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

PIS：陈凯龙/宝霞MiProposal编号：1133559/1134233超滤膜因其能有效去除水中病原体和颗粒物而越来越多地被用于饮用水处理和废水回用。然而，由于进水中微生物的普遍存在，超滤过程经常会受到生物污染的阻碍，这会减少清洁水的产量，缩短膜寿命，增加能源需求。目前，减缓生物污染的努力主要集中在使用消毒剂上，消毒剂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利用聚电解质多层膜(PEMS)将抗菌纳米颗粒(NPs)固定在聚砜超滤膜表面，以提高其抗生物污染能力。与传统的纳米复合膜制备方法相比，使用PEMS将具有以下优势：(1)PEMS可以增加膜表面的电荷和/或亲水性，从而减少细菌附着；(2)PEMS确保NPs位于膜表面，这将增强细菌的灭活；以及(3)PEMS的应用是非破坏性的，当膜受到污染或NPs溶解时，PEM-NP组装可以在原位再生。这些实验旨在验证这样一种假设，即经PEMS修饰的膜对生物污染的抵抗力是由其抗粘连和抗菌性能控制的。PEM参数(例如，组成聚电解质和NPs以及PEM中的双层数)将被系统地改变，以研究它们对膜的防粘和抗菌性能的影响。为了探索S膜的防粘连性能，将测量过滤过程中细菌在膜上沉积的动力学，以及细菌与膜表面的粘附力。膜的抗菌性能将通过对膜表面细菌菌落的计数和使用荧光染料技术来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，将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。这项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，本研究将考察几种在膜表面原位再生PEM-NP组件的物理和化学方法，并对再生膜的性能进行评估。这项研究是新颖的，因为它是第一次探索使用PEMS来制备抗生物污染的纳米复合膜。由于NPs与质子交换膜的结合是一个新兴的领域，本研究将有助于更好地了解PEM-NP组装的形成和稳定性。通过系统地改变组件的组成聚电解质和NPs，这项研究将确定支配膜的关键参数？防粘连和抗菌性能。通过将选定的PEM-NP组件中的顶层替换为PGA-g-PEG层(一种极亲水的聚阴离子)，将考察终止层在控制膜的防粘连性能中的作用。本研究将为研究表面固定化纳米粒子的细胞毒性机制提供依据，并探讨抗菌剂壳聚糖作为组成阳离子时对膜的抗菌活性可能增强的可能性。这项研究将为下一代净水膜过滤系统的开发创造令人兴奋的机会，并可能改变这些过程的操作和维护方式。此外，这项研究将为设计安全生产纳米复合膜提供重要信息。这项工作将有助于理解防止生物被膜的材料设计，这也与材料、化学和生物医学工程领域相关。在这项研究中，他们将让本科生参与研究工作的所有阶段。研究成果将通过在同行评议的期刊上发表文章、在国家科学会议上发表学生报告和组织研讨会来传播。通过参与在巴尔的摩市中心一所以非裔美国人为主的小学为五年级学生组织科学活动，更广泛的影响将进一步扩大。另外，关于环境技术的讲座将在一个女孩会议上发表。华盛顿特区的一所高中。该项目的成果还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.