RESUMEN
Hydrophobic uremic toxins accumulate in patients with chronic kidney disease, contributing to a highly increased cardiovascular risk. The clearance of these uremic toxins using current hemodialysis techniques is limited due to their hydrophobicity and their high binding affinity to plasma proteins. Adsorber techniques may be an appropriate alternative to increase hydrophobic uremic toxin removal. We developed an extracorporeal, whole-blood bifunctional adsorber particle consisting of a porous, activated charcoal core with a hydrophilic polyvinylpyrrolidone surface coating. The adsorption capacity was quantified using analytical chromatography after perfusion of the particles with an albumin solution or blood, each containing mixtures of hydrophobic uremic toxins. A time-dependent increase in hydrophobic uremic toxin adsorption was depicted and all toxins showed a high binding affinity to the adsorber particles. Further, the particle showed a sufficient hemocompatibility without significant effects on complement component 5a, thrombin-antithrombin III complex, or thrombocyte concentration in blood in vitro, although leukocyte counts were slightly reduced. In conclusion, the bifunctional adsorber particle with cross-linked polyvinylpyrrolidone coating showed a high adsorption capacity without adverse effects on hemocompatibility in vitro. Thus, it may be an interesting candidate for further in vivo studies with the aim to increase the efficiency of conventional dialysis techniques.
Asunto(s)
Carbón Orgánico/química , Cresoles/química , Indicán/química , Fenilacetatos/química , Povidona/química , Insuficiencia Renal/sangre , Ésteres del Ácido Sulfúrico/química , Uremia , Adsorción , Recuento de Células Sanguíneas , Humanos , Diálisis RenalRESUMEN
A new approach for on-line SEC-NMR is introduced. The method combines time slicing, fractionation with adjusted loop collection and automatic stop-flow NMR analysis. It will be called on-line fractionated SEC-NMR. This technique allows the precise determination of molar mass distributions for any polymer which can be detected by NMR. It is a significant improvement of sensitivity and accuracy compared to onflow SEC-NMR and exhibits a much easier experimental setup than off-line SEC-NMR fractionation. The new method was applied to protonated and deuterated block copolymers by using ¹H NMR and for the first time also ²H NMR detection. In this case block copolymers can be correctly characterized according to their block length distributions. As the consequence very precise molar mass parameters M(n) and M(w) can be determined. The results of the on-line fractionated SEC-NMR are in very good agreement with the multi detector analysis. The new technique also proposes a method for separating the true copolymer and low molar mass fractions in the mixture, whose structures are confirmed by HPLC-FTIR and 2D chromatography.
Asunto(s)
Cromatografía en Gel/métodos , Espectroscopía de Resonancia Magnética/métodos , Polimetil Metacrilato/química , Poliestirenos/química , Cromatografía Líquida de Alta Presión , Deuterio/química , Hidrógeno/químicaRESUMEN
A general approach of size exclusion chromatography (SEC)-NMR is introduced for the determination of the classical molar mass parameters M(W), M(N), and M(P). It can be used for the determination of molar mass distributions of homopolymers and copolymers. The main advantage of SEC-NMR of copolymers is the possibility of detecting each monomer unit simultaneously with NMR as a quantitative concentration detector. Therefore, it is possible to provide the chemical compositions of copolymers at any elution volume without calibrations. In this respect, a new method will be presented for getting correct signal quantities of onflow data with sufficient NMR sensitivities. As the consequence, the chemical composition of copolymers can be correctly quantified under typical chromatographic conditions with respect to sample concentration and flow rate. Finally, the molar mass calibrations of the copolymers can be easily adjusted according to their chemical compositions. The methods were applied to polystyrene-b-poly(methyl methacrylate) block copolymers of different molar masses. The results of the molar mass distributions and the chemical composition distributions obtained by SEC-NMR are in very good agreement with the complex SEC multidetector analysis.