The dorsal root ganglia contain a variety of sensory neurons that transduce somatic stimuli. Following peripheral nerve injury, sensory neurons have to adapt to a new environment in order to successfully promote their axonal elongation. Unsuccessful regeneration leads to post-traumatic neuropathies, such ataxia and pain-related behavior, which are often chronic and mostly resistant to current treatments. Understanding the cellular and molecular mechanisms leading to improved neurite re-growth is a major step to propose a new therapy for nerve repair. It has been demonstrated that a prior in vivo nerve injury enhances both peripheral and central axonal regeneration following a second injury. In vitro, the neurons conditioned by the first traumatism display a faster, elongated mode of neurite growth called regenerative growth. The neuronal growth cone is a highly motile mechanosensitive structure at the tip of the axon. Elasticity is a determining parameter of membrane mechanical properties and provides important information toward the health and function of the cell. Interestingly, it has been shown that membrane tension influences growth cones dynamics. We have investigated, using DIC and AFM, the morphology and the membrane mechanical properties of adult sensory neurons from mice DRG following left sciatic nerve injury.

Comparative studies on the nanomechanics of normal and malignant cells of the same type are of great importance as they can reveal new information about, and help understanding mechanisms of malignant transformation. In this work, we investigate the morphology and the elastic properties of live cultured, normal human mammalian epithelial cells (HMEC) and breast carcinoma epithelial cells (MCF7), using atomic force microscopy (AFM). We describe the different behaviour of the two similar cell lines under curcumin treatment. Up to a six-hour long treatment leaves the MCF7 cells morphology non-affected, but the microtubules of HMEC cells disassemble and form a ring-like organization circumscribing the nuclear area. The observed morphological changes were correlated to modifications in cell's mechanics via elasticity force-volume measurements. Curcumin treatment modified elasticity of the HMEC cells increasing dramatically the cell's average Young's modulus. Contrariwise, a slight decrease in the Young's modulus value was noticed for the MCF7 cells, as they become softer due to the action of curcumin. This different response of the malignant and non-malignant cells under the same treatment might be of high importance in developing follow-up therapy against breast cancer. Moreover, we also explore the effectiveness of paclitaxel on MCF7 cells. Although paclitaxel is used widely in the treatment of breast cancer, not all tumors respond to this drug, and the characteristics that distinguish resistant tumors from sensitive ones are not well defined.

Porous silicon microcavity (PSiMc) structures were used to immobilize photosynthetic reaction center (RC) purified from the purple bacterium Rhodobacter sphaeroides R-26. Two different binding methods were compared by specular reflectance measurements. Structural characterization of PSiMc was performed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The activity of the immobilized RC was checked by measuring the visible absorption spectra of the externally added electron donor, mammalian cytochrome c. PSi/RC complex was found to oxidize the cytochrome c after every saturating Xe flash, indicating the accessibility of specific surface binding sites on the immobilized RC, for the external electron donor. This new type of bio-nanomaterial is considered as an excellent model for new generation applications of silicon based electronics and biological redox systems.

Surface functionalization methods were investigated for their effects on the sensing performances of porous silicon (p-Si) microcavities when used for detection of biomolecules. These microcavities were fabricated to reveal reflectivity pass-band spectra in the visible and near-infrared spectral regime. In one approach, the devices were thermally oxidized and functionalized to ensure covalent binding of molecules. In the second approach, the as-etched p-Si surface was modified with adhesion peptides, isolated via phage display, that present high binding capacity for silicon. Functionalization and molecular binding events were monitored via reflectometric interference spectra as shifts in the resonance peaks of the cavity structure due to changes in the refractive index when a biomolecule is attached to the large internal surface of p-Si. Improved sensitivity was obtained owing to the peptide interface linkers between the p-Si and biological molecules compared to the silanized devices. Investigating the formation of pep- tide-Si interface layer via X-ray photoelectron spectroscopy, scanning tunneling microscopy, and scanning electron microscopy, we found that peptides form nanometer-thin layers on the Si surface and that their binding energy depends on the sequence of the peptide.