This review article discusses progress in surface plasmon resonance (SPR) of two-dimensional (2D) and three-dimensional (3D) chip-based nanostructure array patterns. Recent advancements in fabrication techniques for nano-arrays have endowed researchers with tools to explore a material’s plasmonic optical properties. In this review, fabrication techniques including electron-beam lithography, focused-ion lithography, dip-pen lithography, laser interference lithography, nanosphere lithography, nanoimprint lithography, and anodic aluminum oxide (AAO) template-based lithography are introduced and discussed. Nano-arrays have gained increased attention because of their optical property dependency (light-matter interactions) on size, shape, and periodicity. In particular, nano-array architectures can be tailored to produce and tune plasmonic modes such as localized surface plasmon resonance (LSPR), surface plasmon polariton (SPP), extraordinary transmission, surface lattice resonance (SLR), Fano resonance, plasmonic whispering-gallery modes (WGMs), and plasmonic gap mode. Thus, light management (absorption, scattering, transmission, and guided wave propagation), as well as electromagnetic (EM) field enhancement, can be controlled by rational design and fabrication of plasmonic nano-arrays. Because of their optical properties, these plasmonic modes can be utilized for designing plasmonic sensors and surface-enhanced Raman scattering (SERS) sensors.
Enzyme-linked
immunosorbent assay (ELISA) is the gold standard
method for protein biomarkers. However, scaling up ELISA for multiplexed
biomarker analysis is not a trivial task due to the lengthy procedures
for fluid manipulation and high reagent/sample consumption. Herein,
we present a highly scalable multiplexed ELISA that achieves a similar
level of performance to commercial single-target ELISA kits as well
as shorter assay time, less consumption, and simpler procedures. This
ELISA is enabled by a novel microscale fluid manipulation method,
composable microfluidic plates (cPlate), which are comprised of miniaturized
96-well plates and their corresponding channel plates. By assembling
and disassembling the plates, all of the fluid manipulations for 96
independent ELISA reactions can be achieved simultaneously without
any external fluid manipulation equipment. Simultaneous quantification
of four protein biomarkers in serum samples is demonstrated with the
cPlate system, achieving high sensitivity and specificity (∼
pg/mL), short assay time (∼1 h), low consumption (∼5
μL/well), high scalability, and ease of use. This platform is
further applied to probe the levels of three protein biomarkers related
to vascular dysfunction under pulmonary nanoparticle exposure in rat’s
plasma. Because of the low cost, portability, and instrument-free
nature of the cPlate system, it will have great potential for multiplexed
point-of-care testing in resource-limited regions.
Digital biosensing assays demonstrate remarkable advantages over conventional biosensing systems because of their ability to achieve single-molecule detection and absolute quantification. Unlike traditional low-abundance biomarking screening, digital-based biosensing systems reduce sample volumes significantly to the fL-nL level, which vastly reduces overall reagent consumption, improves reaction time and throughput, and enables high sensitivity and single target detection. This review presents the current technology for compartmentalizing reactions and their applications in detecting proteins and nucleic acids. We also analyze existing challenges and future opportunities associated with digital biosensing and research opportunities for developing integrated digital biosensing systems.
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