Self-Propelling Microbubblers for Active Cleaning of Biofilm in Confined Spaces

第1部分：被称为“生物膜”的非技术性SUMMARYDense微生物膜经常污染医疗工具、家庭用品和基础设施，如内窥镜、浴室瓷砖和供水管道，并可能导致危险的感染。这些生物膜是细菌细胞的粘性集合体，周围环绕着附着在它们接触到的任何东西上的支架。大约80%的医疗感染来自入侵患者体内临床设备和植入物内部工作的生物膜。在这样一个难以触及的地区清洗生物膜是极其困难的，因为传统的消毒剂和抗生素无法穿透生物膜坚硬的支架。我们怎么能让抗菌试剂越过这样的生物膜屏障呢？这项拟议中的研究试图开发一种小颗粒，可以通过产生氧泡来穿透并摧毁坚硬的支架。这种名为“自行式微泡器”的颗粒将通过在硅藻--藻类的微小骨架--上装载一种产氧化学物质来制备。因此，这一系统将改善对生活在其中的细菌细胞的抗菌素致命打击的输送。在调整微泡发生器的氧泡生成率和随后的推进速度时，这项拟议的研究将检查微泡发生器能够穿透附着在复杂拓扑结构的材料上的生物膜，破坏生物膜的支架，杀死支架保护的细菌细胞，并最终防止生物膜的形成。同时，对于广泛的影响，独特的微泡器将被用作新一代生物科学家和生物工程师的教育和培训工具。总体而言，该项目将有助于改善人们的健康、安全和生活质量，抵御传染病和污染。第2部分：由微生物细胞菌落和周围的胞外聚合物(EPS)组成的生物膜是医学感染和材料变质的主要原因，威胁人类健康和可持续发展。到目前为止，已经开发了各种消毒剂，但这些系统都不能有效地去除在有限空间中形成的生物膜。为此，这项拟议的研究旨在组装和分析一种可以入侵难以到达的地区生长的生物膜并随后清除细菌菌落和EPS的“自行式微泡器”。本研究假设硅藻颗粒中掺杂氧化锌(ZnO)或二氧化锰(MnO2)分解过氧化氢(H_2O_2)的催化剂会喷出氧泡，进而在防腐的3%H_2O_2溶液中充当自行式微泡剂。入侵后，微泡发生器将继续产生氧气泡，这些氧泡融合在一起，产生一波机械能，能够摧毁生物膜。通过对H_2O_2分解活化能、H_2O_2分解速率和动能的分析，研究了微泡发生器的自航性能。同时，将通过监测颗粒对生物膜的入侵以及随后由大肠杆菌和铜绿假单胞菌形成的生物膜的硬度、粘附力和化学成分的变化来检查微泡除菌器去除微槽基质中生物膜的程度。最后，将通过监测细胞内氧化应激的增加、活细胞的减少和生物被膜的复发来评估微泡杀菌器对生物被膜细菌的杀灭效果。这项研究的成功完成将阐明化学机械能转换所获得的独特的清洁机理，并改变目前主要依赖化学品的消毒策略。同时，该项目将产生广泛的影响，将建议的研究模块纳入为不同教育水平的学生开发的几个教育项目，并将研究成果传播到广泛的社区。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYDense microbial films called “biofilm” often foul medical tools, household items, and infrastructures such as an endoscopes, bathroom tiles, and water supply pipes, and can lead to dangerous infections. These biofilms are slimy aggregates of bacterial cells surrounded by scaffolds adhering to anything they touch. About 80 percent of all medical infections originate from biofilms that invade the inner workings of clinical devices and implants inside patients. Cleaning of biofilms in such a hard-to-reach area is extremely difficult because traditional disinfectants and antibiotics cannot penetrate a biofilm's tough scaffolds. How can we let antibacterial reagents cross over such a barrier of biofilms? This proposed study attempts to develop a small particle that can penetrate and destroy tough scaffolds by generating oxygen bubbles. The particle named “self-propelling microbubbler” would be prepared by loading an oxygen-generating chemical on diatoms – the tiny skeletons of algae. As a consequence, this system would improve the delivery of antibacterial deathblow to the bacterial cells living inside. While tuning the oxygen bubble generation rate and subsequent propulsion speed of the micrububblers, this proposed study will examine extents that the microbubblers can penetrate biofilm clinging to a material with complex topology, damages the scaffold of biofilms, kill bacterial cells protected by the scaffolds, and, ultimately, prevent the return of biofilm formation. In parallel, for broad impacts, the unique microbubblers will be used as education and training tools for a new generation of bioscientists and bioengineers. Overall, this project will serve to improve people’s health, safety, and life quality against infectious diseases and fouling.PART 2: TECHNICAL SUMMARY Biofilms composed of microbial cell colonies and surrounding extracellular polymer substances (EPS) are major causes of medical infection and material deterioration, thus threatening both human health and sustainability. A variety of disinfectants were developed to date, but none of these systems are active in removing biofilms forming in confined spaces. To this end, this proposed study aims to assemble and analyze a “self-propelling microbubbler” that can invade biofilms grown in the hard-to-reach area and, subsequently, clean out both bacterial colonies and EPS. This study hypothesizes that diatom particles doped with zinc oxide (ZnO) or manganese dioxide (MnO2) catalysts decomposing hydrogen peroxide (H2O2) eject oxygen bubbles and, in turn, act as the self-propelling microbubbler in the antiseptic 3% H2O2 solution. After the invasion, the microbubblers would continue to generate oxygen bubbles that fuse to produce a wave of mechanical energy capable of destroying the biofilms. The self-propulsion of microbubblers will be studied by analyzing the activation energy for H2O2 decomposition, the H2O2 decomposition rate, and the kinetic energy. In parallel, the extent that the microbubblers remove biofilm in the micro-grooved substrate will be examined by monitoring invasion of particles into the biofilm and subsequent changes in stiffness, adhesion force, and chemical composition of the biofilms formed by Escherichia coli and Pseudomonas aeruginosa. Finally, the efficacy of microbubblers to killing biofilm bacteria will be evaluated by monitoring the increase of intracellular oxidative stress, the reduction of viable cells, and the recurrence of biofilm. The successful completion of this study will elucidate the unique cleaning mechanism attained by chemical-to-mechanical energy conversion and transform current disinfection strategies that rely on chemicals mostly. In parallel, this project will make broad impacts by incorporating the proposed research modules into several educational programs developed for students at various educational levels and also disseminating the research outcomes to a broad spectrum of communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.