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The self-assembly of a series of bisthiourea containing amino acid side chains has been studied in a large range of organic solvents. Self-assembly is driven mainly by hydrogen bonding groups of thiourea and amino acids moieties. Of all the synthesized compounds, only bisthiourea with alanine side chains, 3.5 formed thermoreversible gel in 50:3 dichloromethane:water mixture at minimum gel concentration of 0.5%. SEM micrographs of the gel showed the formation of entangled cross-linked fibres. The addition of anions such as Cl¯, F¯ and AcO¯ disrupted the gel network of 3.5 thus inducing the gel-sol transition. To investigate the ability of the bisthiourea to form metallogel, metal ions such as Co2+, Cu2+, Ni2+ and Pb2+ were introduced, however, none of them induce the formation of metallogel. In particular, the gels show good performance in the absorption of bromocresol green and Eriochrome black-T at 75% and 61% efficiency, respectively within 24 hours. The good dye absorption properties of gel 3.5 render the potential of bisthiourea gels as new dye absorption materials, which show significant benefit for water pollution treatment.

The rise of antimicrobial resistance for infectious bacteria has become an alarming issue to human health. New antimicrobial drugs are in dire need and pivotal to overcome this issue. In this study, aspirinate azo ligands bearing different halogens L1-5 has been prepared via diazo-coupling reaction. The ligands L1-5 were coordinated with silver, Ag (I) metal to produce Ag (I) aspirin-azo complexes C1-5. The antibacterial properties of L1-5 and C1-5 were evaluated against Staphylococcus aureus and Escherichia coli using turbidimetric kinetic method. The complexes C1-5 showed comparable growth inhibition activity towards E. coli (MIC 82-105 ppm) and S. aureus (MIC 80-105 ppm) compared to ligands L1-5 with E. coli (MIC 83-200 ppm), S. aureus (80-131 ppm) and ampicillin (MIC 93 and 124 ppm, respectively). The excellent bacterial resistance of both L1-5 and C1-5 indicates the potential of aspirinate azo and their complexes as new antibacterial agents, which significantly benefit to the pharmaceutical industries.

The past 30 years have seen increasingly rapid advances in the field of tissue engineering. The advancement in the field of tissue engineering could address the drawback involved in the artificial organs and organ transplantation, as well as in the replacement of lost or severely damaged tissues. The major challenges faced in tissue engineering include vascularization, tissue architecture, and cell seeding. Hence, to address the challenges, biologically active scaffolds with ideal characteristics should be properly designed. In recent years, there has been an increasing interest in the use of hydrogel as biologically active scaffolds in tissue engineering. Recently, hyaluronic acid (HA) has been widely used as biomaterials for scaffold fabrication owing to their biofunctionality and multiple reactive functional groups. Pure HA has shown limitation in the gel properties; hence, structural modification on HA has been emphasized through various crosslinking reactions to afford hydrogel with optimum properties suitable for tissue engineering application. The biomaterials developed should be affordable for clinical use and must also satisfy marketing and regulatory requirements. Many HA-derived hydrogels have been reported to meet these criteria, thus widely used in tissue engineering. Hence, this chapter discusses the basic concepts and recent advances of HA-based hydrogels developed for tissue engineering application.