Blends Of Ethylcellulose Research Articles

Characterization of ethylcellulose: starch-based film coatings for colon targeting

Background: The site-specific delivery of drugs to the colon can be highly advantageous for various applications, including the local treatment of inflammatory bowel diseases. The aim of this study was to provide efficient tools that can be used to easily adjust the key properties of novel polymeric film coatings allowing for colon targeting. Methods: Free films based on blends of ethylcellulose and different types of starch derivatives (partially being pregelatinized, acetylated, and/or hydroxypropylated) were prepared and characterized. Results: The key properties of the polymeric systems can effectively be adjusted by varying the polymer blend ratio and type of starch derivative. This includes the water uptake and dry mass loss kinetics as well as the mechanical properties of the films before and upon exposure to aqueous media simulating the contents of the upper GIT. Conclusion: Broad ranges of film coating properties can easily be provided, being adapted to the needs of the respective drug treatment.

Novel polymeric film coatings for colon targeting: Drug release from coated pellets

The aim of this study was to prepare and characterize novel types of polymer coated pellets allowing for the site-specific delivery of drugs to the colon. 5-Aminosalicylic acid (5-ASA)-loaded beads were prepared by extrusion–spheronization and coated with different Nutriose:ethylcellulose blends. In vitro drug release from these systems was measured under various conditions, including the exposure to fresh fecal samples from inflammatory bowel disease patients under anaerobic conditions. Nutriose is a starch derivative, which is preferentially degraded by enzymes secreted by the microflora in the colon of Crohn's disease and ulcerative colitis patients. Interestingly, the release of 5-ASA (which is commonly used for the local treatment of inflammatory bowel diseases) could effectively be suppressed upon exposure to release media simulating the conditions in the upper GIT, irrespective of the degree of agitation and presence or absence of enzymes. But as soon as the pellets came into contact with fecal samples of inflammatory bowel disease patients, the release rate significantly increased and the drug was released in a time-controlled manner. Thus, this novel type of colon targeting system is adapted to the pathophysiology of the patient. Furthermore, culture media containing specific colonic bacteria are presented providing an interesting potential as substitutes for fresh fecal samples.

Preparation a novel pH‐sensitive blend hydrogel based on polyaspartic acid and ethylcellulose for controlled release of naproxen sodium

AbstractHydrogels based on pH‐sensitive polymers are of great interest as potential biomaterials for the controlled delivery of drug molecules. In this study, a novel, pH‐sensitive hydrogel was synthesized by poly(aspartic acid) (PASP) crosslinked with 1,6‐hexanediamine and reinforced with ethylcellulose (EC). The loading and release characteristics of naproxen sodium (NS) were studied. The PASP–EC blend hydrogels had pH‐sensitive characteristics and were strongly dependent on the pH value. The release kinetics for NS from the PASP–EC blend hydrogels and PASP hydrogel were evaluated in simulated gastric fluid (pH = 1.05) and simulated intestinal fluid (pH = 6.8) at 37°C. The results showed that the drug‐loaded hydrogels were resistant to simulated gastric fluid, and hence, they could be useful for oral drug delivery. Compared with the PASP hydrogel, the PASP–EC blend hydrogels showed a lower release rate of NS in the same pH conditions. It was evident that the presence of hydrophobic groups (EC) retarded the release of NS and led to sustained release. The kinetics of NS release from the drug‐loaded hydrogels conformed to the Korsmeyer–Peppas model. The release exponent of the model was 0.7291, which indicated multiple drug release. The PASP–EC blend hydrogels were biodegradable and pH sensitive; there would be a wide range of applications for them in controlled drug‐delivery systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Novel polymeric film coatings for colon targeting: How to adjust desired membrane properties

The major aim of this work was to optimize the properties of novel polymeric films based on blends of ethylcellulose and Nutriose (a water-soluble, branched dextrin). Such blends were recently shown to be highly promising for the site-specific delivery of drugs to the colon in patients suffering from inflammatory bowel diseases, in particular Crohn’s disease and ulcerative colitis. Importantly, and in contrast to various other colon targeting approaches, the system is adapted to the pathophysiological conditions in the disease state. However, it is yet unknown how desired membrane properties, especially water uptake and dry mass loss kinetics as well as mechanical stability can be adjusted to the specific needs of particular drug treatments. Different highly efficient and easy to apply tools were identified altering the membrane’s properties, in particular their mechanical resistance required to withstand the shear forces resulting from the motility of the upper GIT and the hydrostatic pressure built up within the devices upon contact with aqueous media. This includes the variation of the Nutriose:ethylcellulose blend ratio and initial plasticizer content. Importantly, Nutriose also exhibits significant pre-biotic activity, normalizing the microflora in the patients’ colon, which is of major clinical benefit in the case of inflammatory bowel diseases.

Pervaporation properties of EC membranes modified by aliphatic hyperbranched polyester

Pervaporation membranes containing hyperbranched polymer were prepared from the blends of ethyl cellulose (EC) and hyperbranched polyester (HBPE). The FT-IR analysis indicated that the interactions between EC and HBPE decreased as increasing the generation of HBPE. The membrane containing HBPE (EC-HBPE) showed both higher sorption ratio and selectivity than pure EC membrane. The effects of HBPE content as well as temperature of feed solutions on the membrane performance were investigated in detail. The EC-HBPE membrane exhibited much higher permeate flux than the EC membrane, while the separation factor maintained at same level.

