Functionalized magnetic composites based on the aptamer serve as novel bio-adsorbent for the separation and preconcentration of trace lead

Recent advance on microextraction sampling technologies for bioanalysis

The contents of target substances in biological samples are usually at low concentration levels, and the matrix of biological samples is usually complex. Sample preparation is considered a very critical step in bioanalysis. At present, the utilization of microextraction sampling technology has gained considerable prevalence in the realm of biological analysis. The key developments in this field focus on the efficient microextraction media and the miniaturization and automation of adaptable sample preparation methods currently. In this review, the recent progress on the microextraction sampling technologies for bioanalysis has been introduced from point of view of the preparation of microextraction media and the microextraction sampling strategies. The advance on the microextraction media was reviewed in detail, mainly including the aptamer-functionalized materials, molecularly imprinted polymers, carbon-based materials, metal-organic frameworks, covalent organic frameworks, etc. The advance on the microextraction sampling technologies was summarized mainly based on in-vivo sampling, in-vitro sampling and microdialysis technologies. Moreover, the current challenges and perspective on the future trends of microextraction sampling technologies for bioanalysis were briefly discussed.

Quartz Crystal Microbalance-Based Aptasensors for Medical Diagnosis

Aptamers are important materials for the specific determination of different disease-related biomarkers. Several methods have been enhanced to transform selected target molecule-specific aptamer bindings into measurable signals. A number of specific aptamer-based biosensors have been designed for potential applications in clinical diagnostics. Various methods in combination with a wide variety of nano-scale materials have been employed to develop aptamer-based biosensors to further increase sensitivity and detection limit for related target molecules. In this critical review, we highlight the advantages of aptamers as biorecognition elements in biosensors for target biomolecules. In recent years, it has been demonstrated that electrode material plays an important role in obtaining quick, label-free, simple, stable, and sensitive detection in biological analysis using piezoelectric devices. For this reason, we review the recent progress in growth of aptamer-based QCM biosensors for medical diagnoses, including virus, bacteria, cell, protein, and disease biomarker detection.

Waste toner-derived micro-materials as low-cost magnetic solid-phase extraction adsorbent for the analysis of trace Pb in environmental and biological samples

Lead (Pb) is a toxic heavy metal and is commonly used in industrial applications. Thus, Pb poisoning is a concerning public health issue worldwide. The amounts of lead in natural water, urine, and blood can serve as significant indicators for monitoring the exposure of Pb poisoning. Waste toner has the characteristics of both "waste" and "resource," as it is a "resource in the wrong place." Here, a low-cost carboxylate-functionalized magnetic adsorbent was first synthesized from waste toner by a simple thermal treatment and served as a novel adsorbent with a flexible multidentate O-donor for pre-concentration of trace Pb. The characterization, adsorption behavior, and various factors of adsorption and desorption were adequately optimized, and prior to graphite furnace atomic absorption spectrometry (GFAAS) detection, a new magnetic solid-phase extraction method was proposed for the analysis of Pb in real environmental water and biological samples. The developed method exhibited a low detection limit (0.003 μg L^-1), high enrichment factor (88.6-fold), good linearity (0.01-0.3 μg L^-1), satisfactory precision with relative standard deviations of 7.9% (n = 7, C_Pb = 0.02 μg L^-1), fast adsorption kinetics (5 min), and strong ability to overcome matrix interference. Validation was also performed by analyzing a certified standard reference material, and the method was successfully applied to real tap water, lake water, human urine, and human blood serum with satisfactory recoveries of 92.6-109%.

Detecting Pb2+by a 'turn-on' fluorescence sensor based on DNA functionalized magnetic nanocomposites

Sensitive and selective detection of the lead ion (Pb²⁺) plays an important role in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. The highly stable fluorescence biosensor is composed of Fe₃O₄@TiO₂core-shell nanocomposites, functionalized with a carboxyl fluorescein labeled DNA. The morphology, physical and chemical properties of the sensing nanomaterials were studied by transmission electron microscopy, FT-IR spectroscopy (FT-IR), x-ray powder diffraction and vibrating sample magnetometer. UV-visible and fluorescence spectroscopy were used to characterize the fluorescein functionalized magnetic nanoparticles. The performance of Pb²⁺detection displayed an excellent linearity (R² = 0.995) in the range of 10^-10to 5 × 10^-9ppm with a detection limit of 10^-10ppm, based on the optimization of the fabrication process and aptamers' specification. The fluorescence biosensor has an accurate response, excellent recoveries and high adsorbent capacities. It was successfully applied for the determination of Pb²⁺in contaminated water and serum samples; the detection of limit in both media were 10^-10ppm. These features ensure the potential use of aptamer functionalized magnetic nanocomposites as a new class of non-toxic biocompatible sensors for biological and environmental applications.

