More effective exploitation of the approach, however, should be based on a better understanding of the variables controlling translocation of NPs through the aqueous MN-created channels, particularly PLX 4720 those involved in in-skin drug release and the concentration gradient-driven diffusion of the released encapsulated species across hydrophilic, viable skin layers [20]. Confocal laser scanning microscopy (CLSM) indicated that penetration and distribution of fluorescent polymeric NPs into MN-treated skin are confined to the hair follicles and MN-created channels in a size and concentration-dependent manner, with significantly denser localization in the epidermis compared to the dermis [21] and [22]. However, transdermal

delivery of polymer NPs across MN-treated skin has been a matter of controversy. While polystyrene NPs applied to a MN-treated human epidermal membrane reached receptor solutions in permeation experiments [23] and [24], poly lactic-co-glycolic (PLGA) NPs could not permeate full thickness human abdominal skin [22], murine [21], or porcine ear skin [10]. In a recent study [10], we related MN characteristics and application variables to the in vitro skin permeation of a nanoencapsulated medium-size dye, Rh B, across MN-treated full thickness porcine

skin. In the present study, more insight into the mechanism of MN-driven skin permeation of nanoencapsulated dyes as model drugs was sought. HA-1077 purchase The contribution of the carrier and encapsulated dye characteristics to MN-mediated skin permeation was investigated using PLGA NPs with different physicochemical attributes and Rh B and fluorescein isothiocyanate (FITC) as model hydrophilic and hydrophobic molecules,

respectively [25]. Both dyes are easily determined spectrofluorometrically [26] and have been widely used in fluorescence-based imaging applications [19], [27] and [28]. Further, the two dyes Fossariinae were used in an earlier report [25] to examine possible correlation of molecular characteristics with passive diffusion and MN-mediated permeation through full thickness porcine skin. Poly lactic-co-glycolic acid (PLGA), Resomer RG 503 H (50:50) (MW 24,000–38,000 Da), and Resomer RG 753 S (75:25) (MW 36,610 Da) both of inherent viscosity of 0.32–0.44 dl/g in 0.1% in chloroform at 25 °C and Polylactic acid (PLA) Resomer R 203 H (MW 18,000–28,000 Da) of inherent viscosity 0.25–0.35 dl/g were purchased from Boehringer Ingelheim (Ingelheim, Germany). Rhodamine B (Rh B, MW 479.02 Da), fluorescein isothiocyanate (FITC, MW 389.38 Da), Didodecyldimethyl ammonium bromide (DMAB), Polyvinyl alcohol (PVA, MW 30–70 kDa), and phosphate buffer saline (PBS) tablets (pH 7.4) were obtained from Sigma–Aldrich (St. Louis, MO, USA). Ethyl acetate, AR grade (Fisher Scientific UK Ltd., Loughborough, UK), Nanovan®, methylamine vanadate stain (Nanoprobes®, Nanophank, NY, USA) “Silver dag” – a colloidal silver preparation – (Polysciences Inc.