Effect of the content of ethyl cellulose-rubber blend on physicochemical properties of adhesive compositions

Results of comprehensive systematic physicochemical studies of the blends of ethyl cellulose and butadiene-acrylonitrile rubbers are reported. It is shown that the addition of butadiene-acrylonitrile rubbers to ethyl cellulose results in the formation of ethyl cellulose-butadiene-acrylonitrile rubber thermoelastoplastic complexes due to the elastification of the thermoplastic polymorphous structure of ethyl cellulose with enhanced impact strength and heat resistance.

Drug release and swelling kinetics of directly compressed glipizide sustained-release matrices: Establishment of level A IVIVC

The purpose of this study was to examine a level A in vitro–in vivo correlation (IVIVC) for glipizide hydrophilic sustained-release matrices, with an acceptable internal predictability, in the presence of a range of formulation/manufacturing changes. The effect of polymeric blends of ethylcellulose, microcrystalline cellulose, hydroxypropylmethylcellulose, xanthan gum, guar gum, Starch 1500, and lactose on in vitro release profiles was studied and fitted to various release kinetics models. Water uptake kinetics with scanning electron microscopy (SEM) was carried out to support the drug release mechanism. An IVIVC was established by comparing the pharmacokinetic parameters of optimized (M-24) and marketed (Glytop-2.5 SR) formulations after single oral dose studies on white albino rabbits. The matrix M-19 (xanthan:MCC PH301 at 70:40) and M-24 (xanthan:HPMC K4M:Starch 1500 at 70:25:15) showed the glipizide release within the predetermined constraints at all time points with Korsmeyer–Peppas' and zero-order release mechanism, respectively. Kopcha model revealed that the xanthan gum is the major excipient responsible for the diffusional release profile and was further supported by SEM and swelling studies. A significant level A IVIVC with acceptable limits of prediction errors (below 15%) enables the prediction of in vivo performance from their in vitro release profile. It was concluded that proper selection of rate-controlling polymers with release rate modifier excipients will determine overall release profile, duration and mechanism from directly compressed matrices.

Controlled release of diclofenac sodium and ibuprofen through beads of sodium alginate and hydroxy ethyl cellulose blends

AbstractControlled release of diclofenac sodium (DS) and ibuprofen (IB) drugs through sodium alginate (NaAlg)‐hydroxy ethyl cellulose (HEC) blend polymeric beads has been investigated. Beads were prepared by precipitating the viscous solution of NaAlg and HEC blend in alcohol followed by crosslinking with calcium chloride. Different formulations were developed in bead form by varying the amount of HEC, crosslinking agent, and drug concentration. Swelling studies in water, percent encapsulation of drugs, and release studies were carried out. The DS‐loaded beads have shown better release performance than the IB‐loaded beads. Diffusion parameters were evaluated from the Fickian diffusion theory. Mathematical modeling studies and drug release characteristics through bead matrices were studied by solving Fick's diffusion equation. The results are discussed in terms of drug release patterns and theoretical concentration profiles generated through matrices, considering spherical geometry of the beads. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5708–5718, 2006

Thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure of poly(propylene carbonate)/ethyl cellulose blends

AbstractMaleic anhydride end capped poly(propylene carbonate) (PPC‐MA) was blended with ethyl cellulose (EC) by casting from dichloromethane solutions. The thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure were investigated by differential scanning calorimetry (DSC), thermogravimetry (TGA), and wide angle X‐ray diffraction (WAXD). DSC exhibits thermotropic liquid crystallinity in the rich EC composition range. TGA shows that thermal decomposition temperatures were elevated upon interfusing EC into PPC‐MA. WAXD corroborates that EC and PPC‐MA/EC blend films cast from dilute dichloromethane solution possessed cholesteric liquid crystalline structure in the rich EC composition range, and that dilution of PPC‐MA with EC increased the dimension of noncrystalline region, leading to a more ordered packed structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 584–592, 2006

Polymer blends used for the aqueous coating of solid dosage forms: importance of the type of plasticizer

