Sônia Faria Zawadzki

HTPB-based Polyurethanes: a Correlation Study Between Morphology and Mechanical Behaviour

Hydroxyl-terminated polybutadiene and tolylene diisocyanate were used to prepare two series of polyurethanes by a two-step process. In the first series, the prepolymers were chain-extended with aliphatic compounds (1,3-propanediol, 1,4-butanediol and 1,6-hexanediol) and in the second, an aromatic chain extender (dihydroxy isopropyl-N-aniline) was used. Some results from mechanical testing showed different trends in comparison with previously reported results for similar systems. These findings were interpreted in terms of reactant reactivity, experimental procedures and morphology. Morphology was studied by means of swelling experiments, differential scanning calorimetry and scanning electron microscopy.

PHBV/PCL Microparticles for Controlled Release of Resveratrol: Physicochemical Characterization, Antioxidant Potential, and Effect on Hemolysis of Human Erythrocytes

Microparticles of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL) containing resveratrol were successfully prepared by simple emulsion/solvent evaporation. All formulations showed suitable encapsulation efficiency values higher than 80%. PHBV microparticles revealed spherical shape with rough surface and presence of pores. PCL microparticles were spherically shaped with smooth surface. Fourier-transformed infrared spectra demonstrated no chemical bond between resveratrol and polymers. X-ray powder diffraction patterns and differential scanning calorimetry analyses indicated that microencapsulation led to drug amorphization. These PHBV/PCL microparticles delayed the dissolution profile of resveratrol. Release profiles were better fitted to biexponential equation. The hypochlorous-acid-scavenging activity and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation discoloration assay confirmed that the antioxidant activity of PHBV/PCL microparticles was kept, but was dependent on the microparticle morphology and dissolution profile. Resveratrol-loaded PHBV/PCL microparticles showed no cytotoxic effect on red blood cells.

Physicochemical Characterization of a Hydrophilic Model Drug-Loaded PHBV Microparticles Obtained by the Double Emulsion/Solvent Evaporation Technique

Microparticulas de poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBV) contendo um farmaco modelo hidrofilico, o cloridrato de metformina (MH), foram obtidas pela tecnica de emulsao multipla/evaporacao do solvente. Diversas formulacoes foram preparadas, com o objetivo de investigar a influencia de cada composicao sobre a eficiencia de encapsulacao (EE). O resultado mais elevado de EE (9,76%) foi verificado quando da simultânea alcalinizacao e adicao de NaCl na fase aquosa externa da formulacao. O estudo por MEV das microparticulas revelou morfologia esferica e superficie rugosa. As intensidades de difracao cristalina para as microparticulas contendo o MH foram menores do que aquelas observadas para a mistura fisica. Os resultados obtidos por IVTF sugerem que nenhuma ligacao quimica foi formada entre o polimero e o farmaco. A avaliacao por analise termica indica o surgimento de interacoes favoraveis entre MH e PHBV. O estudo de liberacao in vitro demonstrou a influencia do PHBV no perfil de dissolucao do MH. Poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) microparticles containing a watersoluble model drug, metformin hydrochloride (MH), were obtained by a double emulsion/solvent evaporation technique. Several formulations were prepared in order to investigate the influence of each composition on the encapsulation efficiency (EE). The highest value of EE (9.76%) was obtained using simultaneously pH alkalinization and NaCl addition in the external water phase of the formulation. SEM study revealed a spherical morphology and a rough surface. The crystalline diffraction intensities for the MH-loaded microparticles were lower than that verified for the physical mixture. FTIR results suggested that no chemical bond between the polymer and the drug was formed. Also thermal analyses indicated a favorable interaction between MH and PHBV. In vitro drug release demonstrated the influence of the PHBV on the dissolution profile of MH.

HTPB‐based polyurethanes. II. SINs with PMMA

Simultaneous interpenetrating networks from poly(methyl methacrylate-co-ethyleneglycol dimethacrylate) (PA) and a hydroxyl-terminated polybutadiene-based polyurethane (PU) were prepared with various hard-segment contents (X) in the PU and different ratios (PU/PA) between the components. The level of the reinforcement, the mechanism of molecular failure, and the phase inversion depended strongly on X. Dynamic mechanical results indicated that the interpenetration occurred in the rigid blocks of the PU. The improved thermal and mechanical properties observed with higher values of X were interpreted in terms of the molecular weight and polydispersity of the hard blocks in the PU.

