Novel ssDNA aptamer-based fluorescence sensor for perfluorooctanoic acid detection in water

Detecting Perfluorooctanoic Acid in Environmental Water Samples by Design of a Novel and Efficient Photoelectrochemical Sensing Platform

Contrapose the frequent occurrence of perfluorooctanoic acid (PFOA) in the environment and the serious threat to human health, it is urgent to establish effective analytical methods for monitoring PFOA levels in the environment. In this work, a novel and efficient PEC sensing platform was developed for the detection of PFOA based on CuSe/CdSe/TiO2 nanotube arrays (NTs) composites as the photoactive material and anti-PFOA aptamer as the biorecognition element. First, CdSe quantum dots (QDs) with a narrow band gap were decorated on TiO2 NTs surface. Furthermore, CuSe/CdSe/TiO2 NTs composites with a p-n heterojunction structure were designed through modifying p-type semiconductor CuSe on CdSe QDs-decorated TiO2 NTs. The as-prepared composites greatly enhanced visible light absorption and promoted charge separation, exhibiting good PEC activity. Attributed to the specific recognition of aptamer molecules immobilized on the composites toward PFOA, the formed PFOA-aptamer complexes introduced significant steric hindrance at the sensing interface, thereby impeding electron transfer and reducing the photocurrent density, and the variation in photocurrent density enabled quantitative determination of PFOA. The constructed PEC sensing platform has high sensitivity and specificity to PFOA, with a detection limit of 0.053 pg/L. Furthermore, the performance of the sensor in various environmental water samples was studied, yielding satisfactory results. Therefore, a simple and efficient PEC sensing technique has been established, providing a new solution for highly sensitive and specific detection of PFOA in the environment.

Synergistic Integration of Aggregation-Induced Emission and FRET Mechanisms in Conjugated Polymers via Molecular Engineering for Ultrasensitive, Rapid, and Discriminative Detection of Perfluoroalkyl Substances

The global contamination of water bodies by persistent organic pollutants (perfluoroalkyl substances (PFAS)) has generated significant societal concern, emphasizing the urgent need for smart strategies for their rapid, ultratrace, and on-site detection. Conjugated polymers (CPs) are exceptional fluorescence sensing materials with signal-amplification properties, yet their performance is often hindered by a conventional aggregation-caused quenching (ACQ) effect. Herein, we present two acceptor-engineered aggregation-induced emission (AIE)-active CPs (FTD-MI and FTD-C8-MI) integrated with efficient Förster resonance energy transfer (FRET) mechanisms for ultralow detection of PFAS. FTD-MI exhibits a turn-off (cyan to dark) fluorescence response, while FTD-C8-MI shows a ratiometric (cyan to red) response to PFAS due to the synergistic effect of AIE and efficient interchain FRET, facilitated by electrostatic and hydrophobic interactions upon binding. Both CPs demonstrate excellent sensitivity at the subnanomolar level toward the most abundant PFAS, perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS). The sensing mechanism has been thoroughly investigated by both experimental and simulation studies. Additionally, an optical sensor array coupled with machine learning algorithms is established for the discriminative detection of six types of PFAS. Finally, a portable smartphone platform with a custom-designed "app" was developed for real-time, on-site, and semiquantitative analysis of PFAS in actual water samples. Thus, by providing a sensitive, portable, cost-effective, and user-friendly solution, this work offers a powerful tool for monitoring PFAS pollution, ensuring water safety, and reducing risks to public health.

Tracking Perfluorooctanoic Acid in Tap and River Water Employing Screen-Printed Electrodes Modified with Molecularly Imprinted Polymers

While existing polyfluoroalkyl substances (PFAS) detection techniques are highly sensitive, their broader implementation is limited by the need for expensive equipment, lengthy analysis times, and specialized personnel. This underscores the need for fast, reliable, cost-effective, and accessible PFAS detection methods to avoid exposure to these pollutants and expedite the remediation of contaminated environments. Currently, portable electrochemical sensors for in situ contaminant detection are gaining significant attention. This study focuses on developing an electrochemical sensor for on-site perfluorooctanoic acid (PFOA) detection utilizing screen-printed electrodes (SPEs) modified with molecularly imprinted polymers (MIPs). The sensor's performance is evaluated using electrochemical impedance spectroscopy (EIS), with the electrochemical signals for PFOA detection arising from the specific interactions between MIPs and PFOA. The sensor exhibits a linear response to PFOA in phosphate-buffered saline within a concentration range of 0.1 nM to 10 μM, a detection limit of 19 ± 1 pM, and a quantification limit of 42 ± 3 nM. The selectivity of the sensor is assessed by measuring its response to four different PFAS compounds. Additionally, its real-world applicability is tested by analyzing the EIS response in tap and river water samples. The developed sensor, which combines an easy-to-use dipstick format with readily prepared SPEs, has the potential for large-scale production for in situ PFOA detection.

