Number Of Free Hydroxyl Groups Research Articles

Fabrication of a new bamboo composite with large-size high-quality flattened surface

Bamboo is a highly lignified grass with a thin wall and hollow interior. Recombination technology is commonly used to realize its scaling utilization. In this study, a high-quality flattened bamboo recombination panel (BRP) was fabricated based on the full utilization of bamboo. The BRP was designed with sandwich structure and a core layer composed of a mixture of bamboo skin strips and bamboo pith particles upon hot pressing, resembling a reinforced bar-concrete structure. The surface layer was made from densified bamboo slices through thermal-flattening (TF) to achieve stress relief and realize deformation resistant, surface modified resulted in decreased hydrophilicity. The performance of the flattened bamboo slices and BRP was analyzed, the results showed that the TF treatment was successfully modified the bamboo mid-slices, which were compressed and densified during the process. The TF treatment realized stress relief and increased surface hardness and hydrophobicity, because of a reduction in the number of free hydroxyl groups in hemicellulose. The vascular bundles and parenchyma cells of the bamboo mid-slices underwent different extents of contraction. Further, the initial moisture content was negatively correlated with the compression rate. Dynamic mechanical analysis results showed that through the TF treatment conducted at an initial moisture content (MC) of 30%, temperature of 160 ℃ and time of 4 min (30%−160 ℃−4 min) the storage elastic modulus of bamboo mid-slices increased from 5133 to 8867 MPa. The average internal bond strength, surface bond strength, and thickness swelling of the BRP bonded by phenol formaldehyde (PF) and urea-formaldehyde (UF) resins were 0.71, 0.6 MPa; 0.89, 0.82 MPa; and 9.1%, 14.7%, respectively, which meet national standards. The BRP had a high-quality flattening effect, and the flattened width could reach 2–5 times the circumference of the bamboo culm, and the performance matched that of oriented strand boards, confirming to be an upgraded product of bamboo-flattening boards and bamboo- oriented strand boards.

ANALYSIS OF THE FLOW OF A FIBROUS SUSPENSION IN A GRINDING PLANT IN THE PRODUCTION OF FINE CELLULOSE

Of the various methods for obtaining microcrystalline cellulose (mechanical, chemical, thermomechanical, planting cellulose in powder form from its solutions), the most common is acid hydrolysis of cellulose. The difficulty of obtaining MCC from vegetable raw materials is that, in addition to cellulose, it contains in its composition such compounds as lignin, hemicelluloses, various extractive substances and an insignificant percentage of minerals. When grinding plant fibers in an aqueous medium, both a purely mechanical process of changing the size and shape of fibers and a colloidal chemical process called fiber hydration occurs. Mechanical phenomena are expressed in the shortening of fibers, their longitudinal splitting into fibrils, an increase in the outer surface and the number of free hydroxyl groups on their surface. The term hydration refers to colloidal chemical phenomena that begin with the swelling of hydrophilic plant fibers.
 The paper considers methods for obtaining microcrystalline cellulose and factors influencing the development of a fibrous suspension isolated from coniferous wood species in a grinding plant with inertial bodies. Multiphysical models of the flow of fibrous suspension in the installation are constructed. A study of the effect of grinding a fibrous suspension on the process of obtaining fine cellulose was carried out. The indicators of the finished product are given. The change in the degree of polymerization of cellulose that has previously passed the grinding stage, with different degrees of grinding according to the Shopper-Rigler, is analyzed. Data on cost reduction and resource savings (acid concentration, temperature and processing time) in the process of obtaining fine cellulose are presented.

