Coplanar molecular assemblies of amino- and perfluorinated alkylsilanes: characterization and geometric definition of mammalian cell adhesion and growth

Abstract

The photochemistry of organosilanes was used to (1) create mixed monolayers having continuously adjustable surface free energies and (2) affect high resolution adhesion and spatial orientation of biological cells on silica substrates. Monolayers were formed from two materials, an aminoalkylsilane, NH2(CH2)2NH(CH2)3Si(OCH3)3 (EDA), and a perfluorinated alkylsilane, CF3(CF2)s(CH2)2Si(CH3)zC1 (1 3F), and were characterized by ellipsometry and water contact angle measurements. Deep UV (193 nm) radiation was used to induce photochemical changes in the cell-adhesive EDA monolayers. X-ray photoelectron spectroscopy indicated that the amine groups of EDA were removed by the exposure, leaving only Si-OH or alkyl fragments having 5 3 carbons. The exposed substrates were then reacted with 13F to form mixed monolayers or hydrophobic monolayers that inhibited cell adhesion in the irradiated regions. The degree of 13F reactivity with EDA in the unirradiated regions was observed to be solvent-dependent, suggesting that conformational states of the surface amine groups lead to a reduction in their accessibility. The selective photochemistry was exploited to produce high resolution molecular patterns, defined using patterned irradiation, that were mapped with scanning Auger electron spectroscopy. The patterns were used to spatially control the adhesion and direct the outgrowth of rat hippocampal neurons and porcine aortic endothelial cells in vitro. Patterns of controlled geometry may provide new approaches to the study of surface-directed growth, intercellular communication, and organogenesis or be used to control the alignment of individual cells with transducer elements in biosensors and implants. IntroductionRecent reports have indicated that monolayer systems can be targeted for a variety of applications, including cell adhesion and patterning.',2 Several techniques have been introduced in the past few years for the production of patterned self-assembled monolayers (SAMs) of organic functionalitie~.~~~ One approach utilizes conventional photoresist methodology to produce high resolution patterns for the adhesion and growth of cells.2 A fundamentally new technique involves direct modification of SAMs by patterned deep UV e x p o s~r e .~~~ Molecules in the exposed regions of a SAM absorb the radiation and undergo photocleavage to yield surface residues. These residues can then be modified with a second type of functionality. This technique offers several

Biology on a Chip: Microfabrication for Studying the Behavior of Cultured Cells

“…Since then many studies in neuronal patterning have been performed in a variety of labs, using various methods, including surface modification by silane chemistry 113 137 Ti, 140 polystyrene, 130,131 Teflon (fluorinated ethylene propylene), [132][133][134][141][142][143][144] and biodegradable polymers. 145 These studies mainly yielded insights into the adhesion and guidance of neuronal growth by insoluble factors and could prove valuable for selective neuronal immobilization on future microsensors.…”

Tobacco mosaic virus adsorption on self-assembled and Langmuir–Blodgett monolayers studied by TIRF and SFM

“…Silica slides were aminated using N-(2-aminoethyl)(3-aminopropyl)trimethoxysilane (EDA) according to the method of Stenger et al [14] and stored under nitrogen until use. Single-layer LB films were prepared on hydrophobic OTSslides using three phospholipids (Avanti Polar Lipids): dipalmitoylphosphatidylserine (DPPS), dipalmitoylphosphatidylcholine (DPPC) or dipalmitoylethylphosphocholine (Et-DPPC) which were doped with 1 mol% of the dye 3,3′-dioctadecyloxacarbocyanine perchlorate (DiO) (Molecular Probes).…”

Surface Coating as a Key Parameter in Engineering Neuronal Network Structures In Vitro

“…However, culturing neurons within microfluidic chips over long terms is a challenge, possibly due to limited nutrient exchange. Surface chemistry [37][38][39] allowed elegantly patterned neuronal networks with potentially useful functions, but long term maintenance of the networks is a problem. SAMs [40,41] represent a convenient way for engineering cell adhesion [42], as SAMs do not involve complicated instruments during the experiment.…”