Methods: The scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) was used to qualitatively detect the cellular accumulation of ZnO NPs in algal cells, while inductively coupled plasma optical emission spectrometry (ICP OES) was performed to quantify the cell associated-zinc in algal cells. The percentage of cell death, reduction in algal biomass, and loss in photosynthetic pigments were measured to investigate the cytotoxic effects of ZnO NPs on H. pluvialis. Extracellular and intracellular changes in algal cells resulted from the treatment of ZnO NPs were demonstrated through optical, scanning, and transmission electron microscopic studies.
Results: SEM-EDX spectrum evidenced the accumulation of ZnO NPs in algal biomass and ICP OES results reported a significant (p < 0.05) dose- and time-dependent accumulation of zinc in algal cells from 24 h for all the tested concentrations of ZnO NPs (10-200 μg/mL). Further, the study showed a significant (p < 0.05) dose- and time-dependent growth inhibition of H. pluvialis from 72 h at 10-200 μg/mL of ZnO NPs. The morphological examinations revealed substantial surface and intracellular damages in algal cells due to the treatment of ZnO NPs.
Discussion: The present study reported the significant cellular accumulation of ZnO NPs in algal cells and the corresponding cytotoxic effects of ZnO NPs on H. pluvialis through the considerable reduction in algal cell viability, biomass, and photosynthetic pigments together with surface and intracellular damages.
METHODS: CMC/PLA/ZnO/CUR nanocomposite films were prepared by the dispersion of CMC and ZnO NPs in solubilized PLA/curcumin medium, followed by solvent casting step. Curcumin is poorly water-soluble and used as the model drug in this study. The films with different contents of CMC, PLA and ZnO NPs were characterized using FTIR, impedance spectroscopy, tensile testing and FESEM imaging. The in vitro drug release of the films was carried out in deionized water under DC electric field of 4.5 V.
RESULTS: The ionic conductivity of the films increased with increasing the CMC concentration of the film. The addition of a small amount of ZnO NPs (2%) successfully restored the tensile properties of the film. In response to the application of the electric field, the composite films released drug with a near-linear profile. There was no noticeable amount of passive diffusion of the drug from the film with the absence of the electric field.
CONCLUSION: The outcome of this study enabled the design of an electric-responsive nanocomposite platform for the delivery of poorly water-soluble/non-ionic drugs. Graphical abstract.