In this work, bioadhesive behavior of plasma proteins and blood cells from umbilical cord blood (UCB) onto zwitterionic poly(sulfobetaine methacrylate) (polySBMA) polymer brushes was studied. The surface coverage of polySBMA brushes on a hydrophobic polystyrene (PS) well plate with surface grafting weights ranging from 0.02 mg/cm(2) to 0.69 mg/cm(2) can be effectively controlled using the ozone pretreatment and thermal-induced radical graft-polymerization. The chemical composition, grafting structure, surface hydrophilicity, and hydration capability of prepared polySBMA brushes were determined to illustrate the correlations between grafting properties and blood compatibility of zwitterionic-grafted surfaces in contact with human UCB. The protein adsorption of fibrinogen in single-protein solutions and at complex medium of 100% UCB plasma onto different polySBMA brushes with different grafting coverage was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. The grafting density of the zwitterionic brushes greatly affects the PS surface, thus controlling the adsorption of fibrinogen, the adhesion of platelets, and the preservation of hematopoietic stem and progenitor cells (HSPCs) in UCB. The results showed that PS surfaces grafted with polySBMA brushes possess controllable hydration properties through the binding of water molecules, regulating the bioadhesive and bioinert characteristics of plasma proteins and blood platelets in UCB. Interestingly, it was found that the polySBMA brushes with an optimized grafting weight of approximately 0.1 mg/cm(2) at physiologic temperatures show significant hydrated chain flexibility and balanced hydrophilicity to provide the best preservation capacity for HSPCs stored in 100% UCB solution for 2 weeks. This work suggests that, through controlling grafting structures, the hemocompatible nature of grafted zwitterionic polymer brushes makes them well suited to the molecular design of regulated bioadhesive interfaces for use in the preservation of HSPCs from human UCB.

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The separation of hematopoietic stem and progenitor cells (CD34 þ cells) from peripheral blood was investigated using foamed polyurethane (PU) membranes modified with several amino acids. CD34 þ cells were collected by first allowing the blood to permeate through the membranes, and then passing the recovered solution through the membranes. Optimal conditions for the separation of CD34 þ cells were investigated. The highest recovery ratio of CD34 þ cells was obtained using three sheets of PU membranes having carboxylic acid groups (PUACOOH) modified with glycine, the membranes having been pretreated by immersion in phosphate buffer solution prior to permeation of blood. A high recovery ratio of CD34 þ cells was achieved in a recovery process using 0.5 wt % human serum albumin (HSA) or 20% dextran solution passed through PUACOOH membranes. The recovery ratios of CD34 þ cells using platelet-poor plasma and platelet-rich plasma were approximately 20% and 30%, respectively, significantly less than the ratio found using 0.5 wt % HSA solution. Surface-modified membranes having carboxylic acid groups showed a higher recovery ratio of CD34 þ cells than membranes having zwitterionic groups. The effect of carboxylic acid groups on the surface-modified PU membranes was to generate weak interactions by electrostatic repulsion between CD34 þ cells and the membranes because of the negatively charged surfaces of the cells, allowing them to be detached from the membranes and collected in the recovered solution.