Colette Cazeneuve

Drug Delivery to the Skin From Sub-micron Polymeric Particle Formulations: Influence of Particle Size and Polymer Hydrophobicity

PurposeTo investigate the influence of particle size and polymer properties on the topical delivery of a lipophilic “active” species (Nile Red (NR)) from sub-micron polymeric particles.MethodsThree poly-(ε-caprolactone) (CAPA) formulations were examined to assess the impact of particle size. Three other formulations, based on cellulose acetate butyrate (CAB), CAPA and polystyrene were studied to address the role of polymer hydrophobicity. In vitro skin permeation, and confocal microscopy and stratum corneum (SC) tape-stripping were used to evaluate the cutaneous disposition of NR.ResultsNR delivery into the SC was greater from the larger particles, the overall smaller surface area of which enhanced the “leaving tendency” of the lipophilic “active”. Skin uptake of NR (measured as “%payload released”) from polystyrene, CAPA and CAB particles increased with decreasing polymer hydrophobicity (polystyrene > CAPA > CAB) as expected. Confocal microscopy revealed that NR released from the particles accumulated in, and penetrated via, lipid domains between the SC corneocytes. The particles showed affinity for hairs, and concentrated on the skin surface at the follicular openings.ConclusionsDelivery of a model drug to the skin from sub-micron polymeric particle formulations is sensitive to the particle size and the relative hydrophobicity of the carrier.

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. In this work, special attention is paid to the systems combining polycations and negatively charged surfactants. The paper introduces the hair surface and presents a comprehensive review of the adsorption properties of these systems at solid-water interfaces mimicking the negative charge and surface energy of hair. These model surfaces include mixtures of thiols that confer various charge densities to the surface. The kinetics and factors that govern the adsorption are discussed from the angle of those used in shampoos and conditioners developed by the cosmetic industry. Finally, systems able to adsorb onto negatively charged surfaces regardless of the anionic character are presented, opening new ways of depositing conditioning polymers onto keratin substrates such as hair.

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. The total adsorbed amount depends on the charge density of the surface for both types of polymers. The comparison of the adsorbed mass on each layer obtained from D-QCM and from ellipsometry has allowed calculating the water content of the layers that reaches high values for the polymers studied. The analysis of D-QCM results also provided information about the shear modulus of the layers, whose values have been found to be typical of a rubber-like polymer system. The main driving force of the adsorption was found to be the energy of the interactions between chains and surface.

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). The role of the molecular architecture of the constituents of the PEs are often overruled, or at least and either, underestimated in regard to the surface properties. In this work, we aim to evaluate the effect of a model biomimetic surface that shares the key characteristics of the extreme surface of hair and its concomitant chemo- and physisorbed properties onto the deposition of a complex PEs:SU system. To tackle out the effect of the molecular architecture of the PEs, we consider (i) a purely linear and hydrophilic PE (P100) and (ii) a PE with lateral amphiphilic chains (PegPE). Using numerical self-consistent field calculations, we show that the architecture of the constituents interfere with the surface properties in a nonintuitive way such that, depending on the amphiphilicity and hydrophilicity of the PEs and the hydrophobicity of the surface, a re-entrant adsorbing transition can be observed, the lipid coverage of the model hair surface being the unique control parameter. Such a behavior is rationalized by the anticooperative associative properties of the coacervate micelles in solution, which is also controlled by the architecture of the PEs and SU. We now expect that PEs adsorption, as a rule, is governed by the molecular details of the species in solution as well as the surface specificities. We emphasize that molecular realistic modeling is essential to rationalize and optimize the adsorption process of, for example, polymer conditioning agents in water-rinsed cosmetic or textile applications.