Surface-Active and Stimuli-Responsive Polymer−Si(100) Hybrids from Surface-Initiated Atom Transfer Radical Polymerization for Control of Cell Adhesion

• Published in: Biomacromolecules 2004-11, Vol.5 (6), p.2392-2403
• Main Authors: Xu, F. J, Zhong, S. P, Yung, L. Y. L, Kang, E. T, Neoh, K. G
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Acrylamides - chemistry; Acrylates - chemistry; Animals; Applied sciences; Biocompatible Materials - chemistry; Biophysics - methods; Cell Adhesion; Cells, Cultured; Exact sciences and technology; Fibroblasts - metabolism; Hydrogen - chemistry; Mice; Microscopy, Atomic Force; Models, Chemical; Organic polymers; Physicochemistry of polymers; Polyethylene Glycols - chemistry; Polymers - chemistry; Polymers with particular structures; Polymethacrylic Acids - chemistry; Preparation, kinetics, thermodynamics, mechanism and catalysts; Protein Binding; Silicon - chemistry; Surface Properties; Surface-Active Agents - chemistry; Temperature; Time Factors; Ultraviolet Rays; Water - chemistry
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm049675a

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 °C [above the lower critical solution temperature (LCST, ∼32 °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.