Unbinding Process of Amelogenin and Fibrinogen Adsorbed on Different Solid Surfaces Using AFM

The interaction of proteins with solid surfaces is a fundamental phenomenon in the biomaterials field. We investigated, using atomic force microscopy (AFM), the interactions of a recombinant amelogenin with titanium, a biphasic calcium phosphate (BCP) and mica. The unbinding processes were compared to those of an earlier studied protein, namely fibrinogen. Force spectroscopy (AFM) experiments were carried out at 0 ms, 102 ms, 103 ms and 104 ms of contact time. In general, the rupture forces increased as a function of interaction time. The unbinding forces of amelogenin interacting with the BCP surface were always stronger than those of the amelogenin-titanium system. The unbinding forces of fibrinogen interacting with the BCP surface were always much stronger than those of the fibrinogen-titanium system. For the most part, this study provides direct evidence that recombinant amelogenin binds more strongly than fibrinogen on the studied substrates.

How Polydopamine Modulates Biological Responses to PTFE Prostheses

Diaphragm repair after congenital diaphragmatic hernia is associated with hernia recurrence due to prosthesis failure. Expanded polytetrafluoroethylene (e-PTFE), a synthetic non-degradable biomaterial, is currently used for those diaphragmatic defect repairs. The drawback of e-PTFE is its poor wettability that leads to coating difficulties, bonding that could favor implant integration. However, polydopamine (PDA) can be deposited as well on organic as on inorganic substrates. Therefore, we assessed the biological responses of a clinically used e-PTFE biomaterial treated with PDA in two different manners: one impregnated with PDA and the other coated with a one side PDA film. Mechanical properties of the raw e-PTFE, the PDA soaked biomaterial and the PDA coated surface were characterized by colloidal probe atomic force microscopy. Behaviors of primary human fibroblasts and Wharton’s jelly stem cells were investigated by electron microscopy. Findings reveal that the mechanical properties at the microscopic scale are not modified by the PDA treatments. Cells spread onto both PDA functionalized substrates. In addition, microscopic observations disclose numerous focal cell contacts, evidencing cell attachment, and cytoplasmic projections particularly with the nanoscale PDA coating. Results clearly suggest that PDA in general but above all the PDA coating enhance cellular colonization of the implant material.

TEM Assessments of the Restructuring Effects of an Emollient Cream on the <i>stratum corneum</i>

The structure of the stratum corneum contributes to the barrier function of the epidermis. Skin barrier recovery is of utmost importance after epidermal tissue damage. The aim of this study was to describe, at the cellular level, the structural effects resulting from topical application of a hand-cream onto normal skin and to investigate the potential repair mechanisms induced by the emollient on altered tissue. Transmission electron microscopy (TEM) was used to compare the architectures of the horny layers from: 1) ex-vivo cultured human skin;2) skin treated by topical application of a hand-cream emulsion;3) explants exposed to sodium lauryl sulfate (SLS);4) SLS-treated explants that underwent subsequent topical application of the emollient emulsion. These TEM assessments allowed identifying the structural changes occurring in the stratum corneum of skin explants exposed to SLS and/or treated with an emollient. Results strongly suggest that both, SLS-induced damage and emollient-driven repair process take place in the stratum corneum, at the cellular level. One can envisage that the observed restructuring effects after topical application of the skin-care product are likely to ameliorate or restore the barrier function of the stratum corneum. In this, the properties of the emollient go beyond the cosmetic feel.