The purpose of this work was to prepare stable citrus (CF) and apple (AF) pectin aerogels for potential pharmaceutical applications. Different shapes of low ester pectin aerogels were prepared by two fundamental methods of ionic cross-linking. Pectins% spherical and multi-membrane gels were first formed by the diffusion method using 0.2 M CaCl2 solution as an ionic cross-linker. The highest specific surface area (593 m2/g) that had so far been reported for pectin aerogels was achieved using this method. Monolithic pectin gels were formed by the internal setting method. Pectin gels were further converted into aerogels by supercritical drying using CO2. As surface area/volume is one of the key parameters in controlling drug release, multi-membrane pectin aerogels were further used as drug delivery carriers. Theophylline and nicotinic acid were used as model drugs for the dissolution study. CF aerogels showed more controlled release behaviour than AF pectin aerogels. Moreover a higher release rate (100%) was observed with CF aerogels.
The solubility and diffusivity of CO2 in polyethylene glycols (PEGs) of different molecular weight measured by two different methods are discussed in the present work. Before solubility measurements, the melting temperatures of PEG with different molecular weights were determined by means of differential scanning calorimetry. For the purpose of the present study a temperature of 343 K was chosen as the working temperature for both employed methods since all studied polymers are in liquid state at this temperature. All samples were analyzed at isothermal conditions and in the pressure range from 0 MPa up to 30.0 MPa. A set of absorption experiments on the PEG/CO2 systems was performed using an external balance method. In order to validate results obtained by the new method they were compared to the data obtained at the same process conditions by a method using magnetic suspension balance (MSB).
Aerogels are outstanding materials, obtained by the sol-gel process. The production of polysaccharide aerogels is however time-consuming and their use for life-science applications is limited. To accelerate the production time, ethanol was used to induce the gelation of pectin, alginate, xanthan and guar gum. Polysaccharide aerogels were produced by dissolution in water, gelation in ethanol and supercritical drying. Only ethanol was used for the gelation without the use of any other cross-linking agent. In addition there was no solvent-exchange step prior to supercritical drying since the gelation occurred directly in ethanol. Differential scanning calorimetry was used to analyze the decompositions of the samples and also to measure their thermal conductivities. SEM and rheological analyses were performed in order to characterize the new materials.
In this study, we developed a novel high methoxyl pectin – xanthan aerogel coating on medical-grade stainless steel, prepared by ethanol-induced gelation and subsequent supercritical drying. Two non-steroidal anti-inflammatory drugs, i.e. diclofenac sodium and indomethacin, were incorporated into the aerogel coating. Electrochemical analyses were performed on the coated samples using electrochemical impedance spectroscopy and cyclic polarisation techniques. The results showed that all passivated samples were highly resistant to general corrosion. The release of both non-steroidal anti-inflammatory drugs was complete after 24 h, as confirmed by the plateau in the drug release profiles as well as by IR spectroscopy after the final release point. The potential of samples for use in orthopedic applications was evaluated on a human bone-derived osteoblast cell and all samples were shown to be biocompatible. The increased viability of some samples indicates the high potential of the developed approach for future evaluation of possible clinical use.
In the present study, we evaluated the degradation behavior of poly(d,l-lactide-co-glycolide) (PLGA) before and after foaming with supercritical CO2. Initial polymer samples, shaped as tablets, and foamed samples were immersed in a Sörensen buffer solution and maintained for 10 weeks at a constant temperature of 37 °C under mild stirring (50 rpm). The pH of the degradation environment was monitored, and the mass and structure modifications suffered by the samples at various stages of the study were determined. A comparison was performed between the in vitro behaviors of the PLGA samples before and after supercritical fluid processing. It was observed that the PLGA foams degrade slower than the PLGA tablets. These data are essential for evaluating the suitability of various processing methods in the design of biodegradable medical devices or implants with well-defined requirements regarding their stability and mechanical properties during specific applications.