One-Step Biosynthesis of Soft Magnetic Bacterial Cellulose Spheres with Localized Nanoparticle Functionalization

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.Authors acknowledge financial support from the Spanish Ministry of Science and Innovation through the RTI2018-096273-B-I00 project, the “Severo Ochoa” Programme for the Centres of Excellence in R&D (CEX2019-000917-S), and the PhD scholarship of S.R.-S (BES-2016-077533). The Generalitat de Catalunya project 2017SGR765 is also acknowledged. The authors also express their gratitude to the technical services of ICMAB-CSIC (electron microscopy, magnetometry and Nanoquim facilities) and CRAG (microscopy facilities). The authors participate in the CSIC Interdisciplinary Platform for Sustainable Plastics toward a Circular Economy, SUSPLAST, the EPNOE Association, Ministerio de Ciencia e Innovación, Acciones de dinamización Redes de Investigación RED2018-102469-T and in the Aerogels COST ACTION (CA 18125).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe