Search results for "permeation"

Molecular characterization of α,β-poly[( N -hydroxyethyl)- dl –aspartamide] by light scattering and viscometry studies

2000

Abstract α,β-poly[(N-hydroxyethyl)- dl -aspartamide] (PHEA) is a new synthetic polymer which is of interest in biomedical applications. In this paper, the molecular characterization of PHEA by multi-angle laser light scattering and viscometry off-line and on-line to a size exclusion chromatography system is reported. These techniques furnish an exhaustive and consistent characterization of the PHEA polymer. The fractionation of the PHEA macromolecules was relatively simple. Using an aqueous mobile phase of medium ionic strength, the elution was substantially regular and the macromolecules were not aggregate. The molar mass M of four PHEA samples approximately ranges from 46 to 53 K g/mol, t…

Main Chain Conformation and Anomalous Elution Behavior of Cylindrical Brushes As Revealed by GPC/MALLS, Light Scattering, and SFM

1999

High molar mass polymacromonomers based on methacryloyl end-functionalized oligo methacrylates (Mn = 2410 g/mol) adopt the conformation of wormlike cylindrical brushes. Comparison of the absolute molar mass, Mw, determined by static light scattering and the contour length, Lw, of the molecules measured by SFM in the dry state revealed the length per vinylic main chain monomer of the cylindrical structure to be less than 0.1 nm, thus being much shorter than the maximum value of 0.25 nm. In solution this shrinkage could be quantified to 0.071 nm per monomer by Holtzer analysis of the scattering curves which in addition yielded the Kuhn statistical segment length lk = 120 nm. GPC MALLS investi…

1995

About 340 g of a cycloaliphatic ionene (see formula given in the introduction) were fractionated by a continuous countercurrent extraction method (CPF). The efficiency of the separation was checked by viscometry and gel permeation chromatography (GPC). Ten different fractions with number average molecular masses between 16 000 and 29 000 D were obtained and their glass transition temperatures T g determined by differential scanning calorimetry (DSC) for their bromide and tetrafluoroborate salts. No molecular weight dependence of T g was found, in contrast to recently reported results with aliphatic ionenes, where - in case of the bromide - T g increases with rising molecular weight.

Diffusion of naltrexone across reconstituted human oral epithelium and histomorphological features

2006

Abstract In transbuccal absorption a major limitation could be the low permeability of the mucosa which implies low drug bioavailability. The ability of naltrexone hydrochloride (NLX) to penetrate a resembling histologically human buccal mucosa was assessed and the occurrence of any histomorphological changes observed. We used reconstituted human oral (RHO) non-keratinised epithelium as mucosal section and a Transwell diffusion cells system as bicompartmental model. Buccal permeation was expressed in terms of drug flux ( J s ) and permeability coefficients ( K p ). Data were collected using both artificial and natural human saliva. The main finding was that RHO does not restrain NLX permeat…

Release of naltrexone on buccal mucosa: Permeation studies, histological aspects and matrix system design

2007

Transbuccal drug delivery has got several well-known advantages especially with respect to peroral way. Since a major limitation in buccal drug delivery could be the low permeability of the epithelium, the aptitude of NLX to penetrate the mucosal barrier was assessed. Ex vivo permeation across porcine buccal mucosa 800 microm thick was investigated using Franz type diffusion cells and compared with in vitro data previously obtained by reconstituted human oral epithelium 100 microm thick. Both fluxes (Js) and permeability coefficients (K(p)) are in accordance, using either buffer solution simulating saliva or natural human saliva. Permeation was evaluated also in presence of chemical enhance…

Mechanical properties and water vapor permeability of starch/montmorillonite nanocomposites

2009

Results of an investigation into an unmodified-montmorillonite (MMT)-filled nanocomposite based on plasticized starch are reported. Data on the influence of MMT content on the tensile mechanical properties of the material are presented. Particular attention is given to the water vapor permeability of the nanocomposite. It is found that the resistance to water permeation of plasticized starch can be improved considerably by introducing a rather small amount of the filler into it. Data on the influence of MMT content on the coefficients of moisture diffusion, solubility, and permeability are reported. Also, a simple method for determining the effect of irregularly oriented platelike filler pa…

Photocleavable core cross-linked polymeric micelles of polypept(o)ides and ruthenium(II) complexes

2021

Core cross-linking of polymeric micelles has been demonstrated to contribute to enhanced stability that can improve the therapeutic efficacy. Photochemistry has the potential to provide spatial resolution and on-demand drug release. In this study, light-sensitive polypyridyl-ruthenium(II) complexes were combined with polypept(o)ides for photocleavable core cross-linked polymeric micelles. Block copolymers of polysarcosine-block-poly(glutamic acid) were synthesized by ring-opening N-carboxyanhydride polymerization and modified with aromatic nitrile-groups on the glutamic acid side chain. The modified copolymers self-assembled into micelles and were cross-linked by cis-diaquabis(2,2'-bipyridi…

Phenolic profiles of olive mill wastewaters treated by membrane filtration systems

2014

BACKGROUND Olive mill wastewater is an important by-product obtained after olive oil extraction. In this investigation, the phenolic composition of olive mill wastewater treated with a semi-industrial membrane filtration system, including ultrafiltration and reverse osmosis modules, was studied. In particular, untreated olive mill wastewater was compared with the permeate and the concentrate fractions of each filtration step. RESULTS 3,4-(dihydroxyphenyl) ethanol and p-(hydroxyphenyl) ethanol were the main compounds of all olive mill wastewater analyzed. A total of 32 compounds, detected at 240 or 280 nm by HPLC-DAD, were considered for phenol quantification. Ultrafiltration reduced phenol …

Molar masses and structure in solution of haemoglobin hyperpolymers--a common calibration of size exclusion chromatography of these artificial oxygen…

1997

We are developing artificial oxygen carriers for medical use, based on synthetic polymers--so-called hyperpolymers--obtained by cross-linking mammalian haemoglobins. One requirement with respect to the polymers is that they should not increase the oncotic pressure of blood remarkably--this can be realized by high molecular weights of the polymers with a narrow distribution. They may act as a oxygen transporting blood additive, and--in combination with a plasma expander--as a blood substitute. Another important and desired property of the artificial oxygen carrier is a low viscosity, which--first--is due to a high degree of uniformity of the polymer size (or molar mass) distribution and--sec…

Aroma transfers in and through plastic packagings: orange juice andd-limonene. A review. Part I: Orange juice aroma sorption

1997

Orange juice and one of its major volatile constituents, d-limonene, were probably amongst the first food products to be thoroughly studied. Yet, no extensive literature review has been undertaken in order to obtain a general and accurate description of the sorption and diffusion phenomena. This review underlines the effects of packaging on the organoleptic quality of citrus juices; it therefore presents a focused interest on d-limonene mass transfer experimental results with a variety of plastic polymers. Part I deals with first, loss of organoleptic quality of orange juice during storage and d-limonene sorption is discussed. Second, generalites are presented concerning volatiles transfer …