1,721,027 research outputs found
Promethazine−Montmorillonite Inclusion Complex To Enhance Drug Photostability
No full textABSTRACT: The capability of montmorillonite as a matrix (MONT) to improve
the photostability of photolabile drugs has been recently reported. Herein
promethazine (PRO), which was chosen as a model drug because of its
photodegradation mechanism, was intercalated into this inorganic matrix, and the
effects on drug photoprotection were evaluated as well. The hybrid material
(MONT-PRO) was successfully prepared with high drug loading and then was
characterized by X-ray powder diffraction (XRPD), differential scanning calorimetry
(DSC), and FTIR spectroscopy. The spectrophotometric measurements as a
function of light exposure time showed that PRO intercalation into montmorillonite
markedly improved the drug photostability because a 5-fold-slower degradation rate
was determined compared to that measured for PRO in homogeneous solutions;
nanosecond transient absorption measurements highlighted that the interaction
with the inorganic matrix made negligible the photoionization process of the drug,
and its efficiency in producing singlet oxygen was strongly reduced. The MONTPRO
intercalation compound could be easily formulated in gel or ointment media without losing its photostability
Crystal engineering on layered zirconium phosphonates. Crystal structure (from X-ray power data) and non-covalent interactions on the layered zirconium compound of 4-[bis(phosphonomethyl)-amino]butanoic acid
No full textA new layered zirconium diphosphonate fluoride, ZrHF(O3PCH2)2NHC3H6CO2, has been prepared by the reaction of zirconyl chloride with 4-[bis(phosphonomethyl)amino]butanoic acid in the presence of HF. Its structure has been determined "ab initio" by X-ray powder data. It crystallizes in the monoclinic space group P21/c (No. 14), with a = 12.9640(3) Å, b = 8.9900(4) Å, c = 10.7924(4) Å, β = 101.854(4)°, and Z = 4. Both of the phosphonic groups of each diphosphonate building block are bonded to zirconium atoms on the same side of the layers. Only one organic residue is associated with two phosphonate tetrahedra. The packing of layers creates an interdigitated arrangement of organic groups in the interlayer region. Two strong non-covalent interactions are present in the structure. One of them involves neighbouring P-OH and amino groups, while the other interaction engages terminal carboxylic groups and fluorine atoms belonging to adjacent layers. Thermal treatment at 240 °C causes the loss of one mole of HF per mole of zirconium, with the formation of a stable compound in which carboxylate groups probably coordinate to the zirconium atoms belonging to adjacent layers. Preliminary experiments of intercalation with ammonia and short alkylamines are also reported
Development and formulation of inorganic composites for fluoride buccal administration.
No full textCommon tooth disorders are represented by cavities, caused by tooth decay, pulpitis, periapical abscess, impacted teeth, and malocclusion. Epidemiological data from many countries highlight that there is a marked increase of tooth decay prevalence both in children and adults. Protective factors which include salivary calcium, phosphate and proteins, salivary flow, and fluoride in saliva can balance, prevent or reverse dental caries. The benefits of fluoride (F-) in the inhibition of carious lesion development and enhancement of lesion remineralization and as anticariogenic agent are well-documented.
The aim of this work was to develop buccal patches able to give a controlled release of F- ions in order to obtain a complete and prolonged teeth protection. F- ions were intercalated in the lamellar inorganic matrix hydrotalcite (HTlc) then incorporated in a mixture of mucoadhesive and film-forming polymers (NaCMC and Polycarbophil). The mucoadhesive patches were studied in terms of swelling, mucosal adhesion and organoleptic characteristics; in vitro, ex vivo and in vivo release studies of fluoride ions-loaded patches were performed as well.
Obtained results showed that the presence of HTlc matrix improves patches performances in terms of mucoadhesion and controlled release obtained by ion exchange mechanism.
