Sol-gel derived materials as substrates for neuronal differentiation: effects of surface features and protein conformation

Abstract

This work demonstrates the ability of sol-gel derived materials to support the differentiation of neuronal cells, and investigates the physiochemical interactions between the surface and extracellular matrix proteins as a mediator of the effects of surface features on differentiation. We have applied fluorescence resonance energy transfer (FRET) spectroscopy to study the conformational changes of human serum fibronectin, a critical extracellular cell adhesion protein, after adsorption onto native and poly-L-lysine doped sol-gel derived silica thin films and bulk materials. The global conformation of fibronectin varied dramatically between native and organically modified materials and most interestingly between thin films and bulk materials of the same chemistry. A comparison of the surface topography of thin films and bulk materials by atomic force microscopy reveals that films of native silica have surface features less than the AFM tip size (,25 nm) while bulk materials of the same precursor chemistry have features ranging from 50-100 nm in size. Fibronectin assumed an inactive, globular, solution-like state on the larger feature size bulk gels and an active, fully extended fibrillar-like state on the smaller feature size films. Neither native nor PLL-doped bulk materials could support cell growth or neuronal differentiation of PC12 cells, in stark contrast to the thin films, which supported a robust neuronal phenotype. Morphological analysis and expression levels of the neuronal proteins b-tubulin and neurofilament, in addition to the FRET data, indicate that the effects of surface chemistry on fibronectin conformation, cellular adhesion, and differentiation are dependent upon the surface topography.

Lithography-based additive manufacture of ceramic biodevices with design-controlled surface topographies

“…Several strategies for modifying material topographies and surface properties have taken advantage of conventional surface micro-machining [7], laser ablation [8], micro-molding [9], biomimetic templating [10], physical and chemical vapor deposition processes [11], sol-gel procedures [12], and molecular self-assembly [13]. All these processes require enormous hands-on expertise and final result depends on several control parameters, whose interdependencies are normally complex to understand, characterize, model, and master [14].…”

Multi-Channeled Polymeric Microsystem for Studying the Impact of Surface Topography on Cell Adhesion and Motility

“…However, they can be also adjusted and controlled by means of machining processes, chemical etchings, and post-processing tools along the product development cycle. Several strategies for modifying material topographies and surface properties (towards hierarchical materials, structures, and multi-scale devices) have made use of conventional surface micromachining [12], laser ablation [13], micromolding [14], biomimetic templating [15], thin film deposition processes based on physical or chemical vapor deposition [16], sol-gel procedures [17], molecular self-assembly [18], and electro-spinning [19][20][21]. All these procedures require an expertise that is sometimes difficult to achieve and repeatability is not easy [22,23].…”

Materials approaches for modulating neural tissue responses to implanted microelectrodes through mechanical and biochemical means

“…The coating methods employed include covalent immobilization on dextran-coated surfaces (Massia et al, 2004), covalent immobilization on amino-modified glass (Kam et al, 2002), self-assembling peptide nanofibers (Wu et al, 2006; Tysseling-Mattiace et al, 2008), copolymerization with conductive polymers (Cui et al, 2001; Stauffer and Cui, 2006), electrostatic layer-by-layer deposition (He et al, 2006), microcontact printing (James et al, 2000; St. John et al, 1997), fiber templating within a hydrogel (Yu et al, 2005), and covalent binding to silica sol-gel (Jedlicka et al 2006; Jedlicka et al 2007a; Jedlicka et al 2007b). …”