Polymer Mass Ratio Research Articles

Optimization of the synthesis procedure of microparticles containing gold for the selective oxidation of glycerol

Microencapsulation of gold particles was carried out by means of in situ polymerization of urea and formaldehyde. The influence of the amount of organic solvent (dimethyl sulfide) and the gold precursor to polymer mass ratio (Au/PUF) on the encapsulation process and the physical properties of the resulting catalysts have been studied. The amount of DMS has a marked influence on the morphology of the microparticles, affecting to both the porosity outer surface and the encapsulated gold particle size. Synthesized poly(urea-formaldehyde) microparticles containing gold were tested in the liquid phase selective oxidation of glycerol. Obtained results showed that both the amount of DMS and the Au/PUF mass ratio played an important role in the deposition of the gold particles and, consequently, in its catalytic response.

Dissolution rate enhancement of sulfamethoxazole using the gas anti-solvent (GAS) process

The aim of this work was to improve the dissolution rate of a poorly water-soluble antibiotic drug, sulfamethoxazole (SMX), by precipitation and co-precipitation with poly(vinylpyrrolidone) (PVP) using the gas anti-solvent (GAS) process. In the precipitation study, the effects of solvent type (acetone, methanol and ethanol), temperature (35, 40, and 45°C) and percent drug saturation (25, 50 and 75%) on the particle size were investigated using the Box-Behnken design of experiment. It was found that an increase in temperature resulted in a reduction in particle size. Moreover, smaller precipitates were produced when using ethanol as a solvent. An increase in percent saturation of the drug in acetone yielded larger particle size. It was also found that after passing through a 200 mesh sieve the precipitates obtained from the GAS process exhibited a higher dissolution rate than the micronized starting material. In the co-precipitation study, it was found that when using a mass ratio of drug and PVP polymer of 1:1, at 50% drug saturation in methanol and 35°C, the highest % drug content (50.0%) was achieved. The dissolution rate of the prepared composites was found to be 10 times greater than that of the GAS precipitates.

Probing the weak interaction of proteins with neutral and zwitterionic antifouling polymers

Protein–polymer interactions are of great interest in a wide range of scientific and technological applications. Neutral poly(ethylene glycol) (PEG) and zwitterionic poly(sulfobetaine methacrylate) (pSBMA) are two well-known nonfouling materials that exhibit strong surface resistance to proteins. However, it still remains unclear or unexplored how PEG and pSBMA interact with proteins in solution. In this work, we examine the interactions between two model proteins (bovine serum albumin and lysozyme) and two typical antifouling polymers of PEG and pSBMA in aqueous solution using fluorescence spectroscopy, atomic force microscopy and nuclear magnetic resonance. The effect of protein:polymer mass ratios on the interactions is also examined. Collective data clearly demonstrate the existence of weak hydrophobic interactions between PEG and proteins, while there are no detectable interactions between pSBMA and proteins. The elimination of protein interaction with pSBMA could be due to an enhanced surface hydration of zwitterionic groups in pSBMA. New evidence is given to demonstrate the interactions between PEG and proteins, which are often neglected in the literature because the PEG–protein interactions are weak and reversible, as well as the structural change caused by hydrophobic interaction. This work provides a better fundamental understanding of the intrinsic structure–activity relationship of polymers underlying polymer–protein interactions, which are important for designing new biomaterials for biosensor, medical diagnostics and drug delivery applications.

Targeted delivery of 10-hydroxycamptothecin to human breast cancers by cyclic RGD-modified lipid–polymer hybrid nanoparticles

Lipid–polymer hybrid nanoparticles (NPs) combining the positive attributes of both liposomes and polymeric NPs are increasingly being considered as promising candidates to carry therapeutic agents safely and efficiently into targeted sites. Herein, a modified emulsification technique was developed and optimized for the targeting lipid–polymer hybrid NPs fabrication; the surface properties and stability of the hybrid NPs were systematically investigated, which confirmed that the hybrid NPs consisted of a poly (lactide-co-glycolide) core with ∼90% surface coverage of the lipid monolayer and a ∼4.4 nm hydrated polyethylene glycol (PEG) shell. Optimization results showed that the lipid:polymer mass ratio and the lipid-PEG:lipid molar ratio could affect the size, lipid association efficiency and stability of hybrid NPs. Furthermore, a model chemotherapy drug, 10-hydroxycamptothecin, was encapsulated into hybrid NPs with a higher drug loading compared to PLGA NPs. Surface modification of the lipid layer and the PEG conjugated targeting ligand did not affect their drug release kinetics. Finally, the cytotoxicity and cellular uptake studies indicated that the lipid coverage and the c(RGDyk) conjugation of the hybrid NPs gained a significantly enhanced ability of cell killing and endocytosis. Our results suggested that lipid–polymer hybrid NPs prepared by the modified emulsion technique have great potential to be utilized as an engineered drug delivery system with precise control ability of surface targeting modification.

