A Bottom-Up Approach for Developing Aptasensors for Abused Drugs: Biosensors in Forensics

Abstract

Aptamer-based point-of-care (POC) diagnostics platforms may be of substantial benefit in forensic analysis as they provide rapid, sensitive, user-friendly, and selective analysis tools for detection. Aptasensors have not yet been adapted commercially. However, the significance of the applications of aptasensors in the literature exceeded their potential. Herein, in this review, a bottom-up approach is followed to describe the aptasensor development and application procedure, starting from the synthesis of the corresponding aptamer sequence for the selected analyte to creating a smart surface for the sensitive detection of the molecule of interest. Optical and electrochemical biosensing platforms, which are designed with aptamers as recognition molecules, detecting abused drugs are critically reviewed, and existing and possible applications of different designs are discussed. Several potential disciplines in which aptamer-based biosensing technology can be of greatest value, including forensic drug analysis and biological evidence, are then highlighted to encourage researchers to focus on developing aptasensors in these specific areas.

Keywords: custom-tailored aptamers; electrochemical biosensors; forensic sciences; optical biosensors; point-of-care (POC).

Figure 1

The systematic evolution of ligands by exponential enrichment (SELEX) cycle. SELEX starts with a random nucleic acid aptamer library which is used to initiate the SELEX cycle (top arrow entering cycle). The library is incubated with the target, and the target is washed to remove and discard unbound aptamers (right arrow exiting cycle) before the bound aptamers are eluted and amplified by PCR. The amplified sequences seed the next round of SELEX. Typically, around 12 SELEX cycles are performed before sequencing and aptamer characterization (left arrow exiting cycle). Reproduced with permission of [33]. Copyright 2017 Published by MDPI.

Figure 2

Main advantages of aptamers compared to antibodies.

Figure 3

Typical optical detection for both light transmitted through liquid sample platforms (i.e., cuvette, well plate) and light reflected from solid sample platforms (i.e., test strip, cassette) using (a) colorimetric assays, (b) fluorescence-based assays, (c) bio- and chemiluminescence assays, and (d) scattering-based assays. Reproduced with the permission of [106]. Copyright 2016 Published by The Royal Society of Chemistry.

Figure 4

Lateral flow based detection of cocaine. (a) DNA sequences and linkages in cocaine aptamer-linked nanoparticle aggregates. Test of the cocaine-sensing lateral flow device with varying concentrations of cocaine in buffer solution (b) and in undiluted human blood serum (c). Coc = cocaine, Ade = adenosine. Reproduced with the permission of [109]. Copyright 2006 Published by Wiley-VCH.

Figure 5

Schematic of cocaine sensing based on structure switching optical biosensing platform. (a) Structure switching of cocaine combining the two aptamer fragments; (b) hybridization and regeneration of the aptamer with optical fiber. Reproduced with the permission of [119]. Copyright 2016 Published by Elsevier B.V.

Figure 6

Electrochemical (Path A), photoelectrochemical (Path B), and surface plasmon resonance (SPR) (Path C) analysis of cocaine. Reproduced with the permission of [125]. Copyright 2009 Published by American Chemical Society.

Figure 7

Typical electrochemical biosensor measurement principles. Reproduced with the permission of [166]. Copyright 2015 Published by Elsevier B.V.

Figure 8

Aptasensor systems designing with fragments on Au surface with MCE as (a) Au/Cx5S/MCE, (b) Au/Cy5S/MCE, (c) Au/Cy3S/MCE. Reproduced with the permission of [183]. Copyright 2012 Published by Elsevier B.V.