Effect Of Polymer Molecular Weight Research Articles

Effect of the Lactide/Glycolide Ratio and Molecular Weight of PLGA on the Bovine BMPs Microspheres Systems

The present investigation was aimed at optimization of BMPs loaded PLGA microspheres formulations resulting in improved encapsulation efficiency and sustained release of BMPs by varying the molecular weight and copolymer composition of PLGA. Double-emulsion solvent evaporation method was used to prepare the microspheres. The effect of polymer molecular weight and copolymer composition on particle properties and release behavior in vitro was reported. The particle size and encapsulation efficiency increased with increase in molecular weight and lactide content of PLGA. While BMPs release in vitro decreased with increase in molecular weight and lactide content of PLGA. SEM pictures revealed that almost all microspheres were spherical but internal morphology was different. The morphology of PLGA microspheres with exorbitant molecular weight(100kD) was anomalistic whereas the morphology of PLGA microspheres with higher glycolide content(50) have porous structures.

Effects of polymer molecular weight on relative oral bioavailability of curcumin

BackgroundPolylactic-co-glycolic acid (PLGA) nanoparticles have been used to increase the relative oral bioavailability of hydrophobic compounds and polyphenols in recent years, but the effects of the molecular weight of PLGA on bioavailability are still unknown. This study investigated the influence of polymer molecular weight on the relative oral bioavailability of curcumin, and explored the possible mechanism accounting for the outcome.MethodsCurcumin encapsulated in low (5000–15,000) and high (40,000–75,000) molecular weight PLGA (LMw-NPC and HMw-NPC, respectively) were prepared using an emulsification-solvent evaporation method. Curcumin alone and in the nanoformulations was administered orally to freely mobile rats, and blood samples were collected to evaluate the bioavailability of curcumin, LMw-NPC, and HMw-NPC. An ex vivo experimental gut absorption model was used to investigate the effects of different molecular weights of PLGA formulation on absorption of curcumin. High-performance liquid chromatography with diode array detection was used for quantification of curcumin in biosamples.ResultsThere were no significant differences in particle properties between LMw-NPC and HMw-NPC, but the relative bioavailability of HMw-NPC was 1.67-fold and 40-fold higher than that of LMw-NPC and conventional curcumin, respectively. In addition, the mean peak concentration (Cmax) of conventional curcumin, LMw-NPC, and HMw-NPC was 0.028, 0.042, and 0.057 μg/mL, respectively. The gut absorption study further revealed that the HMw-PLGA formulation markedly increased the absorption rate of curcumin in the duodenum and resulted in excellent bioavailability compared with conventional curcumin and LMw-NPC.ConclusionOur findings demonstrate that different molecular weights of PLGA have varying bioavailability, contributing to changes in the absorption rate at the duodenum. The results of this study provide the rationale for design of a nanomedicine delivery system to enhance the bioavailability of water-insoluble pharmaceutical compounds and functional foods.

Poly(ethylene glycol) and poly(N-vinlypyrrolidone) for improved porcine islet cryopreservation

Water-soluble polymers poly(ethylene glycol) (PEG) and poly(N-vinylpyrrolidone) (PVP) were used to study cryopreservation of porcine islets. DMSO was used as control. The effects of polymer purity, molecular weight (MW) and concentration on islet viability were investigated. The results show that both PVP and PEG are good cyroprotectant candidates for islet cryopreservation. The effects of polymer purity and concentration were significant. Increasing concentration significantly increased the islet viability. However, after the concentration reached a certain level, there was no significant difference in viability probably due to increased viscosity of the polymer solution. The effect of polymer MW was not significant. It is concluded that polymers can be a suitable cryoprotectant for porcine islet cryopreservation. The islet viability is polymer concentration-dependent. It seems that PVP is a better cryoprotectant candidate as compared to PEG because the former showed a fast dissolution rate in culture medium and lower viscosity. The polymer concentration at 30% appears to be the optimal for cryopreservation from the viewpoint of islet viability and medium viscosity.

