Accelerated Digital Biodetection Using Magneto-plasmonic Nanoparticle-Coupled Photonic Resonator Absorption Microscopy

Abstract

Rapid, ultrasensitive, and selective quantification of circulating microRNA (miRNA) biomarkers in body fluids is increasingly deployed in early cancer diagnosis, prognosis, and therapy monitoring. While nanoparticle tags enable detection of nucleic acid or protein biomarkers with digital resolution and subfemtomolar detection limits without enzymatic amplification, the response time of these assays is typically dominated by diffusion-limited transport of the analytes or nanotags to the biosensor surface. Here, we present a magnetic activate capture and digital counting (mAC+DC) approach that utilizes magneto-plasmonic nanoparticles (MPNPs) to accelerate single-molecule sensing, demonstrated by miRNA detection via toehold-mediated strand displacement. Spiky Fe3O4@Au MPNPs with immobilized target-specific probes are “activated” by binding with miRNA targets, followed by magnetically driven transport through the bulk fluid toward nanoparticle capture probes on a photonic crystal (PC). By spectrally matching the localized surface plasmon resonance of the MPNPs to the PC-guided resonance, each captured MPNP locally quenches the PC reflection efficiency, thus enabling captured MPNPs to be individually visualized with high contrast for counting. We demonstrate quantification of the miR-375 cancer biomarker directly from unprocessed human serum with a 1 min response time, a detection limit of 61.9 aM, a broad dynamic range (100 aM to 10 pM), and a single-base mismatch selectivity. The approach is well-suited for minimally invasive biomarker quantification, enabling potential applications in point-of-care testing with short sample-to-answer time.

Role of Nano-miRNAs in Diagnostics and Therapeutics

“…Several other nanosystems have been employed in the detection and quantification of miRNA, such as magneto-plasmonic nanoparticles (MPNPs) of the Fe 3 O 4 @Au MPNP kind, which exploited LSPR to detect a miR-375 cancer biomarker directly from unprocessed human serum with a 1 min response time, a LOD of 61.9 aM, a broad dynamic range (100 aM to 10 pM), and single-base-mismatch selectivity [ 70 ]. Polystyrene NPs were used to detect three colorectal-cancer-related miRNAs, miR-106a, miR-15a, and miR-21, with high sensitivity and low limits of detection [ 71 , 72 ].…”

Target Recycling Amplification Process for Digital Detection of Exosomal MicroRNAs Through Photonic Resonator Absorption Microscopy

“…By immobilizing target-activated AuNP probes on a PC surface, PRAM has been used to quantify nucleic acids and proteins with single-particle resolution. [29][30][31][32][33] As proof-of-concept studies for sensing miRNA, previous work focused on detecting chemically synthetic miRNAs, in which each detected miRNA molecule was associated with one AuNP tag 28,31 and lacked an amplification mechanism that could further reduce detection limits, as the target miRNA molecule is consumed by the detection process. To preprint (which was not certified by peer review) is the author/funder.…”

“…that can visualize individual gold nanoparticle (AuNPs) tags on a photonic crystal (PC) surface through resonance coupling. 27 As described in prior publications, [27][28][29][30][31][32][33] the detection principle of PRAM utilizes the resonant PC reflection at a wavelength of λ = 625 nm to provide a high reflected intensity from collimated low intensity LED illumination of the same wavelength into a webcam-variety image sensor.…”

Deep Learning Image Analysis of Nanoplasmonic Sensors: Toward Medical Breath Monitoring

“…Nanoplasmonics is a research area of growing importance that has increasingly contributed to enabling capabilities for developing cost-effective biomedical diagnostics. Much of the success has been in solution-phase detection, where lock-and-key binding creates readily detectable changes in interfacial optical properties. − Gas-phase plasmonic studies are much less common. − However, the advantages of plasmonic devices ,− ,− such as rapid response speed, high sensitivity, miniature size, and the capability for remote measurement by using an optical spectrometer/camera/photodetector outside the sampling chamber offer enormous possibilities for a broader range of gas-phase applications, one of which is the expanding need for noninvasive medical breath analysis and monitoring. ,− …”