Use Of Polymers Research Articles

Development and chemical characterization of biodegradable polymeric implants containing sirolimus for the treatment of malignant solid tumors.

The use of sirolimus and its analogs has been evaluated in studies aimed at combating several types of cancer; however, because of the limited bioavailability of the drug, the search for new forms of administration is required. Biodegradable polymeric implants containing sirolimus were developed and assessed as an alternative method of drug administration. Implants containing 25 % (w/w) sirolimus were prepared employing the polymer matrices chitosan, polycaprolactone and poly(lactic-co-glycolic acid) (PLGA) in two proportions: PLGA 50:50 and PLGA 75:25. Thermal analysis techniques such as thermogravimetry and differential scanning calorimetry, combined with x-ray diffraction were used to characterize and evaluate the compatibility of the constituents of the formulation. No incompatibilities were found between the components, but drug amorphization was observed in all samples. Implants made from the polymers chitosan and PCL may accelerate the degradation of SRL when these polymers are dissolved in methanol at 50 °C. HPLC analysis showed that the implant prepared with PLGA 75:25 did not present degradation products and maintained its appropriate drug content, even when dissolved in methanol and heated to 50 °C. Therefore, it represents the most suitable biodegradable polymer for use in implants developed for the treatment of malignant solid tumors. However, it is still necessary to further study the drug effects after amorphization of the crystal and also to perform stability and solubility analysis.

Virtual Issue: Designing Polymers for Use in Electrochemical Energy Storage Devices

Virtual Issue: Designing Polymers for Use in Electrochemical Energy Storage Devices

Tablet of Ximenia Americana L. Developed from Mucoadhesive Polymers for Future Use in Oral Treatment of Fungal Infections.

The use of biocompatible polymers such as Hydroxypropylmethylcellulose (HPMC), Hydroxyethylcellulose (HEC), Carboxymethylcellulose (CMC), and Carbopol in solid formulations results in mucoadhesive systems capable of promoting the prolonged and localized release of Active Pharmaceutical Ingredients (APIs). This strategy represents a technological innovation that can be applied to improving the treatment of oral infections, such as oral candidiasis. Therefore, the aim of this study was to develop a tablet of Ximenia americana L. from mucoadhesive polymers for use in the treatment of oral candidiasis. An X. americana extract (MIC of 125 μg·mL−1) was obtained by turbolysis at 50% of ethanol, a level that demonstrated activity against Candida albicans. Differential Thermal Analysis and Fourier Transform Infrared Spectroscopy techniques allowed the choice of HPMC as a mucoadhesive agent, besides polyvinylpyrrolidone, magnesium stearate, and mannitol to integrate the formulation of X. americana. These excipients were granulated with an ethanolic solution 70% v/v at PVP 5%, and a mucoadhesive tablet was obtained by compression. Finally, mucoadhesive strength was evaluated, and the results demonstrated good mucoadhesive forces in mucin disk and pig buccal mucosa. Therefore, the study allowed a new alternative to be developed for the treatment of buccal candidiasis, one which overcomes the inconveniences of common treatments, costs little, and facilitates patients’ adhesion.

Recent advances in the orientation of conjugated polymers for organic field-effect transistors

This review summarizes recent advancements in various orientation techniques for conjugated polymers for use in high performance organic field effect transistors.

Improvement of Polypropylene Adhesion by Kraft Lignin Incorporation

Low surface energy and poor adhesion are well-known characteristics of polypropylene (PP). Surface treatments such as plasma, corona, and laser are usually applied to overcome these limitations. However, current studies highlight the incorporation of hydrophilic or amphiphilic polymers into hydrophobic low-surface-energy polymers as an alternative for increasing surface energy and thus improving adhesion. Lignin could be a promising amphiphilic polymer for use in increasing surface energy. In this work, PP/kraft lignin composites were obtained by incorporating up to 5 wt% of kraft lignin (KL) into a PP matrix. Corona treatment was applied to pristine PP and composites surfaces. Contact angle measurements and peeling tests were carried out to investigate the effects of KL incorporation and corona treatment on the surface energy and the mechanical strength of adhesion. Differential scanning calorimetry (DSC) was used to evaluate the PP’s crystallinity index and recrystallization temperature and to dismiss their effects on the surface energy changes. Scanning electron microscopy (SEM) was applied to investigate the lignin dispersion. The results show that KL incorporation has potential as a method to improve the surface energy of PP, improve its poor adhesion, and enhance the effects of corona treatment.

Morphology Driven by Molecular Structure of Thiazole-Based Polymers for Use in Field-Effect Transistors and Solar Cells.

