Valentina Giovanna Brunella

Char formation in polyvinyl polymers I. Polyvinyl acetate

The study of thermal and thermal-oxidative degradation of polyvinyl acetate is reported. Solid residues of degradation were analysed by FTIR microscopy in the reflection-transmission mode. Aromatization and carbonisation of the solid residues are discussed.

Comparison of polypropylene and polyethylene terephthalate (Dacron) meshes for abdominal wall hernia repair: A chemical and morphological study

For the first time, by scanning electron microscopy (SEM), polypropylene (PP) excised meshes (ethylene oxide sterilized) for abdominal wall hernia repair have been shown to be greatly damaged physically, independently of the implantation time, while the polyethylene terephthalate (PET), or Dacron, ones (gamma radiation sterilized), did not undergo alterations due to the sterilization process and were not damaged, even after long implantation periods. Fourier-Transform Infrared Spectroscopy (FTIR) study of PP and PET excised meshes, as well as of their extracts with cyclohexane, has shown the presence of species, such as squalene, palmitic and stearic acid, in some cases, cholesterol, transferred from the surrounding tissues to the polymer during the implantation period. In the case of PP meshes, these small organic molecules would reduce physical and mechanical properties of the material. A hypothesis is presented to account for the better behavior (not in the clinical sense) of PET meshes.

γ irradiation of poly(vinyl chloride) for medical applications

Abstract In this work we have studied the effect of γ radiation on poly (vinyl chloride). Radicals produced by irradiation were investigated by EPR measurements at room temperature and the formation of conjugated double bonds was probed by UV–VIS absorbance measurements; samples were also submitted to infrared measurements to be analysed in terms of oxidation products.

Thermoresponsive mesoporous silica nanoparticles as a carrier for skin delivery of quercetin.

Recently, mesoporous silica nanoparticles (MSNs) have emerged as promising drug delivery systems able to preserve the integrity of the carried substance and/or to selectively reach a target site; however, they have rarely been explored for skin application. In this study, thermoresponsive MSNs, designed to work at physiologic cutaneous temperature, are proposed as innovative topical carriers for quercetin (Q), a well-known antioxidant. The thermosensitive nanoparticles were prepared by functionalizing two different types of matrices, with pore size of 3.5nm (MSNsmall) and 5.0nm (MSNbig), carrying out a free radical copolymerization of N-isopropylacrylamide (NIPAM) and 3-(methacryloxypropyl)trimethoxysilane (MPS) inside the mesopores. The obtained copolymer-grafted MSNs (copoly-MSNs) were physico-chemically characterized and their biocompatibility was attested on a human keratinocyte cell line (HaCaT). The release profiles were assessed and the functional activity of Q, free or loaded, was evaluated in terms of antiradical and metal chelating activities. Ex vivo accumulation and permeation through porcine skin were also investigated. The characterization confirmed the copolymer functionalization of the MSNs. In addition, both the bare and functionalized silica matrices were found to be biocompatible. Among the copolymer-grafted complexes, Q/copoly-MSNbig exhibited more evident thermoresponsive behavior proving the potential of these thermosensitive systems for advanced dermal delivery.

Effects of microtomy on the material properties of ultra high molecular weight polyethylene

In order to study the properties of retrieved orthopaedic prosthetic implants, microtomy is often used to produce pieces suitable for examination. However, the cut made with the microtome can change the characteristics of the material to be studied and thus give an incorrect picture of some of its actual properties. This paper is based on a thorough investigation of the effects of different cutting depth, cutting velocity and cutting angle on the orientation and crystallinity of ultra high molecular weight polyethylene. It was found that the orientation decreases with greater cutting depth and cutting velocity and increases slightly with a greater cutting angle. The degree of crystallinity as measured by FTIR and calculated from the first DSC heating was found to increase with greater cutting depth. The crystallinity calculated from the second heating, however, always gave an average value of 50.5±0.5%. Cutting angle and cutting velocity did not influence the crystallinity. Two different knives were used in the investigation. One was old and left scratch marks on the film while the other had recently been sharpened. The main difference between the two knives, apart from the scratch marks, was that the films cut with the old knife had a lower degree of crystallinity than the ones cut with the new knife when measured immediately after cutting. The crystallinity did, however, increase during ageing in ambient atmosphere, and after about 2 months it was the same as for the samples cut with the new knife.

