Copper complexes with bioactive ligands Part I--Antimicrobial activity

Dissolution of copper mineral phases in biological fluids and the controlled release of copper ions from mineralized alginate hydrogels

Here we investigate the dissolution behaviour of copper minerals contained within biocompatible alginate hydrogels. Copper has a number of biological effects and has most recently been evaluated as an alternative to expensive and controversial growth factors for applications in tissue engineering. Precise control and sustained release of copper ions are important due to a narrow therapeutic window of this potentially toxic ion, and alginate would appear to be a good material of choice for this purpose. We found that aqueously insoluble copper minerals could be precipitated during gelling within or mixed into alginate hydrogels in the form of microbeads prior to gelling to serve as depots of copper. These minerals were found to be soluble in a variety of biological fluids relevant to in vitro and in vivo investigations, and the alginate carrier served as a barrier to diffusion of these ions and therefore offered control over the rate and duration of release (Cu(2+) release rates observed between 10-750 µMol g(-1) h(-1) and duration for up to 32 d). Copper mineral and copper mineralized alginate microbeads were characterized using powder x-ray diffraction, FTIR, thermogravimetric analysis and scanning electron microscopy. Dissolution kinetics were studied based on measurements of copper ion concentrations using colourimetric methods. In addition we characterized the complexes formed between released copper ions and biological fluids by electron paramagnetic spectroscopy which offers an insight into the behaviour of these materials in the body.

Antimicrobial activity of ZnII, CdII, and HgII complexes of 1,2-bis-[2-(5-R)-1H-benzimidazolyl]-1,2-ethanediols and 1,4-bis-[2-(5-R)-1H-benzimidazolyl]-1,2,3,4-butanetetraols

1,2-Bis-[2-(5-H/Me/Cl/NO2)-1H-benzimidazolyl]-1,2-ethanediols (L1-L4), 1,4-bis-[2-(5-H/Me/Cl)-1H-benzimidazolyl]-1,2,3,4-butanetetraols (L5-L7) and their complexes with ZnCl2, CdCl2 and HgCl2 were synthesized and antibacterial activity of the compounds was tested toward Staphylococcus aureus, S. epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Proteus mirabilis and antifungal activity against Candida albicans. HgII complexes have a considerably higher antimicrobial activity against all microorganisms. Some HgII complexes show higher antifungal activity than clotrimazole toward C. albicans. Zn2(L3)Cl4, Zn2(L4)Cl4, and Cd(L3)Cl2 were moderately effective against S. aureus and S. epidermidis; Cd(L4)Cl2 exhibited a weak activity only against S. epidermidis.

Copper complexes with bioactive ligands. Part II--Antifungal activity

Antifungal activity of new copper(II) complexes of 2-methylthionicotinate (2-MeSNic) of the composition Cu(2-MeSNic)2(MeNia)(2).4H2O (where MeNia is N-methylnicotinamide), and Cu(2-MeSNic)2(Nia)(2).2H2O (where Nia is nicotinamide) and Cu(2-MeSNic)2L2 (where L is isonicotinamide, iNia, or ethyl nicotinate, EtNic) were tested on various strains of filamentous fungi by the macrodilution method. Most sensitive against copper(II) adducts with bioactive ligands were Rhizopus oryzae and Microsporum gypseum (IC50 1.5-2.3 mmol/L). The adducts with Nia, MeNia and EtNic at 5 mmol/L induced morphological changes in growing hyphae of Botrytis cinerea, mainly their intensive branching attached to release of cytoplasm with partial growth inhibition. Inhibition of sporulation (> 90%) of Alternaria alternata by Cu(2-MeSNic)2.H2O was observed as a change in the color of the colonies. The highest resistance was marked by B. cinerea and Fusarium moniliforme (average IC50 values 4.25 and 3.13 mmol/L, respectively). The presence of all bioactive ligands in copper(II) complexes caused an increase in the inhibition effect against model fungi (except significant inhibition activity of EtNic on R. oryzae).