Effect of polymer molecular weight on the structural properties of non aqueous ethyl cellulose gels intended for topical drug delivery

Abstract The structural properties of five ethyl cellulose polymers (EC) in mixture with the non aqueous solvent of propylene glycol dicaprylate (PGD) have been investigated with a view to facilitating topical drug delivery. Total concentration of the polymer varied from 12 to 20% (w/w) and its weight average molecular weight was in the range of 64–223 kDa. Experimental techniques utilised were small-deformation dynamic oscillation in shear, attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) and wide-angle X-ray diffraction. The nature of the time and temperature dependence on viscoelastic functions of all samples could be treated with the Chambon and Winter criterion allowing determination of the critical gelation temperature in relation to polymer concentration and molecular weight. A further refinement of this school of thought allowed correlation between the viscoelastic relaxation exponent and fractal dimensions in thermally treated EC/PGD matrices. Tangible evidence on the packing arrangements of the ethyl cellulose network and the molecular nature of its interaction with the non aqueous solvent as a function of polymer concentration and molecular weight was provided by X-ray diffraction and infrared studies.

The Effect of Polymer Molecular Weight and UV Radiation on Physical Properties and Bioactivities of PCL Films

Biodegradable polymers, such as polycaprolactone (PCL), have been well studied in the application of tissue engineering and drug delivery systems due to their favourable biocompatibility profiles. However, little research has discussed the influence of the molecular weight of these polymers on cell behaviours. Here, PCL films were synthesized using polymers with various molecular weight and the physical characteristics of these films and their effect on cell growth were evaluated. Results showed that the tensile strength and elongation rate of PCL films increased from 1.82 MPa and 95.3% to 2.01 MPa and 741.6% when the molecular weight (Mn) of polymers increased from 40,000 to 80,000. A significant difference in polymer crystallinity was also observed between these formulations. Moreover, we found that prolonged exposure to UV radiation of these films could lead to the breakdown of polymer chains and consequently increased the crystallinity of PCL films with a corresponding reduction in the tensile strength. Using Hs68 human foreskin fibroblasts, PCL films prepared using high molecular weight polymers (CAPA 6800) displayed a higher cell proliferation rate compared to ones prepared using low molecular weight polymers (CAPA 6400 and 6500). In contrast, a higher cell proliferation rate was observed for PCL films made of low molecular weight polymers, especially CAPA 6500, when H9c2 rat heart myoblasts were used. In conclusion, polymer molecular weight can alter the

Effect of polymer molecular weight on the fiber morphology of electrospun mats

In this work, different fractions of solvent-induced polymer degraded solution were mixed with freshly prepared solution of same polymer, and its effect on fiber morphology of electrospun mats was investigated. Nylon-6 solution in formic acid was allowed to degrade for 3 weeks and different fractions of it were mixed with freshly prepared nylon-6 solution to get the electrospun mats. FE–SEM images of the mats indicated that the a large amount of sub-nanofibers (<50 nm in diameter) in the form of spider-net like structures were achieved by tailoring the amount of solvent degraded polymer solution in the freshly prepared nylon-6 solution. Large quantity of these ultrafine sub-nanofibers present in electrospun nylon-6 mats could increase its hydrophilicity and mechanical strength. The decreased average pore diameter and increased BET surface area of the mat, caused by spider-net like structure, can make it as a potential candidate for air/water filtration.

Molecular-weight-dependent nanoscale morphology in silole-containing cyclopentadithiophene polymer and fullerene derivative blends

We have investigated the effect of polymer molecular weight (MW) on the morphology and efficiency of bulk heterojunction (BHJ) solar cells comprised of poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl- alt-(5,5′-thienyl-4,4′-dihexyl-2,2′-bithiazole)-2,6-diyl] (Si-PCPDTTBT) and [6,6]-phenyl C 61 butyric acid methyl ester (PCBM). Striking morphological changes are observed in BHJ films upon the change of the polymer MW. Atomic force microscopy and transmission electron microscopy studies suggest that high MW polymer generated high degree of phase separation, leading to formation of an interpenetrating network for carrier transport. The X-ray diffraction investigation indicated that increased π–π stacking in Si-PCPDTTBT with increasing polymer MWs results in an increase in hole mobility of Si-PCPDTTBT and electron mobility of PCBM as well as the red shift absorption spectrum in BHJ films. The solar cells based on PCBM with high-MW Si-PCPDTTBT deliver power conversion efficiencies of 3.33%.

Structure and properties development in poly(phenylene sulfide) fibers, part I: Effect of material and melt spinning process variables

AbstractThe detailed research study of manufacturing PPS fibers using melt spinning and further enhancement of tensile properties by drawing and annealing experiments, a study lacking as of today in open scientific literature, was the focus of this research. This article discusses the effect of polymer molecular weight (MW) and melt spinning process variables on the structure and properties development in melt spun fibers manufactured from proprietary Fortron® linear PPS resins. Structure‐properties relationship was studied using several characterization tools like tensile testing, differential scanning calorimetry, polarized light optical microscopy, and wide‐angle x‐ray scattering. Changes in dynamic mechanical behavior of as‐spun fibers manufactured from resins of varying MW and different melt spinning take‐up speeds were also studied. The study showed that by a combination of higher MW of the polymer and spinning at higher take‐up speeds, tensile properties of as‐spun PPS fibers can be improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The effect of polymer molecular weight on the incidence of film cracking and splitting on film coated tablets.

