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An improved carboxylation method of (OC‐6‐33)‐dichloro(ethane‐1,2‐diamine)dihydroxyplatinum(IV) based on succinic anhydride is reported. Reaction of the uncoordinated carboxylic acid with simple amines and alcohols leads to the corresponding amides and esters in the presence of 1,1′‐carbonyldiimidazole. The resulting new complexes are characterized by IR, 1H, 13C, 15N, and 195Pt NMR spectroscopy, mass spectrometry, and elemental analysis. This reaction provides an entry to a new class of kinetically inert platinum(IV) complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

We have developed a silver-releasing biomaterial with promising potential for wound healing applications. The material is made of ultrashort peptides which can self-assemble in water to form hydrogels. Silver nanoparticles (Ag NPs) were synthesized in situ within the biomaterial, using only UV irradiation and no additional chemical reducing agents. The synthetic strategy allows precise control of the nanoparticle size, with the network of peptide fibers preventing aggregation of Ag NPs. The biomaterial shows increased mechanical strength compared to the hydrogel control. We observed a sustained release of Ag NPs over a period of 14 days. This is a crucial prerequisite for effective anti-bacterial therapy. The ability to inhibit bacterial growth was tested using different bacterial strains, namely gram-negative Escherichia coli and Pseudomonas aeruginosa and gram-positive Staphylococcus aureus. Inhibition of bacterial growth was observed for all strains. The best results were obtained for Pseudomonas aeruginosa which is known for exhibiting multidrug resistance. Biocompatibility studies on HDFa cells, using Ag NP-containing hydrogels, did not show any significant influence on cell viability. We propose this silver-releasing hydrogel as an excellent biomaterial with great potential for applications in wound healing due to its low silver content, sustained silver nanoparticle release and biocompatibility.

Octahedrally configured diaminedichloro- and diamineoxalatoplatinum(IV) complexes with axial hydroxo ligands were carboxylated with succinic or glutaric anhydride. The free, uncoordinated carboxylic acid groups were further derivatized with amines and alcohols to the respective amides and esters and characterized in detail by elemental analysis, mass spectrometry, and multinuclear (1H, 13C, 15N, and 195Pt) NMR spectroscopy. Cytotoxicity of the complexes was studied in four human cancer cell lines derived from ovarian carcinoma (CH1, SK-OV-3), cervical carcinoma (HeLa), and colon carcinoma (SW480) by means of the MTT assay. Structure-activity relationships revealed a low activity for platinum complexes with underivatized carboxylic acid moieties and amide derivatives displaying the hydroxyethylamino residue. Within the series of amides, cyclopentylamino analogues were equipped with the highest cytotoxic potential. However, ester derivatives yielded IC50 values mostly in the low micromolar range and comparable to those of cisplatin. DNA platination studies of selected complexes revealed a high DNA platination capacity in parallel to a high cytotoxic potential and vice versa.

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