Antibacterial and antifungal properties of guanylhydrazones

A series of novel guanylhydrazones were designed, synthesized and characterized. All the compounds were screened for their antibacterial and antifungal activity. Compounds 26 and 27 showed excellent antibacterial activities against Staphylococcus aureus ATCC 25923 and Micrococcus luteus ATCC 379 with minimal inhibitory concentrations of 4 ae g mL(-1), and good antifungal activity against Candida parapsilosis ATCC 22019. These results suggested that the selected guanylhydrazones could serve as promising leads for improved antimicrobial development

Enhanced Antimicrobial Activity of Biocompatible Bacterial Cellulose Films via Dual Synergistic Action of Curcumin and Triangular Silver Nanoplates

Curcumin and triangular silver nanoplates (TSNP)-incorporated bacterial cellulose (BC) films present an ideal antimicrobial material for biomedical applications as they afford a complete set of requirements, including a broad range of long-lasting potency and superior efficacy antimicrobial activity, combined with low toxicity. Here, BC was produced by Komagataeibacter medellinensis ID13488 strain in the presence of curcumin in the production medium (2 and 10%). TSNP were incorporated in the produced BC/curcumin films using ex situ method (21.34 ppm) and the antimicrobial activity was evaluated against Escherichia coli ATCC95922 and Staphylococcus aureus ATCC25923 bacterial strains. Biological activity of these natural products was assessed in cytotoxicity assay against lung fibroblasts and in vivo using Caenorhabditis elegans and Danio rerio as model organisms. Derived films have shown excellent antimicrobial performance with growth inhibition up to 67% for E. coli and 95% for S. aureus. In a highly positive synergistic interaction, BC films with 10% curcumin and incorporated TSNP have shown reduced toxicity with 80% MRC5 cells survival rate. It was shown that only 100% concentrations of film extracts induce low toxicity effect on model organisms’ development. The combined and synergistic advanced anti-infective functionalities of the curcumin and TSNP incorporated in BC have a high potential for development for application within the clinical setting

Composite Films of Thermoplastic Starch and CaCl2 Extracted from Eggshells for Extending Food Shelf-Life

Calcium chloride (CaCl2) has been widely used to maintain the quality of fresh-cut fruits and vegetables because it stabilizes and strengthens the membrane system against fungal attacks. It is mainly applied via spray coating and dip coating techniques. This study explored a method of incorporating calcium chloride extracted from eggshells in a packaging material, thermoplastic starch (TPS), via a hot-melt extrusion process. The composites were characterized by FTIR, DSC, SEM-EDX and tensile testing. FTIR confirmed the chemical reactions between CaCl2 and TPS. DSC results showed a significant decrease in the heat of fusion by adding 20 wt% of CaCl2 content in TPS, indicating a drop in the degree of crystallinity. The Young’s modulus of TPS was not significantly affected by the incorporation of 10 wt% CaCl2 (P = 0.968), but reduced notably with the addition of 20 wt% CaCl2 (P = 0.05), indicating the plasticizer effect of the CaCl2. Physiochemical analysis of fresh-cut apple slices was assessed. Samples placed on the surface of the TPS/CaCl2 composites displayed less pH reduction, reduced antioxidant activity, more weight loss and increased reducing sugar compared to the samples placed on the surface of virgin TPS films. CaCl2 released from the TPS/CaCl2 films was measured and their antimicrobial activity was confirmed by bacterial inhibitory growth assessment. Fungal growth was observed on apple slices placed on virgin TPS film by day 21 while apple slices placed on TPS/CaCl2 20 wt% composites did not support any fungal growth for 28 days. In summary, TPS and eggshell-extracted CaCl2 showed the ability to maintain the quality of fresh-cut apples, and TPS/CaCl2 10 wt% composite could be a good option as a packaging material for fresh-cut fruits due to active antimicrobial activity and maintained Young’s modulus

Antimicrobial Active Bioplastics Using Triangular Silver Nanoplate Integrated Polycaprolactone and Polylactic Acid Films

An innovative antimicrobial technology for plastic surfaces is presented. We report the synthesis and scale-up of triangular silver nanoplates (TSNPs) and their integration into polycaprolactone (PCL) and polylactic acid (PLA) polymers through a solvent-casting technique. The TSNPs have a high geometric aspect ratio and strong local surface plasmon resonance (LSPR) response, which provides an effective tool for monitoring their integrity during processing and integration with the biodegradable plastics. An aqueous-based seed-mediated chemical method was used to synthesize the TSNPs, and characterisation was carried out using TEM and UV (Ultraviolet)-VIS (Visible) spectroscopy to measure LSPR profiles. The UV-VIS spectra of silver seeds and TSNPs exhibited characteristic peaks at 395 and 600 nm respectively. Synthesized TSNPs were coated with thiol-terminated polyethylene glycol (SH-PEG) and transferred into chloroform in order to effect compatibility with PCL and PLA. TSNP/PCL and TSNP/PLA composite films were prepared by solvent casting. The morphological structure, thermal, mechanical, and antimicrobial properties of the TSNP-incorporated composite films were evaluated. Results showed the TSNP-treated films had a rougher surface than the bare films. Insignificant changes in the thermal properties of TSNP-treated films compared to bare ones were also observed, which indicated the thermal stability of the composite films. The tensile strength and antimicrobial properties of the composite films were increased after TSNP incorporation. TSNP/PCL and TSNP/PLA films exhibited improved antimicrobial activity against Escherichia coli and Staphylococcus aureus with antimicrobial effect (AE) values ranging between 0.10 and 0.35. The obtained results and demonstrated TSNP production scalability validate the TSNP treated PCL and PLA films as a composite material with desirable antimicrobial effect for wide-ranging surface applications

Targeting Bacterial Nanocellulose Properties through Tailored Downstream Techniques

Bacterial nanocellulose (BNC) is a biodegradable polysaccharide with unique properties that make it an attractive material for various industrial applications. This study focuses on the strain Komagataeibacter medellinensis ID13488, a strain with the ability to produce high yields of BNC under acidic growth conditions and a promising candidate to use for industrial production of BNC. We conducted a comprehensive investigation into the effects of downstream treatments on the structural and mechanical characteristics of BNC. When compared to alkaline-treated BNC, autoclave-treated BNC exhibited around 78% superior flexibility in average, while it displayed nearly 40% lower stiffness on average. An SEM analysis revealed distinct surface characteristics, indicating differences in cellulose chain compaction. FTIR spectra demonstrated increased hydrogen bonding with prolonged interaction time with alkaline solutions. A thermal analysis showed enhanced thermal stability in alkaline-treated BNC, withstanding temperatures of nearly 300 °C before commencing degradation, compared to autoclaved BNC which starts degradation around 200 °C. These findings provide valuable insights for tailoring BNC properties for specific applications, particularly in industries requiring high purity and specific mechanical characteristics