Journal Article The effect of polymer molecular weight on the incidence of film cracking and splitting on film coated tablets Get access R C Rowe, R C Rowe ICI Pharmaceuticals Division, Alderley Park, Cheshire SK10 2TG, UK Correspondence: ICI Pharmaceuticals Division, Alderley Park, Cheshire SK10 2TG, U.K. Search for other works by this author on: Oxford Academic Google Scholar S F Forse S F Forse ICI Pharmaceuticals Division, Alderley Park, Cheshire SK10 2TG, UK Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 32, Issue 1, September 1980, Pages 583–584, https://doi.org/10.1111/j.2042-7158.1980.tb13003.x Published: 12 April 2011 Article history Received: 10 April 1980 Published: 12 April 2011

Phase Separation of DMDBS from PP: Effect of Polymer Molecular Weight and Tacticity

We report an unexpected dependence of DMDBS phase separation temperature on the molecular weight of the matrix isotactic polypropylene (iPP). DMDBS crystallizes out at lower temperatures for iPP with decreasing molecular weight (and correspondingly lower tacticity). All the iPPs in our study are reasonably high molecular weight samples and there is no molecular weight dependence of their solubility parameter. Therefore, the decrease in DMDBS phase separation temperature for lower molecular weights cannot be rationalized using thermodynamic arguments. This molecular weight dependence appears to be unique to isotactic polypropylene and is not observed for either syndiotactic polypropylene or for random copolymers of isotactic polypropylene containing ethylene comonomer.

The Effect of Polymer Molecular Weight on Citrate Crosslinked Chitosan Films for Site-Specific Delivery of a Non-Polar Drug

Purpose: To develop citrate crosslinked chitosan films using chitosan of different molecular weights (MW) in order to achieve site-specific delivery of a model non-polar drug, indomethacin.Methods: Films prepared with different molecular weights of chitosan and incorporating indomethacin as a non-polar model drug were obtained by a casting/solvent evaporation method. The chitosan films were crosslinked by dipping in varying concentrations of sodium citrate solution and for different crosslinking times. The films were assessed by, amongst others, scanning electron microscopy (SEM), dissolution studies and differential scanning calorimetry (DSC) for surface morphology, drug release and ingredient compatibility, respectively.Results: Crosslinking time and concentration of crosslinking agent significantly (p < 0.05) influenced the in vitro release of indomethacin as well as swelling of the films. Also, the higher the molecular weight (MW) of chitosan the lower the drug release rate (p < 0.05). Furthermore, film swelling index rose as chitosan MW decreased (p < 0.05). The practical absence of the sharp endothermic peak characteristic of indomethacin in the films suggests that crosslinking may have transformed the drug from the crystalline to the amorphous state.Conclusion: The citrate-crosslinked chitosan films can be modulated to vary swelling and drug release at pH 3.5 and 6.2; this feature makes them useful tools for designing site-specific delivery systems.Keywords: Chitosan film, Sodium citrate, Site-specific delivery, Crosslinking, IndomethacinTropical Journal of Pharmaceutical Research December 2010; 9 (6): 525-531

Effects of Polymer Molecular Weight on the Interaction between Acid Dyes and Poly(vinylpyrrolidone) in Inkjet Ink for Textiles

The detailed understanding of the interaction between dyes and additives in the practical service condition is required to develop an inkjet ink for textiles. In the present study, the interaction between three acid dyes (C. I. Acid Red 88, 13, and 27) and a water-soluble polymer, poly(vinylpyrrolidone) (PVP), with different molecular weight was investigated. The binding constants of the dyes with PVP, Kbind, were determined by means of the visible absorption spectrum measurements. The Kbind values decreased with an increase in the number of sulfonate groups in the acid dyes (an increase in the solubility of the dyes in water). This suggests that the affinity to PVP decreases with increasing water solubility. Furthermore, the binding constants were diminished by increasing molecular weight of PVP. It is presumably due to the conformation change of PVP with molecular weight. For further discussion, the thermodynamic parameters for the binding, viz. the enthalpy change, ΔHbind, and the entropy change, ΔSbind, were determined from the temperature dependence of Kbind. The ΔHbind values for all the dyes were negative, showing that the binding processes are exothermic. The absolute values of ΔHbind decreased with the increase in the number of sulfonate groups in the dye molecules. On the other hand, the increase of PVP molecular weight made the thermodynamic process to be less enthalpic and more entropic. Thus, the nature of the interaction should be affected by PVP molecular weight, because the polymer conformation is strongly influenced by the molecular weight.

