Gold nanoparticles (AuNPs) have been extensively used for detecting arsenite, As­(III). Many methods rely on a DNA aptamer that claimed to bind specifically to inorganic arsenic. In these cases, the focus was on arsenic binding to the aptamer, while the potential interactions between As­(III) and the AuNP surface were ignored. Herein, a set of spectroscopic and isothermal titration calorimetry (ITC) experiments were conducted to measure the adsorption of As­(III) by AuNPs and its competition with DNA adsorption. With 10 mM As­(III), 18% of adsorbed DNA was displaced from AuNPs, while preadsorption of only 20 μM As­(III) inhibited DNA adsorption by around 50%. The affinity of As­(III) on AuNPs is comparable to Br– and guanosine. ITC and Raman spectroscopy both indicated that only As­(III) can be adsorbed, while As­(V) had no measurable interactions with the AuNPs. Based on this understanding, a random DNA sequence was used and a similar colorimetric response in the presence of As­(III) was observed. This study confirmed the affinity between As­(III) and the gold surface. The As­(III)/gold interaction is strong enough to affect DNA adsorption, and care should be taken to interpret the observations based on the color change of AuNPs for the detection of As­(III).

We report on a unique DNA aptamer, denoted MSA52, that displays universally high affinity for the spike proteins of wildtype SARS‐CoV‐2 as well as the Alpha, Beta, Gamma, Epsilon, Kappa, Delta and Omicron variants. Using an aptamer pool produced from round 13 of selection against the S1 domain of the wildtype spike protein, we carried out one‐round SELEX experiments using five different trimeric spike proteins from variants, followed by high‐throughput sequencing and sequence alignment analysis of aptamers that formed complexes with all proteins. A previously unidentified aptamer, MSA52, showed Kd values ranging from 2 to 10 nM for all variant spike proteins, and also bound similarly to variants not present in the reselection experiments. This aptamer also recognized pseudotyped lentiviruses (PL) expressing eight different spike proteins of SARS‐CoV‐2 with Kd values between 20 and 50 pM, and was integrated into a simple colorimetric assay for detection of multiple PL variants. This discovery provides evidence that aptamers can be generated with high affinity to multiple variants of a single protein, including emerging variants, making it well‐suited for molecular recognition of rapidly evolving targets such as those found in SARS‐CoV‐2.

Molecular imprinting of enzyme mimics allows delivery and selective catalysis and protection of the enzyme in cells.