Development and evaluation of orally disintegrating tablets (ODTs) containing Ibuprofen granules prepared by hot melt extrusion

In the current study Ibuprofen was embedded in a methacrylate copolymer (Eudragit^® EPO) matrix to produce solid dispersions by hot-melt extrusion (HME) processing. The obtained granules were incorporated in orally disintegrating tablets (ODTs). The tablets were developed by varying the ratio of superdisintegrants such as sodium croscarmellose and crosslinked polyvinylpyrrolidone grades while a direct compression process was used to compress the ODTs under various compaction forces to optimize tablet robustness. The properties of the compressed tablets which included porosity, hardness, friability and dissolution profiles were further evaluated and compared with Nurofen^® Meltlet ODTs. The taste and sensory evaluation in human volunteers demonstrated excellence in masking the bitter active and improved tablet palatability.     

Estimation of physical stability of amorphous solid dispersion using differential scanning calorimetry

The physical stability of amorphous drug in solid dispersion was estimated using differential scanning calorimetry (DSC). Tolbutamide (TB) and flurbiprofen (FBP) were selected as insoluble drugs in water. Polyvinylpyrrolidone (PVP) was selected as a polymer for solid dispersion. Solid dispersions of various ratios of TB or FBP and PVP-K25 were prepared by solvent evaporation method and the induction period of crystallization from amorphous drug in solid dispersion was measured by DSC. Compared with FBP, the induction period of crystallization from TB was delayed by an addition of PVP. The improvement of the physical stability by the addition of PVP-K25 was estimated from the activation energy of diffusion of drug molecules and the interfacial free energy between drug crystal and supercooled liquid of drug in solid dispersion. From thses results, the hindrance of the diffusivity of the drug molecule might be mainly affected the delay of the induction period of crystallization of TB and FBP.     

Quercetin-PVP K25 solid dispersions

Quercetin is a flavonoid very well studied and has already entered clinical trials emerging as prospective anticancer drug candidate. In addition, quercetin has being reported to its free-radical scavenging activity and suggests potential uses for the prevention and treatment of pathologies as atherosclerosis, chronic inflammation, and others. However, quercetin is sparingly soluble in water, which may be responsible for its limited absorption upon oral administration. The solid dispersion of quercetin with polyvinylpyrrolidone Kollidon^® 25 (PVP K25) suggests an interesting way to increase quercetin solubility, antioxidant activity, and consequently bioavailability. Then, the purpose of this study was to prepare solid dispersions of quercetin with PVP K25 and evaluate their thermal characterization, antioxidant activity and quercetin improvement solubility. For this purpose, quercetin-PVP K25 solutions were dried and quercetin-PVP K25 solids were obtained. The formation of quercetin-PVP K25 solid dispersion was evaluated by solubility studies, powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetry (TG), and antioxidant activity. It was observed that PVP K25 was able to provide quercetin clear aqueous solutions and that quercetin solubility was increased in a PVP K25 concentration dependent manner, improving solubility even 436-fold the pure quercetin. The results obtained with XRD, FT-IR, DSC, and TG demonstrated possible quercetin-PVP K25 solid dispersion formation. Besides, the antioxidant activity of the quercetin-PVP K25 solid dispersions dissolved in aqueous solution and pure quercetin dissolved in methanol showed IC₅₀ value of 0.61 ± 0.03 and 1.00 ± 0.02 μg/mL, respectively, demonstrating that the solid dispersions presented a significant increase in antioxidant activity (P < 0.05). Putting results together, it was possible to conclude there was the formation of quercetin-PVP K25 solid dispersion.     

Novel aspects of nanocellulose

Novel nanoscaled cellulose particles were prepared using high-pressure homogenization of aqueous media contenting treated cellulose samples in a Microfluidizer^® processor (MF). Here, we present the generation of spherical cellulose nanoparticles as an extension of previously published reports of nano fibrillated cellulose. Although MF treatment of unmodified cellulose yields nanofibrils which are reported in several publications, in the current work different kinds of pretreatments were proven to be necessary to obtain spherical structured cellulose nanoparticles. One such treatment may be the decrystallization of cellulose regenerating it from N-methylmorpholine-N-oxid-monohydrate (NMMNO*H₂O). Nanocellulose was then obtained by a subsequent high-pressure mechanical treatment of the precipitate in aqueous dispersion. Decrystallization was also realized by grinding cellulose in a planetary ball mill. The resulting amorphous intermediates were characterized by Raman spectroscopy. Another approach tested was hydrolysis and subsequent mechanical treatment using an Ultra-Turrax^® and MF. Another alternative was given by the mechanical treatment of aqueous dispersions of low substituted cellulose derivatives such as carboxymethyl cellulose and oxidized cellulose without any further hydrolysis.     

