Precise microscale arrangement of biomolecules and cells is essential for tissue engineering, microarray development, diagnostic sensors, and fundamental research in the biosciences. Biofunctional polymer brushes have attracted broad interest in these applications. However, patterning approaches to creating microstructured biointerfaces based on polymer brushes often involve tedious, expensive, and complicated procedures that are specifically designed for model substrates. We report a substrate-independent, facile, and scalable technique with which to prepare micropatterned biofunctional brushes with the ability to generate binary chemical patterns. Employing chemical vapor deposition (CVD) polymerization, a functionalized polymer coating decorated with 2-bromoisobutyryl groups that act as atom-transfer radical polymerization (ATRP) initiators was prepared and subsequently modified using UV light. The exposure of 2-bromoisobutyryl groups to UV light with wavelengths between 187 and 254 nm resulted in selective debromination, effectively eliminating the initiation of ATRP. In addition, when coatings incorporating both 2-bromoisobutyryl and primary amine groups were irradiated with UV light, the amines retained their functionality after UV treatment and could be conjugated to activated esters, facilitating binary chemical patterns. In contrast, polymer brushes were selectively grown from areas protected from UV treatment, as confirmed by atomic force microscopy, time-of-flight secondary ion mass spectrometry, and imaging ellipsometry. Furthermore, spatial control over biomolecular adhesion was achieved in three ways: (1) patterned nonfouling brushes resulted in nonspecific protein adsorption to areas not covered with polymer brushes; (2) patterned brushes decorated with active binding sides gave rise to specific protein immobilization on areas presenting polymer brushes; (3) and primary amines were co-patterned along with clickable polymer brushes bearing pendant alkyne groups, leading to bifunctional reactivity. Because this novel technique is independent of the original substrate's physicochemical properties, it can be extended to technologically relevant substrates such as polystyrene, polydimethylsiloxane, polyvinyl chloride, and steel. With further work, the photolytic deactivation of CVD-based initiator coatings promises to advance the utility of patterned biofunctional polymer brushes across a spectrum of biomedical applications.
Bibliographical noteFunding Information:
We acknowledge the Defense Threat Reduction Agency (DTRA) for funding provided through grant no. HDTRA1-12-1-0039 as a part of the interfacial dynamics and reactivity program. We gratefully acknowledge the Engineering Research Centers Program of the National Science Foundation for funding provided through award EEC-1647837. R.K. gratefully acknowledges Rackham Graduate School (University of Michigan, Ann Arbor, MI) for providing financial support through the Rackham Predoctoral Fellowship. A.W. acknowledges Gina Irina Wach, Institute for Functional Interfaces, for technical assistance. R.K. and I.K. thank Linda Barthel of Microscopy and Image Analysis (MIL) for technical advice. We thank Daniel Quevedo for movie editing. We acknowledge Imed Ayadi and co-workers at Nanolane for SEEC measurements. We also acknowledge the BioInterFaces in Technology and Medicine program (BIFTM) at Karlsrushe Institute of Technology.
- chemical vapor deposition
- micropatterned polymer brushes
- protein patterning