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A polyetherurethane (PU) was modified using fluorinated surface-modifying macromolecules (SMMs). A double radiolabel method was used simultaneously to measure the number of adhered platelets ((51)Cr) and the quantity of adsorbed Fg ((125)I), in a cone-and-plate instrument. The objectives were to determine if adsorbed Fg levels correlated to platelet adhesion on the surfaces, and to assess if any reductions in platelet adhesion for the SMM-treated surfaces resulted from surface-induced platelet lysis, rather than changes directly related to lower platelet activation and attachment on the novel surfaces. Platelet lysis was determined from lactate dehydrogenase (LDH) and unbound (51)Cr released into plasma isolated from whole blood exposed to test materials. The corresponding Fg adsorption, evaluated under the same platelet adhesion conditions, did not account for the reduced platelet adhesion on the treated surfaces. LDH and (51)Cr platelet release were very low and indicated no statistically significant differences between the materials. It was therefore concluded that platelet lysis did not contribute to the reduction in platelet adhesion characteristic observed on the SMM-treated surfaces. More importantly, the work emphasizes that the platelet activation cannot be inferred to by assessing the quantity of fibrinogen as is commonly done in the literature. The finding suggests a much more complex mechanism of action for the SMM surface modifiers. On-going work is investigating other Fg parameters such as protein binding affinity and protein conformational state in order to establish the mechanism by which the fluorinated surface modifiers may be reducing platelet adhesion via intermediary changes in initial protein adsorption.

Polyethersulfone (PES) has been recently adopted for membrane materials in applications such as ultrafiltration and haemodialysis. As a biomaterial, the factors which affect the blood compatibility of PES membranes include surface energetics, hydrophobicity, and surface morphology. Surface fluorination of materials has been found to create surfaces with improved blood compatibility and chemical stability. One novel approach to generating fluorinated polymer surfaces has included the use of fluorinated surface modifying macromolecules (SMMs). These macromolecules have been reported to establish fluorinated functional groups at surfaces of polymeric materials without significantly affecting the physical properties of the base polymer. However, to date there has been relatively little information published on the nature of the surface structure for PES materials containing these SMMs. In this study, synthesized SMMs with varying chemical compositions were characterized and blended with PES, and fabricated into flat sheet membranes. The bulk thermal transitions of PES materials were not significantly altered by the addition of 4 wt% SMMs. Contact angle data showed that the addition of SMMs in PES created more hydrophobic surfaces, accompanied by an increase in surface heterogeneity. X-ray photoelectron spectroscopy studies confirmed the presence of elemental fluorine at the surface. Through microscopy studies, it was shown that surface modification was achieved by the migration of SMM concentrated microdomains to the air-membrane interface. The generated microdomains (approximately 1-2 microm in diameter) are dispersed within the top 8 microm of the surface. The concentration of microdomains was gradually depleted from the surface to the bulk of the membrane. A schematic of the morphology for SMMs within the PES membrane surface was proposed.

with infection. A composite risk score was created using retained factors in stepwise multivariable logistic regression modeling.RESULTS: A cohort of 74 patients was identified with obstructive urolithiasis evaluated for decompression due to concern for UTI of whom only 37 (50%) had a true UTI. The standard model of serum WBC > 15 or temperature > 38 C had an AUC of only 0.68 to predict true UTI. Conversely, a data-derived 5-point risk score (1-point for each of the following: positive gram stain, >50 WBCs/hpf on urine microscopy, perinephric fat stranding on CT, serum C-reactive protein (CRP) > 21.95, and serum procalcitonin (PCT) > 0.36) had an AUC of 0.92 (Figure). The chances of a true UTI increased from 5% to 60% to 93% among patients with risk scores of 0-1, 2, and 3-5, respectively (p<0.001).CONCLUSIONS: Currently, only 50% of patients with a suspected UTI and an obstructing stone are ultimately found to have a true UTI. A risk score (consisting of gram stain, pyuria, perinephric fat stranding, CRP, and PCT) outperformed standard clinical variables in predicting a true UTI in patients with obstructing urolithiasis. We are currently validating this score to help elucidate which patients with obstruction and clinical suspicion for infection require decompression.