Quantum Dot-Peptide Nanoassembly on Mesoporous Silica Nanoparticle for Biosensing

Abstract

Quantum dots (QDs) are powerful luminescent probes for detecting single-molecules and imaging live cells. Despite several reports on bioimaging and biosensing applications of QDs, controlled and targeted detection of biomolecules using quantum dots is an ongoing challenge. When a QD is conjugated with an ideal chromophore, which can be a fluorescent or a non-fluorescent dye molecule, QD luminescence can be quenched by Förster resonance energy transfer (FRET) to the quencher dye. However, the photoluminescence of QD can be recovered upon on-demand release of the quencher. Our study focuses on quenching of QD photoluminescence after conjugation with a non-fluorescent dye molecule, black hole quencher 1 (BHQ-1), intermediated with a molecular sensing target peptide GPLG↓VRGK. Based on steady-state and time-resolved photoluminescence measurements of QD and the QD-peptide-BHQ-1 sensor assemblies, we attribute the quenching of photoluminescence intensity and lifetime to FRET from the QD to BHQ-1molecules. Here the intermediate peptide GPLG↓VRGK can be cleaved by matrix metalloproteinase-2 (MMP-2), an enzyme that is upregulated in cancer cells extra cellular matrix (ECM), at its Gly and Val region shown by the down headed arrow. Here the QD-pep-BHQ-1 conjugate detected the MMP-2 presence at the extra cellular matrix of H1299 cancer cells. Further the QD-pep-BHQ-1 molecules were conjugated at the surface of a mesoporous silica nanoparticle (MSN) scaffold to localize maximum target peptide in a nanospace volume for the future αvβ3 integrin receptor targeted detection of MMP-2. The luminescence quenching of MSN-QD-pep-BHQ-1 conjugates were analyzed with time resolved photoluminescence measurement.