Molecular Dispersion State Research Articles

Mucoadhesive Dosage form of Lidocaine Hydrochloride: I. Mucoadhesive and Physicochemical Characterization

The aim of this study was to characterize a buccal mucoadhesive film using lidocaine and its hydrochloride salt (LDHCL) as a model drug. Buccal films were developed using carbopol 971P as a mucoadhesive polymer, and glycerol as a plasticizer. Scanning Electron Microscope, Differential Scanning Calorimetry, X-ray powder diffraction, and Fourier Transform Infra Red techniques were used to characterize the mucoadhesive films. Bioadhesive properties were evaluated using the Universal Instron Instrument with chicken pouch as a model tissue. LDHCL and its base were present in carbopol 971P films in a molecular dispersion state without exerting any effect on the glass transition of these films. The mucoadhesive force between the chicken pouches and the film containing glycerol did not change by time during the tested period (1–20 min), while increased with increasing the amount of glycerol (10–40% w/w of polymer content). Furthermore, a linear increase in the mucoadhesive force was accompanied by the increase in the film thickness, while a linear decrease followed by plateau was obtained when loading the patch with LDHCL at concentration above 1 mg/cm2. Loading carbopol film with lidocaine base, in a concentration up to 6 mg/cm2 decreased linearly the mucoadhesive properties, which could be attributed to salt formation between the acidic carboxylic moiety of carbopol and basic lidocaine.

Optical properties of polydimethylphenyleneoxide free-standing films containing fullerene

The interaction of fullerene C60 with poly(2,6-dimethyl)-phenyleneoxide (PPO) in free films was studied by optical methods. The electronic structure of C60 in these polymer films was shown to have two states, with the energy state of C60 bound to PPO being independent of the C60 content. Comparison of the photoluminescence spectra of PPO-C60 and polystyrene-C60 systems makes it possible to assert that the interaction between the components of these systems occurs via π electrons of fullerene and π electrons of benzene rings of the polymers. It is assumed that C60 in the polymer exists in two forms that differ in their electronic structure: a molecular-dispersed state (in the form of complexes with the polymer) and as crystals (aggregates) of fullerene.

Unraveling the Organization of the Internal Nuclear Matrix: RNA-Dependent Anchoring of NuMA to a Lamin Scaffold

Using quantitative immunoelectron microscopy we show here that when the nuclear matrix is isolated from rat hepatocytes in the presence of an inhibitor of RNase activity both lamins and the nuclear mitotic apparatus protein (NuMA) preferentially localize within the electron-dense domains of the internal nuclear matrix (INM). After RNA digestion NuMA undergoes a sharp depletion, while labeling by an antibody against lamins A and C within the electron-transparent regions increases, suggesting that a subset of lamin epitopes is masked by the interaction with RNA. We were able to explain this result by visualizing for the first time a thin web of lamin protofibrils which connects the electron-dense regions. Confirmation of these changes has been obtained by immunoblot analysis and confocal microscopy. As RNA digestion results both in the release of NuMA and in the collapse of the INM, we propose that a fraction of nuclear RNA brings about the association of NuMA islands with a lamin scaffold and that this interaction is required to maintain the latter in a state of high molecular dispersion.

Investigation of a rifampin, fusidic-acid and mupirocin releasing silicone catheter

After strict hygienical measures have been exhausted the use of plastic materials with antibacterial activity may reduce catheter related-bacterial colonization. An antimicrobial silicone catheter was investigated by HPLC-measurement, SEM, antimicrobial assays and standard biocompatibility tests. The modified catheter was highly biocompatible and the antimicrobial leaching non-toxic. The initially release rate was governed by the drug solubility in the ‘sink’ and surface loading (‘burst effect’). The second continuous period depended on the drug velocity in the silicone matrix and was extended up to 100 days with a proportionality to t for each drug. Diffusion exponents were in range of 2×10 -8 to 1×10 -9 (cm 2 sec -1). The lower diffusion exponent of mupirocin was explained by its higher cohesion energy and lower physico-chemical compatibility with the embedding silicone. The antimicrobial drugs were in a molecular-dispersed state with the silicone-matrix, whereas superficially located crystals of the antibiotics covering the catheter surface could be demonstrated by SEM.

Application of the solid dispersion method to the controlled release of medicine. III. Control of the release of slightly water soluble medicine from solid dispersion granules.

In order to control the release rate of slightly water soluble medicine by using the solid dispersion (SD) method, the SD was prepared with a water soluble polymer and the slightly soluble medicine, and the medicine release from the solid dispersion granules was studied. The SD granules were prepared by the evaporation of ethanol after dissolving into ethanol a slightly water soluble medicine (flurbiprofen (FP)) and soluble polymers (hydroxypropyl cellulose (HPC)). HPC has four grades of molecular weight. The release rate of FP from SD was measured by the rotating basket method (JP XII). The release rate of FP from the SD granules was markedly larger than that from FP powder, and it was larger with a lower HPC molecular weight. It is speculated that these results were mainly based on the molecular dispersion state of FP and HPC in SD.

