Formulation and evaluation of novel glycyrrhizic acid micelles for transdermal delivery of podophyllotoxin

Figures & data

Figure 1. Structure diagram of glycyrrhizic acid.

Figure 2. The HPLC graphs of POD standard (A), POD-loaded GA micelles formulation (B), the sample from the in vitro skin permeation study (C), and the sample from skin deposition study (D).

Figure 3. (A) Phase-solubility diagram of the POD solution at different ethanol–water ratios (0%, 10%, 20%, 25%, 30%, 35%, and 40%); (B) influence of the GA/POD ratios and ethanol contents (0%, 15%, 20%, 25%, and 30%) on the solubility of POD. (C) Influence of different GA/POD ratios on the encapsulation efficiency of POD as the ethanol content was set at 25% (v/v); Data are expressed as the mean ± SD (n = 3).

Figure 4. DSC thermograms of the pure POD, pure GA, POD, and GA physical complexes and POD-loaded GA micelles.

Figure 5. The CMC of GA in the ethanol–water solution in contents of zero percent (A), 15% (B), 25% (C), 35% (D), and 55% (E); Change of the CMC in different ethanol levels (F).

Figure 6. Dynamic light scattering results of the POD-loaded GA micelles (A) and blank micelles (B); TEM images of the POD-loaded GA micelles preparation (×20 k and ×50 k) (C).

Table 1. The characteristic parameters of the POD-loaded GA micelles.

Time (month)	Particle Size (nm)	Polydispersity Index (PDI)	Conc. (mg/mL)	EE (%)	DL (%)
0	10.06 ± 0.01	0.368 ± 0.0012	5.044 ± 0.30	78.53 ± 2.17	7.293 ± 0.42
1	10.08 ± 0.01	0.370 ± 0.0014	5.073 ± 0.12	77.25 ± 1.37	7.270 ± 0.16
3	10.83 ± 0.03	0.249 ± 0.0012	5.096 ± 0.33	77.14 ± 0.87	7.250 ± 0.26

Values represent the mean ± SD (n = 3).

Figure 7. (A) In vitro skin permeation studies of the skin applied with POD tincture, POD-loaded GA micelles preparation, and POD tincture (included GA). The POD concentration of these samples was 5 mg/mL (n = 5); (B) In vitro release profiles of the POD-loaded GA micelles in PBS at 37 ± 0.5 °C (n = 3); (C) In vivo drug-deposition studies of the skin applied with the POD-loaded GA micelles preparation (5 mg/mL) and the POD tincture of different drug concentrations (1, 3, and 5 mg/mL); fluorescent images of the rat skin treated with the GA solution (D), POD tincture (E), and POD-loaded GA micelles preparation (F).

Table 2. The in vitro skin permeation study.

Parameter	POD tincture	POD-loaded GA micelles	POD tincture (include GA)
Jss (μg/cm^2/h)	0.4327 ± 0.036	0.3458 ± 0.023	0.1716 ± 0.019
Tlag (h)	1.251	2.06	0.836
Zero order, R^2	0.9793	0.9868	0.9947
First order, R^2	0.9507	0.9642	0.9886
Higuchi, R^2	0.9634	0.9493	0.9692

All data are shown as the means ± SD (n = 5).

Table 3. The amount of drug deposited in skin (μg/cm²).

	POD tincture (mg/mL)
Time (h)	1	3	5	POD-loaded GA micelles
2	7.469 ± 0.56	14.49 ± 1.14	23.84 ± 0.15	13.70 ± 0.57
4	12.65 ± 0.57	18.66 ± 1.89	83.10 ± 2.42	20.78 ± 0.51
8	5.179 ± 0.42	13.12 ± 2.41	61.76 ± 3.33	23.76 ± 0.44
12	3.593 ± 0.67	8.930 ± 0.53	20.07 ± 1.02	24.37 ± 0.97

Values represent the mean ± SD (n = 3).

Figure 8. HE-staining graphs showing the histological changes of the skin; the immunohistochemical photograph showing the difference between the skin groups treated with physiological saline, 75% ethanol, POD tincture, and POD-loaded GA micelles formulation (magnification,  ×200).