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Calcium alginate beads were investigated for their biosorption performance in the removal of gold and silver from aqueous solutions. It was found that uptake capacities were significantly affected by the solution pH, with optimum pH values of 2 and 4 for gold and silver, respectively. Kinetic and isotherm experiments were carried out at the optimum pH. The maximum uptake capacities were 290 mg/g for Au and 52 mg/g for Ag. FTIR analysis indicated that both carboxylic and hydroxylic functional groups in alginate beads are involved in the metal binding and later reduction of gold (+3) and silver (+1) to gold (0) and silver (0). SEM and X-ray diffraction confirmed the formation of gold and silver nanoparticles.

Please cite this article as: R. Cavalli, M. Argenziano, E. Vigna, P. Giustetto, E. Torres, S. Aime, E. Terreno, Preparation and in vitro characterization of chitosan nanobubbles as theranostic agents, Colloids and Surfaces B: Biointerfaces (2015), http://dx.doi.org/10. 1016/j.colsurfb.2015.03.023 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 of 27 A c c e p t e d M a n u s c r i p A c c e p t e d M a n u s c r i p t 2 ABSTRACT Theranostic delivery systems are nanostructures that combine the modality of therapy and diagnostic imaging. Polymeric micro-and nanobubbles, spherical vesicles containing a gas core, have been proposed as new theranostic carriers for MRI-guided therapy. In this study, chitosan nanobubbles were purposely tuned for the co-delivery of prednisolone phosphate and a Gd (III) complex, as therapeutic and MRI diagnostic agent, respectively. Perfluoropentane was used for filling up the internal core of the formulation. These theranostic nanobubbles showed diameters of about 500 nm and a positive surface charge that allows the interaction with the negatively charged Gd-DOTP complex. Pluronic F68 was added to the nanobubble aqueous suspension as stabilizer agent. The encapsulation efficiency was good for both the active compounds, and a prolonged drug release profile was observed in vitro. The effect of ultrasound stimulation on prednisolone phosphate release was evaluated at 37 °C. A marked increase on drug release kinetics with no burst effect was obtained after the exposure of the system to ultrasound. Furthermore, the relaxivity of the MRI probe changed upon incorporation in the nanobubble shell, thereby offering interesting opportunity in dual MRI-US experiments. The ultrasound characterization showed a good in vitro echogenicity of the theranostic nanobubbles.In summary, chitosan drug-loaded nanobubbles with Gd (III) complex bound to their shell might be considered a new platform for imaging and drug delivery with the potential of improving anticancer treatments.

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