biostudies-literatureDertinger SKNINDS NIH HHSNIGMS NIH HHS12542-7https://www.ebi.ac.uk/biostudies/studies/S-EPMC130496biostudies-literatureUnknown99(20)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.Proceedings of the National Academy of Sciences of the United States of AmericaGradients of substrate-bound laminin orient axonal specification of neurons.PMC130496NS039059R01 NS039059R37 GM030367R01 GM030367GM 30367Li ZMurthy VNJiang XWhitesides GMDertinger SKfalseGradients of substrate-bound laminin orient axonal specification of neurons.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.2002-01-01T00:00:00Z2002 Oct2020-08-31T07:14:06Z2019-03-27T00:12:55ZS-EPMC1304961223740710.1073/pnas.192457199