The effects of the molecular structure of thiazole-based polymers on the active layer morphologies and performances of electronic and photovoltaic devices were studied. Thus, thiazole-based conjugated polymers with a novel thiazole-vinylene-thiazole (TzVTz) structure were designed and synthesized. The TzVTz structure was introduced to extend the π conjugation and coplanarity of the polymer chains. By combining alkylthienyl-substituted benzo[1,2-b:4,5-b']dithiophene (BDT) or dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene (DTBDT) electron-donating units and a TzVTz electron-accepting unit, enhanced intermolecular interactions and charge transport were obtained in the novel polymers BDT-TzVTz and DTBDT-TzVTz. With a view to using the polymers in transistor and photovoltaic applications, the molecular self-assembly in and their nanoscale morphologies of the active layers were controlled by thermal annealing to enhance the molecular packing and by introducing a diphenyl ether solvent additive to improve the miscibility between polymer donors and [6,6]phenyl-C71-butyric acid methyl ester (PC71 BM) acceptors, respectively. The morphological characterization of the photoactive layers showed that a higher degree of π-electron delocalization and more favorable molecular packing in DTBDT-TzVTz compared with in BDT-TzVTz leads to distinctly higher performances in transistor and photovoltaic devices. The superior performance of a photovoltaic device incorporating DTBDT-TzVTz was achieved through the superior miscibility of DTBDT-TzVTz with PC71 BM and the improved crystallinity of DTBDT-TzVTz in the nanofibrillar structure.

Numerical Modeling of 193-nm Excimer Laser Ablation on CR-39 Polymer

Laser polymer processing has evolved into an important field of applied and fundamental research. Allyl diglycol carbonate or CR-39 is considered an important polymer for use in optical and medical applications since it is a hard and infusible thermoset plastic that is insoluble in all solvents. The temperature distribution of CR-39 when subjected to irradiation during 193-nm excimer laser ablation was investigated. An effective simulation was developed to reflect the effects of polymer thermal diffusion, laser fluence, beam geometry, and number of pulses. A two-dimensional finite element model was used to predict the temperature distribution and ablation depth in the plastic CR-39 polymer under the 193-nm laser ablation process. The photochemical threshold ablation fluence was 750 mJ/cm2 for a single laser pulse, but dropped to 240 mJ/cm2 for repetitive laser pulses. At higher fluence, thermal effects exhibited a slight contribution to the ablation process. For fluence ≥ 750 mJ/cm2, the ablation depth increased abruptly. It can thus be inferred that the rate of temperature increase with pulse number increased concomitantly with the fluence. Thus, thermal effects are a significant factor in the ablation process.

Proanthocyanidin subunit composition determined by functionally diverged dioxygenases.

Proanthocyanidins (PAs) are primarily composed of the flavan-3-ol subunits (-)-epicatechin and/or (+)-catechin, but the basis for their different starter and extension unit compositions remains unclear. Genetic and biochemical analyses show that, in the model legume Medicago truncatula, two 2-oxoglutarate-dependent dioxygenases, anthocyanidin synthase (ANS) and its homologue leucoanthocyanidin dioxygenase (LDOX), are involved in parallel pathways to generate, respectively, the (-)-epicatechin extension and starter units of PAs, with (+) catechin being an intermediate in the formation of the (-)-epicatechin starter unit. The presence/absence of the LDOX pathway accounts for natural differences in PA compositions across species, and engineering loss of function of ANS or LDOX provides a means to obtain PAs with different compositions and degrees of polymerization for use in food and feed.

Domperidone nanocrystals with boosted oral bioavailability: fabrication, evaluation and molecular insight into the polymer-domperidone nanocrystal interaction.

The aim of this study was to employ experimental and molecular modelling approaches to use molecular level interactions to rationalise the selection of suitable polymers for use in the production of stable domperidone (DOMP) nanocrystals with enhanced bioavailability. A low-energy antisolvent precipitation method was used for the preparation and screening of polymers for stable nanocrystals of DOMP. Ethyl cellulose was found to be very efficient in producing stable DOMP nanocrystals with particle size of 130 ± 3nm. Moreover, the combination of hydroxypropyl methylcellulose and polyvinyl alcohol was also shown to be better in producing DOMP nanocrystals with smaller particle size (200 ± 3.5nm). DOMP nanosuspension stored at 2-8°C and at room temperature (25°C) exhibited better stability compared to the samples stored at 40°C. Crystallinity of the unprocessed and processed DOMP was monitored by differential scanning calorimetry and powder X-ray diffraction. DOMP nanocrystals gave enhanced dissolution rate compared to the unprocessed drug substance. DOMP nanocrystals at a dose of 10mg/kg in rats showed enhanced bioavailability compared to the raw drug substance and marketed formulation. A significant increase in plasma concentration of 2.6μg/mL with a significant decrease in time (1h) to reach maximum plasma concentration was observed for DOMP nanocrystals compared to the raw DOMP. Molecular modelling studies provided underpinning knowledge at the molecular level of the DOMP-polymer nanocrystal interactions and substantiated the experimental studies. This included an understanding of the impact of polymers on the size of nanocrystals and their associated stability characteristics.

