Reactive Oxygen Species Test Research Articles

Metal-organic frameworks as an active substrate for cell-interaction studies and cell-on-a-chip platforms

Metal-organic frameworks (MOFs) are an emerging class of nanomaterials with immense biomedical potential for their unique interactions with biological and organic materials. In this work, we select two candidate two-dimensional (2D) MOF systems based on Fe3+ and Ni2+ metal centers and 2-aminoterephthalate acid ligand (Fe-MOF and Ni-MOF) and evaluate their performance as an active interface for study of cell-interactions. 2D Fe-MOF and Ni-MOF were synthesized onto hydroxyl-modified gold and glass substrates using a layer-by-layer liquid-phase-epitaxy (LbL-LPE) growth at room temperature and used as active substrates (Fe-MOF/glass, Fe-MOF/Au, Ni-MOF/glass and Ni-MOF/Au, respectively) for MTT cell-proliferation and reactive oxygen species tests using the PC-12 cell-line in order to investigate the biocompatibility. Immunostaining and morphological analyses of PC-12 cells on MOF interfaces suggested a stronger cell-substrate interaction in comparison to glass and were further characterized using the Electrical Cell-substrate Impedance Sensing (ECIS) technique, here for the first time, employed to study cell attachment, spreading and proliferation on 2D Fe-MOF. The 2D Fe-MOF showed superior long-term stability in cell culture medium by recording impedance over 24 h, crucial to monitor cell-dynamics at a solid-liquid interface. A significant increase of interfacial impedance was observed in ECIS, due to PC-12 cells adhering onto 2D Fe-MOF, which was also confirmed by the focused ion beam etching followed by scanning electron microscopy. Our novel findings, therefore, suggest 2D MOFs as highly suitable platform for the study of cell-related interactions using electrical techniques and potentially pave the way for future use of MOFs for bioelectronics and biosensor applications.

Surface-catalyzed electro-Fenton with flexible nanocatalyst for removal of plasticizers from secondary wastewater effluent

Activation of H2O2 with metal-free catalysts is an efficient and environmentally benign alternative to electron-Fenton (EF) for organics degradation. In the present study, flexible nanocatalysts were synthesized with self-regulated metal oxide nanoparticles (FeOx NPs) for efficient removal of plasticizers from secondary wastewater effluent (SWE). Compared with NGr/EF and FeOx@Gr/EF systems, FeOx@NGr/EF could enhance the decay kinetics of plasticizers by 3.9–4.4 times and reduce 48–59% of the disposal cost. Reactive oxygen species tests and trapping experiments proved that the surface-catalyzed EF effectively broadened the range of solution pH. Density functional theory calculations coupled with electrochemical measurements indicated that the electron transfer rates between Fe-O-C atoms were enhanced with N-doping due to strong interactions between N-Fe bond. The synergistic effects of FeOx and N could improve the oxygen reduction activity for H2O2 generation, and accelerate electron transfer between FeOx/NGr and H2O2 for •OH generation, offering an alternative for wastewater treatment.

Metal-organic frameworks with different oxidation states of metal nodes and aminoterephthalic acid ligand for degradation of Rhodamine B under solar light

Metal-organic frameworks (MOFs) have been investigated recently as effective visible light photocatalysts. In this report, we synthesized nickel, iron, and titanium-based MOFs with different oxidation states of metal ions and aminoterephthalic acid ligand for photocatalytic degradation of Rhodamine B (RhB) dye under solar light irradiation. The photoluminescence analysis revealed that the Fe-MOF could suppress the recombination of photoinduced charges and effectively degrade the dye. The photocatalytic experiment demonstrated that the Fe-MOF exhibited higher degradation efficiency of dye (90 %) compared to the Ni-MOF (9 %) and Ti-MOF (50 %) at pH 7 in 90 min. In addition, the effects of catalyst amount, dye concentration, and solution pH on dye degradation were investigated. The photodegradation of dye using Fe-MOF was well-fitted to the first-order kinetics with an R2 value of 0.9987. Furthermore, reactive oxygen species test and electron paramagnetic resonance study revealed that the superoxide anion radicals were mainly responsible for the dye degradation. Cyclic test analysis indicates that there was no substantial decrease in the degradation efficiency of dye after four consecutive cycles.