Marianne Odlyha

Silsesquioxane nanocomposites as tissue implants.

Background: Silicone implants are being used increasingly worldwide, especially in breast augmentation procedures. The most common morbidity observed is capsular contracture, which occurs in 15 percent of cases. To overcome this problem, the authors have developed a novel nanocomposite based on polyhedral oligomeric silsesquioxane-poly(carbonate-urea)urethane (POSS-PCU) for use as tissue implants. Methods: These polymers were implanted in six healthy sheep (n = 6) for 36 months and a siloxane served as the positive control. After explantation, these polymers were extracted, as was the surrounding capsule, if any. Attenuated total reflectance Fourier transform infrared spectroscopy analysis was performed to look for signs of surface degradation on the polymers and histopathologic and electron microscopic examinations were performed to study the interaction between the biomaterial and the host environment in greater detail. Results: After implantation, the authors observed minimal inflammation of the nanocomposite within the sheep model as compared with the siloxane control. Contact angle measurements and fibrinogen enzyme-linked immunosorbent assay tests were then conducted on the POSS-PCU nanocomposite to determine the reason for this behavior. The increased fibrinogen adsorption on POSS-PCU, its amphilicity, and large contact-angle hysteresis indicated that POSS-PCU inhibits inflammation by adsorbing and inactivating fibrinogen on its surface. In complete contrast, the control siloxane in the same setting demonstrated very significant inflammation and degradation, resulting in capsular formation. Naturally, there was no evidence of degradation of the nanocomposite compared with the siloxane control. Conclusions: POSS-PCU nanocomposites have enhanced interfacial biocompatibility and better biological stability as compared with conventional silicone biomaterials, thus making them safer as tissue implants.

Thermo-mechanical analysis of a compliant poly(carbonate-urea)urethane after exposure to hydrolytic, oxidative, peroxidative and biological solutions

AIMS To date, there is still a great need for a fully viable small diameter (< 6 mm) polymeric vascular graft. Currently in such low flow locations, non-elastic expanded polytetrafluoroethylene (ePTFE) is the best available but it is quite inferior to autologous saphenous vein since it fails due to intimal hyperplasia caused by compliance mismatch between the graft and elastic host artery. Recently, a novel compliant poly(carbonate-urea)urethane vascular graft whose trade name is MyoLink has been developed. In this article, we report the findings of a thermo-mechanical analysis of the polymers chemistry postexposure to in vitro solutions comprised of hydrolytic, oxidative, peroxidative and biological media. METHODS AND MATERIALS The following degradative solutions were used in vitro: plasma fractions I-IV; phospholipase A2 (PLA); cholesterol esterase (CE) and solutions of H2O2/CoCl2, t-butyl peroxide/CoCl2 (t-but/CoCl2) and glutathione/t-butyl peroxide/ CoCl2 (glut/t-but/CoCl2). The MyoLink graft was compared against a conventional poly(ether)urethane (Pulse-Tec). All the graft specimens were 100 mm in length (5.0 mm ID) and were incubated in the latter solutions at 37 degrees C for 70 days in total. The following thermo-mechanical methods were used to analyse both graft types: thermo-mechanical analysis (TMA) and dynamic mechanical thermal analysis (DMTA). RESULTS Incubation of Pulse-Tec in plasma fractions I-IV, PLA and CE reveals only one observable modification: an increase in the size of the low temperature, melting phase. But incubation in H2O2/CoCl2, and t-but/CoCl2 leads to an increase in the polymeric phase separation coupled with an enlargement in the size of the low temperature melting crystalline phase in Pulse-Tec. The glut/t-but/CoCl2 solution leads to a phase separation between the hard and soft segment domains, coupled with an increase of the internal order within the hard segment domains in Pulse-Tec. The only system in which MyoLink degraded was glut/t-but/CoCl2. In this system, an increase of the phase separation coupled with a simultaneous increase of the crystal size of the low-temperature melting crystalline phase occurred. CONCLUSION This study shows dramatic changes in the chemistry of the soft and hard segments occurred in the case of the conventional poly(ether)urethane Pulse-Tec graft material. Such changes were not manifested in the majority of solutions in the case of MyoLink but a hydrolytic-led degradation of the carbonate soft segment was evidenced only in the glut/t-but/CoCl2 system.

