Polysaccharide-based hydrogels are very promising materials for a wide range of medical applications, ranging from tissue engineering to controlled drug delivery for local therapy. The most interesting property of this class of materials is the ability to be injected without any alteration of their chemical, mechanical and biological properties, by taking advantage of their thixotropic behavior. It is possible to modulate the rheological and chemical-physical properties of polysaccharide hydrogels by varying the cross-linking agents and exploiting their thixotropic behavior. We present here an overview of our synthetic strategies and applications of innovative polysaccharide-based hydrogels: hyaluronan-based hydrogel and new derivatives of carboxymethylcellulose have been used as matrices in the field of tissue engineering; while guar gum-based hydrogel and hybrid magnetic hydrogels, have been used as promising systems for targeted controlled drug release. Moreover, a new class of materials, interpenetrating hydrogels (IPH), have been obtained by mixing various native thixotropic hydrogels.

The chemical, biological and physical properties of carboxymethylcellulose (CMC) hydrogels with silanized magnetite (Fe₃O₄) nanoparticles (NPs) as cross-linker were investigated and compared with the analogous hydrogel obtained by using 1,3-diaminopropane (DAP) as cross-linker. The magnetic hydrogel was characterized from the chemical point of view by FT-IR, whereas the morphology of the hydrogel was investigated by FESEM and STEM. The water uptake and rheological measurements reveal how much the swelling and mechanical properties change when CMC is cross-linked with silanized magnetite NPs instead of with DAP. As far as the biological properties, the hybrid hydrogel neither exerts any adverse effect nor any alteration on the cells. The magnetic hydrogels show magnetic hysteresis at 2.5 K as well as at 300 K. Magnetic measurements show that the saturation magnetization, remanent magnetization and coercive field of the NPs are not influenced significantly by the silanization treatment. The magnetic hydrogel was tested as controlled drug delivery system. The release of DOXO from the hydrogel is significantly enhanced by exposing it to an alternating magnetic field. Under our experimental conditions (2 mT and 40 kHz), no temperature increase of the hydrogel was measured, testifying that the mechanism for the enhancement of drug release under the AMF involves the twisting of the polymeric chains. A static magnetic field (0.5 T) does not influence the drug release from the hydrogel, compared with that without magnetic field.

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels containing carboxymethylcellulose (CMC) and CMC/Fe₃O₄ nanoparticles were prepared. Free-radical polymerization with BIS as cross-linker was used to synthesize the hydrogels. The morphology at the microscopic scale of these materials was investigated using field emission scanning electron microscopy (FESEM). The images show that CMC in the PNIPAM hydrogels induces the formation of a honeycomb structure. This surface morphology was not observed for pure PNIPAM hydrogels prepared under similar conditions. The equilibrium swelling degree of the PNIPAM/CMC hydrogels (5200%) is much larger than that of the pure PNIPAM hydrogels (2500%). The water retention of PNIPAM/CMC hydrogels above the volume phase transition temperature is strongly reduced compared to that of pure PNIPAM hydrogel. Both PNIPAM/Fe₃O₄ and PNIPAM/CMC/Fe₃O₄ hydrogels exhibit a superparamagnetic behavior, but the blocking temperature (104 K) of the former is higher than that of the latter (83 K).

The chemical characterization of gilding decorations in works of art is fundamental in order to elucidate the techniques and materials used by the artists. In the present work we investigated by a combination of bulk and surface sensitive methods the composition and micro stratigraphy of the gilding laminae in the wall painting of the 14th century “La Maestà”, the masterpiece of Simone Martini. The aim of this study was to determine the composition of the gilding leaves and of the adhesive organic materials used to glue the metallic decorations to the wall painting. Due to the altered state of the samples we could not univocally identify the nature of the adhesive materials. Time of flight secondary ion mass spectrometry measurements showed that the gilding layers consisted of a gold leaf which was laid either directly on a preparation layer or on a tin lamina. The high sensitivity of ToF-SIMS and its spatial resolution allowed us to find traces of silver in the gold leaves and in the tin laminae which were not revealed by energy dispersive X-ray analysis.