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This investigation concerns the design of poly(3-hydroxybutyrate) (PHB)-based nanofibrous hybrid materials containing zinc oxide nanoparticles (nano-ZnO) by means of two electro-hydrodynamic techniques, i.e., electrospinning of polymer/nano-ZnO solutions and the combination of electrospinning of polymer solutions with electrospraying of nano-ZnO dispersions. The analysis of the physical properties associated with precursory solutions was performed in order to understand the final morphology of the corresponding nanofibers. The obtained PHB/nano-ZnO mats showed uniform fiber morphology with an average porosity ca. 85 % with enhanced thermal stability compared to that of pristine PHB. Differential scanning calorimetry was also used to determine the influence of ZnO nanoparticles in the phase transitions of as-spun PHB nanofibers. Furthermore, the antibacterial performance against E. coli and S. aureus proved to be dependent on the elaboration technique, thus permitting the design of novel bacteriostatic or bactericidal PHB/nano-ZnO nanofibrous composites.

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Escherichia coli is one the most common bacteria responsible of uropathogenic diseases, which motives the search for rapid and easy methods of detection. By taking advantage of the specific interactions between mannose and type 1 fimbriae, in this work two fluorescent phenyleneethynylene (PE) trimers bearing one or two 4-aminophenyl-α-D-mannopyranoside termini groups were synthesized for the detection of E. coli. Three bacterial strains: ORN 178 (fimbriae I expression), ORN 208 (mutant serotype with no fimbriae expression) and one obtained from a local hospital (SS3) were used. Laser Scanning Confocal Microscopy (LSCM) and Surface Plasmon Resonance (SPR) were applied for the interaction studies following two different approaches: (1) mixing the oligomer solutions with the bacterial suspension, which permitted the observation of stained bacteria and by (2) biosensing as thin films, where bacteria adhered on the surface-functionalized substrate. LSCM allows one to easily visualize that two mannose groups are necessary to have a specific interaction with the fimbriae 1. The sensitivity of SPR assays to E. coli was 104 colony forming unit (CFU)/mL at 50 µL/min flow rate. The combination of PE units with two mannose groups results in a novel molecule that can be used as a specific fluorescent marker as well as a transducer for the detection of E. coli.

Novel composites have been prepared via the incorporation of zinc oxide nanoparticles (nZnO) into poly(acrylic acid-co-itaconic acid) (poly(AA-co-IA)) hydrogel. The prepared composites were characterized by means of Fourier transform infrared spectroscopy (FT-IR), swelling studies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The amount of nZnO incorporated into hydrogel was determined by using atomic absorbance spectrometry. In addition, the antibacterial performance of composites was evaluated against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). SEM characterization of the composite hydrogels revealed a homogeneous distribution of the nZnO throughout the hydrogel with formation of some agglomerates. A progressive rise in thermal stability of poly(AA-co-IA) is found with increasing nZnO concentration. nZnO/poly(AA-co-IA) composites showed antibacterial activity against both bacteria. The approach used in this work is an efficient method to develop new hydrogel-based wound dressing composites for use in biomedical applications. POLYM. COMPOS.,

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