These formulations resulted highly versatile resulting applicable for the buccal administration of different active pharmaceutical ingredients as antinfiammatory and antimicrobical agent
Unexpected chromogenic properties of the 1,3,3-trimethylspiro[indoline-2,3’-[3H]naphtho [2,1-b][1,4]oxazine] in solid phase: photochromism, piezochromism and acidichromism
No full textNew chromogenic properties of a spirooxazine {1,3,3- trimethylspiro(indoline-2,3′-[3H]naphtho[2,1-b][1,4]-oxazine), SO} are presented in this work. This molecule was found to be photochromic and piezochromic in the pure microcrystalline solid phase and also exhibited acidichromism when kept in contact with a hydrogen-donating solid phase. Photochromism was observed under continuous UV irradiation. Biexponential thermal bleaching followed the interruption of irradiation. Piezochromism was detected by applying a mechanical force to the solid powder, using either a hydraulic press or manual crushing. After discontinuing pressure, biexponential bleaching kinetics were observed. The biexponential nature of the fading processes is interpreted in terms of merocyanine (M) micro-spot formation inside the crystalline phase. The third chromogenic property of the solid spirooxazine, acidichromism, is due to the extraction of protons from an acidic solid matrix, alpha zirconium phosphate [α-Zr(HPO4) 2·H2O]. Proton transfer to SO in the solid phase causes the appearance of a purple colour. The spectral evolution is qualitatively similar to that observed in CH3CN solution when HClO4 is added at room temperature and in the dark. Temporal evolution of the colour bands, in both solid and liquid phases, is interpreted in terms of an initial protonation, inducing ring-opening, and a second protonation, leading to a colourless produc
Development of smart semisolid formulations to enhance retinoic acid topical application
No full textRetinoids play a very important role in the topical treatment of acne vulgaris. However their use is restricted because of the limited photo-stability responsible for local adverse effects as erythema, dryness, itching and stinging. In this way the therapeutic efficacy of such molecules is strongly reduced resulting, at the same time, harmful for the patient upon light exposure. Thus, a suitable technological strategy is necessary to increase retinoid stability in order to have a product both safe and efficacious. With this aim, new inorganic-organic hybrids based on tretinoin (RET) and hydrotalcite like-compounds (HTlc) have been prepared and well characterized by X ray powder diffraction, inductively coupled plasma spectrometry, thermal analyses, scanning electron microscopy and UV-Vis spectrophotometric measurements.
Such hybrids, namely ZnAl-HTlc-RET and MgAl-HTlc-RET, were formulated as simple gels for topical use and submitted to further studies in order to evaluate their rheological properties, photo-stability and RET release capability.
The RET photo-stability resulted improved upon intercalation into HTlc, both in MgAl-HTlc and ZnAl-HTlc, as proved by the data acquired during irradiation of the sample at 366 nm. This strategy is suitable for the realization of safe, efficacious and compliant topical formulations for acne treatment
Novel Functional Materials Based on Zirconium Carboxyphosphonates with Different Dimensionality
No full textLayered zirconium phosphonates are a class of hybrid inorgano-organic solids which structure is made of inorganic layers based on zirconium octahedra and phosphonate tetrahedra and the interlayer region is occupied by several functional groups. They represent a powerful class of materials for many applications in solid state chemistry, such as heterogeneous catalysis, nanocomposites chemistry, ion- exchange and separation and intercalation. The interest on these materials mainly resides on their high insolubility and on their chemical versatility. However, their high insolubility also represents a drawback for their correct structural characterization and for the comprehension of the structure/reactivity relationship.
Here we present the synthesis and the structural characterization by means of XRPD ab-initio methods of novel zirconium aminophosphonates based on small aminoacids (glycine derived phosphonic acids, glyphosine and glyphosate).
These compounds have different structure and dimensionality with novel and nice structural motifs. The ion- exchange, intercalation and proton conductivity properties have been also studied in details and will be discussed.
Finally a new strategy for the growth of metal nanoparticles of very small size on the layer surface of the layered zirconium aminophosphonates will be also presented.
Layered zirconium phosphonates are a class of hybrid inorgano-organic solids which structure is made of inorganic layers based on zirconium octahedra and phosphonate tetrahedra and the interlayer region is occupied by several functional groups. They represent a powerful class of materials for many applications in solid state chemistry, such as heterogeneous catalysis, nanocomposites chemistry, ion- exchange and separation and intercalation. The interest on these materials mainly resides on their high insolubility and on their chemical versatility. However, their high insolubility also represents a drawback for their correct structural characterization and for the comprehension of the structure/reactivity relationship.
