Evaluating the Catalytic Activity of the Enzyme Matrix Metalloproteinase (MMP-14, a Cancer Marker) using AuNP−Peptide Conjugates

Proximity-driven interactions between plasmonic nanostructures and fluorescent dyes yield efficient quenching of the dye photoluminescence (PL). This has provided researchers with an effective strategy to develop analytical biosensors.<br/>We report on the use of polyethylene glycol-stabilized gold nanoparticles (AuNPs) covalently coupled to several dye-labelled peptides, as sensitive optically-addressable sensors for determining the catalytic efficiency of the human matrix metalloproteinase-14 (MMP-14), a known molecular marker of select metastatic cancers. We exploit the time-dependent recovery of the dye emission triggered by hydrolysis of the AuNP-tethered peptide-dye by added MMP-14, to extract quantitative analysis of the proteolysis kinetics. Sub-nanomolar limit of detections for the target enzyme has been achieved using these constructs. In addition, we have used conceptual rationales that consider the effects of the AuNP size, reduced Brownian diffusion combined with surface crowdedness of the AuNP-peptide conjugates, compared to peptide only system, to gain additional insights into the kinetic of the PL recovery. We derive enzyme substrate hydrolysis equations and evaluate the catalytic efficiency ([endif]--&gt;) for these platforms. This allowed us to describe the complexity of enzyme activity interacting with nanosurface-bound substrates. Our findings offer a great strategy for the development of highly sensitive and stable biosensors for cancer detection and imaging.