Molecularly imprinted cyclodextrin nanosponges for the controlled delivery of L-DOPA: perspectives for the treatment of Parkinson's disease.

ABSTRACT Background: L-DOPA is an amino acid precursor to the neurotransmitter dopamine that is extensively used as a prodrug for the treatment of Parkinson’s disease. However, L-DOPA is an unstable compound: when exposed to light or added to aqueous solutions, it may degrade, compromising its therapeutic properties. Methods: In this work, a new type of drug-loaded cyclodextrin-based nanosponge, obtained using molecular imprinting, is described for the prolonged and controlled release of L-DOPA. The molecularly imprinted nanosponges (MIP-NSs) were synthesized by cross-linking β-cyclodextrin with 1,1ʹ-carbonyldiimidazole in DMF in the presence of L-DOPA as a template molecule. TGA, DSC and FTIR analyses were performed to characterize the interactions between L-DOPA and the two nanosponge structures. Quantitative NMR spectroscopy was used to determine the amount and the affinity of L-DOPA entrapped in the nanosponges. The in vitro L-DOPA release kinetics from the NSs were quantitatively determined by HPLC analysis. Results: The MIP-NSs show a slower and more prolonged release profile than the non-imprinted nanosponges. No degradation of the L-DOPA hosted in the MIP-NSs was observed after long-term storage at room temperature. Conclusions: The MIP-NSs are a promising alternative for the storage and controlled delivery of L-DOPA.

Electron beam radiation effects on UHMWPE: an EPR study

Electron paramagnetic resonance (EPR) technique has been employed to detect and characterise a series of different radical species generated in ultra‐high molecular weight polyethylene (UHMWPE) via electron beam irradiation. Three different radical species have been found and assigned on the basis of their EPR spectra and of the related computer simulations. A secondary alkyl species, the prevalent one, is present immediately after irradiation, an allyl species appears only 24 h after irradiation when the alkyl species disappears.The third species, clearly visible at high microwave power only, has been observed for the first time and assigned to a tertiary alkyl carbon radical, whose formation is strictly connected with a Y‐shape crosslink and a migration of the unpaired electron on a carbon atom localised in an adjacent position. Copyright

Effect of Multimodal Pore Channels on Cargo Release from Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles (MSNs) with multimodal pore channels were fully characterized by TEM, nitrogen adsorption-desorption, and DLS analyses. MSNs with average diameter of 200 nm with dual pore channel zones with pore diameters of 1.3ź2.6 and 4 nm were tested for their use in drug delivery application. Important role of the multimodal pore systems present on MSNs on the quantitative release of model drug ibuprofen was investigated. The results obtained revealed that the release profile for ibuprofen clearly shows distinct zones which can be attributed to the respective porous channel zones present on the particles. The fluctuations in the concentration of ibuprofen during the prolonged release from MSNs were caused by the multimodal pore channel systems.

Poly(NIPAM-co-MPS)-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system

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HYSCORE and Davies ENDOR study of irradiated ultra high molecular weight polyethylene

Ultra high molecular weight polyethylene (UHMWPE) has been studied with different magnetic resonance techniques to elicit information on the nature and the location of radicals generated during high energy irradiation. Field swept electron paramagnetic resonance, pulsed Davies electron nuclear double resonance and hyperfine sublevel correlation spectroscopic measurements allowed extracting for the first time the full 1H hyperfine coupling tensors of the most abundant radical, i.e. a secondary alkyl radical and to ascertain the formation of allyl radicals in the first stages of the irradiation process. The 1H hyperfine coupling tensors are analogous to those reported for single crystal irradiated polyethylene, suggesting that radicals generated in UHMWPE are located in the crystalline region of the polymer. Copyright