Sensitive bioassay for detection of PPARα potentially hazardous ligands with gold nanoparticle probe

Bivalent affinity binding-inspired PPARγ immobilization with selective conformation and improved ligand-binding activity

Functional protein immobilization forms the basis for bio-detections. A series of one-point, site-specific immobilization methods have been developed, however, it still remains as a challenge how to avoid the proteins to move in all directions as well as conveniently regenerate the bio-devices. Herein, we have developed a bivalent affinity binding-inspired method for PPARγ immobilization using DNA aptamer and nickel-nitrilotriacetic acid (Ni2+-NTA) chelation. The specific DNA aptamer (Apt 2) was selected by an on-column systematic evolution of ligands by exponential enrichment (SELEX) method with affinity of (1.57 ± 0.15) × 105 M-1, determined by isothermal titration calorimetry (ITC). Apt 2 and nickel-nitrilotriacetic acid (Ni2+-NTA) were modified on macroporous silica gels via L-α-allylglycine as a linker. They respectively interacted with PPARγ and 6×His tag via bivalent affinity binding for the receptor immobilization. After comprehensive surface characterization, PPARγ was proved to be successful immobilized. Chromatographic studies revealed that the immobilized PPARγ has conformation selectivity, which discriminated agonist and antagonist of the receptor. Ligand-binding parameters (affinity and rate constant) of four agonists (rosiglitazone, pioglitazone, troglitazone, and magnolol) with PPARγ were determined. Troglitazone showed the lowest dissociation rate constant. The binding affinities (3.28 × 107, 1.91 × 106, 2.25 × 107, and 2.43 × 107 M-1) were highly consistent with the data obtained using purified receptor in solution (2.16 × 107, 4.52 × 106, 1.20 × 107, and 1.56 × 107 M-1), offering reliable bio-detection method for PPARγ and its ligands. Due to the biocompatibility of nuclear receptor with DNA, it is conceivable that the bivalent affinity-based method will be a general method for the immobilization of other nuclear receptors, which may provide selective conformation and improved ligand-binding activity for the receptors.

A new sensitive layer based on clcinated Zn/Ti-MOF/magnetic molecularly imprinted polypyrrole: Application to preconcentration and electrochemical determination of perfluorooctane sulfonic acid by magnetic carbon paste electrode

In this research, a new approach based on magnetic electrodes has been developed for the determination of per-fluorooctane sulfonic acid (PSOF). Zinc and Titanium-based Metal-organic framework (MOF) was synthesized and used with polypyrrole as a conductive polymer for preparation of the absorbent to achieve the best performance for electrochemical application. The response of the electrode for determination of the PFOS was affected and optimized by different factors such as buffer solution, pH of the solution, amount of absorbent, extraction time of absorbent, accumulation time, as well as the Square Wave Voltammetry (SWV) instrumental parameters including voltage step, pulse amplitude, frequency and resting time. In the optimum condition, the response of the Zn/Ti/C-MOF-magnetic molecular imprinting polymer/carbon paste electrode (MOFMMIP/CPE) has increased logarithmically by increasing the concentration in the range of 0.002-165 μM by the limit of detection (LOD) of 0.7 nM. The obtained percentage of Recovery (96.00-104.14 %), Bias (-4.00 - 4.14 %) and Relative Standard Deviation (RSD) (1.89-3.74 %) for determination of the PFOS in real and spiked tap water, river water and well water samples demonstrates that the proposed method has an acceptable precision. The comparison between the gained data by the presented method and High-performance liquid chromatography (HPLC) showed that the presented method has high accuracy.

PPARβ/δ-ANGPTL4 axis mediates the promotion of mono-2-ethylhexyl phthalic acid on MYCN-amplified neuroblastoma development

