132 JOURNAL OF COSMETIC SCIENCE
PHYSICAL STABILITY
The physical stability of the selected formulation was evaluated in a Turbiscan Lab Expert
analyzer (Formulation Inc., Toulouse, France). The detection head was composed of a pulsed
near-infrared light source (k =850 nm) and transmission and backscattering detectors.
The NLC sample was placed in a cylindrical glass tube and scanned throughout the tube
height every 30 minutes continuously for 24 hours at 37°C. The stability of the formulation
was determined through the variation of backscattering of the sample over the monitored
time, using Easysoft© software (Easysoft, Wetherby, United Kingdom).
PHOTOSTABILITY STUDY
Samples of NLC encapsulating AVB, NLC without AVB and of AVB dissolved in ACN
(n =3) were subjected to UVA radiation (3,025 mW/cm²) for 24 hours in a photostability
chamber (424 CF, Nova Ética, Brazil) equipped with a near-UV fluorescent lamp (15 W)
with a spectral distribution from 320–400 nm and several cool white fluorescent lamps
(15 W). The samples collected before irradiation, after 2, 4, 8, and 24 hours of irradiation,
and quantifications of AVB were performed by HPLC.
SKIN RETENTION AND PERMEATION
For the in vitro study of cutaneous retention in pig ear skin, manual vertical Franz-type
static flow cells equipment (Hanson Research, USA) were used under agitation of 300 rpm,
at 37°C and a diffusion area of 1.86 cm2. The receiving compartment contained 6.7 mL
of phosphate-buffered saline (PBS) buffer solution (pH: 7.4) with 5% Tween20, with 1 mL
samples being collected at each time point. The 400 µm skin was positioned between the
two compartments with the stratum corneum facing up. 18.5 µL of the formulation were
applied on the stratum corneum surface to maintain sink conditions (data not shown).
Samples were collected at 2, 4, 6, 8, and 24 hours of permeation and were quantified by
HPLC. The study was conducted under the norms of research involving animals with
protocol CEUA/UFG nr. 105/22.
To evaluate the cutaneous retention of nano encapsulated AVB on the skin surface, the skins
were removed from the compartments after 24 hours of exposure and were washed with 2 mL
of PBS buffer solution (pH: 7.4) containing 5% Tween 20. Next, tape stripping was performed
using adhesive tape to remove the stratum corneum. This procedure was repeated 15 times on
each skin, and then the strips were added in 15 mL tube with 5 mL of ACN, homogenized
for 2 minutes in a vortex, transferred to the ultrasound bath for 20 minutes, and then filtered
through a PVDF membrane (0.45 µm) for quantification by HPLC. Finally, the remaining
skin was fragmented, diluted in 5 mL of can, and homogenized for 2 minutes in a vortex. The
homogenate was kept under ultrasound for 20 minutes and then filtered (PVDF 0.45 µm).
The assay was performed six times, and all samples were quantified by HPLC.
STATISTICAL ANALYSIS
A student’s t-test was used to compare the sets of data in Graphpad Prism software version 5.0
(Graphpad Prism Inc., Massachusetts USA), and p values 0.05 were considered significant.

133 ImprovedPROVED AVB PhotostabilityOTOSTABILITY UsingING NLCs
RESULTS AND DISCUSSION
AVB QUANTIFICATION
The analytical method was able to elute AVB in 3.5 minutes. The presence of two peaks
was identified (Figure 1), one at 2.2 minutes corresponding to AVB in its keto form, and
the other at 3.4 minutes corresponding to its enol form, as described by Abid et al.24 The
method was linear, with a correlation coefficient r =0.9995, and all points on the curve
presented RPD 5%. Accuracy was in the range of 5% of variation (95–105%). Detection
and quantification limits were 0.0509 and 0.1542 µg/mL, respectively. As for selectivity,
no changes were observed in the peaks obtained from AVB, in relation to the peaks of the
isolated candidate components of the formulations.
AVB SOLUBILITY
AVB showed different solubilities in the liquid lipids: 49.20 ± 2.83 mg/mL−1 in oleic acid,
126.79 ± 7.87 mg/mL−1 in isopropyl myristate, and 124.85 ± 1.95 mg/mL−1 in capric and
caprylic acid triglycerides. AVB solubility in mineral oil and sesame oil was 17.22 ± 6.50 mg/
mL−1 and 45.45 ± 1.57 mg/mL−1, respectively.
THERMAL ANALYSIS (DTA AND TG/DTG)
Figure 2 shows the DTA curves of AVB and the mixture of AVB with lipid-based excipients.
The DTA curve of AVB shows a narrow endothermic peak with T
peak at 86.45°C. The
greatest variations in AVB T
peak (29.67–20.69°C) were observed in the binary mixtures
with Poloxamer 188, glyceryl monostearate, and beeswax. Anticipations of the AVB
Figure 1. Chromatogram of AVB sample obtained by HPLC. Zorbax Eclipse (Agilent) XDB – C18 column
150mm × 4.6 mm, 3.5 µm, with precolumn C18 12.5 × 4.6 mm, 3.5 µm (Agilent), maintained at 30°C. The
mobile phase was composed of ACN and water 90:10, v/v, at a 1 mL/min-1 flow. The injection volume was
10 µL. Sample concentration was 30 µg/mL.1