Highly Efficient Enzyme-Functionalized Porous Zirconia Microtubes for Bacteria Filtration

Abstract

In contrast to polymer membranes, ceramic membranes offer considerable advantages for safe drinking water provision due to their excellent chemical, thermal, and mechanical endurance. In this study, porous ceramic microtubes made of yttria stabilized zirconia (YSZ) are presented, which are conditioned for bacteria filtration by immobilizing lysozyme as an antibacterial enzyme. In accordance with determined membrane pore sizes of the nonfunctionalized microtube of ≤200 nm, log reduction values (LRV) of nearly 3 (i.e., bacterial retention of 99.9%) were obtained for bacterial retention studies using gram-positive model bacterium Micrococcus luteus. Immobilization studies of lysozyme on the membrane surface reveal an up to six times higher lysozyme loading for the covalent immobilization route as compared to unspecific immobilization. Antibacterial activity of lysozyme-functionalized microtubes was assessed by qualitative agar plate test using Micrococcus luteus as substrate showing that both the unspecific and the covalent lysozyme immobilization enhance the microtubes' antibacterial properties. Quantification of the enzyme activity at flow conditions by photometric assays reveals that the enzyme activities of lysozyme-functionalized microtubes depend strongly on applied flow rates. Intracapillary feeding of bacteria solution and higher flow rates lead to reduced enzyme activities. In consideration of different applied flow rates in the range of 0.2-0.5 mL/min, the total lysozyme activity increases by a factor of 2 for the covalent immobilization route as compared to the unspecific binding. Lysozyme leaching experiments at flow conditions for 1 h show a significant higher amount of washed-out lysozyme (factor 1.7-3.4) for the unspecific immobilization route when compared to the covalent route where the initial level of antibacterial effectiveness could be achieved by reimmobilization with lysozyme. The presented platform is highly promising for sustainable bacteria filtration.

Production of ceramic membranes with different pore sizes for virus retention

“…Afterwards, these green capillaries were sintered for 2 h at 1050 • C with preceding dwell times at 280 • C and 500 • C to remove the dispersant (APTES) and binder (PVA) molecules, respectively (Nabertherm, Germany). According to our previous studies based on YSZ, a moderate sintering temperature of 1050 • C for 2 h was chosen to obtain capillary membranes showing both, relatively high open porosities in combination with a sufficient mechanical stability [15,35]. After sintering, the capillaries were ready for characterisation.…”

Effective activation of halloysite nanotubes by piranha solution for amine modification via silane coupling chemistry

“…36 The hydroxylated surfaces have relatively higher activity for silanization. [37][38][39] We anticipate that piranha solution would be a promising candidate for activating HNTs. To the best of our knowledge, the effectiveness of piranha solution in activating HNTs and subsequent silanization has not yet been reported.…”

Poly(N-isopropylacrylamide)-gated Fe3O4/SiO2 core shell nanoparticles with expanded mesoporous structures for the temperature triggered release of lysozyme

“…3.9 nm which plays a crucial role in targeting Gram positive bacteria as a first line of defense in the human body. 43,44 Due to this, lysozyme is found abundantly in the nasal and ocular membranes and its deficiency often results in conjunctivitis or other increased incidences in illness. 45 The applicability of the temperature controlled delivery of lysozyme from CS-MSNs is tested by observing its antibacterial properties on Gram positive Bacillus cereus and Micrococcus luteus bacteria.…”