CAREER: Nanoscale Interactions of Stimuli-responsive Nanoparticles with Enzymes

活细胞使用酶来执行许多生物功能。这些酶作用于尺寸极小的细胞靶点，通常以纳米（十亿分之一米）长度尺度测量。这个CAREER项目旨在了解酶敏感的纳米材料如何与酶相互作用的基本机制。这一目标将通过开发纳米颗粒来实现，纳米颗粒通过改变颗粒大小和功能来响应特定类别的酶。此外，这些颗粒将模拟细胞中发现的天然存在的酶敏感蛋白质-组蛋白的功能。因此，开发的平台将回答与纳米级酶作用相关的几个基本问题，例如（1）纳米颗粒如何选择性地与靶酶相互作用，并拒绝与复杂生物环境中的其他大分子相互作用？以及（2）如何通过设计纳米材料的尺寸、形状、表面性质和化学组成来调节纳米材料的酶响应率和程度？对酶敏感纳米颗粒的结构和功能的深入了解将为设计能够选择性识别特定酶的智能纳米材料打开大门。然后，这些纳米平台将提供制备癌症药物递送系统、神经退行性疾病诊断剂、生物传感技术和污染控制机制的工具和技术。CAREER项目的教育目标有三管齐下的方法，集中在整个北达科他州的部落学院和初级本科学院。该方法旨在提高包容性，尽量减少高等教育中美洲原住民学生的流失。教育活动将包括（1）在项目期间与至少八个部落学院和Primitive本科院校导师进行点对点合作，以振兴这些学院的STEM教育学习资源，（2）北达科他州州立大学工程研究生课程的课程开发，以及（3）增加来自北达科他州贫困地区的本科生的研究参与。因此，本项目中所描述的研究活动将扩大纳米级相互作用的培训范围，并有助于在国家层面上提供STEM研究所需的专业人员。本CAREER项目的总体目标是解卷积和了解酶与酶响应聚合物体相互作用时发生的事件。聚合物囊泡是通过两亲性嵌段共聚物的自组装形成的纳米级膜结合囊泡，所述两亲性嵌段共聚物构成其膜。使用具有表观遗传活性的模型酶，组蛋白去乙酰化酶，主要研究者旨在研究聚合物囊泡的化学组成和纳米级特征的影响，这些聚合物囊泡能够识别靶酶并拒绝与脱靶生物大分子的相互作用。开发研究酶与动态响应纳米系统相互作用的平台具有挑战性，因为（1）酶对其纳米颗粒结合底物的可及性不仅取决于颗粒大小和电荷，还取决于分子拥挤和构象;（2）酶与底物在纳米尺度上相互作用的机制是特定环境线索的瞬时下游，以及（3）在周围分子的干扰下在纳米生物界面处提取分子水平结构/动力学信息是不平凡的。鉴于对用于治疗剂、农用化学品、环境修复和模拟细胞器的合成材料的生物分子递送平台的需求日益增加，迫切需要克服这些挑战。为了实现这个CAREER项目的目标，将实现三个策略：首先，PI将模拟组蛋白的酶响应模式-一种具有明确大小和结构的乙酰化赖氨酸的天然蛋白质，在活细胞中发现，与不同的表观遗传酶相互作用，如组蛋白脱乙酰酶;第二，酶在这种组蛋白模拟纳米平台上的相互作用机制，通过脱乙酰化反应（从赖氨酸残基的伯胺中除去乙酰基）介导的脱乙酰化反应将在结构上进行并建立。第三，能够正交检测分子水平相互作用的合成和实验技术将用于剖析纳米颗粒与酶相互接触的相互作用。这项研究活动的中心假设是，响应表观遗传酶的酶响应性聚合物囊泡的结构和功能变化是通过两亲性嵌段共聚物的疏水和亲水部分在水中的溶解度的反转来介导的，并且由酶对其位于纳米结构内的底物的可及性来控制。PI教育计划的主要教学理念包括通过沉浸式“导师对导师”计划与北达科他州部落学院和小学本科院校的导师联系，以继续和加强这些学院的STEM培训。此外，纳米粒子-酶相互作用的研究元素将与PI所在研究所的工程研究生课程开发相结合，这将被用于提高4年制研究生院中代表性不足的少数民族的入学率。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Living cells use enzymes to perform numerous biological functions. These enzymes work on cellular targets which are extremely small in size, oftentimes measured at the nanometer (one billionth of a meter) length scale. This CAREER project aims to understand the fundamental mechanisms of how enzyme-sensitive, nanoscale materials interact with an enzyme. This goal will be realized by developing nanoparticles, which respond to a particular class of enzymes by changing particle size and function. Further, these particles will mimic the function of a naturally occurring, enzyme-sensitive protein – histone – that is found in cells. The developed platform will therefore answer several fundamental questions related to enzyme actions at the nanoscale, such as (1) How nanoparticles selectively interact with a target enzyme and reject interactions with other macromolecules in the complex biological environment ? and (2) How to regulate the rate and extent of enzyme responsivity of nanoscale materials via engineering their size, shape, surface properties, and chemical composition? An in-depth understanding of the structure and function of enzyme-sensitive nanoparticles will open the gateway to designing smart nanomaterials capable of selectively recognizing a specific enzyme. These nano-platforms would then provide tools and techniques to prepare cancer drug delivery systems, diagnostic agents for neurodegenerative diseases, biosensing technologies, and mechanisms for pollution control. The educational goal of the CAREER project has three-pronged approaches centered on Tribal Colleges and Primary Undergraduate Institutes across North Dakota. The approach is aimed to increase inclusivity and minimize the loss of Native American students in higher education. The educational activity will include (1) peer-to-peer collaboration with at least eight Tribal College and Primarily Undergraduate Institution mentors over the project period to revitalize the learning resources of these institutes for STEM