Effect of pH on colloidal properties of native ovalbumin aqueous systems

The effect of pH on the molecular shape and dispersed state of native ovalbumin molecules in 20 mM phosphate and acetic acid buffer solutions has been studied using small-angle x-ray scattering (SAXS) and a rheological method The degree of association of the OA molecule at the 0.5% colloid system increases slightly with decreasing pH, i.e., 2.10 at pH 7.0, and 2.88 at pH 4.0, and the radius of the OA molecule decreases slightly with decreasing pH, i.e., 24.5 A at pH 7.0, and 22.0 A at pH 4.0. The OA colloid shows apparent yield stress and rigidity which are due to a certain ordered arrangement of the molecules. The yield stress and the rigidity increase abruptly at a pH value near to an isoelectric point (ca. pH 4.4). In the dilute system this increment is attributed to the change in the ordered arrangement or in the interparticle interaction, and not to the change in the association state of the OA molecules. The values of the yield stress and the rigidity remain almost constant over a wide concentration range and this feature (an auto-controlled mechanism) is kept over a certain range of pH.

Ibuprofen-loaded ethylcellulose microspheres: Release studies and analysis of the matrix structure through the Higuchi model

The following work deals with ibuprofen-loaded ethylcellulose microspheres. The drug exists either in a state of molecular dispersion or in crystalline form, depending on the encapsulation ratio. The in vitro release profiles have been studied and the Higuchi model applied to the experimental results. With an appropriate treatment of the results, it has been shown that the surface crystals responsible for the observed burst effect are really encapsulated by the polymer. The calculation of the tortuosity factor clearly shows that the release kinetics are controlled by the hydrophobicity of ethylcellulose and the geometry of the porous volume resulting from the dissolution of ibuprofen crystals. It thus appears that crystals are probably differently distributed in the matrix depending on the microsphere size.

Studies of the Aqueous Solution of a Surface Active Substance by Means of an Ultrasonic Interferometer. III. Determinations of Ionic and Nonionic Hydrations of Sodium Alkyl Sulfate

Abstract The amounts of water of ionic and nonionic hydration were calculated for sodium alkyl sulfate in the state of molecular dispersion from the data obtained by the author and under the assumptions usually adopted: (a) the solution, as a whole, consists of several volume elements of different compressibilities; (b) the ionic radical together with its hydration water is incompressible; (c) the compressibility of the water of nonionic hydration for the CH2 group of the hydrocarbon chain is the same as that of ordinary ice; (d) the compressibility and the molar volume of the CH2radical in the state of molecular dispersion are the same as those in the micellar state. The water of hydration was calculated to be 2.1 mole per mole of the CH2 radical, and 4.9 mole per mole of the ionic radical, the latter value being the same as that of the solute in the micellar state previously reported. The molar volume of the water of nonionic hydration is found to be slightly less than that of free water, in accordance with the prediction of others. The dehydration of sodium alkyl sulfate caused by the addition of inorganic electrolyte has also been observed.

The Chemistry of Vulcanization. VII. Role of Zinc Butyrate in the Reaction of Diphenylmethane, Sulfur and 2-Mercaptobenzothiazole

Abstract In previous Parts of this series, the accelerating mechanism of thiazole type accelerators, namely, 2-mercaptobenzothiazole (MBT), 2,2′-benzothiazolyl disulfide (MBTS) and zinc salt of 2-mercaptobenzothiazole (ZMBT) in the absence of zinc oxide or zinc soap, was investigated with diphenylmethane (DPM) as a model compound of rubber hydrocarbon. The significance of DPM as a model was discussed in some of the earlier papers. Parts IV, V and VI of this series indicated that 2-mercaptobenzothiazolyl radical generated from accelerators splits the sulfur ring, and that the processes by which accelerators generate the radical differ with each other according to their types. These results were obtained in the absence of zinc oxide or zinc soap. The present study will report the role of zinc butyrate in the reaction involving DPM, sulfur and MBT. Experience in the industry indicates that zinc oxide (or zinc soap) is indispensable to the thiazole type accelerators and that the efficiency of zinc oxide or soap is more prominent in MBT than in MBTS or ZMBT. The results obtained in the previous papers also suggest that zinc oxide or soap may have an influence on the rate at which the accelerator generates 2-mercaptobenzothiazolyl radical, since it is shown in Parts IV, V and VI that the radical has an accelerating effect. Therefore, it may be considered that zinc oxide or zinc soap activates MBT more effectively than does the other thiazole type accelerators in order to produce this radical. As will be seen later in this study, interaction of MBT with zinc butyrate in the absence of sulfur produces ZMBT and butyric acid. The ZMBT will interact with sulfur and generate the 2-mercaptobenzothiazolyl radical as reported in Part VI. The zinc salt thus formed will be dispersed in a state of molecular dispersion in the reaction system, while the same compound prepared in Part VI was not dissolved in DPM even at the reaction temperatures. In this respect the former is considered more effective than the latter. In order to verify the above assumptions the reaction involving DPM, sulfur and MBT in the presence of zinc butyrate were investigated. The reaction products and mechanism were compared with those in the absence of zinc soap. Since zinc butyrate is soluble in the reaction system at the reaction temperatures, a kinetic study also was carried out and compared with that in the absence of zinc soap.