Dorsal root ganglia (DRG) 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 (regenerative growth mode). Unsuccessful regeneration leads to post-traumatic neuropathies, such ataxia and pain-related behavior, which are often chronic and mostly resistant to current treatments. Therefore understanding the cellular and molecular mechanisms leading to improved neurite re-growth is a major step to propose new therapies for nerve repair. In this work, we use differential interference contrast microscopy (DIC), fluorescence microscopy and atomic force microscopy (AFM) to study the morphological and nanomechanical properties of mice DRG sensory neurons in regenerative growth mode. DIC 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 longer and larger neurites and growth cones. Our AFM data indicate that conditioned neurons are characterized by softer growth cones and cell bodies, compared to control neurons. As cell elasticity is related mainly to the intrinsic properties of the cell membrane and cytoskeleton structures such as microtubules and actin fibers, the increase of the cell membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins. Furthermore, in order to evidence structural differences between conditioned and control somas and growth cones, we use immunocytochemistry to localize actin (anti-actin antibody) and neuronal microtubules (anti-βIII-tubulin).

Despite extensive recent research efforts on material-specific peptides, the fundamental problem to be explored yet is the molecular interactions between peptides and inorganic surfaces. Here we used computer simulations (density functional theory and classical molecular dynamics) to investigate the adsorption mechanism of silicon-binding peptides and the role of individual amino acids in the affinity of peptides for an n-type silicon (n+-Si) semiconductor. Three silicon binding 12-mer peptides previously elaborated using phage display technology have been studied. The peptides' conformations close to the surface have been determined and the best-binding amino acids have been identified. Adsorption energy calculations explain the experimentally observed different degrees of affinity of the peptides for n+-Si. Our residual scanning analysis demonstrates that the binding affinity relies on both the identity of the amino acid and its location in the peptide sequence.

Engineering shape-controlled bionanomaterials requires comprehensive understanding of interactions between biomolecules and inorganic surfaces. We explore the origin of facet-selective binding of peptides adsorbed onto Pt(100) and Pt(111) crystallographic planes. Using molecular dynamics simulations, we show that upon adsorption the peptides adopt a predictable conformation. We compute the binding energies of the amino acids constituting two adhesion peptides for Pt, S7, and T7 and demonstrate that peptides' surface recognition behavior that makes them unique among populations originates from differential adsorption of their building blocks. We find that the degree of peptide binding is mainly due to polar amino acids and the molecular architecture of the peptides close to the Pt facets. Our analysis is a first step in the prediction of enhanced affinity between inorganic materials and a peptides, toward the synthesis of novel nanomaterials with programmable shape, structure, and properties.

Peripheral nerve injury in vivo promotes a regenerative growth in vitro characterized by an improved neurite regrowth. Knowledge of the conditioning injury effects on both morphology and mechanical properties of live sensory neurons could be instrumental to understand the cellular and molecular mechanisms leading to this regenerative growth. In the present study, we use differential interference contrast microscopy, fluorescence micros- copy, and atomic force microscopy (AFM) to show that conditioned axotomy, induced by sciatic nerve injury, does not increase somatic size of sensory neurons from adult mice lumbar dorsal root ganglia but promotes the appear- ance of longer and larger neurites and growth cones. AFM on live neurons is also employed to investigate changes in morphology and membrane mechanical properties of somas of conditioned neurons following sciatic nerve injury. Mechanical analysis of the soma allows distinguishing neurons having a regenerative growth from control ones, although they show similar shapes and sizes.