Surface Of Microcrystalline Cellulose Research Articles

Raman spectroscopic surface characterization of cellulose derivatives.

First results of experiments on the surface characterization of cellulose derivatives are presented. Different water contents of the surface of microcrystalline cellulose have been investigated by means of Raman spectroscopy, SERS, and environmental scanning electron microscopy (ESEM).

A técnica da reflectância difusa aplicada ao estudo da fluorescência de 2,3-naftalimidas n-substituídas com grupos alquila incluídas em <FONT FACE=Symbol>b</font>-ciclodextrina e adsorvidas em celulose microcristalina

The solution fluorescence of N-alkyl-2,3-naphthalimides (1-4) in polar protic and aprotic solvents was compared to the emission from solid samples resulting from the imide complexation with b-cyclodextrin or adsorption on the surface of microcrystalline cellulose. Solid samples of the inclusion complex 2,3-naphthalimides/b-cyclodextrin show maximum for fluorescence emission significantly different to the observed in methanolic solution. Beside this, a clear effect on the alkyl chain length could be observed for these samples which is probably due to differences in probe location inside the cyclodextrin cavity. The constancy for fluorescence quantum yield and fluorescence lifetime for the imides 1 - 4 adsorbed on microcrystalline cellulose suggests that, independently of the polarity of the solvent used for sample preparation, the probe is preferentially located on the cellulose surface. An increase of fluorescence quantum yield and fluorescence lifetime for solid samples, when compared to the values obtained in solution for the different solvents employed in this study (acetonitrile, methanol and water), is fully in accordance with a decrease of the probe mobility due to inclusion in b-cyclodextrin or to adsorption on cellulose.

Studies on Internal Structure of Tablets. Part VIII. Melting Granulation by Addition of Polyethyleneglycol for Stabilization of TAT-59.

Compatibility of (E)-4-[1-[4-[2-(dimethylamino)ethoxy]phenyl]-2-(4-isopropylphenyl)-1-butenyl]phenyl monophosphate, TAT-59, with excipients was studied by using a powder mixture, a tablet obtained by compressing the powder mixture and powder obtained by crushing the tablet. TAT-59 with excipients of kinds of cellulose, sugar and starch degraded, whereas TAT-59 with polyethyleneglycol 6000 (PEG6000) was stable. Stability of the tablet consisting of TAT-59 and microcrystalline cellulose (MCC) obtained by the direct compression method (T-TM), the tablet consisting of TAT-59, MCC and PEG6000 by the direct compression method (T-TMP) and the tablet consisting of TAT-59, MCC and PEG6000 by the melting granulation method (T-MG) was evaluated by determining the formation of its hydrolysis product, DP-TAT-59. The degradation rate decreased in the order: T-TM> T-TMP>T-MG. Thus, the melting granulation method with the addition of PEG6000 was found to stabilize the tablet containing TAT-59. The reason for the stabilization was presumably that the contact between TAT-59 and the water vapor or the water in MCC was decreased by coating the surface of TAT-59 and MCC with PEG6000, and that the phosphate group of TAT-59 was stabilized for the hydrogen bonding with PEG6000. Furthermore, the water-soluble PEG6000 little affected the dissolution profile of TAT-59, showing the melting granulation method can be useful for the stabilization of TAT-59.

Binding of the cellulose-binding domain of exoglucanase Cex from Cellulomonas fimi to insoluble microcrystalline cellulose is entropically driven.

Isothermal titration microcalorimetry is combined with solution-depletion isotherm data to analyze the thermodynamics of binding of the cellulose-binding domain (CBD) from the beta-1,4-(exo)glucanase Cex of Cellulomonas fimi to insoluble bacterial microcrystalline cellulose. Analysis of isothermal titration microcalorimetry data against two putative binding models indicates that the bacterial microcrystalline cellulose surface presents two independent classes of binding sites, with the predominant high-affinity site being characterized by a Langmuir-type Ka of 6.3 (+/-1.4) x 10(7) M-1 and the low-affinity site by a Ka of 1.1 (+/-0.6) x 10(6) M-1. CBDCex binding to either site is exothermic, but is mainly driven by a large positive change in entropy. This differs from protein binding to soluble carbohydrates, which is usually driven by a relatively large exothermic standard enthalpy change for binding. Differential heat capacity changes are large and negative, indicating that sorbent and protein dehydration effects make a dominant contribution to the driving force for binding.