The effect of mercerization on water conductivity in cotton fabrics and its regulation

AbstractMercerization had been widely used in the textile industry because of its simplicity and ability to improve the luster, strength, and dyeing properties of cotton fabrics. However, the water transfer behavior of mercerized cotton fabrics had not been systematically investigated. In this work, cotton fabrics were treated with different concentrations of alkali (130 and 260 g/L) for structural characterization (scanning electron microscopy [SEM], Fourier transform infrared [FTIR]), water absorption (vertical wicking height), moisture absorption (moisture return rate), water retention, and so forth, and were compared with industrial mercerized cotton. It meant that water absorbency and water holding capacity of mercerized cotton textiles were improved by reducing surface impurity, increasing amorphous region, and increasing the number of free hydroxyl groups. It was easier for water molecules to move through the fabric as the vertical wicking height increased. Research showed that the water absorption and water transfer properties of cotton fabrics were related to the alkali concentration in the mercerized treatment, and a comparison with industrial mercerized cotton also proved this point. It also showed that the amount of tension had an effect on water transfer in the fabric, which provided further precision in regulating the mercerization process, improving the thermal comfort of mercerized fabrics, and achieving the aim of regulating the mercerization process according to market demand and environmental influences.

Effect of High-Temperature Hydrothermal Treatment on the Cellulose Derived from the Buxus Plant.

Cellulose has attracted considerable attention as the most promising potential candidate raw material for the production of bio-based polymeric materials. In the last decade, significant progress has been made in the production of biopolymers based on different cellulose forms. In this study, cellulose was obtained in an innovative and environmentally friendly way, using boxwood powder. Crude cellulose was obtained by treating Buxus powder with an ethanol–acetic acid–water mixture. Refined cellulose was then obtained by treatment with an acidic sodium hypochlorite solution and alkaline hydrogen peroxide solution. The novel chemistry of cellulose prepared by this method promises to be not only green, but also highly desirable, because of its lower emissions and low cost. It is crucial for the future of the global polymer industry. The refined cellulose was subjected to a high-temperature hydrothermal treatment under two temperatures and time conditions, with temperature gradients of 120, 140, and 160 °C, and time gradients of 1, 2, and 3 h. The samples were subjected to infrared and thermogravimetric analyses. The cellulose undergoes dehydration and thermal degradation reactions during the heat treatment process, and the thermal stability of the residual is enhanced, compared with that of virgin cellulose. Between 120 and 140 °C, the hydroxyl and hypomethyl groups on the surface of cellulose are shed. Groups in the amorphous region of the polymer are the first to be shed. The dehydration reaction reduces the number of free hydroxyl groups on the surface of the cellulose molecules. The dehydration reaction was accelerated by an increase in temperature. Between 140 and 160 °C, the β-(1,4)-glycosidic bond begins to slowly break and some furans are generated. The structure of cellulose undergoes reorganization during thermal treatment. The thermal stability of the modified material is greater than that of untreated cellulose.

OBTAINING SUPRAMOLECULAR COMPLEXES OF ANGIDROLAGOQUILINE WITH GLYCYRRHISINOIC ACID AND ITS SALTS AND STUDYING THEIR SPECIFIC HEMOSTATIC ACTIVITY

The hemostatic effect of drugs of the genus Lagochilus (Lamiaceae) is due to the content in its composition of four atomic alcohol diterpenoid lagochiline, alkaloid stahydrine, vitamin K and tannins. On the basis of lagochilin, a number of acetyl and isopropylidene derivatives were obtained. It has been shown that the hemostatic activity in a certain way depends on the number of free hydroxyl groups of lagochilin and its derivatives. However, lagochiline derivatives are poorly soluble in water, which limits their bioavailability. Chemical modification of lagochilin is carried out mainly by hydroxyl groups with the production of esters or succinates with dibasic anhydrides.
 For the first time, water-soluble supramolecular complexes based on the diterpenoid lactone an-hydrolagoquiline with the triterpene saponin glycyrrhizic acid (GA) and its monoammonium (MASGA) and monopotassium salts (MPSGA) in various molar ratios were obtained. The physicochemical and spectral characteristics of the resulting complex compounds have been studied. Screening studies were carried out to study the specific hemostatic activity of the obtained supramolecular complexes. Among Lagochilin Lagochirzine and their derivatives at a dose of 10 mg/kg, Lagochilin had the most active effect on bleeding time, followed by Anhydrolagochilin–Lagohirzin. The greatest effect on bleeding time at a dose of 10 mg/kg among supramolecular complexes with HA was shown by HA-AHL, which in a ratio of 2 : 1 it was impossible to determine the bleeding time, and in a ratio of 4 : 1 it reduced the bleeding time by 12 times, and the amount of blood loss by 42 times.