In vitro compatibility testing of thiol-ene/acrylate-based shape memory polymers for use in implantable neural interfaces.

Shape memory polymers (SMPs) based on thiol-ene/acrylate formulations are an emerging class of materials with potential applications as structural and/or dielectric coatings for implantable neural interfaces. Here, we report in vitro compatibility studies of three novel thiol-ene/acrylate-based SMP formulations. In vivo cytotoxicity assays were carried out in accordance with International Organization for Standards (ISO) protocol 10993-5, using NCTC clone 929 fibroblasts as well as embryonic cortical cultures. All three SMP formulations passed standardized cytotoxicity assays (>70% normalized cell viability) using both cell types. Functional neurotoxicity assays were carried out using primary cortical networks cultured on substrate-integrated microelectrode arrays (MEAs). We observed significant reduction in cortical network activity in the case of positive control material, but no significant alterations in activity following incubation with SMP material extracts, indicating functional cytocompatibility. Finally, we assessed cell reactivity at the tissue-material interface by performing an in vitro glial scarring assay. Through immunostaining, we observed similar astrocyte-associated (GFAP) mean intensity ratios near nonsoftening SMP-coated and uncoated stainless steel microwires (1.10 ± 0.06 vs. 1.19 ± 0.10), suggesting similar glial cell reactivity. However, we observed decreased mean intensity ratios in the presence of fully softening SMP-coated microwires (1.02 ± 0.04) suggesting reduced glial cell reactivity. Overall, these results indicate that the thiol-ene/acrylate SMP formulations presented here are neither cytotoxic nor neurotoxic, and suggest that fully softening SMP may reduce foreign body response in terms of glial cell reactivity. These findings support further consideration of this class of materials as backbone or insulating materials for implantable neural stimulating/recording devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2891-2898, 2018.

Simultaneous encapsulation of zinc oxide and octocrylene in poly (methyl methacrylate-co-styrene) nanoparticles obtained by miniemulsion polymerization for use in sunscreen formulations

Polymer nanoparticles have been used by the cosmetic industry since the last decade. Nanoencapsulation of sunscreen is performed to prevent photodegradation and skin accumulation, reducing its toxic effects. The aim of this study was to develop a new sunscreen with the simultaneous encapsulation of zinc oxide nanoparticles (ZnO) and octocrylene in poly-styrene-co-methyl methacrylate (PMMA/PS) nanoparticles via minimemulsion polymerization, and to evaluate its efficacy as sunscreen and biocompatibility in human dermal fibroblasts. Both inorganic and organic filters were successfully encapsulated in PMMA/PS nanoparticles with high encapsulation efficiency and physical-chemical properties desirable for use in sunscreens. The obtained nanoparticles (10% or 20%) were incorporated into Artistoflex AVC® gel resulting in a semi-solid formulation with homogeneous aspect and without lumps, color white and pH close to the pH of the skin. The semi-solid formulation containing ZnO and octocrylene in PMMA nanoparticles exhibited a good solar protection factor (SPF > 30) being considered a good UVA sunscreen receiving a 4-star rating according to the Boots Star Rating System. Lastly, cytotoxicity studies on human dermal fibroblasts showed the biocompatibility of sunscreen, this being a promising system for future studies in vivo.

Novel magnetic core-shell nanoparticles for the removal of polychlorinated biphenyls from contaminated water sources.

