Time-dependent Polymer Research Articles

Combination of time-dependent polymer and inulin as a coating for sustained delivery of budesonide pellets aimed for use in IBD treatment

Combination of time-dependent polymer and inulin as a coating for sustained delivery of budesonide pellets aimed for use in IBD treatment

Formulation and Development of Flurbiprofen Colon-Specific Eudragit Coated Matrix Tablets: Use of a Novel Crude Banana Peel Powder as a Time-Dependent Polymer.

The rationale for the current investigation is to study the crude banana peel (CBP) powder efficiency as a novel natural time-dependent polymer along with a pH-sensitive polymer to develop flurbiprofen colon-specific tablets. The direct compression method is utilized to prepare the flurbiprofen-CBP matrix tablets using 9mm punches on the rotary tableting machine and subsequently coated with Eudragit® S 100 by a dip coating method. The tablets were evaluated for various tableting properties and in vitro drug release studies. From the results of dissolution studies, the F6 formulation showed negligible drug release (5.76% in 5h) in the upper gastrointestinal tract and progressive release in the colon (99.08% in 24h). Mean dissolution time, T10%, and T80% were found to be 13.33h, 5.8h, and 20.7h, respectively, which explains the efficiency of the present combination of polymers for colon-specific drug release. From the dissolution studies results of stability studies, the similarity index was calculated and found to be 74.75. In conclusion, utilizing CBP as a natural, time-dependent polymer in conjunction with Eudragit® S 100 to develop the flurbiprofen tablets seems like a promising approach for delivering drugs specifically to the colon.

Significance of Chemical Processes and Non-uniform Heat Sink/source Aspects for Time-dependent Polymer Liquid Carrying Nanoparticles

Owing to extensive application developments of nanofluid, the engineers and scientists have concentrated their attention in regions of thermal and engineering processes. Additionally, nanofluids have wide-ranging returns as compared to traditional fluids. Keeping aforementioned logicality of nanofluid in observation, we deliberated a time-varying mathematical model to formulate the non-uniform heat sink-source assume Sutterby liquid over Brownian movements and thermophoretic. Thermal- solutal stratification phenomenon in addition with heat sink-source and activation energy aspects are scrutinized. Characteristics of random motion and thermophoresis diffusion properties for Sutterby fluid are examined. Similarity variable techniques are used to reduce partial differential equations into ordinary differential equations and solved numerically by using bvp4c method. The physical aspects of fluid flow, temperature, concentration for variation of involved parameters have been explained through graphs. Velocity of Sutterby nanofluid has contrary performances against unsteady and mixed convection parameters. Augmented values of Brownian moment, thermophoresis and heat source parameters exaggerate the temperature of nanofluid. Concentration of Sutterby nanofluid deteriorates for greater Schmidt number. Moreover, transportation rate of heat dwindles against Pr while it rises against NSUBt/SUB.

Impact of thermal-solutal stratifications and activation energy aspects on time-dependent polymer nanoliquid

Nanofluids are used in our daily life and have engineering applications due to their improving energy efficiency and heat transfer in different thermal systems. Nanotechnology and thermal performance have developed a great prospect for global scientists and researchers. In our research work, we have considered time-dependent Sutterby nanofluid by capturing the aspects of thermal radiation and stratification phenomenon. Additionally, features of activation energy and heat source-sink are considered. Transformation variables are used to reduce PDEs into nonlinear ordinary differential equations. To obtain the numerical results, we have used the bvp4c scheme. Through graphs and tables, we have demonstrated a comprehensive analysis for velocity, temperature, concentration profiles, skin-friction parameter, Nusselt number, and Sherwood number. It is analyzed that the temperature profile increases as the thermal biot number raises, also, the concentration profile declines when the Schmidt number raises.

