We have for the past ten years been developing and exploring solid SERS substrates based on gold or silver coated nanopillars. Recently, we have, with kind support from the Danish Bio Innovation Institute, focused on developing a SERS based platform for therapeutic drug monitoring (TDM). Here, we detect e.g., anti-cancer drugs in patient blood samples, to monitor if the patient is receiving a correct dose within the therapeutic window. The vision is to be able to provide a tool for personalized treatment of critical diseases where correct dosing is essential and where a wrong dose can be lethal or cause severe side effects. We will share our recent findings and the prototype of a complete TDM device, with integrated sample pre-treatment using centrifugal microfluidics.

Changes in the real and imaginary parts of the waveguide effective index in the presence of analytes have been used in various microcavity and slow light devices for on-chip sensing and absorption spectroscopy respectively in diverse applications. Periodically patterned waveguide sensors in interferometer configurations can lead to small interferometer sizes comparable in dimensions to microcavity resonator sensors, and/or significantly higher sensitivities compared to resonator type sensors. We show our work with compact silicon photonic interferometer devices for on-chip biosensing and absorbance sensing, overcoming fabrication tolerances with post-fabrication phase trimming.

Organ-on-chip (OoC) models have recently attracted considerable attention in the biomedical community as they have the potential to replace mouse models for studying human pathophysiology and associated treatment outcomes. My research focuses on the integration of photonic ring resonator biosensors that can detect senescence-associated secreted phenotype (SASP) factors as markers of aberrant wound healing in a human tendon-on-chip (hToC) device. Current methods to measure biomolecular analytes in OoC systems are mostly limited to media sampling and endpoint assays. By integrating photonic sensors, I have performed time-course measurements of CCL2/MCP-1, CCL3/MIP-1α, IL-6, and IL-17A levels over several hours in hToC cocultures.

Microchip technology is the pervasive solution across functions ranging from communications and computation to sensing and imaging, for products ranging from washing machines to automobiles and mega-scale data centers. How will technology roadmaps that guide supply chain readiness acquire three dimensionality to simultaneously optimize technology, ecology, and workforce? Sustainability as it applies to photonic integrated circuit sensor manufacturing will be discussed.

I will describe a point-of-care diagnostic that we have developed, in which all reagents are printed and stored on a “non-fouling”—protein and cell resistant— polymer brush. The D4 assay involves four sequential events: (1) Dispense (droplet of blood); (2) Dissolve (printed reagents on chip); (3) Diffuse (across surface); and (4) Detect (binding event). The D4 assay consists of microarrays of printed on the polymer polymer brush yields quantitative results, with picomolar sensitivity within an hour. All reagents are inkjet-printed and stored on D4 chips, which do not require refrigeration. Upon application of a drop of blood to the D4 chip, analyte capture and detection on the D4 chip occurs automatically, generating an image of fluorescent spots that is imaged by a hand-held detector and quantified by an on-board App. Examples of quantitative dose-response from whole blood will be presented and from patient samples. A plasmonically enhanced version of this assay will also be described.

Several scenarios require very fast (<5min) detection of various pathogens at the point of care or need (POC/N), including screening for highly infectious pathogens, life threatening conditions, etc. Gold standard and accurate techniques, including culturing and qPCR, remain too slow for such applications, and are relatively expensive and complicated to use at the POC/N. We developed a method for detecting genomic pathogenic molecules at the single molecule level, thus eliminating the need to amplify these molecules. The method relies on fluorescent hybridization probes that bind specific genes of interest. Upon target binding, the probes generate a FRET signal that undergoes time-dependent modulation through reversible frustration of the FRET process. Unbound probes and other background components remain unmodulated, and their signal is filtered out in the frequency domain, allowing sensitive signal detection from single probe molecules bound to the target genes. The method is fast (~2min) and accurate (>95% sensitivity and specificity), as demonstrated for STD causing pathogens. The method is also general and can be expanded to additional pathogens and media of interest.

