Search

BACKGROUND: The present study investigates the physical, chemical, and antibacterial properties of water‐soluble chitosan derivatives. Preparation of the water‐soluble chitosan derivatives was performed by the Maillard reaction (MR) between chitosan [with the degree of deacetylation (DD) being 50%, 70%, and 90%] and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan–mannose MR products (Mc‐mrps), were carried out. RESULTS: Based on the experimental data obtained from Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, Pyrolysis‐gas chromatography‐mass spectrometry analysis, and 1H‐NMR, the Mc‐mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△E), and solubility (P < 0.05). The zeta potential and particle size of the Mc‐mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram‐positive (Staphylococcus aureus and Bacillus subtilis) and Gram‐negative bacteria (Escherichia coli and Salmonella typhimurium), as well as antioxidant activity, were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan. CONCLUSION: The results of the present study suggest that chitosan was derived with mannose to yield a novel, water‐soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc‐mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

To explore a novel colorimetric biosensor with high sensibility and selectivity, a new Wells–Dawson-type polyoxometalate (POM)-based metal–organic framework (MOF) with an eightfold helix, [Cu9(FKZ)12(H2O)8][H3P2W18O62]2·4H2O (CuFKZP2W18) (HFKZ = 1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-1-yl)methyl] ethanol), was successfully synthesized; then, polypyrrole (PPy) was introduced to fabricate CuFKZP2W18/PPy(n) nanocomposites (n = 7%, 15%, 30%) via a facile in situ oxidation polymerization process. All the results indicate that CuFKZP2W18/PPy(15%) as a colorimetric biosensor exhibits lower limits of detection (0.07 μM towards H2O2 and 0.627 μM towards ascorbic acid), smaller Km values (0.106 mM for H2O2 and 0.042 mM for o-phenylenediamine) and higher sensitivity (0.0227 1 μM−1 towards H2O2 and 0.0025 1 μM−1 to ascorbic acid) than most reported enzyme mimetics to the best of our knowledge. [ABSTRACT FROM AUTHOR]

To overcome the poor conductivities and promote the application in the biosensors of metal-organic frameworks (MOFs), a simple approach was employed to improve their overall conductivity by adjusting the metal centers of MOFs and coating conductive polypyrrole (PPy) in the work. An unprecedented molybdenum oxide-based three-dimensional MOFs with helical channels (CuTRZMoO 4) was synthesized based on MoO 4 −, Cu2+ ions and 1,2,3-trz for the first time, then combined with PPy to fabricate hybrid composites (CuTRZMoO 4 @PPy-n) with both advantages. The CuTRZMoO 4 modified glassy carbon electrode show high sensitivity for detecting the neurotransmitter dopamine (DA), and the CuTRZMoO 4 @PPy-2 modified glassy carbon electrode has the highest catalytical activity to DA with the linear detection range from 1 μM to 100 μM and the detection limit of 80 nM (S/N = 3) by differential pulse voltammetry (DPV). Moreover, the developed biosensor has good selectivity, reproducibility and stability. The concept behinds the new architecture to modify electrodes should promote the further development of MOF-based biosensors. A high active, non-noble MOF based biosensing platform by adjusting the metal centers of MOFs and employing conductive polypyrrole (PPy) for enhancing detection of dopamine (DA) was developed for the first time. Image 1 • Molybdenum oxide-based metal-organic framework ([Cu 3 (trz) 2 (MoO 4) 2 ]·H 2 O) were synthesized. • Adjusting the metal centers of Mo based MOFs and employing conductive PPy to dopamine (DA) detection is discussed. • The CuTRZMoO 4 @PPy exhibit the excellent detection of DA with wide linear detection range and very low limit of detection. [ABSTRACT FROM AUTHOR]