Addressable nanoantennas with cleared hotspots for single-molecule detection on a portable smartphone microscope

Abstract

The advent of highly sensitive photodetectors and the development of photostabilization strategies made detecting the fluorescence of single molecules a routine task in many labs around the world. However, to this day, this process requires cost-intensive optical instruments due to the truly nanoscopic signal of a single emitter. Simplifying single-molecule detection would enable many exciting applications, e.g., in point-of-care diagnostic settings, where costly equipment would be prohibitive. Here, we introduce addressable NanoAntennas with Cleared HOtSpots (NACHOS) that are scaffolded by DNA origami nanostructures and can be specifically tailored for the incorporation of bioassays. Single emitters placed in NACHOS emit up to 461-fold (average of 89 ± 7-fold) brighter enabling their detection with a customary smartphone camera and an 8-US-dollar objective lens. To prove the applicability of our system, we built a portable, battery-powered smartphone microscope and successfully carried out an exemplary single-molecule detection assay for DNA specific to antibiotic-resistant Klebsiella pneumonia on the road.

Cellphone enabled point-of-care assessment of breast tumor cytology and molecular HER2 expression from fine-needle aspirates

“…We attribute the improved performance observed with the EpiView-D4 to improved illumination and increased noise rejection efficiency due to the epifluorescence optical configuration. For other applications, the sensitivity of our device could be further improved by switching to a monochromic camera-embedded smartphone 64 , or combining with other signal enhancement strategies, such as surface-enhanced fluorescence 65 , 66 .…”

Few-Molecule Strong Coupling with Dimers of Plasmonic Nanoparticles Assembled on DNA

“…The DNA-based assembly of dimers of plasmonic nanoparticles, with diameters ranging from 40 and 100 nm, has been shown to be a flexible and robust approach to enhance the spontaneous emission of single emitters in a weak coupling regime. ,− In particular, it allows a nanoscale control over the interparticle distance and over the position of the emitter in the gap. ,,, This method also permits the controlled introduction of multiple emitters, in particular to modulate resonant energy transfer. − It is therefore an attractive approach to efficiently couple a known number of fluorescent molecules to a plasmonic resonator in order to reach a strong coupling regime.…”

Viral detection and identification in 20 min by rapid single-particle fluorescence in-situ hybridization of viral RNA

“…However, as brighter particles (like fluorescent beads) can be used for this calibration, single molecule detection is not a requirement, and virus particles (which bind ~ 20 probes on average) should already be detectable by less sensitive microscopes. Improving particle brightness by expanding the probe arrays would bring down the technical requirements even more, to the point where mobile microscopy equipment might be used 47 , 48 . The microscopy skills required from the testing personnel or experimenter can be reduced by automated acquisition, auto-focusing, or having a microscope with a fixed axial position.…”