In this work, we developed novel core-shell nanoparticle systems with magnetic core and polymer shell via atom transfer radical polymerization for use as high affinity nanoadsorbents for organic contaminants in water and wastewater treatment. Polyphenolic-based moieties, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA), were incorporated into poly(ethylene glycol) (PEG) based polymeric shells to create high affinity binding sites for the capture of polychlorinated biphenyls (PCBs) as a model pollutant. The resulting magnetic nanoparticles (MNPs) were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and UV-visible spectroscopy. The affinity of these novel materials for PCB 126 was evaluated and fitted to the nonlinear Langmuir model to determine binding affinities (KD). The KD values obtained were: PEG MNPs (8.42 nM) < IO MNPs (8.23nM) < QMA MNPs (5.88 nM) < CMA MNPs (2.72 nM), demonstrating that the presence of polyphenolic-based moieties enhanced PCB 126 binding affinity, which is hypothesized to be a result of π - π stacking interactions. These values are lower that KD values for activated carbon, providing strong evidence that these novel core-shell nanoparticles have a promising application as nanoadsorbents for specific organic contaminants offering a cost effective alternative to current remediation approaches.

Design rules for a tunable merged-tip microneedle

This publication proposes the use of an elasto-capillarity-driven self-assembly for fabricating a microscale merged-tip structure out of a variety of biocompatible UV-curable polymers for use as a microneedle platform. In addition, the novel merged-tip microstructure constitutes a new class of microneedles, which incorporates the convergence of biocompatible polymer micropillars, leading to the formation of a sharp tip and an open cavity capable of both liquid trapping and volume control. When combined with biocompatible photopolymer micropillar arrays fabricated with photolithography, elasto-capillarity-driven self-assembly provides a means for producing a complex microneedle-like structure without the use of micromolding or micromachining. This publication also explores and defines the design rules by which several fabrication aspects, such as micropillar dimensions, shapes, pattern array configurations, and materials, can be manipulated to produce a customizable microneedle array with controllable cavity volumes, fracture points, and merge profiles. In addition, the incorporation of a modular through-hole micropore membrane base was also investigated as a method for constitutive payload delivery and fluid-sampling functionalities. The flexibility and fabrication simplicity of the merged-tip microneedle platform holds promise in transdermal drug delivery applications.

Mechanistic Insights of BHT-Mg-Catalyzed Ethylene Phosphate's Coordination Ring-Opening Polymerization: DFT Modeling and Experimental Data.

Poly(ethylene phosphates) are promising polymers for use in biomedical applications. Catalytic ring-opening polymerization (ROP) of cyclic ethylene phosphate monomers (CEPMs) is the most effective approach for obtaining these polymers. The mechanism of coordination ROP of CEPMs remains unclear. We report, for the first time, the results of DFT modeling of CEPM ROP. In these calculations by Gaussian-09 program package with the B3PW91/DGTZVP basis set, we explored methyl ethylene phosphate (MeOEP) ROP catalyzed by dimeric and monomeric catalytic species derived from heteroleptic complex [(BHT)Mg(μ-OBn)(THF)]2 (Mg1, BHT = 2,6-di-tert-butyl-4-methylphenolate). Analysis of the reaction profiles for the binuclear and mononuclear reaction mechanisms allowed us to conclude that the ROP of MeOEP is preferentially catalyzed by mononuclear Mg complexes. This estimation was confirmed by comparative polymerization experiments using MeOEP and traditional monomers ε-caprolactone (εCL), racemic lactide (rac-LA), and l-lactide (l-LA) initiated by Mg1. ROP of MeOEP proceeds at an extremely high rate due to the substantially lower activation barrier calculated for mononuclear mechanism in comparison with that of cyclic esters that polymerize without the dissociation of BHT-Mg binuclear species. We also demonstrated the use of MeOEP as a "monomerization" agent in the synthesis of MeOEP-lactide block copolymers. Comparison of the multiple acceleration of l-LA ROP after MeOEP prepolymerization and formation of atactic PLA blocks in rac-LA polymerization with the heterotactic PLA formation during Mg1-catalyzed homopolymerization also confirmed the mononuclear nature of the polyphosphate-containing catalytic particles.

Time-dependent mucoadhesion of conjugated bioadhesive polymers.

The time-dependent bioadhesive performance of various polymers was evaluated using a texture analyzer apparatus and freshly excised rat small intestinal tissue. A series of novel bioadhesive polymers were prepared by conjugating L-phenylalanine, L-tyrosine, and L-DOPA to either a low molecular weight poly (butadiene-maleic anhydride) or a high molecular weight poly (ethylene-maleic anhydride). Bioadhesive force was characterized as a function of time relative to polycarbophil, a slightly cross-linked poly (acrylic acid)-derivative, revealing different fracture strengths and tensile work for each of the six backbone-side chain conjugations that were studied. While polycarbophil showed a rapid and significant loss of bioadhesion over the testing period, the newly developed synthetic polymers were able to maintain their bioadhesive performance over the course of 91 min with the overall magnitude of bioadhesion corresponding to the hydrogen bonding potential of the associated side chains. These results highlight the potential of these polymers for use in the development of more effective bioadhesive oral drug delivery systems.