Surface coating of l-glutamine solid microparticles for enteric delivery

The objective of this work was to produce enteric delivery systems to minimize gastric degradation of bioactives, using l-glutamine microparticles as a model, by surface-coating with a layer of enteric polymer (hydroxypropyl methylcellulose phthalate). Suspensions of solid glutamine microparticles in a methanol solution with enteric polymer and different concentrations of plasticizer (glycerol or triethyl citrate) and medium chain fatty acids (MCFA) were spray-dried at 55°C. Spray-dried powders were characterized for in vitro release kinetics in simulated gastric (pH 1.2) and intestinal (pH 6.8) fluids at 37°C. At a MCFA:polymer mass ratio of 2:1, formulations with plasticizer used at 30% of polymer mass resulted in <30% glutamine release after 2h and <40% after 4h at pH 1.2. At pH 6.8, complete release of glutamine was observed for most samples after 4h. Our work demonstrated a simple approach for enteric delivery of food and pharmaceutical compounds.

SYNTHESIS AND CHARACTERIZATION OF GENIPIN CROSS-LINKED OLIGOETHYLENIMINE FOR GENE DELIVERY

A novel fluorescent cationic polymer, genipin cross-linked branched oligoethylenimine (1800 Da, OEI1800), GP, was successfully synthesized in 70% ethanol solution and evaluated as a non-viral gene carrier. The copolymers were characterized by nuclear magnetic resonance spectroscopy ((1)H-NMR) and gel permeation chromatography (GPC). The complexes of copolymers/DNA based on GP were measured by dynamic light scattering and Zeta potential instrument. The results showed that the synthesized copolymers could efficiently condense DNA into nanosized particles (120 similar to 150 nm) with positive surface charges (+ 20 similar to 25 mV). The DNA-binding ability of the copolymers was further examined by gel retardation assy. When the mass ratio of polymer and DNA was 0.25, the plasmids were fully retarded in 1% agarose gel by gel retardation electrophoresis. Moreover, the in vitro cytotoxicity and transfection efficiency of the GP copolymers were respectively tested by the MTT and luciferase assay,using OEI1800 and PEI25k as the control in the HEK293 cells lines. The cell toxicity and gene transfection evaluations showed that the copolymers exhibited lower cytotoxicity and higher gene transfection efficiency than PEI25k in the HEK293 cell lines. Finally, the carriers could be used as the fluorescent labeling materials. Therefore, the copolymers may have potential biomedical application as non-viral gene carriers.

Altering the drug release profiles of double-layered ternary-phase microparticles

Double-layered ternary-phase microparticles composed of a poly( d,l-lactide-co-glycolide) (50:50) (PLGA) core and a poly( l-lactide) (PLLA) shell impregnated with poly(caprolactone) (PCL) particulates were loaded with ibuprofen (IBU) and metoclopramide HCl (MCA) through a one-step fabrication process. MCA and IBU were localized in the PLGA core and in the shell, respectively. The aim of this study was to study the drug release profiles of these double-layered ternary-phase microparticles in comparison to binary-phase PLLA(shell)/PLGA(core) microparticles and neat microparticles. The particle morphologies, configurations and drug distributions were determined using scanning electron microscopy (SEM) and Raman mapping. The presence of PCL in the PLLA shell gave rise to an intermediate release rate of MCA between that of neat and binary-phase microparticles. The ternary-phase microparticles were also shown to have better controlled release of IBU than binary-phase microparticles. The drug release rates for MCA and IBU could be altered by changing the polymer mass ratios. Ternary-phase microparticles, therefore, provide more degrees of freedom in preparing microparticles with a variety of release profiles and kinetics.

Magnolol entrapped ultra-fine fibrous mats electrospun from poly(ethylene glycol)-b-poly(L-lactide) and in vitro release

Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly(ethylene glycol) blocked poly(L-lactide). Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry. According to in vitro drug release investigation by high performance liquid chromatography, it was found that fibers with 10%, 20% and 30% drug entrapped respect to polymer (mass ratio) presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K. The reason may be that fibers with 10% drug entrapped was more easily affected by enzyme while, to some degree, magnolol in fibers with 20% and 30% entrapped prevented polymer from being degraded by enzyme.