Synthetic zinc layered hydroxide salts intercalated with anionic azo dyes as fillers into high-density polyethylene composites: first insights

AbstractUsing a co-precipitation process, we intercalated zinc layered hydroxide salts (zinc LHS) with anionic orange azo dyes (methyl orange—MO or orange II—OII), co-intercalated with chloride anions; for comparison purposes, we also intercalated zinc LHS with chloride anions only, which furnished ZHC. After XRD characterization, we filled high-density polyethylene (HDPE) with the intercalated materials and submitted them to melt compounding and injection molding. We also obtained control batches of HDPE filled with ZHC, the MO sodium salt, or the OII sodium salt. XRD, thermal (simultaneous TGA/DTA), DSC, SEM, and UV-radiation photostability analyses confirmed that homogeneous composites were obtained. HDPE filled with zinc LHS intercalated with MO (a probable more hydrophobic anionic azo dye) displayed improved mechanical properties, good interface bonding, and stability to UV photodegradation; the other fillers afforded materials with poorer mechanical properties. Zinc layered hydroxide salts were intercalated with anionic orange azo dyes and used as fillers into high-density polyethylene (HDPE). Improved mechanical properties and UV photostability were observed for some samples, especially those intercalated with hydrophobic methyl orange.

Estudo do uso de plastificantes de fontes renovável em composições de PVC

Synthetic polymers have been widely used in manufactured products because of their physical and chemical properties and low cost of production. Poly(vinyl chloride), called PVC, is a versatile, inexpensive plastic whose use has become pervasive in modern society. Its applications include window frames, rain gutters, wall paneling, doors, wallpapers, flooring, garden furniture, toys, blood bags and pipes. In all of these applications additives are used, with plasticizers being among the most important. This work shows a comparative study among distinct compositions of flexible PVC - based on two vegetable plasticizers from renewable sources (modified vegetable oil - OVM and epoxidized modified vegetable oil - OVME), in addition to two conventional petrochemical plasticizers, called di(2-ethylhexyl) phthalate-(DEHP) and di(2-ethylhexyl) adipate-(DEHA). No significant differences were observed in the mechanical behavior of the compositions evaluated. The plasticizers affected the hardness and chemical resistance to n-heptane for the compositions. The epoxi group and the high molar mass from vegetable plasticizers showed better compatibility with the PVC resin. The analyses by SEM showed a probable exudation of OVM from the PVC matrix.

An innovative quaternary ammonium methacrylate polymer can provide improved antimicrobial properties for a dental adhesive system.

A quaternary ammonium methacrylate polymer (QAMP) with antimicrobial potential was synthesized. The resulting product (QAMP) was characterized by FTIR spectroscopy, NMR spectroscopy, visible spectrophotometry, XRPD and TGA. The in vitro susceptibility tests against Streptococcus mutans of QAMP were investigated prior and after incorporation into a commercial adhesive system (Clearfil™ SE Bond). The release of quaternary ammonium compounds from the experimental adhesive system (Clearfil™ SE Bond + 5% QAMP) was performed during 1, 7, 14, 21 and 30 days. Spectroscopic data confirmed that QAMP was successfully obtained. Thermogravimetric analysis indicated that QAMP was heat stable. Prior incorporation into the adhesive system, QAMP revealed an inhibition halo of 18.33 ± 0.6 mm. By agar disk diffusion test, Clearfil™ SE Bond containing 5% QAMP presented an inhibition halo (16.67 ± 1.5 mm) similar to Clearfil™ Protect Bond (positive control, 17.00 ± 1.7, p = 0.815) and significantly higher than Clearfil™ SE Bond (negative control, 11.00 ± 1.0, p = 0.006). The minimum inhibitory/bactericidal concentrations for Clearfil™ SE Bond containing 5% QAMP were 20 μL mL−1. The release of quaternary ammonium compounds from the experimental adhesive containing QAMP was very low (5.1%) when compared to Clearfil™ Protect Bond that released 47.2% of its quaternary ammonium monomer (MDPB) after 30 days. The QAMP can offer enhanced antimicrobial properties for self-etching adhesive systems.