The aim of this study was to investigate the importance of the type of plasticizer in polymer blends used for the coating of solid dosage forms, comparing a lipophilic and a hydrophilic plasticizer (dibutyl sebacate (DBS) and triethyl citrate (TEC)). In vitro drug release from propranolol hydrochloride (propranolol HCl)-loaded pellets coated with blends of ethyl cellulose (EC) and Eudragit® L (100:0, 75:25, 50:50, 25:75 and 0:100 w/w) was investigated at low as well as at high pH. To better understand the underlying mass transport mechanisms, the physicochemical properties of the film coatings (e.g. mechanical resistance, water uptake and dry weight loss behavior) were determined. Interestingly, drug release strongly depended on the type of plasticizer. Importantly, not only the slope but also the shape of the release curves was affected, indicating that the chemical nature of the plasticizer plays a major role for the underlying drug release mechanisms. Diffusion through the intact polymer coatings and/or through water-filled cracks was found to be dominating for the control of drug release. The relative importance of these pathways strongly depended on the polymer blend ratio and type of plasticizer. In contrast to DBS, TEC rapidly leached out of the coatings, resulting in decreasing mechanical resistances of the films and, thus, facilitated crack formation. In addition, the hydrophilicity of the plasticizer significantly affected the water uptake behavior of the film coatings and, hence, changes in the coatings' toughness and drug permeability. Also the relative affinity of the plasticizer to the different polymers was found to be of significance. In contrast to TEC, DBS has a higher affinity to EC than to Eudragit® L, resulting in potential redistributions of this plasticizer within the polymeric systems and changes in the release profiles during storage. Importantly, these effects could be avoided with appropriate curing conditions and preparation techniques for the coating dispersions.

Cellulose acetate trimellitate ethylcellulose blends for non-steroidal anti-inflammatory drug (NSAID) microspheres

Ketoprofen (Ket), a non-steroidal anti-inflammatory drug, has been incorporated into polymeric micromatrices (microspheres) prepared by a spray drying process and made of cellulose acetate trimellitate (CAT)/ethylcellulose (EC) blends. Drug loaded microspheres were obtained by spray-drying organic solutions of the two polymers and the drug. Characterization of the microparticles (morphology, particle size distribution, drug content, yield of production, surface properties, solvent residues) was carried out and in-vitro release behaviour measured. The release rate of the drug diminished as the proportion of EC was raised.

Polymer blends based on bacterial poly(3-hydroxybutyrate)

The phase behavior of blends of bacterial poly(3-hydroxybutyrate) (PHB) with highly substituted cellulose esters (CEs), polymethylmethacrylate (PMMA), polycyclohexylmethacrylate (PCHMA), ethylcellulose (EtC), and polyepichlorohydrin (PEC) is discussed on the basis of dynamic mechanical, calorimetric, and optical microscopy results. PHB is miscible in the melt in all proportions with CEs and PEC, is partially miscible with PMMA, and is totally immiscible with EtC and PCHMA. The rate and extent of biodegradation in activated sludge of immiscible PHB–EtC blends strongly depends on phase distribution, which is in turn dictated by composition and blending conditions. Miscible PHB–CE and PHB–PEC blends containing 80% PHB show analogous spherulitic morphology, but behave very differently in activated sludge. The blend containing PEC shows weight loss and surface erosion upon sludge exposure, whereas the one containing CE does not biodegrade over a period of 12 months. It is suggested that mobility of the amorphous mixed phase is an important parameter in determining biodegradability of miscible PHB-based blends.Key words: poly(3-hydroxybutyrate), blends, miscibility, biodegradation, morphology.

The morphology of blends of ethylcellulose with hydroxypropyl methylcellulose as used in film coating

Near-equilibrium morphologies of thin films (< 0.2 μm) of ethylcellulose-rich incompatible blends of ethylcellulose (EC) with hydroxypropyl methylcellulose (HPMC) consist of HPMC-rich macroscopic polydisperse domains (3-approx. 20 μm) dispersed in an EC-rich matrix implying complete leaching of the water soluble phase. However, for thick films (> 100 μm) complete leaching was observed only for systems with above 60% w/w HPMC, whereas all other systems showed some HPMC retention. The observed HPMC leaching behaviour is attributed to deviations of the phase decomposition from equilibrium during film formation arising from the rate of viscosity increase and changes in the solvent system composition.

A study of the leaching/retention of water-soluble polymers in blends with ethylcellulose using torsional braid analysis

The leaching/retention of a variety of aqueous soluble polymers from blends with ethylcellulose has been studied using combined torsional braid analysis and gravimetric analysis. Interactions between the two blend components in conjunction with related morphological features produced retention all through the composition range for blends of ethylcellulose with hydroxypropyl methylcellulose phthalate, cellulose acetate phthalate and hydroxypropyl cellulose. In the case of ethylcellulose/hydroxypropylmethylcellulose blends retention only occurs at high ethylcellulose concentrations because of the protective action of the ethylcellulose matrix on the dispersion of the water-soluble component. Complete leaching of polyethylene glycol 6000 occurs except in compositions with small amounts of ethylcellulose where there is an increased molecular attraction.

Polymer/polymer interaction in blends of ethyl cellulose with both cellulose derivatives and polyethylene glycol 6000

Polymer/polymer interactions in blends of ethyl cellulose with hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose phthalate, cellulose acetate phthalate and polyethylene glycol 6000 have been studied using the torsional braid pendulum. All the film formers were shown to be incompatible with ethyl cellulose exhibiting phase separation throughout the composition range. However, some interaction via the unsubstituted hydroxyl groups did occur, with hydroxypropyl methylcellulose with its increased substitution showing slightly reduced interaction. Both grades of hydroxypropyl methylcellulose phthalate and cellulose acetate phthalate exhibited appreciable interaction and mutual dispersion due to the presence of phthalyl groups. The results are extremely important in understanding the transport mechanisms of such blends when used in pharmaceutical formulations for controlled release.