Anisotropic Gold Nanorod Arrays for Plasmon-Enhanced\nElectrochemical Sensing

Electrochemical\n(bio)sensors are widely employed as point-of-care\ndevices for the detection of diverse analytes for health and environmental\npurposes as they can offer high sensitivity, rapid response, and applicability\nto miniaturization. However, the recorded electrochemical signals\nusually have a low signal-to-noise ratio, especially when nanoscaled\ntags are used for labeling in sensor architectures. This increases\nthe effects of interference, which would eventually lead to poorer\nreproducibility and limited sensor performance. Plasmon-enhanced electrochemistry\n(PEEC) is a recently growing field, which is based on the relationship\nbetween plasmonic nanostructures and their electrocatalytic function\nunder the localized surface plasmon resonance (LSPR) region for analytical-based\napplications. The integration of plasmonic nanostructured materials\nwith electrochemical sensor platforms can exhibit enhanced catalytic\nactivity and sensitivity when surface plasmons are created under light\nirradiation. Herein, we demonstrate the first-time use of anisotropic\ngold nanorod arrays (AuNRs) as the source of plasmonic enhancement\nin the electrochemical detection of doxorubicin (DOX), a chemotherapeutic\nagent. To achieve this, AuNRs were deposited onto carbon screen-printed\nelectrodes (cSPEs) at a deposition angle of 10° by the oblique\nangle deposition (OAD) technique. Based on the excitation of the surface\nusing an 808 nm near-infrared (NIR) laser, the plasmon-based catalytic\nenhancement on the electrochemical response of AuNRs-deposited cSPEs\nwas investigated using a redox mediator in comparison to bare cSPEs.\nThe effect of laser excitation time (0–120 s) and power (0.2–1.8\nW) on PEEC was optimized to clarify the plasmonic effect. Utilizing\nthe oriented surface alignment of nanorods, the effect of isotropy\nwas also investigated by directional laser excitation and found to\nbe an effective parameter due to possible plasmon trapping effects.\nThis plasmon-induced electrocatalytic enhancement enabled increased\nsensitivity for DOX detection, which shows its applicability as a\nproof-of-concept design in practical real-world sensor applications.