Silver-loaded In2S3-CdIn2S4@X(X=Ag, Ag3PO4, AgI) ternary heterostructure nanotubes treated by electron beam irradiation with enhanced photocatalytic activity

Ternary heterostructure nanotubes of In2S3-CdIn2S4@X(X = Ag, Ag3PO4, AgI) were synthesized with enhanced photocatalytic activity for efficiently degrading pollutants. Electron beam irradiation was employed to artificially introduce interface defects to the heterostructure nanotubes. The experimental results for degrading carmine and Cr6+ under visible light irradiation showed that the photocatalytic efficiency of In2S3-CdIn2S4 was improved to some extent by the introduction of silver compounds. DRS results confirmed that the band gaps of In2S3-CdIn2S4 were reduced to 1.62 eV and 1.58 eV by introducing Ag3PO4 and AgI, respectively. Interestingly, the band gap of In2S3-CdIn2S4@AgI after electron beam irradiation was further reduced to 1.56 eV, resulting in that the degradation time of both Cr6+ and carmine by In2S3-CdIn2S4@AgI after high-energy electron beam irradiation was shortened to only 5 min. The XRD spectra of the photocatalysts after five cycles could maintain the original crystal form to a large extent. The OH stretching vibration peaks of In2S3-CdIn2S4@AgI after electron beam irradiation at 3387 cm−1 became wider and sharper, thus indicating that the number of free hydroxyl groups on the heterostructure surface significantly increased. PL results showed that electron beam irradiation could significantly reduce the PL emission peak and enhance the utilization of photogenerated charge carriers. EIS results further confirmed that In2S3-CdIn2S4@AgI processed by electron beam irradiation had higher photogenerated electron-hole separation efficiency. Based on the experimental results, a feasible reaction pathway and photocatalytic mechanism for the degradation of carmine was investigated. ESR results showed that the main active groups in the whole photocatalytic system were •O2– and h+.

Unlocking the chemistry of bile acids for cancer therapeutics.

Breast cancer is the second leading cause of cancer deaths today after lung cancer and is the most common cancer among women. The primary drug tamoxifen is used treat breast cancer has several problems including poor oral bioavailability. Bile acids/salts are known to be components of endogenous molecular pool that solubilizes, absorbs dietary fat/lipid molecules in the form of micelles. Bile acids are interesting chemical scaffold for drug conjugation due to presence of different number of free hydroxyl groups and a free carboxylic acid. We have been exploring bile acids as drug carriers for cancer therapy. We used three bile acids: lithocholic acid (LCA), deoxycholic acid (DCA) and cholic acid (CA) to engineer bile acid tamoxifen conjugates with free amine and acid functionalities. In this talk, I would present the interactions of these new drug carriers and their therapeutic potential for breast cancer therapy.

Number of Free Hydroxyl Groups on Bile Acid Phospholipids Determines the Fluidity and Hydration of Model Membranes

Interactions of synthetic phospholipids with model membranes determines the drug release capabilities of phospholipid vesicles at diseased sites. We performed 1,6-diphenyl-1,3,5-hexatriene (DPH)-based fluorescence anisotropy, Laurdan-based membrane hydration, and differential scanning calorimetry (DSC) studies to cognize the interactions of three bile acid phospholipids, lithocholic acid-phosphocholine (LCA-PC), deoxycholic acid-phosphocholine (DCA-PC), and cholic acid-phosphocholine (CA-PC) with model membranes. These studies revealed that bile acid phospholipids increases membrane fluidity in DCA-PC > CA-PC > LCA-PC order, indicating that induction of membrane fluidity is contingent on the number and positioning of free hydroxyl groups on bile acids. Similarly, DCA-PC causes maximum membrane perturbations due to the presence of a free hydroxyl group, whereas LCA-PC induces gel phase in membranes due to hydrophobic bile acid acyl chain interactions. These DCA-PC-induced membrane perturbations induce a drastic decrease in phase transition temperature (Tm) as determined by calorimetric studies, whereas doping of LCA-PC causes phase transition broadening without change in Tm. Doping of CA-PC induces membrane perturbations and membrane hydration like DCA-PC but sharpening of phase transition at higher doping suggests self-association of CA-PC molecules. Therefore these differential mode of interactions between bile acid phospholipids and model membranes would help in the future for their use in drug delivery.