Influence of Drug Load on the Printability and Solid-State Properties of 3D-Printed Naproxen-Based Amorphous Solid Dispersion

Fused deposition modelling-based 3D printing of pharmaceutical products is facing challenges like brittleness and printability of the drug-loaded hot-melt extruded filament feedstock and stabilization of the solid-state form of the drug in the final product. The aim of this study was to investigate the influence of the drug load on printability and physical stability. The poor glass former naproxen (NAP) was hot-melt extruded with Kollidon^® VA 64 at 10–30% w/w drug load. The extrudates (filaments) were characterised using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). It was confirmed that an amorphous solid dispersion was formed. A temperature profile was developed based on the results from TGA, DSC, and DMA and temperatures used for 3D printing were selected from the profile. The 3D-printed tablets were characterised using DSC, X-ray computer microtomography (XµCT), and X-ray powder diffraction (XRPD). From the DSC and XRPD analysis, it was found that the drug in the 3D-printed tablets (20 and 30% NAP) was amorphous and remained amorphous after 23 weeks of storage (room temperature (RT), 37% relative humidity (RH)). This shows that adjusting the drug ratio can modulate the brittleness and improve printability without compromising the physical stability of the amorphous solid dispersion.     

Prediction of the induction period of crystallization of naproxen in solid dispersion using differential scanning calorimetry

The induction period of crystallization of amorphous naproxen in solid dispersion was measured by DSC. Hydroxypropylmethylcellulose acetate succinate LG (HPMCAS-LG) was selected as a polymer of solid dispersion, because of the excellent inhibitory effect of crystallization. Naproxen was chosen as a model drug having poor water solubility and poor physical stability of glassy state. The prediction of crystallization of amorphous naproxen in solid dispersion at the desired storage temperature or the desired polymer content was carried out. If the storage condition satisfied the requirement that was either more than 90% of HPMCAS-LG content at 333 K or below storage temperature of 301 K for 50% HPMCAS-LG content, the induction period of crystallization of naproxen in solid dispersion would be more than 1 year. The storage period of amorphous drug in solid dispersion of desired storage temperature and desired drug content might be predictable from measurement data of induction period of crystallization.     

Thermal analysis of poly(2-methylpentamethylene terephthalamide)

Poly(2-methylpentamethylene terephthalamide) (Nylon M5T) is a new high temperature aromatic polyamide developed by Hoechst Celanese. In this paper thermal properties of Nylon M5T chips, as well as as-spun and drawn fibers were studied by DSC, DMA, hot stage microscopy and WAXS.T _g of the fully amorphous Nylon M5T is 143°C when measured by DSC;T _g increases with crystallinity to 151°C. The temperature dependence of the solid and melt specific heat capacities has also been determined. The heat capacity increase at the glass transition of the amorphous polymer is 103.9 J °C^–1 mol^–1.T _g by DMA for the as-spun fiber is 155°C, for a drawn fiber is 180°C. Three secondary transitions were observed by DMA in addition to the glass transition. These correspond to a local mode relaxation of the methylene groups at –120°C, onset of rotation of the amide-groups at –65°C and the onset of the rotation of the phenylenegroups (at 63°C). The crystallinity of Nylon M5T strongly depends on the rate of cooling from the melt. The isothermal crystallization data are melt temperature dependent: two-dimensional crystallization takes place when the samples are crystallized from higher melt temperatures, and this phase changes into a spherulitic structure during cooling to room temperature. Spherulitic crystallization occurs when lower melt temperatures are used. This polymer has three crystal forms as indicated by DSC, DMA and WAXS data. The crystal to crystal transitions are clearly visible when amorphous samples are heated in the DSC, or the DMA curves of as-spun fibers are recorded. It is experimentally shown that a considerable melting of the lower temperature crystal forms takes place during the crystal to crystal transitions. The equilibrium melting point as measured by the Hoffman-Weeks method, has been determined to be 339°C.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthday     

