The application of microbeads to microfluidic systems for enhanced detection and purification of biomolecules.

This paper describes microbead-based microfluidic systems. Several aspects of bead assays in microfluidics make them advantageous for bioassays in simple microchannels, including enhanced surface-to-volume ratio, improved molecular recognition reaction efficiency, and the wide range of surface functionalization available with commercial microbeads. Two-level SU-8 molds are used to fabricate PDMS microchannels that can hydrodynamically trap different types of microbeads, with characteristic dimensions of tens of microns. The use of these microbead-based microfluidic systems in the biosensing of antibodies, toxins and nucleic acids, as well as in antibody purification will be presented and discussed in this paper.

Preoperative plasma levels of soluble tumor necrosis factor receptor type I (sTNF-RI) predicts adverse events in cardiac surgery.

OBJECTIVE: The objective was to estimate the sTNF-RI preoperative measure in the identification of patients with bad outcome and death. METHODS: We assessed prospectively sixty-two patients submitted electively to myocardial revascularization with ECC or heart valve surgery. The sTNF-RI levels were determined by the Sandwich-Type ELISA method before anesthetic induction. Clinical, surgical characteristics and sTNF-RI levels were compared among patients with good (group I, n=46) or bad outcome (group II, n=16--length of stay in the ICU for over 72 h or death). RESULTS: No difference was found between the verified mortality (6.4%) and the predicted by EuroSCORE (3.0%), p=0.48. The sTNF-RI levels were higher in group II (1322) than group I (748) p=0.009 (levels >954, 69% sensitivity and 70% specificity for good outcome, 44% positive predicted value and 85% negative). The sTNF-RI levels were higher in patients who died (1556) versus (759) p=0.029, (levels >1230, 79% sensitivity, 75% specificity, 20% positive predicted value and 98% negative). In the multivariate logistic regression model sTNF-RI (OR=1.002, IC95% 1.000-1.005, p=0.014) and age (OR=1.083, IC95% 1.010-1.161, p=0.025) were independently related to the risk of bad outcome. CONCLUSIONS: Basal levels of sTNF-RI yield prognostic information in patients who undergo heart surgery.