Chitosan microparticles loaded with exotoxin A subunit antigen for intranasal vaccination against Pseudomonas aeruginosa: An in vitro study

Chitosan microparticles (CMs) were prepared with tripolyphosphate by spray-drying. Effects of polymer molecular weight, sonication power, cross-linking time and concentration of TPP on release profiles of catalytic or third domain pseudomonas exotoxin A (PEIII) and morphology of CMs were evaluated. The mean particle sizes of CMs were in the range from 1.09–1.46 μm and antigen loading efficiencies were more than 59%. As the molecular weight of chitosan increased, microparticles had a more spherical shape and a smooth surface. An increase in sonication power and decrease in cross-linking time resulted microparticles morphology changes. Approximately 60–80% of PEIII released from microparticles within the first few hours. The release of antigen is increased significantly by raising the sonication power more than 45 W. When the cross-linking time extended from 15 to 60 min, the release of PEIII significantly reduced. The release of PEIII from the microparticles increased when concentration of TPP was raised.

Effects of Polymer Molecular Weight on the Size, Activity, and Stability of PEG-Functionalized Trypsin

Polymer conjugation increases an enzyme's circulation time and stability for use as a therapeutic agent, but this attachment indubitably affects its properties. Covalent attachment of multiple polyethylene glycol chains with sizes of either 2, 5, 10, or 20 kDa increases the molecular weight and hydrodynamic radius of the model enzyme trypsin. The sizes of these polymer-enzyme conjugates are increased to be within the recommended limits for PDEPT applications. The T(d) increases from 49 to 60 °C to expand the enzyme's workable range of conditions. This functionalization with PEG polymers of varying lengths maintains trypsin's enzymatic activity. Conjugate activities are 79-120% that of native trypsin at room temperature and 221-432% that of trypsin at 37 °C.

Nicotine Fast Dissolving Films Made of Maltodextrins: A Feasibility Study

This work aimed to develop a fast-dissolving film made of low dextrose equivalent maltodextrins (MDX) containing nicotine hydrogen tartrate salt (NHT). Particular attention was given to the selection of the suitable taste-masking agent (TMA) and the characterisation of the ductility and flexibility under different mechanical stresses. MDX with two different dextrose equivalents (DEs), namely DE 6 and DE 12, were selected in order to evaluate the effect of polymer molecular weight on film tensile properties. The bitterness and astringency intensity of NHT and the suppression effect of several TMA were evaluated by a Taste-Sensing System. The films were characterised in term of NHT content, tensile properties, disintegration time and drug dissolution test. As expected, placebo films made of MDX DE 6 appeared stiffer and less ductile than film prepared using MDX DE 12. The films disintegrated within 10 s. Among the tested TMA, the milk and mint flavours resulted particularly suitable to mask the taste of NHT. The addition of NHT and taste-masking agents affected film tensile properties; however, the effect of the addition of these components can be counterweighted by modulating the glycerine content and/or the MDX molecular weight. The feasibility of NHT loaded fast-dissolving films was demonstrated.

Predicting the Phase Behavior of Polymer Systems with the GC-SAFT-VR Approach

The recently developed heteronuclear group contribution SAFT-VR equation (GC-SAFT-VR) [Peng et al. Fluid Phase Equilib. 2009, 227 (2), 131-144] enables the predictive study of the thermodynamic properties of fluids and their mixtures by using a molecular-based model in which the molecules are described by heterosegmented chains in which each type of segment represents a functional group present in the molecule. Given the success of the GC-SAFT-VR approach in predicting the fluid phase equilibria of mixtures without fitting to any mixture data, and the known difficulties in determining equation-of-state parameters for polymers because of the lack of coexistance data, in this work, we extend the GC-SAFT-VR equation to study the phase equilibria of small molecules in polymer systems. The results demonstrate the ability of the GC-SAFTVR equation of state to predict the vapor-liquid and liquid-liquid equilibria of polymer solutions and accurately capture the effects of polymer molecular weight and molecular topology on phase behavior.

