Chitosan-based films containing nanoemulsions of methyl salicylate: Formulation development, physical-chemical and in vitro drug release characterization.

Transdermal patches for analgesic purposes are widely used, however, their occlusive characteristics can often cause allergic reactions, irritating contact dermatitis, and allergic contact dermatitis upon extended use. Chitosan is a natural positively charged bioadhesive polysaccharide with several biological properties, being promising templates for sustained and controlled topical or transdermal drug delivery. Methyl salicylate (MS) is a non-steroidal topical anti-inflammatory drug (NSAID). MS is a lipophilic oily drug commonly found in transdermal patches, being difficult to incorporate into hydrophilic formulations such as Chitosan-based films. Thus, MS is a good candidate to be encapsulated into nanoemulsions (NE). This work reports the formulation development, physical-chemical characterization, and in vitro drug release of NE-loaded Chitosan films formulated with MS, as a novel substitute for transdermal analgesic patches. MS was encapsulated into NE, which were prepared by ultrasonication and presented 29.3 nm ± 0.1 and PdI 0.167 ± 0.005. The incorporation of MS into NE prevented phase separation and provided a homogeneous physical blending formulation, as confirmed by FTIR, TGA. NE-loaded films provided high drug incorporation in the films 94.08% ± 6.63%), and a smaller crystallinity degree in comparison with physical mixture films, suggesting a plasticizing effect of nano-sized droplets. Besides, mean weight, thickness, and moisture content were increased in NE-loaded films in comparison with chitosan-based control films. In vitro drug release from NE-loaded films was significantly higher than for physical mixture films, following Weibull and Korsmeyer-Peppas release kinetics models. The results suggest that NE-loaded chitosan film can increase the drug loading capacity of oil drugs and successfully control in vitro release, constituting a novel approach for transdermal drug delivery of NSAIDs.

Understanding Drug Release Data through Thermodynamic Analysis.

Understanding the factors that can modify the drug release profile of a drug from a Drug-Delivery-System (DDS) is a mandatory step to determine the effectiveness of new therapies. The aim of this study was to assess the Amphotericin-B (AmB) kinetic release profiles from polymeric systems with different compositions and geometries and to correlate these profiles with the thermodynamic parameters through mathematical modeling. Film casting and electrospinning techniques were used to compare behavior of films and fibers, respectively. Release profiles from the DDSs were performed, and the mathematical modeling of the data was carried out. Activation energy, enthalpy, entropy and Gibbs free energy of the drug release process were determined. AmB release profiles showed that the relationship to overcome the enthalpic barrier was PVA-fiber > PVA-film > PLA-fiber > PLA-film. Drug release kinetics from the fibers and the films were better fitted on the Peppas-Sahlin and Higuchi models, respectively. The thermodynamic parameters corroborate these findings, revealing that the AmB release from the evaluated systems was an endothermic and non-spontaneous process. Thermodynamic parameters can be used to explain the drug kinetic release profiles. Such an approach is of utmost importance for DDS containing insoluble compounds, such as AmB, which is associated with an erratic bioavailability.

Structural and thermal analyses of zinc and lactose in homeopathic triturated systems.

BACKGROUND: A series of different experimental approaches was applied in Zincum metallicum (Zinc met.) samples and lactose controls. Experiments were designed to elucidate the effect of zinc trituration and dynamization on physicochemical properties of homeopathic formulations, using lactose as excipient. METHODS: Zinc met. potencies (Zinc met 1-3c) were triturated and dynamized using lactose as excipient, according to Brazilian Homeopathic Pharmacopoeia. Lactose samples (LAC 1-3c) were also prepared following the same protocol and used as controls. The samples were analyzed structurally by Atomic Absorption Spectroscopy (AAS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) with Energy Dispersive X-ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM), and thermodynamically by Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). RESULTS: AAS analysis detected 97.0 % of zinc in the raw material, 0.75 % (Zinc met 1c) and 0.02% (Zinc met 2c). XRD analysis showed that inter-atomic crystalline spacing of lactose was not modified by dynamization. Amorphous and crystalline lactose spheres and particles, respectively, were observed by TEM in all samples, with mean size from 200 to 800 nm. EDX obtained with TEM identified zinc presence throughout the amorphous matter but individualized zinc particles were not observed. SEM images obtained from dynamized samples (LAC 1c and Zinc met 1c) with electron backscattering could not identify zinc metal grains. The dynamization process induced Derivatives of Thermal Gravimetric (DTg) peak modification, which was previously centered near 158°C to lactose, to a range from 140 to 170°C, suggesting the dynamization process modifies the temperature range of water aggregation. Thermal phenomena were analyzed and visualized by Analysis of Variance (ANOVA) and Principal Component Analysis (PCA) statistics. Both indicated that fusion enthalpy of dynamized samples (DynLAC 1-3c; DynZn 1-3c) increased 30.68 J/g in comparison to non-dynamized lactose (LAC; p < 0.05). CONCLUSIONS: Our results suggested no structural changes due to the trituration and dynamization process. However, TG and DSC analyses permit the differentiation of dynamized and non-dynamized groups, suggesting the dynamization process induced a significant increase in the degradation heat. These results call for further calorimetric studies with other homeopathic dilutions and other methodologies, to better understand the dynamics of these systems.