Longitudinal surface plasmon resonance assay enhanced by magnetosomes for simultaneous detection of Pefloxacin and Microcystin-LR in seafoods

Molecular imprinting-based indirect fluorescence detection strategy implemented on paper chip for non-fluorescent microcystin

Fluorescence analysis is a fast and sensitive method, and has great potential application in trace detection of environmental toxins. However, many important environmental toxins are non-fluorescent substances, and it is still a challenge to construct a fluorescence detection method for non-fluorescent substances. Here, by means of charge transfer effect and smart molecular imprinting technology, we report a sensitive indirect fluorescent sensing mechanism (IFSM) and microcystin (MC-RR) is selected as a model target. A molecular imprinted thin film is immobilized on the surface of zinc ferrite nanoparticles (ZnFe2O4 NPs) by using arginine, a dummy fragment of MC-RR. By implementation of IFSM on the paper-based microfluidic chip, a versatile platform for the quantitative assay of MC-RR is developed at trace level (the limit of detection of 0.43 μg/L and time of 20 min) in real water samples without any pretreatment. Importantly, the proposed IFSM can be easily modified and extended for the wide variety of species which lack direct interaction with the fluorescent substrate. This work offers the potential possibility to meet the requirements for the on-site analysis and may explore potential applications of molecularly imprinted fluorescent sensors.

Biomedical applications of magnetosomes: State of the art and perspectives

Magnetosomes, synthesized by magnetotactic bacteria (MTB), have been used in nano- and biotechnological applications, owing to their unique properties such as superparamagnetism, uniform size distribution, excellent bioavailability, and easily modifiable functional groups. In this review, we first discuss the mechanisms of magnetosome formation and describe various modification methods. Subsequently, we focus on presenting the biomedical advancements of bacterial magnetosomes in biomedical imaging, drug delivery, anticancer therapy, biosensor. Finally, we discuss future applications and challenges. This review summarizes the application of magnetosomes in the biomedical field, highlighting the latest advancements and exploring the future development of magnetosomes.

Cell-Based Metabolomics Approach for Anticipating and Investigating Cytotoxicity of Gold Nanorods

Despite the increasing application of gold nanoparticles, there has been little assessment of biological system toxicity to evaluate their potential impact on human health. In this study, the human hepatoma cell line (Hep G2) was used in a metabolomics approach to study the effects of shape, time, and dose of gold nanorods (GNRs). Using optimized parameters for chromatography and mass spectrometry, the metabolites detected by GC-MS were processed with MS DIAL and identified with Fiehnlib. Key metabolic pathways affected by GNRs were identified by endo-metabolic profiling of cells mixed with GNRs of varying shape while varying the dose and time of exposure. The shape of GNRs affected cytotoxicity, and short GNR (GNR-S) triggered disorder of cell metabolism. High concentrations of GNRs caused more significant toxicity. The cytotoxicity and bioTEM results illustrated that the mitochondria toxicity, as the main cytotoxicity of GNRs, caused declining cytoprotective ability. The mitochondrial dysfunction disrupted alanine, aspartate, glutamate, arginine, and proline metabolism, with amino acid synthesis generally downregulated. However, the efflux function of cells can exclude GNRs extracellularly within 24 h, resulting in reduced cell mitochondrial metabolic toxicity and allowing metabolic disorders to recover to normal function.

Development of a colloidal gold immunochromatographic strip for the rapid detection of pefloxacin in grass carp with a novel pretreatment method

A rapid colloidal gold immunochromatography assay (GICA) for the detection of pefloxacin (PEF) was established and optimized. The anti-PEF monoclonal antibody (mAb) was used to target PEF as a colloidal gold-mAb conjugate. The mAb belonged to the IgG2b subtype, lambda light chain, the affinity constant (Ka) was 5.21 × 10⁹ L·mol^-1, and its half maximal inhibitory concentration (IC₅₀) was 0.23 ng·mL^-1. No obvious cross-reactivity (CR) was observed with other common fluoroquinolone antibiotics, including ciprofloxacin (CIP), norfloxacin (NOR), lomefloxacin (LOM) and ofloxacin (OFL). The visual limit of detection (vLOD) of the optimized GICA was 2 ng·g^-1 under the conventional pretreatment method, and the assay was completed in 15 min. Liquid chromatography tandem-mass spectrometry (LC-MS/MS) was employed to confirm the performance of the strip. In addition, a novel pretreatment was established and compared with conventional pretreatment. Without the removal of organic solvents, the novel pretreatment method reduced the sample pretreatment time (more than 10 min). The vLOD of the optimized GICA was also 2 ng·g^-1 when applying the novel pretreatment method. In conclusion, the proposed PEF-GICA could detect samples containing PEF rapidly and accurately, and the novel pretreatment method saved the time of sample pretreatment and improved the efficiency of detection.