Inflated Cone Experiment for High-Throughput Characterization of Time-Dependent Polymer Membranes

Abstract Long-term behavior of polymer membranes in the nonlinear regime is probed by strain histories under various stress levels. Current characterization methods for polymer membranes impose a uniform stress field and hence require a series of long-duration tests to be conducted, which poses a significant experimental challenge. Here, we present the inflated cone method to generate a continuous spectrum of strain histories under various stresses in a single experiment. By imposing a known stress gradient and utilizing a full-field strain measurement technique, the inflated cone method provides a high-throughput approach for extracting time-dependent data of polymer membranes. The method is suitable for studying nonlinear time-dependent deformations under a biaxial stress state. The stress range and ratio can be easily modulated by cone geometry design. We demonstrate the utility of the method through creep-recovery tests carried out on a polyethylene thin film. The proposed experimental method is highly beneficial for the development of nonlinear viscoelastic and viscoplastic models.

Wall-anchored semiflexible polymer under large amplitude oscillatory shear flow.

The properties of semiflexible polymers tethered by one end to an impenetrable wall and exposed to oscillatory shear flow are investigated by mesoscale simulations. A polymer, confined in two dimensions, is described by a linear bead-spring chain, and fluid interactions are incorporated by the Brownian multiparticle collision dynamics approach. At small strain, the polymers follow the applied flow field. However, at high strain, we find a strongly nonlinear response with major conformational changes. Polymers are stretched along the flow direction and exhibit U-shaped conformations while following the flow. As a consequence of confinement in the half-space, frequency doubling in the time-dependent polymer properties appears along the direction normal to the wall.

Propagation of quantum gravity-modified gravitational waves on a classical FLRW spacetime

The linearized Einstein field equations provide a low-energy wave equation for the propagation of gravitational fields which may originate from a high energy source. Motivated by loop quantum gravity, we propose the polymer quantization scheme to derive the effective propagation of such waves on a classical Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. To overcome the challenge of polymer quantizing a time-dependent Hamiltonian, we rewrite such a Hamiltonian in a time-independent manner in the extended phase space, polymerize it, and then transform it back to the usual phase space. In this way we obtain a time-dependent polymer Hamiltonian for the gravitational waves. We then derive the effective equations of motion and show that (i) the form of the waves is modified, (ii) the speed of the waves depends on their frequencies, and (iii) quantum effects become more apparent as waves traverse longer distances.

Optimizing pH-sensitive and time-dependent polymer formula of colonic pH-responsive pellets to achieve precise drug release

Time-sensitive and pH-dependent polymers are generally employed to prepare colon-site delivery system, and their coating thickness and order are very important in controlling the drug release. The traditional colon-site delivery systems consist of time-dependent polymers as inner layer and pH-sensitive polymers as outer layer. However, they suffer from low drug-loading rate and immature drug release. In this study, total alkaloids of sophora alopecuroides(TASA)-loaded pellets were prepared by extrusion-spheronization method and coated with Eudragit RS30D and Eudragit S100. Pellets using Eudragit RS30D as inner layer and Eudragit S100 as outer layer were named as ERS-ES100 TCO, while pellets with Eudragit S100 as inner layer and Eudragit RS30D as outer layer were ES100-ERS NCO. Both types of formulations with varying coating ratios and orders of Eudragit S100 and Eudragit RS30D were designed and prepared. The following in vitro drug release and SEM studies indicated that ERS-ES100 TCO(F2) with 12.8% Eudragit RS30D as inner layer and 21% Eudragit S100 as outer layer released up to 42% drug in 5 h. Interestingly, ES100-ERS NCO (F4) coated with 12.8% Eudragit S100 and 14.8% Eudragit RS30D showed optimal drug release in colon. In conclusion, ES100-ERS NCO colonic delivery system achieved reduced coating thickness and improved colonic targeting compared with traditional delivery system (ERS-ES100 TCO). In addition, the similarity factors (f2) value of sophoridine and matrine for investigated formulation were within 50–100 and > 80, demonstrating that sophoridine and matrine in all formulations achieved a synchronous release.

