Design of poly(ethylene glycol) immobilizing platinum complex through chelate-type coordination bond

Platinum-based chemotherapy: trends in organic nanodelivery systems

Despite the investment in platinum drugs research, cisplatin, carboplatin and oxaliplatin are still the only Pt-based compounds used as first line treatments for several cancers, with a few other compounds being approved for administration in some Asian countries. However, due to the severe and worldwide impact of oncological diseases, there is an urge for improved chemotherapeutic approaches. Furthermore, the pharmaceutical application of platinum complexes is hindered by their inherent toxicity and acquired resistance. Nanodelivery systems rose as a key strategy to overcome these challenges, with recognized versatility and ability towards improving the safety, bioavailability and efficacy of the available drugs. Among the known nanocarriers, organic systems have been widely applied, taking advantage of their potential as drug vehicles. Researchers have mainly focused on the development of lipidic and polymeric carriers, including supramolecular structures, with an overall improvement of encapsulated platinum complexes. Herein, an overview of recent trends and strategies is presented, with the main focus on the encapsulation of platinum compounds into organic nanocarriers, showcasing the evolution in the design and development of these promising systems. This comprehensive review highlights formulation methods as well as characterization procedures, providing insights that may be helpful for the development of novel platinum nanocarriers aiming at future pharmaceutical applications.

Synthetic polymers as drug-delivery vehicles in medicine

Cancerous diseases present a formidable health problem worldwide. While the chemotherapy of cancer, in conjunction with other treatment modalities, has reached a significant level of maturity, efficacious use of such agents is still restricted by numerous pharmacological deficiencies, such as poor water solubility, short serum circulation lifetimes, and low bioavailability resulting from lack of affinity to cancer tissue and inadequate mechanisms of cell entry. More critically still, most drugs suffer from toxic side effects and a risk of drug resistance. The class of platinum anticancer drugs, although outstandingly potent, is particularly notorious in that respect. Among the countless methods developed in recent years in an effort to overcome these deficiencies, the technology of polymer-drug conjugation stands out as a particularly advanced treatment modality. The strategy involves the bioreversible binding, conjugating, of a medicinal agent to a water-soluble macromolecular carrier. Following pharmacokinetic pathways distinctly different from those of the common, nonpolymeric drugs, the conjugate so obtained will act as a prodrug providing safe transport of the bioactive agent to and into the affected, that is, cancerous cell for its ultimate cell-killing activity. The present treatise will acquaint us with the pharmacological fundamentals of this drug delivery approach, applied here specifically to the metalorganic platinum-type drug systems and the organometallic ferrocene drug model. We will see just how this technology leads to conjugates distinctly superior in antiproliferative activity to cisplatin, a clinically used antitumor agent used here as a standard. Polymer-drug conjugation involving metal-based and other medicinal agents has unquestionably matured to a practical tool to the pharmaceutical scientist, and all indications point to an illustrious career for this nascent drug delivery approach in the fight against cancer and other human maladies.

Poly(amidoamine) dendrimer-supported organoplatinum antitumour agents

While numerous water-soluble biocompatible polymers have been utilized for the construction of drug conjugates that offer significant advantages for drug delivery, poly(amidoamine) (PAMAM) dendrimers are superior in many ways for this purpose. They display nanoscale size, uniform shape, excellent water solubility, low toxicity and high surface functionality. In an attempt to circumvent the toxic side effects associated with the administration of organoplatinum drugs, a polymeric prodrug has been prepared from the treatment of a generation 4.5 PAMAM dendrimer with diaquo(1,2-diaminocyclohexane)platinum(II). A well-defined dendrimer–platinum conjugate containing 40 (1,2-diaminocyclohexane)platinum(II) units coordinated to the dendrimer surface via carboxylate groups is formed. This adduct is well behaved, water soluble, contains a high loading of platinum moieties and displays sustained release of active platinum species over a 24 h period under physiological conditions.

Separation of polyethylene glycols and their fluorescein-labeled compounds depending on the hydrophobic interaction by high-performance liquid chromatography

The separation and characterization of fluorescein-labeled polyethylene glycols (PEG) is described. Firstly, the polyethylene glycols labeled with fluorescein isothiocyanate (FITC) were synthesized and separated using Sephadextrade mark LH-20 medium by a step gradient. Secondly, a TSK GEL G4000 PW XL column was developed for determining the FITC derivatives of PEG. The retention mechanism is based on the hydrophobic interaction between the FITC derivatives of PEG and the packing material of the TSK GEL G4000PW XL column. The retention time of the PEG compounds increased by adding of salts in the mobile phase and decreased by adding of organic modifier. In addition, various salts in the eluent can also change the chromatographic behavior of these compounds. Finally, the pH of the mobile phase can have an impact on the retention time of the PEG compounds.

Synthesis and cytotoxic activity of platinum complex immobilized by branched polyethylene glycol

Two-arm branched mPEG (monomethoxy-polyethylene glycol) with different molecular weights (M(n)=4000, 6000, 9400) was synthesized and used as carrier for immobilization of cisplatin [cis-diammine(dichloro)platinum (II), CDDP]. As a contrast, CDDP modified with linear mPEGs was also synthesized. All these polymeric drugs modified with branched mPEG are water soluble and show higher cytotoxic activity against C6 human breast cancer cells than cisplatin modified with linear mPEG with the same molecular weight. All the polymeric CDDP showed a much lower toxicity than the CDDP.