Spectral histology of hair and hair follicle using infrared microspectroscopy.

Objective: Today, there is only limited knowledge of the spatial organization of hair chemistry. Infrared microspectroscopy is a well-established tool to provide such information and has significantly contributed to this field. In this study, we present new results combining multiple infrared microspectroscopy methods at different length scales to create a better chemical histology of human hair, including the hair follicle, hair shaft, hair medulla and hair cuticle.

Discrete Nanoscale Distribution of Hair Lipids Fails to Provide Humidity Resistance.

The subcellular distribution of lipids in human hair was investigated to better understand their role in water permeability. Unlike where lipids are organized under a precisely ordered continuous structure, the removal of free lipids in hair does not lead to an increase of water permeability. Esterified and CH-enriched molecules were tracked at a 10 nm resolution by infrared nanospectroscopy (atomic force microscopy coupled to infrared spectroscopy, AFMIR).

Turning autophobic wetting on biomimetic surfaces into complete wetting by wetting additives.

Autophobicity or pseudo partial wetting, a phenomenon of a liquid not spreading on its own monolayer, is characterized by an energy barrier that prevents the growth of a wetting film beyond the monolayer thickness. Applying a molecularly detailed self-consistent field theory we illustrate how autophobic wetting can be overcome by wetting additives. More specifically we use an emulsifier which keeps the interfacial tension between the wetting component and the majority solvent low, and a co-solvent additive which partitions inside the film and then destroys the molecular order in it so that the barrier for film growth is cleared.

Modeling of Polyelectrolyte Adsorption from Micellar Solutions onto Biomimetic Substrates.

Depositing cationic polyelectrolytes (PEs) from micellar solutions that include surfactants (SU) onto surfaces is a rich, complex, highly relevant, and challenging topic that covers a broad field of practical applications (e.g., from industrial to personal care).

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber.

The complex mechanical properties of biomaterials such as hair, horn, skin, or bone are determined by the architecture of the underlying fibrous bionetworks. Although much is known about the influence of the cytoskeleton on the mechanics of isolated cells, this has been less studied in tridimensional tissues. We used the hair follicle as a model to link changes in the keratin network composition and architecture to the mechanical properties of the nascent hair.

Distribution and localization of hydrophobic and ionic chemical groups at the surface of bleached human hair fibers.

A chemical mapping with high lateral resolution using an atomic force microscope in the pulsed force mode with chemically modified tips, introduced as "dynamic chemical force microscopy" (dCFM), was carried out to investigate the chemical properties of the cuticle of human hair and its changes following an oxidative treatment. Chemically modified atomic force microscopy (AFM) tips, CH3- and NH2-terminated, were applied to achieve a defined chemical contrast (hydrophobic and ionic) in aqueous medium. A comparative Fourier transform infrared spectroscopy-attenuated total reflection identified the dominant chemical groups of the surface vicinity of the hair fiber resulting from the bleaching process.

Localization of human hair structural lipids using nanoscale infrared spectroscopy and imaging.

Atomic force microscopy (AFM) and infrared (IR) spectroscopy have been combined in a single instrument (AFM-IR) capable of producing IR spectra and absorption images at a sub-micrometer spatial resolution. This new device enables human hair to be spectroscopically characterized at levels not previously possible. In particular, it was possible to determine the location of structural lipids in the cuticle and cortex of hair.

Adsorption of polyelectrolytes and polyelectrolytes-surfactant mixtures at surfaces: a physico-chemical approach to a cosmetic challenge.

The use of polymer and polymer - surfactant mixtures for designing and developing textile and personal care cosmetic formulations is associated with various physico-chemical aspects, e.g. detergency and conditioning in the case of hair or wool, that determine their correct performances in preserving and improving the appearance and properties of the surface where they are applied.

Adsorption of conditioning polymers on solid substrates with different charge density.

The adsorption processes of polymers that belong to two different families (neutral hydrophilic polymers and cationic polysaccharide polymers) onto solid surfaces with different charge density have been studied using dissipative quartz crystal microbalance (D-QCM) and ellipsometry. The polymers studied are very frequently used in the cosmetic industry as conditioning agents. The adsorption kinetics of the polymers involves at least two steps.

Detection of corneodesmosin on the surface of stratum corneum using atomic force microscopy.

Corneodesmosin, a protein known to be present in the stratum corneum (SC), plays an important role in its physical integrity. Here, a specific antibody to corneodesmosin was tethered via a flexible linker to an atomic force microscopy tip, and the interaction forces between this tip and the surface of the SC were successfully measured. Using the recently developed technique of simultaneous topography and recognition imaging, we were able to map the distribution of corneodesmosin on the surface of the SC at the nanoscale.