Quantum Dot–Peptide Conjugates as Energy Transfer Probes for Sensing the Proteolytic Activity of Matrix Metalloproteinase-14

• Published in: Analytical chemistry (Washington) Vol. 95; no. 5; pp. 2713 - 2722
• Main Authors: Jin, Zhicheng, Dridi, Narjes, Palui, Goutam, Palomo, Valle, Jokerst, Jesse V., Dawson, Phillip E., Sang, Qing-Xiang Amy, Mattoussi, Hedi
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.02.2023
• Subjects: Analytical chemistry; Biomarkers; Breast cancer; Carboxyl group; Chemistry; Conjugates; Diffusion coefficient; Diffusion rate; Dyes; Energy transfer; Fluorescence resonance energy transfer; Fluorescence Resonance Energy Transfer - methods; Matrix metalloproteinase; Matrix Metalloproteinase 14; Matrix metalloproteinases; Metalloproteinase; Peptides; Peptides - chemistry; Polyethylene glycol; Probes; Proteolysis; Quantum dots; Quantum Dots - chemistry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.2c03400

We detail the assembly and characterization of quantum dot (QD)−dye conjugates constructed using a peptide bridge specifically designed to recognize and interact with a breast cancer biomarkermatrix metalloproteinase-14 (MMP-14). The assembled QD conjugates are then used as optically addressable probes, relying on Förster resonance energy transfer (FRET) interactions as a transduction mechanism to detect the activity of MMP-14 in solution phase. The QDs were first coated with dithiolane poly­(ethylene glycol) (PEG) bearing a carboxyl group that allows coupling via amide bond formation with different dye-labeled peptides. The analytical capability of the conjugates is enabled by correlating changes in the FRET efficiency with the conjugate valence and/or QD-to-dye separation distance, triggered and modulated by enzymatic proteolysis of surface-tethered peptides. The FRET probe exhibits great sensitivity to enzyme digestion with sub-nanomolar limit of detection. We further analyze the proteolysis data within the framework of the Michaelis–Menten model, which considers the fact that surface-attached peptides have a slower diffusion coefficient than free peptides. This results in reduced collision frequency and lower catalytic efficiency, k cat/K M. Our results suggest that our conjugate design is promising, effective, and potentially useful for in vivo analysis.