Melamine formaldehyde: curing studies and reaction mechanism

Carbamazepine is a water-insoluble antiepileptic drug. Being a BCS class-II drug, its absorption is dissolution rate limited. Solid dispersions were prepared to enhance the dissolution rate of the drug. Crospovidone and croscarmellose sodium were used as the hydrophilic carriers. Solid dispersions showed a remarkable enhancement in the dissolution rate of the drug. In the present research work, the solid dispersions were formulated in to fast dissolving tablets. The prepared tablets were evaluated for hardness, friability, drug content, disintegration time and the in vitro dissolution rate. The solid dispersions were characterized by Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). The DSC study revealed a marked reduction in the crystallinity of the drug. The faster dissolution rate of the solid dispersion is attributed to a marked reduction in the crystallinity of the drug. The FTIR and DSC studies demonstrated the absence of drug-polymer interaction. The formulated tablet (F2) achieved a 7 fold faster dissolution rate compared to the marketed tablet.

The hydrothermal synthesis of aluminophosphate molecular sieve type AlPO4-11 was processed from chemicals containing psueudobohemite, 85% phosphoric acid, water, and di-isopropylamine as templating agent. The crystallization of the samples was studied by taking samples in times from 2 to 74 h. The obtained white powder products were characterized by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and differential scanning calorimetry (DTG) data and pH measurement of the mother liquor. The pore volume, as determined from TG and DTG curves, was ca. 0.17 cm3g−1. The percent relative crystallinity was determined by XRD and FT-IR methods. The crystallization kinetics evidenced that the hydrothermal synthesis of AlPO4-11 exhibited in its initial phase a behavior of first order reaction with a specific velocity constant of ca. 0.25 h−1, as determined from XRD and FT-IR data. The results obtained by both X-ray diffraction and infrared spectroscopy are comparable, and FT-IR is found to be a rapid method for estimating crystallinity and structure of aluminophosphate.

This work involves the preparation and characterization of alginate nanoparticles (Alg NPs) as a new transdermal carrier for site particular transport of glucosamine sulfate (GS). The GS–Alg NPs were examined through transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dielectric spectroscopy. GS–Alg NPs was efficiently prepared via ionic gelation method which generates favorable conditions for the entrapment of hydrophilic drugs. The TEM studies revealed that GS–Alg NPs are discrete and have spherical shapes. FTIR studies showed a spectral change of the characteristic absorptions bands of Alg NPs after encapsulation with GS because of the amine groups of GS and the carboxylic acid groups of Alg. The DSC data showed changes in the thermal behavior of GS–Alg NPs after the addition of GS indicating signs of main chemical interaction among the drug (GS) and the polymer (Alg). The absence of the drug melting endothermic peak within the DSC thermogram of GS–Alg NPs indicating that GS is molecularly dispersed in the NPs and not crystallize. From the dielectric study, it was found modifications within the dielectric loss (ε″) and conductivity (σ) values after the addition of GS. The ε″ and σ values of Alg NPs decreased after the addition of GS which indicated the successful encapsulation of GS within Alg NPs. Furthermore, the dielectric study indicated an increase of the activation energy and the relaxation time for the first process in the GS–Alg NPs as compared to Alg NPs. Consequently, the existing observations indicated an initiation of electrostatic interaction among the amine group of GS and carboxyl group of Alg indicating the successful encapsulation of GS inside Alg NPs which could provide favorable circumstance for the encapsulation of GS for topical management.

Multivariate analysis models were developed to evaluate the results obtained from a compatibility study designed for ibuprofen with a large group of different types of excipients, as a possible approach for rapid screening of the incompatibility between the active pharmaceutical ingredient (API) and excipients. The solid-state characterization of the binary mixtures was performed by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) using SIMCA® software were applied for evaluation of the experimentally obtained results. The optimal PCA model for the FTIR spectra explains 96.2 % of the variations in the dataset with good statistical indicators (R2X = 0.960, Q2 = 0.900), which was also the case for the PCA model for the DSC curves (R2X = 0.981, Q2 = 0.866). The applied PLS-DA models have shown similar behaviour to the PCA. Moreover, the main spectral variations in the FTIR spectra and the thermal events in the DSC data were attributed the highest variable importance for the projection (VIP) scores in the corresponding VIP plots, confirming the model capability for predicting ibuprofen interactions. Furthermore, the prediction power of the optimal models for FTIR and DSC experimental data was evaluated by the root mean square error of prediction (RMSEP) of 0.10 and 0.16, respectively. The obtained results demonstrated the potential of multivariate statistical analysis as a machine learning-based technique for screening and prediction of ibuprofen-excipients solid-state compatibility in the preformulation phase of the pharmaceutical development of dosage forms.

