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Filtrol 13 may be used to dehydrate methyl ricinoleate with simultaneous dimerization and polymerization of the linoleate esters formed. Hydrolysis of the ester group is avoided by the use of xylene as an azeotroping solvent and the preferred method of reaction is the dropwise addition of the ester to a stirred suspension of catalyst in xylene. Products prepared by this technique had a dimer/polymer ratio of about 5 when the yield was 50%. The acid value of the polymer was 7 and of the recovered monomer 3–4.

The phase relationship in ternary mixtures water-gelatin-poly(acrylamide) has been studied performing measurements of cinematic viscosity, gel → sol transition temperature and heat and morphological observations.

Microcapsules were prepared using a poly (L-lactic acid) (L = PLA), mol. wt. 43,200, by an emulsification and solvent evaporation technique. Phenobarbitone (PB) was used as a reference drug, (core to polymer ratio, 1:1). Both the o/w and w/o emulsion system were investigated in order to study microcapsule properties affected by the preparative technique. In the o/w system, dichloromethane (DCM) was used to dissolve L = PLA and PB and the resulting solution was dispersed in 1 per cent aqueous gelatin solution. Subsequent evaporation of the DCM resulted in the formation of microcapsules. PB was found to be poorly encapsulated within microcapsules from this o/w system. PB content in the microcapsules was found to improve using PB saturated aqueous gelatin solution as the continuum. In the w/o system, acetonitrile (AN) was used as a solvent for L-PLA and PB and light liquid paraffin (LLP), containing 2 per cent w/w Span 40, as the continuous phase. PB loading in the microcapsules was found to be very high from this w/o system. Microcapsules from the o/w system were very small compared to microcapsules obtained from the w/o system. The morphology of the microcapsules and the surface properties were found to be affected distinctly by the two techniques. Microcapsules from the o/w system showed a smooth and less porous surface, whereas a highly porous surface containing embedded PB crystals was found in the microcapsules from the w/o system.

Interpolymer complex formation of polyvinylpyrrolidone (PVP) with carboxyvinyl polymer (CP) was examined by turbidity measurement, a binding isotherm study and Fourier-transform infrared spectroscopy. The interpolymer complex of PVP with CP was found to be formed in the unit molecular ratio of 1 : 1 under ideal conditions, though the ratio of PVP in the solid complex was lower than 1 : 1 under practical conditions. Hydrogen bonding might be the driving force for the complexation, and the degree of hydrogen bonding was calculated to be about 40 to 50%.The slowest dissolution rate of chlorpheniramine maleate from tablets, which consisted of a blend of PVP and CP was observed when the polymer combination ratio was 1 : 1. In the case of indomethacin, the longest lag time for the dissolution was observed at the polymer ratio of 1 : 1. Therefore, the drug dissolution behavior from PVP/CP tablets is dependent on the complex formation of PVP and CP.

Theophylline-loaded poly(methyl methacrylate) (PMM) microspheres were prepared by the solvent evaporation method. Increasing the drug to polymer ratio increased both the mean particle size of the microspheres and the release rate. Polyethylene glycol (PEG) 4000 was used to improve the release rate of theophylline from the microspheres. No marked effect was observed on particle size distribution of the microspheres as a function of PEG concentration but there was a pronounced effect on drug release. The different particle sizes of microspheres prepared from the same drug to polymer ratio showed no significant difference in drug content, indicating that the ratio between theophylline and PMM remained practically constant regardless of the size of microspheres. Release characteristics of the microspheres were influenced by drug to polymer ratio, the amount of PEG incorporated and the particle size of microspheres. The release rate was slightly higher in simulated gastric fluid than in simulated intestinal fluid. The release profiles of the drug were modified by mixing microspheres of different formulations in different ratios.

The potential advantages of catalysts in which transition metal complexes are linked to inert supports have been outlined by many authors including ourselves1. Foremost amongst these is the greater ease of separation of the supported catalyst from the reaction mixture, as compared to its homogeneous counterpart. However, whilst some results obtained with supported catalysts have been very encouraging, for example in some instances the presence of the support has increased the specificity of the catalyst2–4, in general the activities of supported catalysts have been lower than those of their homogeneous counterparts. Again there have been exceptions to this5–9, which together with the increased specificity found in certain instances have encouraged an increasing number of workers to join in the search for supported catalysts. It is apparent from previous work that the factors that lead to high activity and high selectivity are generally fairly subtle, so that a large series of closely related, yet each slightly different, supported catalysts is essential if a thorough study is to be made of the factors involved. The technique of γ-irradiation grafting offers a potentially very convenient route for the preparation of such a series of supported catalysts due to the realtive ease with which different amounts of complex can be introduced into different regions of the polymer by modifying the radiation conditions.

