Department of Pharmacy, University of Copenhagen, DK-2100 Copenhagen, Denmark.
ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, OX11 0QX Harwell, Oxfordshire, UK.
Nanoscale. 2022 Sep 2;14(34):12297-12312. doi: 10.1039/d2nr01958b.
In the present study, we investigate the combined interaction of mesoporous silica (SiO) and photocatalytic titanium dioxide (TiO) nanoparticles with lipid membranes, using neutron reflectometry (NR), cryo-transmission electron microscopy (cryo-TEM), fluorescence oxidation assays, dynamic light scattering (DLS), and ζ-potential measurements. Based on DLS, TiO nanoparticles were found to display strongly improved colloidal stability at physiological pH of skin (pH 5.4) after incorporation into either smooth or spiky ("virus-like") mesoporous silica nanoparticles at low pH, the latter demonstrated by cryo-TEM. At the same time, such matrix-bound TiO nanoparticles retain their ability to destabilize anionic bacteria-mimicking lipid membranes under UV-illumination. Quenching experiments indicated both hydroxyl and superoxide radicals to contribute to this, while NR showed that free TiO nanoparticles and TiO loaded into mesoporous silica nanoparticles induced comparable effects on supported lipid membranes, including membrane thinning, lipid removal, and formation of a partially disordered outer membrane leaflet. By comparing effects for smooth and virus-like mesoporous nanoparticles as matrices for TiO nanoparticles, the interplay between photocatalytic and direct membrane binding effects were elucidated. Taken together, the study outlines how photocatalytic nanoparticles can be readily incorporated into mesoporous silica nanoparticles for increased colloidal stability and yet retain most of their capacity for photocatalytic destabilization of lipid membranes, and with maintained mechanisms for oxidative membrane destabilization. As such, the study provides new mechanistic information to the widely employed, but poorly understood, practice of loading photocatalytic nanomaterials onto/into matrix materials for increased performance.
在本研究中，我们使用中子反射法（NR）、低温透射电子显微镜（cryo-TEM）、荧光氧化测定、动态光散射（DLS）和 ζ-电位测量研究了介孔硅（SiO）和光催化二氧化钛（TiO）纳米粒子与脂质膜的联合相互作用。基于 DLS，发现 TiO 纳米粒子在低 pH 值下掺入光滑或多刺（“病毒样”）介孔硅纳米粒子后，在生理 pH 值（皮肤 pH 5.4）下显示出强烈改善的胶体稳定性，后者通过 cryo-TEM 证明。与此同时，这种基质结合的 TiO 纳米粒子在紫外照射下仍能破坏模拟阴离子细菌的脂质膜。猝灭实验表明羟基和超氧自由基都有助于这一点，而 NR 表明游离 TiO 纳米粒子和负载到介孔硅纳米粒子中的 TiO 纳米粒子对支撑脂质膜产生类似的影响，包括膜变薄、脂质去除和部分无序外层膜叶的形成。通过比较光滑和病毒样介孔纳米粒子作为 TiO 纳米粒子基质的效果，阐明了光催化和直接膜结合效应之间的相互作用。总的来说，该研究概述了如何将光催化纳米粒子容易地掺入介孔硅纳米粒子中以提高胶体稳定性，同时保留其对脂质膜光催化破坏的大部分能力，并保持氧化膜破坏的机制。因此，该研究为广泛使用但理解不佳的将光催化纳米材料加载到/进入基质材料以提高性能的做法提供了新的机制信息。