Simultaneous voltammetric determination of carbendazim and carbaryl in medicinal plant infusions with a boron-doped diamond electrode

This study is aimed to develop an electroanalytical methodology using a boron-doped diamond electrode to determine simultaneously and selectively carbendazim (CBZ) and carbaryl (CAR). In previous studies using cyclic voltammetry oxidation, peaks were observed at 1.03 V (CBZ) and 1.44 V (CAR), with characteristics of an irreversible process controlled by diffusion of species, with a supporting electrolyte of BR buffer (0.1 mol L^?1) and pH adjusted to 6.0. The differences between the potentials for both pesticides, about 400 mV, indicate the possibility of selective determination of CBZ and CAR. The square-wave voltammetric parameters were optimised. The best separation conditions were pH 6.0, square-wave frequency of 100 s^?1, pulse amplitude of 50 mV and scan increment of 2.0 mV. These parameters were used to obtain the calibration curves of CBZ and CAR. An analytical curve was constructed in the range concentration of CBZ of 1.3 mg L^?1 to 15.3 mg L^?1 and CAR of 1.0 mg L^?1 to 11.4 mg L^?1, respectively. The limits of detection (LOD) and limits of quantification (LOQ) for CBZ were 0.40 mg L^?1 and 1.30 mg L^?1, respectively. For CAR, the LOD and LOQ were 0.30 mg L^?1 and 1.00 mg L^?1, respectively. Sensitivity values were 0.78 and 2.60 µA/mg L^?1 for CBZ and CAR, respectively. The electroanalytical method was applied in Mikania glomerata infusions. The recovery values were 106.2% and 116.5% for CBZ and CAR, respectively. The results show that the developed method is suitable for application in medicinal plant samples.     

Molar mass distributions and viscosity behavior of perfluorinated sulfonic acid polyelectrolyte aqueous dispersions

Perfluorinated sulfonic acid polyelectrolyte aqueous dispersions originating from similar polymer feed stocks and having similar compositions can have order‐of‐magnitude viscosity differences that are dependent on the manufacturing process. To better understand this phenomenon at the molecular level, a size exclusion chromatography method incorporating static light scattering detection was developed. The initial apparent mass distributions were broad and bimodal for all dispersions. A high‐molar‐mass shoulder was consistent with a previously postulated aggregate structure, and the evidence suggested that molecular aggregation accounted for viscosity variability. The apparent weight‐average molar masses ranged from 1.3 × 10⁶ to 3.9 × 10⁶ g mol^?1. Upon the heating of the dispersions at or above 230 °C, the aggregate structure was broken down, and this resulted in similar low‐viscosity dispersions that had monomodal mass distributions. The weight‐average molar masses were reduced to approximately 2.5 × 10⁵ g mol^?1, and the polydispersities were approximately 1.7–1.8. Shear thinning with higher viscosities and apparent molar masses was rationalized with intrinsic viscosity and other measurements, which supported an anisotropic aggregate structure, with particles that could be significantly overlapped at nominal 11% concentrations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 421–428, 2005     

Characterization of solid dispersions of rofecoxib using differential scanning calorimeter

Summary Solid dispersions were prepared to enhance the dissolution rate of rofecoxib. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used for the characterization of solid dispersions of polyvinyl pyrrolidone (PVP):talc:drug (3:1:1) and hydroxypropyl methylcellulose (HPMC):talc:drug (4:1:1). The DSC study indicated that PVP solid dispersion showed formation of fusion solution while HPMC solid dispersion showed no intermolecular fusion during the preparation of solid dispersions by spray dry process. The dissolution profiles and the calculated times for 75 and 90% drug release showed that dissolution rate of rofecoxib was improved in solid dispersions as compared to pure drug and physical mixtures. The DSC and XRD were successfully employed to find out the crystalline state of drug in the both solid dispersions. PVP solid dispersion gave better dissolution rate than HPMC solid dispersion. The drug was transformed from crystalline to amorphous form in PVP solid dispersion which was further conformed by XRD and DSC. The PVP:talc:drug solid dispersion can be used for the dissolution enhancement and thereby bioavailability of rofecoxib.     

Thermal analysis study of flavonoid solid dispersions having enhanced solubility

Purposes of this paper were to prepare and study new drug delivery systems for both flavanone glycosides and their aglycones based on solid-dispersion systems. These compounds are poor water soluble drugs, so an enhancement of their dissolution is a high priority. Solid-dispersion systems were prepared using PVP, PEG and mannitol as drug carrier matrices. Characterizations of these dispersions were done by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The glass transition (T_g) temperature of PVP was only recorded in the DSC thermograms of PVP solid-dispersions of both flavanone glycosides and their aglycones, while in case of PEG and mannitol solid-dispersions endotherms of both glycosides and aglycones were noticed with low peak intensity, indicating that high percent of drug is in amorphous state. The XRD patterns of all PVP solid-dispersions of aglycones show typical amorphous materials, but XRD patterns of their glycosides reveal the presence of crystalline material. However, in all solid dispersions shifts in T_g of PVP as well as T_m of PEG were observed, indicating the existence of some interactions between drugs and matrices. SEM and TEM microscopy revealed that PVP/aglycone flavanone compounds are nanodispersed systems while all the other solid dispersions are microcrystalline dispersions. The solubility of both flavanone glycosides and their aglycones was directly affected by the new physical state of solid dispersions. Due to the amorphous drug state or nano-dispersions in PVP matrices, the solubility was enhanced and found to be 100% at pH 6.8 in the nano-dispersion containing 20 mass% of aglycones. Also solubility enhancement was occurred in solid dispersions of PEG and mannitol, but it was lower than that of PVP nano-dispersions due to the presence of the drug compounds in crystalline state in both matrices.     

Oxygen‐barrier properties of oriented and heat‐set poly(ethylene terephthalate)

The improvement in the oxygen‐barrier properties of poly(ethylene terephthalate) (PET) by orientation and heat setting was examined. Orientation was carried out at 65 °C by constrained uniaxial stretching to a draw ratio of about 4. Heat setting was performed at temperatures from 90 to 160 °C with the specimen taut. Orientation decreased the permeability of PET to almost one‐third that of the unoriented, amorphous polymer because of decreases in both the diffusion coefficient and the solubility coefficient. The proposed two‐phase model for oriented PET consisted of a permeable isotropic amorphous phase (density = 1.335 g/cm³) with ethylene linkages predominately in the gauche conformation and an impermeable oriented phase (density = 1.38 g/cm³) with ethylene linkages that had transformed from the gauche conformation to the trans conformation during stretching. Chain segments in the trans conformation did not possess crystalline order; instead, they were viewed as forming an ordered amorphous phase. Crystallization by heat setting above the glass‐transition temperature did not dramatically affect the permeability. However, a decrease in the diffusion coefficient, offset by an increase in the solubility coefficient, indicated that crystallization affected the barrier properties of the permeable amorphous phase. Analysis of the barrier data, assuming a two‐phase model with variable density for both the permeable and impermeable phases, revealed that the impermeable phase density increased during crystallization, approaching a value of 1.476 g/cm³. This value is consistent with previous measurements of the density of the defective crystalline phase in PET. The density of the permeable amorphous phase decreased concurrently to about 1.325 g/cm³, indicating the appearance of additional free volume. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1679–1686, 2000     

Preformulation study of nicergoline solid dispersions

Nicergoline, a semisynthetic ergot derivative, which, in its crystalline state, is insoluble in water, was dispersed in polyvinylpyrrolidone K30 (PVP K30) to improve drug particle dissolution. Preformulation studies were carried out initially by differential scanning calorimetry and X-ray powder diffraction in order to predict the conditions and the possibility to actually obtain solid dispersions by mixing the two components at different proportions. Solid dispersions were finally prepared by dissolving nicergoline and PVP K30 in chloroform that was next evaporated under reduced pressure. Under these conditions, an amorphous powder was recovered in every proportion of the two components. Nicergoline demonstrated to be physically and chemically stable for 1 year. The dissolution studies revealed a very high dissolution rate of nicergoline from solid dispersions only lower than the pure amorphous form. This is the consequence of the molecular dispersion of nicergoline in the polymer that enhances the rate of drug release from the polymer.     

