CIC biomaGUNE, Basque Research and Technology Alliance (BRTA), 20014 San Sebastián, Spain.
Biomedical Research Networking Center in Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), 20014 Donostia-San Sebastián, Spain.
ACS Nano. 2021 May 25;15(5):8984-8995. doi: 10.1021/acsnano.1c01878. Epub 2021 May 13.
The development of continuous monitoring systems requires sensors that are capable of screening multiple chemical species and providing real-time information. Such measurements, in which the sample is analyzed at the point of interest, are hindered by underlying problems derived from the recording of successive measurements within complex environments. In this context, surface-enhanced Raman scattering (SERS) spectroscopy appears as a noninvasive technology with the ability of identifying low concentrations of chemical species as well as resolving dynamic processes under different conditions. To this aim, the technique requires the use of a plasmonic substrate, typically made of nanostructured metals such as gold or silver, to enhance the Raman signal of adsorbed molecules (the analyte). However, a common source of uncertainty in real-time SERS measurements originates from the irreversible adsorption of (analyte) molecules onto the plasmonic substrate, which may interfere in subsequent measurements. This so-called "SERS memory effect" leads to measurements that do not accurately reflect varying conditions of the sample over time. We introduce herein the design of plasmonic substrates involving a nonpermeable poly(lactic-co-glycolic acid) (PLGA) thin layer on top of the plasmonic nanostructure, toward controlling the adsorption of molecules at different times. The polymeric layer can be locally degraded by irradiation with the same laser used for SERS measurements (albeit at a higher fluence), thereby creating a micrometer-sized window on the plasmonic substrate available to molecules present in solution at a selected measurement time. Using SERS substrates coated with such thermolabile polymer layers, we demonstrate the possibility of performing over 10,000 consecutive measurements per substrate as well as accurate continuous monitoring of analytes in microfluidic channels and biological systems.
连续监测系统的发展需要能够筛选多种化学物质并提供实时信息的传感器。这种在感兴趣的点对样品进行分析的测量方法受到复杂环境中连续测量记录所产生的潜在问题的阻碍。在这种情况下，表面增强拉曼散射（SERS）光谱学作为一种非侵入式技术出现，具有识别低浓度化学物质的能力以及在不同条件下解析动态过程的能力。为此，该技术需要使用等离子体基底，通常由金或银等纳米结构金属制成，以增强吸附分子（分析物）的拉曼信号。然而，实时 SERS 测量中的一个常见不确定性来源源于（分析物）分子不可逆地吸附在等离子体基底上，这可能会干扰后续的测量。这种所谓的“SERS 记忆效应”导致测量结果不能准确反映样品随时间变化的条件。我们在此引入了涉及在等离子体纳米结构顶部的不可渗透的聚（乳酸-共-羟基乙酸）（PLGA）薄层的等离子体基底的设计，以控制不同时间的分子吸附。该聚合物层可以通过用与用于 SERS 测量相同的激光照射局部降解（尽管在更高的通量下），从而在等离子体基底上创建一个可用的、尺寸为微米级的窗口，用于在选定的测量时间存在于溶液中的分子。使用涂覆有这种热不稳定聚合物层的 SERS 基底，我们证明了每个基底进行超过 10000 次连续测量以及在微流控通道和生物系统中对分析物进行准确连续监测的可能性。