Mode of action of brown rot decay resistance in modified wood: a review

Abstract Chemically or physically modified wood materials have enhanced resistance to wood decay fungi. In contrast to treatments with traditional wood preservatives, where the resistance is caused mainly by the toxicity of the chemicals added, little is known about the mode of action of nontoxic wood modification methods. This study reviews established theories related to resistance in acetylated, furfurylated, dimethylol dihydroxyethyleneurea-treated, and thermally modified wood. The main conclusion is that only one theory provides a consistent explanation for the initial inhibition of brown rot degradation in modified wood, that is, moisture exclusion via the reduction of cell wall voids. Other proposed mechanisms, such as enzyme nonrecognition, micropore blocking, and reducing the number of free hydroxyl groups, may reduce the degradation rate when cell wall water uptake is no longer impeded.

An attempt to cast light into starch nanocrystals preparation and cross-linking

Potato starch was hydrolyzed with 2.2 or 3.7M hydrochloric acid in order to obtain the nanocrystals which afterwards were chemically cross-linked with sodium hexametaphosphate. The stronger acidity resulted in smaller nanocrystals with mean size of 48nm in a shorter time. X-ray diffraction confirmed the dominant crystalline nature of particles and Fourier transform infrared spectroscopy suggested the presence of lower number of free hydroxyl groups in nanocrystals after cross-linking. Starch nanocrystals showed two distinctive differential scaning colorimetry endotherms at 26 and 125°C, attributed to destruction of nanocrystals lattice and moblizing of each nanocrystal’s structure, respectively. Cross-linking resulted in a tenacious spatial arrangement of nanocrystals, strengthening the crystals lattice against phase transitions induced by heating. Scanning electron microscopy images confirmed the particle size measured for nanocrystals by light scattering. Atomic force microscopy topographic images suggested that starch nanocrystals were originated from small amylopectin blocklets in granular assembly of starch.

Chemical modification of methyl cellulose with HMDI to modulate the thickening properties in castor oil

This work deals with the selective incorporation of reactive isocyanate groups into methyl cellulose in order to be used as reactive thickening agent in castor oil. Resulting gel-like dispersions may have potential applications as green lubricating greases formulated from renewable resources. Two different isocyanate-functionalized methyl cellulose-based polymers were obtained by reaction of methyl cellulose with 1,6-hexamethylene diisocyanate. The functionalization degree, from fully functionalized to a certain number of free hydroxyl groups (58:36:6 ratio between –OMe, –NCO and free –OH groups), was controlled by modifying the reagents molar ratio. These polymers were characterized through nuclear magnetic resonance of protons (1H-NMR), Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). Thermal and rheological responses of oleogels prepared by dispersing these polymers in castor oil were studied by means of TGA analysis and small-amplitude oscillatory shear measurements. The evolution of linear viscoelasticity functions with frequency of the oleogel containing isocyanate-functionalized methyl cellulose with lower –NCO content is quite similar to that found for traditional lithium lubricating greases. In relation to long-term stability of these oleogels, the values of viscoelastic functions significantly increase during the first 7 days of ageing and then remain almost constant.

