A portable thermal detection method based on the target responsive hydrogel mediated self-heating of a warming pad

Scalable one-step fabrication of integrated electrode arrays for highly sensitive and portable carbendazim detection

Highly sensitive and portable pesticide residues detection are indispensable for safeguarding food safety and environmental health. Herein, we introduce a one-step vacuum filtration strategy for the scalable production of cobalt-based conjugated coordination polymers (CoCCPs) electrode arrays, utilizing carboxylated single-walled carbon nanotubes (c-SWNTs) as bonding bridges (CoCCPs@c-SWNTs). Due to their abundant active sites and high conductivity, the CoCCPs@c-SWNTs arrays exhibit superior electrochemical performance (e.g., active area, charge transfer capacity, adsorbed charge, etc.) and enhanced electrocatalytic activity for carbendazim (CBZ). Benefiting from the homogeneous and twining interface, the CoCCPs@c-SWNTs arrays also demonstrate good repeatability, reproducibility, and stability (relative standard deviations <5 %). The CoCCPs@c-SWNTs sensor, with a linear range of 0.01-4.0 μM and a detection limit of 1.9 nM, has been successfully employed in tea and strawberry samples. Overall, this novel sensor holds great potential for application in rapid on-site detection of pesticide residues.

Overview of the Design and Application of Photothermal Immunoassays

Developing powerful immunoassays for sensitive and real-time detection of targets has always been a challenging task. Due to their advantages of direct readout, controllable sensing, and low background interference, photothermal immunoassays have become a type of new technology that can be used for various applications such as disease diagnosis, environmental monitoring, and food safety. By modification with antibodies, photothermal materials can induce temperature changes by converting light energy into heat, thereby reporting specific target recognition events. This article reviews the design and application of photothermal immunoassays based on different photothermal materials, including noble metal nanomaterials, carbon-based nanomaterials, two-dimensional nanomaterials, metal oxide and sulfide nanomaterials, Prussian blue nanoparticles, small organic molecules, polymers, etc. It pays special attention to the role of photothermal materials and the working principle of various immunoassays. Additionally, the challenges and prospects for future development of photothermal immunoassays are briefly discussed.

Hydrogel-integrated sensors for food safety and quality monitoring: Fabrication strategies and emerging applications

Food safety is a global issue in public hygiene. The accurate, sensitive, and on-site detection of various food contaminants performs significant implications. However, traditional methods suffer from the time-consuming and professional operation, restricting their on-site application. Hydrogels with the merits of highly porous structure, high biocompatibility, good shape-adaptability, and stimuli-responsiveness offer a promising biomaterial to design sensors for ensuring food safety. This review describes the emerging applications of hydrogel-based sensors in food safety inspection in recent years. In particular, this study elaborates on their fabrication strategies and unique sensing mechanisms depending on whether the hydrogel is stimuli-responsive or not. Stimuli-responsive hydrogels can be integrated with various functional ligands for sensitive and convenient detection via signal amplification and transduction; while non-stimuli-responsive hydrogels are mainly used as solid-state encapsulating carriers for signal probe, nanomaterial, or cell and as conductive media. In addition, their existing challenges, future perspectives, and application prospects are discussed. These practices greatly enrich the application scenarios and improve the detection performance of hydrogel-based sensors in food safety detection.

Recent Studies and Applications of Hydrogel-Based Biosensors in Food Safety

Food safety has increasingly become a human health issue that concerns all countries in the world. Some substances in food that can pose a significant threat to human health include, but are not limited to, pesticides, biotoxins, antibiotics, pathogenic bacteria, food quality indicators, heavy metals, and illegal additives. The traditional methods of food contaminant detection have practical limitations or analytical defects, restricting their on-site application. Hydrogels with the merits of a large surface area, highly porous structure, good shape-adaptability, excellent biocompatibility, and mechanical stability have been widely studied in the field of food safety sensing. The classification, response mechanism, and recent application of hydrogel-based biosensors in food safety are reviewed in this paper. Furthermore, the challenges and future trends of hydrogel biosensors are also discussed.

Multiorbital DNA walker nanoprobe for portable photothermal detection based on H2S etching of cubic Prussian blue

In the developed assay, multiorbital 3D DNA walker (MO DNA walker) was applied as signal amplified protocol for enhancing the detection signal of the photothermal biosensor, which was designed for sensitive detection of miRNA based on the H2S triggered conversation of photothermal reagent. When the target molecule is present, the DNA walking strand was released and then hybridize with track strands. The landing of walking particles (WPT) on the tracking particles (TPT) promotes the relative movement of the WPT around TPT, thus releasing large amount of horseradish peroxidase (HRP) with the aid of DNAzyme. After reacting with Na2S2O3 and H2O2, multiple H2S can be generated in situ based on the catalytic ability of HRP. Meanwhile, cubic Prussian blue (CPB) was synthesized and exhibited superior photothermal response, which can be served as efficient photothermal reagent and H2S responsive acceptor. Significantly, the photothermal signal of CPB could be obviously reduced after challenged with H2S ascribed to synchronous reaction between the ferric ion (Fe3+) and H2S. The improved walking area and freedom enable significant signal amplification, enhancing the biosensor's performance. Under ideal circumstances, the proposed photothermal assay demonstrated excellent performance for determination of miRNA-21.

Stimulus-Responsive DNA Hydrogel Biosensors for Food Safety Detection

Food safety has always been a major global challenge to human health and the effective detection of harmful substances in food can reduce the risk to human health. However, the food industry has been plagued by a lack of effective and sensitive safety monitoring methods due to the tension between the cost and effectiveness of monitoring. DNA-based hydrogels combine the advantages of biocompatibility, programmability, the molecular recognition of DNA molecules, and the hydrophilicity of hydrogels, making them a hotspot in the research field of new nanomaterials. The stimulus response property greatly broadens the function and application range of DNA hydrogel. In recent years, DNA hydrogels based on stimulus-responsive mechanisms have been widely applied in the field of biosensing for the detection of a variety of target substances, including various food contaminants. In this review, we describe the recent advances in the preparation of stimuli-responsive DNA hydrogels, highlighting the progress of its application in food safety detection. Finally, we also discuss the challenges and future application of stimulus-responsive DNA hydrogels.

Design and application of stimuli-responsive DNA hydrogels: A review

Deoxyribonucleic acid (DNA) hydrogels combine the properties of DNAs and hydrogels, and adding functionalized DNAs is key to the wide application of DNA hydrogels. In stimuli-responsive DNA hydrogels, the DNA transcends its application in genetics and bridges the gap between different fields. Specifically, the DNA acts as both an information carrier and a bridge in constructing DNA hydrogels. The programmability and biocompatibility of DNA hydrogel make it change macroscopically in response to a variety of stimuli. In order to meet the needs of different scenarios, DNA hydrogels were also designed into microcapsules, beads, membranes, microneedle patches, and other forms. In this study, the stimuli were classified into single biological and non-biological stimuli and composite stimuli. Stimuli-responsive DNA hydrogels from the past five years were summarized, including but not limited to their design and application, in particular logic gate pathways and signal amplification mechanisms. Stimuli-responsive DNA hydrogels have been applied to fields such as sensing, nanorobots, information carriers, controlled drug release, and disease treatment. Different potential applications and the developmental pro-spects of stimuli-responsive DNA hydrogels were discussed.