Multi-readout thermoplasmonic biosensor for rapid detection of oligonucleotides

Developing user-friendly, high-performance sensing devices for nucleic acid detection is crucial for diagnostics, drug development, and personalized therapies. Nanotechnologies offer innovative solutions to meet this need, utilizing the organization and functionalization of nanomaterials. This study presents a paradigm shift in sensing applications, exploiting the morphological and optical properties of gold nanorods (AuNRs) immobilized on a rigid substrate and functionalized with DNA oligonucleotides, creating a DNA–plasmonic microarray. Fabricated through a water-based layer-by-layer electrostatic assembly technique, this method avoids DNA modification. Scanning electron and atomic force microscopy reveal that the AuNRs–DNA microarray has suitable morphological properties to promote DNA hybridization. The photothermal properties of the plasmonic microarray are employed to monitor oligonucleotide hybridization under near-infrared laser irradiation. This approach yields a multi-readout plasmonic biosensor, detecting oligonucleotides by absorption spectroscopy due to its sensitivity to refractive index changes. Additionally, the AuNRs–DNA microarray's unique morphology allows a selective quantification of target DNA sequences through fluorescent imaging and photoluminescence spectroscopy, achieving a detection limit of 0.39 µM, comparable to similar plasmonic-based devices, while adding reusability. This thermoplasmonic-controlled, multi-readout, and reusable biosensor offers promising potential for bioanalytical applications.