A critical review of sensors for detecting per- and polyfluoroalkyl substances: Focusing on diverse molecular probes

Per and Polyfluoroalkyl Substances (PFASs) pose a severe threat to the ecological environment and human health due to their persistence, bioaccumulation, and potential toxicity in the environment. Currently, the detection methods of PFASs generally rely on the combination of chromatographic techniques and mass spectrometry, which are typically suitable for laboratory testing. To meet the requirements of on-site detection, there is an urgent need to develop convenient and efficient detection methods. Sensors, as the preferred alternative, have been widely studied. In order to deeply investigate the mechanism of sensors in recognizing PFASs, this review, from the unique perspective of molecular probes, summarizes the construction and recognition mechanisms of four molecular probes: antibodies, aptamers, synthesized micromolecules, and synthesized polymers for PFASs. This review focuses on PFOA and PFOS as representative perfluoroalkyl substances and systematically investigates their properties and effects. It also analyzes the respective advantages, disadvantages, and applicable scenarios, and discusses the future development trends.

Rapid and Ultrasensitive Sensor for Point-of-Use Detection of Perfluorooctanoic Acid Based on Molecular Imprinted Polymer and AC Electrothermal Effect

Perfluorooctanoic acid (PFOA) is one of the most persistent and bioaccumulative water contaminants. Sensitive, rapid, and in-field analysis is needed to ensure safe water supplies. Here, we present a single step (one shot) and rapid sensor capable of measuring PFOA at the sub-quadrillion (ppq) level, 4.5 × 10-4 ppq, within 10 s. This innovative sensor employs a synergistic combination of a molecularly imprinted polymer (MIP)-modified gold interdigitated microelectrode chip and AC electrothermal effects (ACETs), which enhance detection sensitivity by facilitating the accelerated movement of PFOA molecules towards specific recognition sites on the sensing surface. The application of a predetermined AC signal induces microfluidic enrichment and results in concentration-dependent changes in interfacial capacitance during the binding process. This enables real-time, rapid quantification with exceptional sensitivity. We achieved a linear dynamic range spanning from 0.4 to 40 fg/L (4 × 10-7-4 × 10-5 ppt) and demonstrated good selectivity (~1:100) against other PFAS compounds, including perfluorooctanoic acid (PFOS), in PBS buffer. The sensor's straightforward operation, cost-effectiveness, elimination of the need for external redox probes, compact design, and functionality in relatively resistant environmental matrices position it as an outstanding candidate for deployment in practical applications.

Infrared Electrochemiluminescence from A Water-Soluble Anion-π+ Emitter for Sensitive Perfluorooctanoic Acid Sensing

Electrochemiluminescence (ECL) analysis stands out among various analytical methods due to its exceptional sensitivity and accuracy. However, the poor solubility of most ECL probes limits their effectiveness in aqueous environments. To address this challenge, we developed a water-soluble anion-π+ ECL luminophore, DPBC-OTS. With its remarkable water solubility and electron transfer characteristics, the study detailed revealed that DPBC-OTS exhibited excellent ECL performance in the infrared region. Additionally, leveraging ion electrostatic interactions, the DPBC-OTS-based ECL system achieved ultrasensitive detection of the organic fluorine pollutant PFOA, with a detection limit as low as 28.9 nM. This study not only enhances ECL performance in aqueous media through the introduction of the anion-π+ compound but also highlights the significant potential of ECL in the trace detection of organic fluorine pollutants.

