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Aptamers, a group of nucleic acids which can specifically bind to a target molecule, have drawn extensive interest over the past few decades. For analytics, aptamers represent a viable alternative to gold-standard antibodies due to their oligonucleic nature combined with advantageous properties, including higher stability in harsh environments and longer shelf-life. Indeed, over the last decade, aptamers have been used in numerous bioanalytical assays and in various point-of-care testing (POCT) platforms. The latter allows for rapid on-site testing and can be performed outside a laboratory by unskilled labor. Aptamer technology for POCT is not limited just to medical diagnostics; it can be used for a range of applications, including environmental monitoring and quality control. In this review, we critically examine the use of aptamers in POCT with an emphasis on their advantages and limitations. We also examine the recent success of aptasensor technology and how these findings pave the way for the analysis of small molecules in POCT and other health-related applications. Finally, the current major limitations of aptamers are discussed, and possible approaches for overcoming these challenges are presented. © 2020 by the authors.

Detection of the small molecule 25-hydroxyvitamin D (25(OH)D) as the most relevant marker for vitamin D supply suffers from a high variability of results using the current detection methods, such as high-performance liquid chromatography (HPLC) and immunoassays. A new detection approach using a highly specific aptamer directed against 25(OH)D was established in this study based on the target-induced dissociation (TID) sensing approach. In this work, the aptamer was investigated regarding its structural properties as well as its binding affinity by using microscale thermophoresis (MST). Moreover, complementary oligonucleotides were designed based on the aptamer structure and were evaluated in MST experiments. Binding experiments of immobilized aptamers were conducted in microarray experiments. It could be shown that the aptamer exhibited the usual B-DNA structure and did not form any G-quadruplexes. The design of complementary oligonucleotides for the TID assay identified a putative 25(OH)D binding site within the aptamer. The limit of detection of the established competitive assay was determined to be 5.4 nM, which sets the stage for the development of a biosensor system.