Nanoparticulate Gels for Cutaneous Administration of Caffeic Acid

Abstract

Caffeic acid is a natural antioxidant, largely distributed in plant tissues and food sources, possessing anti-inflammatory, antimicrobial, and anticarcinogenic properties. The object of this investigation was the development of a formulation for caffeic acid cutaneous administration. To this aim, caffeic acid has been loaded in solid lipid nanoparticles by hot homogenization and ultrasonication, obtaining aqueous dispersions with high drug encapsulation efficiency and 200 nm mean dimension, as assessed by photon correlation spectroscopy. With the aim to improve the consistence of the aqueous nanodispersions, different types of polymers have been considered. Particularly, poloxamer 407 and hyaluronic acid gels containing caffeic acid have been produced and characterized by X-ray and rheological analyses. A Franz cell study enabled to select poloxamer 407, being able to better control caffeic acid diffusion. Thus, a nanoparticulate gel has been produced by addition of poloxamer 407 to nanoparticle dispersions. Notably, caffeic acid diffusion from nanoparticulate gel was eight-fold slower with respect to the aqueous solution. In addition, the spreadability of nanoparticulate gel was suitable for cutaneous administration. Finally, the antioxidant effect of caffeic acid loaded in nanoparticulate gel has been demonstrated by ex-vivo evaluation on human skin explants exposed to cigarette smoke, suggesting a protective role exerted by the nanoparticles.

Keywords: caffeic acid; cigarette smoke; poloxamer; small angle X-ray scattering; solid lipid nanoparticles.

Figure 1

Cryogenic Transmission Electron Microscopy (Cryo-TEM) images of drug loaded solid lipid nanoparticles (SLN-CA) (a) and of SLN-P-CA (b,c).

Figure 2

X-ray scattering profile for SLN (blue) and SLN-CA (red) samples. The SLN sample has been measured only up to Q = 3.5 nm⁻¹, so that the third order is not observable. Experiments were performed at Diamond Light Source (UK).

Figure 3

Small angle X-ray scattering (SAXS) diffraction profiles of P (a); P-CA (b); P-HA (c); and P-HA-CA (d) at 20 (blue), 30 (light blue), and 37 (red) °C. The dashed line indicates the position of the first correlation peak. Experiments were performed in Graz (AT) laboratory.

Figure 4

Data fitting for P-CA SAXS curve at 30 °C.

Figure 5

Temperature effect on elastic (G’, blue) and viscous (G”, orange) moduli for P (a); P-CA (b); P-HA (c); and P-HA-CA (d).

Figure 6

CA diffusion kinetics from Sol-CA (light blue), P-HA-CA (green), P-CA (blue), SLN-CA (black), and SLN-P-CA (red), as determined by Franz cell. Data are the mean of 6 independent experiments.

Figure 7

X-ray scattering profiles for P-CA (red) and SLN-P-CA (light blue) samples measured at 37 °C. The dashed line indicates the position of the gel first correlation peak; the arrow points the position of the first Bragg peak related to the inner organization of the SLN. Experiments were performed at Diamond Light Source (UK).

Figure 8

Temperature effect on elastic (G’, blue) and viscous (G”, orange) moduli for P-P188-CA (a), SLN-CA (b), and SLN-P-CA (c).

Figure 9

Representative images of immunohistochemical analysis for 4-HNE (green) and DAPI (blue) in ex vivo human skin biopsies at 40× magnification. Immunofluorescence on human skin explants (HSE) was determined instantly and 6 h after exposure of CS for 30 min (panel a). Quantification of immunofluorescence signal by using ImageJ software (panel b). Data are the average of three experiments. **** p ≤ 0.0001 vs control (CTRL) Air at the same timepoint.

Figure 10

Expression of heme-oxygenase (HO-1) protein levels on HSE exposed to air or CS for 30 min and pre-treated with SLN-P-CA. Samples were collected after 24 h from exposure. Western blot analysis of HO-1 protein expression is representative of three experiments and β-actin was considered as control (panel a). Quantification of HO-1 expression bands as a ratio of β-actin (panel b). **** p ≤ 0.0001 with respect to control (CTRL) Air.