Self-healing composite hydrogel with antibacterial and reversible restorability conductive properties.

Self-healable PAA/PPy-Fe composite hydrogels have been simply synthesized in one step and utilized for antibacterial and electrical conductivity application. The network of hydrogel is composed of polyacrylic acid (PAA) and Fe3+ ions with interlacing of the second polymeric chain of polypyrrole (PPy). In this study, ammonium persulfate (APS) was utilized to initiate the polymerization of both acrylic acid and pyrrole. Such hydrogels exhibited good mechanical properties and remarkable self-healing efficiency as well. The self-healing ability of the hydrogels was facilitated by ionic interaction between carboxylic anion groups (COO-) from polyacrylic acid (PAA) and Fe3+ ions. Moreover, the antibacterial activity of the composite hydrogels was examined on Escherichia coli via the disk diffusion method and the zone of inhibition was obtained in the range of 1.26-1.56 cm after incubation for 12 h. In addition, demonstration of the PAA/PPy-Fe composite hydrogels in electrical conductivity applications was performed in which the composite hydrogel was set up in an electrical circuit consisting of an LED and powered by 3 V batteries. The results showed that the electricity could light-up the LED through the PAA/PPy-Fe composite hydrogels and possessed reversible restorability, as indicated by the healed hydrogel consistently lighting-up the LED in the electrical circuit.

Direct biodiesel production from wet spent coffee grounds.

Utilization of waste spent coffee grounds (SCG) remains limited and requires pre-treatment before being discarded to avoid pollution to the environment. Lipids contained in SCG could be converted to biodiesel through an in situ transesterification method. Current in situ transesterification of wet SCG biomass, conducted at high reaction temperature to reduce the water effect and reduce reaction time, is energy intensive. A new approach, which combines simultaneous extraction-transesterification in a single step using soxhlet apparatus, was developed to produce biodiesel directly from wet SCG biomass. A homogeneous base catalyst at a concentration of 0.75 M showed better catalytic activity than acid, with hexane as a co-solvent on fatty acid (FA) extraction efficiency and FA to fatty acid methyl ester (FAME) conversion efficiency. Studying the factorial effect of ratio of methanol to hexane and reaction time led to the highest FA to FAME conversion efficiency of 97% at a ratio of 1 : 2 and 30 min reaction time. In addition, the catalyst could be used five times without losing its activity. In term of energy consumption, the reactive extraction soxhlet (RES) method could save 38-99% of energy compared to existing methods.

A simple one-pot fabrication of silver loaded semi-interpenetrating polymer network (IPN) hydrogels with self-healing and bactericidal abilities.

In the last decade, there has been a significant increase in the development of self-healing hydrogels. However, in most cases, the synthesized self-healing hydrogels possess no antibacterial properties. Further, the preparation of self-healing hydrogels usually requires sophisticated processes and also involves multiple steps. Herein, we proposed a simple one-pot synthesis of silver loaded semi-IPN hydrogels with self-healing and antibacterial properties. The hydrogels were prepared by physical cross-linking between polyacrylic acid (PAA) and ferric ions (Fe3+) and further modified by the interpenetration of gelatin-silver in the networks. In addition, the effect by varying the gelatin concentration was also studied. The mechanical properties of the as-prepared hydrogels reached 0.79 MPa in stress and 920% in strain with the self-healing efficiency of 87.5% (healed at 70 °C for 2 h). As displayed by the SEM images, the incorporated silver chloride nanoparticles (AgCl NPs) in gelatin-free hydrogels were agglomerated. Meanwhile, well-distributed AgCl NPs in the hydrogels were obtained in the presence of gelatin which acts as a stabilizer. Moreover, due to Fe3+ and AgCl NPs, the hydrogels were able to inhibit the growth of bacteria indicated by an inhibition zone (9-9.6 mm) which was examined toward Escherichia coli via the disk-diffusion method.

Preparation of In Situ Cross-Linked N-Maleoyl Chitosan-Oxidized Sodium Alginate Hydrogels for Drug Delivery Applications.

AIM: This study was aimed to prepare in situ cross-linked N-maleoyl chitosan - oxidised sodium alginate (MCS - OSA) hydrogel loaded with metronidazole (MTZ) for drug delivery applications. METHODS: The hydrogel was prepared by in situ cross-linking via Schiff base reaction between amine (-NH2) groups from MCS and aldehyde (-CHO) groups from OSA at the different ratio, and the MTZ was loaded into the hydrogels along with the gelatin processes. RESULTS: The highest drug entrapment efficiency (DEE) was exhibited by MTZ-H3 (5: 5) with DEE of 99.20% and a gel fraction of 97.52%. FTIR results revealed that Schiff base reaction was occurred by the absorption peak of -C = N- groups at 1628 cm-1 and indicated that there is insignificant alteration at different ratio of MCS and OSA. The best sustained of in vitro release profiles of MTZ was shown by MTZ-H3, which is 74.92% and 75.65% at pH 1.2 and 7.4 for 12 h of release, respectively. CONCLUSION: The optimised ratio between MCS and OSA to prepare in situ cross-linked hydrogels were found to be 5:5 according to the results of DEE and in vitro drug release profiles of MTZ and the MTZ loaded MCS-OSA hydrogels have a great potential which can be applied in biomedical applications.