We present a nanoparticle (NP) enhanced imaging-based plasmonic biosensing technique using gold nanohole arrays (Au-NHAs) that enables highly sensitive protein detection with single analyte resolution in a one-step sandwich immunoassay. By digital quantification of individual Au-NP bound molecules on large area plasmonic surface, the portable biosensor enables rapid and robust detection of disease biomarkers from patient serum in hospital settings. Using mass-scalable deep-UV lithography (DUVL) sensor fabrication and simple LED based imaging set-up in a microarray format, our novel technology provides a powerful tool for clinical biomarker detection in a highly multiplexed manner.
We propose a disruptive point-of-care (PoC) imaging platform based on lens-free interference phase-contrast imaging for rapid detection of biomarker such as for sepsis and potentially other diseases (e.g. cancer). It enables simultaneous analysis of potentially up to 10,000 functionalized microarray spots with different biomarkers with fast time-to-results (few minutes) and by consuming a small sample volume (~10 μL). The high sensitivity allows direct measurements of the biomarker binding without the use of fluorescent labels (e.g. ELISA) or microbial culture methods. In addition, adhoc plasmonic nano-structuring is utilized to significantly improve the sensitivity for biomarker detection (optical path difference ~Å) to concentration levels relevant for disease diagnosis.
The proposed technology incorporates a portable and low-cost lens-free imaging reader made of consumer electronic components, plasmonic microarrays with distinct functionalization, and user-friendly software based on a novel phaseshifting interferometry method for topography and refractive index analysis. Due to its compactness and cost-efficiency, we foresee a great potential for PoC applications, especially for the rapid detection of infectious diseases or lifethreatening conditions, e.g. sepsis, but also for clinical trials of drugs and food control.
The implementation of multiplexed point-of-care biosensors is a top priority to address the current epidemic problems originated by widespread pathogenic infections, like those caused by viruses or bacteria. A rapid and accurate detection, identification, and quantification of the infectious pathogens is essential not only to facilitate a prompt treatment but also to prevent onward transmission, reduce economic expenses, and significantly promote healthcare in resource-constrained environments. We have developed a nanoplasmonic biosensor based on nanohole arrays for fast and highly sensitive analysis in a simple and direct configuration. Our microarray is integrated into a microfluidic system to allow for highthroughput detection of multiple targets in a few minutes, without the need of sample pretreatment or amplification steps. Previously, we demonstrated the utility of the biosensor for the detection of hazardous live viruses, such as the Ebola or Vaccinia viruses, measured directly in biological media. Most recently we proved the truly multiplexing capability of our plasmonic microarray with the simultaneous identification and quantification of Chlamydia trachomatis and Neisseria gonorrhoeae in urine samples. We are able to detect and distinguish the two different bacteria with detection limits in the range of 102 -103 bacteria/mL. With recent advances in plasmonics, optimized surface chemistry, and microfluidics integration, our biosensors could provide a non-invasive and rapid diagnosis at the point of care, especially when we combine the detection on a compact and low-cost optical reader.
Cell signaling activities play a critical role in physiological and disease processes. The analysis of the tumor microenvironment or the immune system activation is nowadays providing valuable insights towards disease understanding and novel therapies development. Due to the various dynamic profiles, it is essential to implement a continuous monitoring methodology for accurate analysis. The current fluorescent and colorimetric approaches hinder such applications due to their multiple time-consuming steps, molecular labeling, and the ‘snapshot’ endpoint readouts. Photonics technology, and especially nanoplasmonic biosensors offer a unique opportunity to implement lab-on-a-chip systems that provide highly sensitive and label-free analysis of cell signaling events in real time. Here, we will present a microfluidics-integrated nanoplasmonic biosensor for long-term and real-time monitoring of cell secretion activity. The biosensor consists of a gold nanohole array supporting extraordinary optical transmission (EOT), which has been optimized to enable ultra-sensitive and high-throughput biomolecular detection. The nanobiosensor is integrated with a specifically designed microfluidic system that provides well-controlled cell culture conditions for long-term monitoring. We achieved an outstanding sensitivity for the detection of vascular endothelial growth factor (VEGF) directly secreted from microfluidic-cultured cancer cells. We demonstrated real-time monitoring for over 10 hours, preserving good cell viability. The multiplexing capability of our nanobiosensor could enable simultaneous analysis of different cell types and molecules-of-interest. Thus, our innovative approach of probing live cells can be a powerful tool to evaluate cellular activities for diagnostics and novel therapy development.
Our goal is to develop a rectifying antenna (rectenna) applicable to solar spectrum energy harvesting. In particular, we
aim to demonstrate viable techniques for converting portion of the solar spectrum not efficiently converted to electric
power by current photovoltaic approaches. Novel design guidelines are suggested for rectifying antenna coupled
tunneling diodes. We propose a new geometric field enhancement scheme in antenna coupled tunneling diodes that uses
surface plasmon resonances. For this purpose, we have successfully implemented a planar tunneling diode with
polysilion/SiO2/polysilcon structure. An antenna coupled asymmetric tunneling diode is developed with a pointed
triangle electrode for geometric field enhancement. The geometrically asymmetric tunneling diode shows a unique
asymmetric tunneling current versus voltage characteristic. Through comparison with crossover tunneling diodes, we
verified that the current asymmetry is not from the work function difference between the two electrodes. Results of RF
rectification tests using the asymmetric diode demonstrate that our approach is practical for energy harvesting
application. Furthermore, we describe how surface plasmons can enhance the electric field across the tunnel junction,
lowering the effective "turn-on" voltage of the diode, further improving rectification efficiency.