Measurement of shrinkage behaviour in leather and parchment by dynamic mechanical thermal analysis

The mechanical behaviour of modern and historic parchment and leather samples through their shrinkage temperature is described. The measurements are made possible by the novel modification of a standard dynamic mechanical thermal analyser (Rheometric Scientific DMTA Mk3) to enable experiments to be conducted on samples immersed in water. A sample of parchment was clamped in tensile mode under a small static applied force. The temperature of the water could be controlled and thus it was possible to heat the sample and monitor the change in its displacement as it passed through the shrinkage temperature. Information could therefore be obtained on the percentage shrinkage and the temperature range over which it occurred. Furthermore, the method also provided useful information on the expansion or contraction of the samples on initial immersion in water, which relates to ease of sample wettability, and on the changes during drying process and rehydration.

Dosimetry of paintings : determination of the degree of chemical change in museum exposed test paintings (lead white tempera) by thermal analysis and infrared spectroscopy

Thermoanalytical (DSC and TGA) data on the basic lead carbonate pigment alone have been previously published [J. Chem. Soc., Dalton Trans. (1996) 3639]. This paper draws attention to the modifying effect of basic lead carbonate on the thermal stability of the paint medium, and on the degradation of the paint medium under controlled light ageing conditions. The various light dosages received by the samples were found to produce differences in the shape of the leading edge of the DSC curves. Quantification of the data shows that there is a systematic trend, i.e. the difference in the leading edge of the DSC curve, with respect to the control sample, increases with the duration of light exposure of the samples. In the natural ageing of the samples exposed in various galleries for a period of 9 months, the dominant change is a shift in the overall peak. Changes in artificially and naturally aged samples were also identified by Fourier transform infrared spectroscopy. The broadening of the carbonyl peak due to the formation of lipid oxidation products could be quantified to determine the degree of chemical change.

Dosimetry of paintings: determination of the degree of chemical change in museum exposed test paintings (azurite tempera) by thermal and spectroscopic analysis

Abstract This paper describes the effects of accelerated artificial and natural ageing on samples of azurite paint tempera prepared according to traditional early Italian recipes. The pigment used was basic copper carbonate in the form known as azurite and this was mixed using whole egg tempera medium. Artificial and natural ageing of the dosimeters was performed using controlled ageing chambers and selected sites of varying environmental conditions. The effects of ageing were quantified using a number of analytical techniques, which include the following: thermal analysis (DSC and TGA), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The data were then compared with those obtained from samples which were naturally aged by exposure in selected European art galleries and historic castles for a period of 9 months. It was found that the changes observed on artificial light ageing alone were minimal. Mass spectrometry (DTMS) showed that samples had already undergone oxidation during the curing stage of 3 months [O.F. van den Brink, G.B. Eijkel, J.J. Boon, Thermochim. Acta 360 (2) (2000), this proceedings]. There were, however, measurable differences in the samples that had been subjected to thermal and pollutant ageing, and this was used to rank the sites.

Dosimetry of paintings: determination of the degree of chemical change in museum exposed test paintings (smalt tempera) by thermal analysis

Abstract One of the main concerns of conservators and curators is to find a method for evaluating the damage incurred by works of art in major galleries, historic houses, and castles with differing indoor environmental conditions. For this purpose, test tempera paintings were prepared and exposed at selected sites. The test paintings act as dosimeters and integrate the contributions from a range of factors which determine the overall environmental hazard to which paintings are exposed. Subsequent analysis of the test paintings involved an interdisciplinary approach using mass spectrometry (FOM Institute, the Netherlands), thermal analysis (Birkbeck College, UK) and non-invasive spectroscopic analysis (CNR–IROE, Italy). These techniques gave a measure of the physicochemical change and hence the resulting damage. In this paper, the thermoanalytical data will be presented, in particular of smalt tempera. Prior accelerated ageing of similar test paintings using controlled conditions was also performed to provide a comparison between artificial and natural ageing and a means for calibrating the test paintings.

