Collaborative Research: Elucidating the Mechanisms for Inhibition of Biofouling on Polymeric Membranes Modified with Polyelectrolyte Multilayers and Antimicrobial Nanoparticles

超滤膜（UF）因其在去除水中病原体和颗粒物方面的有效性，在饮用水处理和废水回用中得到越来越多的应用。然而，由于进水中微生物的普遍存在，超滤过程经常受到生物污染的阻碍，这减少了清洁水的生产，缩短了膜的寿命，增加了能源需求。目前，阻止生物污染的努力主要集中在使用消毒剂，这可能会破坏膜并导致消毒副产物的形成。为了克服这些限制，本研究的目的是研究使用聚电解质多层膜（PEMs）将抗菌纳米颗粒（NPs）固定在聚砜UF膜表面，以增强其对生物污染的抵抗力。与传统的纳米复合膜制造方法相比，使用PEMs具有优势，因为(1)PEMs可以增加膜表面电荷和/或亲水性，从而减少细菌附着；(2) PEMs确保NPs位于膜表面，这将增强细菌的失活；(3) PEMs的应用是非破坏性的，当膜被污染或NPs溶解时，PEMs - np组件可以在原位再生。该实验旨在验证经PEMs改性的膜对生物污垢的抗性是由其抗粘附和抗菌性能控制的假设。PEM参数（例如，组成聚电解质和NPs以及PEM内的双层数量）将被系统地改变，以研究它们对膜的抗粘附和抗菌性能的影响。探测细胞膜？S抗粘接性能，过滤过程中细菌在膜上沉积的动力学，以及细菌与膜表面之间的粘附力，将被测量。膜的抗菌性能将通过枚举膜表面的细菌菌落和使用荧光染料技术检测膜受损的沉积细胞来研究。在细菌悬浮液的长期过滤实验中，通过监测渗透通量的下降来评估经PEMs改性的膜的抗生物污染能力。本研究的另一个组成部分将是调查上述PEM参数对非预期NP浸出率的影响。最后，本研究将研究几种物理和化学方法在膜表面原位再生PEM-NP组件，并评估再生膜的性能。这项研究是新颖的，因为它是第一个探索使用PEMs制造抗生物污染的纳米复合膜。由于将np整合到pem中是一个新兴领域，本研究将更好地理解PEM-NP组件的形成和鲁棒性。通过系统地改变组件的聚电解质和NPs组成，本研究将确定控制膜的关键参数。抗粘接和抗菌性能。我们将通过用PGA-g-PEG（一种极亲水的聚阴离子）层取代选定的PEM-NP组件中的顶层，来研究终止层在控制膜抗粘附性能方面的作用。本研究将进一步揭示表面固定化NPs的细胞毒性机制，并探讨抗菌壳聚糖作为多阳离子组分对膜抗菌活性的增强作用。这项研究将为下一代水净化膜过滤系统的发展创造令人兴奋的机会，并有可能改变这些过程的操作和维护方式。此外，这项研究将为纳米复合膜的安全生产提供重要的信息。这项工作将有助于理解生物膜预防的材料设计，这也与材料、化学和生物医学工程领域有关。在这项研究中，他们将让本科生参与研究工作的各个阶段。研究成果将通过在同行评议的期刊上发表的出版物、学生在国家科学会议上的报告和组织专题讨论会来传播。在巴尔的摩市中心的一所以非洲裔美国人为主的小学，PI参与组织五年级学生的科学活动，将进一步扩大其广泛的影响。此外，环境技术的讲座将在一个女孩？我在华盛顿读高中。该项目的成果也将被整合到乔治华盛顿大学的一门新的环境纳米技术课程中。

PIs: Kai Loon Chen / Baoxia MiProposal Numbers: 1133559 / 1134233Ultrafiltration (UF) membranes are increasingly being used in drinking water treatment and wastewater reuse because of their effectiveness in removing waterborne pathogens and particulate matter. Due to the ubiquity of microorganisms in influent waters, however, UF processes are often hindered by biofouling which reduces clean water production, shortens membrane life, and increases energy demands. Currently, efforts to retard biofouling have centered on using disinfectants, which can damage the membranes and result in the formation of disinfection byproducts. To overcome these limitations, the objective of this research is to investigate the use of polyelectrolyte multilayers (PEMs) to immobilize antimicrobial nanoparticles (NPs) onto the surfaces of polysulfone UF membranes to enhance their resistance to biofouling. Compared to conventional nanocomposite membrane fabrication methods, the use of PEMs would be advantageous because (1) PEMs can increase membrane surface charge and/or hydrophilicity and, thus, reduce bacterial attachment; (2) PEMs ensure that NPs are located on the membrane surface, which will enhance bacterial inactivation; and (3) the application of PEMs is non-destructive and the PEM-NP assembly can be regenerated in situ when the membrane is fouled or the NPs have dissolved. The experiments are designed to test the hypothesis that the resistance of membranes modified by PEMs towards biofouling is controlled by its anti-adhesive and antimicrobial properties. PEM parameters (e.g., constituent polyelectrolytes and NPs and number of bilayers within PEMs) will be systematically varied in order to investigate their influence on the anti-adhesive and antimicrobial properties of the membranes. To probe the membrane?s anti-adhesive properties, the kinetics of bacterial deposition on the membrane during filtration, as well as the adhesive forces between a bacterium and the membrane surface, will be measured. The antimicrobial properties of the membranes will be studied through the enumeration of bacterial colonies on the membrane surface and by using a fluorescent dye technique to detect deposited cells with damaged membranes. The biofouling resistance of membranes modified by PEMs will be evaluated by monitoring the permeate flux decline in long-term filtration experiments with bacteria suspensions. Another component of this research will be to investigate the effects of the above-mentioned PEM parameters on the rate of unintended NP leaching. Finally, this research will examine several physical and chemical methods for the in situ regeneration of PEM-NP assemblies on membrane surfaces and evaluate the performance of the regenerated membranes. This study is novel because it is one of the first to explore the use of PEMs to fabricate biofouling-resistant nanocomposite membranes. Since the incorporation of NPs into PEMs is an emerging field, this research will provide a better understanding of the formation and robustness of PEM-NP assemblies. By systematically varying the constituent polyelectrolytes and NPs of the assemblies, this research will identify the key parameters that govern the membranes? anti-adhesive and antimicrobial properties. The role of the terminating layer in controlling the anti-adhesive properties of a membrane will be examined by replacing the top layers in selected PEM-NP assemblies with layers of PGA-g-PEG, an extremely hydrophilic polyanion. This research will provide insights into the mechanisms of cytotoxicity of surface-immobilized NPs and probe the possible enhancement in membrane antimicrobial activity when antimicrobial chitosan is used as the constituent polycation. This research will create exciting opportunities for the development of the next-generation membrane filtration systems for water purification and potentially transform the way these processes are operated and maintained. Furthermore, this study will provide crucial information allowing for the safe-by-design production of nanocomposite membranes. This work will contribute significantly to the understanding of material design for biofilm prevention, which is also of relevance to the fields of material, chemical, and biomedical engineering. In this study, they will involve undergraduate students in all phases of the research effort. Research results will be disseminated through publications in peer-reviewed journals, student presentations at national scientific meetings, and the organization of a symposium. The broader impact will be further augmented by the involvement of the PI in organizing scientific activities for 5th grade students in a predominantly African American elementary school in inner-city Baltimore. Also, lectures on environmental technologies will be presented at a girls? high school in Washington, DC. The results from this project will also be integrated into a new environmental nanotechnology course at George Washington University.