杂的动力学关系。版权所有 © 2023. Elsevier B.V. 发表

Serine proteases play crucial biological roles and have their activity controlled by inhibitors, such as the EcTI, a serine protease inhibitor purified from Enterolobium contortisiliquum seeds, which has anticancer activity. This study aimed to conjugate EcTI with quantum dots (QDs), fluorophores with outstanding optical properties, and investigate the interaction of QDs-EcTI nanoprobe with cancer cells. The conjugation was evaluated by fluorescence correlation spectroscopy (FCS) and fluorescent microplate assay (FMA). EcTI inhibitory activity after interaction with QDs was also analyzed. From FCS, the conjugate presented a hydrodynamic diameter about 4× greater than bare QDs, suggesting a successful conjugation. This was supported by FMA, which showed a relative fluorescence of ca. 3815 % for the nanosystem, concerning bare QDs or EcTI alone. The EcTI inhibitory activity remained intact after its interaction with QDs. From flow cytometry analyses, approximately 62 % of MDA-MB-231 and 90 % of HeLa cells were labeled with the QD-EcTI conjugate, suggesting that their membranes have different protease levels to which EcTI exhibits an affinity. Concluding, the QD-EcTI represents a valuable nanotool to study the interaction of this inhibitor with cancer cells using fluorescence-based techniques with the potential to unravel the intricate dynamics of interplays between proteases and inhibitors in cancer biology.Copyright © 2023. Published by Elsevier B.V.