Drug-Eluting Stents and Balloons-Materials, Structure Designs, and Coating Techniques: A Review.

Controlled drug delivery is a matter of interest to numerous scientists from various domains, as well as an essential issue for society as a whole. In the treatment of many diseases, it is crucial to control the dosing of a drug for a long time and thus maintain its optimal concentration in the tissue. Heart diseases are particularly important in this aspect. One such disease is an obstructive arterial disease affecting millions of people around the world. In recent years, stents and balloon catheters have reached a significant position in the treatment of this condition. Balloon catheters are also successfully used to manage tear ducts, paranasal sinuses, or salivary glands disorders. Modern technology is continually striving to improve the results of previous generations of stents and balloon catheters by refining their design, structure, and constituent materials. These advances result in the development of both successive models of drug-eluting stents (DES) and drug-eluting balloons (DEB). This paper presents milestones in the development of DES and DEB, which are a significant option in the treatment of coronary artery diseases. This report reviews the works related to achievements in construction designs and materials, as well as preparation technologies, of DES and DEB. Special attention was paid to the polymeric biodegradable materials used in the production of the above-mentioned devices. Information was also collected on the various methods of producing drug release coatings and their effectiveness in releasing the active substance.

Retention indices and quantum-chemical descriptors of aromatic compounds on stationary phases with chemically bonded copper complexes.

In this paper, Kováts retention indices determined on stationary phases with chemically bonded copper complexes were correlated with molecular structural parameters for aromatic compounds. Principal component regression (PCR) was applied to extract principal components from the set of 13 descriptors compiled in 5 theoretical models. Extracted components were used to model theoretical retention indices. Significant correlations were found among the retention indices of these compounds and, among others: molecular surface and molecule area, boiling point, HOMO and LUMO energies, dipole moment, dielectric energy, and double bond count. These correlations provide insights into the mechanism of chromatographic retention at the molecular level for the packings and the compounds under study.

Recent advances in gas chromatography for solid and liquid stationary phases containing metal ions.

This review is devoted to the application of metal complexes as column packings and liquid stationary phases in gas chromatography. Particular attention is paid to the stationary phases with nitrogen-containing functional groups (e.g., amine and ketoimine) and beta-diketonates on the modified silica surface. The review also concerns the results of the research on metallomesogenes and chiral stationary phases. The factors influencing the retention mechanism in complexation gas chromatography are discussed. Practical application of the metal chelate-containing chromatographic packings for analytical separation of organic substances is considered.

Chemically Bonded Phases for the Analysis of Trace Amounts of Organic Pollutants.

This work describes some results of identification and determination of bisphenol A (BPA) in powdered milk by applying the gas chromatography. To determine BPA contents in the milk and to reduce the matrix interference associated with the constituents of the powdered milk, we performed the following activities. First, we ultra-centrifuged the dissolved milk solutions. Next, we preconcentrated the analyte in the supernatant using a C(18) and new sorbent with chemically bonded ketoimine group solid phase extraction column. Finally, we used gas chromatography for the determination of BPA in the samples under study. A recovery of bisphenol A from spiked milk samples was also performed, with recovery result located at 91% +/- 3%/94% +/- 2%.

Ketoimino groups as silica surface modifiers.

The presented work is devoted to Porasil C silica, with organic compounds bonded to its surface and capable of electron-donor-acceptor (EDA) interactions. These packings are a good base for studying interactions among stationary phases and the adsorbate molecules showing electron-donor properties. The presented work concentrates on the phases containing ketoimino groups at their surface. Copper and chromium chlorides were bonded through these to the surface. Physicochemical characteristics of the obtained packings were determined by the use of elemental analysis, differential scanning calorimetry (DSC) and inverse gas chromatography. We examined the influence of the surface modification on the retention parameters of the nucleophilic compounds.

Comparative studies of gas chromatographic properties of new packings with chemically bonded complexes.

Specific interactions of aliphatic linear and branched hydrocarbons as well as cyclic and aromatic hydrocarbons with new packings containing chemically bonded complexes of transition metals are studied. The possibility of using these packings to separate these compounds is also discussed. The packings under study contain complexes of Cu(II) and Cr(III) chemically bonded to the silica surface. Chlorides of these metals are bonded to the silica surface by the use of the ketoimine group originally from 2-(3-triethoxysililpropylimino)-3-(n-buthyl)-pentanon-4. In order to determine an influence of the performed modification to gas chromatographic properties of the packings, such retention parameters as retention factor, retention index, molecular retention index, and specific retention volume are measured for these compounds. Based on the obtained values, a trial is taken to determine an influence of the nature of the bonded metal from the complex on the retention of the adsorbates under study and a dependence between a structure of an adsorbate molecule and values of charge-transfer interactions with the bonded metal complexes.