title: Gradients of substrate-bound laminin orient axonal specification of neurons.
abstract: Little is known about the influence of substrate-bound gradients on neuronal development, since it has been difficult to fabricate gradients over the distances typically required for biological studies (a few hundred micrometers). This article demonstrates a generally applicable technique for the fabrication of substrate-bound gradients of proteins with complex shapes, using laminar flows in microchannels. Gradients that range from pure laminin to pure BSA were formed in solution by using a network of microchannels, and these proteins were allowed to adsorb onto a homogeneous layer of poly-l-lysine. Rat hippocampal neurons were cultivated on these substrate-bound gradients. Analysis of optical images of these neurons showed that axon specification is oriented in the direction of increasing surface density of laminin. Linear gradients in laminin adsorbed from a gradient in solution having a slope of nabla [laminin] > about 0.06 microg (ml.microm)(-1) (defined by dividing the change of concentration of laminin in solution over the distance of the gradient) orient axon specification, whereas those with nabla [laminin] < about 0.06 microg (ml.microm)(-1) have no effect.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Stephan K W
authors.initials: SK
authors.lastname: Dertinger
authors.forename: Xingyu
authors.initials: X
authors.lastname: Jiang
authors.forename: Zhiying
authors.initials: Z
authors.lastname: Li
authors.forename: Venkatesh N
authors.initials: VN
authors.lastname: Murthy
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000648:ultrastructure; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D005109:Extracellular Matrix / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D007797:Laminin / Q000737:chemistry*; D008956:Models, Chemical; D009474:Neurons / Q000378:metabolism; D011107:Polylysine / Q000737:chemistry*; D051381:Rats; D012828:Silicones / Q000737:chemistry
chemical_list: D004129:Dimethylpolysiloxanes; D007797:Laminin; D012828:Silicones; D011107:Polylysine; C013830:baysilon