Feasibility of calcium alginate beads to preconcentrate lead in river water samples prior to determination by flame atomic absorption spectrometry

Lead (Pb) is a potentially toxic element with significant environmental interest. Simple and sensitive analytical methods are necessary to allow determination of this element at trace levels using sample preparation procedures related to green chemistry. For this, calcium alginate beads (CA-beads), a low-cost and environmentally friendly biopolymer, have been proposed for extraction and preconcentration of Pb²⁺ in river water samples and determination by flame atomic absorption spectrometry (FAAS). CA-beads were prepared and applied to extract and preconcentrate Pb²⁺ in river water samples, providing an enrichment factor (EF) of 50, enhancement factor (E) of 54, a detection limit of 2 μg L^-1, and a relative standard deviation < 5%. The extraction of Pb²⁺ in CA-beads achieved good selectivity, with recoveries from 94.8 to 100.2% in real samples, demonstrating the good accuracy of the proposed method. The results were also compared to those obtained by ICP-MS. The reuse of CA-beads was evaluated for six cycles, and under these conditions, the extraction and preconcentration efficiency of Pb²⁺ were not significantly affected. The developed methodology was applied to determine Pb²⁺ in water samples from rivers that are part of the hydrographic areas of Tibagi and Pitangui Rivers, in which the Pb²⁺ concentration was less than 2 μg L^-1, a concentration lower than that established by Brazilian legislation for class I and II rivers.

Magnetic mesoporous silica/ε-polylysine nanomotor-based removers of blood Pb2

The removal of excessive blood lead ions (Pb2+) is very important to human health, but current effective removal technology is still lacking because of the complex existence state of Pb2+ in blood, which can be attributed to the fact that most of the blood Pb2+ is combined with haemoglobin (Hb) located in red blood cells (RBCs). Here, a new type of magnetic mesoporous silica/ε-polylysine nanomotor-based remover (MMS/P NR) with abundant chelation sites was designed, synthesized and used to remove Pb2+ from blood. The magnetic core can make the nanocomposites become nanomotors with autonomous movement under an external variable magnetic field, which can effectively improve the contact probability between the MMS/P NRs and Pb2+-contaminated Hb in RBCs. The amino rich ε-polylysine (ε-PL) was used as the co-template of mesoporous silica. Mesoporous channels can provide a confinement effect for Pb2+-contaminated Hb to stabilize the captured blood Pb2+. The movement behavior of the MMS/P NRs in and out of RBCs and the capture mechanism of Pb2+ in the blood were studied. The results indicate that the MMS/P NRs we propose have good blood compatibility, low cytotoxicity, magnetic properties, autonomous movement ability and recyclability under the condition of an external magnetic field. Moreover, compared with the experimental conditions without an external variable magnetic field (0.01485 mg g-1), the MMS/P NRs show a higher blood Pb2+ removal ability under the condition of an external variable magnetic field (0.05525 mg g-1). The design strategy of this remover based on nanomotor technology has great potential in the future medical treatment of heavy metal poisoning.

12-Plex UHPLC-MS/MS analysis of sarcosine in human urine using integrated principle of multiplex tags chemical isotope labeling and selective imprint enriching

Urinary sarcosine was considered to be a potential biomarker for prostate cancer (Pca). In this work, an integrated strategy of multiplex tags chemical isotope labeling (MTCIL) combined with magnetic dispersive solid phase extraction (MDSPE), was proposed for specific extraction and high-throughput determination of sarcosine by ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). In the past three months, we have developed 8-plex MTCIL reagents with excellent qualitative and quantitative performance. In this work, the multiplexing capacity of MTCIL reagents (MTCIL360/361/362/363/364/365/366/375/376/378/379/381) was increased 1.5-fold from 8-plex to 12-plex. MTCIL359 was prepared and used to label sarcosine standard as internal standard (IS). The structural analogue derivative (MTCIL373-sarcosine) of all targeted MTCIL-sarcosine derivatives was synthesized and used as a novel dummy template to prepare dummy magnetic molecularly imprinted polymers (DMMIPs). The integration of MTCIL and DMMIPs procedures were extremely favorable to excellent chromatographic separation and efficient mass spectrometric detection. The labeling efficiency, chromatographic retention and mass spectrometry responses of MTCIL reagents were consistent for sarcosine. In a single UHPLC-MS/MS run (2.0 min), this method can simultaneously quantify sarcosine in 12-plex urine samples and achieve unbiased concentrations comparison between different urine samples. Analytical parameters including linearity (R² 0.989-0.997), detection limits (0.02 nM), precision (2.6-11.5%), accuracy (96.1-107.4%), matrix effect, labeling and extraction efficiency were carefully validated. The proposed method was successfully applied for urinary sarcosine determination of healthy male individuals and Pca patients. It was found that the sarcosine concentrations in these two groups were statistically extremely significantly different (P < 0.001). The developed method was a powerful analytical tool to substantially promote the analysis throughput and large-scale experiments about the potential biomarker research.

