Application of atomic force microscopy to investigate axonal growth of PC-12 Neuron-like cells

A nerve conduit with suitable biomechanical and biochemical environment may improve the regeneration of axons of the injured peripheral nerve. The PC-12 cells were cultured in PRMI medium 1640 and then axonal growth was induced by using nerve growth factor. Time-course morphological changes of the cells were analyzed by using an optical microscope. Regional viscoelasticity and adhesion force of axons were measured by an atomic force microscope by using ramp-and-hold indentation and scratching. The data were fitted with a quasi-viscoelastic model by a method developed previously. Morphological results revealed that cell body length and branch number were highly correlated with axonal growth process and average axon length can be used to define the stage of growth process. Electrical field with intensity of 100mV/mm could enhance the growth rate of axons by 2.88 folds. AFM results showed that the mean elastic modulus of axon increased with stage and the growth cone region has higher Young's modulus than the middle region. Furthermore, the adhesion force on middle region of axon was smaller than that of proximal region and growth cone.