However, increasing FITC loading (F9–F11) particularly at the 20% w/w level was associated with a marked increase in particle size and PDI and reduced zeta potential. The FITC NPs formulation (F12) prepared using 1% w/v PVA as stabilizer showed a zeta potential of −4.5 and a distinct increase in particle size. Fig. 3 shows TEM images of representative Rh B (F8) and FITC (F9) NPs samples prepared using PLGA 50:50 at 5% w/w dye loading. NPs were spherical in shape with more or less uniform size verifying size data presented see more in Table 1. Data for skin permeation of nanoencapsulated

dyes across MN-treated porcine ear skin, expressed as cumulative amount of dye permeating at 48 h (Q48, μg/cm2) and steady state flux (μg/cm2/h), are presented in Table 2. Several reports provided

evidence for maintenance of the barrier function of porcine skin for up to 48 h [10] and [31]. Further, frequent sampling was essential for the initial part of the study due to the lack of the literature data regarding the permeation of a dye loaded into nanoparticles through MN-treated skin. At the 1% w/v DMAB concentration used throughout the study, NPs had a mean diameter of approximately CAL-101 solubility dmso 100 nm (Table 1) which did not noticeably change in response to homogenization speed (screening data not shown). The higher concentrated 3% w/v DMAB solution had a higher viscosity (20.8 ± 0.0026 cP) as measured using a cone and plate viscometer (CSL2 whatever 100, TA Instruments, Crawley, UK) compared to that of the

1% w/v solution (3.71 ± 0.0004 cP). It resulted in a measurable increase in particle size that was inversely proportional to the homogenization speed. Thus, NP size was controlled by optimizing emulsion homogenization speed and DMAB concentration (Table 1). The increase in particle size of Rh B-loaded PLGA 50:50 NPs significantly (P < 0.05) reduced Rh B skin permeation ( Fig. 4) despite the PDI values exceeding 0.2. Mean Q48 values of 2.49 ± 0.08, 2.02 ± 0.11 and 0.5 ± 0.20 μg/cm2 and flux values of 3.55 ± 0.09, 2.83 ± 0.19 and 0.81 ± 0.28 μg/cm2/h were obtained for test NPs formulations F1 (155.2 nm), F2 (251.5 nm) and F3 (422.3 nm), respectively. The increase in hydrophilicity of Rh B-loaded PLGA NPs (F4–F6) of more or less similar size (91.9–105.5 nm), achieved by reducing lactide to glycolide ratio, enhanced dye permeation across MN-treated skin (Fig. 5). Data in Table 2 indicated that exposure of skin samples to F4 NPs (PLGA 100:0) resulted in a mean Q48 of 2.07 ± 0.19 μg/cm2 and flux of 2.90 ± 0.27 μg/cm2/h. Reducing the lactide to glycolide ratio to 75:25 (F5) increased Q48 (2.92 ± 1.32 μg/cm2) and the flux (3.98 ± 1.62 μg/cm2/h) yet not significantly (P = 0.379, 0.395, respectively). A further reduction in the lactide content (50:50, F6) caused a significant increase in mean Q48 (5.40 ± 0.39 μg/cm2, P = 0.016) with no significant increase in flux (6.19 ± 0.77 μg/cm2/h, P = 0.072).