Di-2-ethylhexyl phthalic acid (DEHP) is one of the most widely used plasticizers in the industry, which can improve the flexibility and durability of plastics. It is prone to migrate from various daily plastic products through wear and leaching into the surrounding environment and decompose into the more toxic metabolite mono-2-ethylhexyl phthalic acid (MEHP) after entering the human body. However, the impacts and mechanisms of MEHP on neuroblastoma are unclear. We exposed MYCN-amplified neuroblastoma SK-N-BE(2)C cells to an environmentally related concentration of MEHP and found that MEHP increased the proliferation and migration ability of tumor cells. The peroxisome proliferator-activated receptor (PPAR) β/δ pathway was identified as a pivotal signaling pathway in neuroblastoma, mediating the effects of MEHP through transcriptional sequencing analysis. Because MEHP can bind to the PPARβ/δ protein and initiate the expression of the downstream gene angiopoietin-like 4 (ANGPTL4), the PPARβ/δ-specific agonist GW501516 and antagonist GSK3787, the recombinant human ANGPTL4 protein, and the knockdown of gene expression confirmed the regulation of the PPARβ/δ-ANGPTL4 axis on the malignant phenotype of neuroblastoma. Based on the critical role of PPARβ/δ and ANGPTL4 in the metabolic process, a non-targeted metabolomics analysis revealed that MEHP altered multiple metabolic pathways, particularly lipid metabolites involving fatty acyls, glycerophospholipids, and sterol lipids, which may also be potential factors promoting tumor progression. We have demonstrated for the first time that MEHP can target binding to PPARβ/δ and affect the progression of neuroblastoma by activating the PPARβ/δ-ANGPTL4 axis. This mechanism confirms the health risks of plasticizers as tumor promoters and provides new data support for targeted prevention and treatment of neuroblastoma.

Calixarene-based supramolecular assembly with fluorescent gold-nanoclusters for highly selective determination of perfluorooctane sulfonic acid

The present study developed an efficient fluorescent approach, based on a supramolecular assembly between gold nanoclusters and calix[4]arene derivatives (C4A-Ds), to detect sever pollutant of perfluorooctane sulfonic acid (PFOS). For that, a series of C4A-Ds with different chain lengths and positive charges at the wider rim were designed and synthesized. Cytidine-5' phosphate protected gold nanoclusters (AuNCs@CMP) were then assembled with calix[4]arene (LC4AP) to form AuNCs/LC4AP assembly, leading to 8-fold luminescence enhancement via the AIEE effect. However, further binding with PFOS reconstituted the as-formed assembly hrough a competitive effect, generating a fluorescence quenching. Particularly, the linear fluorescence response of AuNCs/LC4AP to PFOS realized a highly sensitive determination of the pollutant PFOS in a wide range (2.0-100 μM). In addition, the developed method successfully detected PFOS in pool water near a fire drill field, being good enough for the practical PFOS determination. The calixarene mediated method, based on the fluorescence "on-off" strategy of metal nanoclusters, is sensitive, rapid-responsive, economical, particularly, suitable for the PFOS determination in practice. It takes full advantage of the molecular recognition and self-assembly of artificial macrocyclic host molecules as a promising strategy for the PFOS determination, and will be highlight to develop new detection methods for PFOS and other poisonous compounds in environments.

Research Progress on Up-Conversion Fluorescence Probe for Detection of Perfluorooctanoic Acid in Water Treatment

Perfluorooctanoic acid (PFOA) is a new type of organic pollutant in wastewater that is persistent, toxic, and accumulates in living organisms. The development of rapid and sensitive analytical methods to detect PFOA in environmental media is of great importance. Fluorescence detection has the advantages of high efficiency and low cost, in which fluorescent probes have excellent fluorescence properties, excellent bio-solubility, and remarkable photostability. It is necessary to review the fluorescence detection routes for PFOA. In addition, the up-conversion of fluorescent materials (UCNPs), as fluorescent materials to prepare fluorescent probes with, has significant advantages and also attracts the attention of researchers, however, reviews related to their application in detecting PFOA and comparing them with other routes are rare. Furthermore, there are many strategies to improve the performance of up-conversion fluorescent probes including SiO₂ modification and amino modification. These strategies can enhance the detection effect of PFOA. Thus, this work reviews the types of fluorescence detection, the design, and synthesis of UCNPs, their recognition mechanism, properties, and their application progress. Moreover, the development trend and prospects of these detection probes are given.

Detection methods for sub-nanogram level of emerging pollutants - Per and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are organofluorine compounds has been manufactured for more than five decades and used in different purposes. Among persistent organic pollutants, PFAS are toxic, bioaccumulative in humans, wildlife, and global environment. As per environmental protection agency (EPA) guidelines, the perfluorooctanoate and perfluorooctane sulfonate permissible limit was 0.07 ng/L in drinking water. When the concentration exceeds the acceptable limit, it has negative consequences for humans. In such a case, PFAS monitoring is critical, and a quick detection technique are highly needed. Health departments and regulatory agencies have interests in monitoring of PFAS presences and exposures. For the detection of PFAS, numerous highly precise and sensitive chromatographic methods are available. However, the drawbacks of analytical techniques include timely sample preparations and the lack of on-site applicability. As a result, there is an increasing demand for simple sensor systems for monitoring of PFAS in real field samples. In this review, we first describe the sample pre-treatment and analytical techniques for the detection of PFAS. Second, we broadly discussed available sensor system for the quantification of PFAS in different filed samples. Finally, future trends in PFASs sensor are also presented.

