Reversal Nanoimprinted 3D Plasmonic Sensor Around Microposts for Cell and DNA Detection

Localized surface plasmon resonance biosensors are promising devices for label-free detection of live cells and biomolecules. However, typical plasmonic sensors have limited surface area, planar electromagnetic fields, and poor compatibility with three-dimensional (3D) interactions with cells or biomolecules. In this study, a 3D plasmonic sensor around microposts was developed using reversal nanoimprint lithography for highly sensitive cell and DNA detection. Au nanopillars were conformally integrated onto the bottom, sidewall, and top of microposts, forming additional sensing surface area along the sidewall of microposts for plasmonic sensing. The 3D plasmonic sensors exhibited tunable resonance peaks and refractive index (RI) sensitivities by varying the micropost height. The highest sensitivity of 1306 nm per RI unit was obtained from the sensor with 10 μm-tall microposts at a resonance wavelength of 1315 nm, which was significantly higher than that of typical planar plasmonic sensors. The platform was applied to live MC3T3-E1 cell detection, showing a resonance peak shift of 71 ± 11.6 nm at a cell concentration of 10⁶ cells/mL with a cell concentration ranging from 10² to 10⁶ cells/mL. In addition, DNA hybridization detection was demonstrated over a concentration range of 10^-15-10^-7 M complementary target DNA, with a resonance shift of 68 ± 2.5 nm observed at 10^-7 M target DNA concentration. The 3D plasmonic sensor provides a scalable device for additional plasmonic biointerfaces with enhanced analyte accessibility and light-matter interactions. This platform offers high-sensitivity biosensing involving live cells, nucleic acids, and other biological targets.