Statistical analysis of low molecular mass heparin Nanoencapsulation

The objective of this study was to use Box-Behnken design (BBD) to investigate the influence of formulation variables on the properties of heparin-loaded poly(lactic-coglycolic acid) (PLGA)-polymethacrylate-RLPO (E-RLPO) nanoparticles (NP) in terms of mean diameter (as size) and drug encapsulation efficiency. The NPs were prepared by the double emulsion solvent evaporation method. The independent variables were: X1 - polymer mass ratio (PLGA:E-RLPO) in the oil phase, X2 - concentration of polyvinyl alcohol (PVA) as emulsion stabilizer, and X3 - volume of the external aqueous phase (W2). Particle size (analyzed by dynamic light scattering) and encapsulation efficiency (EE, estimated by spectrophotometry) were the investigated responses. The polynomial equation obtained from regression analysis of the reduced model (p = 0.0002, F = 25.7952 and R2 = 0.96) provided an excellent fit. The optimal size for the NP was found to be 134.2 ± 16.5 nm with formulation variables of 48.2:61.8, 0.321 (%,m/V) and 263 mL for X1, X2 and X3, respectively. Probably, due to electrostatic interaction between the negatively charged drug and the positively charged E-RLPO, the percent EE of heparin was between 74.4 ± 6.5 % (lowest value) and 92.1 ± 5.3 % (highest value). The data suggest that BBD is a useful tool in rational design of heparin-loaded NPs.

One‐Step Fabrication of Triple‐Layered Polymeric Microparticles with Layer Localization of Drugs as a Novel Drug‐Delivery System

Particulate systems have tremendous potential to achieve controlled release and targeted delivery of drugs. However, conventional single-layered particles have several inherent limitations, including initial burst release, the inability to provide zero-order release, and a lack of time-delayed or pulsatile release of therapeutic agents. Multilayered particles have the potential to overcome these disadvantages. Herein, it is shown how triple-layered polymeric microparticles can be fabricated through a simple, economical, reliable, and versatile one-step solvent evaporation technique. Particle morphologies and layer configurations are determined by scanning electron microscopy, polymer dissolution tests, and Raman mapping. Key fabrication parameters that affect the formation of triple-layered polymeric microparticles comprising poly(DL-lactide-co-glycolide) (50:50), poly(L-lactide), and poly(ethylene-co-vinyl acetate) (40 wt% vinyl acetate) are discussed, along with their formation mechanisms. Layer thickness and the configurations of these microparticles are altered by changing the polymer mass ratios. Finally, it is shown that drugs can be localized in specific layers of the microparticles. This fabrication process can therefore be used to tailor microparticle designs, thus allowing such "designer" particulate drug-delivery systems to function across a wide range of applications.

Gamma radiation synthesis and swelling properties of hydrogels based on poly(ethylene glycol)/methacrylic acid (MAc) mixtures

AbstractIn this work, gamma radiation was used to prepare hydrophilic hydrogels based on different mass ratios of poly(ethylene glycol) (PEG) and methacrylic acid (MAc) monomer. The thermal stability of hydrogels was characterized thermogravimetric analysis (TGA). The effect of temperature and pH, as external environments, on the equilibrium swelling of PEG/MAc hydrogels was also studied. The results showed that the gel fraction of PEG/MAc hydrogels is lower than that of PMAc hydrogel, in which the gel fraction of PMAc hydrogel was decreased greatly with increasing the mass ratio of PEG polymer in the initial solutions. The results showed that PEG/MAc hydrogels reached the equilibrium swelling state in water after 6 hours. It was found that the equilibrium swelling of PEG/MAc hydrogels displayed a transition change within the temperature range 30–40°C. This change in equilibrium swelling was illustrated by differential scanning calorimetry (DSC). However, it was observed that the equilibrium swelling of PEG/MAc hydrogels increases progressively with increasing the pH value from 4 up to 8. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Morphological characteristics of selenium-containing nanostructures based on rigid-chain molecules

Selenium-containing nanostructures of rigid-chain polymers with close molecular masses were studied by flow birefringence (FB) and static and dynamic light scattering at a fixed selenium to polymer mass ratio ν = 0.1 in solution. The group of polymers under study included the cationic polyelectrolyte poly-N,N,N,N-trimethylmethacryloyloxyethylammonium methyl sulfate, anionic polyelectrolyte carboxymethylcellulose, and nonionogen polymer oxyethylcellulose. High-molecular selenium-containing polymer nanostructures were found in all cases. Nanostructures with a maximum molecular mass and the largest number of constituent macromolecules were obtained using oxyethylcellulose. At ν = 0.1 the mean square radii of inertia of the nanostructures were almost independent of the nature of the polymer matrix. The thermodynamic state of the solutions of nanostructures was close to the ideal one in all cases. For the region where stable dispersions formed, the Gibbs energies of macromolecule-selenium nanoparticle interactions were calculated and shown to be almost independent of the nature of the polymer matrix at ν = 0.1. The close mean square radii of inertia Rg* of the nanostructures, the Gibbs energies of interaction, and the equivalence of the thermodynamic state of the solutions of nanostructures obtained for all polymer matrices at ν = 0.1 suggest that ν = 0.1 corresponds to the ultimate adsorption capacity of selenium nanoparticles; the considerable differences between the molecular masses (for close Rg* values), mean densities, and structural conformation parameters ρ* point to different packings of macromolecules in the nanostructures under study.