Chitosan-Mediated siRNA Delivery In Vitro: Effect of Polymer Molecular Weight, Concentration and Salt Forms

The aim of this study was to investigate chitosan/siRNA complexes formulated with various chitosan salts (CS) including chitosan aspartate (CS-Asp), chitosan glutamate (CS-Glu), chitosan acetate (CS-Ac), and chitosan hydrochloride (CS-HCl) for in vitro siRNA delivery into stable and constitutive enhanced green fluorescent protein (EGFP)-expressing HeLa cells. The CS/siRNA complexes were characterized by 2% agarose gel electrophoresis and investigated for their transfection efficiency in stable and constitutive EGFP-expressing HeLa cells. The cytotoxicity of the complexes was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The formation of complexes CS/siRNA is mainly dependent on the weight ratio, whereas salt form and molecular weight has less effect. The particle sizes of the complete complexes were in the range of 270-373 nm except the complete complex of CS-Ac, with a slightly positive charge of less than 2 mV. The ability of CS to transfer functionally active siRNA into cell culture is mainly dependent on the weight ratio and molecular weight of CS whereas salt form of CS has less effect. The high gene-silencing efficiency was observed with low MW of CS (20 kDa) and high weight ratio of 32. Over 80% average cell viabilities were observed for CS/siRNA complexes in all weight ratios comparison to untreated cells. This study suggests CS salts have the potential to be used as safe siRNA delivery vectors.

Polymer–protein conjugates: an enzymatic activity perspective

Proteins have been modified with polymers in diverse manners over the past 30 years. However, while proteins have been used to prepare many functional constructs, they are sensitive biomolecules and their bioactivity can be either positively or negatively influenced by many different aspects of polymer modification. The primary focus of this review article is to highlight the opportunities offered by new trends in protein modification, and specifically how they influence the overall biological activity of the conjugate, including its dependence on temperature and pH. We survey the effect of polymer molecular weight, number of conjugated polymer chains, polymer coupling strategy (including random versus site-specific coupling, “grafting from”, and multi-point covalent attachment), polymer architecture (including branched and comb-type), polymer interactions with the protein (including electrostatic and host–guest interactions), polymer interactions with enzyme substrate, and polymer biodegradability. We have selected six enzymes, which have been extensively modified with polymers in diverse fashions in the literature, as basis for this discussion. These proteins are L-asparaginase, alpha-chymotrypsin, trypsin, lysozyme, bovine serum albumin, and papain. This review includes polymers such as poly(ethylene glycol) (PEG), polysaccharides, polypeptides, and other synthetic (vinyl) polymers. From the discussed literature we attempt to extract tentative general trends observed between state-of-the-art methods of preparing protein–polymer conjugates and the activity of the conjugate.

Effect of Polymer Molecular Weight on the Electrospinning of Polylactides in Entangled and Aligned Fiber Forms

Thin fibers having diameters ranging from 25 nm to 2 micro-m were successfully electrospun from solutions of polylactides (PLA) having different molecular weights both in entangled and aligned fiber forms. The latter aligned fibers were collected with a new target comprising a rotor around which several fins were attached. Low viscosity of the solutions resulted in formation of beads or beads-on-strings, while high viscosity gave homogeneous fibers at optimum conditions. The resultant aligned fibers were drawn to 2 - 3 times at various optimum temperatures. WAXD of the drawn fibers revealed smectic nature of the PLA chain arrangement in spite of crystal orientation supported. The mechanical properties of the PLA fibers were also improved after drawing.

Shear-Induced Nanometer and Micrometer Structural Responses in Nanocomposite Hydrogels

The structural responses of a polymer−clay nanocomposite hydrogel to an imposed shear field are investigated from the nanometer to the micrometer length scales. The effects of polymer molecular weight and concentration of the components are probed, and the structural response of the individual components is explored using contrast matching techniques with small-angle neutron scattering. At rest the clay structure appears minimally perturbed by the presence of the polymer. As the network begins to be disrupted under the effect of low shear, large-scale inhomogeneities roll up and orient with their long axis parallel to the neutral direction. With increasing shear rates the effect of the polymer−clay interactions becomes apparent with nanoscopic orientation of both the clay platelets and the polymer chains, but only in systems where polymer bridging of the clay can occur. The clay and polymer concentration dependence of the shear response suggests an ideal combination of concentrations and polymer molecular weights with implications for materials design.