PCL/PHBV Microparticles as Innovative Carriers for Oral Controlled Release of Manidipine Dihydrochloride

Microparticles of poly(ε-caprolactone) (PCL) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) containing manidipine dihydrochloride (MAN) were successfully prepared by the simple emulsion/solvent evaporation method. All formulations showed loading efficiency rates greater than 80% and average particle size less than 8 μm. Formulations had spherical shape with smooth and porous surface for PCL and PHBV, respectively. According to Fourier-transform infrared spectroscopy, initial components were not chemically modified during microencapsulation. X-ray diffraction patterns and differential scanning calorimetry demonstrated that this process led to drug amorphization. In vitro dissolution studies showed that all microparticles prolonged MAN release, mainly which one obtained using PCL that contained 5% of drug loaded (PCL-M5). Animal studies demonstrated that formulation PCL-M5 was able to keep the variation of mean arterial pressure after phenylephrine administration up to 24 hours. These data confirmed the sustained antihypertensive effect of the investigated microparticles. Results provided an experimental basis for using formulation PCL-M5 as a feasible carrier for oral controlled release of MAN intended for treating high blood pressure.

Enhanced gastric tolerability and improved anti-obesity effect of capsaicinoids-loaded PCL microparticles.

Capsaicinoids show several pharmacological effects including weight loss. However, their pungency limits the long-term use through the gastrointestinal tract. In that sense, the goal of this study was to prepare capsaicinoids-loaded poly(ε-caprolactone) microparticles as an oral carrier in order to improve their gastric tolerability and to make feasible the long-term treatment of obesity. Formulations containing 3, 5 and 10% capsaicinoids were successfully obtained by simple emulsion/solvent evaporation method. Values of encapsulation efficiency above 90% were achieved. Microparticles showed spherical shape and smooth surface. The particle size was suitable for oral use in order to provide an extended release through the gastrointestinal tract. No chemical bond was observed between drug and polymer. Microencapsulation led to drug amorphization. Formulations prolonged the release of capsaicinoids without changing the release kinetic (biexponential model). Microencapsulation increased the gastric tolerability of capsaicinoids because it prevented inflammatory processes in the stomach of rats. Microparticles containing 5% capsaicinoids demonstrated a statistically significant reduction of Lee index, mesenteric and retroperitoneal fat pads of rats with obesity induced by hypothalamic lesion using monosodium l-glutamate. In summary, capsaicinoids-loaded poly(ε-caprolactone) microparticles are low-irritative oral controlled-release carriers for a long-term use in obesity.

Spray-dried Eudragit® L100 microparticles containing ferulic acid: Formulation, in vitro cytoprotection and in vivo anti-platelet effect

This paper aimed to obtain new spray-dried microparticles containing ferulic acid (FA) prepared by using a methacrylic polymer (Eudragit® L100). Microparticles were intended for oral use in order to provide a controlled release, and improved in vitro and in vivo biological effects. FA-loaded Eudragit® L100 microparticles were obtained by spray-drying. Physicochemical properties, in vitro cell-based effects, and in vivo platelet aggregation were investigated. FA-loaded Eudragit® L100 microparticles were successfully prepared by spray-drying. Formulations showed suitable encapsulation efficiency, i.e. close to 100%. Microparticles were of spherical and almost-spherical shape with a smooth surface and a mean diameter between 2 and 3μm. Fourier-transformed infrared spectra demonstrated no chemical bond between FA and polymer. X-ray diffraction and differential scanning calorimetry analyses indicated that microencapsulation led to drug amorphization. FA-loaded microparticles showed a slower dissolution rate than pure drug. The chosen formulation demonstrated higher in vitro cytoprotection, anti-inflammatory and immunomodulatory potential and also improved in vivo anti-platelet effect. These results support an experimental basis for the use of FA spray-dried microparticles as a feasible oral drug delivery carrier for the controlled release of FA and improved cytoprotective and anti-platelet effects.