The COVID-19 pandemic has emphasized the inability of diagnostic laboratories' testing capacity to keep up with the surging demand. The primary reasons were the lack of reagents (e.g., viral transport media and nucleic acid extraction kits) and the low throughput of the gold-standard molecular detection method (RT-qPCR). While the reagent shortages were eventually resolved, the limited throughput of the RT-qPCR remains a bottleneck for high-throughput testing applications even today. Here, we introduce a rapid saliva-based extraction-free molecular assay, which utilizes a non-invasive saliva sampling and extraction-free sample preparation, a fast endpoint RT-PCR and a high-throughput optical modulation biosensing (ht-OMBi) detection platform. We blindly tested 364 paired nasopharyngeal swabs and saliva samples from suspected SARS-CoV-2 cases in Israel. Compared with the gold standard swab-based RT-qPCR, the presented assay's sensitivity and specificity are 90.7% and 95.3%, respectively, but is achieved with only 50 min. sample-to-result turnaround time (~60% faster than the regular RT-qPCR), allowing high throughput and considerable savings of the reagents and disposables.

Rapid, highly sensitive, and high-throughput detection of biomarkers at low concentrations is invaluable for the early diagnosis of various diseases. In many sensitive immunoassays, the protocol is time-consuming and requires a complicated and expensive detection system. Previously, we presented a high-throughput optical modulation biosensing (ht-OMB) system, which enables reading a 96-well plate within 10 minutes. In ht-OMB, to aggregate and immobilize the magnetic beads to one spot, a single cylindrical permanent magnet with a sharp tip is positioned under a 96-well plate. To reduce washing and separation steps, the laser beam is manipulated relative to the fixed magnetic beads. Recently, MagBiosense Inc., which commercializes the ht-OMB technology, provided us with a fully automated OMBi detection system. Here, we show the use of the OMBi system for highly sensitive serological (clinical anti-Zika, anti-DENV, and anti-West Nile IgG) and molecular (SARS-CoV-2) assays. Using the OMBi, to detect 336 RNA extracts from 70 confirmed RT-qPCR SARS-CoV-2-positive patients (Ct≤40) and 236 confirmed RT-qPCR SARS-CoV-2-negative individuals, resulted in 100% specificity and 96% sensitivity.

Label-free optical observation of transparent nano-objects is challenging. Here, we demonstrate PlAsmonic NanO-apeRture lAbel-free iMAging (PANORAMA) that addresses existing issues for both SPR and LSPR imaging. PANORAMA involves a standard commercial bright-field microscope without the need for laser or interferometric detection. PANORAMA can image, size, count, and monitor a single polystyrene nanoparticle down to 25 nm at a millisecond timescale. The extrapolated size limit of detection is sub-10 nm. Higher imaging speed is achievable with high-speed cameras. Molecular imaging is envisioned with functionalized substrates for single nanoparticle analysis for extracellular vesicles (e.g., exosomes) and pathogens (e.g., viruses).

Detection, imaging, and quantification of low abundant biomolecules within biological fluids, cells, and tissues is of fundamental importance but remains extremely challenging in biomedical research as well as clinical diagnostics. We have designed and synthesized an ultrabright fluorescent nanoconstruct, termed “plasmonic-fluor”, as an “add-on” bio-label to dramatically improve the signal-to-noise ratio of a wide variety of existing fluorescence bioassays without altering or complicating the conventional assay workflow or read-out devices. We demonstrate that these novel nanoconstructs can be readily utilized in a broad range of bioanalytical methods, including fluorophore-linked immunosorbent assays, multiplexed bead-based immunoassays, lateral flow assays, immuno-microarrays, flow cytometry, and immunocytochemistry, to attain more than 1000-fold improvement in the limit-of-detection and dynamic range. Harnessing plasmonic-fluors, we also demonstrate minimally-invasive and ultrasensitive quantification of target protein biomarkers in interstitial fluid through microneedle-assisted in vivo sampling and subsequent on-needle analysis.