Effects of compression pressure on physical and chemical stability of tablets containing an anticancer drug TAT-59.

(E)-4-[1-[4-[2-(Dimethylamino)ethoxy]phenyl]-2-(4-isopropyl) phenyl]-1-butenyl]phenyl monophosphate (TAT-59) is a new drug for the treatment of breast cancer. Physical and chemical stability of mixtures of TAT-59 and microcrystalline cellulose (1:9) compressed at 0, 300, 600 and 1400 kg/cm2 was evaluated by determination of water content, porosity and the amount of hydrolysis product, DP-TAT-59, formed. The water contents and porosity of these tablets scarcely changed during 57 d at 25-60 degrees C under 50% relative humidity (RH). The degradation rate of TAT-59 increased with increasing compression pressure as well as temperature. The apparent activation energy and frequency factor were determined from an Arrhenius plot of the degradation rate. Activation energy of these tablets was almost the same, while the frequency factor tended to increase with increasing compression pressure. The porosity and pore sizes in TAT-59-containing tablets decreased with increasing compressive force. We speculated from these observations that the increase in compression pressure decreased the distance and increased the contact area between TAT-59 and microcrystalline cellulose. The proximity between TAT-59 and moisture presented at the surface of microcrystalline cellulose by compression was considered to enhance the degradation of TAT-59.

PHOTOCHEMISTRY ON SURFACES: TRIPLET‐TRIPLET ENERGY TRANSFER ON MICROCRYSTALLINE CELLULOSE STUDIED BY DIFFUSE REFLECTANCE TRANSIENT ABSORPTION and EMISSION SPECTROSCOPY*

AbstractTriplet‐triplet energy transfer has been studied between benzophenone and an oxazine dye (2,7‐bis(diethyl‐amino)‐phenazoxonium chloride) co‐adsorbed on the surface of microcrystalline cellulose. Ground state absorption and fluorescence measurements provide evidence for dimer formation of the oxazine dye when adsorbed on cellulose in contrast to the behaviour in ethanol solution where no dimerization is observed. The equilibrium constant for dimerization, which is found to be (1.0 × 0.1) × 106 mol−1 g (2560 × 250 dm3 mol−1) for oxazine alone on cellulose decreases in the presence of co‐adsorbed benzophenone. Fluorescence is detected from excited monomeric but not from excited dimeric oxazine. The absorption spectrum of the triplet state of oxazine adsorbed on cellulose was obtained and its extinction coefficient evaluated relative to that of triplet benzophenone which was used as a sensitizer. The lifetime of adsorbed triplet oxazine is 4.3 ms which is 300 times longer than that in acetonitrile solution.The efficiency of energy transfer from triplet benzophenone to oxazine on cellulose was studied using both time resolved sensitized absorption and phosphorescence intensity measurements as a function of oxazine concentration. Lifetime measurements show that the energy transfer process involves static quenching since the benzophenone lifetime is independent of oxazine loading at the surface. A mechanism is proposed to explain the results in which one oxazine molecule is suggested as being able to quench phosphorescence from a “pool” consisting of 2 to 3 benzophenone molecules.

The Interaction Between Cibacron® Blue 3G‐A Dyed Amyloses and Microcrystalline Cellulose

AbstractIt has been shown with the aid of chemical analysis, gel permeation chromatographic analysis of malto‐oligosaccharide mixtures produced by the action of α‐amylase (1, 4,‐α‐D‐glucan glucanohydrolase, E. C. 3. 2. 1. 1.) and photomicroscopy, that dyed amylosic fragments, produced by the conventional action of α‐amylase on Cibacron® Blue 3G‐A dyed amylose substrates, can become adsorbed by microcrystalline cellulose. The adsorption occurs between the aromatic residues of the dye molecule and the surface of microcrystalline cellulose, and only when the amount of solubilisation of the dyed amylose substrate is high. Thus, under these circumstances erroneously low values for α‐amylase activity will be obtained when using such a chromogenic substrate due to adsorption of soluble dyed fragments onto the surface of microcrystalline cellulose, thereby escaping detection. When α‐amylase levels are low, thereby causing little solubilisation of the dyed substrate, as is frequently the case in clinical chemistry, the amount of absorption cannot be detected and therefore the use of microcrystalline cellulose as a tablet binder to facilitate the routine use of these dyed amylose chromogenic substrates is permissible.