Mechanical and acoustic performance of compression‐molded open‐cell polypropylene foams

AbstractOpen‐cell materials are lightweight and multifunctional capable of absorbing acoustic energy and supporting mechanical load. The acoustic and mechanical performance of open‐cell materials can be optimized through processing. In this article, the relationships between processing parameters and acoustic and mechanical performance are shown for polypropylene (PP) foams. PP foam samples are fabricated using a combined compression molding and particulate leaching process. The results from a parametric study showed that both salt size and salt to polymer ratio affect the acoustic and mechanical performance of open‐cell PP foams. As salt size increases, cell size increased and cell density decreased. The salt to polymer ratio had opposite affect on cell density, and increasing the salt to polymer mass ratio increased the open‐cell content. The airflow resistivity decreased significantly by increasing the cell size, which means that foam samples with smaller cell size have better sound absorption. When foam samples were thin, smaller cell sizes produced better sound absorption; however, as thickness of the sample increases, medium cell size offered the best acoustic performance. The compressive strength of the foams was increased by increasing the relative density. Acoustic performance results from the parametric study were compared to the Johnson‐Allard model with good agreement. Finally, optimal cellular morphologies for acoustic absorption and mechanical performance were identified. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Manipulation of process parameters to achieve different ternary phase microparticle configurations

Ternary phase microparticles of poly( d, l-lactide-co-glycolide) (50:50), poly( l-lactide) and poly(caprolactone) were fabricated through a one-step solvent evaporation technique. The purpose of this study was to examine the effects of various process parameters on the final configuration (i.e. polymer distribution and dimensions) of these composite microparticles and, subsequently, propose their mechanism of formation. Particle morphologies and configurations were determined using scanning electron microscopy, polymer dissolution tests and Raman mapping. It was found that a starting polymer solution prepared below the cloud point and an increased oil to water ratio will facilitate polymer configurations close to thermodynamic equilibrium, which is dictated by the interfacial energies of the components. By varying the polymer mass ratio or adjusting the precipitation rate, through stirring speed and oil to water ratio, a wide range of microparticles with different core–shell dimensions and embedded particulate sizes can also be fabricated. At the same time, lowering the polymer solution concentration and increasing the stirring speed may result in smaller microparticles. Correlation of these process parameters with the final composite particle morphology was thus established. This understanding should allow the controlled fabrication of ternary phase composite microparticles through a single step solvent evaporation technique.

A comprehensive study of the interactions between DNA and poly(3,4-ethylenedioxythiophene)

The interaction between poly(3,4-ethylenedioxythiophene), a conducting polymer with excellent electrical and electrochemical properties, and plasmid DNA has been investigated using electrophoresis, UV–visible and CD spectroscopy, and quantum mechanical calculations. Analyses of mixtures with different DNA:polymer mass ratios indicate that, in all cases, interactions form immediately and induce structural alterations in DNA. Furthermore, the existence of interactions between poly(3,4-ethylenedioxythiophene) and specific nucleotides sequences has been evidenced by adding restriction enzymes to the mixtures. In contrast, interactions between DNA and poly(3-methylthiophene), a similar polyheterocyclic conducting polymer but without hydrogen bonding acceptors, are weak or do not exist. These results suggest that, in addition to non-specific electrostatic interactions between the charged phosphate groups of DNA and the positively charged fragments of the conducing polymers, specific hydrogen bonding interactions play a crucial role. The ability of 3,4-ethylenedioxythiophene units to form hydrogen bonds with the methylated analogues of DNA bases has been examined in different environments using MP2/6-31G(d) and MP2/6-311++G(d,p) calculations. Results indicate that, in environments with low polarity, the formed interactions are significantly stronger than those reached by unsubstituted thiophene and similar to those established by pyrrole. However, in polar environments (aqueous solution) 3,4-ethylenedioxythiophene provides stronger interactions with nucleic acids than both thiophene and pyrrole. These theoretical results are fully consistent with experimental observations.