The circular dichroism spectra of the poly-L-lysine complexes with abc(–), abd(–), and abd(+)Co(L-ala-O)3 in water and isopropyl alcohol–water (1 : 1), at different pH values and over a range of complex to polymer molar ratios, have been measured. Evidence of a specific site binding is presented for abc(–)Co(L-ala-O)3 in the mixed solvent medium. Of the diastereoisomers used, only in the presence of this material does the macroion assume an α-helical conformation at pH values where the coil form normally predominates. The greater the complex to polymer ratio, the greater the proportion of material of α-helical conformation there is present. Directional modes in the binding, very likely involving hydrogen bonding interactions, are indicated by the changes in the visible c.d. spectra of abc(–)-Co(L-ala-O)3 in PLL-50% isopropyl alcohol solutions. In contrast, the same complex destabilizes the α-helix structure of poly-L-ornithine. All these features are examined in the light of the structural characteristics of the interacting species. The influence of solvent composition is also considered. Implications of the different stereochemical features of abd-diastereoisomers on the association process with the polypeptides are discussed.

Polycarbonate microspheres containing dibucaine were prepared and evaluated as injectable sustained release formulations. Poly (ethylene carbonate) and two lots of poly (ethylene propylene carbonate) were used alone or as mixtures to prepare microspheres. The dibucaine contents of these microspheres were about 27 to 30% when they were prepared at a constant drug/polymer ratio of 30/70. The release rate of dibucaine from the microspheres could be varied by changing the composition of polymer matrices. Therefore, various sustained release patterns of dibucaine were obtainable by the employment of polycarbonate microspheres of different polymer compositions. Three representative preparations of microspheres were examined for local anesthetic effects in guinea pigs. The longest duration of local anesthetic effect was obtained following the implantation of the poly (ethylene propylene carbonate) microspheres with an intermediate release rate of the drug in vitro.

Albumin microcapsules containing sulphadiazine were prepared using a multiple emulsion technique. Heat was utilized to denature the albumin and form the capsule shell. Albumin microcapsules prepared using this technique were free-flowing, spherical in shape, and had varying degrees of vacuolation. The effects of drug: polymer ratio and concentration of cross-linking agent on the percentage of drug retained in the microcapsules and release of drug from the microcapsules were studied. Also, the effect of viscosity of the innermost oil layer, of the multiple emulsion, upon the mean diameter of the microcapsules and release of drug from the microcapsules was investigated.

Experiments were conducted to evaluate the effects of changes in the polymer ratio and environmental conditions on the water vapor transmission properties of plasticized films containing combinations of hydroxypropyl methylcellulose and ethyl-cellulose. Rates of water vapor transmission were calculated from a formula based on Fick's first law of diffusion. Inverse relationships were observed between the rate of water vapor transmission and film thickness for all films studied. In these plasticized systems, the polymer ratio of hydroxypropyl methylcellulose to ethylcellulose produced essentially no difference in the water vapor transmission properties from one film composition to another. Films subjected to a water vapor environment at both film surfaces were more permeable to water vapor than films subjected to a water vapor environment at only one surface. In the thickness range studied, films subjected to 40 and 50° conditions had lower rates of water vapor transmission than those studied at 30°. The findings of this study demonstrated the presence of another mechanism of vapor transmission, in addition to diffusion, that is apparently related to the hydrophilic character of the film.

Both esterand etherbased thermoplastic polyurethane (TPU) nanocomposites were prepared by melt blending, using 3 wt % Cloisite 10A (organically modified montmorillonite clay) as the nanoscale reinforcement. The nanocomposites were subsequently melt-blended with polypropylene (PP) using maleic anhydride grafted polypropylene (MA-g-PP) as a compatibilizer (in the ratio of 70/30TPU nano/PP, 70/25/5-TPU nano/PP/MA-g-PP). Besides giving substantial increase in modulus, tensile strength and other properties organoclay reinforcement functions as a surface modifier for TPU hard segment. X-ray diffraction studies revealed that compatibilization is further improved by introducing functionalized PP (MA-g-PP) in the organoclay containing blends. The blend system was evaluated by DSC, DMA, SEM, mechanical properties and Xray diffraction. The results indicate that the esterTPU exhibited greater miscibility than ether-TPU. Abrasion resistance and water absorption were also better for compatibilised esterTPU blends as compared to the ether-TPU materials. Introduction Recently, polymer/organoclay nanocomposites have been extensively studied and published in the literature. Organically modified nanoclay has been widely used as a reinforcing agent for commercially available polymers like polypropylene (PP), nylon and polyurethane. Some correlations have been established between organoclay loading and the physical, mechanical and thermal properties of the nanocomposites. Depending on the strength of interfacial interactions between the polymer matrix and layered silicate (organoclay), two types of polymer/organoclay nanocomposites are achievable. In intercalated nanocomposites, the insertion of a polymer matrix into the layered silicate structure occurs in a crystallographically regular fashion, regardless of the clay to polymer ratio. In an exfoliated nanocomposite, the individual clay layers are separated in a continuous polymer matrix by an average distance that depends on clay loading. Usually, the clay content of an exfoliated nanocomposite is much lower than that of an intercalated nanocomposite. Polypropylene/organoclay nanocomposites were prepared via direct meltintercalation by using an internal mixer and co-rotating twin screw extruder [1]. The structure of nanocomposites was characterized by X-ray diffraction, transmission electron microscopy and rheometry in small amplitude oscillatory shear. MA-g-PP was used as a compatibilizer to improve the dispersibility of clay in polypropylene. There are several reports of polypropylene-graft-maleic anhydride being used to

