Abstract
In recent years, reagentless aptamer biosensors, named aptasensors, have shown significant advancements. Particularly, electrochemical aptasensors could change the field of biosensors in this era, where digitalization seems to be a common goal of many fields. Biomedical devices are integrating electronic technologies for detecting pathogens, biomolecules, small molecules, and ions, and the physical-chemical properties of nucleic acid aptamers makes them very interesting for these devices. Aptamers can be easily synthesized and functionalized with functional groups for immobilization and with redox chemical groups that allow for the conversion of molecular interactions into electrical signals. Furthermore, non-labeled aptamers have also been utilized. This review presents the current challenges involved in aptasensor architectures based on gold electrodes as transducers.
Highlights
Biosensors are devices that facilitate the specific detection of analytes and produce detectable signals, correlating the presence of a target analyte such as proteins, DNA, glucose, cholesterol, toxins, hormones, bacteria, etc
In the last few years, we have witnessed novel developments in electrochemical biosensors and their translation from bench to commercial devices; a key is the lack of systematic screening technology to discover novel molecules for biosensing applications
Aptamers are an interesting class of oligonucleotides, larger than small molecules but smaller than antibodies, with specific binding affinities toward a variety of targets [64,70,71]
Summary
Biosensors are devices that facilitate the specific detection of analytes and produce detectable signals, correlating the presence of a target analyte such as proteins, DNA, glucose, cholesterol, toxins, hormones, bacteria, etc. Potential probes for commercial electrochemical affinity-based biosensors include enzymes (e.g., oxidoreductases) and DNA molecules for genomic analysis and DNA or RNA aptamers for capturing target analytes. While enzymes have high selectivity for their substrates, they possess several disadvantages that affect the electron transfer efficiency—(1) they are large molecules, (2) the active site is usually deeply buried, affecting the electron transfer, and (3) they have a limited shelf life To overcome these problems, efforts are dedicated to finding enzyme immobilization procedures and protein engineering in order to improve the electron transfer efficiency of enzymes. In our opinion, there are still several limitations that aptamer electrochemical-based biosensors need to overcome, including the development of a systematic aptamer discovery process for biosensors, chemisorption of molecules on the conductive surface, quality of the semiconductor material, and improvement of the signal-to-noise ratio. While many aspects of aptamers and their potential uses have been extensively reviewed elsewhere [4,6,7,8,9], this review is focused on the current limitations, which challenge the development of aptamer electrochemical-based biosensors, and the sensor architectures that have been developed so far
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