Quantum‐Dot‐Functionalized Poly(styrene‐co‐acrylic acid) Microbeads: Step‐Wise Self‐Assembly, Characterization, and Applications for Sub‐femtomolar Electrochemical Detection of DNA Hybridization

Abstract

A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene‐co‐acrylic acid) microbeads with CdTe quantum dots. CdTe‐tagged polybeads are prepared by a layer‐by‐layer self‐assembly of the CdTe quantum dots (diameter = 3.07 nm) and polyelectrolyte on the polybeads (diameter = 323 nm). The self‐assembly procedure is characterized using scanning and transmission electron microscopy, and X‐ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum‐dot coverage is (9.54 ± 1.2) × 103 per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe‐tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin–biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square‐wave voltammetry of Cd2+ after the dissolution of the CdTe tags with HNO3. The efficient carrier‐bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L−1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events.

Sensitive biosensing strategy based on functional nanomaterials

“…The change in fluorescent intensity could be used for the detection of the target with a detection limit down to 12 nM. QDs are also widely used as tags in ultrasensitive electrochemical DNA assays due to their intrinsic redox properties and the sensitive electrochemical stripping analysis of the metal components of QDs [51]. The efficient carrier-bead amplification platform can provide a hybridization detection of DNA down to 0.52 fmol/L.…”

“…A nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization has been fabricated by functionalizing poly(styrene-co-acrylic acid) microbeads with CdTe quantum dots [51]. As shown in Figure 8, the CdTe-tagged polybeads are attached to DNA probes by streptavidin-biotin binding to construct a DNA biosensor.…”

An enhanced sensing platform for ultrasensitive impedimetric detection of target genes based on ordered FePt nanoparticles decorated carbonnanotubes

“…Nevertheless, these techniques suffer from some disadvantages that include relatively complex operation processes, time-consuming, and high cost. DNA biosensors based on electrochemical transduction have attracted broad attention and been widely developed due to their advantages such as simple and inexpensive instrumentation, fast response, precise and sensitive measurements, and low production cost as well as compatibility with microfabrication technology (Dong et al, 2010;Jayakumar et al, 2012). Currently, much effort has been devoted to promote the detection sensitivity and selectivity of electrochemical DNA biosensors (Li et al, 2012).…”

Quantum dot-based electrochemical DNA biosensor using a screen-printed graphite surface with embedded bismuth precursor

“…Nevertheless, in the existing ASV-QD DNA assays, the surfaces on which the DNA assay is performed cannot be used as sensitive transducers for the ASV determination of the metallic ions released from QD labels; therefore, the hybridization/labeling step and the detection step take place at spatially separated surfaces. More specifically, in these applications the biorecognition events are conducted in microwells [3,4], on glass substrates [5], on magnetic beads [6][7][8][9], on carbon nanotubes [10], or on gold surfaces [11][12][13], while the ASV detection step of QDs is carried out at mercury-or bismuth-film sensors prepared via electroplating procedures on rigid glassy carbon electrodes. Besides the existing methodologies involve an additional step for generating the voltammetric detection layer while the electroplated metal-film electrodes present several drawbacks associated with the creation and deposition reproducibility of the Hg or Bi film.…”