Biosensors for wastewater-based epidemiology for monitoring public health

Public health is attracting increasing attention due to the current global pandemic, and wastewater-based epidemiology (WBE) has emerged as a powerful tool for monitoring of public health by analysis of a variety of biomarkers (e.g., chemicals and pathogens) in wastewater. Rapid development of WBE requires rapid and on-site analytical tools for monitoring of sewage biomarkers to provide immediate decision and intervention. Biosensors have been demonstrated to be highly sensitive and selective tools for the analysis of sewage biomarkers due to their fast response, ease-to-use, low cost and the potential for field-testing. This paper presents biosensors as effective tools for wastewater analysis of potential biomarkers and monitoring of public health via WBE. In particular, we discuss the use of sewage sensors for rapid detection of a range of targets, including rapid monitoring of community-wide illicit drug consumption and pathogens for early warning of infectious diseases outbreaks. Finally, we provide a perspective on the future use of the biosensor technology for WBE to enable rapid on-site monitoring of sewage, which will provide nearly real-time data for public health assessment and effective intervention.

Recent advances on aptamer-based biosensors for detection of pathogenic bacteria

As a significant constituent in biosphere, bacteria have a great influence on human activity. The detection of pathogen bacteria is closely related to the human health. However, the traditional methods for detection of pathogenic bacteria are time-consuming and difficult for quantification, although they are practical and reliable. Therefore, novel strategies for rapid, sensitive, and cost-effective detection are in great demand. Aptamer is a kind of oligonucleotide that selected by repeated screening in vitro or systematic evolution of ligands by exponential enrichment (SELEX) technology. Over the past years, owing to high affinity and specificity of aptamers, a variety of aptamer-based biosensors have been designed and applied for pathogen detection. In this review, we have discussed the recent advances on the applications of aptamer-based biosensors in detection of pathogenic bacteria. In addition, we also point out some problems in current methods and look forward to the further development of aptamer-based biosensors for pathogen detection.

Aminophosphonic Acid Functionalized Cellulose Nanofibers for Efficient Extraction of Trace Metal Ions

Cellulose nanofibers were covalently functionalized using diethylenetriamine penta (methylene phosphonic acid) and studied for the extraction of heavy metal ions. The surface-functionalized nanofibers showed a high adsorption capacity towards heavy metal ions as compared to bare nanofibers. The elemental composition and surface morphology of the prepared bio-adsorbent was characterized by X-ray photoelectron spectroscopy, attenuated total reflectance infrared spectroscopy, field emission scanning electron microscopy, and energy dispersive spectroscopy. The prepared material was studied to develop a column-based solid phase extraction method for the preconcentration of trace metal ions and their determination by inductively coupled plasma optical emission spectroscopy. The batch experimental data was well fitted to Langmuir adsorption isotherms (R2 > 0.99) and follows pseudo-second-order kinetics. The experimental variables such as sample pH, equilibrium time, column breakthrough, sorption flow rate, the effect of coexisting ions, and eluent type were systematically studied and optimized accordingly. The detection limit of the proposed method was found to be 0.03, 0.05, and 0.04 µg L-1 for Cu(II), Pb(II), and Cd(II), respectively. Certified Reference Materials were analyzed to validate the proposed method against systematic and constant errors. At a 95% confidence level, the Student's t-test values were less than the critical Student's t value (4.302). The developed method was successfully employed for the preconcentration and determination of trace metal ions from real water samples such as river water and industrial effluent.

Poly (deep eutectic solvents) as a new class of sustainable sorbents for solid phase extraction: application for preconcentration of Pb (II) from food and water samples

