Abstract
Aptamers are artificial nucleic acid ligands identified and obtained from combinatorial libraries of synthetic nucleic acids through the in vitro process SELEX (systematic evolution of ligands by exponential enrichment). Aptamers are able to bind an ample range of non-nucleic acid targets with great specificity and affinity. Devices based on aptamers as bio-recognition elements open up a new generation of biosensors called aptasensors. This review focuses on some recent achievements in the design of advanced label-free optical aptasensors using porous silicon (PSi) as a transducer surface for the detection of pathogenic microorganisms and diagnostic molecules with high sensitivity, reliability and low limit of detection (LoD).
Highlights
Biosensors are analytical hybrid devices comprising a bio-receptor immobilized on a transducer surface which is able to selectively recognize a molecular target [1,2].The most commonly employed bioprobes in biosensors development are enzymes, proteins, and antibodies (Abs), which suffer from various drawbacks, limiting their specific applications [3,4].The enzyme isolation procedure and consequent incorporation in in vitro operating environments could result in a loss of their activity [5]
The results showed that Ap-modified porous silicon (PSi) outperformed Ab-modified PSi devices in terms of insulin detection time and sensitivity: 19 nm effective optical thickness (EOT) shift in 12 min compared to 16 nm EOT shift in 60 min
This phenomenon might be due to a steric hindrance effect that could prevent the aptamer from folding into the correct 3D conformation required to show the highest insulin affinity [64]
Summary
Biosensors are analytical hybrid devices comprising a bio-receptor ( called bioprobe) immobilized on a transducer surface which is able to selectively recognize a molecular target [1,2]. New biomolecular recognition elements which are able to overcome the Ab and enzyme constraints associated with standard bioprobes are in growing demand in molecular sensing In this context, aptamers are considered as to have the greatest potential among the recognition tools which have developed in recent years. Aptamers are able to interact with their targets through structural recognition similar to that of the antibody-antigen reaction with a dissociation constant in the range of pico- to nano-molar. For these reasons, aptamers are usually referred as chemical Abs [8]. The improvement of device performance in terms of sensitivity, response time and limit of detection (LoD) will be discussed
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