The objectives of this study were to prepare microcapsules containing verapamil and propranolol and to evaluate the kinetics and mechanism of drug release from the microcapsules using USP Apparatus 1. The effects of polymer concentration and polymer type on the cumulative amount of drug released were evaluated. The microcapsules were manufactured using Eudragit RS and RL polymers by solvent evaporation with the ultimate aim of prolonging drug release. Twenty-four formulations were prepared using different drug/polymer ratios. The effects of polymer type and polymer/drug ratios on the size, flow properties, surface morphology, and the release characteristics of the microcapsules were examined. The effects of drug inclusion methods on drug loading, encapsulation efficiency, and release properties of the complex microcapsules were also investigated. The formulations containing drug/polymer ratio 1:4 (w/w) were the most appropriate with respect to encapsulation efficiency (70%), flow properties (HR = 1.2), drug loading (15–20%), and drug release characteristics, in all cases. The release kinetics from the different formulations followed mainly a diffusion-controlled mechanism.

In present study, matrix tablets of Omeprazole (OPZ) were formulated by wet granulation technique using a combination of hydroxyl propyl methyl cellulose (HPMC K15M) and ethyl cellulose (EC) in varying ratios and the effect of polymer ratio as well as their concentration on drug release profile was investigated. Response surface methodology (RSM) was conducted to optimize matrix tablets. Compressed tablets were evaluated for hardness, friability, weight variation, drug content and in vitro dissolution studies. The dissolution study was performed in pH1.2 for the first 2 h and in phosphate buffer (pH 7.4) for another 5 h. The optimized formulation was compared with other formulations using similarity (ƒ2) and dissimilarity factor (ƒ1) test. The results of RSM indicated that both X1 (the blending ratio of HPMC K15M K15M and Carbopol 934P 934P) and X2 (polymer blend concentration)have significant effect on in-vitro drug release profile. Hardness, friability, weight variation and drug content were found to be in desired range. Among different formulations, matrix tablets prepared by HPMC K15M and Carbopol 934P 934P (7:3) with 15% polymer blend concentration displayed 98.85% OPZ release in 7 hr. and release kinetic was higuchi (r 2= 0.9884). Similarity (f2) and dissimilarity (f1) factors demonstrated that the in vitro profiles were not similar. Finally, it was concluded that release rate of OPZ decreased proportionally with increasing polymer ratio (HPMC K15M: Carbopol 934P 934P) and decreasing polymer blend concentration.

The aim of this study was the preparation of diclofenac sodium microcapsules using cellulose acetate as a polymer and polyvinyl acohol as an emulsifying agent by solvent evaporation technique. Preliminary experiments were carried out to determine practically the volume range of both the external phase, the internal organic phase, the concentration range of emulsifier and the drug to polymer ratio. The prepared microcapsules were evaluated for their morphology and surface structure, average particle size, yield, drug loading efficiency, and their release pattern. The results of these trials revealed that diclofenac sodium–cellulose acetate microcapsules were successfully prepared applying the solvent evaporation technique. The characteristics of the produced microcapsules were highly affected by the different formulation parameters. Changing the polymer content didn’t affect the morphology of the produced microcapsules. The microcapsules were discrete, spherical and freely flowing. The increase in the polymer amount increased the mean particle size and decreased the yield of the microcapsules due to the increase in the internal phase viscosity. The drug loading efficiency was significantly increased with the increase in methylene chloride–acetone volume. The condensed monolayer of polyvinyl alcohol was not achieved at concentrations below 0.5%. Above this concentration, the increase in polyvinyl alcohol content decreased both the mean particle diameter and the percentage yield of the microcapsules. The release of diclofenac sodium from cellulose acetate microcapsules was pH dependent. The drug was released faster in the alkaline medium compared to acidic medium

