ABSTRACT
Actuated structures are becoming relevant in medical fields; however, they call for flexible/soft-base materials that comply with biological tissues and can be synthesized in simple fabrication steps. In this work, we extend the palette of techniques to afford soft, actuable spherical structures taking advantage of the biosynthesis process of bacterial cellulose. Bacterial cellulose spheres (BCS) with localized magnetic nanoparticles (NPs) have been biosynthesized using two different one-pot processes: in agitation and on hydrophobic surface-supported static culture, achieving core-shell or hollow spheres, respectively. Magnetic actuability is conferred by superparamagnetic iron oxide NPs (SPIONs), and their location within the structure was finely tuned with high precision. The size, structure, flexibility and magnetic response of the spheres have been characterized. In addition, the versatility of the methodology allows us to produce actuated spherical structures adding other NPs (Au and Pt) in specific locations, creating Janus structures. The combination of Pt NPs and SPIONs provides moving composite structures driven both by a magnetic field and a H2O2 oxidation reaction. Janus Pt/SPIONs increased by five times the directionality and movement of these structures in comparison to the controls.
Subject(s)
Acetobacteraceae/chemistry , Cellulose/biosynthesis , Magnetite Nanoparticles/chemistry , Acetobacteraceae/metabolism , Cellulose/chemistry , Hydrogen Peroxide/chemistry , Hydrogen Peroxide/metabolism , Hydrophobic and Hydrophilic Interactions , Magnetic Fields , Oxidation-Reduction , Particle Size , Surface PropertiesABSTRACT
Efficacy and efficiency of pesticide application in the field through the foliage still face many challenges. There exists a mismatch between the hydrophobic character of the leaf and the active molecule, low dispersion of the pesticides on the leaves' surface, runoff loss, and rolling down of the active molecules to the field, decreasing their efficacy and increasing their accumulation to the soil. We produced bacterial cellulose-silver nanoparticles (BC-AgNPs) hybrid patches by in situ thermal reduction under microwave irradiation in a scalable manner and obtaining AgNPs strongly anchored to the BC. Those hybrids increase the interaction of the pesticide (AgNPs) with the foliage and avoids runoff loss and rolling down of the nanoparticles. The positive antibacterial and antifungal properties were assessed in vitro against the bacteria Escherichia coli and two agro-economically relevant pathogens: the bacterium Pseudomonas syringae and the fungus Botrytis cinerea. We showed in vivo inhibition of the infection in Nicotiana benthamiana and tomato leaves, as proven by the suppression of the expression of defense molecular markers and reactive oxygen species production. The hydrogel-like character of the bacterial cellulose matrix increases the adherence to the foliage of the patches.