Nano-enabled sensing of per-/poly-fluoroalkyl substances (PFAS) from aqueous systems - A review

Per-/poly-fluoroalkyl substances (PFAS) are an emerging class of environmental contaminants used as an additive across various commodity and fire-retardant products, for their unique thermo-chemical stability, and to alter their surface properties towards selective liquid repellence. These properties also make PFAS highly persistent and mobile across various environmental compartments, leading to bioaccumulation, and causing acute ecotoxicity at all trophic levels particularly to human populations, thus increasing the need for monitoring at their repositories or usage sites. In this review, current nano-enabled methods towards PFAS sensing and its monitoring in wastewater are critically discussed and benchmarked against conventional detection methods. The discussion correlates the materials' properties to the sensitivity, responsiveness, and reproducibility of the sensing performance for nano-enabled sensors in currently explored electrochemical, spectrophotometric, colorimetric, optical, fluorometric, and biochemical with limits of detection of 1.02 × 10^-6 μg/L, 2.8 μg/L, 1 μg/L, 0.13 μg/L, 6.0 × 10^-5 μg/L, and 4.141 × 10^-7 μg/L respectively. The cost-effectiveness of sensing platforms plays an important role in the on-site analysis success and upscalability of nano-enabled sensors. Environmental monitoring of PFAS is a step closer to PFAS remediation. Electrochemical and biosensing methods have proven to be the most reliable tools for future PFAS sensing endeavors with very promising detection limits in an aqueous matrix, short detection times, and ease of fabrication.

Selectivity of Per- and Polyfluoroalkyl Substance Sensors and Sorbents in Water

Per- and polyfluoroalkyl substances (PFAS) are a large group of engineered chemicals that have been widely used in industrial production. PFAS have drawn increasing attention due to their frequent occurrence in the aquatic environment and their toxicity to animals and humans. Developing effective and efficient detection and remediation methods for PFAS in aquatic systems is critical to mitigate ongoing exposure and promote water reuse. Adsorption-based removal is the most common method for PFAS remediation since it avoids hazardous byproducts; in situ sensing technology is a promising approach for PFAS monitoring due to its fast response, easy operation, and portability. This review summarizes current materials and devices that have been demonstrated for PFAS adsorption and sensing. Selectivity, the key factor underlying both sensor and sorbent performance, is discussed by exploring the interactions between PFAS and various probes. Examples of selective probes will be presented and classified by fluorinated groups, cationic groups, and cavitary groups, and their synergistic effects will also be analyzed. This review aims to provide guidance and implication for future material design toward more selective and effective PFAS sensors and sorbents.

Engineering human liver fatty acid binding protein for detection of poly- and perfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic fluorinated chemicals with surface active and water-repellent properties. The combination of wide-spread use in numerous consumer and industrial products and extended biological half-lives arising from strong carbon-fluorine bonds has led to significant accumulation of PFAS in humans. As most human interaction with PFAS comes from ingestion, it is important to be able to detect PFAS in drinking water as well as in agricultural water. Here we present an approach to designing a fluorescence-based biosensor for the rapid detection of PFAS based on human liver fatty acid binding protein (hLFABP). Introduction of solvatochromic fluorophores within the ligand binding pocket (L50) allowed for intrinsic detection of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexanesulfonic acid (PFHxS) via blue-shifts in fluorescence emission spectra. Initially, a single tryptophan mutation (L50W) was found to be able to detect PFOA with a limit of detection (LOD) of 2.8 ppm. We improved the sensitivity of the biosensor by exchanging tryptophan for the thiol reactive fluorophore, acrylodan. The acrylodan conjugated C69S/F50C hLFABP variant is capable of detecting PFOA, PFOS, and PFHxS in PBS with LODs of 112 ppb, 345 ppb, and 1.09 ppm, respectively. The protein-based sensor is also capable of detecting these contaminants at similar ranges in spiked environmental water samples, including samples containing an interfering anionic surfactant sodium dodecyl sulfate. Overall, this study demonstrates engineered hLFABP is a useful platform for detection of PFAS in environmental water samples and highlights its ease of use and versatility in field applications.

