Effect Of Polymer Type Research Articles

Formulation of venlafaxine for once daily administration using polymeric material hybrids

Objective: Controlled release venlafaxine for once daily administration.Methods: Drug resin complexation followed by polymer encapsulation. A 41.21 factorial design was used to study the effect of polymer type and core: coat ratio on the release profile and kinetics. Polymer combinations were tried for optimisation adapting the desIMNCility function. The optimised formula was tested in rabbits against commercial extended release capsules.Results: Poly-epsilon-caprolactone, poly(d, l-lactide-co-glycolide) ester and poly(d, l-lactide) ester polymers were more efficient in lowering the release rate and the initial burst release than Eudragit®RS100. Encapsulation at 1:1 ratio ensured complete coats and drug release sustainment. Formula prepared using 50:50 PLA/Eudragit at 1:1 ratio sustained the drug release up to 24 h with low burst release. This formula had higher venlafaxine absorption in rabbits compared to the commercial capsules.Conclusions: The optimised formula is superior to the available once-daily trials regarding enhanced bioavailability, dosage form versatility and ease of scaling up.

Investigation of the adsorption of polymer chains on amine-functionalized double-walled carbon nanotubes

Molecular dynamics (MD) simulations were used to study the adsorption of different polymer chains on functionalized double-walled carbon nanotubes (DWCNTs). The nanotubes were functionalized with two different amines: NH2 (a small amine) and CH2-NH2 (a large amine). Considering three different polymer chains, all with the same number of atoms, the effect of polymer type on the polymer-nanotube interaction was studied. In general, it was found that covalent functionalization considerably improved the polymer-DWCNT interaction. By comparing the results obtained with different polymer chains, it was observed that, unlike polyethylene and polyketone, poly(styrene sulfonate) only weakly interacts with the functionalized DWCNTs. Accordingly, the smallest radius of gyration was obtained with adsorbed poly(styrene sulfonate). It was also observed that the DWCNTs functionalized with the large amine presented more stable interactions with polyketone and poly(styrene sulfonate) than with polyethylene, whereas the DWCNTs functionalized with the small amine showed better interfacial noncovalent bonding with polyethylene.

Extended release microparticle-in-gel formulation of octreotide: Effect of polymer type on acylation of peptide during in vitro release

Polymeric microparticles (MPs)-in-gel formulations for extended delivery of octreotide were developed. We investigated influence of polymer composition on acylation of octreotide and kinetics of release during in vitro release from biodegradable polymeric formulations. Polycaprolactone (PCL), polylactic acid (PLA), polyglycolic acid (PGA) and polyethylene glycol (PEG) based triblock (TB≈PCL10k-PEG2k-PCL10k) and pentablock (PBA≈PLA3k-PCL7k-PEG2k-PCL7k-PLA3k and PBB≈PGA3k-PCL7k-PEG2k-PCL7k-PGA3k) polymers were investigated. Octreotide was encapsulated in MPs using methanol–oil/water emulsion solvent evaporation method. The particles were characterized for size, morphology, encapsulation efficiency, drug loading and in vitro release. Release samples were subjected to HPLC analysis for quantitation and HPLC-MS analysis for identification of native and chemically modified octreotide adducts. Entrapment efficiency of methanol-oil/water method with TB, PBA and PBB polymers were 45%, 60%, and 82%, respectively. A significant fraction of released octreotide was acylated from lactide and glycolide based PBA (53%) and PBB (92%) polymers. Substantial amount of peptide was not released from PBB polymers after 330 days of incubation. Complete release of octreotide was achieved from TB polymer over a period of 3 months with minimal acylation of peptide (13%). PCL based polymers resulted in minimal acylation of peptide and hence may be suitable for extended peptide and protein delivery. Conversely, polymers having PLA and PGA blocks may not be appropriate for peptide delivery due to acylation and incomplete release.

A conceptual model to understand the correlation between topography and wetting of polypropylene- and polyethylene-based wood–plastic composites

Microscopic and physico-chemical methods were used for a comprehensive surface characterization of different extruded polypropylene- and polyethylene-based wood–plastic composite (WPC) formulations. The surfaces were analysed using stereophotogrammetry, high-resolution scandisk confocal microscopy and scanning electron microscopy, resulting in detailed information about the topography and surface morphology. In addition, dynamic water contact angle measurements were carried out to characterize the wettability of the samples. The effects of polymer type, polymer content, additive content and processing method on the resulting topography and wetting were investigated. The correlation between topography and wetting resulted in a conceptual model of WPC surface morphology and wetting, which may be applied to optimize adhesion properties of this composite material.