Multiplex aptamer cluster detection platform and systems toxicology study for 17β-estradiol, bisphenol A, and diethylstilbestrol

Intake of 17β-estradiol (E2), bisphenol A (BPA), and diethylstilbestrol (DES) from food can contribute to endocrine disorders. Therefore, developing a sensitive method for the simultaneous detection of E2, BPA, and DES and understanding their combined effects on endocrine disruption are crucial. We developed a fluorescence aptasensing platform utilizing DNase I-assisted cyclic enzymatic signal amplification in conjunction with an aptamer/graphene oxide complex. Using PEG 20000 as a surface-blocking agent, the aptasensor achieved ultralow detection limits of 2.643, 0.3039, and 0.6996 for E2, BPA, and DES, respectively. The sensor demonstrated accurate detection in plastic bottled water at spiked levels of 10 and 100 ng/mL. Systems toxicology revealed 30 potential targets for mixture-induced endocrine disruption. Molecular docking showed binding affinities of E2, BPA, and DES for ESR1 of -9.94, -8.29, and - 8.98 kcal/mol, respectively. These results highlight the effectiveness of the aptasensor and provide valuable insights into endocrine disruption mechanisms.

An autonomous microbial sensor enables long-term detection of TNT explosive in natural soil

Microbes can be engineered to sense target chemicals for environmental and geospatial detection. However, when engineered microbes operate in real-world environments, it remains unclear how competition with natural microbes affect their performance over long time periods. Here, we engineer sensors and memory-storing genetic circuits inside the soil bacterium Bacillus subtilis to sense the TNT explosive and maintain a long-term response, using predictive models to design riboswitch sensors, tune transcription rates, and improve the genetic circuit's dynamic range. We characterize the autonomous microbial sensor's ability to detect TNT in a natural soil system, measuring single-cell and population-level behavior over a 28-day period. The autonomous microbial sensor activates its response by 14-fold when exposed to low TNT concentrations and maintains stable activation for over 21 days, exhibiting exponential decay dynamics at the population-level with a half-life of about 5 days. Overall, we show that autonomous microbial sensors can carry out long-term detection of an important chemical in natural soil with competitive growth dynamics serving as additional biocontainment.

A rapid and accurate fluorescent sensor array based on lanthanide metal-organic framework for identification and determination of perfluorinated compounds

Perfluorinated compounds (PFCs), as an important class of environmental pollutants, have chemical and structural similarities that make their detection a great technical challenge. This study synthesized three species of metal-organic frameworks (MOFs) using different lanthanide metal ions or organic ligands, which were integrated into a fluorescent sensor array. This innovative approach offers a straightforward, rapid, and precise detection strategy for PFCs. Different ionization properties and fluorinated hydrophobic tails of PFCs lead to different electrostatic attraction and hydrophobic effects between PFCs and sensing elements, which become the basis for differential sensing. Furthermore, the fluorescence signal is more convenient to collect, making the sensor array simple to complete the identification. Combined with pattern recognition methods, the array successfully identified seven kinds of PFCs and mixtures with a classification accuracy of 100 % and a detection limit as low as 51 nM. Finally, the utility of the sensor array in river water sample analysis was verified. The strategy provides an effective method for identifying and determining PFCs and offers new opportunities for developing sensor arrays based on lanthanide MOFs.

Aptamer-Triggered Nucleic Acid Amplification Strategy for the Electrochemiluminescence Detection of Perfluorooctanoic Acid

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent micropollutants. Due to their chemical stability and bioaccumulation, concentrations of PFASs in environmental media, even at ultratrace levels, pose significant environmental and health risks. However, currently reported detection methods lack an effective signal amplification strategy, and the detection sensitivity is limited, which can not meet the requirements of ultratrace detection. Herein, a groundbreaking aptamer-recognition-driven nucleic acid strategy was developed to significantly amplify the detection signal of perfluorooctanoic acid (PFOA). Furthermore, step pulse (SP) was used instead of cyclic voltammetry (CV) as an electrochemical excitation method to modulate the low electrochemiluminescence (ECL) triggering potential of poly [9,9-bis (3'-(N, N-dimethylamino) propyl) -2,7-fluorene]-alt-2,7-(9,9-dioctylfluorene)] (PFN) nanoparticles (NPs) so that a strong signal of +0.80 V was emitted without any exogenous coreactants. PFN NPs coupled rolling circle amplification-assisted PAM-free CRISPR/Cas12a system to construct an ultrasensitive ECL aptasensor for PFOA detection and the limit of detection was as low as 1.97 × 10-15 M. This ECL system integrated the advantages of no exogenous coreactants, low trigger potential, and nucleic acid amplification strategy and provided an ultrasensitive method for monitoring trace PFOA in the real water sample.

