Aptamer-capped nanocrystal quantum dots: a new method for label-free protein detection

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Biochemistry

Background:

• Quantum dots (QDs) are semiconductor nanocrystals with tunable optical properties.
• Aptamers are short DNA or RNA sequences that can bind to specific targets.
• Developing sensitive and selective protein detection methods is crucial for diagnostics.

Purpose of the Study:

• To develop a novel biosensor for protein detection using aptamer-functionalized quantum dots.
• To investigate the mechanism of fluorescence quenching upon protein binding.
• To assess the selectivity and sensitivity of the developed QD-based sensor.

Main Methods:

• Synthesis of water-soluble, near-infrared emitting lead sulfide (PbS) quantum dots (QDs).
• Functionalization of QDs with thrombin-binding aptamers, preserving their quadruplex structure.
• Characterization of QD-protein interactions using fluorescence spectroscopy to observe quenching.
• Evaluation of detection limit and selectivity in the presence of interfering proteins.

Main Results:

• Aptamer-capped PbS QDs exhibited fluorescence around 1050 nm.
• Selective binding of thrombin to aptamer-functionalized QDs resulted in fluorescence quenching.
• Thrombin detection was achieved within 1 minute with a detection limit of approximately 1 nM.
• The sensor demonstrated high selectivity, unaffected by high concentrations of other proteins.

Conclusions:

• Aptamer-capped near-infrared PbS QDs enable rapid and label-free detection of target proteins via selective charge transfer.
• The QD-aptamer complex maintains structural integrity for specific thrombin binding.
• This technology shows promise for sensitive protein assays in complex biological matrices.