Improving Biosensors by the Use of Different Nanomaterials: Case Study with Microcystins as Target Analytes

The eutrophication of lakes and rivers without adequate rainfall leads to excessive growth of cyanobacterial harmful algal blooms (CyanoHABs) that produce toxicants, green tides, and unpleasant odors. The rapid growth of CyanoHABs owing to global warming, climate change, and the development of rainforests and dams without considering the environmental concern towards lakes and rivers is a serious issue. Humans and livestock consuming the toxicant-contaminated water that originated from CyanoHABs suffer severe health problems. Among the various toxicants produced by CyanoHABs, microcystins (MCs) are the most harmful. Excess accumulation of MC within living organisms can result in liver failure and hepatocirrhosis, eventually leading to death. Therefore, it is essential to precisely detect MCs in water samples. To date, the liquid chromatography-mass spectrometry (LC-MS) and enzyme-linked immunosorbent assay (ELISA) have been the standard methods for the detection of MC and provide precise results with high reliability. However, these methods require heavy instruments and complicated operation steps that could hamper the portability and field-readiness of the detection system. Therefore, in order for this goal to be achieved, the biosensor has been attracted to a powerful alternative for MC detection. Thus far, several types of MC biosensor have been proposed to detect MC in freshwater sample. The introduction of material is a useful option in order to improve the biosensor performance and construct new types of biosensors. Introducing nanomaterials to the biosensor interface provides new phenomena or enhances the sensitivity. In recent times, different types of nanomaterials, such as metallic, carbon-based, and transition metal dichalcogenide-based nanomaterials, have been developed and used to fabricate biosensors for MC detection. This study reviews the recent advancements in different nanomaterial-based MC biosensors.

A new method based on diffusive gradients in thin films for in situ monitoring microcystin-LR in waters

The passive sampling method of diffusive gradients in thin-films (DGT) was developed to provide a quantitative and time-integrated measurement of microcystin-LR (MC-LR) in waters. The DGT method in this study used HLB (hydrophilic-lipophilic-balanced) material as a binding agent, and methanol as an eluent. The diffusion coefficient of MC-LR was 5.01 × 10⁻⁶ cm² s⁻¹ at 25 °C in 0.45 mm thick diffusion layer. This DGT method had a binding capacity of 4.24 μg per binding gel disk (3.14 cm²), ensuring sufficient capacity to measure MC-LR in most water matrices. The detection limit of HLB DGT was 0.48 ng L⁻¹. DGT coupled to analysis by HPLC appears to be an accurate method for MC-LR monitoring. Comparison of DGT measurements for MC-LR in water and a conventional active sampling method showed little difference. This study demonstrates that HLB-based DGT is a useful tool for in situ monitoring of MC-LR in fresh waters.

Localized surface plasmon resonance based biosensing

INTRODUCTION

Bioanalytical sensing based on the principle of localized surface plasmon resonance experiences is currently an extremely rapid development. Novel sensors with new kinds of plasmonic transducers and innovative concepts for the signal development as well as read-out principles were identified. This review will give an overview of the development of this field. Areas covered: The focus is primarily on types of transducers by preparation or dimension, factors for optimal sensing concepts and the critical view of the usability of these devices as innovative sensors for bioanalytical applications. Expert commentary: Plasmonic sensor devices offer a high potential for future biosensing given that limiting factors such as long-time stability of the transducers, the required high sensitivity and the cost-efficient production are addressed. For higher sensitivity, the design of the sensor in shape and material has to be combined with optimal enhancement strategies. Plasmonic nanoparticles from bottom-up synthesis with a post-synthetic processing show a high potential for cost-efficient sensor production. Regarding the measurement principle, LSPRi offers a large potential for multiplex sensors and can provide a high-throughput as well as highly paralleled sensing. The main trends are expected towards optimal LSPR concepts which represent cost-efficient and robust point-of-care solutions, and the use of multiplexed devices for clinical applications.