In Silico Analysis of Binding Sites for a Novel ssDNA Aptamer Specific to Verrucarin A and Detection in Dust Extracts

An aptamer is a single-stranded oligonucleotide that serves as a chemical antibody with a high specificity and binding affinity that can recognize a wide range of molecules. Effective modification and truncation of aptamers can enhance their binding affinities to particular targets while also broadening their application for uses, such as biosensors. However, a conventional trial-and-error methodology hinders this process. Herein, we demonstrate an in silico method to elucidate the binding site of single-stranded DNA aptamer specific to verrucarin A, a mycotoxin produced by molds in indoor buildings that causes adverse effects in living organisms. The novel ssDNA aptamer exhibited a binding affinity of 29.5 nM, demonstrating a relatively strong affinity compared to those of previously reported typical aptamers for small molecules. Furthermore, the selected aptamer was highly specific toward verrucarin A among structurally related mycotoxins (i.e., verrucarol and zearalenone). The specific binding site of the aptamer predicted via molecular dynamics and molecular docking simulations was highly consistent with the results observed via truncation, single base mutation, and circular dichroism experiments. The fluorescence assay revealed limits of detection and quantification of 4.1 and 12 nM for the aptamer, respectively. Comparing our developed aptasensor with LC-MS/MS methodology revealed that it could detect verrucarin A levels in phosphate-buffered saline and dust extracts with robust precision and consistency. Our findings provide insight for future studies exploring interaction mechanisms with intended targets and practical sensing applications, such as point-of-care detection of verrucarin A.

Programming of a Portable Digital Monitoring System-Integrated DNA Aptamer Reversely Regulated Oxidase-Like Nanozyme for Real-Time Dynamic Analysis of Atmospheric Perfluorooctanoic Acid

Timely and efficient analysis of the fluorinated per- and polyfluoroalkyl substances (PFAS) in an atmospheric environment is critical to environmental pollution traceability, early warnings, and governance. Here, a portable, reliable, and intelligent digital monitoring device for onsite real-time dynamic analysis of atmospheric perfluorooctanoic acid (PFOA) is proposed. The sensing mechanism is attributed to the oxidase-like activity of PtCoNPs@g-C3N4 that is reversely regulated by the surface modification of a PFOA-recognizable DNA aptamer, engineering a PFOA-activated oxidase-like activity of nanozyme (Apt-PtCoNPs@g-C3N4) to combine the nonfluorescence o-phenylenediamine (OPD) as the dual-modality response system. The present PFOA interacts with its DNA aptamer and dissociates from the surface of Apt-PtCoNPs@g-C3N4, restoring the oxidase-like activity of PtCoNPs@g-C3N4 to oxidize OPD into yellow fluorescence 2,3-diphenylaniline (DAP), thereby observing a PFOA-triggered colorimetric as well as fluorescence dual-modality change. Then, a hydrogel kit-programmed Apt-PtCoNPs@g-C3N4 + OPD system is used as the sensitive element to incorporate into this homemade portable device, automatically gathering and processing the PFOA-triggered hydrogel colorimetric and fluorescence image gray values by our self-weaving software, ultimately realizing the onsite real-time dynamic analysis of atmospheric PFOA surrounding a fluorochemical production plant. This work provides a direction and theoretical foundation for designing portable onsite screening devices that cater to other atmospheric contaminants detection requirements.

Rapid degradation of perfluorooctane sulfonic acid (PFOS) and perfluorononanoic acid (PFNA) through bimetallic catalyst of Fe2O3/Mn2O3 and unravelling the effect of support SiO2

