Axonal regeneration is one of the greatest challenges in severe injuries of peripheral nerve. To provide the bridge needed for regeneration, biological or synthetic tubular nerve constructs with aligned architecture have been developed. A key point for improving axonal regeneration is assessing the effects of substrate geometry on neuronal behavior. In the present study, we used an extracellular matrix-micropatterned substrate comprising 3 mm wide lines aimed to physically mimic the in vivo longitudinal axonal growth of mice peripheral sensory and motor neurons. Adult sensory neurons or embryonic motoneurons were seeded and processed for morphological and electrical activity analyses after two days in vitro. We show that micropattern-guided sensory neurons grow one or two axons without secondary branching. Motoneurons polarity was kept on micropattern with a long axon and small dendrites. The micro-patterned substrate maintains the growth promoting effects of conditioning injury and demonstrates, for the first time, that neurite initiation and extension could be differentially regulated by conditioning injury among DRG sensory neuron subpopulations. The micro-patterned substrate impacts the excitability of sensory neurons and promotes the apparition of firing action potentials characteristic for a subclass of mechanosensitive neurons. The line pattern is quite relevant for assessing the regenerative and developmental growth of sensory and motoneurons and offers a unique model for the analysis of the impact of geometry on the expression and the activity of mechanosensitive channels in DRG sensory neurons.

The way cells explore their surrounding extracellular matrix (ECM) during development and migration is mediated by lamellipodia at their leading edge, acting as an actual motor pulling the cell forward. Lamellipodia are the primary area within the cell of actin microfilaments (filopodia) formation. In this work, we report on the use of porous silicon (pSi) scaffolds to mimic the ECM of mesenchymal stem cells from the dental pulp (DPSC) and breast cancer (MCF-7) cells. Our atomic force microscopy (AFM), fluorescence microscopy, and scanning electron microscopy (SEM) results show that pSi promoted the appearance of lateral filopodia protruding from the DPSC cell body and not only in the lamellipodia area. The formation of elongated lateral actin filaments suggests that pores provided the necessary anchorage points for protrusion growth. Although MCF-7 cells displayed a lower presence of organized actin network on both pSi and nonporous silicon, pSi stimulated the formation of extended cell protrusions.

Further development of biomaterials is expected as advanced therapeutic products must be compliant to good manufacturing practice regulations. A spraying method for building-up polyelectrolyte films followed by the deposition of dental pulp cells by spraying is presented. Physical treatments of UV irradiation and a drying/ wetting process are applied to the system. Structural changes and elasticity modifications of the obtained coatings are revealed by atomic force microscopy and by Raman spectroscopy. This procedure results in thicker, rougher and stiffer film. The initially ordered structure composed of mainly a helices is transformed into random/b-structures. The treat- ment enhanced dental pulp cell adhesion and proliferation, suggesting that this system is prom- ising for medical applications.

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.