Integration of Dual Functions of Cytosensing and Highly Efficient Photothermal Therapy Using a Cascaded Ω-Shaped Fiber Optic Localized Surface Plasmon Resonance Sensor

Elimination of circulating tumor cells (CTCs) is a promising way to inhibit tumor metastasis using antitumor devices. The current devices lack the functions for sensing the captured CTCs <i>in situ</i>, which causes potential toxicity and off-target effects in the therapy for CTCs. In this work, a novel cascaded Ω-shaped fiber optic functionalized with gold nanoparticles/gold nanobipyramids (AuNPs/AuNBPs) was prepared for the realization of cytosensing and photothermal therapy. The incorporation of a no-core fiber (NCF) segment in the Ω-shaped fiber optic enhanced the evanescent field <i>via</i> bending-induced loss and mode reconstruction, which was critically dependent on the bending diameter and NCF length. Under the optimal conditions, the fiber optic probe yielded an exceptionally high refractive index sensitivity of 962.9 nm/RIU and photothermal conversion efficiency. After the modification with T-shaped aptamers, the fiber optic probe enabled ultrasensitivity for the cytosensor with an ultralow limit of detection of 2.1 cells/mL. Since the localized surface plasmon resonance peak of the hybridized nanolayer matches well with the radiation laser, the cascaded Ω-shaped fiber optic probe can reach to a steady state within 1.3 s, which is 13-fold faster than that of the 600 μm Ω-shaped fiber optic probe under the same laser power. The cascaded Ω-shaped fiber optic probe effectively captured and then killed the target MCF-7 cells through precisely controlling photothermal ablation. With ultrasensitivity for cell sensing and high photothermal treatment efficiency, the fiber optic probe with compact dimensions would become a promising implanted device to eliminate CTCs in the blood vessel.