A new class of polymeric sorbents based on deep eutectic solvents (DESs) is introduced. These materials are obtained from simple and inexpensive precursors via an energy-efficient process. The primary benefit of these sorbents is that they possess the unique characteristics of DESs and porous materials simultaneously. Moreover, the possibility of tailoring deep eutectic solvents allows designing a specific polymer for a desired analyte, based on its physical and chemical properties. In this work, the deep eutectic solvent of tetrabutylammonium bromide and acrylic acid (1:2 molar ratio) was prepared and then polymerized under solventless condition. The synthesized polymer was characterized by FT-IR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and Brunauer, Emmett and Teller analysis (BET) to evaluate the properties of the sorbent. The poly (TBAB-2AA DES) was applied as a selective sorbent for preconcentration of lead from food and water samples prior to its quantification by flame atomic absorption spectroscopy (FAAS). Variable factors affecting the extraction were optimized, and under the optimum conditions, the calibration plot was linear in the range 5.0-250.0 μg L^-1. The relative standard deviation was (for n = 5) (RSD) < 3%. The limit of detection (LOD) and the enhancement factor were found to be 2.0 μg L^-1 and 50, respectively. Finally, the accuracy of the method was assessed by comparison of the results with those obtained by direct determination of lead using inductively coupled plasma mass spectrometry (ICP-MS) and spiked real samples. The obtained recoveries were between 92 and 106%. Graphical abstract.

Coadsorption behaviors and mechanisms of Pb(ii) and methylene blue onto a biodegradable multi-functional adsorbent with temperature-tunable selectivity

An entirely bio-degradable adsorbent based on lignin was synthesized by a crosslinking method and the adsorption of methyl blue (MB) and Pb(ii) onto the adsorbent were comparatively investigated, with adsorption behavior and mechanism of the two pollutants on the adsorbent (SLS) being assessed in single and binary systems. According to the results, SLS was capable of effective adsorption using MB and Pb(ii). The adsorption behavior of MB and Pb(ii) followed Langmuir and pseudo-first order models and showed temperature-dependent preferences. At 298 K MB was more preferred while at 318 K Pb(ii) adsorption was more favorable, which means that the selectivity of SLS can be tuned by changing the temperature. From a mechanism aspect, the adsorption of MB and Pb(ii) were both achieved through more than one route. Pb(ii) mainly interacts with sulfonate and hydroxyl groups on SLS, while MB can be bound on both anionic and aromatic groups due to its aromatic nature. Recycling and reuse experiments showed that used SLS can be readily reactivated and stably reused. The findings will guide adsorbent applications in wastewater containing heavy metals and aromatic compounds.

Determination of sulfadimethoxine in milk with aptamer-functionalized Fe3 O4 /graphene oxide as magnetic solid-phase extraction adsorbent prior to HPLC

An aptamer (Apt) functionalized magnetic material was prepared by covalently link Apt to Fe₃ O₄ /graphene oxide (Fe₃ O₄ /GO) composite by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, and then characterized by FTIR spectroscopy, X-ray diffraction, and vibration sample magnetometry. The obtained composite of Fe₃ O₄ /GO/Apt was employed as magnetic solid-phase extraction adsorbent for the selective preconcentration of sulfadimethoxine prior to analysis by high-performance liquid chromatography. Under the optimal conditions (sample pH of 4.0, sorbent dosage of 20 mg, extraction time of 3 h, and methanol-5% acetic acid solution as eluent), a good linear relationship was obtained between the peak area and concentration of sulfadimethoxine in the range of 5.0 to 1500.0 µg/L with correlation coefficient of 0.9997. The limit of detection (S/N = 3) was 3.3 µg/L. The developed method was successfully applied to the analysis of sulfadimethoxine in milk with recoveries in the range of 75.9-92.3% and relative standard deviations less than 8.1%. The adsorption mechanism of Fe₃ O₄ /GO/Apt toward sulfadimethoxine was studied through the adsorption kinetics and adsorption isotherms, and the results show that the adsorption process fits well with the pseudo-second-order kinetic model and the adsorbate on Fe₃ O₄ /GO/Apt is multilayer and heterogeneous.

Recent Advances in Nanomaterials for Analysis of Trace Heavy Metals

In an effort to achieve high sensitivity analysis methods for ultra-trace levels of heavy metals, numerous new nanomaterials are explored for the application in preconcentration processes and sensing systems. Nanomaterial-based methods have proven to be effective for selective analysis and speciation of heavy metals in combination with spectrometric techniques. This review outlined the different types of nanomaterials applied in the field of heavy metal analysis, and concentrated on the latest developments in various new materials. In particular, the functionalization of traditional materials and the exploitation of bio-functional materials could increase the specificity to target metals. The hybridization of multiple materials could improve material properties, to build novel sensor system or achieve detection-removal integration. Finally, we discussed the future perspectives of nanomaterials in the heavy metal preconcentration and sensor design, as well as their respective advantages and challenges. Despite impressive progress and widespread attention, the development of new nanomaterials and nanotechnology is still hampered by numerous challenges, particularly in the specificity to the target and the anti-interference performance in complex matrices.

A ratiometric electrochemical sensor for lead ions based on bismuth film coated porous silicon nanoparticles

A ratiometric electrochemical sensor for the detection of lead ions was developed based on porous silicon nanoparticles with in situ plated bismuth to improve the accuracy and reliability.