Synthetic pseudowollastonite (psW) and a nanostructured copolymer made of a biostable component, Poly(ethylmethacrylate) (PEMA) and a bioresorbable component, vinylpyrrolidone (VP) are used in this work for the preparation of a new family of bone substitutes that allow osseointegration and mechanical stability. Composites are prepared by bulk polymerization of the desired composition in 15 mm diameter cylindrical plastic moulds. Polymerization was induced thermally at 50°C using 1wt% azobis(isobutyronitrile) (AIBN) as free-radical initiator. The moulds were filled to a height of 100 mm and 1 mm height discs were cut with a diamond saw. Specimens with a ceramic/polymer ratio 58/42, 33/67,17/83 and 0/100 were obtained. Compression stress in the range 39-59 MPa and elastic modulus between 2.64 and 4.14 GPa are obtained where the greater values correspond to the specimens prepared with a 60% ceramic load. Degradation in SBF produces a porous nanostructure in the polymeric component indicating microdomains of different solubility and the formation of an apatite-like layer on the surface of the wollastonite component. All the compositions assayed present a biocompatibility at least of the level or even superior than the Thermanox® control used.

The purpose of research was to develop a mucoadhesive multiparticulate sustained drug delivery system of pravastatin sodium, a highly water-soluble and poorly bioavailable drug, unstable at gastric pH. Mucoadhesive microparticles were formulated using eudragit S100 and ethyl cellulose as mucoadhesive polymers. End-step modification of w/o/o double emulsion solvent diffusion method was attempted to improve the purity of the product, that can affect the dose calculations of sustained release formulations and hence bioavailability. Microparticles formed were discrete, free flowing, and exhibited good mucoadhesive properties. DSC and DRS showed stable character of drug in microparticles and absence of drug polymer interaction. The drug to polymer ratio and surfactant concentration had significant effect on mean particle size, drug release, and entrapment efficiency. Microparticles made with drug: eudragit S100 ratio of 1:3 (F6) exhibited maximum entrapment efficiency of 72.7% and ex vivo mucoadhesion time of 4.15 h. In vitro permeation studies on goat intestinal mucosa demonstrated a flux rate (1,243 μg/cm(2)/h) that was 169 times higher than the flux of pure drug. The gastric instability problem was overcome by formulating the optimized microparticles as enteric-coated capsules that provided a sustained delivery of the highly water-soluble drug for 12 h beyond the gastric region. The release mechanism was identified as fickian diffusion (n = 0.4137) for the optimized formulation F6. Conclusively, a drug delivery system was successfully developed that showed delayed and sustained release up to 12 h and could be potentially useful to overcome poor bioavailability problems associated with pravastatin sodium.

Calcium alginate microdiscs were prepared by the gelification technique using sodium alginate as the precursor hydrophilic polymer and calcium chloride aqueous solution (1% w/v) as the cross-linking agent. Indomethacin, the model drug, was simultaneously encapsulated in the cross-linked swellable calcium alginate matrix. It was found that as the sodium alginate concentration was increased in the cross-linking reaction, there was a marked increase in drug entrapment capacity of the calcium alginate microdiscs. The 1% w/v indomethacin-calcium alginate microdisc formulation maximally entrapped 43.84% drug, while the 4% w/v formulation retained 92.18% drug. In addition, indomethacin release in phosphate buffer, pH 6.2, was markedly decreased as the precursor polymeric concentration was increased. The t(80%) for the 1% w/v formulation was approximately 3 h, while this value was extrapolated to 13.5 h for the 4% w/v formulation. A 1:1 combination of the 2 and 3% w/v formulations of the indomethacin-calcium alginate microdiscs provided bimodal, biphasic drug release characteristics similar to Indocid-R capsules. With the aid of scanning electron microscopy, it was demonstrated that the microdisc diameter also increased as the polymer concentration was increased. For example, the 1 and 4% w/v formulations had mean diameters of 1.26 and 2.17 mm, respectively. The micrographs also elucidated typical pore formation on the surface of the indomethacin-calcium alginate micro-discs, which suggested that the drug release mechanism is governed by swelling/erosion as well as partial diffusion. Density and surface area measurements of the indomethacin-calcium alginate microdiscs revealed that both dimensional characteristics decreased with increasing sodium alginate concentrations. A change in the drug:polymer ratio (1:1, 1:2, 1:2.5, 1:3, and 1:4) also resulted in microdiscs with higher potencies and slower dissolution rates. The above 4% w/v microdisc formulation was similar to the formulation containing the 1:4 drug:polymer fraction, in that both formulations were prepared from a 4% w/v sodium alginate solution. However, changing the polymer fraction proved more effective in decreasing the release of indomethacin from the calcium alginate microdiscs.

