Topical systems for the controlled release of antineoplastic Drugs: Oxidized Alginate-Gelatin Hydrogel/Unilamellar vesicles.

The efficacy of chemotherapeutic procedures relies on delivering proper concentrations of anti-cancer drugs in the tumor surroundings, so as to prevent potential side effects on healthy tissues. Novel drug carrier platforms should not just be able to deliver anticancer molecules, but also allow for adjustements in the way these drugs are administered to the patients. We developed a system for delivering water-insoluble drugs, based on the use of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), or bis(2-ethylhexyl) sulfosuccinate benzyl-n-hexadecyldimethylammonium (BHD-AOT), embedded into oxidized alginate-gelatin (ADA/Gel) hydrogel, emulating a patch for topic applications. After being loaded with curcumin, cancer cells such as human colorectal adenocarcinoma (HCT116 and DLD-1) and melanoma cell lines (MEL501), and non-malignant cells such as mammary epithelial cell lines (NMuMG) and embryonal fibroblasts (NIH 3T3 or NEO cells) were analyzed for biocompatibility and cytotoxic effects. The results show that the proposed system can load comparatively higher concentrations of the drug (with respect to other nano/microcarriers in the literature), and that it can enhance the likelihood of the drug being uptaken by cancer cells instead of non-malignant cells. These assays were complemented by diffusion studies across the stratum corneum of rat skin, with the aim of determining the system's efficiency during topical application. Finally, the stability of the patch was tested after lyophilization to determine its potential pharmaceutical use. As a whole, the combined system represents a highly reliable and robust method for embedding and delivering complex insoluble chemotherapeutical molecules, and it is less invasive than other alternative methods in the literature.

Electrochemical and photophysical behavior of 1-naphthol in benzyl-n-hexadecyldimethylammonium 1,4-bis(2-ethylhexyl)sulfosuccinate large unilamellar vesicles.

In the present contribution, 1-naphthol is investigated in large unilamellar vesicles formed from a new catanionic surfactant, benzyl-n-hexadecyldimethylammonium 1,4-bis(2-ethylhexyl)sulfosuccinate, by electrochemical and spectroscopic techniques. The electrochemical results show that 1-naphthol experiences a partition process between the water phase and the large unilamellar vesicle bilayer phase, which is corroborated by absorption spectroscopic studies at pH = 6.40 and pH = 10.75. Interestingly, studies of 1-naphthol emission in benzyl-n-hexadecyldimethylammonium 1,4-bis(2-ethylhexyl)sulfosuccinate large unilamellar vesicles at pH = 10.75 and in sodium 1,4-bis(2-ethylhexyl)sulfosuccinate water solution show that when the 1,4-bis(2-ethylhexyl)sulfosuccinate moiety is part of the bilayer, the 1,4-bis(2-ethylhexyl)sulfosuccinate polar head interacts strongly with 1-naphthol, by favoring emission from the excited neutral species resulting in the appearance of a new band close to λ = 355 nm. It seems that the large unilamellar vesicle bilayer of the catanionic vesicle slows down the proton transfer process observed in water, where only emission from 1-naphtholate is detected.

On the characterization of NaDEHP/n-heptane nonaqueous reverse micelles: the effect of the polar solvent.

The behavior of two polar solvents, ethylene glycol (EG) and dimethylformamide (DMF), entrapped in sodium bis-(2-ethylhexyl) phosphate (NaDEHP)/n-heptane reverse micelles (RMs) was investigated using dynamic light scattering (DLS), molecular probe absorption and FT-IR spectroscopy. DLS results reveal the formation of RMs containing EG and DMF as a polar component. To the best of our knowledge this is the first report where both polar solvents are entrapped by the NaDEHP surfactant to effectively create RMs. We use the solvatochromism behavior of the molecular probe, 1-methyl-8-oxyquinolinum betaine (QB), and FT-IR spectroscopy to investigate the physicochemical properties of the non-aqueous RMs. Our results demonstrate that the NaDEHP surfactant interacts through hydrogen bonds with EG at the EG/NaDEHP interface and this interaction is responsible for destroying the bulk structure of pure solvent EG when entrapped in NaDEHP RMs. On the other hand, when DMF is incorporated inside the RMs the bulk structure of DMF is destroyed upon encapsulation by the Na-DMF interaction at the DMF/NaDEHP interface. Our results are completely different than the one observed for DMF/n-heptane/AOT. Our results show how the physicochemical properties, such as micropolarity, microviscosity and hydrogen bond interaction, of nonaqueous NaDEHP/n-heptane RMs interfaces can be dramatically changed by simply using different non-aqueous polar solvents. Thus, these results can be very useful to employ these novel RMs as nanoreactors since the dimensions of the RMs are around 10 to 20 nm.

Distribution of amines in water/AOT/n-hexane reverse micelles: influence of the amine chemical structure.

The distribution of different aliphatic and aromatic amines: n-butylamine (n-BA), isobutylamine (i-BA), tert-butylamine (t-BA), piperidine (PIP), N,N-dimethylaniline (DMA) and N-methylaniline (MA) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate(AOT)/n-hexane reverse micelles was investigated by steady-state fluorescence measurements. The partition constants were measured by an indirect method based on the effect that amine partitioning exert on the bimolecular rate of the reaction between a microphase incorporated fluorophore (Ru(bpy)2+(3)) and the quencher, (Fe(CN)3-(6)). For MA, that can act as a quencher of the fluorophore a direct method was used. The results show that primary amines have larger partition constants than the secondary ones. For tertiary amines the distribution constants were practically negligible. Laser flash photolysis experiments confirmed that tertiary amines, both aliphatic and aromatic, are not incorporated to the micellar pseudophase. The effect of the amine structure on the partition constant was analyzed through linear solvation free energy relationships (LSER) using solute parameters and compared with those obtained for alcohols. Hydrogen bond interactions with the AOT polar heads appear to be the main driving force for the distribution of amines between the organic and micellar pseudophases, whereas the size of the alkyl or aromatic group tends to hinder it.