Nanotechnology-based analytical techniques for the detection of contaminants in aquatic products

Food safety of aquatic products has attracted considerable attention worldwide. Although a series of conventional bioassays and instrumental methods have been developed for the detection of pathogenic bacteria, heavy metal residues, marine toxins, and biogenic amines during the production and storage of fish, shrimp, crabs et al., the nanotechnology-based analyses still have their advantages and are promising since they are cost-efficient, highly sensitive and selective, easy to conduct, facial design, often require no sophisticated instruments but with excellent detection performance. This review aims to summarize the advances of various biosensing strategies for bacteria, metal ions, and small molecule contaminants in aquatic products during the last five years, The review highlights the development in nanotechnologies applied for biorecognition process, signal transduction and amplification methods in each novel approach, the nuclease-mediated DNA amplification, nanomaterials (noble metal nanoparticle, metal-organic frameworks, carbon dots), lateral flow-based biosensor, surface-enhanced Raman scattering, microfluidic chip, and molecular imprinting technologies were especially emphasized. Moreover, this study provides a view of current accomplishments, challenges, and future development directions of nanotechnology in aquatic product safety evaluation.

Colorimetric detection of heavy metal ions with various chromogenic materials: Strategies and applications

Detection of heavy metal ions has drawn significant attention in environmental and food area due to their threats to the human health and ecosystem. Colorimetry is one of the most frequently-used methods for the detection of heavy metal ions owing to its simplicity, easy operation and rapid on-site detection. The development of chromogenic materials and their sensing mechanisms are the key research direction in the area of colorimetric method. Since each chromogenic material has their unique optical and chemical properties, they have totally different colorimetric sensing mechanisms. This review focuses on the chromogenic materials and their sensing strategies for the colorimetric detection of heavy metal ions. We divide the chromogenic materials into three types, including organic materials, inorganic materials, and other materials. As for each type of chromogenic material, we discuss their detailed sensing strategies, sensing performance, and real sample applications. Moreover, current challenges and perspectives related to the colorimetry of heavy metal ions are also discussed in this review. The aim of this review is to help readers to better understand the principles of colorimetric methods for heavy metal ions and push the development of rapid detection of heavy metal ions.

Carbon Nanotube and Its Derived Nanomaterials Based High Performance Biosensing Platform

After the COVID-19 pandemic, the development of an accurate diagnosis and monitoring of diseases became a more important issue. In order to fabricate high-performance and sensitive biosensors, many researchers and scientists have used many kinds of nanomaterials such as metal nanoparticles (NPs), metal oxide NPs, quantum dots (QDs), and carbon nanomaterials including graphene and carbon nanotubes (CNTs). Among them, CNTs have been considered important biosensing channel candidates due to their excellent physical properties such as high electrical conductivity, strong mechanical properties, plasmonic properties, and so on. Thus, in this review, CNT-based biosensing systems are introduced and various sensing approaches such as electrochemical, optical, and electrical methods are reported. Moreover, such biosensing platforms showed excellent sensitivity and high selectivity against not only viruses but also virus DNA structures. So, based on the amazing potential of CNTs-based biosensing systems, healthcare and public health can be significantly improved.

Nanoarmored Multi-Enzyme Cascade Catalysis

This chapter reports a single-step preparation of nanoarmored bi-enzyme systems assembled on 1-D and 2-D nanomaterials, with glucose oxidase and peroxidase enzymes as model systems for cascade bio-catalysis. This is a simple and facile method to both exfoliate the bulk 1D (carbon nanotubes, CNT) and 2D nanomaterials (α-Zirconium phosphate, α-ZrP) and bind the enzymes in a single step. Exfoliation of the bulk material enhances the accessible surface area of the materials for the enzyme binding, and it also boosts the diffusion of reagents from the bulk phase to the active sites of the bio-catalysts. For example, a mixture of horseradish peroxidase, glucose oxidase, and bovine serum albumin (BSA) were adsorbed on the surfaces of the α-ZrP nanoplates or carbon nanotubes (CNT) as the bulk materials are exfoliated simultaneously, in a one-step process. The resulting bio-catalysts were thoroughly characterized by powder X-ray diffraction, electron microscopy, biochemical and biophysical methods, while enzyme activity studies proved successful binding of enzymes with retention of activities or even enhancements in their specific activities. For example, GOx/HRP/BSA/CNT displayed 6 times the activity of a mixture of GOx/HRP/BSA, under otherwise identical conditions. Similarly, GOx/HRP/BSA/ZrP had 3.5 times the activity of the corresponding mixture of GOx/HRP/BSA, in the absence of the nanoplates. These robust nano-dispersions worked extraordinarily well as active bio-catalysts. These two kinds of fabricated biocatalyst dispersions are also highly stable.