Doxorubicin loaded into liposomes grafted with polyethylene glycol (PEG) has been demonstrated to have a longer circulation time and lower cardiotoxicity than doxorubicin (DOX). This study aims to investigate the biophysical characterization of a marketed formulation DOX-encapsulated liposome (DOX-NPTM). The interactions between doxorubicin and liposomal lipids can help in liposomal development. The liposome and DOX-NPTM were characterized in terms of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The rheological properties of liposomal samples were also measured. Physical interactions may be occurred between the drug functional groups and liposomal lipids, probably by weak hydrogen bond formation or weak bond formation due to dipole-dipole interaction. There was no shift of existing peaks or appearance of new peaks was detected between the characteristic peaks of the liposomal lipids were present in the DOX-encapsulated liposome sample. This suggests that there were physical interactions that took place only between the drug and lipids and no chemical interaction between them. DSC information shows that the phase transition temperature shifts to lower temperature degrees after loading of DOX into the liposomes. The DSC curve has a small broadening. This may infer a little cooperativity decrease between acyl chains of liposomal membranes after DOX inclusion. The encapsulation of DOX into liposomes decreases the plastic viscosity of liposomes (from 1.64 to 1.48 cP), which shows that the membrane fluidity was increased.

Purpose: To develop a pH-controlled two-pulse drug delivery system of amoxicillin in order to overcome the snag of biological tolerance and to improve bactericidal activity.Methods: The core tablets were compressed and coated with hydroxylpropyl methylcellulose (HPMC) of different viscosities with spray-dried lactose (SDL) as a pore former. The final two-pulse release tablet was prepared with the remaining drug fraction (to be released as the first immediate release pulse) with a disintegrant, giving the final tablet. The tablets were evaluated for pharmaceutical properties including disintegration, thickness, hardness, friability and weight variation and by DSC (differential scanning calorimetry) and FTIR (Fourier transform infrared spectroscopy) studies in order to assess drug/polymer compatibility. The tablets further subjected to in vitro dissolution studies and stability studies.Result: The tablet core disintegrated within 30 to 40 s. Drug content ranged from 97.85 to 98.23 %. FTIR and DSC studies showed drug-polymer compatibility. The developed two-pulse release tablets had acceptable thickness, hardness, friability and weight variation. In vitro drug release showed prolongation of lag time as polymer viscosity increased. With 25 % HPMC and 75 % SDL, drug release was 97.5 % by the end of 8th , 9th &10th h and viscosity was 100, 400 and 4000 cps respectively. No significant difference in drug release was found as values were within limits of confidence interval (p < 0.05). The formulation was stable.Conclusion: The developed formulation demonstrates the feasibility of a two-phase release of amoxicillin separated by a well-defined time-controlled lag phase which is desirable for chronotherapeutic drug delivery.Keywords: Two-pulse drug delivery, Chronotherapeutic drug delivery, Bacterial drug resistance, Amoxicillin

A series of polyurethane networks were prepared from MDI (4,41-diphenyl methane diisocyanate), ethylene glycol and a polyoxyethylene-tipped polyoxypropylene triol. The phase separation and phase inversion phenomena of these polyurethane networks were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and measurement of their tensile properties. The DSC and DMA data indicate that the segmented copolyurethanes possess a two-phase morphology comprising soft and hard segments. It can be found from DSC data that the polyether soft segments exhibit a Tg (glass transition temperature) of −60 °C, and the aromatic hard segments display a Tg of about 128 °C. Two Tgs corresponding to the comprised segments can also be found by DMA for some segmented polyurethanes. Varying the content of aromatic hard segments over the range from 0 to 80 wt% changes the material behavior from a soft rubber through a highly extensible elastomer to a brittle semi-ductile glassy material. Based on the property-composition plots, phase inversion appears to occur at a hard segment content of about 50 wt%.

Microspheres (MS) of Ketorolac Tromethamine (KT) for oral delivery were prepared by complex coacervation (method-1) and simple coacervation (method-2) methods without the use of chemical cross–linking agent (glutaraldehyde) to avoid the toxic reactions and other undesirable effects of the chemical cross-linking agents. Alternatively, ionotropic gelation was employed by using sodium-tripolyphosphate (Na-TPP) as cross linking agent. Chitosan and gelatin B were used as polymer and copolymer respectively. All the prepared microspheres were subjected to various physico-chemical studies, such as drug-polymer compatibility by Thin Layer Chromatography (TLC) and Fourier Transform Infra Red Spectroscopy (FTIR), surface morphology by Scanning Electron Microscopy (SEM), frequency distribution, encapsulation efficiency, in-vitro drug release characteristics and release kinetics. The physical state of drug in the microspheres was determined by Differential Scanning Calorimetry (DSC) and X-ray powder Diffractometry (XRD). TLC and FTIR studies indicated no drug-polymer incompatibility. All the MS showed release of drug by a fickian diffusion mechanism. DSC and XRD analysis indicated that the KT trapped in the microspheres existed in an amorphous or disordered-crystalline status in the polymer matrix. It is possible to design a controlled drug delivery system for the prolonged release of KT, improving therapy by possible reduction of time intervals between administrations.

