Abstract
Three-dimensional (3D) multilayered plasmonic nanostructures consisting of Au nanosquares on top of SU-8 nanopillars, Au asymmetrical nanostructures in the middle, and Au asymmetrical nanoholes at the bottom were fabricated through reversal nanoimprint technology. Compared with two-dimensional and quasi-3D plasmonic nanostructures, the 3D multilayered plasmonic nanostructures showed higher electromagnetic field intensity, longer plasmon decay length and larger plasmon sensing area, which are desirable for highly sensitive localized surface plasmonic resonance biosensors. The sensitivity and resonance peak wavelength of the 3D multilayered plasmonic nanostructures could be adjusted by varying the offset between the top and bottom SU-8 nanopillars from 31% to 56%, and the highest sensitivity of 382 and 442 nm/refractive index unit were observed for resonance peaks at 581 and 805 nm, respectively. Live lung cancer A549 cells with a low concentration of 5 × 103 cells ml−1 and a low sample volume of 2 μl could be detected by the 3D multilayered plasmonic nanostructures integrated in a microfluidic system. The 3D plasmonic biosensors also had the advantages of detecting DNA hybridization by capturing the complementary target DNA in the low concentration range of 10−14–10−7 M, and providing a large peak shift of 82 nm for capturing 10−7 M complementary target DNA without additional signal amplification.
Highlights
Quantitative and rapid detection of live cancer cells and DNA hybridization are critical aspects of cancer diagnosis, gene mutation, food safety, and environment protection
After reversal nanoimprint lithography (RNIL), the Intermediate polymer stamp (IPS) stamp was demolded at 20 °C, and the 3D multilayered nanostructures with residual layer were formed and hard-baked at 150 °C for 10 min to achieve good adhesion and mechanical properties of the layers of SU-8 nanopillars. 3D multilayered nanostructures could be generated by removing the residual SU-8
No transfer occurred at lower temperature and pressure of 65 °C and 10 bar because the top SU-8 layer was already crosslinked
Summary
Quantitative and rapid detection of live cancer cells and DNA hybridization are critical aspects of cancer diagnosis, gene mutation, food safety, and environment protection. Integration of microfluidic technology with various detection methods such as optical [5, 6], electrochemical [7], and mechanical [8] transduction have been employed for miniaturized POC devices Among these detection methods, localized surface plasmon resonance (LSPR)-based optical biosensors have shown significant advantages of being fast, highly sensitive, simple, and providing high signal-to-noise ratio [9]. To the best of our knowledge, our study is the first to report the 3D multilayered plasmonic nanostructures with Au layers on the top, middle, and bottom and the application on detecting live cancer cells and DNA hybridization with high sensitivity. The 3D multilayered plasmonic nanostructures fabricated by RNIL are high performance biosensors for detecting live cancer cells at low concentrations with large peak shift and DNA hybridization with high sensitivity
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