Ana Isabel F. Ribeiro

Synthesis and antimicrobial activity of novel 5-aminoimidazole-4-carboxamidrazones.

A mild and simple method was developed to prepare a series of fifteen 5-aminoimidazole 4-carboxamidrazones, starting from the easily accessible 5-amino-4-cyanoformimidoyl imidazoles. The antimicrobial activity of these novel amidrazones was screened against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and Candida sp. (Candida albicans, Candida krusei, Candida parapsilosis). Only a subset of compounds displayed fair-moderate activity against S. aureus and E. coli but all exhibited activity against Candida sp. The three most potent antifungal compounds were further tested against Cryptococcus neoformans, Aspergillus fumigatus and three dermatophytes (Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum gypseum). These three hit compounds strongly inhibited C. krusei and C. neoformans growth, although their activity on filamentous fungi was very weak when compared to the activity on yeasts.

Dyed Poly(styrene-methyl Methacrylate-acrylic Acid) Photonic Nanocrystals for Enhanced Structural Color

In the present work, we investigated the combined effect of poly(styrene-methyl methacrylate-acrylic acid) [P(St-MMA-AA)] PCs with the disperse dye C.I. Disperse Red 343 on the photonic crystals (PCs) shape, distribution, organization, iridescence, chemical structure, thermal stability, and reflectance. PCs were successfully produced in the form of highly spherical, monodisperse colloidal structures. Presence of dye in the PCs inner core-shell structure was confirmed via Fourier-transformed infrared spectroscopy. The PCs brightness and iridescent effect was enhanced by the presence of the dyestuff, which also promoted the self-assembly of the colloidal nanospheres in the form of arrays. The P(St-MMA-AA) PCs thermal stability did not alter with the introduction of the dye. In a side experiment, dyed PCs were also coated onto dyed polyamide fabrics. Data reported successful coating of the textile fabric and an improvement of its reflectance. Fabric immobilization fostered the self-assembling of the dyed colloidal nanospheres in the form of well-organized face-centered cubic, closed-packed arrays. This is the simplest and most energy favorable organization for PCs. The combination of disperse dyes with PCs is a very recent and challenging idea and could open new ways to understand the influence the PCs photonic-band structure may exert on the photoluminescence properties of the dyes embedded in the PCs inner space, and vice versa.

Double dielectric barrier (DBD) plasma-assisted deposition of chemical stabilized nanoparticles on polyamide 6,6 and polyester fabrics

The development of new multifunctional textiles containing nanoparticles (NPs) has a special interest in several applications for pharmaceutical and medical products. Cu, Zn and Ag are the most promising antimicrobial NPs, exhibiting strong antibacterial activities. However, most of antimicrobial textiles coated with NPs are not able to perform a controlled release of NPs because of the high degree of aggregation. The aim of this study is to assess the effect of NPs stabilizers such as citrate, alginate and polyvinyl alcohol (PVA) in Cu, Zn and Ag NPs dispersions. The obtained dispersions were used to develop a new class of antibacterial NPs coatings onto polyamide 6,6 (PA66) and polyester fabrics (PES) by Double Dielectric Barrier (DBD) plasma discharge. Dynamic light scattering (DLS) was used to evaluate the best dispersing agent in terms of size, polydispersity index and zeta potential. Coating efficiency was evaluated by SEM, XPS and FTIR. The washing fastness of the coatings developed was also tested. The results show that the best dispersions were obtained using 2.5% of citrate for ZnO, 5% Alginate for Cu and 2.5% alginate for Ag NPs. SEM, XPS and FTIR analysis shows that DBD is an efficient deposition technique only for Ag and Cu NPs and that better perform in PA66 than PES fabric. The DBD deposition in air display similar results in term of NPS deposition of usually more efficient plasma jets using carrier gas such as N2 and Ar.