Increased therapeutic efficacy of a newly synthesized tyrosinase inhibitor by solid lipid nanoparticles in the topical treatment of hyperpigmentation

Figures & data

Table 1 Physicochemical characterization of MHY-SLNs

Formulation	Yield (%)	DL (wt %)	EE (%)	Size (nm)	Zeta potential (mV)	PDI
MHY-SLNs	88.5±1.7	3.4±0.4	77.6±4.7	207±39	−29.8±1.2	0.269

Note: Values are presented as the mean ± SD (n=3).

Abbreviations: DL, drug loading; EE, encapsulation efficiency; MHY-SLNs, MHY498-loaded solid lipid nanoparticles; PDI, polydispersity index; SD, standard deviation.

Figure 1 In vitro characterization of MHY-SLNs.

Notes: Transmission electron microscopy images (A), particle size distribution (B), X-ray diffraction analysis diffractograms (C) and differential scanning calorimetry thermograms (D) of MHY498, Compritol, and MHY-SLNs.
Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; endo, endothermic.

Figure 2 In vitro release profile of MHY498-loaded solid lipid nanoparticles. Notes: A drug-release study was performed using the dialysis bag-diffusion technique. Results are presented as the mean ± SD (n=3).

Abbreviation: SD, standard deviation.

Table 2 Flux determination of MHY-SLNs and MHY solution at different time intervals

Formulation	Flux (J) (µg/cm^2⋅h)
	12 h	24 h	48 h
MHY-SLNs	5.7±1.1	4.1±0.4	3.3±0.6
MHY solution	1.7±0.5	1.8±0.3	1.8±0.1

Note: Values are presented as the mean ± SD (n=3).

Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; SD, standard deviation.

Figure 3 In vitro skin permeation of MHY solution and MHY-SLNs.

Notes: In vitro skin permeability was evaluated using C57BL/6 mouse dorsal skin. Results are presented as the mean ± SD (n=3).
Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; SD, standard deviation.

Figure 4 Proposed permeation mechanism of MHY498 from MHY-SLNs matrix through loose corneocyte packing of stratum corneum after skin application.

Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; UVB, ultraviolet B.

Figure 5 In vivo evaluation of MHY-SLNs.

Notes: (A) Qualitative skin-brightness comparison based on daily changes in skin brightness observed with the UV control, MHY solution, and MHY-SLNs groups. (B) Quantitative skin-brightness comparison based on reflective colorimetric measurements of skin darkening with the UV control, MHY solution, and MHY-SLNs groups. The values are presented as the mean ± SD (n=6). ***P<0.001 for MHY-SLNs and MHY solution group, and **P<0.01 for Blank-SLNs group when compared with the UV control group.
Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; SD, standard deviation; UV control, ultraviolet control.

Figure 6 Fontana–Masson-stained sections of C57BL/6 skin from the UV control, MHY solution, and MHY-SLNs groups.

Notes: Black pigments indicated by the arrows signify melanin in the epidermis. All images were taken at 20× magnification.
Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; UV control, ultraviolet control.

Figure 7 In vitro cytotoxicity study of MHY-SLNs and MHY solution.

Notes: The L929 mouse fibroblast cell line was used to evaluate skin cytotoxicity. The data shown represent the mean ± SD (n=4).
Abbreviations: MHY-SLNs, MHY498-loaded solid lipid nanoparticles; SD, standard deviation.