A Sensitive Flow Injection Fluorimetry for the Determination of Carbamazepine in Human Plasma

Abstract

A simple, sensitive, and specific flow injection fluorimetric method has been developed for the determination of carbamazepine (CBZ). The proposed method is based on use of a solid‐phase reactor containing lead dioxide for on‐line oxidization of CBZ into a strongly fluorescent compound in a medium of phosphoric acid. The product has a green‐yellow fluorescence at a maximum excitation wavelength of 355 nm and an emission wavelength of 478 nm. Under the optimum conditions, the fluorescence intensity is proportional to the concentration of CBZ ranging from 0.0005 to 4.000 µg mL^?1. The detection limit is 5.7×10^?5 µg mL^?1 (2.4×10^?10 mol L^?1) and the relative standard deviation is 1.4% at the sampling rate of 45 h^?1. The proposed method has been applied to clinical estimation of CBZ in real patients' plasma samples with the results compared with those obtained by HPLC method.     

An Experimental Design for Simultaneous Determination of Carbendazim and Fenamiphos by Electrochemical Method

This study is aimed to develop an electroanalytical methodology using a boron‐doped diamond electrode (BDD) associated with experimental design in order to determine simultaneously and selectively carbendazin (CBZ) and fenamiphos (FNP) pesticides. In previous studies oxidation peaks were observed at 1.10 V (CBZ) and 1.20 V (FNP), respectively, with characteristics of irreversible processes controlled by diffusion of species (in pH 2.0 (CBZ) and pH 3.5 (FNP)) using a BR buffer 0.1 mol L^?1 as support electrolyte. The differences between the potentials for both pesticides, (about 100 mV) indicate the possibility of selective determination of FNP and CBZ. However, employing an equimolar mixture of analytes, the peaks overlap to form a single oxidation peak. Thus, we used a 3⁴ full factorial design with four parameters to be analyzed in three levels, in order to obtain the optimized parameters for the separation of the peaks. The best separation conditions were pH 5.0, square wave frequency of 300 s^?1, pulse amplitude of 10 mV and scan increment of 2 mV. These parameters were used to obtain the calibration curves of CBZ and FNP. For CBZ the analytical curve was obtained in the concentration range of 4.95×10^?6 to 6.90×10^?5 mol L^?1 with good sensitivity and linearity (0.175 A/mol L^?1 and 0.999, respectively). The limits of detection (LOD) and quantification (LOQ) were 1.6×10^?6 mol L^?1 and 5.5×10^?6 mol L^?1, respectively. For FNP the linear concentration interval was 4.95×10^?6 to 3.67×10^?5 mol L^?1, with a sensitivity of 0,207 A/mol L^?1 and linearity of 0.996. The LOD and LOQ were 4.1×10^?6 mol L^?1 and 13.7×10^?6 mol L^?1, respectively. Using these experimental conditions it was possible to separate the oxidation peaks of CBZ (E_p=1.08 V) and FNP (E_p=1.23 V). The electroanlytical method was applied in lemon juice samples. The recovery values were 110.0 % and 92.5 % for CBZ and FNP, respectively. The results showed that the developed method is suitable for application in foodstuff samples.     

Effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene

The effects of molecular characteristics and processing conditions on melt‐drawing behavior of ultrahigh molecular weight polyethylene (UHMW‐PE) are discussed, based on a combination of in situ X‐ray measurement and stress–strain behavior. The sample films of metallocene‐ and Ziegler‐catalyzed UHMW‐PEs with a similar viscosity average MW of ～10⁷ were prepared by compression molding at 180 °C. Stress profiles recorded at 160 °C above the melting temperature of 135 °C exhibited a plateau stress region for both films. The relative change in the intensities of the amorphous scattering recorded on the equator and on the meridian indicated the orientation of amorphous chains along the draw axis with increasing strain. However, there was a substantial difference in the subsequent crystallization into the hexagonal phase, reflecting the molecular characteristics, that is, MW distribution of each sample film. Rapid crystallization into the hexagonal phase occurred at the beginning point of the plateau stress region in melt‐drawing for metallocene‐catalyzed UHMW‐PE film. In contrast, gradual crystallization into the hexagonal phase occurred at the middle point of the plateau stress region for the Ziegler‐catalyzed film, suggesting an ease of chain slippage during drawing. These results demonstrate that the difference in the MW distribution due to the polymerization catalyst system dominates the phase development mechanism during melt‐drawing. The effect of the processing conditions, that is, the including strain rate and drawing temperature, on the melt‐drawing behavior is also discussed. The obtained results indicate that the traditional temperature–strain rate relationship is effective for transient crystallization in to the hexagonal phase during melt‐drawing, as well as for typically oriented crystallization during ultradrawing in the solid state. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2455–2467, 2006     

Testing of the structure of macromolecular polymer films containing solid active pharmaceutical ingredient (API) particles

The aim of the present study was to investigate the structure of free films of Eudragit^® L 30D-55 containing different concentrations (0%, 1% or 5%) of diclofenac sodium by positron annihilation spectroscopy. The data revealed that the size of the free-volume holes and the lifetimes of ortho-positronium atoms decreased with increase of the API concentration. Films containing 5% of the API exhibited a different behavior during storage (17 °C, 65% relative humidity (RH)) in consequence of the uptake of water from the air.     

