Study of the interaction mechanism between hydrophilic thiol capped gold nanoparticles and melamine in aqueous medium

Recent advancements in chemosensors for the detection of food spoilage

The need for reliable sensors has become a major requirement to confirm the quality and safety of food commodities. Chemosensors are promising sensing tools to identify contaminants and food spoilage to ensure food safety. Chemosensing materials are evolving and becoming potential mechanisms to enable onsite and real-time monitoring of food safety. This review summarizes the information about the basic four types of chemosensors (colorimetric, optical, electrochemical, and piezoelectric) employed in the food sector, the latest advancements in the development of chemo-sensing mechanisms, and their food applications, with special emphasis on the future outlook of them. In this review, we discuss the novel chemosensors developed from the year 2018 to 2022 to detect spoilage in some common types of food like fish, meat, milk, cheese and soy sauce. This work will provide a fundamental step toward further development and innovations of chemosensors targeting different arenas in the food industry.

Self-assembly of glycoprotein nanostructured filaments for modulating extracellular networks at long range

The intriguing capability of branched glycoprotein filaments to change their hierarchical organization, mediated by external biophysical stimuli, continues to expand understanding of self-assembling strategies that can dynamically rearrange networks at long range. Previous research has explored the corresponding biological, physiological and genetic mechanisms, focusing on protein assemblies within a limited range of nanometric units. Using direct microscopy bio-imaging, we have determined the morpho-structural changes of self-assembled filament networks of the zona pellucida, revealing controlled levels of structured organizations to join distinct evolved stages of the oocyte (Immature, Mature, and Fertilized). This natural soft network reorganizes its corresponding hierarchical network to generate symmetric, asymmetric, and ultimately a state with the lowest asymmetry of the outer surface roughness, and internal pores reversibly changed from elliptical to circular configurations at the corresponding stages. These elusive morpho-structural changes are regulated by the nanostructured polymorphisms of the branched filaments by self-extension/-contraction/-bending processes, modulated by determinate theoretical angles among repetitive filament units. Controlling the nanoscale self-assembling properties by delivering a minimum number of activation bio-signals may be triggered by these specific nanostructured polymorphic organizations. Finally, this research aims to guide this soft biomaterial into a desired state to protect oocytes, eggs, and embryos during development, to favour/prevent the fertilization/polyspermy processes and eventually to impact interactions with bacteria/virus at multiscale levels.

Thiol functionalised gold nanoparticles loaded with methotrexate for cancer treatment: From synthesis to in vitro studies on neuroblastoma cell lines

HYPOTHESIS

Colloidal gold nanoparticles (AuNPs) functionalised with hydrophilic thiols can be used as drug delivery probes, thanks to their small size and hydrophilic character. AuNPs possess unique properties for their use in nanomedicine, especially in cancer treatment, as diagnostics and therapeutic tools.

EXPERIMENTS

Thiol functionalised AuNPs were synthesised and loaded with methotrexate (MTX). Spectroscopic and morphostructural characterisations evidenced the stability of the colloids upon interaction with MTX. Solid state (GISAXS, GIWAXS, FESEM, TEM, FTIR-ATR, XPS) and dispersed phase (UV-Vis, DLS, ζ-potential, NMR, SAXS) experiments allowed to understand structure-properties correlations. The nanoconjugate was tested in vitro (MTT assays) against two neuroblastoma cell lines: SNJKP and IMR5 with overexpressed n-Myc.

FINDINGS

Molar drug encapsulation efficiency was optimised to be >70%. A non-covalent interaction between the π system and the carboxylate moiety belonging to MTX and the charged aminic group of one of the thiols was found. The MTX loading slightly decreased the structural order of the system and increased the distance between the AuNPs. Free AuNPs showed no cytotoxicity whereas the AuNPs-MTX nanoconjugate had a more potent effect when compared to free MTX. The active role of AuNPs was evidenced by permeation studies: an improvement on penetration of the drug inside cells was evidenced.

Efficient preparation of nitrogen-doped lignin-based carbon nanotubes and the selectivity of nitrogen speciation for photothermal therapy

In this study, the lignin was pre-modified using small-molecule nitrogen-containing compounds, and then the nitrogen-doped lignin-based carbon nanotubes (L-NCNTs) were fabricated by pyrolysis using the modified lignin as raw materials. The obtained L-NCNTs were multi-walled carbon nanotubes with diameters between 10 and 80 nm. The modification of lignin had an important effect on the nitrogen morphology of L-NCNTs, and promoted the high selectivity of pyridine-N in the L-NCNTs. Defects and pyridinic-N structure were conducive to boosting photothermal properties of the L-NCNTs. The photothermal conversion efficiency of the L-NCNTs after 808 nm laser irradiation for 5 min reached 58.8 %. The L-NCNTs can be used as photothermal agents in drug delivery system to achieve mild photothermal therapy, and it is basically non-toxic to normal cells, indicating good biocompatibility. This work provides new ideas for development of lignin-based high value-added products from biomass.

Gold Nanoparticles-Based Colorimetric Assays for Environmental Monitoring and Food Safety Evaluation

Recent years have witnessed an exponential increase in the research on gold nanoparticles (AuNPs)-based colorimetric sensors to revolutionize point-of-use sensing devices. Hence, this review is compiled focused on current progress in the design and performance parameters of AuNPs-based sensors. The review begins with the characteristics of AuNPs, followed by a brief explanation of synthesis and functionalization methods. Then, the mechanisms of AuNPs-based sensors are comprehensively explained in two broad categories based on the surface plasmon resonance (SPR) characteristics of AuNPs and their peroxidase-like catalytic properties (nanozyme). SPR-based colorimetric sensors further categorize into aggregation, anti-aggregation, etching, growth-mediated, and accumulation-based methods depending on their sensing mechanisms. On the other hand, peroxidase activity-based colorimetric sensors are divided into two methods based on the expression or inhibition of peroxidase-like activity. Next, the analytes in environmental and food samples are classified as inorganic, organic, and biological pollutants, and recent progress in detection of these analytes are reviewed in detail. Finally, conclusions are provided, and future directions are highlighted. Improving the sensitivity, reproducibility, multiplexing capabilities, and cost-effectiveness for colorimetric detection of various analytes in environment and food matrices will have significant impact on fast testing of hazardous substances, hence reducing the pollution load in environment as well as rendering food contamination to ensure food safety.

Recent Advances in Electrochemical Chitosan-Based Chemosensors and Biosensors: Applications in Food Safety

Chitosan is a biopolymer derived from chitin. It is a non-toxic, biocompatible, bioactive, and biodegradable polymer. Due to its properties, chitosan has found applications in several and different fields such as agriculture, food industry, medicine, paper fabrication, textile industry, and water treatment. In addition to these properties, chitosan has a good film-forming ability which allows it to be widely used for the development of sensors and biosensors. This review is focused on the use of chitosan for the formulation of electrochemical chemosensors. It also aims to provide an overview of the advantages of using chitosan as an immobilization platform for biomolecules by highlighting its applications in electrochemical biosensors. Finally, applications of chitosan-based electrochemical chemosensors and biosensors in food safety are illustrated.