Encapsulation of Local Anesthetic Bupivacaine in Biodegradable Poly(DL-lactide-co-glycolide) Nanospheres: Factorial Design, Characterization and Cytotoxicity Studies

Local anesthetic agents cause temporary blockade of nerve impulses productiong insensitivity to painful stimuli in the area supplied by that nerve. Bupivacaine (BVC) is an amide-type local anesthetic widely used in surgery and obstetrics for sustained peripheral and central nerve blockade. in this study, we prepared and characterized nanosphere formulations containing BVC. To achieve these goals, BVC loaded poly(DL-lactide-co-glycolide) (PLGA) nanospheres (NS) were prepared by nanopreciptation and characterized with regard to size distribution, drug loading and cytotoxicity assays. The 2(3-1) factorial experimental design was used to study the influence of three different independent variables on nanoparticle drug loading. BVC was assayed by HPLC, the particle size and zeta potential were determined by dynamic light scattering. BVC was determined using a combined ultrafiltration-centrifugation technique. The results of optimized formulations showed a narrow size distribution with a polydispersivity of 0.05%, an average diameter of 236.7 +/- 2.6 nm and the zeta potential -2.93 +/- 1,10 mV. In toxicity studies with fibroblast 3T3 cells, BVC loaded-PLGA-NS increased cell viability, in comparison with the effect produced by free BVC. In this way, BVC-loaded PLGA-NS decreased BVC toxicity. The development of BVC formulations in carriers such as nanospheres could offer the possibility of controlling drug delivery in biological systems, prolonging the anesthetic effect and reducing toxicity.

The Use of Mucoadhesive Polymers to Enhance the Hypotensive Effect of a Melatonin Analogue, 5-MCA-NAT, in Rabbit Eyes

Purpose.: 5-Methoxy-carbonylamino-N-acetyltryptamine (5-MCA-NAT, a melatonin receptor agonist) produces a clear intraocular pressure (IOP) reduction in New Zealand White rabbits and glaucomatous monkeys. The goal of this study was to evaluate whether the hypotensive effect of 5-MCA-NAT was enhanced by the presence of cellulose derivatives, some of them with bioadhesive properties, as well as to determine whether these formulations were well tolerated by the ocular surface. Methods.: Formulations were prepared with propylene glycol (0.275%), carboxymethyl cellulose (CMC, 0.5% and 1.0%) of low and medium viscosity and hydroxypropylmethyl cellulose (0.3%). Quantification of 5-MCA-NAT (100 μM) was assessed by HPLC. In vitro tolerance was evaluated by the MTT method in human corneal-limbal epithelial cells and normal human conjunctival cells. In vivo tolerance was analyzed by biomicroscopy and specular microscopy in rabbit eyes. The ocular hypotensive effect was evaluated measuring IOP for 8 hours in rabbit eyes. Results.: All the formulations demonstrated good in vitro and in vivo tolerance. 5-MCA-NAT in CMC medium viscosity 0.5% was the most effective at reducing IOP (maximum IOP reduction, 30.27%), and its effect lasted approximately 7 hours. Conclusions.: The hypotensive effect of 5-MCA-NAT was increased by using bioadhesive polymers in formulations that are suitable for the ocular surface and also protective of the eye in long-term therapies. The use of 5-MCA-NAT combined with bioadhesive polymers is a good strategy in the treatment of ocular hypertension and glaucoma.

Synthesis and characterization of biodegradable thermoplastic elastomers for medical applications: Novel copolyesters as an alternative to polylactide and poly (e-caprolactone)

421 p.

Tratamentos de fibras de carnaúba [copernicia prunífera (miller) h. e. moore] para o desenvolvimento de compósito biodegradável com matriz de polihidroxibutirato

The use of raw materials from renewable sources for production of materials has been the subject of several studies and researches, because of its potential to substitute petrochemical-based materials. The addition of natural fibers to polymers represents an alternative in the partial or total replacement of glass fibers in composites. In this work, carnauba leaf fibers were used in the production of biodegradable composites with polyhydroxybutyrate (PHB) matrix. To improve the interfacial properties fiber / matrix were studied four chemical treatments to the fibers..The effect of the different chemical treatments on the morphological, physical, chemical and mechanical properties of the fibers and composites were investigated by scanning electron microscopy (SEM), infrared spectroscopy, X-ray diffraction, tensile and flexural tests, dynamic mechanical analysis (DMA), thermogravimetry (TGA) and diferential scanning calorimetry (DSC). The results of tensile tests indicated an increase in tensile strength of the composites after the chemical treatment of the fibers, with best results for the hydrogen peroxide treated fibers, even though the tensile strength of fibers was slightly reduced. This suggests a better interaction fiber/matrix which was also observed by SEM fractographs. The glass transition temperature (Tg) was reduced for all composites compared to the pure polymer which can be attributed to the absorption of solvents, moisture and other low molecular weight molecules by the fibers

Determination of deep and shallow levels in conjugated polymers by electrical methods

Conjugated organic semiconductors have been submitted to various electrical measurement techniques in order to reveal information about shallow levels and deep traps in the forbidden gap. The materials consisted of poly[2-methoxy, 5 ethyl (2' hexyloxy) paraphenylenevinylene] (MEH-PPV), poly(3-methylthiophene) (PMeT), and alpha-sexithienyl (alpha T6) and the employed techniques were IV, CV, admittance spectroscopy, TSC, capacitance and current transients. (C) 1999 Elsevier Science B.V. All rights reserved.

