Lattice-fluid model for gas-liquid chromatography.

Lattice-fluid models describe molecular ensembles in terms of the number of lattice sites occupied by molecular species (r-mers) and the interactions between neighboring molecules. The lattice-fluid model proposed by Sanchez and Lacombe (Macromolecules, 1978;11:1145-1156) was used to model specific retention volume data for a series of n-alkane solutes with n-alkane, polystyrene, and poly(dimethylsiloxane) stationary liquid phases. Theoretical equations were derived for the specific retention volume and also for the temperature dependence and limiting (high temperature) values for the specific retention volume. The model was used to predict retention volumes within 10% for the n-alkanes phases; 22% for polystyrene; and from 20 to 70% for PDMS using no adjustable parameters. The temperature derivative (enthalpy) could be calculated within 5% for all of the solutes in nine stationary liquid phases. The limiting value for the specific retention volume at high temperature (entropy controlled state) could be calculated within 10% for all of the systems. The limiting data also provided a new chromatographic method to measure the size parameter, r, for any chromatographic solute using characteristic and size parameters for the stationary phase only. The calculated size parameters of the solutes were consistent, i.e. independent of the stationary phase and agreed within experimental error with the size parameters previously reported from saturated vapor pressure, latent heat of vaporization or density data.

Nanoparticles: functionalization and multifunctional applications in biomedical sciences.

Rapid innovations in nanomedicine have increased the likelihood that engineered nanomaterials will eventually come in contact with humans and the environment. The advent of nanotechnology has created strong interest in many fields such as biomedical sciences and engineering field. Central to any significant advances in nanomaterial based applications will be the development of functionalized nanoparticles, which are believed to hold promise for use in fields such as pharmaceutical and biomedical sciences. Early clinical results have suggested that functionalization of nanoparticles with specific recognition chemical moieties indeed yields multifunctional nanoparticles with enhanced efficacy, while simultaneously reducing side effects, due to properties such as targeted localization in tumors and active cellular uptake. A prerequisite for advancing this area of research is the development of chemical methods to conjugate chemical moieties onto nanoparticles in a reliable manner. In recent years a variety of chemical methods have been developed to synthesize functionalized nanoparticles specifically for drug delivery, cancer therapy, diagnostics, tissue engineering and molecular biology, and the structure-function relationship of these functionalized nanoparticles has been extensively examined. With the growing understanding of methods to functionalize nanoparticles and the continued efforts of creative scientists to advance this technology, it is likely that functionalized nanoparticles will become an important tool in the above mentioned areas. Therefore, the aim of this review is to provide basic information on nanoparticles, describe previously developed methods to functionalize nanoparticles and discuss their potential applications in biomedical sciences. The information provided in this review is important in regards to the safe and widespread use of functionalized nanoparticles particularly in the biomedicine field.

Mass spectrometric inverse gas chromatography: investigation of polymeric phase transitions.

An improved inverse gas chromatographic method involving the use of a mass-specific detector for the determination of the glass transition temperature of polymeric materials is described. The new method allows the use of several probe solutes simultaneously with an automated, closed-loop injector and stepped temperature programming. The result is a single continuous chromatogram for each probe solute over a range of temperatures encompassing the glass transition temperature, T(g). Several different methods for the exact determination of T(g) from the chromatogram were investigated, including the classical van't Hoff-type plots with retention volumes calculated from both the peak maximum and first moment values of the elution peaks. Two new methods are also proposed for the evaluation of T(g) from either the temperature dependence of the second moments of the elution peaks for probe solutes or simple inspection of the variation of elution peak height (width) with temperature. All four methods for the determination of T(g) are evaluated with three probe solutes and four different polymers, viz., poly(methyl methacrylate), poly(ethylene terephthalate), polycarbonate, and two batches of polystyrene with different molecular weights and T(g) values. Three phenomenological models were used to interpret the chromatographic retention mechanisms of the solute probes in glassy and rubbery polymers. These are (i) the classical adsorption/absorption model for glass and rubber polymers, (ii) the single absorption mechanism model, and (iii) a dual-mode model previously used to explain the sorption of gases, such as CO(2), in glassy polymers. It is concluded that no single approach is adequate to interpret the experimental results for all of the systems, although each model is adequate for some individual solute/polymer combinations.

[Development of minocycline containing polycaprolactone film as a local drug delivery].

Local drug delivery by using biocompatible polymers has been developed in the treatment of periodontitis for many years. The purpose of this study was to examine the release kinetics of minocycline from monolithic film prepared from polycaprolactone and polyethylene glycol and to examine the antimicrobial activity in vitro. Polycaprolactone (Mwt 60,000), polyethylene glycol and minocyline was dissolved by chloroform, which was vigorously stirred for 24 hours and it was dried in vacuum chamber. The thickness of cast films containing 20%, 30% and 40% minocycline was 200 +/- 10 microns. Release rate of minocycline from the film was measured by means of a UV spectrophotometer. In vitro releasing test, each film showed a large burst effect within first two and three hours and a steady state release kinetic at the rate of 4-8 micrograms/cm/hour for 7 days. In antimicrobial test, each sample (one fourth inch in diameter) sunk in the broth that had been innoculated with periodontopathic bacteria showed growth inhibitory activity after 48 hr anaerobic incubation. In cytotoxicity test, there was no significant cytotoxic effect in casting film to human gingival fibroblast. This study showed that, by embedding minocycline in polycaprolactone, it is feasible to obtain substained release of the drug within the periodontal pocket for seven days and should be useful tool for elimination of pathogenic microflora from periodontal pocket or reducing inflammation in periodontal disease.