A tetraphenylethylene-functionalized benzoxazine and copper(II) acetylacetonate form a high-performance polybenzoxazine

The effect of silane treatment of carboxylic-functionalized multi-walled carbon nanotubes (COOH-MWCNTs) on the thermal properties of COOH-MWCNTs/epoxy nanocomposites was studied by comparing the research results on differential scanning calorimetry and thermogravimetric analysis data of silane treated COOH-MWCNTs/epoxy system with those of as-received COOH-MWCNTs/epoxy system. At the initial curing stage, silane treatment of COOH-MWC- NTs does not change the autocatalytic cure reaction mechanism of COOH-MWCNTs/diglycidyl ether of bisphenol-A gly- cidol ether epoxy resin/2-ethyl-4-methylimidazole (COOH-MWCNTs/DGEBA/EMI-2,4) system, however, silane treatment of COOH-MWCNTs has catalytic effect on the curing process, which could help to shorten pre-cure time or lower pre-temperature. Then, at the later curing stage, silane treatment of COOH-MWCNTs promotes vitrification, which would help to shorten post-cure time or lower post-temperature. Therefore, overall, silane treatment of COOH-MWCNTs could bring positive effect on the processing of epoxy nanocomposites. Furthermore, it was also found that silane treatment of COOH-MWCNTs does not affect the thermal degradation pattern of COOH-MWCNTs/DGEBA/EMI-2,4 system, how- ever, decreases the thermal stability of COOH-MWCNTs/DGEBA/EMI-2,4 nanocomposites.

DSC and DEA studies of underfill curing kinetics

The classical expression for estimating the polymer‐solvent interaction parameter χ from melting point data of the solvent is refined by considering χ to be concentration‐dependent. Differential scanning calorimetry (DSC) measurements are performed on blends of cis‐polyiso‐prene‐dimethyl terephthalate (DMT) and trans‐polyisoprene–DMT. It is found that the presence of DMT would not affect the DSC events of the polyisoprenes appreciably. However, in both cases, the melting point of DMT decreases, and the rate of depression increases with increasing proportions of polymer. These DSC data are analyzed by the proposed procedure. The results on the interaction energy density parameter are presented as a function of the blend concentration, and rationalized by the specific interactions between different moieties on the component molecules. The limitations of the present technique are discussed.

A novel polyhedral oligomeric octa(propargylaminophenyl)silsesquioxane (OPAPS, (SiO1.5C6H4NHCH2CCH)8) was prepared from octa(aminophenyl)silsesquioxane and propargyl bromide. The chemical structure of OPAPS was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance, X‐ray diffraction (XRD), high‐performance liquid chromatography, gel permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis (TGA). The structure of the thermally cured polymer of OPAPS was characterized by FTIR, XRD, and TGA. It had good thermal stability. TGA demonstrated that the thermal decomposition temperatures (Td5) of the cured OPAPS polymer in nitrogen and air were 455.6 and 458.8°C, respectively. The thermal curing reaction kinetics of OPAPS were studied and some kinetic parameters were obtained. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Objective: Tazarotene is used as a topical retinoid for the treatment of acne, psoriasis and sun-damaged skin. But its topical formulation has many side effects, including itching, burning, dryness, redness, stinging, rash blistering, skin discoloration, peeling at the site of application and low bioavailability. The present study focuses on the reduction of side effects and enhancement of solubility and topical bioavailability of tazarotene by using cyclodextrin-based nanosponges. Methods: Nanosponge of tazarotene were prepared by lyophilization method. The physiochemical characterization of plain nanosponges and drug-loaded nanosponges were performed using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and X-ray Diffractometer (XRD) studies. The drug-loaded nanosponges were incorporated into a carpool-based gel formulation. The prepared formulation was evaluated for viscosity, dissolution and stability. FTIR, DSC and XRD studies confirmed the formation of inclusion complex of tazarotene with nanosponges. Results: The particle size of the drug-loaded nanosponges was found to be in the range of 156.72 to 163.48 nm. Transmission Electron Microscopy (TEM) images revealed the regular spherical shape of both the nanosponges that are unaffected even after drug encapsulation. The pH of the gel formulations was found to be in the range of 5.86 to 6.46. The gel formulation resulted in the diffusion of drug in controlled manner for up to 24 h. The in vitro dissolution studies revealed that nanosponges-based topical formulation had better results than the marketed product. Conclusion: Thus, the study showed that nanosponge-based gel formulation can be a possible alternative to conventional formulations of tazarotene with enhanced bioavailability and skin retention characteristics for topical application.

Poly(ethylene oxide) and its blends with sodium alginate