Gantrez AN nanoparticles can be obtained by desolvation of the poly(anhydride) with an aqueous medium, followed by a purification step and freeze-drying. In order to simplify this method, a spray-drying procedure was evaluated here. For this purpose, suspensions of nanoparticles were mixed with carbohydrates before their drying. Lactose, in a saccharide/polymer ratio of 2, was found to be the most suitable excipient regarding the physicochemical characteristics and stability of the resulting nanoparticles. These conditions can be successfully applied to the preparation of conventional, combined cyclodextrin/polyanhydride or pegylated nanoparticles. The capabilities of the new procedure were also studied by the characterization of nanoparticles loaded with either an antigenic extract (HS from Brucella ovis) or atovaquone. In all cases, the new formulations displayed similar physico-chemical characteristics to those of nanoparticles obtained by lyophilization. In summary, the spray-drying procedure can be an adequate alternative to lyophilization in the preparative process of poly(anhydride) nanoparticles.

Buoyant beads enclosing furosemide were prepared by cross-linking chitosan with dioctyl sodium sulphosuccinate (DOSS) and characterized according to: entrapment efficiency, in vitro release, in vitro and in vivo buoyancy. The effect of various factors (DOSS and chitosan concentrations, drug: polymer ratio and loading technique) on bead properties were assessed. Interaction between chitosan and DOSS was evaluated by DSC and FTIR. SEM demonstrated that the dried beads were spherical in shape with an inward cavity enclosing furosemide in the range of 1.8-62.25 %. Most beads floated over SGF for 12 h. Beads retarded the release of furosemide compared to pure drug powder and Lasix tablets. The t 50 % ranged from 1.79-4.1 h and release followed zero or diffusion kinetics. Beads remained buoyant in the stomach of dogs for 6 h. Beads were stable at 40 °C and 75 % RH for 3 months. Results showed that chitosan beads proved to be effective carrier for furosemide, maximizing its therapeutic effect at the site of absorption in a controlled release pattern.

psyllium, a medicinally active gel forming natural polysaccharide and a dietary fiber has been used as a medicine in myriad of conditions such as constipation and inflammatory bowel syndrome. One of its more recent uses that have received attention has been its ability to reduce blood sugar levels in diabetics. Therefore present work is an attempt to formulate anti diabetic drug Metformin as a controlled release floating delivery making use of pysllium as release retardant and to assist the drug in stabilizing blood sugar level in type II diabetics. Drug and excipients compatibility studies were monitored by thermal analysis using differential scanning calorimeter (DSC) and Fourier transform infra red (FTIR). The DSC thermogram and FTIR of drug and drug-polymer mixture did not reveal any incompatibility. psyllium was tried in different concentrations along with other polymers like HPMC K15M and carbopol 940 to achieve the desired release profile. The total drug: polymer ratio was kept between 1:0.4 to 1:0.5, and different polymer combinations were tried to achieve desired drug release for 12 hours. The prepared tablets were evaluated for in vitro release studies and floating behavior. Our conclusion from the present study indicated that pysllium could potentially be used in conjunction with other polymers to formulate controlled release formulations of anti-diabetic drugs to provide better control over blood glucose levels.

The circular dichroism spectra of the poly-L-lysine complexes with abc(–), abd(–), and abd(+)Co(L-ala-O)3 in water and isopropyl alcohol–water (1 : 1), at different pH values and over a range of complex to polymer molar ratios, have been measured. Evidence of a specific site binding is presented for abc(–)Co(L-ala-O)3 in the mixed solvent medium. Of the diastereoisomers used, only in the presence of this material does the macroion assume an α-helical conformation at pH values where the coil form normally predominates. The greater the complex to polymer ratio, the greater the proportion of material of α-helical conformation there is present. Directional modes in the binding, very likely involving hydrogen bonding interactions, are indicated by the changes in the visible c.d. spectra of abc(–)-Co(L-ala-O)3 in PLL-50% isopropyl alcohol solutions. In contrast, the same complex destabilizes the α-helix structure of poly-L-ornithine. All these features are examined in the light of the structural characteristics of the interacting species. The influence of solvent composition is also considered. Implications of the different stereochemical features of abd-diastereoisomers on the association process with the polypeptides are discussed.