Enhanced Determination of Single-Stranded DNA (ssDNA) Using Gold-Nickel Nanomotors: A Multimodal Biosensing Approach

OpenAlex · İngilizce

The development of nanomotors and their integration with single-stranded DNA (ssDNA) detection systems represents a significant advancement in biosensing technologies. This study presents the fabrication of magnetic nanomotors composed of gold–nickel (Au–Ni) nanowires, which are further functionalized with polystyrene sulfonate (PSS) and polyallylamine (PAA) coatings. The cationic PAA outer layer enables the effective electrostatic binding of negatively charged ssDNA, leading to pronounced changes in both the optical and dynamic properties of the micromotors. Upon association of FAM-labeled ssDNA with the Au–Ni-PSS-PAA surface, the fluorescence intensity of the micromotors increases as a function of ssDNA concentration, while their speed under combined magnetic and near-infrared (NIR) actuation gradually decreases with increasing ssDNA loading due to additional hydrodynamic drag and modified surface charge, even though the dual actuation condition itself enhances the propulsion of the bare micromotors. In the present proof-of-concept system, selectivity is primarily governed by electrostatic interactions between the positively charged PAA coating and the anionic phosphate backbone of ssDNA, although the platform is readily adaptable to sequence-specific detection via immobilized complementary probes. The unique combination of magnetic and plasmonic (NIR-responsive) properties in these micromotors enables dual-mode detection, integrating motion-based (speed variation under external magnetic and NIR stimuli) and optical (fluorescence intensity) readouts into a single biosensing platform. The detection limit for motion-based ssDNA sensing with Au–Ni-PSS-PAA micromotors is 200 nM, whereas it is 46 nM when analyzed by optical methods. This dual-modality operation enables sensitive and reliable ssDNA detection for diagnostics, environmental monitoring, and forensics.