In vivo evaluation of pH and time-dependent polymers as coating agent for colonic delivery using central composite design

The objective of this study was to evaluate the combination of pH-dependent and time-dependent polymers on drug release in order to optimize coating for colonic delivery. Response surface methodology (RSM) based on central composite design (CCD) was employed for formulation optimization. Theophylline was used as model drug and Eudragit® FS 30D and hydroxypropyl methylcellulose (HPMC) were used as pH-dependent and time-dependent polymer, respectively. Dissolution test was carried out using the release conditions as follow: pH 1.2 for 2 h, pH 6.8 for 2 h, pH 7.4 for 3 h and pH 6.8 for 3 h. Scanning electron microscopy (SEM) was applied to observe the morphology of coated capsules. Drug release was evaluated spectrophotometrically. In vivo X-ray imaging study was used to trace the movement and behavior of the capsules in gastrointestinal (GI) tract. The optimized formulation containing 0.5% HPMC and 80% Eudragit FS 30D was prepared according to the software determined levels. There was no drug release for 2 h at pH 1.2 and for 2 h at pH 6.8. Optimum values of drug release were 32.57% and 71.37% at pH 7.4 (7 h) and pH 6.8 (10 h), respectively, which were in agreement with the predicted value by RSM. Surface coated capsules were rougher than gelatin capsules as examined by SEM. X-ray analysis confirmed that coated capsules dissolved at the targeted colon region. The results of this study indicate that the designed system can be potentially used as a carrier for colon delivery of drugs.

Characterization and Screening of a Novel Multiparticulate Pulsatile Delivery of Aceclofenac

In the present investigation, sodium alginate based multiparticulate system overcoated with time and pH dependent polymer was studied in the form of oral pulsatile system to achieve pulsatile with sustained release of aceclofenac for chronotherapy of rheumatoid arthritis seven batches of micro beads with varying concentration of sodium alginate (2-5 %) were prepared by ionotropic-gelation method using CaCl2 as cross-linking agent. The prepared Ca-alginate beads were coated with 5% Eudragit L100 and filled into pulsatile capsule with varying proportion of plugging materials. Drug loaded microbeads were investigated for physicochemical properties and drug release characteristics. The mean particle sizes of drug-loaded microbeads were found to be in the range 596±1.1 to 860 ± 1.2 micron and %DEE in the range of 65-85%. FT-IR and DSC studies revealed the absence of drug polymer interactions. The release of aceclofenac from formulations F1 to F7 in buffer media (pH 6.8) at the end of 5h was 65.6, 60.7, 55.7, 41.2, 39.2, 27 and 25% respectively. Pulsatile system filled with eudragit coated Ca-alginate microbeads (F2) showed better drug content, particle size, surface topography, in-vitro drug release in a controlled manner. Different plugging materials like Sterculia gum, HPMC K4M and Carbopol were used in the design of pulsatile capsule. The pulsatile system remained intact in buffer pH 1.2 for 2 hours due to enteric coat of the system with HPMCP. The enteric coat dissolved when the pH of medium was changed to 7.4. The pulsatile system developed with Sterculia gum as plugging material showed satisfactory lag period when compared to HPMC and Carbopol.

Preparation and evaluation of electrospun nanofibers containing pectin and time-dependent polymers aimed for colonic drug delivery of celecoxib

Objective(s):The aim of this study was to prepare electrospun nanofibers of celecoxib using combination of time-dependent polymers with pectin to achieve a colon-specific drug delivery system for celecoxib. Materials and Methods:Formulations were produced based on two multilevel 22 full factorial designs. The independent variables were the ratio of drug:time-dependent polymer (X1) and the amount of pec‌tin in formulations (X2). Electrospinning process was used for preparation of nanofibers. The spinning solutions were loaded in 5 mL syringes. The feeding rate was fixed by a syringe pump at 2.0 mL/h and a high voltage supply at range 10-18 kV was applied for electrospinning. Electrospun nanofibers were collected and evaluated by scanning electron microscopy and drug release in the acid and buffer with pH 6.8 with and without pectinase. Results:Electrospun nanofibers of celecoxib with appropriate morphological properties were produced via electrospinning process. Drug release from electrospun nanofibers was very low in the acidic media; while, drug release in the simulated colonic media was the highest from formulations containing pectin. Conclusion: Formulation F2 (containing drug:ERS with the ratio of 1:2 and 10% pectin) exhibited acceptable morphological characteristics and protection of drug in the upper GI tract and could be a good candidate as a colonic drug delivery system for celecoxib.

