Thermo-Plasmonic Trapping of Living Cyanobacteria on a Gold Nanopyramidal Dimer Array: Implications for Plasmonic Biochips

With implication of developments of plasmonic biochips, we investigated laser trapping of cyanobacteria (CB) on a gold nanostructure, where a nanopyramidal dimer array was integrated. Upon near-infrared (808 nm) laser irradiation of the sample solution, CB cells were immediately collected, trapped, and permanently fixed onto the irradiated area of the nanostructure. About 15 CB cells were fixed to form a ring pattern. Because bubble generation was always necessary for CB fixation, the fixation was not because of a plasmon-enhanced optical force but because of hydrodynamic pressure modulation and Marangoni convection around the bubble. The bubble was generated by a photothermal effect to boil water. The fixation mechanism would be analogous to that of bubble nanolithography. We examined bioactivity and viability of CB cells using fluorescence microspectroscopy. Our method would be applicable to develop living-cell-based biodevices.