Small molecule drugs can be bound to plasma proteins. Examples are Apixaban (459 Da, 87% protein bound), Carvedilol (406 Da, 98% protein bound) or Calcitriol (416 Da, 99.9 % protein bound). In ...plasma, these drugs have a free and a protein bound fraction. Protein binding impacts the removal behavior of the drug during dialysis. The purpose of this work was to develop a quantitative model to describe the removal of these solutes, and validate the model experimentally. A mathematical model was developed by coupling the equations of transport in dialyzers reported in one of our previous studies, and mass balance equations reported in literature to include the effect of binding. Simulated HD treatments with human plasma were performed with 3 different types of commercial dialyzers having different membrane permeability to study the removal of Apixaban, Carvedilol or Calcitriol, expressed in terms of solute clearance. Additionally, the loss of albumin was quantified. Experimental clearance results ml/min are given as mean ± MAD from 3 independent experiments in the order of Apixaban / Carvedilol / Calcitriol. Calculated values are reported in brackets. Dialyzer 1 was tested in HDF mode, yielding clearance of 60 ± 1.0 61 / 41 ± 1.8 10/ < 6 0.5. Dialyzer 2 tested in HD mode yielded clearance of 60 ± 1.6 60 / 31 ± 1.6 10 / <6 0.5. Dialyzer 3 tested in HD mode yielded clearance of 61 ± 0.5 61 / 34 ± 3.8 10 / <6 0.5. Clearance of tested drugs was lower than expected for their nominal molecular weight. The levels scaled Apixaban > Carvedilol >> Calcitriol, which is inverse to their degree of protein binding (Apixaban < Carvedilol << Calcitriol). The degree of protein binding was revealed to be the actual critical determinant, rather than dialyzer design and operational mode. Drug clearance seemed to be driven by the proportion of the free fractions, as is reflected in the model by the increase of clearance for decreasing bound fraction.
This work is about gas biosensing with a cytochrome c biosensor. Emphasis is put on the analysis of the sensing process and a mathematical model to make predictions about the biosensor response. ...Reliable predictions about biosensor responses can provide valuable information and facilitate biosensor development, particularly at an early development stage. The sensing process comprises several individual steps, such as phase partition equilibrium, intermediate reactions, mass-transport, and reaction kinetics, which take place in and between the gas and liquid phases. A quantitative description of each step was worked out and finally combined into a mathematical model. The applicability of the model was demonstrated for a particular example of methanethiol gas detection by a cytochrome c biosensor. The model allowed us to predict the optical readout response of the biosensor from tabulated data and data obtained in simple liquid phase experiments. The prediction was experimentally verified with a planar three-electrode electro-optical cytochrome c biosensor in contact with methanethiol gas in a gas tight spectroelectrochemical measurement cell.
Introduction
The mortality risk of dialysis patients is still elevated. Even though there is continuous improvement in the biocompatibility of dialysis devices and treatments, there is clinical ...evidence of a negative inflammatory impact. One dialysis-related risk factor to be considered in this regard may be the repeated blood exposure to foreign filter surfaces. Standard test methods do not allow differences to be shown between most of the common dialysis devices.
Methods
A new highly sensitive in vitro test system was developed by analyzing the response of leukocytes to surface contact in dialysis filter devices by means of quantitative real time PCR and flow cytometry. Membrane surface studies provided additional physical data.
Results
An increase in the transcription level of specific pro-inflammatory genes, particularly IL-1β, TNF alpha, and IL-8, was observed after blood contact to the filter devices. In two sets of pairwise filter comparisons, radiation-sterilized filters showed stronger cell activation, more hydrophilic membranes, and rougher surfaces.
Conclusions
Quantitative real time RT-PCR was shown to be a new in vitro test method with increased sensitivity for detecting differences in activation levels of leukocytes upon membrane contact. Correlating leukocyte activation levels with surface properties opens new opportunities for understanding leukocyte activation upon membrane contact and thus guides further improvements in the biocompatibility of dialysis filter devices.
Objectives: Objective of this work is to provide a new and more sensitive method based on RT-qPCR (quantitative polymerase chain reaction) for biocompatibility testing in order to facilitate further ...improvements of dialysis filter devices. Need for improved biocompatibility is given by the clinical observation that dialysis patients have increased risk of cardiovascular disease that is suspected to be influenced by the foreign surface contact. Although there exist a couple of methods to measure biocompatibility, these methods are not sensitive enough to differentiate biocompatibility of modern filter devices and consequently these methods are not suited to guide future developments. Methods: The method is a two-step in vitro process. The first part is the exposure of human blood in parallel to two dialysis filter devices. The second part is the quantitative analysis of the activation level of the leukocyte cell population. The activation level is quantified by the amount of mRNA of a specified set of inflammatory markers by real-time quantitative PCR. Additional information is obtained by FACS analysis of surface marker proteins. Results: RT-qPCR analysis of inflammatory markers in human blood showed that exposure of blood to different filter devices resulted in different leukocyte activation levels. Particularly early inflammatory markers like TNF- alpha and IL-1 beta revealed statistically significant differences between filter devices. Though physical and chemical analysis of the filter materials showed differences in filter materials, no single parameter could be correlated to increased leukocyte activation. Conclusions: A new method based on RT-qPCR could be established for biocompatibility testing of modern dialysis filter devices. The method allows in vitro characterization of inflammatory processes that are caused by foreign surface contact and are suspected to be clinically relevant for cardiovascular complications. Moreover, the method showed differences in leukocyte activation between commercial dialysis filters and is therefore suited to guide further improvements in biocompatibility.
Microarray technology is increasingly used for a miniaturised and parallel measurement of binding constants. In microarray experiments heterogeneous functionalization of surfaces with capture ...molecules is a problem commonly encountered. For multivalent ligands, especially, however, binding is strongly affected by receptor density. Here we show that high-resolution imaging of microarrays followed by image segmentation and separate analysis of bright and dark parts provides valuable information about ligand binding. Binding titrations were conducted with monovalent and bivalent fluorescent ligand peptides for the model receptor vancomycin. Microarrays were scanned with a confocal microscope and inhomogeneous spots were evaluated either as a whole or after segmentation into bright and dark areas. Whereas the binding constant for the monovalent ligand was hardly affected by spot heterogeneity, for the bivalent ligand affinity was higher for the parts of the spots with a greater density of receptors. This information was lost if the spots were analysed as a whole. These results reveal that imaging resolution may be a key factor in miniaturised binding assays, emphasising the importance of high-resolution images and image segmentation for new techniques, for example SPR imaging.
The comparative analsis of the effectiveness of surgical interventions performed by the standard method and using electric welding technology in endocrine surgery was hold. Compared duration of ...surgery, amount of intraoperatve blood loss, frequency of intra- and early postoperative complications. Found that the use of weding technology ensures shorter duration of surgery, on average by 30%, amount of blood loss--by 20-50%, the frequency of intra- and early postoperative complications.
The experience of a method of electric welding of biological tissues in laparoscopic surgery is submitted. 1494 operations with use of electrowelding procedure were conducted (cholecystectomy - 1434 ...(95.9%), echinococcectomy - 32 (2.1%), pericystectomy of echinococcosis cyst - 19 (1.27%), regional resection of a liver with a cyst - 1 (0.06%), enucleation of a hemangioma - 5 (0.33%). On the estrablishment of the received results it is possible to make a conclusion, that procedure of electric welding of biological tissues is a reliable, simple method of a hemostasis and tissue bonding method in laparoscopic surgery.
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