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

Soledad Roig-Sanchez,Pavel A Levkin,Anna Roig,Oriol Torrecilla,Jordi Floriach-Clark,Anna Laromaine,Sebastià Parets

doi:10.1021/acsami.1c17752

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.

Highlights

Bacterial cellulose (BC) is a biopolymeric hydrogel made of intertwined nanocellulose fibrils secreted by bacteria, such as Komagateibacter xylinus, at the air interface of the liquid culture
Soft actuators are attractive tools in medicine; they have to comply with biomedical requirements, such as biocompatibility, flexibility, self-healing, and adaptation to different biological environments.[4−6] Actuators are usually built from a base material, and actuation or movement is conferred by a modification of the structure or by the addition of an auxiliary material to create stimulus-responsive composites.[7−10] Among the current palette of actuators’ base materials, polymers arise as strong candidates
Silica[16] or poly(lactic-coglycolic acid) (PLGA)[17] based actuators are extensively used as cargo-delivery systems, theragnostic, tissue engineering or metal-ion sensing.[16−20] Despite the clear suitability of BC spheres (BCS), they have only been proposed for bioseparation, heavy-metal ion removal and immobilization reactions due to their large surface areas.[21]

Summary

■ INTRODUCTION

Bacterial cellulose (BC) is a biopolymeric hydrogel made of intertwined nanocellulose fibrils secreted by bacteria, such as Komagateibacter xylinus, at the air interface of the liquid culture. Soft actuators are attractive tools in medicine; they have to comply with biomedical requirements, such as biocompatibility, flexibility, self-healing, and adaptation to different biological environments.[4−6] Actuators are usually built from a base material, and actuation or movement is conferred by a modification of the structure or by the addition of an auxiliary material to create stimulus-responsive composites.[7−10] Among the current palette of actuators’ base materials, polymers arise as strong candidates. We have produced size-controlled Janus BC structures in the same biosynthesis single step, the propelling ability of which has been tested under a different stimuli, such as magnetic fields and media acting as fuel

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES