Development of New Bexarotene-loaded Mesoporous Silica Systems for Topical Pharmaceutical Formulations.

The present study reports the first time use of MCM-41 mesoporous silica as highly efficient carrier for bexarotene - an antineoplastic agent specific for cutaneous T-cell lymphoma treatment. Bexarotene is highly toxic and poor-water soluble, having low bioavailability in the conventional pharmaceutical forms. Comparative uptake of bexarotene on amino-functionalized silica host at various functionalization degrees is discussed in details taking into account all structural features, of matrix as well as properties of the drug molecules. The obtained results proved a successful bexarotene loading on amino-functionalized MCM-41 silica. The bexarotene molecules are adsorbed on the active centers in non-crystalline state proving the major role of the silica amino-functionalization for the drug solubility and bioavailability enhancing. In vitro dissolution tests showed a prolonged release of bexarotene during 12 h, reaching 50% release of loaded active molecules. The prolonged release has been demonstrated to be a result of the presence of aminopropyl groups on the silica pore walls.

Inhibition of bcl-2 and cox-2 Protein Expression after Local Application of a New Carmustine-Loaded Clinoptilolite-Based Delivery System in a Chemically Induced Skin Cancer Model in Mice.

Our research has focused on in vitro and in vivo evaluations of a new Carmustine (BCNU)-loaded clinoptilolite-based delivery system. Two clinoptilolite ionic forms-hydrogen form (HCLI) and sodium form (NaCLI)-were prepared, allowing a loading degree of about 5-6 mg BCNU/g of zeolite matrix due to the dual porous feature of clinoptilolite. Clinoptilolite-based delivery systems released 35.23% of the load in 12 h for the BCNU@HCLI system and only 10.82% for the BCNU@NaCLI system. The BCNU@HCLI system was chosen to develop gel and cream semisolid dosage forms. The cream (C_BCNU@HCLI) released 29.6% of the loaded BCNU after 12 h in the Nylon synthetic membrane test and 31.6% in the collagen membrane test, higher by comparison to the gel. The new cream was evaluated in vivo in a chemically induced model of skin cancer in mice. Quantitative immunohistochemistry analysis showed stronger inhibition of B-cell lymphoma-2 (bcl-2) and cyclooxygenase 2 (cox-2) protein expression, known markers for cancer survival and aggressiveness, after the treatment with C_BCNU@HCLI by comparison to all the control treatment types, including an off-label magistral formula commercially available Carmustine cream as reference, bringing evidence that a clinoptilolite-based delivery systems could be used as a cancer drug carriers and controlled release systems (skin-targeted topical delivery systems).

Investigations on nanoconfinement of low-molecular antineoplastic agents into biocompatible magnetic matrices for drug targeting.

Magnetic mesoporous silica nanoparticles are employed as biocompatible matrices to host low-molecular antineoplastic drugs. 5-Fluorouracil is a well-known antimetabolite drug used to treat many malignancies: colon, rectal, breast, head and neck, pancreatic, gastric, esophageal, liver and G-U (bladder, penile, vulva, prostate), skin cancers (basal cell and keratosis). Unfortunately severe gastrointestinal, hematological, neural, cardiac and dermatological toxic effects are often registered due to its cytotoxicity. Thus, this work focuses on development of a magnetic silica nanosystem, capable of hosting high amounts of 5-fluorouracil and delivers it in a targeted manner, under the influence of external magnetic field. There are few reports on nanoconfinement of this particular small molecule antimetabolite on mesoporous silica hosts. Therefore we have investigated different ways to confine high amounts of 5-FU within amino-modified and non-modified mesopores of the silica shell, from water and ethanol, under magnetic stirring and ultrasound irradiation. Also, we have studied the adsorption process from water as a function of pH in order to rationalize drug-support interactions. It is shown that nature of the solvent has great influence on diffusion of small molecules into mesopores, which is slower from alcoholic solutions. More importantly, sonication is proven as an excellent alternative to long adsorption tests, since the time necessary to reach equilibrium is drastically reduced to 1h and higher amounts of drug may be immobilized within the mesopores of amino-modified magnetic silica nanoparticles. These results are highly important for optimization of drug immobilization process in order to attain desired release profile.

Magnetic α-Fe2O3/MCM-41 nanocomposites: preparation, characterization, and catalytic activity for methylene blue degradation.

Catalysts based on nanosized magnetic iron oxide stabilized inside the pore system of ordered mesoporous silica MCM-41 have been prepared. The obtained materials were characterized by powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and N(2) adsorption-desorption isotherm. XRD analysis showed that the obtained materials consist from the pure hematite crystalline phase (α-Fe(2)O(3)) dispersed within ordered mesoporous silica MCM-41. Magnetic measurements show that the obtained nanocomposites exhibit at room temperature weak ferromagnetic behavior with slender hysteresis. The catalytic activity of the magnetic α-Fe(2)O(3)/MCM-41 nanocomposites was evaluated by the degradation of methylene blue (MB) aqueous solution. For this purpose, an ultrasound-assisted Fenton-like process was used. The effect of solution pH on degradation of MB was investigated. The results indicated that US-H(2)O(2)-α-Fe(2)O(3)/MCM-41 nanocomposite system is effective for the degradation of MB, suggesting its great potential in removal of dyes from wastewater. It was found that the degradation rate of MB increases with decrease in the pH value of the solution.

Complementary use of Fourier transform laser microprobe mass spectrometry and time-of-flight static secondary ion mass spectrometry for the study of the surface adsorption of organic dyes on silicate materials.

The adsorption of organic ionic dyes on different pore size engineered silica materials with potential application for industrial wastewater treatment has been investigated using Fourier transform laser microprobe mass spectrometry (FT-LMMS) and time-of-flight secondary ion mass spectrometry (TOF-S-SIMS). The complementary use of the two methods with different information depth allowed data on the subsurface distribution and pore penetration of the adsorbed organic compounds. Macroscopic methods were employed to determine the amount adsorbed on the particles and the specific external surface area. Local MS analysis allows identification of the organic dyes exclusively at the outer particle surface when the pore size is inferior to the size of the adsorbing molecule, or at the surface of the channels inside the material. Specifically, the monolayer information depth of TOF-S-SIMS causes a signal to refer essentially to the adsorbate at the outer particle surface, which is only a fraction of the total adsorption in mesoporous materials, while FT-LMMS allowed detection of the presence of adsorbates at the outer surface as well as inside the subsurface of 10 to 50 nm depending on the material under study. The observed data open perspectives for the molecular monitoring of the adsorption behaviour of different materials at the (sub) microm scale.