Review paper: principles and applications of surface analytical techniques at the vascular interface.

Surface properties have been found to be one of the key parameters which cause degradation and of thrombogenicity in all polymers used in biomedical devices, thus signifying the importance and the necessity for quantitative and accurate characterization of the polymer surface itself as used in the construction of the device. The characterization techniques employed generally involve thermal and spectroscopic measurements, in which class the electrochemical investigations and scanning probe microscopies can also be included. Current hypotheses on the correlations that exist between surface parameters and hemocompatibility and degradation of polymers are examined herein, but concentrating on the field of clinically utilized polymeric materials as used within medical devices themselves. Furthermore, this review provides a brief but complete synopsis of these techniques and other emerging ones, which have proven useful in the analysis of the surface properties of polymeric materials as used in the construction of cardiovascular devices. Statements and examples are given as to how specific information can be acquired from these differing methodologies and how it aids in the design and development of new polymers for usage in biomedical device construction.

Characterisation of Leather Samples by Non-invasive Dielectric and Thermomechanical Techniques

A description is given how the dielectric coaxial technique measuring in the microwave region has been used for monitoring drying processes in leather samples. It is also shown how the coupling of this technique together with dynamic mechanical analysis enables the simultaneous recording of changes inthe dielectric properties, related to the moisture content of the material, together with the mechanical properties as a function of time or temperature. The samples studied include unaged and artificially aged goat and calf leathers. Measurements using the dynamic mechanical analyser are presented over a range of temperature which includes the shrinkage temperature. During the drying process, values of mechanical modulus or displacement and dielectric permittivity are recorded as a function of time or temperature which includes the temperature range of leather shrinkage, and from previous research report of Larsen [1] this has been associated with the chemical state of the leather samples.

Thermal analyses of selected soil samples from the tombs at the Tianma-Qucun site, Shanxi, China

Abstract This paper describes a study of selected soil samples from three of the tombs at the Tianma-Qucun site, Shanxi province, China, using thermogravimetry and differential scanning calorimetry. The results of the analyses indicate that these soil samples are calcite-rich and contain a few percent of organic matter. The soil from the location of one of the tombs was found to have less calcite than the soil from the other two tombs. There was, however, only a small difference in organic matter in the soils from the different tombs. Results for soil samples taken from regions in the proximity of archaeological objects, however, demonstrated that the microenvironment as characterised by the soils for objects in various locations of the one tomb varied. Some evidence for the presence of charcoal and collagen based material was found.

Microclimate monitoring of indoor environments using piezoelectric quartz crystal humidity sensors

The aim of this paper is to describe indoor microclimate monitoring at two different locations, Sandham Memorial Chapel, in Hampshire, England, and the castle El Alcázar, in Segovia, Spain. Piezoelectric quartz crystal sensors with novel humidity sensitive poly(ethyleneimine) coatings and Pt resistance thermometers were used to measure the relative humidity (RH) and temperature gradients across one of the paintings of the British artist, Stanley Spencer, housed in Sandham Memorial Chapel. The measurement period extended from December 1997 to September 1998. Each coated crystal was set in its own housing from which temperature and RH measuring circuits were connected via a cable to the computer. The 9 month monitoring period incorporated the range in seasons from winter through to autumn. Between December and February the RH at the back of the painting was found to be lower than that at the front. In March and April the reverse was true. Additionally, there were large spikes in the data in some of the months for both RH and temperature, probably caused by direct sunlight falling on the sensors. At the second site monitoring was performed for a shorter period, from December 1997 to early January 1998. It served, however, to show that abrupt changes can occur in the microclimate surrounding the painting. These fluctuations can with time lead to alterations to the paint surface and result eventually in cracking and damage to the art work.