Experimental studies of contact angle hysteresis phenomena on polymer surfaces ­ Toward the understanding and control of wettability for different applications.

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications.

The use of PEG-Hirudin in chronic hemodialysis monitored by the Ecarin Clotting Time: influence on clotting of the extracorporeal system and hemostatic parameters.

AIM: The aim of our study was to investigate the use of polyethylene glycol (PEG)-Hirudin (PEG-H) as an anticoagulant in hemodialysis including drug monitoring with the Ecarin Clotting Time (ECT) in whole blood and to compare this regimen with standard anticoagulant unfractionated heparin (UFH) for influence on hemostatic parameters and clot frequency of the extracorporeal system. PATIENTS AND METHODS: The application of PEG-H as an anticoagulant in patients on chronic HD was studied in 20 patients (12 males, 8 females) from a single center in an exploratory, open-label, controlled, single-blind, dose-finding study. The patients were divided in 2 groups with 10 patients each (Group I and II); both received 3 dialyses with UFH, thereafter Group I received 5 dialyses with PEG-H and Group II 10 dialyses with PEG-H. Starting dose of PEG-H in the first dialysis was a bolus of 0.08 mg/kg bwt, the mean dose of the following HD was 0.041 mg/kg bwt (range 0.026 0.065 mg/kg bwt). PEG-H was applied as an intravenous bolus-dose followed by a 0.9% saline as a placebo-infusion. HD was performed regularly 3 times a week. All dialysis treatments were performed exclusively with a hollow fiber dialyzer type. Fibrinogen, antithrombin III, prothrombin fragments, thrombin-antithrombin and soluble fibrin were measured with commercial tests. ECT was determined in a mechanical coagulometer. A semiquantitative score was given for the presence of clots in the extracorporeal system after each dialysis. RESULTS: PEG-H was effectively used as an anticoagulant in 150 chronic dialysis treatments using ECT as a simple monitoring method. The optimal whole blood concentration for PEG-H is 600-1000 ng/ml. Clotting in the whole extracorporeal system was decreased by 45% (p = 0.059) with PEG-H anticoagulated HD in comparison to UFH. Fibrinogen, prothrombin fragments (F1+2-fragments) and thrombin-antithrombin-complex showed no significant change in comparison with UFH, antithrombin III (AT III) increased to normal concentrations. Highly sensitive coagulation markers such as a soluble fibrin showed a significant decrease (p < 0.001) before and after HD with PEG-H compared with UFH. CONCLUSION: PEG-H can be used effectively as an alternative anticoagulant in patients on chronic HD using ECT as a simple drug monitoring method. The lower frequency of clots in the extracorporeal system, the stronger and more efficient inhibition of coagulation during HD as indicated by soluble fibrin, may have a positive influence on the disturbed blood coagulation of these patients.

[Follow-up in kidney transplantation. Which complications are likely?]. / Nach der Nierentransplantation. Mit welchen Komplikationen müssen Sie rechnen?

Kidney transplantations are being performed in every increasing numbers, and, in addition to specialist centres, nephrologists, general practitioners and urologists are more frequently being involved in the provision of aftercare. The major urological complications seen after transplantation include ureteral stenosis and necrosis, incontinence and impotence, lymphoceles, arterial stenosis, infections of the urinary tract and adnexa, as well as--the most serious complication--malignant tumours. In addition, the immunosuppression required by these patients is often associated with secondary disorders such as hypertension, steroid-related diabetes, hyperlipidemia and infections. Against the background of progressive organic deficiency it is of particular importance to identify such complications and to treat them adequately, or to prevent them from occurring, thus ensuring the longest possible survival of transplant and patient and improved quality of life.

Pharmacodynamics and pharmacokinetics of polyethylene glycol-hirudin in patients with chronic renal failure.

BACKGROUND: Hirudin selectively inhibits thrombin without cofactors and is eliminated via the kidneys. Recombinant hirudin (r-hi) has a terminal elimination half-life (t1/2) of about 50 to 100 minutes. Coupling of polyethylene glycol (PEG) to r-hi, giving PEG-hirudin (PEG-Hi), prolongs its t1/2 while enhancing efficacy. We looked at the pharmacodynamic and pharmacokinetic behavior of PEG-Hi in patients with impaired renal function. METHODS: Anticoagulant activity and the pharmacokinetic parameters of a single intravenous bolus injection of 0.05 mg/kg body weight PEG-Hi were studied in 38 subjects. They were assigned to five groups: group IA, creatinine clearance (CCr) >/= 80 mL/min, 8 healthy volunteers; group IB, CCr >/= 80 mL/min, 8 patients with normal renal function); group II, CCr 79 to 50 mL/min, 7 patients with mild chronic renal failure (CRF); group III, CCr 49 to 20 mL/min, 10 patients with moderate CRF; and group IV, CCr