Localized Surface Plasmon Resonance Enhancement from Complex Nanoscale Geometries

The unprecedented COVID-19 pandemic highlights the need for portable, sensitive, and accurate biosensors. Here, a novel biosensor that takes advantage of localized surface plasmonic resonance (LSPR) through unique nanoscale geometries was fabricated for sensitive detection of biomarkers. The formation of an adaptable system capable of combining with other sensing methods, such as CRISPR-Cas13a assays, allowed for the detection of specific targets to be realized. In this system, streptavidin-coated gold nanoparticles (GNPs) hybridize with single-stranded RNA (ssRNA) before binding to the surface of gold nanomushrooms (GNMs). Through LSPR enhancement, this binding event produces a red shift in the resonance wavelength peak due to changes in the refractive index surrounding the GNMs. Various concentrations, shapes, and diameters of nanoparticles were investigated to determine the greatest possible resonant shift. Through this work, the use of streptavidin-coated 40 nm AuNPs produced the greatest redshift at ~30 nm for concentrations greater than 500 pM. Packaged in a microfluidic cell, the device offers a novel strategy for the detection of biomarkers with minimal sample preparation and rapid, label-free detection. Expanding this process to include CRISPR-Cas13a proteins incorporates the advantage of collateral cleavage which further enhances the sensitivity of LSPR, a critical and far-reaching bottleneck specifically of concern in label-free biosensing

Gold Nanoparticle Enabled Localized Surface Plasmon Resonance on Unique Gold Nanomushroom Structures for On‐Chip CRISPR‐Cas13a Sensing

Abstract A novel localized surface plasmon resonance (LSPR) system based on the coupling of gold nanomushrooms (AuNMs) and gold nanoparticles (AuNPs) is developed to enable a significant plasmonic resonant shift. The AuNP size, surface chemistry, and concentration are characterized to maximize the LSPR effect. A 31 nm redshift is achieved when the AuNMs are saturated by the AuNPs. This giant redshift also increases the full width of the spectrum and is explained by the 3D finite‐difference time‐domain (FDTD) calculation. In addition, this LSPR substrate is packaged in a microfluidic cell and integrated with a CRISPR‐Cas13a RNA detection assay for the detection of the SARS‐CoV‐2 RNA targets. Once activated by the target, the AuNPs are cleaved from linker probes and randomly deposited on the AuNM substrate, demonstrating a large redshift. The novel LSPR chip using AuNP as an indicator is simple, specific, isothermal, and label‐free; and thus, provides a new opportunity to achieve the next generation multiplexing and sensitive molecular diagnostic system

On-Demand Fully Enclosed Superhydrophobic-Optofluidic Devices Enabled by Microstereolithography.

Superhydrophobic surface-based optofluidics have been introduced to biosensors and unconventional optics with unique advantages, such as low light loss and power consumption. However, most of these platforms were made with planar-like microstructures and nanostructures, which may cause bonding issues and result in significant waveguide loss. Here, we introduce a fully enclosed superhydrophobic-based optofluidics system, enabled by a one-step microstereolithography procedure. Various microstructured cladding designs with a feature size down to 100 μm were studied and a T-type overhang design exhibits the lowest optical loss, regardless of the excitation wavelength. Surprisingly, the optical loss of superhydrophobic-based optofluidics is not solely decided by the solid area fraction at the solid/water/air interface, but also the cross-section shape and the effective cladding layer composition. We show that this fully enclosed optofluidic system can be used for CRISPR-labeled quantum dot quantification, intended for in vitro and in vivo CRISPR therapeutics