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Bioaerosols could carry and spread harmful microorganisms, thus posing a continuous threat to human beings and livestock health. Early warning and management are crucial for controlling the spread of bioaerosols. Herein, we developed a split aptamer (SA)-based electrochemical nanosensor chip (denoted SAE-nChip) for rapid and sensitive detection of adenosine triphosphate (ATP) in bioaerosols. The platform features two components: split DNA aptamers for their ability to bind ATP and undergo target-induced assembly on the chip surface and ZIF-8@MXene composites for their ability to provide a high surface density of aptamer-binding sites and facilitate the electron transfer at the biointerface. The SAE-nChip was capable of detecting ATP with a detection limit of 10 pM. Furthermore, this assay allowed the detection of ATP in cultured microorganisms and collected real bioaerosols. Overall, this strategy of interfacing DNA aptamers with MXene-based composite materials represents a versatile approach for the ubiquitous detection of biochemical targets in bioaerosols.

There is currently a great need for developing a simple and effective biosensing platform for the detection of single biomolecules (e.g., DNAs, RNAs, or proteins) in the biological, medical, and environmental fields. Here, we show a versatile and sensitive fluorescence counting strategy for quantifying proteins and microRNAs by employing functional DNA superstructures (denoted as 3D DNA). A 3D DNA biolabel was first engineered to become highly fluorescent and carry recognition elements for the target of interest. The presence of a target cross-links the resultant of the 3D DNA biolabel and a surface-bound capturing antibody or DNA oligonucleotide, thus forming a sandwich complex that can be easily resolved using traditional fluorescence microscopy. The broad utility of this platform is illustrated by engineering two different 3D DNA biolabels that enable the quantification of β-lactamase (one secreted bacterial hydrolase) and miR-21 (one overexpressed microRNA in cancer cells) with detection limits of 100 aM and 1 fM, respectively. We envision that the approach described herein will find useful applications in chemical biology, medical diagnostics, and biosensing.

Phosphorus is a key element responsible for eutrophication, and its measurement and speciation is a critical topic in analytical chemistry. Most research efforts have been devoted to detecting phosphate (P(V)), while few reports on phosphite (P(III)) are available, making it difficult for sensor-based understanding of the phosphorus cycle. This study presents a fluorescent "turn-on" sensor for quantitative and highly selective analysis of phosphite based on the different coordination strength of N and P lone-pair electrons toward nickel oxide (NiO). A few N-containing compounds (mainly Good's buffers) were screened as inhibitors for the oxidase-like activity of NiO nanoparticles for the oxidation of Amplex red (AR). HEPES was found to be most effective for inhibiting the formation of fluorescent resorufin, the oxidation product of AR. Among various phosphorus-, arsenic-, selenium-, and sulfur-containing species, along with various cations, phosphite was the only one that could restore the activity, likely due to its stronger affinity with the surface, and it is not an inhibitor. Under the optimum condition, the sensor detected P(III) up to 1 mM with a detection limit of 1.46 μM. The phosphite analysis with recovery rates ranged from 74.2 ± 2.6% to 107.5 ± 0.5% in real water and biological samples, suggesting the potential applicability of this sensor.