Antibacterial effects ofin situzinc oxide nanoparticles generated inside the poly (acrylamide-co-hydroxyethylmethacrylate) nanocomposite.

The present work reports the antibacterial activity againstPseudomonasaeruginosaof a nanocomposite made of zinc oxide nanoparticles dispersed in a poly(acrylamide-co-hydroxyethylmethacrylate) matrix (PAAm-Hema-ZnONPs). Thein situsynthesis of ZnONPs inside of the PAAm-Hema crosslinked network is described. Moreover, the physicochemical properties of the PAAm-Hema-ZnONPs nanocomposite are analyzed. The results confirm that the PAAm-Hema hydrogel provides an excellent scaffold to generate ZnONPs. The presence of ZnONPs inside the hydrogel was confirmed by UV-visible (band at 320 nm), by Infrared spectroscopy (peak at 470 cm-1), SEM, and TEM images. The presence of NPs in PAAm-Hema diminish the swelling percentage by 70%, and the Young modulus by 33.7%, compared with pristine hydrogel. The 75% of ZnONPs are released from the nanocomposite after 48 h of spontaneous diffusion, allowing the use of the nanocomposite as an antibacterial agent.In vitro, the agar diffusion test presents an inhibition halo againstP. aeruginosabacteria 50% higher than the unloaded hydrogel. Also, the PAAm-Hema-ZnONPs live/dead test shows 54% of dead cells more than the hydrogel. These results suggest that the easy, one-step way generated composites can be used in biomedical applications as antimicrobial agents.

Synergistic effect of polyaniline coverage and surface microstructure on the inhibition of Pseudomonas aeruginosa biofilm formation.

Biofilm Formation is a survival strategy for microorganisms to adapt to their environment. Microbial cells in biofilm become tolerant and resistant to antibiotics and immune responses, increasing the difficulties for the clinical treatment of microbial infections. The surface chemistry and the micro/nano-topography of solid interfaces play a major role in mediating microorganism activity and adhesion. The effect of the surface chemical composition and topography on the adhesion and viability of Pseudomonas aeruginosa was studied. Polymeric (polyethylene terephthalate) surfaces were covered with a conducting polymer (polyaniline, PANI) film by in-situ polymerization and microstructured by Direct Laser Interference Patterning (DLIP). The viability of Pseudomonas aeruginosa on the different surfaces was investigated. The physicochemical properties of the surfaces were characterized by water contact angle measurements, scanning electron microscopy and atomic force microscopy. Bacterial biofilms were imaged by atomic force and scanning electron microscopies. The bacterial viability decreased on PANI compared with the substrate (polyethylene terephthalate) and it decreased even more upon micro-structuring the PANI films. In addition, the biofilm reduction could be improved using polymers with different chemical composition and/or the same polymer with different topographies. Both methods presented diminish the bacterial attachment and biofilm formation. These findings present a high impact related to materials for biomedical engineer applications regarding medical devices, as prostheses or catheters.

pH-responsive hydrogels to protect IgY from gastric conditions: in vitro evaluation.

Oral administration of specific egg yolk immunoglobulin (IgY) is effective against a number of gastrointestinal pathogens. However, the activity of orally administered IgY is reduced rapidly, since IgY is sensitive to pepsin and low pH. In this study, hydrogels containing acrylamide and acrylic acid were synthesized and used to encapsulate IgY. The capacity of these structures to load, protect and release IgY and the interaction between IgY and hydrogels by FTIR spectroscopy were studied. The particle size and swelling percentage of hydrogels were highly dependent on the pH of the buffer solution. As expected, pH-sensitive hydrogels had a high IgY loading percentage (99.2 ± 12.9 mg IgY/mg hydrogel) at pH 7.4. It means that each gel piece incorporated approximately 8.4 ± 1.1 mg IgY. The results showed that the hydrogels could efficiently incorporate IgY and retain it inside the polymer network at pH <2.2. However, IgY was slowly released at basic pH and a high percentage remained inside. The IR spectra show that IgY interacts with the hydrogel in its network with extended hydrogen bonds. The present study demonstrates that hydrogels particles can efficiently incorporate the IgY but cannot show a controlled and sustained release of IgY in simulated intestinal fluid probably due to hydrophobic interactions with the polymer network. The stability of IgY in simulated gastric fluid was greatly improved by encapsulation in hydrogels. This approach provides information about a novelty method for delivery of IgY for the prevention and control of enteric diseases.

A direct and quantitative image of the internal nanostructure of nonordered porous monolithic carbon using FIB nanotomography.

A direct study of the shape, size and connectivity of nonordered pores in carbon materials is particularly challenging. A new method that allows direct three-dimensional (3D) investigations of mesopores in monolithic carbon materials and quantitative characterization of their physical properties (surface area and pore size distribution) is reported. Focused ion beam (FIB) nanotomography technique is performed by combination of focused ion beam and scanning electron microscope. Porous monolithic carbon is produced by carbonization of a resorcinol-formaldehyde gel in the presence of a cationic polyelectrolyte as a pore stabilizer.

Design of a new electrogenerated polyquinone film substituted with glutathione. Towards direct electrochemical biosensors.

We developed a method to graft a tripeptide (glutathione) onto 5-hydroxy-1,4-naphthoquinone, an electropolymerizable molecule. The resulting thin conducting polymer presents a well-defined and stable electroactivity in neutral buffered solution, due to the embedded quinone group, and is able to covalently graft amino-modified DNA probe strands. It is shown that the bioelectrode presents positive current change following DNA hybridization. This makes a "signal-on" direct electrochemical DNA sensor. The results were obtained with low target concentration (50nM) and the selectivity is excellent as a single-mismatch sequence can be discriminated from the full-complementary target.