NER: Chemical Probing of Biosensor Nano-environments using Dynamic AFM

生物传感器在基因组分析、战剂检测和医学诊断中正变得越来越重要。为了优化这些设备的性能，必须开发新的工具来表征支撑其功能的分子水平现象。这一探索性的纳米技术方案旨在开发一种新的方法来测量生物传感器表面的纳米特性，利用原子力显微镜(AFM)在动态模式下的超精细分辨率。它们必须鼓励特定分析物的结合，而不鼓励外来物质的结合。通常，这些目标是通过构建具有防污聚合物的异质表面以及针对所需分析物的受体来实现的。为了在不牺牲选择性的情况下最大限度地提高产量，必须在表面施加最佳的聚合物密度和厚度。在这项工作中，PI希望测量生物分子在传感器表面附近穿过的纳米级能量景观，试图指导生物传感器的合理设计。对于真实的测量，必须同时测量聚合物空间相互作用和特定配体-受体相互作用。动态AFM方法包括振动AFM悬臂梁和测量当样品接近AFM尖端时的幅度衰减。振幅衰减对聚合物空间作用力比偏转更敏感，因此可以使用特定配体-受体测量所需的尖锐尖端。在此，PI将在模型生物传感器系统中测量动态和常规AFM力曲线。通过对悬臂振动的理论描述，我们希望证明动力学方法的敏感性和准确性。如果成功，该项目将在多个方面产生影响。首先，这项技术将提供与生物传感器相关的异质表面的独特纳米探测器。它还将能够以纳米级的横向分辨率测量聚合物的立体作用力，这对润滑和胶体加工具有重要意义。最后，由于在聚合物环境中，上皮细胞和细菌细胞表面也同时含有特定的黏附受体，动态AFM力方法可能成为研究细胞-细胞和细胞-表面黏附的有力工具。

Biosensors are becoming increasingly important for genomic analysis, detection of warfare agents, and medical diagnostics. To optimize the performance of these devices, new tools must be developed to characterize the molecular-level phenomena that underlie their function. This exploratory nanotechnology proposal aims to develop a new method to measure nanoscopic properties of biosensor surfaces, utilizing the ultrafine resolution of atomic force microscopy (AFM) in dynamic mode.Biosensors must perform two functions at once. They must encourage the binding of specific analytes while discouraging the binding of adventitious material. Typically, these goals are achieved by building heterogeneous surfaces with antifouling polymers together with receptors specific for desired analytes. To maximize yield without sacrificing selectivity, an optimal density and thickness of polymer must be applied to the surface. In this work, the PI hopes to measure the nanoscopic energy landscape that a biomolecule traverses near the sensor surface in an attempt to guide the rational design of biosensors. For a realistic measurement, both polymer steric interactions and specific ligand-receptor interactions must be measured simultaneously.The dynamic AFM method involves oscillating the AFM cantilever and measuring the amplitude attenuation as the sample approaches the AFM tip. Amplitude attenuation is more sensitive to polymer steric forces than deflection, so the sharp tips required for specific ligand-receptor measurements can be used. Here, the PI will measure dynamic and conventional AFM force curves in a model biosensor system. Using a theoretical description of cantilever oscillation, we hope to demonstrate the sensitivity and accuracy of the dynamic method.If successful, the project will have an impact on many fronts. First, the technique will provide a unique nanoscopic probe of heterogeneous surfaces pertinent to biosensors. It will also be able to measure polymer steric forces with nanometer lateral resolution, with implications for lubrication and colloidal processing. Finally, since epithelial and bacterial cell surfaces also contain specific adhesion receptors together in a polymeric environment, the dynamic AFM force method may emerge as a powerful tool in the study of cell-cell and cell-surface adhesion.