Recent advances and perspectives of enzyme-based optical biosensing for organophosphorus pesticides detection

The overuse or abuse of organophosphorus pesticides (OPs) can bring about severe contamination problems in foodstuff and the environment, which will seriously threaten human health and the ecosystem's cycle. Hence, it is in high demand to establish sensitive, portable, specific, and cost-effective methods for monitoring OPs to control food safety, protect the ecosystem, and prevent disease. The optical biosensor with enzyme as bio-recognition elements has been an effective alternative for OPs detection. Herein, we firstly introduce various enzymes, sensing mechanisms, advantages and disadvantages used as bio-recognition elements in optical sensing for OPs detection. Then, we review various optical biosensing strategies based on enzymes as recognition elements that were ingeniously designed and successfully utilized for OPs detection, with a particular emphasis on photoluminescence (PL), chemiluminescence (CL), electrochemiluminescence (ECL), and colorimetric (CM) biosensing strategies. We not only highlight the state-of-art developments and the construction strategies of the enzyme-based optical biosensing method but also summarize the existing deficiencies, current challenges, and the future perspectives of OPs detection.

Towards the development of flexible carbon nanotube–parafilm nanocomposites and their application as bioelectrodes

Soft, flexible and conductive interfaces, which can be used as electrode materials integrated with commercial electronic components and the human body for continuous monitoring of different analytes are in high demand in wearable electronics.

A sensitive “ON–OFF” fluorescent probe based on carbon dots for Fe2+ detection and cell imaging

A sensitive fluorescent probe based on carbon dots has been synthesized by a one-pot hydrothermal method for the rapid detection of intracellular Fe²⁺.

Twisted intramolecular charge transfer (TICT) based fluorescent probe for lighting up serum albumin with high sensitivity in physiological conditions

Accurate detection of human serum albumin (HSA) in biological samples is quite meaningful for early disease diagnosis and treatment. Herein, a novel fluorescent probe 1-ethyl-4-[2-[4-(diethylamino)-2-hydroxyphenyl]ethenyl]]-pyridinium salt (DEHP) was developed for HSA determination. The inherent fluorescence of DEHP is essentially negligible at physiological conditions assigned to the well-developed twisted intramolecular charge transfer (TICT) protocol. An intriguing fluorescence light up is triggered as the addition of HSA, on account of the inhibited TICT procedure when DEHP enters the hydrophobic cavity of protein HSA. This combination leads to a turn on fluorescent response for HSA with a detection limit of 4.8 nM. After an overall investigation, it has been proved that the strong binding between DEHP and HSA is specific-site-related. In additional, the probe implies a great potential to assist clinical diagnosis due to the usage in actual serum detection. Cell imaging also shows that the probe is expected to monitor HSA production process at cell level.

Colorimetric method for glucose detection with enhanced signal intensity using ZnFe2O4-carbon nanotube-glucose oxidase composite material

In this paper, a composite material comprised of ZnFe2O4 nanomaterial, carbon nanotubes (CNT) and glucose oxidase (GOD) was synthesized and used for glucose detection. ZnFe2O4-CNT was formed by a one-step solvothermal approach using acid-treated CNT as precursor, then GOD was linked to it by coupling reaction between -NH2 and -COOH. After addition of glucose, which is oxidized by GOD, the intermediate product (H2O2) further oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) substrate and forms a blue product. This process was accelerated in the presence of peroxidase-mimic ZnFe2O4 nanomaterial and the detected signal intensity was correspondingly enhanced. The linear detection range of glucose was 0.8 to 250 μM, with a limit of detection of 0.58 μM. This may originate from (1) the limited diffusion of intermediate species, which resulted in enhanced local concentrations of reaction compounds; (2) enhanced electron transmission among CNT, GOD and ZnFe2O4; (3) the synergistic enhancement of catalytic activity of ZnFe2O4 compared with other metal oxides; (4) the high loading capacity of ZnFe2O4-CNT for GOD molecules, because of its high surface-to-volume ratio. Meanwhile, this method has reasonable selectivity, stability and reusability and can be used for real serum detection, which may be useful for the development of sensitive biosensors.