title: Surface-active and stimuli-responsive polymer--Si(100) hybrids from surface-initiated atom transfer radical polymerization for control of cell adhesion.
abstract: A simple two-step method was developed for the covalent immobilization of atom-transfer radical polymerization (ATRP) initiators on the hydrogen-terminated Si(100) (Si-H) surface. Well-defined functional polymer-Si hybrids, consisting of covalently tethered brushes of poly(ethylene glycol) monomethacrylate (PEGMA) polymer, N-isopropylacrylamide (NIPAAm) polymer, and NIPAAm-PEGMA copolymers and block copolymers on Si-H surfaces, were prepared via surface-initiated ATRP. Kinetics study revealed that the chain growth from the silicon surface was consistent with a "controlled" process. Surface cultures of the cell line 3T3-Swiss albino on the hybrids were evaluated. The PEGMA graft-polymerized silicon [Si-g-P(PEGMA)] surface is very effective in preventing cell attachment and growth. At 37 degrees C [above the lower critical solution temperature (LCST, approximately 32 degrees C) of NIPAAm], the seeded cells adhered, spread, and proliferated on the NIPAAm graft polymerized silicon [Si-g-P(NIPAAm)] surface. Below the LCST, the cells detached from the Si-g-P(NIPAAm) surface spontaneously. Incorporation of PEGMA units into the NIPAAm chains of the Si-g-P(NIPAAm) surface via copolymerization resulted in more rapid cell detachment during the temperature transition. The "active" chain ends on the Si-g-P(PEGMA) and Si-g-P(NIPAAm) hybrids were also used as the macroinitiators for the synthesis of diblock copolymer brushes. Thus, not only are the hybrids potentially useful as stimuli-responsive adhesion modifiers for cells in silicon-based biomedical microdevices but also the active chain ends on the hybrid surfaces offer opportunities for further surface functionalization and molecular design.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge, Singapore 119260.
authors.forename: F J
authors.initials: FJ
authors.lastname: Xu
authors.forename: S P
authors.initials: SP
authors.lastname: Zhong
authors.forename: L Y L
authors.initials: LY
authors.lastname: Yung
authors.forename: E T
authors.initials: ET
authors.lastname: Kang
authors.forename: K G
authors.initials: KG
authors.lastname: Neoh
mesh_terms: D016475:3T3 Cells; D000178:Acrylamides / Q000737:chemistry; D000179:Acrylates / Q000737:chemistry; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D001703:Biophysics / Q000379:methods*; D002448:Cell Adhesion; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry; D051379:Mice; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011485:Protein Binding; D012825:Silicon / Q000737:chemistry; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D000178:Acrylamides; D000179:Acrylates; D001672:Biocompatible Materials; C090629:N-isopropylacrylamide-acrylic acid copolymer; D011108:Polymers; D011109:Polymethacrylic Acids; D013501:Surface-Active Agents; C466018:poly(triethylene glycol monomethacrylate); D014867:Water; D011092:Polyethylene Glycols; D006859:Hydrogen; D012825:Silicon