New Polymer Systems for Use in Organic Photovoltaics

In this paper, new polymers for use in organic photovoltaics were investigated. PPBI, PNBI and copolymer MULT are considered as a potential alternative or an effective dopant for P3HT and PCBM. The choice of these materials allows us to find out new information on the prospects and properties of heterocyclic polymers — for thermal stability and resistance to the environment for organic solar cells. The levels of HOMO and LUMO of new heterocyclic polymers were measured, and the results were compared with those of P3HT: PCBM. The level of new polymer MULT photoluminescence was determined. The absorption blend for P3HT: PCBM peak absorption shift was detected by adding 5% (by mass) of the new polymer MULT, the value of 30–40[Formula: see text]nm to longer wavelengths. Data obtained by cyclic voltammetry showed deep HOMO levels of heterocyclic polymers in values of about [Formula: see text]6[Formula: see text]eV, which is promising in terms of acceptor properties.

Novel Polymers for Use in Total Joint Arthroplasty

Abstract Improving the mechanical properties and wear resistance of polymers used as implant bearing materials requires new approaches and modern technology. This article describes recent work on translating novel materials and coatings into clinical practice to reduce risks and significantly improve orthopedic implant fixation and longevity.

Absorption and Desorption of Superabsorbent Polymers for Use in Internally Cured Concrete

Abstract Superabsorbent polymers (SAP) have been investigated as an additive for use in the manufacture of internally cured concrete. The ability of SAP to absorb and desorb fluid is important for the design of internally cured concrete mixtures. Internal curing research on lightweight aggregates (LWA) has typically focused on the absorption of water in the LWA internal curing agent. However, when SAP is used, the absorption test should be performed using a pore solution with a defined ionic concentration. To address the effect of the ionic composition of the pore solution on SAP absorption, pore solutions were extracted from fresh cementitious pastes, and their composition was evaluated using X-ray fluorescence. This study characterizes the absorption and desorption of a commercially available SAP, using both simulated and extracted pore solutions with a range of ionic concentrations. The teabag method was implemented to measure the absorption of the SAP. As expected, the absorption of the SAP decreased in solutions with higher ionic concentrations. In addition to studying solutions extracted from ordinary portland cement pastes, the effects of the inclusion of supplementary cementitious materials on the SAP absorption were studied. Results showed that the inclusion of supplementary cementitious materials had a relatively minor impact on the SAP absorption, primarily due to a dilution of the ionic concentration of the pore solution. This article examined the desorption of the SAP in two conditions: a reduction in the ambient relative humidity and after exposure of the SAP to solutions with a higher ionic concentration. It was observed that SAP-containing solutions with a higher ionic concentration had a reduced rate of desorption and a reduced overall desorption at a given relative humidity. In addition, moving the SAP from a solution with a lower ionic concentration to a more highly concentrated solution resulted in desorption. An equation was developed that expresses the SAP absorption as a function of the pH of the soaking solution. The expression was used to predict the desorption of SAP due to an increase in the ionic concentrations in a hydrating system. This equation was used to show that the desorption of SAP due to changes in the pore solution ionic concentration were significant during the first 72 hours. The findings and the techniques used in this study are meant to be used as an example for the characterization of SAP in concrete internal curing applications.

Field-dependent electric conductivities of silicone rubbers deduced from measured currents and surface potential decay characteristics

Measurements of DC electric conductivities of four types of silicone rubber-based polymers for use in high voltage insulation systems of power components are reported. The field dependences of the conductivities obtained by two different techniques, namely by utilizing steady-state currents through materials’ samples placed between metallic electrodes and by employing surface potential decay characteristics in an open circuit configuration, are compared and discussed. It is shown that the surface potential decay technique allows for a wider range of electric field strength and reduces the time span of the measurements.

Poly(lactic acid) for Biomedical Application–Synthesis of Biocompatible Mg Catalyst and Optimization of Its Use in Polymerization of Lactide with the Aid of Design of Experiments

An efficient original synthesis of magnesium 2-ethylhexanoate (MgOct2) via reaction of metallic magnesium with 2-ethylhexanoic acid was achieved. The activity of MgOct2 as a biocompatible catalyst for lactide ring-opening polymerization was examined. The process was successfully optimized by using factorial and rotatable designs. Poly(lactic acid) with Mw = 34 000 g/mol with high lactide conversion (>95%) has been obtained. Because the method employs a biocompatible catalyst (lack of tin), it can be used in medical and pharmaceutical applications.