Light-Induced Advanced Oxidation Processes as PFAS Remediation Methods: A Review

PFAS substances, which have been under investigation in recent years, are certainly some of the most critical emerging contaminants. Their presence in drinking water, correlated with diseases, is consistently being confirmed by scientific studies in the academic and health sectors. With the aim of developing new technologies to mitigate the water contamination problem, research activity based on advanced oxidation processes for PFAS dealkylation and subsequent mineralization is active. While UV radiation could be directly employed for decontamination, there are nevertheless considerable problems regarding its use, even from a large-scale perspective. In contrast, the use of cheap, robust, and green photocatalytic materials active under near UV-visible radiation shows interesting prospects. In this paper we take stock of the health problems related to PFAS, and then provide an update on strategies based on the use of photocatalysts and the latest findings regarding reaction mechanisms. Finally, we detail some brief considerations in relation to the economic aspects of possible solutions.

Sensors for detecting per- and polyfluoroalkyl substances (PFAS): A critical review of development challenges, current sensors, and commercialization obstacles

Per- and polyfluoroalkyl substances (PFAS) are a class of compounds that have become environmental contaminants of emerging concern. They are highly persistent, toxic, bioaccumulative, and ubiquitous which makes them important to detect to ensure environmental and human health. Multiple instrument-based methods exist for sensitive and selective detection of PFAS in a variety of matrices, but these methods suffer from expensive costs and the need for a laboratory and highly trained personnel. There is a big need for fast, inexpensive, robust, and portable methods to detect PFAS in the field. This would allow environmental laboratories and other agencies to perform more frequent testing to comply with regulations. In addition, the general public would benefit from a fast method to evaluate the drinking water in their homes for PFAS contamination. A PFAS sensor would provide almost real-time data on PFAS concentrations that can also provide actionable information for water quality managers and consumers around the planet. In this review, we discuss the sensors that have been developed up to this point for PFAS detection by their molecular detection mechanism as well as the goals that should be considered during sensor development. Future research needs and commercialization challenges are also highlighted.

Exposure, health effects, sensing, and remediation of the emerging PFAS contaminants - Scientific challenges and potential research directions

Per- and polyfluoroalkyl substances (PFAS) make up a large group of persistent anthropogenic chemicals which are difficult to degrade and/or destroy. PFAS are an emerging class of contaminants, but little is known about the long-term health effects related to exposure. In addition, technologies to identify levels of contamination in the environment and to remediate contaminated sites are currently inadequate. In this opinion-type discussion paper, a team of researchers from the University of Connecticut and the University at Albany discuss the scientific challenges in their specific but intertwined PFAS research areas, including rapid and low-cost detection, energy-saving remediation, the role of T helper cells in immunotoxicity, and the biochemical and molecular effects of PFAS among community residents with measurable PFAS concentrations. Potential research directions that may be employed to address those challenges and improve the understanding of sensing, remediation, exposure to, and health effects of PFAS are then presented. We hope our account of emerging problems related to PFAS contamination will encourage a broad range of scientific experts to bring these research initiatives addressing PFAS into play on a national scale.

Recent progress in the detection of emerging contaminants PFASs

As an emerging contaminant, per- and polyfluoroalkyl substances (PFASs) make up a large group of persistent anthropogenic chemicals, which are difficult to degrade in the environment. Notwithstanding their wide range of applications in consumer products and industrial processes, PFASs have been detected in the environment as well as in human body. Due to their potential adverse human health effects, the U.S. Environmental Protection Agency (EPA) set the combined concentration of PFOA and PFOS in drinking water at 70 ng/L or 70 ppt (parts per trillion) as a lifetime health advisory level. Current standard detection methods for PFASs heavily rely on chromatographic techniques coupled with mass spectrometry. Although these methods provide accurate, specific, and sensitive measurements, their applications are greatly limited in advanced analytical laboratories because it necessitates expensive instrumentations, professional operators, complicated sample pretreatment, and considerable analysis time. Therefore, other detection methods beyond chromatographic based techniques, such as optical and electrochemical techniques, have also been extensively explored for simple, accessible, inexpensive, rapid, and sensitive detection of PFASs, particularly PFOA and PFOS. The purpose of this review is to provide recent progress in alternative detection platforms relying on non-MS based techniques for PFASs analysis. Starting with a brief introduction about the importance of monitoring PFASs, recent advances in various PFASs detection methods are grouped and discussed based on the difference of signals, with an emphasis on the working principles of different techniques, the sensing mechanism, and the sensing performance. The review is closed with the conclusion and discussion of future trends.