Characterization of a complex dispersion of multilamellar vesicles

Spherulites ^® are multilamellar vesicles made up of surfactant bilayers. These vesicles would potentially be very useful for the encapsulation and protection of molecules; however, traditional formulations of these vesicles are poor at retaining small hydrophilic molecules (below 1000 g/mol). In this study, we present new systems of Spherulites called complex dispersions. These are prepared by dispersing Spherulites in an oil medium, and then emulsifying this oily dispersion of Spherulites within an aqueous solvent. These new systems provide an additional oil barrier between encapsulated molecules and an external aqueous phase. We have used polarized light optical microscopy, X-ray diffraction and freeze–fracture electron microscopy to study a complex dispersion of Spherulites at all stages of its preparation. We first studied the sheared lamellar phase, followed by the dispersion of the multilamellar vesicles in the oily medium and finally the emulsification of the oily dispersion within the aqueous solvent. We compared our results on lamellar phases with previous results obtained with Spherulites directly dispersible in an aqueous medium. Since the formulation of our lamellar phase included a large percentage of oil as a component, we studied the localization of the oil in the lamellar structure. We also studied the influence of osmotic pressure on complex dispersions, because complex dispersions possess a double structure similar to that of water-in-oil-in-water emulsions and multiple emulsions are known to be sensitive to osmotic pressure. In conclusion, complex dispersions proved to be new potential carriers exhibiting some unique physical properties.     

Stability and solution concentration enhancement of resveratrol by solid dispersion in cellulose derivative matrices

Resveratrol is a highly biologically active phytoalexin, found in many plant materials that are common elements of the human diet, such as grapes, nuts, and red wine. The therapeutic or disease preventative potential of this natural polyphenolic antioxidant has been limited in part due to its poor aqueous solubility and low oral bioavailability. We hypothesized that solid dispersion of resveratrol (Res) in cellulose derivative matrices might afford amorphous dispersions, from which supersaturated Res solutions would be produced in the human gastrointestinal (GI) tract, resulting in higher Res bioavailability. We carried out structure–property studies employing cellulose esters with a range of physical characteristics but possessing features suitable for use in amorphous solid dispersions: carboxymethylcellulose acetate butyrate (CMCAB), hydroxypropylmethylcellulose acetate succinate (HPMCAS) and cellulose acetate adipate propionate (CAAdP). The cellulose derivative results were compared with those of a negative control, pure crystalline Res, and a positive control, Res/poly(vinylpyrrolidinone) (PVP). Solid dispersions were characterized by powder X-ray diffraction (XRPD), modulated differential scanning calorimetry (MDSC), nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR) of solid dispersions. HPMCAS and PVP solid dispersions afforded faster and more complete Res release at pH 6.8; however Res is also released from PVP matrices at pH 1.2. The carboxyl-containing cellulose derivatives release Res to only a small extent at pH 1.2. This combination of solution and solid phase stabilization against crystallization, and pH-triggered drug release makes these cellulose esters attractive candidates for Res bioavailability enhancement.     

Thermal, rheological, and barrier properties of waterborne acrylic nanocomposite coatings based on boehmite or organo-modified montmorillonite

An organo-modified montmorillonite (Cloisite^®30B) or an unmodified boehmite (Disperal^®40) have been added to two acrylic latex dispersions (one of them UV-curable) for obtaining nanocomposite coatings. X-ray diffraction and transmission electron microscopy show a high degree of exfoliation in the nanocoatings based on montmorillonite, together with the deagglomeration of the micrometer-sized boehmite powder and the presence of single boehmite crystallites within the polymer matrix. Such morphologies are found to enhance the thermal and thermo-oxidative stability of the latexes and to significantly decrease their oxygen permeability, as well.