Effect of time-dependent polymer on the dissolution rate of flurbiprofen: Formulation and evaluation of colon-specific matrix tablets

Effect of time-dependent polymer on the dissolution rate of flurbiprofen: Formulation and evaluation of colon-specific matrix tablets

Improved Poly(3,4-Ethylenedioxythiophene) (PEDOT) for Neural Stimulation.

This study compares the stability of three variations of the conductive polymer poly(3,4-ethylenedioxythiophene) or PEDOT for neural micro-stimulation under both in vitro and in vivo conditions. We examined PEDOT films deposited with counter-ions tetrafluoroborate (TFB) and poly(styrenesulfonate) (PSS), and PSS combined with carbon nanotubes (CNTs). For the in vitro stability evaluation, implantable micro-wires were coated with the polymers, placed in a vial containing phosphate buffered saline (PBS) under accelerated aging conditions (60°C), and current pulses were applied. The resulting voltage profile was monitored over time. Following the same polymer deposition protocol, chronic neural micro-probes were modified and implanted in the motor cortex of two rats for the in vivo stability comparison. Similar stimulating current pulses were applied and the output voltage was examined. The electrochemical impedance spectroscopic (EIS) data were also recorded and fit to an equivalent circuit model that incorporates and quantifies the time-dependent polymer degradation and impedance associated with tissue surrounding each micro-electrode site. Both in vitro and in vivo voltage output profiles show relatively stable behavior for the TFB modified micro-electrodes compared to the PSS and CNT: PSS modified ones. EIS modeling demonstrates that the time-dependent increase in the polymeric resistance is roughly similar to the rise in the respective voltage output in vivo and indicates that the polymeric stability and conductivity, rather than the impedance due to the tissue response, is the primary factor determining the output voltage profile. It was also noted that the number of electrodes showing unit activity post-surgery did not decay for TFB as was the case for PSS and CNT: PSS. TFB may be an enabling material for achieving long lasting micro-stimulation and recording.

Formulation of indomethacin colon targeted delivery systems using polysaccharides as carriers by applying liquisolid technique.

The present study aimed at the formulation of matrix tablets for colon-specific drug delivery (CSDD) system of indomethacin (IDM) by applying liquisolid (LS) technique. A CSDD system based on time-dependent polymethacrylates and enzyme degradable polysaccharides was established. Eudragit RL 100 (E-RL 100) was employed as time-dependent polymer, whereas bacterial degradable polysaccharides were presented as LS systems loaded with the drug. Indomethacin-loaded LS systems were prepared using different polysaccharides, namely, guar gum (GG), pectin (PEC), and chitosan (CH), as carriers separately or in mixtures of different ratios of 1 : 3, 1 : 1, and 3 : 1. Liquisolid systems that displayed promising results concerning drug release rate in both pH 1.2 and pH 6.8 were compressed into tablets after the addition of the calculated amount of E-RL 100 and lubrication with magnesium stearate and talc in the ratio of 1 : 9. It was found that E-RL 100 improved the flowability and compressibility of all LS formulations. The release data revealed that all formulations succeeded to sustain drug release over a period of 24 hours. Stability study indicated that PEC-based LS system as well as its matrix tablets was stable over the period of storage (one year) and could provide a minimum shelf life of two years.

Investigation of the influence of different commercial softeners on the stability of poly(lactic acid) fabrics during storage

We have studied the potential degradation of poly(lactic acid)-based fabrics treated with commercial softeners and stored under two sets of conditions for one year. Initial wet-processing caused a fall in molecular weight of about 28%, irrespective of after-treatment. Storage at 40 °C and 80% RH produced further degradation which, with few exceptions, was aggravated by the presence of softeners. Ultimately, all samples degraded beyond the point of commercial usefulness. No clear distinction could be made between the effects of softeners having differing compositions. In contrast, fabrics stored under milder conditions of 23 °C and 50% RH showed no significant time-dependent polymer degradation, irrespective of the treatment applied. There were slight changes in tensile properties and some evidence of physical structural effects having occurred, which we attribute to physical aging. However, we do not believe these to be so serious as to call into question the long-term viability of PLA-based textile products.