Modified TEWL in vitro measurements on transdermal patches with different additives with regard to water vapour permeability kinetics

Water vapour permeability (WVP) and water absorption capacity (WAC) influence physicochemical properties and wearability of transdermal patches considerably. For determination of WVP, a modified transepidermal water loss (TEWL) measurement was developed. These measurements continuously measure WVP of transdermal patches in vitro along with time required to reach steady state, and its magnitude according to the type of polymer used. Additionally, WAC of the patches was examined and related to WVP. According to literature in the field of WVP determination, usually selected points are taken from the evaporation time curve and averaged over a given time span without knowing whether steady state has already been reached or not. The latter causes errors upon averaging. The advantage of the in vitro TEWL measurement presented includes reproducibly adjustable conditions for every time span desired, thus providing information on the kinetics of the experiment and avoiding biased results from averaging. Knowing the shape of the evaporation time curve and thus the kinetics of the experiment allows for focusing on the relevant part of the measurement, i.e. the determination of the steady state level and the time to reach it. Four different polymers (P1-P4) based on sugar-modified polyacrylates were investigated with regard to WVP and WAC of the matrices prepared thereof along with the influence of drug loading and the incorporation of a variety of additives commonly used for transdermal patches. A clear correlation between WVP and the hydrophilicity in terms of the number of free hydroxyl groups of the polymer was elaborated. Additives of higher hydrophilicity compared to that of the polymer itself led to higher WVPs and vice versa. The combination of the model drug lidocaine in its free base form together with the additive succinic acid (Suc) resulted in ionization of the drug and thus in substantially increased WVPs. Addition of α-tocopherol acetate (Toc) into P3 and P4 and Suc into the drug-free matrix of P3 decreased WVP probably by affecting the structure of the polymer network. The same effects were found for WAC upon incorporation of succinic acid into drug-loaded matrices of P3 and P4 (drug-loaded patches of P1 and P2 were not tested) but not for additives which were likely to modify the polymer network structure.

Enumeration of hydroxyl groups of sugars and sugar alcohols by aqueous-based acetylation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The properties of carbohydrates are determined in part by the number and stereochemical arrangement of their hydroxyl groups. To facilitate their analysis, rapid methods are needed to identify and enumerate hydroxyl groups in sugars and polyalcohols, especially methods that are water-based. The present report details the results of an alternative method for identification and enumeration of hydroxyl groups in aqueous media. It employs vinyl acetate to selectively derivatize hydroxyl groups in analytes, followed by analysis of the reaction mixtures by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The method has been applied to several single and multi-component mixtures of monosaccharides and polyalcohols. The O-acetylated products were analyzed without chromatographic separation or purification by MALDI-TOF-MS. The mass spectra revealed consecutive ion peaks that are separated by 42 mass units as a consequence of displacement of one hydroxyl hydrogen by one acetyl group. A rapid and aqueous-based method is described to enumerate the hydroxyl groups in carbohydrates. The number of ion peaks due to derivatized products is determined by MALDI-TOF-MS, and corresponds to the number of free hydroxyl groups in the analyte. The method is applicable to both single and multi-component mixtures.

Humidity effect on head-disk clearance

The mechanism of head-disk-clearance change due to a humidity effect was investigated experimentally. The head-disk clearance was measured by moving the head elements towards the disk by thermal flying-height-control technology until the head touched the disk while monitoring them with an acoustic-emission sensor in an environmentally controlled component tester. Measured clearance change from 3% RH to 80% RH reached about −0.6 nm at 25°C and about −1.6 nm at 60°C. Head-disk clearance change caused by humidity was classified as the slider-flying-height change and disk-touch-down-height (TDH) change to clarify the mechanism of the clearance change. Slider FH change was dominated by absolute humidity rather than relative humidity. On the other hand, the humidity effect on disk TDH change was classified as a “water-film effect” and a “lubricant-mogul effect”, which both depend on relative humidity. Both effects caused clearance change of about 0.4 nm for lubricant A, which is a lubricant with two hydroxyl functional groups at the end of the main chain. These effects were assumed to be caused by water adsorption onto the surface of lubricant. Reduction of the number of free hydroxyl groups which attract water molecules could suppress the disk TDH change related to the humidity effect.