Cloud-point measurement for (sulphate salts + polyethylene glycol 15000 + water) systems by the particle counting method

The phase separation of (water + salt + polyethylene glycol 15000) systems was studied by cloud-point measurements using the particle counting method. The effect of three kinds of sulphate salt (Na 2SO 4, K 2SO 4, (NH 4) 2SO 4) concentration, polyethylene glycol 15000 concentration, mass ratio of polymer to salt on the cloud-point temperature of these systems have been investigated. The results obtained indicate that the cloud-point temperatures decrease linearly with increase in polyethylene glycol concentrations for different salts. Also, the cloud points decrease with an increase in mass ratio of salt to polymer.

Closed-Packed Colloidal Assemblies from Icosahedral Plant Virus and Polymer

A practical process to synthesize bio-colloidal composites was developed on the basis of the noncovalent interactions of icosahedral plant virus turnip yellow mosaic virus (TYMV) and poly(4-vinylpyridine) (P4VP). TYMV particles fully covered the surface of a P4VP ball with a hexagon-like packing. The raspberry-like morphology of TYMV-P4VP colloids and the packing pattern of TYMV were revealed by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), dynamic light scattering (DLS), and synchrotron small-angle X-ray scattering (SAXS). The size of TYMV-P4VP colloids was controlled readily by varying the mass ratio of virus and polymer. A simplified model was established to explain the experimental data.

The first solid-phase route to fabricate and size-tune gold nanoparticles at room temperature

Gold nanoparticles have attracted considerable interest due to their salient properties and many methods for their fabrication have been developed. In this study, for the first time a solid state method for their synthesis has been designed and developed. Thus, high-speed vibration milling has been used for the synthesis of gold nanoparticles, where sodium borohydride was used for the reduction of the gold salt. Poly(vinylpyrrolidone) was used as a protecting agent for the gold nanoparticles synthesized. This system used for the synthesis of the gold nanoparticles required only room temperature and yielded mostly polyhedral nanoparticles with diameters ranging from 6.3 ± 2.1 to 27.9 ± 6.2 nm. The size of the nanoparticles was tunable by varying different reaction parameters such as the molar mass of polymer protecting agent, reaction time, and the mass ratio of gold precursor and polymer protecting agent. The nanoparticles were characterized by UV-visible spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, and powder X-ray diffraction techniques.

Study of photoluminescence quenching and DC conductivity measurements in polymer-SWNT composite films for various SWNT concentrations

Conducting polymer-SWNT composite films have a high potential in the area of photovoltaic devices and light emitting diodes (LEDs). SWNTs have high electron affinity and high mobility for electrons. As a result of this, the separation of photoinduced charges in the solar cell is very fast and efficient. For LEDs, the polymer-SWNT composite films act as efficient electron transporting layer (ETL). In the present work, composite solutions of P3HT and SWNTs were prepared in 1,2-dichlorobenzene with nanotube to polymer mass ratios varied from 0% to 30%. The films from this solution were spin coated on a glass substrate with the help of spinner keeping the film thickness ∼100 nm. The photoluminescence (PL) of the film was observed with the help of Shimadzu Spectrofluorophotometer. It was found that the PL intensity decreases by ∼90% as the concentration of the SWNT is increased from 0% to 30%. This decrease is due to the transfer of electrons from P3HT to SWNTs before the exciton in the polymer can decay radiatively to emit PL. DC conductivity of the composite films was measured with the help of Keithley sourcemeter in sandwich structures. It was found that conductivity increases by more than five orders of magnitude with the increase of SWNT concentration. The composite films can therefore act as good electron transporter for LEDs and efficient electron acceptor for solar cells.

Production of theophylline and polyethylene glycol 4000 composites using Gas Anti-Solvent (GAS) process

Production of drug composites can be used to enhance the dissolution rate of poorly-water soluble drugs. In this research, Gas Anti-Solvent (GAS) technique was applied to produce composites between theophylline (THEO) and polyethylene glycol (PEG) by using dense carbon dioxide as an anti-solvent. It was found that the size of the composites decreased as the concentration of PEG 4000 decreased. However, when increasing the temperature the degree of aggregation and particles size were increased. It was also found that a decrease in ethanol amount in the solvent mixture of dichloromethane and ethanol resulted in a decrease of particle size. The theophylline–PEG composites with the highest drug loading of 16.70% were obtained when using the mass ratio of drug and polymer at 2:3 wt.% in the dichloromethane and ethanol solvent of 50:50%v/v and 25 °C. The dissolution rate of the prepared composites in phosphate buffered solution was found to be 20.8 times greater than that of the original material.