Recent Developments of PFAS-Detecting Sensors and Future Direction: A Review

Per- and poly-fluoroalkyl substances (PFASs) have recently been labeled as toxic constituents that exist in many aqueous environments. However, traditional methods used to determine the level of PFASs are often not appropriate for continuous environmental monitoring and management. Based on the current state of research, PFAS-detecting sensors have surfaced as a promising method of determination. These sensors are an innovative solution with characteristics that allow for in situ, low-cost, and easy-to-use capabilities. This paper presents a comprehensive review of the recent developments in PFAS-detecting sensors, and why the literature on determination methods has shifted in this direction compared to the traditional methods used. PFAS-detecting sensors discussed herein are primarily categorized in terms of the detection mechanism used. The topics covered also include the current limitations, as well as insight on the future direction of PFAS analyses. This paper is expected to be useful for the smart sensing technology development of PFAS detection methods and the associated environmental management best practices in smart cities of the future.

A new dual-recognition strategy for hybrid ratiometric and ratiometric sensing perfluorooctane sulfonic acid based on high fluorescent carbon dots with ethidium bromide

In this work, a novel strategy for perfluorooctane sulfonic acid (PFOS) detection was established by using a ratiometric nanosensor with the combination of fluorescence and second-order scattering (SOS). The practical ratiometric nanosensor was synthesized simply by mixing fluorescent dye ethidium bromide (EB) and nitrogen doped carbon dots (N-CDs) which was synthesized by a one-step hydrothermal method with Victoria Blue B, possessing three emission peaks at 472 nm, 560 nm and 600 nm under a single wavelength excitation of 280 nm, respectively. The EB served as the reference signal label, and the N-CDs, having response to the analytes, acted as the response signal label. To achieve ratiometric detection, the fluorescence emission of the N-CDs was turned off and the SOS emission was turned on with the addition of the target PFOS. To achieve colorimetric detection, with the help of EB, the fluorescence of the system changed from green to orange. Under the optimal conditions, the difference of F₄₇₂/I₅₆₈ of the nanosensor had good linearity against the concentrations of PFOS within a linear range of 0-2.0 μM. The limit of detection was as low as 27.8 nM, which was low enough for the detection of PFOS in water samples. The proposed method has been successfully applied to the detection of PFOS with RSD <1.67%. The results show that the as-prepared N-CDs/EB ratiometric nanosensor has potential application for the detection of PFOS in environmental monitoring.

Mediating Roles of PPARs in the Effects of Environmental Chemicals on Sex Steroids

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors that are widely involved in various physiological functions. They are widely expressed through the reproductive system. Their roles in the metabolism and function of sex steroids and thus the etiology of reproductive disorders receive great concern. Various kinds of exogenous chemicals, especially environmental pollutants, exert their adverse impact on the reproductive system through disturbing the PPAR signaling pathway. Chemicals could bind to PPARs and modulate the transcription of downstream genes containing PPRE (peroxisome proliferator response element). This will lead to altered expression of genes related to metabolism of sex steroids and thus the abnormal physiological function of sex steroids. In this review, various kinds of environmental ligands are summarized and discussed. Their interactions with three types of PPARs are classified by various data from transcript profiles, PPRE reporter in cell line, in silico docking, and gene silencing. The review will contribute to the understanding of the roles of PPARs in the reproductive toxicology of environmental chemicals.

Delivery of therapeutic agents by nanoparticles made of grapefruit-derived lipids

Although the use of nanotechnology for the delivery of a wide range of medical treatments has potential to reduce adverse effects associated with drug therapy, tissue-specific delivery remains challenging. Here we show that nanoparticles made of grapefruit-derived lipids, which we call grapefruit-derived nanovectors (GNVs), can transport chemotherapeutic agents, siRNA, DNA expression vectors and proteins to different types of cells. We demonstrate the in vivo targeting specificity of GNVs by co-delivering therapeutic agents with folic acid, which in turn leads to significantly increasing targeting efficiency to cells expressing folate receptors. The therapeutic potential of GNVs was further demonstrated by enhancing the chemotherapeutic inhibition of tumor growth in two tumor animal models. GNVs are less toxic than nanoparticles made of synthetic lipids and, when injected intravenously into pregnant mice, do not pass the placental barrier, suggesting they may be a useful tool for drug delivery.