Characterizing Modern and Fossil Gymnosperm Exudates Using Micro-Fourier Transform Infrared Spectroscopy

Infrared absorption spectra of exudates from 65 species of gymnosperms were measured using micro–Fourier transform infrared (FTIR) spectroscopy. On the basis of the infrared spectra, three compositionally distinct groups of exudates can be distinguished: resins, volatile-rich resins, and gums. Resins and volatile-rich resins are mainly composed of terpenoids, whereas gums are polysaccharides. Resins and volatile-rich resins are restricted to conifers (Pinophyta). Gums, on the other hand, are produced by some conifer families including Araucariaceae and Podocarpaceae; nonconifer gymnosperms including Ginkgo (Ginkgophyta), cycads (Cycadophyta), and Welwitschia (Gnetophyta); and angiosperms. Using spectral band ratios, conifer resins can be subdivided quantitatively into two distinct resin types that reflect compositional differences in their terpenoid constituents and broadly parallel different conifer families. The first type of resin (pinaceous resin) is produced by members of Pinaceae and consists mainly of diterpenes that are based on abietane/pimarane skeletal structures. The second type (cupressaceous resin) is associated with members of the Cupressaceae, Sciadopityaceae, Araucariaceae, and Podocarpaceae and consists mainly of diterpenes that are based on the labdanoid structures. Variability within the resin spectra correlates with the number of free hydroxyl groups, and it can be used to assess the degree of resin polymerization. Volatile-rich resins are found exclusively within Pinaceae, reflecting a generally higher abundance of volatile mono- and sesquiterpenoids in resins of this family. The results of the FTIR spectroscopy have direct implications for the assessment of the fossil potential and the chemotaxonomic interpretation of modern and fossil gymnosperm exudates.

Combinatorial effects of mechanical activation and chemical stimulation on the microwave assisted acetylation of corn (Zea mays) starch

AbstractThe changes in the physical characteristics of ball milled corn starch (BMS) after chemical modification were investigated. The SEM and XRD analysis of BMS granules showed a fragmented aspect with a total loss of their initial crystallinity and an increase of their potential hydroxyl substitution sites. This morphology facilitated the access of the esterifying solvents into the starch molecule as corroborated by the spectacular increase of the water solubility index (WSI) and water absorption index (WAI). Following the acetylation, the degree of substitution (DS) increased up to 2.83 with the augmentation of the iodine catalyst content (p = 0.011). However, under the same condition of esterification, the DS of the BMS was slightly lower in comparison to the control, due to an increase in the number of free hydroxyl groups. Consequently to the modification, a reduction in the Tg, strong hydrophobicity and important exo‐corrosion affecting the granules were noticed.

Glucose cross-linking of polyurethane copolymer and its impact on the elevation of mechanical properties and shape memory effect

Effect of glucose cross-linking on the shape memory and mechanical properties of polyurethane (PU) block copolymer was investigated. Glucose was selected due to its large number of free hydroxyl groups, easy availability, miscibility with other reactants, and cyclic structure. The glycerol cross-linking did not affect the molecular interaction and phase separation of hard and soft segments in polyurethane structure as judged from IR and DSC analysis. Viscosity of glucose cross-linked PU increased after cross-linking due to the cross-linked structure. Maximum stress drastically improved with the adoption of glucose as a cross-linker together with a slight increase in strain at break. Shape recovery also increased with the adoption of glucose as a cross-linker, and shape recovery was not diminished after four cyclic shape recovery tests. In contrast, shape retention significantly decreased if glucose was included for two different hard segment contents. Finally, glucose cross-linking was compared with other cross-linkers used in shape memory polymer and the advantage of glucose cross-linking was discussed.

Lung Damage in Mice after Inhalation of Nanofilm Spray Products: The Role of Perfluorination and Free Hydroxyl Groups

