Fabrication of Ag nanoplate-bio tip for evaluation of the binding between proteins and small molecules

利用三角形纳米银片（Ag NPLs），开发了一种结合局部表面等离子体共振（LSPR）传感和基质辅助激光解吸/电离-质谱（MALDI-MS）的互补分析方法。以银纳米粒子为原料，采用两步光介导生长工艺制备了具有近红外LSPR吸光度的银NPLs。这些材料可以作为LSPR/MALDI-MS的通用平台，因为它们适合通过分析表面等离子体吸附带进行LSPR传感，并且可以作为LDI-MS的辅助材料。在实际应用中，LSPR传感对分析物的检测可以通过使用特定的生物分子识别技术来实现，这些技术涉及用大分子（如蛋白质）修饰金属NPs的表面。我们研究了用不同大小的分子修饰Ag表面对LSPR灵敏度（即折射率单位RIU）的影响，发现RIU值与分子量的立方根Mw1/3的振幅成正比。我们通过评估大豆胰蛋白酶抑制剂与经胰蛋白酶共价修饰的Ag NPL底物的结合，证明了这种互补的LSPR和MALDI-MS分析方法的实用性。这种特异性的生物分子识别现象首先通过LSPR技术检测到，然后通过MALDI-MS成功鉴定。

A complementary analytical methodology combining localised surface plasmon resonance (LSPR) sensing and matrix assisted laser desorption/ionisation-mass spectrometry (MALDI-MS) has been developed by using triangular silver nanoplates (Ag NPLs). Ag NPLs with near-IR LSPR absorbance were prepared via a two-step photo-mediated growth process from Ag nanoparticles. These could be utilised as a common platform for LSPR/MALDI-MS, as they were suitable for LSPR sensing via the analysis of surface plasmon adsorption bands and as the assisting material for LDI-MS. For practical use, the detection of analytes by LSPR sensing can be achieved by using specific biomolecular recognition techniques that involve the surface modification of metal NPs with large molecules such as proteins. We investigated the effect on LSPR sensitivity (i.e. refractive index unit, RIU) of modifying the Ag surface with molecules of different sizes, and found that the RIU values were proportional to the amplitude of the cube root of the molecular weight, Mw1/3. We demonstrated the utility of this complementary LSPR and MALDI-MS analysis methodology by evaluating the binding of soy bean trypsin inhibitor to the Ag NPL substrate covalently modified with trypsin. This specific biomolecule recognition phenomenon was first detected using the LSPR technique, and then successfully identified by the MALDI-MS.