Penetration and Growth of DPPC/DHPC Bicelles Inside the Stratum Corneum of the Skin

Abstract

The effect of dipalmitoyl phosphatidylcholine (DPPC)/dihexanoyl phosphatidylcholine (DHPC) bicelles on the microstructure of pig stratum corneum (SC) in vitro was evaluated. The physicochemical characterization of these nanoaggregates revealed small disks with diameters around 15 nm and a thickness of 5.4 nm. Upon dilution, the bicelles grow and transform into vesicles. Cryogenic scanning electron microscopy (cryo-SEM) images of the SC pieces treated with this system showed vesicles of about 200 nm and lamellar-like structures in the intercellular lipid areas. These vesicles probably resulted from the growth and molecular rearrangement of the DPPC/DHPC bicelles after penetrating the SC. The presence of lamellar-like structures is ascribed to the interaction of the lipids from bicelles with the SC lipids. The bicellar system used is suitable to penetrate the skin SC and to reinforce the intercellular lipid areas, constituting a promising tool for skin applications.

Bicellar systems as modifiers of skin lipid structure

“…However, it is necessary to consider that the DPPC/DHPC bicelles increase in size, forming large bilayers by a dilution effect. This behavior is similar to that reported in surfactant-lipid micellar systems [17,18] and has been recently reported for DPPC/DHPC bicellar systems [19]. Then, we can assume that small DPPC/DHPC discoidal bicelles are able to pass through the SC layers and by mixing with SC lipids and influenced by SC hydration, large structures are formed.…”

Structural Versatility of Bicellar Systems and Their Possibilities as Colloidal Carriers

“…[32,55]. Applying the form factor squared of the simplified Gaussian model to SAXS a bilayer thickness value (d B = 5.4 nm) was obtained [32,55]. The size distribution curve obtained by DLS shows a HD value of 11.3 nm and a PI of 0.072.…”

“…In fact, the interaction of these systems with SC has been reported and although tracking the presence of the bicellar disks in the tissue was not possible, interestingly, vesicles and lamellar-like structures were observed in the lipid intercellular areas of the tissue after treatment with bicellar systems. These structures were probably the result of a structural rearrangement of bicelles inside the cutaneous SC [55]. …”

“…Its versatility, the ability to modulate its structure, organization and their lipid bilayer offer great advantages over other bilayer systems. Besides, some works have demonstrated that these systems are adequate to penetrate the skin and to reinforce the structure lipid system (DPPC / DHPC q = 3.5) or to enhance the permeability of this tissue (DMPC / DHPC q = 2) [47,55,87]. …”

Effect of Low Concentration of DHPC on the DPPC/Sm Bilayer

“…In the last two decades, bicellar systems have become a useful membrane mimetic since it provides an oriented media for the study of molecules with biological interest, using solid [6][7][8][9] and solution NMR 10,11 . Bicellar systems are formed from mixtures of the dihexanoylphosphatidylcholine (DHPC) and dimiristoylphosphatidylcholine (DMPC) 4,12 and occasionally, dipalmitoylphatidylcholine (DPPC) [13][14][15] . On the other hand, it has been reported that adding a third lipid, with propensity to form a non-lamellar phase, to the DPPC/SM mixture, increases the permeation of cytolitic proteins 16 .…”