Exposures to two commercial nanofilm spray products (NFPs), a floor sealant (NFP 1) and a coating product for tiles (NFP 2), were investigated for airway irritation, airway inflammation, and lung damage in a mouse inhalation model. The particle exposure was characterized by particle number, particle size distribution, and gravimetric analysis. BALB/cJ mice were exposed for 60 min to the aerosolized products at 3.3–60 mg/m3 (105–106 fine particles/cm3) measured in the breathing zone of the mice. Lung inflammation and lung damage were assessed by study of bronchoalveolar lavage fluid (BALF) cytology, protein in BALF, and histology. Mass spectral analysis showed that NFP 1 and NFP 2 contained hydrolysates and condensates of a perfluorosilane and alkylsilane, respectively. NFP 1 induced a concentration-dependent decrease of the tidal volume lasting for at least 1 day. Exposure concentrations above 16.1 mg/m3 (2.1 × 106 fine particles/cm3) gave rise to significant increases of protein level in BALF and reduced body weight, and histological examination showed atelectasis, emphysema, and hemorrhages. A narrow interval between the no-effect level (16.1 mg/m3) and the lethal concentrations (18.4 mg/m3) was observed. The alkylsilane-based product (NFP 2) had no effect at the concentrations studied. Experiments with different types of perfluorinated silanes and alkylsiloxanes showed that the toxic effects did not arise solely from the perfluorination. The number of free hydroxyl groups in the silanes/alkylsiloxanes was also critical for the toxicity.

Shape-memory effects of polyurethane copolymer cross-linked by dextrin

The effects of the dextrin cross-linking and hard-segment content on the shape-memory property of a polyurethane (PU) block copolymer were investigated. Although dextrin was selected due to its large number of free hydroxyl groups and ubiquitous availability, it is unfortunately insoluble in most organic solvents. The insolubility of dextrin was resolved by attaching a phenyl group onto the dextrin to reduce its hydrophilicity. The phase separations of hard and soft segments were not dependent on the dextrin cross-linking and hard-segment content, as per the results obtained from FTIR, DSC, and XRD analysis. An increased content of chemically cross-linked dextrin increased the maximum stress, but did not decrease the strain for most cases. The cross-linking density increased with increasing dextrin content, as expected. After dextrin cross-linking, the shape recovery rate was generally over 90%, and remained the same after four cyclical tests, while a low shape retention rate was observed for most cases. The best shape-memory effect, considering both the shape recovery and retention rate, was found for a PU consisting of 35 wt.% hard segment and 2 wt.% dextrin. Finally, dextrin was compared to other cross-linking compounds, such as glycerol and pentaerythritol, in this investigation.

Enhanced In Vivo Absorption of Itraconazole via Stabilization of Supersaturation Following Acidic-to-Neutral pH Transition

Previous attempts to improve the dissolution and absorption properties of itraconazole (ITZ) through advanced formulation design have focused only on release in acidic media; however, recent reports indicate that absorption occurs primarily in the proximal small intestine. This suggests that enhancing supersaturation of ITZ in neutral aqueous environments is essential for improving absorption. The aim of this study was to evaluate different polymeric stabilizers with either immediate release (IR) (Methocel™ E5, Methocel™ E50, Kollidon® 12, and Kollidon® 90) or enteric release (EUDRAGIT® L 100-55, HP-55, and HP-55S) properties to determine the chemical and physical attributes of the polymeric stabilizers that promote supersaturation of ITZ in neutral media. Each amorphous composition was produced by hot-melt extrusion and characterized by differential scanning calorimetry. Dissolution testing by a supersaturated acidic-to-neutral pH change method was conducted on each composition. Testing of IR compositions revealed that Methocel™ was a superior stabilizer compared with Kollidon® owing to stronger intermolecular interaction with ITZ molecules in solution. Increasing the molecular weight of polymers was found to promote ITZ supersaturation and was most likely attributable to increased solution viscosity resulting in retention of ITZ molecules in an enthalpically favored association with the polymer for extended durations. Of the enteric polymeric stabilizers, EUDRAGIT® L 100-55 was found to be superior to both HP-55 grades because of its greater permeability to acid that allowed for improved hydration of ITZ in the acid phase as well as a greater number of free hydroxyl groups on the polymer backbone that presumably helped to stabilize ITZ in solution. The Methocel™ E50 and EUDRAGIT® L 100-55 formulations were evaluated for in vivo drug absorption in male Sprague–Dawley rats and were found to produce a threefold greater ITZ absorption over our previously reported IR formulations. The results of this study confirmed the hypothesis that supersaturation of ITZ following an acidic-to-neutral pH transition in vitro correlates directly to in vivo absorption.