The ability to continuously monitor the concentration of specific molecules in the body is a long-sought goal of biomedical research. For this purpose, interstitial fluid (ISF) was proposed as the ideal target biofluid because its composition can rapidly equilibrate with that of systemic blood, allowing the assessment of molecular concentrations that reflect full-body physiology. In the past, continuous monitoring in ISF was enabled by microneedle sensor arrays. Yet, benchmark microneedle sensors can only detect molecules that undergo redox reactions, which limits the ability to sense metabolites, biomarkers, and therapeutics that are not redox-active. To overcome this barrier, here, we expand the scope of these devices by demonstrating the first use of microneedlesupported electrochemical, aptamer-based (E-AB) sensors. This platform achieves molecular recognition based on affinity interactions, vastly expanding the scope of molecules that can be sensed. We report the fabrication of microneedle E-AB sensor arrays and a method to regenerate them for multiple uses. In addition, we demonstrate continuous molecular measurements using these sensors in flow systems in vitro using single and multiplexed microneedle array configurations. Translation of the platform to in vivo measurements is possible as we demonstrate with a first E-AB measurement in the ISF of a rodent. The encouraging results reported in this work should serve as the basis for future translation of microneedle E-AB sensor arrays to biomedical research in preclinical animal models.

The mortality of patients with EVD was closely associated with age and duration from symptom onset to presentation for care. Patients with EVD identified in the current outbreak did not necessarily have fever. Early diagnosis of the disease and timely symptomatic treatment may greatly contribute to the reduction of fatality rate of patients with EVD.

It has been almost 30 years since the invention of Systematic Evolution of Ligands by Exponential Enrichment (SELEX) methodology and the description of the first aptamers. In retrospect over the past 30 years, advances in aptamer development and application have demonstrated that aptamers are potentially useful reagents that can be employed in diverse areas within analytical chemistry, biotechnology, biomedicine, and molecular biology. While often touted as artificial antibodies with an ability to be selected for any target, aptamer development, unfortunately, lags behind development of analytical methodologies that employ aptamers, hindering deeper integration into the application of analytical tool development. This perspective covers recent advances in SELEX methodology for improving efficiency of the SELEX procedure and enhancing affinity and specificity of the selected aptamers, what we view as a critical barrier in the future role of aptamers in analytical chemistry. We discuss postselection modifications that can be used for enhancing performance of the selected aptamers in an analytical device by including understanding intermolecular interaction forces in the binding domain. While highlighting promising properties of aptamers that enable several analytical advances, we provide discussion on the challenges of penetration of aptamers in the analytical field.

A novel strategy to fabricate an aptasensor for potassium with high sensitivity and selectivity by using nicking endonuclease is proposed in this work. A nicking endonuclease (Nt.CviPII), which may recognize specific nucleotide sequences in double-stranded DNA formed by a potassium-binding aptamer and a linker DNA but cleave only the linker strand, may transfer and amplify the quantitative information of the potassium detection to that of the linker DNA through elaborate strand-scission cycles. Since the technique for gene assay is much more mature, the linker DNA can thereby be detected by a number of available methods. Here, taking advantage of a simple and fast gold nanoparticles-based sensing technique, we are able to assay the linker and consequently potassium ion simply by UV-vis spectroanalysis and even with the naked eye. Results show that a 2 μL sample containing 0.1 mM of potassium is enough to induce distinct color appearance of the nanoparticles, and the potassium ion can be easily distinguished from many other ions. The strategy proposed in this work shows some unique advantages over some traditional methods and may be further developed for the detection of some other chemicals in the future.