Schottky barriers to semiconducting polymers

Schottky barrier diodes are made from virtually all semiconducting polymers. Application of Schottky barriers on the development of electronic devices built from semiconducting polymers prompted this research. The article investigated the dc and ac admittance of Schottky barrier which occur at the interface between aluminum and poly(3-methyl thiophene) made ready by electropolymerisation. The experiment revealed that the interfacial layers occurring in polymer Schottky barriers is significant in the response of the controlling device.

Electrical study of impurity states in conjugated polymers

Schottky diodes resulting from an intimate contact of aluminum on electro-deposited poly(3-methylthiopene), PMeT, have been studied by admittance spectroscopy, capacitance-voltage and current-voltage measurements, and optically-induced current transients. The loss-tangents show the existence of interface states that can be removed by vacuum annealing, also visible in the transients. Furthermore, the CV curves don't substantiate the idea of movement of the dopant ions.

Electrical characterization of semiconducting polymers

Schottky diodes resulting from an intimate contact of aluminum on electrodeposited poly(3-methylthiopene) were studied by admittance spectroscopy, capacitance-voltage measurements and voltaic and optically-induced current and capacitance transients. The loss tangents show the existence of interface states that can be removed by vacuum annealing. Furthermore, the C-V curves contradict the idea of movement of the dopant ions.

Schottky barrier diodes from semiconducting polymers

Schottky barrier diodes based on Al/poly(3-methylthiophene)/Au have been fabricated and their electrical behaviour investigated. I-V characteristics revealed a dependence on the fabrication conditions, specifically on the time under vacuum prior to evaporation of the rectifying contact and post-metal annealing at elevated temperature. The available evidence is consistent with the formation of a thin insulating layer between the metal and the polymer following these procedures. Long periods under vacuum prior to deposition of the aluminium electrode reduced the likelihood of such a layer forming. Capacitance-voltage plots of the devices were stable to voltage cycling, so long as the forward voltage did not exceed similar to 1 V. Above this a small degree of hysteresis was observed, which is attributed to the filling/emptying of interface states or traps in the polymer.

Raman Spectroscopy and DFT calculations for the Electronic Structure Characterization of Conjugated Polymers

In the last three decades, there has been a broad academic and industrial interest in conjugated polymers as semiconducting materials for organic electronics. Their applications in polymer light-emitting diodes (PLEDs), polymer solar cells (PSCs), and organic field-effect transistors (OFETs) offer opportunities for the resolution of energy issues as well as the development of display and information technologies1. Conjugated polymers provide several advantages including low cost, light weight, good flexibility, as well as solubility which make them readily processed and easily printed, removing the conventional photolithography for patterning2. A large library of polymer semiconductors have been synthesized and investigated with different building blocks, such as acenes or thiophene and derivatives, which have been employed to design new materials according to individual demands for specific applications. To design ideal conjugated polymers for specific applications, some general principles should be taken into account, including (i) side chains (ii) molecular weights, (iii) band gap and HOMO and LUMO energy levels, and (iv) suited morphology.3-6 The aim of this study is to elucidate the impact that substitution exerts on the molecular and electronic structure of π-conjugated polymers with outstanding performances in organic electronic devices. Different configurations of the π-conjugated backbones are analyzed: (i) donor-acceptor configuration, (ii) 1D lineal or 2D branched conjugated backbones, and (iii) encapsulated polymers (see Figure 1). Our combined vibrational spectroscopy and DFT study shows that small changes in the substitution pattern and in the molecular configuration have a strong impact on the electronic characteristics of these polymers. We hope this study can advance useful structure-property relationships of conjugated polymers and guide the design of new materials for organic electronic applications.

Characterization of a biodegradable starch based film. Application on the preservation of fresh spinach

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia - UL

Determination of deep and shallow levels in conjugated polymers by electrical methods

Conjugated organic semiconductors have been submitted to various electrical measurement techniques in order to reveal information about shallow levels and deep traps in the forbidden gap. The materials consisted of poly[2-methoxy, 5 ethyl (2' hexyloxy) paraphenylenevinylene] (MEH-PPV), poly(3-methylthiophene) (PMeT), and alpha-sexithienyl (alpha T6) and the employed techniques were IV, CV, admittance spectroscopy, TSC, capacitance and current transients. (C) 1999 Elsevier Science B.V. All rights reserved.

Schottky barriers to semiconducting polymers

Schottky barrier diodes are made from virtually all semiconducting polymers. Application of Schottky barriers on the development of electronic devices built from semiconducting polymers prompted this research. The article investigated the dc and ac admittance of Schottky barrier which occur at the interface between aluminum and poly(3-methyl thiophene) made ready by electropolymerisation. The experiment revealed that the interfacial layers occurring in polymer Schottky barriers is significant in the response of the controlling device.

Electrical study of impurity states in conjugated polymers

Schottky diodes resulting from an intimate contact of aluminum on electro-deposited poly(3-methylthiopene), PMeT, have been studied by admittance spectroscopy, capacitance-voltage and current-voltage measurements, and optically-induced current transients. The loss-tangents show the existence of interface states that can be removed by vacuum annealing, also visible in the transients. Furthermore, the CV curves don't substantiate the idea of movement of the dopant ions.

Electrical characterization of semiconducting polymers

Schottky diodes resulting from an intimate contact of aluminum on electrodeposited poly(3-methylthiopene) were studied by admittance spectroscopy, capacitance-voltage measurements and voltaic and optically-induced current and capacitance transients. The loss tangents show the existence of interface states that can be removed by vacuum annealing. Furthermore, the C-V curves contradict the idea of movement of the dopant ions.