Abstract
Semiconductor quantum dots have attracted extensive interest in the biosensing area because of their properties, such as narrow and symmetric emission with tunable colors, high quantum yield, high stability and controllable morphology. The introduction of various reactive functional groups on the surface of semiconductor quantum dots allows one to conjugate a spectrum of ligands, antibodies, peptides, or nucleic acids for broader and smarter applications. Among these ligands, aptamers exhibit many advantages including small size, high chemical stability, simple synthesis with high batch-to-batch consistency and convenient modification. More importantly, it is easy to introduce nucleic acid amplification strategies and/or nanomaterials to improve the sensitivity of aptamer-based sensing systems. Therefore, the combination of semiconductor quantum dots and aptamers brings more opportunities in bioanalysis. Here we summarize recent advances on aptamer-functionalized semiconductor quantum dots in biosensing applications. Firstly, we discuss the properties and structure of semiconductor quantum dots and aptamers. Then, the applications of biosensors based on aptamer-modified semiconductor quantum dots by different signal transducing mechanisms, including optical, electrochemical and electrogenerated chemiluminescence approaches, is discussed. Finally, our perspectives on the challenges and opportunities in this promising field are provided.
Highlights
Quantum dots (QDs) are colloidal nanocrystalline semiconductors and possess properties such as a quantum confinement effect
Electrogenerated chemiluminescence (ECL) method includes the generation of species at electrode surface undergoing electron-transfer reactions to form excited states, where light is produced when it decays to the ground state
Different from conventional organic fluorophores or fluorescent proteins, QDs are synthesized by wet chemical synthesis methods
Summary
Quantum dots (QDs) are colloidal nanocrystalline semiconductors and possess properties such as a quantum confinement effect. The excellent optical properties include: (1) Broad and consecutive excitation bands, high absorptivity [3]; (2) Narrow and symmetric emission, long fluorescence lifetime; (3) Good photostability [4], with low susceptibilities to photo-bleaching; (4) Tunable emission wavelength (Figure 1) [5,6,7]. (e.g., metal ions and etc.) with high affinity and specificity, equal to or superior to those properties small size and convenient modifications with various functional groups and nanomaterials. Proteins tend to be irreversibly denatured in certain conditions, while aptamers are capable (DHLA)–QD self-assembly, producing compact QD–DNA conjugates [13]. Mattoussi et al firstly used the His6-tagged DNA and dihydrolipoic acid (DHLA)–QD self-assembly, producing compact QD–DNA conjugates [13]. Some alternative modification strategies can be used in compact QD–DNA conjugates, such as self-assembly of thiolated-DNA onto 3-mercaptopropionic acid (MPA)–QDs [17]. We discuss the properties and structure of QDs, and the application of biosensors based on aptamer-modified QDs in the context of different signal transducing mechanisms, and further our perspectives are provided on the challenges and opportunities in this promising field
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