The possibility to engineer bio-nanomaterials with programmed synthesis and controlled immobilization of biomolecules through biomimetic molecular evolution approach has been demonstrated. Material specific peptides with exquisite molecular recognition function were used as a linker for the attachment of biomolecules. Exploring the origin of peptide material specificity not only opens up rational design approach with precise control over biomimetic bio-sensor design, but more importantly provides a new route of functionalizing for various material surfaces with enhanced sensitivity over classical grafting chemistry. To study the fine prints of experimentally obtained peptides, theoretical understanding of surface interactions may serve as important clues for further refinement. By taking advantage of classical molecular dynamics (MD) simulations and density functional theory (DFT), we investigated the origin of this smart recognition function through the strength of interaction of experimentally selected 12mer peptides revealing high binding affinity towards n+-Si(100). Here, we attempt for the very first time to model the interaction of the peptides (in buffer solution) with semiconductors and we calculate their binding energies at the atomic level, enabling thereby linking direct evidence to our experimental evidence. Several peptide conformations have been taken into account simultaneously upon the surface. Our studies demonstrate that the peptides possess certain recognition function and their high interaction energy with the surface makes them unique among the populations. Our work is a step towards the understanding of the interactions between peptides and semiconductor surfaces that is a highly relevant challenge in the development of novel devices with a high degree of biocompatibility as well.

We use atomic force microscopy (AFM) to study the morphological and nanomechanical properties of mice dorsal root ganglia sensory neurons in regenerative growth mode. A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of sensory neurons neurite regrowth in vitro. Complementary differential interference contrast microscopy results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons but promoted the appearance of larger growth cones. Our AFM data indicate that neurons having a regenerative growth are characterized by softer growth cones, compared to control neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins.

A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of sensory neurons neurite regrowth in vitro. This in vitro model of conditioned axotomy allows analysis of the cellular and molecular mechanisms leading to an improved neurite re-growth. Our differential interference contrast microscopy and immunocytochemistry results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons from mice dorsal root ganglia sensory neurons but promoted the appearance of larger neurites and growth cones. Using atomic force microscopy on live neurons, we investigated whether membrane mechanical properties of growth cones of axotomized neurons were modified following sciatic nerve injury. Our data revealed that neurons having a regenerative growth were characterized by softer growth cones, compared to control neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins.

The purified photosynthetic reaction center protein (RC) from Rhodobacter sphaeroides R-26 purple bacteria was bound to porous silicon microcavities (PSiMc) either through silane-glutaraldehyde (GTA) chemistry or via a noncovalent peptide cross-linker. The characteristic resonance mode in the microcavity reflectivity spectrum red shifted by several nanometers upon RC binding, indicating the protein infiltration into the porous silicon (PSi) photonic structure. Flash photolysis experiments confirmed the photochemical activity of RC after its binding to the solid substrate. The kinetic components of the intraprotein charge recombination were considerably faster (τfast = 14 (±9) ms, τslow = 230 (±28) ms with the RC bound through the GTA cross-linker and only τfast = 27 (±3) ms through peptide coating) than in solution (τfast = 120 (±3) ms, τslow = 1387 (±2) ms), indicating the effect of the PSi surface on the light-induced electron transfer in the protein. The PSi/RC complex was found to oxidize the externally added electron donor, mammalian cytochrome c, and the cytochrome oxidation was blocked by the competitive RC inhibitor, terbutryne. This fact indicates that the specific surface binding sites on the PSi-bound RC are still accessible to external cofactors and an electronic interaction with redox components in the aqueous environment is possible. This new type of biophotonic material is considered to be an excellent model for new generation applications at the interface of silicon-based electronics and biological redox systems designed by nature.

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.

Multiphoton microscopy has been used to reveal structural details of dentine and enamel at the dentin-enamel junction (DEJ) based on their 2-photon excited fluores- cence (2PEF) emission and second harmonic generation (SHG). In dentine tubule 2PEF intensity varies due to protein content variation. Intertubular dentin produces both SHG and 2PEF signals. Tubules are surrounded by a thin circular zone with a lower SHG signal than the bulk dentine and the presence of collagen fibers perpen- dicular to the tubule longitudinal axis is indicated by strong SHG responses. The DEJ appears as a low inten- sity line on the 2PEF images and this was never pre- viously reported. The SHG signal is completely absent for enamel and aprismatic enamel shows a homogeneous low 2PEF signal contrary to prismatic enamel. The SHG intensity of mantle dentine is increasing from the dentine-enamel junction in the first 12 mm indicating a progressive presence of fibrillar collagen and corresponding to the more external part of mantle dentine where matrix metallo-proteases accumulate. The high information content of multiphoton images confirms the huge potential of this method to investigate tooth structures in physiological and pathological conditions. Dentine-Enamel Junction. Superposition of SHG and 2PEF images showing the relationship of enamel and dentine.