The importance of correcting for variable probe-sample interactions in AFM-IR spectroscopy: AFM-IR of dried bacteria on a polyurethane film
The importance of correcting for variable probe-sample interactions in AFM-IR spectroscopy: AFM-IR of dried bacteria on a polyurethane film
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DOI：
10.1039/c6an00940a
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发表时间：
2016-01-01
期刊：
影响因子：
4.2
通讯作者：
Russell, John N., Jr.
中科院分区：
文献类型：
--
作者：
Barlow, Daniel E.;Biffinger, Justin C.;Russell, John N., Jr.
AFM-IR是一种结合原子力显微镜-红外光谱的方法，有望用于生物材料相互作用的纳米级化学表征。在努力应用这种方法来定量探测微生物引起的聚氨酯降解机制，我们已经研究了单层集群的类似200 nm厚的假单胞菌Pf-5细菌（Pf）的300 nm厚的聚醚聚氨酯（PU）膜。在这里，不同的生物和聚合物机械性能对热机械AFM-IR检测机制的影响首先进行了评估，而没有聚合物降解的额外复杂性。将PF和PU的AFM-IR谱图与FTIR谱图进行了比较，两者吻合较好。局部AFM-IR光谱的Pf对PU（Pf-PU）表现出两种成分的频带，表明AFM-IR是敏感的化学成分在表面和下面。Pf-PU上局部AFM-IR光谱的一个明显差异是与Pf接触的探针相对于PU的IR峰强度异常增加4倍。这归因于探针-样品相互作用的差异。特别是，观察到探针与PU接触的悬臂梁阻尼明显更高，Q因子小了10倍。单波长AFM-IR化学绘图也受到影响。我们演示了化学分析的映射数据的比率作为一种简单的方法来消除变量探针-样品相互作用的极端影响。
AFM-IR is a combined atomic force microscopy-infrared spectroscopy method that shows promise for nanoscale chemical characterization of biological-materials interactions. In an effort to apply this method to quantitatively probe mechanisms of microbiologically induced polyurethane degradation, we have investigated monolayer clusters of similar to 200 nm thick Pseudomonas protegens Pf-5 bacteria (Pf) on a 300 nm thick polyether-polyurethane (PU) film. Here, the impact of the different biological and polymer mechanical properties on the thermomechanical AFM-IR detection mechanism was first assessed without the additional complication of polymer degradation. AFM-IR spectra of Pf and PU were compared with FTIR and showed good agreement. Local AFM-IR spectra of Pf on PU (Pf-PU) exhibited bands from both constituents, showing that AFM-IR is sensitive to chemical composition both at and below the surface. One distinct difference in local AFM-IR spectra on Pf-PU was an anomalous similar to 4x increase in IR peak intensities for the probe in contact with Pf versus PU. This was attributed to differences in probe-sample interactions. In particular, significantly higher cantilever damping was observed for probe contact with PU, with a similar to 10x smaller Q factor. AFM-IR chemical mapping at single wavelengths was also affected. We demonstrate ratioing of mapping data for chemical analysis as a simple method to cancel the extreme effects of the variable probe-sample interactions.