Investigation of corrosion behavior of aluminum flakes coated by polymeric nanolayer: Effect of polymer type

Protection of aluminum pigments from corrosion phenomenon has been extended by an encapsulating polystyrene (PS) and poly(acrylic acid) (PAA) nanolayers. Flakes were first coupled with 3-methacryloxypropyltrimethoxysilane (MPS) and in situ polymerizations of styrene and acrylic acid, initiating with Azobisisobutyronitrile (AIBN) were performed. The encapsulated flakes were characterized by Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscope (TEM). Also, polymer chains were analyzed by gel permeation chromatography (GPC). Subsequently the chemical stability of the pigments in alkaline and acidic aqueous media was examined. Results indicated that polystyrene coating remarkably improved flakes’ anticorrosion property while PAA evolved hydrogen.

Whey Protein/Polysaccharide-Stabilized Emulsions: Effect of Polymer Type and pH on Release and Topical Delivery of Salicylic Acid

Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industries. They are thermodynamically unstable and require emulsifiers for stabilization. Studies have indicated that emulsifiers could affect topical delivery of actives, and this study was therefore designed to investigate the effects of different polymers, applied as emulsifiers, as well as the effects of pH on the release and topical delivery of the active. O/w emulsions were prepared by the layer-by-layer technique, with whey protein forming the first layer around the oil droplets, while either chitosan or carrageenan was subsequently adsorbed to the protein at the interface. Additionally, the emulsions were prepared at three different pH values to introduce different charges to the polymers. The active ingredient, salicylic acid, was incorporated into the oil phase of the emulsions. Physical characterization of the resulting formulations, i.e., droplet size, zeta potential, stability, and turbidity in the water phase, was performed. Release studies were conducted, after which skin absorption studies were performed on the five most stable emulsions, by using Franz type diffusion cells and utilizing human, abdominal skin membranes. It was found that an increase in emulsion droplet charge could negatively affect the release of salicylic acid from these formulations. Contrary, positively charged emulsion droplets were found to enhance dermal and transdermal delivery of salicylic acid from emulsions. It was hypothesized that electrostatic complex formation between the emulsifier and salicylic acid could affect its release, whereas electrostatic interaction between the emulsion droplets and skin could influence dermal/transdermal delivery of the active.

Preparation of Cylinder-Shaped Porous Sponges of Poly(L-lactic acid), Poly(DL-lactic-co-glycolic acid), and Poly(ε-caprolactone)

Design of mechanical skeletons of biodegradable synthetic polymers such as poly(L-lactic acid) (PLLA), poly(DL-lactic-co-glycolic acid) (PLGA), and poly(ε-caprolactone) (PCL) is important in the construction of the hybrid scaffolds of biodegradable synthetic polymers and naturally derived polymers such as collagen. In this study, cylinder-shaped PLLA, PLGA, and PCL sponges were prepared by the porogen leaching method using a cylinder model. The effects of polymer type, polymer fraction, cylinder height, pore size, and porosity on the mechanical properties of the cylinder-shape sponges were investigated. SEM observation showed that these cylinder-shaped sponges had evenly distributed bulk pore structures and the wall surfaces were less porous with a smaller pore size than the wall bulk pore structures. The porosity and pore size of the sponges could be controlled by the ratio and size of the porogen materials. The PLGA sponges showed superior mechanical properties than those of the PLLA and PCL sponges. Higher porosity resulted in an inferior mechanical strength. The pore size and sponge height also affected the mechanical properties. The results indicate that cylinder-shaped sponges can be tethered by choosing the appropriate polymers, size and ratio of porogen materials and dimension of sponges based on the purpose of the application.

In situ forming implants for the delivery of metronidazole to periodontal pockets: formulation and drug release studies

This study was performed to obtain prolonged drug release with biodegradable in situ forming implants for the local delivery of metronidazole to periodontal pockets. The effect of polymer type (capped and uncapped PLGA), solvent type (water-miscible and water-immiscible) and the polymer/drug ratio on in vitro drug release studies were investigated. In situ implants with sustained metronidazole release and low initial burst consisted of capped PLGA and N-methyl-2-pyrolidone as solvent. Mucoadhesive polymers were incorporated into the in situ implants in order to modify the properties of the delivery systems towards longer residence times in vivo. Addition of the polymers changed the adhesiveness and increased the viscosity and drug release of the formulations. However, sustained drug release over 10 days was achievable. Biodegradable in situ forming implants are therefore an attractive delivery system to achieve prolonged release of metronidazole at periodontal therapy.

Solid solutions vs. solid dispersions: the impact of formulation parameters

Matrix films were prepared with drugs with different aqueous solubility (metoprolol tartrate, ibuprofen and diclofenac Na) and different polymers (ethylcellulose, Eudragit RS and Eudragit RL). Solid solutions (drug dissolved) and solid dispersions (drug dispersed) were obtained. The drug release was studied as a function of drug type and loading, additive type and amount and polymer type. Drug release from the matrices was not in accordance with drug aqueous solubility, but rather with the physical state of the drug in the matrix. Increasing the drug loading increased the drug release rate in a monotonical fashion for the solid solution. In contrast, increasing the drug loading with the solid dispersion had almost no effect until 30 %. An increase in speed was only registered after the drug release significantly increased. The addition of hydrophilic additives mainly increased the initial phase of the release profile, with no effect on the plateau. On the contrary, polyethylene glycol 1500 was shown to decrease the release of diclofenac Na due to entrapment of the drug in the hydrophilic additive domains. The effect of polymer type on ibuprofen release correlated well with the partition of the drug into the polymer. In the case of metoprolol tartrate, drug release was much faster from Eudragit RS than EC matrices due to the formation of an amorphous mixture with Eudragit RS polymer.

Controlled Release of Ropinirole Hydrochloride from a Multiple Barrier Layer Tablet Dosage Form: Effect of Polymer Type on Pharmacokinetics and IVIVC

The purpose of the present study was to control in vitro burst effect of the highly water-soluble drug, ropinirole hydrochloride to reduce in vivo dose dumping and to establish in vitro-in vivo correlation. The pharmacokinetics of two entirely different tablet formulation technologies is also explored in this study. For pharmacokinetics study, FDA recommends at least 10% difference in drug release for formulations to be studied but here a different approach was adopted. The formulations F8A and F9A having similar dissolution profiles among themselves and with Requip® XL™ (f 2 value 72, 77, 71 respectively) were evaluated. The C max of formulation F8A comprising hypromellose 100,000 cP was 1005.16 pg/ml as compared to 973.70 pg/ml of formulation F9A comprising hypromellose 4000 cP irrespective of T max of 5 and 5.75 h, respectively. The difference in release and extent of absorption in vivo was due to synergistic effect of complex RH release mechanism; however, AUC0-t and AUC0-∞ values were comparable. The level A correlation using the Wagner-Nelson method supported the findings where R (2) was 0.7597 and 0.9675 respectively for formulation F8A and F9A. Thus, in vivo studies are required for proving the therapeutic equivalency of different formulation technologies even though f 2 ≥ 50. The technology was demonstrated effectively at industrial manufacturing scale of 200,000 tablets.

Plasma Directed Organization of Nanodots on Polymers: Effects of Polymer Type and Etching Time on Morphology and Order

AbstractOxygen plasma etching of poly(methyl methacrylate) (PMMA), poly(ethylene terephthalate) (PET), and polystyrene (PS) leads to the formation of organized nanodots on the surfaces of the polymers. In this paper, we describe the metrological characterization of these nanodots and compare their morphology as a function of the polymer type. We study the evolution of the surface morphology with etching time and observe a transition point where dual scale roughness develops, order is lost, and sudden increase in the surface roughness is observed. Possible mechanisms are discussed. magnified image

The effect of polymer type on electric breakdown strength on a nanosecond time scale

Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength (EBD) on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE (polyethylene), PTFE (polytetrafluoroethelene), PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD (PTFE) > EBD (PMMA) > EBD (Nylon) > EBD (PE). This result is consistent with the theoretical prediction.

