Nanospeckle illumination microscopy (NanoSIM) based on disordered metallic nanocomposite island substrates is described. The nanoisland substrates can be fabricated without lithographic techniques. Azimuthal scanning illumination of nanoislands creates near‐field distribution that excites an arbitrary number of basis images to produce super‐resolution. Experimental studies of point‐spread images using NanoSIM with 360 basis images obtained by azimuthal scanning find spatial resolution improved by more than three times with an achievable full‐width‐at‐half‐maximum at 81.1 nm on average. The approach is confirmed by imaging aggregated nanobeads and nanoscale distribution of gangliosides on the HeLa cell membrane.
In this article, we report the use of randomly structured light illumination for chemical imaging of molecular distribution based on Raman microscopy with improved image resolution. Random structured basis images generated from temporal and spectral characteristics of the measured Raman signatures were superposed to perform structured illumination microscopy (SIM) with the blind-SIM algorithm. For experimental validation, Raman signatures corresponding to Rhodamine 6G (R6G) in the waveband of 730–760 nm and Raman shift in the range of 1096–1634 cm−1 were extracted and reconstructed to build images of R6G. The results confirm improved image resolution using the concept and hints at super-resolution by almost twice better than the diffraction-limit.
Various plasmonic nanostructure-based substrates are used to detect biological signals beyond the diffraction limit with a high signal-to-noise ratio. These approaches take advantage of excitation of localized surface plasmon to acquire highfrequency biological signals while preserving photon energy. Numerous techniques, including focused ion beam, electronbeam lithography, and reactive ion etching, have been used to fabricate plasmonic substrates. However, these fabrication techniques are time and resource-consuming. In contrast, disordered nanostructure-based substrates have attracted interests due to the easy fabrication steps and potential cost savings. Metallic nanoisland substrates, for instance, can be massproduced using thin film deposition and annealing without lithographic process. In this work, we have investigated nanospeckle illumination microscopy (NanoSIM) using disordered near-field speckle illumination generated by nanoisland substrate. Selectively activated fluorescence wide-field images were obtained by nanospeckle illumination generated on the nanoisland substrate. Super-resolved fluorescence images were reconstructed by an optimization algorithm based on blind structured illumination microscopy. Experimental studies of various biological targets including HeLa cell membranes were performed to demonstrate the performance of NanoSIM. Using NanoSIM, we were able to improve spatial resolution of ganglioside distribution in HeLa cells targeted by CT-B by more than threefold compared to the diffraction-limited images. Note that the accessibility of super-resolution imaging techniques can be enhanced by the nanospeckle illumination of disordered metallic nanoislands. These results may be used in imaging and sensing systems that work with detecting biological signals beyond diffraction limits in various applications.
We investigated super-localized measurement of molecular distribution at cell membrane with surface plasmon localization. The plasmonic nanostructures could improve the precision of optical measurement over diffraction-limited microscopy techniques.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.