The air sensitivity of many substrates, and specifically biosurfaces, presents an experimental challenge for their analysis by vibrational spectroscopy and, in particular, infrared microscopy on a nanometer scale. The recent development of atomic-force-microscopy-based infrared spectroscopy (AFM-IR), which circumvents the Abbe diffraction limit, allows nanoscale chemical characterization of surfaces. Additionally, this technique has been shown to work for thin films under aqueous environments but is limited to substrates up to 10 nm thick, thus ruling out application to many biological surfaces. To circumvent this restriction, we have utilized hydrogels to cover such surfaces and maintain a more physiologically representative environment for biological substrates. We show that it is feasible to use AFM-IR to chemically characterize this type of substrate buried under a thin hydrogel film. Specifically, this work describes the AFM-IR spectra of red blood cells under polyvinyl alcohol hydrogels.

中文翻译：

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由水凝胶薄膜保护的空气敏感生物基质的红外纳米光谱

许多基材的空气敏感性，特别是生物表面，为它们的振动光谱分析，特别是纳米尺度的红外显微镜分析提出了实验挑战。最近开发的基于原子力显微镜的红外光谱 (AFM-IR) 绕过了阿贝衍射极限，允许对表面进行纳米级化学表征。此外，该技术已被证明适用于水性环境下的薄膜，但仅限于厚度达 10 nm 的基材，因此无法应用于许多生物表面。为了规避这一限制，我们利用水凝胶覆盖这些表面并为生物基质保持更具生理学代表性的环境。我们表明，使用 AFM-IR 对埋在水凝胶薄膜下的这种类型的基材进行化学表征是可行的。具体来说，这项工作描述了聚乙烯醇水凝胶下红细胞的 AFM-IR 光谱。