PMN encounter artificial surfaces ex vivo when they are processed and stored in blood collection devices and containers prior to transfusion, and in vivo in patients who receive implants and intravenous catheters. Ideally, artificial materials in contact with blood components should not significantly alter the functional responses of cells or stimulate an inflammatory response at the implant site. The goal of this project is to determine whether hydrophilic and hydrophobic substrate surface modifications that occur on biomaterials alter human neutrophil (PMN) motility. The substitution of individual chemical functionalities on synthetic surfaces is useful for examining the effects of specific chemical moieties on cell function. A collaborative project was undertaken with J.J. Hickman (a surface chemist at SAIC, McLean, VA) to determine whether relatively simple chemical modifications to artificial surfaces alter PMN migratory behavior. Polycarbonate membrane surfaces were modified with self-assembled silane monolayers containing various functionalities including amines and hydrophobic groups. The poly-carbonate surfaces were assessed by contact angle measurements and X-ray photoelectron spectroscopy. The chemically-defined surfaces were evaluated for their effects on human PMN random motility and chemotactic migration to the N-formyl peptide chemoattractant, FMLP. Migratory responses were evaluated on four polycarbonate surfaces: 1) Control, untreated polycarbonate, 2) hydroxyl-rich polycarbonate, 3) hydrophilic alkyl silane (DETA), and 4) hydrophobic alkyl silane (13F). The results of these experiments indicated that selected hydrophilic surface modifications such as DETA and hydroxyl moieties enhanced the random, unstimulated motility of human neutrophils, whereas, hydrophobic surface modifications did not alter random motility. None of the surface modifications inhibited PMN chemotactic migration to FMLP. These experiments provide the foundation of a system for quantitatively evaluating the effects of other chemical functionalities on PMN migration. Future studies will include the evaluation of sulfhydryl-rich surfaces and the effects of exogenous protein on PMN interactions with the modified biomaterial surfaces.
