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Metals and metal complexes are promising antimicrobials due to their powerful inhibitory activity against microbes. However, the potential for metal toxicity to life remains unsolved. Mercury is a toxic element with no known positive biological functions, and its toxicity to humans is well known. With the known toxicity of Hg and its complexes, their usefulness for antimicrobial therapy should not be neglected. In this work, we investigated the antimicrobial activity of bis-(alkynyl)mercury(II) complexes with oligothiophene and bithiazole linking units against MRSA and C. albicans (pathogens commonly co-inhabit infected sites), and their cytotoxicity was tested on NIH 3T3 cells. Among the Hg(II) complexes, complex 2 showed potent microcidal activity against MRSA (MIC and MBC values = 0.2 μg mL−1) and C. albicans (MIC and MBC values = 0.4 μg mL−1). Complex 2 displayed a highly distinguished zone of clearance with comparably sharp zone edges on microbial agar plates. Time–kill kinetic studies showed that MRSA colonies were reduced by approximately 5 logs during the initial 3 h exposure to complex 2 at an 8× MIC level. The possible antimicrobial mechanism might be due to the intracellular ROS generation by complex 2 that caused the loss in MRSA viability. Complex 2 exhibited a higher IC50 value (0.8 μg mL−1) towards NIH 3T3 cells that was greater than its corresponding MIC values against tested microbes. Hg(II) complexes would be potent antimicrobials, but a challenge is to fully utilize their potential inhibitory effects on microbes while lowering their toxic levels on human health.

Otomycosis is a superficial infection of the ear caused by fungi. The disease may occur in the pinna, external auditory canal and tympanic membrane of humans and animals. Aspergillus niger and Candida albicans are the most prevalent fungal species responsible for otomycosis. In our study, the potential antifungal properties of a series of Schiff bases was examined. The synthesized compounds (1–14) were investigated for their minimum inhibitory concentration, minimum fungicidal concentration and zone of clearance against Aspergillus niger and Candida albicans. Compounds 5 and 6 with alkyl chain containing 6 or 7 carbon atoms exhibited an obvious fungicidal activity with the MIC/MFC ratio of 2. Zone of clearance study also demonstrated that both compounds 5 and 6 produced noticeable clear zones against the tested fungi as compared to fluconazole. The time-kill kinetic study showed that Candida albicans colonies were reduced by more than 3 logs after 24 h exposure to compound 5 at 4 and 8 × MIC levels. Both compounds 5 and 6 at a concentration of 50 μg mL−1 exhibited satisfactory cell viability towards human skin keratinocytes. Our results suggest that these compounds may be considered as potential drug candidates for the treatment of Aspergillus niger and Candida albicans ear infections.

A series of ruthenium(II) bis(2,2'-bipyridyl) complexes containing N-phenyl-substituted diazafluorenes (Ru-C1, Ru-C6, Ru-C7 and Ru-F) was synthesized and their potential antibacterial activity against methicillin resistant Staphylococcus aureus (MRSA) was investigated. The Ru-C7 complex showed significant improvement in both minimum inhibitory concentration (MIC, 6.25 μg mL(-1)) and minimum bactericidal concentration (MBC, 25 μg mL(-1)) towards MRSA when compared with those of methicillin (positive control) (MIC = 25 μg mL(-1) and MBC = 100 μg mL(-1)). The Ru-C7 complex possessed much stronger antibacterial effects than the Ru-C6 complex (MIC, 25 μg mL(-1), MBC, >100 μg mL(-1)). Both Ru-C6 and Ru-C7 complexes were also demonstrated to be biologically safe when tested on normal human skin keratinocytes.

The safety issues of biomedical applications have been a major concern in recent years. Drug delivery associated with microencapsulation technology has been focused on as microencapsulated drugs are believed to promote comparative therapeutic efficiency on human absorption and prolong the life cycle of drugs. The most commonly applied crosslinker is formaldehyde in a gelatin microencapsulation system, which is considerably toxic to the human body. To reduce the risks involved when using formaldehyde, agar was associated with gelatin as the wall matrix materials of microcapsules as it could crosslink with gelatin to give a gel network in the microcapsules formation. Here we report the development, characterization and safe use of agar–gelatin microcapsules. We further demonstrate that both oral and topical applications are possible using the berberine HCl and gallic acid loaded microcapsules respectively. Microcapsules containing both drugs were prepared combining the optimal parameters identified. The mean drug loading efficiency and the mean particle sizes of the berberine HCl loaded microcapsules were 78.16% and 16.75 μm respectively, while those of gallic acid loaded microcapsules were 70.28% and 21.98 μm respectively. The compositions and surface morphology of berberine HCl and gallic acid containing microcapsules were examined using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The in vitro controlled release models demonstrated that the drugs could be gradually released from the microcapsules. The minimum inhibitory concentrations (MICs) and anti-Staphylococcus aureus activity also proved that the berberine HCl loaded microcapsules exhibited better antibacterial activity towards Staphylococcus aureus when compared with those of the original drugs. The in vitro drug delivery model also demonstrated the delivery of berberine HCl from microcapsule treated textiles into nude mice skin. The in vivo mice disease model also showed that gallic acid loaded microcapsules were helpful in the treatment of acute liver and kidney toxicity after an overdose administration of acetaminophen. The development of agar–gelatin microcapsules was demonstrated to be an efficient, deliverable tool for both oral and topical applications.

In connection to our previously reported phosphine compounds as antitumor agents, this article describes the preparation of ferrocenyl amino-phosphine and their possible cytotoxic potential towards the human hepatocellular carcinoma cell line Hep3B. The preliminary results suggested that ferrocenyl amino-phosphines can be potential anti-tumour agents which might be considered as novel cancer chemotherapeutic agents. In particular, compounds 4b, 4d and 4f exhibit strong cytotoxicity with IC50 < 5 μg ml−1. These compounds possess more promising cytotoxic activities than their precursor non-substituted ferrocene as well as the reference metallodrug cisplatin.