Molecular Organization in SAMs Used for Neuronal Cell Growth

Abstract

The attachment of cells onto solid supports is fundamental in the development of advanced biosensors or biochips. In this work, we characterize cortical neuron adhesion, growth, and distribution of an adhesive layer, depending on the molecular structure and composition . Neuronal networks are successfully grown on amino-terminated alkanethiol self-assembled monolayer (SAM) on a gold substrate without adhesion protein interfaces. Neuron adhesion efficiency was studied for amino-terminated, carboxy-terminated, and 1:1 mixed alkanethiol SAMs deposited on gold substrates. Atomic force microscopy and X-ray photoelectron spectroscopy were used to measure the roughness of gold substrate and thickness of SAM monolayers. Conformational ordering and ionic content of SAMs were characterized by vibrational sum frequency generation (VSFG) spectroscopy. Only pure amino-terminated SAMs provide efficient neuronal cell attachment. Ordering of the terminal amino groups does not affect efficiency of neuron adhesion. VSFG analysis shows that ordering of the terminal groups improves with decreasing surface roughness; however the number of gauche defects in alkane chains is independent of surface roughness. We monitor partial dissociation of carboxy groups in mixed SAMs that implies formation of NH3+ neighbors and appearance of catanionic structure. Such catanionic environment proved inefficient for neuron adhesion. Surface roughness of metal within the 0.7-2 nm range has little effect on the efficiency of neuron adhesion. This approach can be used to create new methods that help map structure-property relationships of biohybrid systems.

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

“…Many cell types have been successfully patterned with microfluidics [14][15][16], lCP [17], inkjet printing [18,19], plasma treatment [20], self-assembled monolayers [21][22][23][24], self-assembled constructs [25], laser scanning lithography [26], atomic force microscope lithography, dip-pen nanolithography [27], topography [28,29], carbon nano-tubes [30], or their combinations [31,32]. Neurons are, however, distinctive cells with highly polarized morphology, much smaller somata, and thus few anchoring points for adhesion in comparison to most types of adherent mammalian cells.…”

Light Switching of Molecules on Surfaces

“…Recently Forster et al (18) reported the photosubstitution of chlorido for aqua ligands in an Ru(II) polypyridyl complex, [Ru(bpy) 2 (4-pyridyl)ethylene]. The complex forms well-defined SAMs and undergoes loss of either the bpe anchoring ligand or the chlorido ligand, depending on the solvent employed, with aqueous solvents favoring the substitution of the latter ligand.…”

“…Smart surfaces, surfaces that can respond to a specific external stimulus in a specific manner, are of increasing interest in areas as diverse as cell culture (1,2), microfluidics (3,4), organic electronics (5), and coatings (6,7). When combined with the flexibility provided through molecular synthesis, supramolecular chemistry, and surface science, exciting opportunities emerge toward the development of smart molecular materials and devices.…”

Vibrational spectroscopy for probing molecular-level interactions in organic films mimicking biointerfaces

“…The growth and adhesion of cortical neurons on self-assembled monolayers depends on the functional groups for amino-terminated, carboxyterminated and 1:1 mixed alkanethiol monolayers on gold, as described by Palyvoda et al [169]. Using SFG they inferred that the ordering of the terminal amino groups does not affect the ability for neuron adhesion, while the dissociation of carboxylic groups hampers neuron attachment.…”