Perfluoroalkyl substances (PFAS) are emerging contaminants present in various water sources. Their bioaccumulation and potential toxicity necessitate proper treatment to ensure safe water quality. Although iron-based monometallic photocatalysts have been reported to exhibit rapid and efficient PFAS degradation, the impact of bimetallic photocatalysts is unknown. In addition, the mechanistic effects of utilizing a support are poorly understood and solely based on physicochemical properties. This study investigates the efficacy of bimetallic photocatalysts (Fe2O3/Mn2O3) in inducing the photo-Fenton reaction for the degradation of perfluorooctane sulfonate (PFOS) and perfluorononanoic acid (PFNA) under various conditions. The rapid removal of both PFAS was observed within 10 min, with a maximum efficiency exceeding 97 % for PFOS under UV exposure, aided by the photocatalytic activation (photo-Fenton) of the oxidant (H2O2). Contrary to expectations, the use of the SiO2 support material did not significantly improve the removal efficiency. The efficacy of PFNA decreased despite SiO2 providing larger surface areas for Fe2O3/Mn2O3 loading. Further analysis revealed that the adsorption of PFAS onto the catalyst surfaces owing to electrostatic interactions contributed to the removal efficiency, where the degradation efficacy was worse than that of the catalyst with SiO2. This is because adsorption hindered the effective contact of H2O2 with catalytic reaction sites, thereby impeding the generation of hydroxyl (·OH) radicals. This study indicates the importance of considering chemical properties, including surface charge, in catalyst design to ensure effective degradation, focusing on physicochemical properties, such as surface area might overlook crucial factors.

Development of a "Signal-On" Fluorescent Aptasensor for Highly Selective and Sensitive Detection of ZEN in Cereal Products Using Nitrogen-Doped Carbon Dots Based on the Inner Filter Effect

This study aimed to develop a novel fluorescent aptasensor for the quantitative detection of zearalenone (ZEN), addressing the limitations of conventional detection techniques in terms of speed, sensitivity, and ease of use. Nitrogen-doped carbon dots (N-CDs) were synthesized via the hydrothermal method, resulting in spherical particles with a diameter of 3.25 nm. These N-CDs demonstrated high water solubility and emitted a bright blue light at 440 nm when excited at 355 nm. The fluorescence of N-CDs was quenched by dispersed gold nanoparticles (AuNPs) through the inner filter effect, while aggregated AuNPs induced by NaCl did not affect the fluorescence of N-CDs. The aptamer could protect AuNPs from NaCl-induced aggregation, but the presence of ZEN weakened this protective effect. Based on this principle, optimal conditions for ZEN detection included 57 mM NaCl, 12.5 nM aptamer concentration, incubation of AuNPs with NaCl for 15 min in Tris-EDTA(TE) buffer, and incubation of aptamer with ZEN and NaCl for 30 min. Under these optimized conditions, the "signal-on" fluorescent aptasensor for ZEN detection showed a linear range of 0.25 to 200 ng/mL with a low detection limit of 0.0875 ng/mL. Furthermore, the developed aptasensor exhibited excellent specificity and could rapidly detect ZEN in corn flour samples or corn oil, achieving satisfactory recovery rates ranging from 84.7% to 108.6%. Therefore, this study presents an economical, convenient, sensitive, and rapid method for accurately quantifying ZEN in cereal products.

Lanthanide metal-organic framework-based surface molecularly imprinted polymers ratiometric fluorescence probe for visual detection of perfluorooctanoic acid with a smartphone-assisted portable device

Perfluorooctanoic acid (PFOA) poses a threat to the environment and human health due to its persistence, bioaccumulation, and reproductive toxicity. Herein, a lanthanide metal-organic framework (Ln-MOF)-based surface molecularly imprinted polymers (SMIPs) ratiometric fluorescence probe (Eu/Tb-MOF@MIPs) and a smartphone-assisted portable device were developed for the detection of PFOA with high selectivity in real water samples. The integration of Eu/Tb MOFs as carriers not only had highly stable multiple emission signals but also prevented deformation of the imprinting cavity of MIPs. Meanwhile, the MIPs layer preserved the fluorescence of Ln-MOF and provided selective cavities for improved specificity. Molecular dynamics (MD) was employed to simulate the polymerization process of MIPs, revealing that the formation of multiple recognition sites was attributed to the establishment of hydrogen bonds between functional monomers and templates. The probe showed a good linear relationship with PFOA concentration in the range of 0.02-2.8 μM, by giving the limit of detection (LOD) of 0.98 nM. Additionally, The red-green-blue (RGB) values analysis based on the smartphone-assisted portable device demonstrated a linear relationship of 0.1-2.8 μM PFOA with the LOD of 3.26 nM. The developed probe and portable device sensing platform exhibit substantial potential for on-site detecting PFOA in practical applications and provide a reliable strategy for the intelligent identification of important targets in water environmental samples.