Here we present the synthesis and the structural characterization by means of XRPD ab-initio methods of novel zirconium aminophosphonates based on small aminoacids (glycine derived phosphonic acids, glyphosine and glyphosate).
These compounds have different structure and dimensionality with novel and nice structural motifs. The ion- exchange, intercalation and proton conductivity properties have been also studied in details and will be discussed.
Finally a new strategy for the growth of metal nanoparticles of very small size on the layer surface of the layered zirconium aminophosphonates will be also presented
Montmorillonite as an agent for drug photostability
No full textAmong the large number of applications of montmorillonite and halloysite, low attention has been
devoted to the photostabilization effect of these matrices on photounstable agents and no studies have
been performed concerning their employment for drug photostability improvement. Herein we report
the preparation of novel hybrids of these inorganic matrices and piroxicam (PX), which was chosen as a
model drug due to its instability to light. The hybrid materials were successfully prepared with high
drug loading and then were characterized by X-ray powder diffraction (XRPD), differential scanning
calorimetry (DSC) and FT-IR spectroscopy. Finally, in order to investigate the matrix effects on
piroxicam photostability, the hybrids were subjected to spectrophotometric analysis as a function of
light exposure time. The results highlighted that PX intercalation into montmorillonite markedly
improves the drug photostability and that this matrix can be proposed as an excipient for drug
photostability enhancement
Hydrotalcite-like compounds as heterogeneous catalysts in liquid phase organic synthesis. II. Preparation of 4H-chromens promoted by hydrotalcite doped with hydrous tin (IV) oxide
No full textNew heterogeneous catalysts for liquid phase organic synthesis have been obtained by precipitating MgAl-hydrotalcites like compounds
according to the urea method in the presence of Sn(IV) and characterised for their composition, thermal behaviour, X-ray diffraction
pattern and B.E.T. specific surface area. The anion exchange capacity of the solids has been determined to have information on
the possible incorporation of Sn(IV) into the brucite layer of the hydrotalcites. The values obtained give support to the hypothesis that
most part of Sn(IV) is present as co-precipitated hydrous oxide. The base strength surface sites was estimated with the method of
adsorbed acid–base indicators and the samples have been used as heterogeneous catalysts in the preparation of 4H-chromenes. The
results obtained showed that MgAl-hydrotalcite doped with Sn(IV) catalyses the tandem Knoevenagel–Michael reactions, giving good
to excellent yields in short time and its performance has been compared with that of the corresponding MgAl-hydrotalcite. Moreover, the
catalyst was recovered and reused several times without loss of activity
Coupling physical chemical techniques with hydrotalcite-like compounds to exploit their structural features and new multifunctional hybrids with luminescent properties
No full textHydrotalcite-like compounds (HTlc), belonging to the large class of Layered Double Hydroxides (LDH),
have excited wide interest owing to the incredible number of their potential and achieved applications
in physical, chemical and bio-chemical fields. This perspective review deals with recent advances in the
application of physical–chemical techniques for the study of HTlc structure and for the design and
synthesis, using intercalation chemistry routes, of new hybrid materials. Firstly, a rapid survey on the
most common synthetic strategies for the attainment of HTlc with different crystallinity degree and crystal
size and for their modification to obtain hybrids has been made, and the use of coupled techniques
(XRPD, luminescence, Solid State MAS NMR and Molecular Dynamics) to gain structural information is
reported. Then, the design, synthesis and photophysical characterization of azoic dyes-intercalated and
co-intercalated HTlc hybrid materials are described. Hybrids constituted of ZnAl–HTlc, co-intercalated
with stearate anions and methyl orange or methyl yellow dyes, have been used as nanofillers of hydrophobic
polymers. The polymeric nano-composites obtained have been characterized by means of XRPD
patterns, Thermo-Gravimetric Analysis and Confocal Fluorescence Microscopy. This latter technique has
been found to be an excellent, complementary and non-invasive tool to probe the dispersion degree of
the fluorescent fillers into the polymeric matrices and their stability in the compounding process. Finally,
the synthesis and spectroscopic characterization of nanoparticle (NP) decorated HTlc for advanced antimicrobial
and photo-catalytic applications are also reported. The review terminates with a concluding
short note and future trends
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