Platinum Complexes with the Novel Ligand Diethyl [(Methylsulfinyl)-methyl]phosphonate (SMP): Solid-State Characterization of Potassium Trichloro(SMP)platinum(II) which, in Solution, Gives Dichloro(SMP)-platinum(II) and Potassium Chloride

Surface hybrid self-assembly, mechanism, and crystalline behavior of a carboxyl-ended hyperbranched polyester/platinum complex

The self-assembly of hyperbranched polymers has attracted much attention because of their wide application. In this article, we report a new facile surface self-assembly method for a carboxyl-ended hyperbranched polyester/platinum complex (HTD-3-Pt) and obtain ordered structural microrods with a length of 10-20 μm and a width of 1 μm. The length and diameter of the self-assembled microrods could be increased to 300-600 μm and 4-5 μm, respectively, by hierarchical self-assembly. The main factors affecting the morphology of the self-assemblies, including temperature, time, solvent and solubility parameter, and relative humidity were discussed by transmission/reflection polarizing optical microscopy (TRPOM), SEM, and HRSEM. The indications for the coordination bond (-COOPt) included the appearance of a new peak at 1606 cm(-1) and its shifting to 1634 cm(-1) in the FT-IR spectra, the disappearance of the C 1s peak at about 288.6 eV, and the increase in the O 1s electron binding energy in the XPS spectra. Furthermore, an interesting crystal property of the HTD-3-Pt self-assemblies was discovered and confirmed by XRD. The study results from the surface self-assembly mechanism suggest that the coordination induction of the platinum ion play a key role in driving microphase separation between the intermolecular chains and end groups of the HTD-3-Pt to form the microrod self-assemblies. Another interesting finding was that HTD-3-Pt showed a higher catalytic activity for hydrosilylation than did a traditional homogeneous catalyst.

Silica xerogels and hydroxyapatite nanocrystals for the local delivery of platinum-bisphosphonate complexes in the treatment of bone tumors: a mini-review

The present review focuses on the "drug targeting and delivery" approach of the selective transportation of cisplatin to bone tumors and bone metastases. This aim is realized by binding cisplatin to (bis)phosphonate ligands or their derivatives. Geminal bisphosphonates are in clinical use in the treatment of several bone-related diseases because of their high affinity for calcium ions and hence for bones. Platinum-bisphosphonate complexes may be easily loaded onto calcium-containing inorganic matrices, such as calcium-doped sol-gel derived silica xerogels and hydroxyapatite nanocrystals, for local administration at the site of the bone malignancy. The composites may be used as bone-filler materials that, in addition to their action as bone substitutes, can also act as controlled platinum-drug releasing agents. The release kinetics of the drug can be tailored for specific therapeutic applications modulating the physico-chemical features of the inorganic matrices. Moreover, apatite nanocrystals loaded with platinum-bisphosphonate prodrugs can be used as injectable material for nanomedical applications (e.g. intracellular drug delivery).

Mechanistic insight into the inhibition of matrix metalloproteinases by platinum substrates

Platinum compounds are among the most used DNA-damaging anticancer drugs, however they can also be tailored to target biological substrates different from DNA, for instance enzymes involved in cancer progression. We recently reported that some platinum complexes with three labile ligands inhibit matrix metalloproteinase activity in a selective way. We have now extended the investigation to a series of platinum complexes having three chlorido or one chlorido and a dimethylmalonato leaving ligands. All compounds are strong inhibitors of MMP-3 by a noncompetitive mechanism, while platinum drugs in clinical use are not. Structural investigations reveal that the platinum substrate only loses two labile ligands, which are replaced by an imidazole nitrogen of His224 and a hydroxyl group, while it retains one chlorido ligand. A chlorido and a hydroxyl group are also present in the zinc complex inhibitor of carboxypeptidase A, whose active site has strong analogies with that of MMP-3.

Antitumour metal compounds: more than theme and variations

Triggered by the resounding success of cisplatin, the past decades have seen tremendous efforts to produce clinically beneficial analogues. The recent achievement of oxaliplatin for the treatment of colon cancer should, however, not belie the imbalance between a plethora of investigated complexes and a very small number of clinically approved platinum drugs. Strategies opening up new avenues are increasingly being sought using complexes of metals other than platinum such as ruthenium or gallium. Based on the chemical differences between these metals, the spectrum of molecular mechanisms of action and potential indications can be broadened substantially. Other approaches focus on complexes with tumour-targeting properties, thereby maximizing the impact on cancer cells and minimizing the problem of adverse side effects, and complexes with biologically active ligands.

Bisphosphonate complexation and calcium doping in silica xerogels as a combined strategy for local and controlled release of active platinum antitumor compounds

The production of bone substitute biomimetic materials which could also act as antitumoral drug release agents is of enormous interest. We report in this paper the synthesis and characterization of a novel platinum dinuclear complex containing a geminal bisphosphonate and its embodiment into xerogels prepared by the sol-gel method. Our goal was to obtain a hybrid inorganic matrix that could release a platinum species active against bone tumors or metastases, upon local implant. Two silica xerogels were considered: one was composed of pure silica, while the other contained also some calcium as potential release-modulating agent thanks to its high affinity for bisphophonates. The platinum-complex loading capacity of the inorganic matrices, the release kinetics in buffer simulating physiological conditions, and the stability upon storage were investigated as a function of Pt-complex concentration and calcium addition. We found that the presence of calcium in the composites deeply influences not only the stability of the formulations but also the nature of the platinum complex liberated in solution.