Marcos R. Mauricio

Albumin release from a brain-resembling superabsorbent magnetic hydrogel based on starch

Brain-resembling superabsorbent hydrogel composites were developed via UV-induced copolymerization-crosslinking of vinyl-modified starch with acrylic acid (AAc) and N,N-dimethylacrylamide (DMAAm) in the presence of Fe3O4 particles. The iodine test revealed the actual 3D network structure of starch within the swollen hydrogel composite. FTIR spectra of the hydrogel composites indicated interaction between the carboxyl groups from a hydrogel and the iron ions from Fe3O4. The formation of the hydrogel composites also was evidenced by wide-angle X-ray diffraction (WAXD) and energy dispersive X-ray (EDS) spectroscopies. Scanning electron microscopy (SEM) images revealed a homogeneous material since no phase separation between the hydrogel and the Fe3O4 phases could be observed. Minimal fragments of the swollen composite allowed the study of its actual morphology by TEM imaging. Stick-type structures were observed in the composite, as a result of a water-equilibrated structural configuration (obtained in a swollen state) of carboxyl groups of AAc coordinated to iron ions of Fe3O4. The albumin release mechanism of the hydrogel without Fe3O4 is governed by macromolecular relaxation. In the hydrogel composites, the albumin release was driven by macromolecular relaxation, but with a strong tendency to anomalous transport, because of both the tortuosity effect and attenuation of the anion–anion electrostatic repulsion forces. On the other hand, the albumin release became more dependent on anomalous transport with an applied magnetic field, which intensified the tortuosity effect. The proposed hydrogels are more appropriate for use as oral drug delivery systems because they provide a better sustention of the drug over the in vitro release experiment.

Covalent TiO2/pectin microspheres with Fe3O4 nanoparticles for magnetic field-modulated drug delivery

Covalent TiO(2)-co-pectin microspheres containing Fe(3)O(4) nanoparticles were developed through an ultrasound-induced crosslinking/polymerization reaction between the glycidyl methacrylate from vinyl groups in TiO(2) and in pectin. ζ-potentials became less negative in the nanostructured microspheres, caused by the presence of both inorganic particles in the negatively charged pectin. The nanostructured pectin microspheres showed an amoxicillin release rate slower than that of pure pectin microspheres. The proposed microspheres were found to be a sustained release system of amoxicillin in the acid medium. Furthermore, the antibiotic release may be modulated by exposition of the microspheres to a remote magnetic field. In practical terms, the nanostructured microspheres could deliver a larger proportion of their initial load to specific site of action. The cytotoxic concentrations for 50% of VERO cells (CC(50)), calculated as the concentration required to reduce cell viability by 50% after 72h of incubation, for pectin-only microspheres and nanostructured pectin microspheres were 217.7±6.5 and 121.5±4.9μgmL(-1), respectively. The obtained CC(50) values indicated acceptable cytotoxic levels for an incubation period of 72h, showing that the pectin microspheres have a great pharmacological potential for uses in biological environments, even after the introduction of both Fe(3)O(4) and TiO(2).

Synthesis of a thermosensitive surface by construction of a thin layer of poly (N-isopropylacrylamide) on maleimide-immobilized polypropylene.

Thermosensitive surfaces were developed by the grafting of a thin layer of PNIPAAm through an UV-induced photopolymerization reaction of vinyl monomers with a free radical-activated polypropylene (PP) surface. PNIPAAm layer covering the PP surface corrected, to some extension, both depressions and fissures of the previously modified PP surfaces. The layered surfaces have morphological characteristic different from those of the non-layered surfaces, and their thickness was dependent on irradiation time. Water contact angles of the layered surfaces revealed a transition at approximately 33.5-36.5 °C as a result of a response to the variation of temperature. There was an increase in the values of the contact angles with an increase in temperature from 26 °C to 44 °C, revealing the nature both hydrophilic and hydrophobic of the surfaces due to a conformational rearrangement of PNIPAAm exposing its isopropyl groups to the liquid drop. This work offers a chemically stable thermosensitive surface (because it is covalently structured) with great potential for use as sensors and actuators.