Neurite outgrowths of neurons using neurotrophin-coated nanoscale magnetic beads.

Neurotrophin-coated nanoscale magnetic beads were used to regulate the differentiation and survival of neurons. The beads coated with nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) promoted neurite outgrowths of neurons in the same manner as soluble NGF or soluble BDNF, but beads coated with bovine serum albumin did not promote neurite outgrowths. When the volume of NGF-coated bead solution was increased, the number of neurons with neurite outgrowths increased. The addition of anti-NGF antibodies decreased the numbers of neurons with neurite outgrowths in proportion to the volume of anti-NGF antibodies added. NGF-coated beads appeared to bind to soma with neurite outgrowths as determined using fluorescence. In addition, hybrid beads coated with both NGF and BDNF promoted neurite outgrowths of PC12h cells, although the cells did not produce neurite outgrowths in response to BDNF. Neurons with neurite outgrowths could be concentrated within a particular area when NGF-coated beads were immobilized in a particular area of the culture plate surface using a magnet. The results demonstrate that neurotrophin-coated nanoscale magnetic beads allow us to cultivate neurons in a selected area of the culture plate surface by using a magnet. Thus, neurotrophin-coated nanoscale magnetic beads are applicable to micro-integrated systems and biosensors.