The use of nanoencapsulation to decrease human skin irritation caused by capsaicinoids

Renata V Contri,1 Luiza A Frank,2 Moacir Kaiser,1 Adriana R Pohlmann,1,3 Silvia S Guterres1,2 1Programa de Pós-Graduação em Ciências Farmacêuticas, 2Faculdade de Farmácia, 3Instituto de Química, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil Abstract: Capsaicin, a topical analgesic used in the treatment of chronic pain, has irritant properties that frequently interrupt its use. In this work, the effect of nanoencapsulation of the main capsaicinoids (capsaicin and dihydrocapsaicin) on skin irritation was tested in humans. Skin tolerance of a novel vehicle composed of chitosan hydrogel containing nonloaded nanocapsules (CH-NC) was also evaluated. The chitosan hydrogel containing nanoencapsulated capsaicinoids (CH-NC-CP) did not cause skin irritation, as measured by an erythema probe and on a visual scale, while a formulation containing free capsaicinoids (chitosan gel with hydroalcoholic solution [CH-ET-CP]) and a commercially available capsaicinoids formulation caused skin irritation. Thirty-one percent of volunteers reported slight irritation one hour after application of CH-NC-CP, while moderate (46% [CH-ET-CP] and 23% [commercial product]) and severe (8% [CH-ET-CP] and 69% [commercial product]) irritation were described for the formulations containing free capsaicinoids. When CH-NC was applied to the skin, erythema was not observed and only 8% of volunteers felt slight irritation, which demonstrates the utility of the novel vehicle. A complementary in vitro skin permeation study showed that permeation of capsaicinoids through an epidermal human membrane was reduced but not prevented by nanoencapsulation. Keywords: chitosan, nanocapsules, capsaicinoids, skin irritation, skin permeatio

Labeling the oily core of nanocapsules and lipid-core nanocapsules with a triglyceride conjugated to a fluorescent dye as a strategy to particle tracking in biological studies

The synthesis of novel fluorescent materials represents a very important step to obtain labeled nanoformulations in order to evaluate their biological behavior. The strategy of conjugating a fluorescent dye with triacylglycerol allows that either particles differing regarding supramolecular structure, i.e., nanoemulsions, nanocapsules, lipid-core nanocapsules, or surface charge, i.e., cationic nanocapsules and anionic nanocapsules, can be tracked using the same labeled material. In this way, a rhodamine B-conjugated triglyceride was obtained to prepare fluorescent polymeric nanocapsules. Different formulations were obtained, nanocapsules (NC) or lipid-core nanocapsules (LNC), using the labeled oil and Eudragit RS100, Eudragit S100, or poly(caprolactone) (PCL), respectively. The rhodamine B was coupled with the ricinolein by activating the carboxylic function using a carbodiimide derivative. Thin layer chromatography, proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), UV-vis, and fluorescence spectroscopy were used to identify the new product. Fluorescent nanocapsule aqueous suspensions were prepared by the solvent displacement method. Their pH values were 4.6 (NC-RS100), 3.5 (NC-S100), and 5.0 (LNC-PCL). The volume-weighted mean diameter (D₄.₃) and polydispersity values were 150 nm and 1.05 (NC-RS100), 350 nm and 2.28 (NC-S100), and 270 nm and 1.67 (LNC-PCL). The mean diameters determined by photon correlation spectroscopy (PCS) (z-average) were around 200 nm. The zeta potential values were +5.85 mV (NC-RS100), −21.12 mV (NC-S100), and −19.25 mV (LNC-PCL). The wavelengths of maximum fluorescence emission were 567 nm (NC-RS100 and LNC-PCL) and 574 nm (NC-S100). Fluorescence microscopy was used to evaluate the cell uptake (human macrophage cell line) of the fluorescent nanocapsules in order to show the applicability of the approach. When the cells were treated with the fluorescent nanocapsules, red emission was detected around the cell nucleus. We demonstrated that the rhodamine B-conjugated triglyceride is a promising new material to obtain versatile dye-labeled nanocarriers presenting different chemical nature in their surfaces

Mitochondrial apoptosis is induced by Alkoxy phenyl-1-propanone derivatives through PP2A-mediated dephosphorylation of Bad and Foxo3A in CLL

Protein phosphatase 2 A (PP2A) is a tumour suppressor whose strong inhibition underlies the phosphorylation-dependent, anti-apoptotic mechanisms in Chronic Lymphocytic Leukemia (CLL). Inactivation of PP2A is due to the cooperative action of the phosphorylation of Y307 of its catalytic subunit by the aberrant cytosolic pool of the Src Family Kinase Lyn and the interaction with its protein inhibitor SET, which is overexpressed in CLL. In this study, we developed a library of compounds, the most potent being the one named CC11, which restores PP2A activity by disrupting the PP2A/SET complex, thereby triggering the mitochondrial pathway of apoptosis. This process involves the recruitment of the pro-apoptotic BH3-only proteins Bad and Bim to mitochondria, the former upon direct dephosphorylation and the latter being newly expressed upon dephosphorylation and activation of its transcription factor FoxO3a. These findings highlight that PP2A antagonizes the prosurvival pathways controlled by Akt, which phosphorylates and thereby suppresses a variety of pro-apoptotic factors and tumour suppressors including Bad and FoxO3a. Furthermore, the PP2A-mediated pro-apoptotic effect of CC11 is synergistically potentiated by the abrogation of Lyn's activity. Our results show that CC11 represents a promising lead compound for a new therapeutic rationale aimed at abrogating the aberrant oncogenic signals in CLL