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The use of natural diatoms is currently a topic of interest for therapeutic applications due to its facilities, low cost, and biocompatibility. Here, we report the chemical modification of diatoms Aulacoseria genus microalgae-derived biosilica from Guayllabamba - Ecuador decorated with gold nanoparticles by In-situ and Ex-situ methods to study the in vitro gentamicin loading and release properties in simulated body fluid (SBF). Successful decoration of the diatoms and loaded with gentamicin was confirmed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy and Fluorescence Microscopy. We follow the In-vitro drug release by using Ultraviolet-Visible Spectroscopy (UV-vis). Our results revealed that diatoms decorated with gold nanoparticles using the Ex-situ method (Au/CTAB-Diatom) showed a faster release reaching a maximum of 93% in 10 days and a lower loading rate, while the samples decorated by the In-situ method presented longer and slower release behavior. Fluorescence properties were enhanced after the gentamicin loaded. The advantage of this work is the control of the structural and optical properties of diatoms decorated with gold nanoparticles for the gentamicin drug delivery., (Copyright © 2021. Published by Elsevier B.V.)

Cobalt ferrite hollow spheres with chitosan (CoFe 2 O 4 /CS) were synthesized by two different approaches using the solvothermal method. The first approach involves in-situ incorporation of FeCl 3 :6H 2 O and CoNO 3 :6H 2 O in the solvothermal reaction (M1) and in second approach already prepared CoFe 2 O 4 nanoparticles (NPs) using the thermal decomposition method was placed in the solvothermal reaction to form the hollow spheres (M2). Structural identification of the samples were characterized by Fourier transform infrared spectra (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analyses (DSC-TGA) and energy dispersive X-ray spectroscopy (EDX). The magnetic properties were evaluated using a vibrating sample magnetometer (VSM). The presence of chitosan on the hollow sphere was confirmed by FTIR. The XRD analyses proved that the synthesized samples were cobalt ferrite with spinel structure. The structure of the surface and the average particle size of the spheres were observed by SEM and TEM showing the nano scale of the CoFe 2 O 4 component. Structural characterization demonstrating that chitosan does not affect the crystallinity, chemical composition, and magnetic properties of the CoFe 2 O 4 /CS. This work demonstrates that the CoFe 2 O 4 /CS prepared using the as synthesized CoFe 2 O 4 NPs have better structural and magnetic properties., (Copyright © 2017 Elsevier B.V. All rights reserved.)