State-of-the-art in engineering small molecule biosensors and their applications in metabolic engineering

Genetically encoded biosensors are crucial for enhancing our understanding of how molecules regulate biological systems. Small molecule biosensors, in particular, help us understand the interaction between chemicals and biological processes. They also accelerate metabolic engineering by increasing screening throughput and eliminating the need for sample preparation through traditional chemical analysis. Additionally, they offer significantly higher spatial and temporal resolution in cellular analyte measurements. In this review, we discuss recent progress in in vivo biosensors and control systems-biosensor-based controllers-for metabolic engineering. We also specifically explore protein-based biosensors that utilize less commonly exploited signaling mechanisms, such as protein stability and induced degradation, compared to more prevalent transcription factor and allosteric regulation mechanism. We propose that these lesser-used mechanisms will be significant for engineering eukaryotic systems and slower-growing prokaryotic systems where protein turnover may facilitate more rapid and reliable measurement and regulation of the current cellular state. Lastly, we emphasize the utilization of cutting-edge and state-of-the-art techniques in the development of protein-based biosensors, achieved through rational design, directed evolution, and collaborative approaches.

The Latest Sensor Detection Methods for per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFASs) have emerged as a prominent environmental pollutant in recent years, primarily due to their tendency to accumulate and magnify in both the environment and living organisms. The entry of PFASs into the environment can have detrimental effects on human health. Hence, it is crucial to actively monitor and detect the presence of PFASs. The current standard detection method of PFAS is the combination of chromatography and mass spectrometry. However, this requires expensive instruments, extra sample pretreatment steps, complicated operation and long analysis time. As a result, new methods that do not rely on chromatography and mass spectrometry have been developed and applied. These alternative methods mainly include optical and electrochemical sensor methods, which offer great potential in terms of real-time field detection, instrument miniaturization, shorter analysis time, and reduced detection cost. This review provides a summary of recent advancements in PFAS detection sensors. We categorize and explain the principles and mechanisms of these sensors, and compare their limits of detection and sensitivity. Finally, we discuss the future challenges and improvements needed for PFAS sensors, such as field application, commercialization, and other related issues.

An Overview on Recent Advances in Biomimetic Sensors for the Detection of Perfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are a class of materials that have been widely used in the industrial production of a wide range of products. After decades of bioaccumulation in the environment, research has demonstrated that these compounds are toxic and potentially carcinogenic. Therefore, it is essential to map the extent of the problem to be able to remediate it properly in the next few decades. Current state-of-the-art detection platforms, however, are lab based and therefore too expensive and time-consuming for routine screening. Traditional biosensor tests based on, e.g., lateral flow assays may struggle with the low regulatory levels of PFAS (ng/mL), the complexity of environmental matrices and the presence of coexisting chemicals. Therefore, a lot of research effort has been directed towards the development of biomimetic receptors and their implementation into handheld, low-cost sensors. Numerous research groups have developed PFAS sensors based on molecularly imprinted polymers (MIPs), metal-organic frameworks (MOFs) or aptamers. In order to transform these research efforts into tangible devices and implement them into environmental applications, it is necessary to provide an overview of these research efforts. This review aims to provide this overview and critically compare several technologies to each other to provide a recommendation for the direction of future research efforts focused on the development of the next generation of biomimetic PFAS sensors.

Fluorescent nanostructured carbon dot-aptasensor for chlorpyrifos detection: Elucidating the interaction mechanism for an environmentally hazardous pollutant

Chlorpyrifos (CPF) is a commonly used insecticide found in many water sources and is related to several health and environmental effects. Biosensors based on aptamers (single-stranded nucleic acid oligonucleotides) are promising alternatives to achieve the detection of CPF and other pesticides in natural waters. However, several challenges need to be addressed to promote the real application of functional aptasensing devices. In this work, an ssDNA aptamer (S1) is combined with carbon quantum dots (CD) and graphene oxide (GO) to produce a stable fluorescent aptasensor characterized through spectrophotometric and electrophoretic techniques. For a deeper understanding of the system, the mechanism of molecular interaction was studied through docking modeling using free bioinformatic tools like HDOCK, showing that the stem-loops and the higher guanine (G) content are crucial for better interaction. The model also suggests the possibility of generating a truncated aptamer to improve the binding affinity. The biosensor was evaluated for CPF detection, showing a low LOD of 0.01 μg L-1 and good specificity in tap water, even compared to other organophosphates pesticides (OPs) like profenofos. Finally, the recovery of the proposed aptasensor was evaluated in some natural water using spiked samples and compared with UPLC MS-MS chromatography as the gold standard, showing a good recovery above 2.85 nM and evidencing the need of protecting ssDNA aptamers from an erratic interaction with the aromatic groups of dissolved organic matter (humic substances). This work paves the way for a better aptasensors design and the on-site implementation of novel devices for environmental monitoring.

High-Throughput Effect-Directed Monitoring Platform for Specific Toxicity Quantification of Unknown Waters: Lead-Caused Cell Damage as a Model Using a DNA Hybrid Chain-Reaction-Induced AuNPs@aptamer Self-Assembly Assay

A high-throughput cell-based monitoring platform was fabricated to rapidly measure the specific toxicity of unknown waters, based on AuNPs@aptamer fluorescence bioassays. The aptamer is employed in the platform for capturing the toxicity indicator, wherein hybrid chain-reaction (HCR)-induced DNA functional gold nanoparticle (AuNPs) self-assembly was carried out for signal amplification, which is essential for sensitively measuring the sub-lethal effects caused by target compounds. Moreover, the excellent stability given by the synthesized DNA nanostructure provides mild conditions for the aptamer thus used to bind the analyte. Herein, ATP was treated as a toxicity indicator and verified using lead-caused cell damage as a model. Under optimized conditions, excellent performance for water sample measurement was observed, yielding satisfactory accuracy (recovery rate: 82.69-114.20%; CV, 2.57%-4.65%) and sensitivity (LOD, 0.26 µM) without sample pretreatment other than filtration, indicating the method's simplicity, high efficiency, and reliability. Most importantly, this bioassay could be used as a universal platform to encourage its application in the rapid quantification of specific toxicity in varied sources of samples, ranging from drinking water to highly contaminated wastewater.

Pyrene-Containing Polyamines as Fluorescent Receptors for Recognition of PFOA in Aqueous Media

The globally widespread perfluorooctanoic acid (PFOA) is a concerning environmental contaminant, with a possible toxic long-term effects on the environment and human health The development of sensible, rapid, and low-cost detection systems is a current change in modern environmental chemistry. In this context, two triamine-based chemosensors, L1 and L2, containing a fluorescent pyrene unit, and their Zn(II) complexes are proposed as fluorescent probes for the detection of PFOA in aqueous media. Binding studies carried out by means of fluorescence and NMR titrations highlight that protonated forms of the receptors can interact with the carboxylate group of PFOA, thanks to salt bridge formation with the ammonium groups of the aliphatic chain. This interaction induces a decrease in the fluorescence emission of pyrene at neutral and slightly acidic pH values. Similarly, emission quenching has also been observed upon coordination of PFOA by the Zn(II) complexes of the receptors. These results evidence that simple polyamine-based molecular receptors can be employed for the optical recognition of harmful pollutant molecules, such as PFOA, in aqueous media.

Two-in-one platform based on conjugated polymer for ultrasensitive ratiometric detection and efficient removal of perfluoroalkyl substances from environmental water

Continuous emergence of persistent organic pollutants perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in various water bodies around the world poses a serious threat to the global ecosystem. The exploration of advanced detection/removal techniques to monitor/treat such type of toxicants is urgently required. Herein, we unveiled a donor-acceptor type conjugated polymer PF-DBT-Im as a first-of-its-kind ratiometric fluorescent probe for visual, amplified, and specific monitoring of PFOA and PFOS with ultra-low detection limits of 6.12 nM (PFOA) and 14.3 nM (PFOS), respectively. PF-DBT-Im undergoes strong aggregation after binding with PFOA/PFOS as evident by transmission electron microscopy, zeta potential measurements, and dynamic light scattering studies. This promotes interchain Förster resonance energy transfer process to endorse an obvious emission color change from blue-to-magenta under ultraviolet lamp excitation. Consequently, a smartphone-integrated portable device is fabricated for realizing rapid and on-site detection of PFOA/PFOS. Besides, a new class of magnetic adsorbent Fe₃O₄@NH₂&F₁₃ is also prepared and used in combination with PF-DBT-Im to remove PFOA/PFOS from the environmental water effectively and rapidly as confirmed by liquid chromatography-mass spectrometry analysis. Thus, utilizing the excellent signal amplification property of PF-DBT-Im and the remarkable magnetic separation capability of Fe₃O₄@NH₂&F₁₃, a multifunctional system is developed for step-wise recognition and separation of PFOA/PFOS from the environmental water proficiently and rapidly.

Detection and differentiation of per- and polyfluoroalkyl substances (PFAS) in water using a fluorescent imprint-and-report sensor array

Widespread industrial use of per- and polyfluoroalkyl substances (PFAS) as surfactants has led to global contamination of water sources with these persistent, highly stable chemicals. As a result, humans and wildlife are regularly exposed to PFAS, which have been shown to bioaccumulate and cause adverse health effects. Methods for detecting PFAS in water are currently limited and primarily utilize mass spectrometry (MS), which is time-consuming and requires expensive instrumentation. Thus, new methods are needed to rapidly and reliably assess the pollution level of water sources. While some fluorescent PFAS sensors exist, they typically function in high nanomolar or micromolar concentration ranges and focus on sensing only 1-2 individual PFAS. Our work aims to address this problem by developing a fluorescent sensor for both individual PFAS, as well as complex PFAS mixtures, and demonstrate its functionality in tap water samples. Here we show that dynamic combinatorial libraries (DCLs) with simple building blocks can be templated with a fluorophore and subsequently used as sensors to form an array that differentially detects each PFAS species and various mixtures thereof. Our method is a high-throughput analysis technique that allows many samples to be analyzed simultaneously with a plate reader. This is one of the first examples of a fluorescent PFAS sensor array that functions at low nanomolar concentrations, and herein we report its use for the rapid detection of PFAS contamination in water.

A single strand: A simplified approach to DNA origami

Just as a single polypeptide strand can self-fold into a complex 3D structure, a single strand of DNA can self-fold into DNA origami. Most DNA origami structures (i.e., the scaffold-staple and DNA tiling systems) utilize hundreds of short single-stranded DNA. As such, these structures come with challenges inherent to intermolecular construction. Many assembly challenges involving intermolecular interactions can be resolved if the origami structure is constructed from one DNA strand, where folding is not concentration dependent, the folded structure is more resistant to nuclease degradation, and the synthesis can be achieved at an industrial scale at a thousandth of the cost. This review discusses the design principles and considerations employed in single-stranded DNA origami and its potential benefits and drawbacks.

Preferential interactions of surface-bound engineered single stranded DNA with highly aromatic natural organic matter: Mechanistic insights and implications for optimizing practical aquatic applications

Engineered short-chain single stranded DNA (ssDNA) are emerging materials with various environmental applications, such as aptasensor, selective adsorbent, and hydrological tracer. However, the lack of fundamental understanding on the interactions of such materials with natural organic matter (NOM) hinders the improvement of their application performance in terms of sensitivity, selectivity, and stability. In this study, we investigated the interactions of ssDNA (four strands with systematically varied length and sequence) with two humic acids (Suwannee River humic acid (SRHA) and Aldrich humic acid (AHA)) and two humic-like NOM present in local aquatic matrices (ROM in river water and WOM in wastewater). Detailed, molecular level interaction mechanisms were obtained by probing the colloidal stability of the ssDNA-coated gold nanoparticles, coupled with product characterization using a suite of microscopic and spectroscopic techniques. Our study revealed that π-π interactions and divalent cation bridging were the major mechanisms for ssDNA-NOM interactions. ssDNA preferentially interacted with NOM with high aromaticity (AHA > SRHA/WOM/ROM). With divalent cations present (especially Ca²⁺), even a small amount of AHA could completely shield ssDNA, whereas the extent of shielding by SRHA/WOM/ROM depended on the relative content of ssDNA and NOM and whether bridges formed. The extent of shielding of ssDNA by NOM provides a potential answer to the reported conflicting effects of natural water matrices on the performance of DNA-based sensors. Taken together, our findings provide insights into the transformations of engineered ssDNA under environmentally relevant conditions as well as implications for their performance optimization in practical aquatic applications (e.g., from DNA design to pretreatment strategy).