DIC imaging for identification of motor and sensory nerves

Identification of motor and sensory nerves is important in applications such as nerve injury repair.Conventional practice relies on time consuming staining methods for this purpose.Here,we use laser scanning infrared diferential interference contrast(IR-DIC)microscopy for label-free observation of the two types of nerve.Ventral and dorsal nerve roots of adult beagle dogs were collected and sections of different thicknesses were imaged with an IR-DIC microscope.Different texture patterns of the IR-DIC images of the motor and sensory nerve can be distinguished when the section thickness increases to 40 pm.This suggests that nerve fibers in motor and sensory nerves have different distribution patterns.The result hints a potential new way for more rapid identification of nerve type in peripheral nerve repair surgery.

Effect of chondroitin sulfate proteoglycans on neuronal cell adhesion, spreading and neurite growth in culture

As one major component of extracellular matrix （ECM） in the central nervous system, chondroitin sul- fate proteoglycans （CSPGs） have long been known as inhibitors enriched in the glial scar that prevent axon regeneration after injury. Although many studies have shown that CSPGs inhibited neurite out- growth in vitro using different types of neurons, the mechanism by which CSPGs inhibit axonal growth remains poorly understood. Using cerebellar granule neuron （CGN） culture, in this study, we evaluated the effects of different concentrations of both immobilized and soluble CSPGs on neuronal growth, in- cluding cell adhesion, spreading and neurite growth. Neurite length decreased while CSPGs concentration arised, meanwhile, a decrease in cell density accompanied by an increase in cell aggregates formation was observed. Soluble CSPGs also showed an inhibition on neurite outgrowth, but it required a higher concen- tration to induce cell aggregates formation than coated CSPGs. We also found that growth cone size was significantly reduced on CSPGs and neuronal cell spreading was restrained by CSPGs, attributing to an inhibition on lamellipodial extension. The effect of CSPGs on neuron adhesion was further evidenced by interference reflection microscopy （IRM） which directly demonstrated that both CGNs and cerebral cortical neurons were more loosely adherent to a CSPG substrate. These data demonstrate that CSPGs have an effect on cell adhesion and spreading in addition to neurite outgrowth.

FEM-based modeling of microsphereenhanced interferometry

To improve the lateral resolution in microscopic imaging,microspheres are placed close to the object’s surface in order to support the imaging process by optical near-field information.Although microsphere-assisted measurements are part of various recent studies,no generally accepted explanation for the effect of microspheres exists.Photonic nanojets,enhancement of the numerical aperture,whispering-gallery modes and evanescent waves are usually named reasons in context with microspheres,though none of these effects is proven to be decisive for the resolution enhancement.We present a simulation model of the complete microscopic imaging process of microsphere-enhanced interference microscopy including a rigorous treatment of the light scattering process at the surface of the specimen.The model consideres objective lenses of high numerical aperture providing 3D conical illumination and imaging.The enhanced resolution and magnification by the microsphere is analyzed with respect to the numerical aperture of the objective lenses.Further,we give a criterion for the achievable resolution and demonstrate that a local enhancement of the numerical aperture is the most likely reason for the resolution enhancement.

Realization of palladium-based optomechanical cantilever hydrogen sensor

Hydrogen has attracted attention as an alternative fuel source and as an energy storage medium.However,the flammability of hydrogen at low concentrations makes it a safety concern.Thus,gas concentration measurements are a vital safety issue.Here we present the experimental realization of a palladium thin film cantilever optomechanical hydrogen gas sensor.We measured the instantaneous shape of the cantilever to nanometer-level accuracy using diffraction phase microscopy.Thus,we were able to quantify changes in the curvature of the cantilever as a function of hydrogen concentration and observed that the sensor’s minimum detection limit was well below the 250 p.p.m.limit of our test equipment.Using the change in curvature versus the hydrogen curve for calibration,we accurately determined the hydrogen concentrations for a random sequence of exposures.In addition,we calculated the change in film stress as a function of hydrogen concentration and observed a greater sensitivity at lower concentrations.