Analysis of time dependent polymer deformation based on a viscoelastic model in thermal imprint process

A finite element simulation tool for thermal imprint process has been developed. In the system, polymer is assumed to be a viscoelastic body represented by the generalized Maxwell model. We experim...

Analysis of time dependent polymer deformation based on a viscoelastic model in thermal imprint process

A finite element simulation tool for thermal imprint process has been developed. In the system, polymer is assumed to be a viscoelastic body represented by the generalized Maxwell model. We experimentally measured viscoelastic properties of a polymer material and derived parameters used in the simulation tool. Using the same polymer material, we performed imprint experiments to examine time dependent deformation. Comparing the polymer deformations in simulated results with those in experiments, we confirmed that the developed simulation tool and the measured material parameters were useful for analysis of thermal imprint process.

Reaction of pectin and glycidyl methacrylate and ulterior formation of free films by reticulation

In this work, low-methoxyl pectin was chemically modified by reaction with glycidyl methacrylate (GMA) to give a material with low hydrosolubility. After physio-chemical characterization by FT-IR, DSC, and TGA analyses, the methacrylated/modified pectin (Pect-GMA) was crosslinked after the addition of sodium persulfate (SP), that actuates as initiator, at 50 °C for 24 and 48 h either in the presence or not of aqueous polymethacrylate dispersion (Eudragit ® RS 30 D) to obtain free films by Teflon ® plate “casting” process. Different Pect-GMA/Eudragit ® RS 30 D ratios and SP concentrations were used. The free films were characterized by the determination of water vapor transmission (WVT), the swelling index ( I eq%) in simulated gastric (SGF) and intestinal (SIF) fluids, and by scanning electron microscopy (SEM). The presence of ionized groups in Pect-GMA turned the films pH-dependent because I eq% of swollen crosslinked Pect-GMA films was larger at pH 6.8 than at pH 1.2. This was confirmed by the large pore size observed in the micrographs of SIF-swollen lyophilized films. In this way, films containing Pect-GMA and Eudragit ® RS 30 D, a time-dependent polymer, may present a synergistic action that favors specific biodegradation of the film in distal end of the gastrointestinal tract (GIT) by enzymes produced by the colonic microflora, enabling the modification of the release kinetics of drugs.

Thermal quenching sample chamber for grazing incidence small angle x-ray scattering studies of polymer films

The second generation of a sample chamber designed for in situ measurement of temperature- and time-dependent polymer film nanostructure using the method of grazing incidence small angle x-ray scattering is presented. An increased operating temperature limit (from 260 to 400 degrees C) with precise control (+/-0.1 degrees C) at fixed temperatures as well as a fourfold increase in maximum instantaneous cooling rate (up to 73 degrees C/s) relative to the first generation chamber [M. N. Groves et al, J. Appl. Crystallogr. 39, 120 (2006)] are reported. Thermal quenches from 220 to 90 degrees C are shown to be reproducible to within +/-1 degrees C of the final temperature. Experimental tests on spin-coated films of symmetric diblock styrene-butadiene copolymer demonstrate the ability to resolve the kinetics of orientation of lamellar domains parallel to the silicon substrate, distinct from the initial formation of randomly oriented lamellar domains immediately following the thermal quench.

A simple method to predict high strain rates mechanical behavior of low interconnected cell foams

A method to model high strain rate compressive properties of PU foams was investigated. The nonlinear mechanical response of the foam was split into three independent contributions: foam morphology, time-dependent polymer response, gas entrapped in the cells. The foam morphology contribution was estimated by a simple uniaxial compression test at very low strain rate. The time (temperature)-dependent behavior of the polymeric foam was evaluated by stress relaxation tests. Due to the low degree of cell interconnections of the studied foam, at low strain rates the gas contribution was predicted by using a gas flow model derived from Darcy's law. Starting from 2 s −1 compressive strain rate, the foam exhibited a transition and the gas contribution was evaluated by a scaled closed cell model. The proposed method is able to predict the mechanical response of foams at high strain rates using data obtained by few low strain rates mechanical tests.