Ultrabright gap-enhanced Raman tags for high-speed bioimaging

Abstract

Surface-enhanced Raman spectroscopy (SERS) is advantageous over fluorescence for bioimaging due to ultra-narrow linewidth of the fingerprint spectrum and weak photo-bleaching effect. However, the existing SERS imaging speed lags far behind practical needs, mainly limited by Raman signals of SERS nanoprobes. In this work, we report ultrabright gap-enhanced Raman tags (GERTs) with strong electromagnetic hot spots from interior sub-nanometer gaps and external petal-like shell structures, larger immobilization surface area, and Raman cross section of reporter molecules. These GERTs reach a Raman enhancement factor beyond 5 × 10 9 and a detection sensitivity down to a single-nanoparticle level. We use a 370 μW laser to realize high-resolution cell imaging within 6 s and high-contrast (a signal-to-background ratio of 80) wide-area (3.2 × 2.8 cm 2 ) sentinel lymph node imaging within 52 s. These nanoprobes offer a potential solution to overcome the current bottleneck in the field of SERS-based bioimaging.

Gap-enhanced Raman tags for physically unclonable anticounterfeiting labels

“…2d) and the narrow linewidths of their vibrational Raman bands (see detailed mode assignments in Supplementary Table 1) along with their unique spectral profiles allows use of demultiplexing methods (e.g., CLS) to obtain a large encoding capacity. The off-resonantly excited GERTs (with a localized surface plasmon resonance in the visible range but excited by 785 nm near-infrared laser) show large Raman enhancement due to a combination of electromagnetic field enhancement and electron transport effect across molecular layer in the nanogaps 41,48 , and therefore lead to a number of important properties favorable for PUF labels: (1) large enhancement factor, detectable down to a single-NP level 42,49 , leading to the fastest (to the best of our knowledge) readout speed with a good signal-to-noise ratio; (2) ultra-photostability under repeated readout due to the offresonance excitation condition 37,50,51 , leading to excellent reproducibility; (3) ultra-stable material properties in various environments (for example, humid environment), resulting in easy storage and a long shelf-life of prepared labels 37 ; (4) suitability for NIR laser excitation, resulting in low Raman background from the PUF substrate or package materials. We have to emphasize that the conventional plasmonic dimers or aggregates are inappropriate for the PUF labels since the SERS hot spots from them are apt to photobleaching 37,52 .…”

“…6a) along with a SWIFT mode on the confocal Raman system was used 56 . To demonstrate highspeed readout in DuoScan mode, a PUF label (100 × 100 μm 2 ) fabricated using 4-NBT GERTs was mapped with a shortened exposure time of around 0.7 ms per pixel, which is by now the shortest acquisition time of commercial electron-multiplying charge-coupled device (EMCCD) as far as we know 42 . Only 6 s was needed to acquire a Raman map with a resolution of 50 × 50 pixels (Fig.…”

“…Herein we demonstrate fabrication and authentication of SERS-based PUF labels for anticounterfeiting. The labels are stochastic two-dimensional (2D) patterns formed by drop-casting various types of core-shell SERS nanoparticles (NPs), known as gap-enhanced Raman tags (GERTs) [37][38][39][40][41][42] , on a silica substrate (Fig. 1a).…”

Recent advances in surface-enhanced Raman spectroscopy for the detection of tumor markers

“…[66] : (a) 完整和切口的动脉粥 样硬化组织和非动脉粥样硬化组织的SERS光谱; (b) HA NSG小鼠体内炎症分子的非侵入性SERS光谱. 花瓣状缝隙增强拉曼探针(P-GERTs)用于 生物成像 [69] : (c) P-GERTs示意图和透射电子显微镜图; (d) 单个H1299细胞的拉曼图像及其3个不同位置的SERS光谱; (e) 注射P-GERTs后, 小鼠 肢腘窝淋巴结的高对比度、大范围活体拉曼成像 Figure 3 (Color online) Application of SERS in tumor markers detection of tissues. Multiplex molecular SERS imaging of vascular inflammation using gold nanoprobes [66] : (a) SERS spectra of the intact (left) and opened (right) artery on atherosclerotic and non-atherosclerotic tissues; (b) noninvasive in vivo SERS spectra of adhesion molecules on HA NSG mice.…”

“…Multiplex molecular SERS imaging of vascular inflammation using gold nanoprobes [66] : (a) SERS spectra of the intact (left) and opened (right) artery on atherosclerotic and non-atherosclerotic tissues; (b) noninvasive in vivo SERS spectra of adhesion molecules on HA NSG mice. Gap-enhanced Raman tags with a petal-like shell (P-GERTs) [69] : (c) Schematic diagram and TEM image of P-GERTs; (d) Raman image of a single H1299 cell and three representative SERS spectra obtained from different points in panel b; (e) high-contrast and wide-area in vivo Raman image of the hind-limb popliteal lymph node after injection of P-GERTs 合主成分分析, 该传感器可甄别模拟呼出气中特征分 子浓度是否达到阈值(图4(d)). 此外, Chen等人 [77] 利用 石墨烯和Au NPs, 根据呼出气中14种VOCs拉曼谱带提 供的指纹图谱, 区分了不同模拟呼气样本和200个临床…”