Title: In situ assembly of bacterial cellulose/graphene oxide spherical hydrogels for their application as nanocarriers

Abstract:

Nowadays, biomedical research and technology is focused on the development of new materials with specific properties. One of the most important aspects in the development of new forms of medication is focused on the design and application of controlled drug dosing systems and localized management systems for the activity of a particular drug. The current trend in such applications is the use of natural polymers such as chitosan, alginate or cellulose. Bacterial cellulose (BC) is a biopolymer synthesized by some bacterial strains which displays unique properties i.e. high crystallinity and purity degree, excellent mechanical performance, porosity and high swelling capacity attributed to the 3D nanofibrillar network structure formed during the biosynthesis process. Due to this last feature, BC can be considered a hydrogel. Depending on the cultivation technique used, BC can be obtained in different morphologies with variable properties. In dynamic cultures spherical particles can be obtained. BC obtained in dynamic cultivation presents a more disordered structure, higher porosity and higher water holding capacity. Moreover, to enhance and extend its applications in biomedicine and pharmacology, BC is normally modified to tailor its properties. One of the most attractive aspects, is that BC has the possibility to be modified through in situ methods, therefore BC-based composites can be obtained in one step procedure by the addition of some additives, polymers or particles to the culture medium so that the additive is incorporated into the BC growing nanofiber network during its biosynthesis. Among the materials that have been used in the in situ biosynthesis process of BC for the development of nanocomposites, graphene family materials can be found. Graphene oxide (GO) is a twodimensional monolayer carbon material which contains large number of hydrophilic oxygenated functional groups and this improves the miscibility of the GO sheets with other polymers included BC. Moreover, the reduced structure, reduced graphene oxide (rGO), exhibits excellent electrical and thermal conductivities and has attracted special attention for the development of conductive and stimuli-responsive systems. In the present work, GO has been incorporated in a BC sphere-like structure in dynamic cultivation by one step method. Different conformations have been obtained, from encapsulation to uniformly distributed hybrid spheres by the variation of the GO concentration during the BC biosynthesis. Hydrogels presented different swelling capacity, and semiconductive behavior, which could open new possibilities for the development of electrostimulated systems. Additionally, in order to evaluate the possible application of these hydrogels as nanocarriers for controlled drug release, the loading and release in simulated intestinal fluid of ibuprofen has been carried out

Biography:

Leire Urbina obtained her Bachelor's Degree in Chemical Engineering at the University of the Basque Country (UPV/EHU). Afterwards, she studied a Master in Renewable Materials Engineering at the Engineering College of Gipuzkoa (UPV/EHU). She was granted with a 4 year pre-doctoral fellowship from the Basque Government and developed her research in the “Materials+Technologies” Research Group. She had the final evaluation of the International Thesis work entitled "Biosynthesis and characterization of polymers from cider by-products. Bacterial cellulose-based nanocomposites" and she was graduated with "Cum Laude". At present, she works as a postdoctoral researcher in UPV/EHU. Her research is based on the polymer area, advanced materials, nanotechnology and biotechnology. She has expertise in the sustainable production of bioplastics and biocellulose using microorganisms and the analysis of the influence of the biosynthetic conditions on the final structures, and their nanocomposites. This work invests in the positioning towards green materials preparation routes opening a wide range of applications.