Effect of Polymer Type on the Dynamics of Phase Inversion and Drug Release in Injectable In Situ Gelling Systems

The objective of this study was to evaluate the effect of the nature of the polymer on the dynamics of phase inversion and drug release in an in situ forming gel drug-delivery system composed of a biodegradable polymer and the solvent N-methyl-2-pyrrolidone (NMP), with metoclopramide monohydrochloride (metosalt) used as a low-molecular-weight model drug. Injection of this solution into an aqueous medium leads to the formation of a solid gel due to the rapid solvent/water exchange, followed by sustained release of the incorporated drug. The release of solvent from the injectable gel into phosphate buffer, which influences the polymer precipitation rate, was investigated as a function of the type of polymer using UV-Vis spectrophotometry. The cross-sectional gel morphology and its water uptake were characterized to relate the initial burst release (and thus the dynamics of phase inversion) to the polymer lactide/glycolide ratio and to the end-group characteristics. The results show that the phase inversion of hydrophobic polymers (e.g., PdlLA) occurs faster than the phase inversion of relatively more hydrophilic polymers (e.g., PLGA75/25, RG502 and RG502H). Three of the four polymers exhibit a four-phase profile, with the characteristics of each phase dependent on the hydrophobicity and degradation kinetics of the individual polymer.

The Spectrophotometric Investigation of Nonionic Polymer Adsorption (Polyethylene Glycol (PEG), Polyethylene Oxide (PEO) and Polyvinyl Alcohol (PVA)) Influence on the Alumina Suspension Stability – Effects of Polymer Type, its Molecular Weight and Solution pH

The effect of nonionic polymer adsorption on the stability of alumina (Al2O3) in the pH range 3–9 was examined. The influences of polymer type and its molecular weight, as well as solution pH, were studied. The following macromolecular substances were used: polyethylene glycol (PEG), polyethylene oxide (PEO) and polyvinyl alcohol (PVA). The spectrophotometry method was applied to obtain the stability curves (dependence of suspension absorbance vs. time). The obtained results indicate that the addition of the polymer influences alumina suspension stability. The addition of the polymer at pH 3 improves the stability conditions of investigated systems. At pH = 6 the decrease of Al2O3 suspension stability (except PEG 2 000) was obtained. On the other hand, at pH 9 the presence of polymer improves the stability properties of the alumina. The higher the molecular weight of the polymer, the more pronounced effects were observed. Moreover, adsorption of polyvinyl alcohol whose macromolecules contain ionizable acetate groups causes greater changes in alumina suspension stability in comparison to the systems containing polyethylene glycol and polyethylene oxide.

Self-healing of polymer modified concrete

Self healing phenomenon of concrete has been observed in traditional, fibrous, self compacting concrete. This phenomenon occurred mainly due to the presence of unhydrated cement particles in the presence of water. Mechanism of polymer in concrete depends on creating a layer and net of polymer around cement particles which enhances the properties of polymer modified concrete. This mechanism may affect the self healing of this type of concrete. This work aims to study the presence of the self healing phenomenon in polymer modified concrete and the related parameters. An experimental investigation on self healing of polymer modified concrete was undertaken. In this research work, effect of polymer type, polymer dose, cement content, cement type, w/cm ratio and age of damage were studied. The healing process extended up to 60 days. Ultrasonic pulse velocity measurements were used to evaluate the healing process. Results indicated that, the self healing phenomenon existed in polymer modified concrete as in traditional concrete. The increase of polymer dose increases the healing degree at the same healing time. This increase depends on polymer type. Also, the decrease of w/cm ratio reduces the self healing degree while the use of Type V Portland cement improves the self healing process compared with Type I Portland cement. Cement content has an insignificant effect on healing process for both concrete with and without polymer. In addition, the increase of damage age decreases the efficiency of self healing process.

Experimental Study of Polymer Flooding in Low-Viscosity Oil Using One-Quarter Five-Spot Glass Micromodel

A polymer flooding technique is developed to reduce the amount of residual oil saturation that cannot be recovered through waterflooding or gas injection processes. Using polymer flooding in the case of high-viscosity oil has been successful due to reducing mobility ratio (M), whereas there is conflict in efficiency of polymer flooding in the case of low-viscosity oil. In this study, to investigate the behavior of polymer flooding in low-viscosity oil, the transparent materials (glass) were used to construct a micromodel and to study various aspects of micro-displacement. By using a micromodel, the displacement of the fluid and menisci was observed and investigated with the aid of images captured by a camera. In this work, two kinds of quarter five-spot glass micromodel patterns were designed and developed and considered as pores medium. These patterns were saturated with light and low-viscosity oil samples from an Iranian fractured reservoir and then flooded by a polymer slug in low-pressure and low-temperature conditions. Three polymer types, hydrolyzed polyacrylamide (HPAM 25%), very low hydrolyzed polyacrylamide (<5%; PA) and xanthan, were utilized to inspect the effects of polymer type, concentration, injection rate, pore structure, and presence of connate water on recovery of low-viscosity oil. The results of experiments illustrated that recovery from HPAM is higher than both xanthan and very low hydrolyzed polyacrylamide. Rate sensitivity tests showed that increasing rate injection induced a decrease in recovery. Flooding in two different micromodel patterns demonstrated that higher permeability leads to lower recovery. In addition, experiments indicated that the presence of connate water caused a reduction in recovery. Finally, compared with waterflooding, polymer flooding resulted in a considerable growth in ultimate oil recovery.

Active targeting of dendritic cells with mannan-decorated PLGA nanoparticles

The purpose of this study was to identify an optimum targeted particulate formulation based on mannan (MN)-decorated poly(D, L-lactide-co-glycolide) (PLGA) nanoparticles (NPs), for efficient delivery of incorporated cargo to dendritic cells (DCs). In brief, NPs were formulated from two different types of PLGA; ester-terminated (capped) or COOH-terminated (uncapped) polymer. Incorporation of MN in NPs was achieved either through addition of MN during the process of NP formation or by attachment of MN onto the surface of the freeze dried NPs by physical adsorption or chemical conjugation (to COOH terminated polymer). The formulated NPs were characterized in terms of particle size, Zeta potential and level of MN incorporation. The effect of polymer type and the incorporation method on the extent of fluorescently labelled NP uptake by murine bone marrow-derived DCs have been investigated using flowcytometry. The results of this study showed MN incorporation to enhance the uptake of PLGA NPs by DCs. Among different MN incorporation strategies, covalent attachment of MN to COOH-terminated PLGA-NPs provided the highest level of MN surface decoration on NPs. Maximum NP uptake by DCs was achieved by COOH terminated PLGA NPs containing covalent or adsorbed MN. Therefore, a better chance of success for these formulations for active targeted drug and/or vaccine delivery to DCs is anticipated.

Double-layer weekly sustained release transdermal patch containing gestodene and ethinylestradiol

The combination therapy of gestodene (GEST) and ethinylestradiol (EE) has shown advanced contraception effect and lower side effect. The present study was designed to develop a weekly sustained release matrix type transdermal patch containing GEST and EE using blends of different polymeric combinations. The multiple-layer technique was adopted in order to maintain a steady permeation flux for 7 days. The effects of polymer types, polymer ratios, permeation enhancers, drug loadings and drug ratios in different layers on the skin permeations of the drugs were evaluated using excised mice skin. Polariscope examination was carried out to observe the drug distribution behavior. The formulation with the mixture of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) (7:1) was found to provide the regular release and propylene glycol (PG) could enhance the permeation fluxes of drugs. Double-layer transdermal drug delivery system (TDDS) could sustain the steady permeation flux of drugs for 7 days when the ratio of drug in drug release layer and drug reservoir layer was 1:4 with the identical total drug amount. The in vitro transdermal permeation fluxes were 0.377 μg/cm 2/h and 0.092 μg/cm 2/h, for GEST and EE respectively. The uniformity of dosage units test showed that the distribution of drugs in the matrix was homogeneous, which was further demonstrated by the polariscope result. The developed transdermal delivery system containing GEST and EE could be a promising non-oral contraceptive method.

The Evaluation of Eudragit Microcapsules Manufactured by Solvent Evaporation Using USP Apparatus 1

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.

Effect of polymer type on the dissolution profile of amorphous solid dispersions containing felodipine

Amorphous solid dispersions are used as a strategy to improve the bioavailability of poorly water-soluble compounds. When formulating with a polymer, it is important not only for the polymer to stabilize against crystallization in the solid state, but also to improve the dissolution profile through inhibiting crystallization from the supersaturated solution generated by dissolution of the amorphous material. In this study, the dissolution profiles of solid dispersions of felodipine formulated with poly(vinylpyrrolidone) (PVP), hydroxypropyl methylcellulose (HPMC) or hydroxypropyl methylcellulose acetate succinate (HPMCAS) were compared. In addition, concentration versus time profiles were evaluated for the supersaturated solutions of felodipine in the presence and absence of the polymers. HPMCAS was found to maintain the highest level of supersaturation for the greatest length of time for both the dissolution and solution crystallization experiments, whereas PVP was found to be the least effective crystallization inhibitor. All polymers appeared to reduce the crystal growth rates of felodipine at an equivalent supersaturation and this mechanism most likely contributes to the enhanced solution concentration values observed during dissolution of the amorphous solid dispersions.