education, (2) curriculum development for the North Dakota State University engineering graduate program, and (3) increased research involvement of undergraduates from underprivileged areas across North Dakota. The research activity delineated in this project will thus expand the scope of training in nanoscale interactions and contribute to a robust supply of professionals needed in STEM research at the national level.The overarching goal of this CAREER project is to deconvolute and understand the events occurring when an enzyme interacts with an Enzyme-Responsive Polymersome. Polymersomes are nanoscale, membrane-bound vesicles formed via the self-assembly of amphiphilic block copolymers that constitutes their membranes. Using a model enzyme with epigenetic activity, histone deacetylase, the principal investigator aims to study the effect of chemical composition and nanoscale features of polymersomes that are capable of recognizing target enzymes and rejecting interactions with off-target biomacromolecules. Developing platforms to study enzyme interactions with dynamically-responsive nanosystems is challenging because (1) accessibility of an enzyme to its nanoparticle-bound substrates depends not only on the particle size and charge but also on molecular crowding and conformation; (2) the mechanism of enzyme interactions with substrates at the nanoscale is transient downstream of specific environmental cues, and (3) extracting molecular level structure/dynamics information at the nano-bio interface under the interference of surrounding molecules is non-trivial. Given the increasing need for biomolecular delivery platforms for therapeutics, agrochemicals, environmental remediation, and synthetic materials that mimic cellular organelles, there is a critical need to overcome these challenges. Three strategies will be realized to achieve the goal of this CAREER project: first, the PI will mimic the enzyme-responsivity pattern of a histone — an acetylated lysine-bearing natural protein of well-defined size and structure, found in living cells that interacts with different epigenetic enzymes, such as histone deacetylase; second, the mechanism of the enzyme interactions on this histone-mimetic nanoplatform, mediated by deacetylation reaction (removal of acetyl groups from primary amines of lysine residues) will be structurally followed and established. third, synthetic and experimental techniques capable of orthogonally detecting molecular-level interactions will be used to dissect the interactions of nanoparticles with enzymes in contact with each other. The central hypothesis of this research activity is that structural and functional changes of enzyme-responsive polymersomes in response to epigenetic enzymes are mediated mechanistically via the inversion of solubility of the hydrophobic and hydrophilic segment of the amphiphilic block copolymers in water and governed by the enzyme accessibility to its substrate located within the nanostructure. The main teaching philosophy of PI’s educational plan involves connecting with mentors serving tribal colleges and primary undergraduate institutes across the state of North Dakota via an immersive ‘Mentor- to-Mentor” program for the continuation and reinforcement of STEM training in these institutes. Further, the research elements of nanoparticle-enzyme interactions will be bridged with engineering graduate curriculum development in the PI’s home institute that will be harnessed to improve enrollments of under-represented minorities in 4-year graduate schools.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.