Novel Biomimic Crystalline Colloidal Array for Fast Detection of Trace Parathion

A novel gold doped inverse opal photonic crystal (IO PC) was successfully fabricated with combination of molecularly imprinted technical for the fast determination of parathion. First, a closest silica array arrangement behaved as the 3D photonic crystal precursors to build the opal photonic crystal (O PC). Second, the parathion-containing polymeric solution with gold nanoparticles was drawn into the 3D array cracks. After polymerization, the well-designed O PC was treated with HF solution for the etching of the silica skeleton. Finally, the template parathion was removed and the Au-MIP IO PCs were obtained. The morphology of SiO₂ and Au NPs was characterized by transmission electron microscopy (TEM), and the eluted influence of the IO PCs was monitored by scanning electron microscopy (SEM). The cross-linking effect was well optimized according to the best spectrum signal of parathion. The as-synthesized Au-MIP IO PCs displayed the specificity toward parathion and the selectivity to other competitive pesticide molecules. The response time was only 5 min, and the parathion could be well detected from real water samples. The recoveries were between 95.5% and 101.5%.

Magnetotactic bacteria: nanodrivers of the future

Magnetotactic bacteria (MTB) represent a heterogeneous group of Gram-negative aquatic prokaryotes with a broad range of morphological types, including vibrioid, coccoid, rod and spirillum. MTBs possess the virtuosity to passively align and actively swim along the magnetic field. Magnetosomes are the trademark nano-ranged intracellular structures of MTB, which comprise magnetic iron-bearing inorganic crystals enveloped by an organic membrane, and are dedicated organelles for their magnetotactic lifestyle. Magnetosomes endue high and even dispersion in aqueous solutions compared with artificial magnetites, claiming them as paragon nanomaterials. MTB and magnetosomes offer high technological potential in modern science, technology and medicines. This review focuses on the applicability of MTB and magnetosomes in various areas of modern benefits.

Development of an ELISA and immunochromatographic strip for highly sensitive detection of microcystin-LR

A monoclonal antibody for microcystin-leucine-arginine (MC-LR) was produced by cell fusion. The immunogen was synthesized in two steps. First, ovalbumin/ bovine serum albumin was conjugated with 6-acetylthiohexanoic acid using a carbodiimide EDC (1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride)/ NHS (N-hydroxysulfosuccinimide) reaction. After dialysis, the protein was reacted with MC-LR based on a free radical reaction under basic solution conditions. The protein conjugate was used for immunization based on low volume. The antibodies were identified by indirect competitive (ic)ELISA and were subjected to tap water and lake water analysis. The concentration causing 50% inhibition of binding of MC-LR (IC50) by the competitive indirect ELISA was 0.27 ng/mL. Cross-reactivity to the MC-RR, MC-YR and MC-WR was good. The tap water and lake water matrices had no effect on the detection limit. The analytical recovery of MC-LR in the water samples in the icELISA was 94%-110%. Based on this antibody, an immunochromatographic biosensor was developed with a cut-off value of 1 ng/mL, which could satisfy the requirement of the World Health Organization for MC-LR detection in drinking water. This biosensor could be therefore be used as a fast screening tool in the field detection of MC-LR.

Toxicological evaluation of microcystins in aquatic fish species: current knowledge and future directions

Microcystins (MCs) are algal toxins produced intracellularly within the algal cells, and are subsequently released into the aquatic systems. An increase in the frequency and intensity of occurrence of harmful algal blooms has directed the global attention towards the presence of MCs in aquatic systems. The effects of MCs on fish have been verified in a number of studies including histological, biochemical and behavioral effects. The toxicological effects of MCs on different organs of fish are related to the exposure route (intraperitoneal injection, feeding or immersion), the mode of uptake (passive or active transport) as well as biotransformation and bioaccumulation capabilities by different organs. This paper reviews the rapidly expanding literature on the toxicological evaluation of MCs in fish from both field studies and controlled laboratory experimental investigations, integrates the current knowledge available about the mechanisms involved in MC-induced effects on fish, and points out future research directions from a cross-disciplinary perspective. In addition, the need to carry out systematic fish toxicity studies to account for possible interactions between MCs and other environmental pollutants in aquatic systems is discussed.