Austrian Institute of Technology, Donau-City-Strasse 1, 1220 Vienna, Austria.
Biosens Bioelectron. 2010 Mar 15;25(7):1663-8. doi: 10.1016/j.bios.2009.12.003. Epub 2009 Dec 11.
A novel label-free biosensor based on the measurement of binding-induced refractive index changes by hydrogel optical waveguide spectroscopy (HOWS) is reported. This biosensor is implemented by using a surface plasmon resonance (SPR) optical setup in which a carboxylated poly(N-isoproprylacrylamide) (PNIPAAm) hydrogel film is attached on a metallic surface and modified by protein catcher molecules through amine coupling chemistry. The swollen hydrogel with micrometer thickness serves both as a binding matrix and optical waveguide. We show that compared to regular SPR biosensor with thiol self-assembled monolayer (SAM), HOWS provides an order of magnitude improved resolution in the refractive index measurements and enlarged binding capacity owing to its low damping and large swelling ratio, respectively. A model immunoassay experiment revealed that HOWS allowed detection of IgG molecules (molecular weight 150 kDa) with a 10 pM limit of detection that was 5-fold lower than that achieved for SPR with thiol SAM. For the high capacity hydrogel matrix, the affinity binding was mass transport limited. Therefore, we envisage that HOWS will provide further improved detection limit for low molecular weight analytes or for assays employing lower affinity catcher molecules.
本文报道了一种基于水凝胶波导光谱（HOWS）测量结合诱导折射率变化的新型无标记生物传感器。该生物传感器通过使用表面等离子体共振（SPR）光学装置来实现，其中在金属表面上附着了羧基化聚（N-异丙基丙烯酰胺）（PNIPAAm）水凝胶膜，并通过胺偶联化学将蛋白质捕获分子修饰在其上。具有微米厚度的溶胀水凝胶既可用作结合基质又可用作光波导。我们表明，与具有硫醇自组装单层（SAM）的常规 SPR 生物传感器相比，HOWS 分别由于其低阻尼和大溶胀比，在折射率测量中提供了一个数量级的分辨率提高，并扩大了结合容量。一项模型免疫测定实验表明，HOWS 可以检测到 IgG 分子（分子量为 150 kDa），检测限为 10 pM，比具有硫醇 SAM 的 SPR 低 5 倍。对于高容量水凝胶基质，亲和结合受到质量传输限制。因此，我们预计 HOWS 将为低分子量分析物或使用低亲和力捕获分子的测定提供进一步提高的检测限。
