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Simplified Sample Preparation and Lateral Flow Immunoassay for the Detection of Plant Viruses
(2026)
Lateral flow immunoassays (LFAs) are widely used for on-site testing; however, their use for the rapid detection of plant viruses in the field is often limited by inconvenient sample preparation. Here, we present a new sampling method and a simplified dipstick LFA format for the detection and monitoring of cowpea chlorotic mottle virus (CCMV) as a model plant pathogen. The assay employs a monoclonal mouse antibody for capture and a poly-clonal rabbit antibody conjugated to 80 nm gold nanoparticles for detection. Conventional sample and conjugate pads are omitted, allowing the test strips to be dipped directly into wells containing plant extract and antibody–gold conjugate. No plastic casing was required, which could lead to a reduction in waste. It was shown that CCMV concentrations as low as 3.5 µg/L or 350 pg per sample could be reliably detected in 15 min. Specificity tests confirmed that other plant viruses, cowpea mosaic virus (CPMV) and tobacco mosaic virus (TMV), did not produce false-positive results. In addition, we describe a new method for on-site sampling using a manual punch and a syringe equipped with a frit. This step combines grinding the sample, extraction, filtration, and reconstitution and mixing of the antibody-gold conjugate, enabling the analysis of punched leaf disks without laboratory equipment. When applied to CCMV-infected cowpea plants, the assay revealed systemic infection before visual symptoms became apparent. This work demonstrates that simplified LFAs combined with innovative sampling techniques can provide sensitive, specific, and rapid diagnostics for crop monitoring and support early intervention strategies in agriculture.
Kardiosprint: Detektion des Herzinfarktmarkers Troponin-I durch photonische Biosensoren (Kapri)
(2026)
Ziel des Projekts war die Entwicklung eines miniaturisierten, siliziumbasierten photonischen Biosensors zur schnellen, empfindlichen und kostengünstigen Detektion klinisch relevanter Herzmarker direkt am Patienten (Point-of-Care). Im Fokus standen zwei Biomarker: das kardiale Troponin I (cTnI) als hochspezifischer Akutmarker des Herzinfarkts sowie das C-reaktive Protein (CRP) als prognostischer Entzündungs- und Risikomarker für Herz-Kreislauf-Erkrankungen. Eine schnelle, quantitative und ortsnahe Messung dieser Marker kann die Diagnose beschleunigen und Behandlungsentscheidungen verbessern.
Im Projektverlauf wurden die wesentlichen Bausteine einer solchen Plattform erarbeitet und erstmals zusammengeführt: Die Etablierung von Referenzassays (ELISA) als Vergleichsmaßstab, die Entwicklung der Oberflächenchemie für die Sensorchips, ein kontaktloses Druckverfahren zur präzisen Beschichtung der winzigen Sensorstrukturen sowie erste funktionale Messungen am photonischen Biosensor. Als zentrale Ergebnisse konnten die spezifische Detektion eines Proteins in Echtzeit, die gleichzeitige Mehrkanal-Messung über mehrere Sensoren sowie ein erster Nachweis des Biomarkers CRP am Chip demonstriert werden. Der Transfer auf den anspruchsvolleren Marker Troponin I sowie die Bestimmung belastbarer Nachweisgrenzen bleiben offene, gezielt zu bearbeitende Punkte.
Simplified Sample Preparation and Lateral Flow Immunoassay for the Detection of Plant Viruses
(2025)
Lateral flow immunoassays (LFA) are widely used for decentralized testing, but their application for in-field plant virus diagnostics is often limited by tedious sample preparation. Here, we present a simplified dipstick LFA for the detection and monitoring of cowpea chlorotic mottle virus (CCMV) as a model plant pathogen. The assay employes a monoclonal mouse antibody for capture and a polyclonal rabbit antibody conjugated to 80-nm gold nanoparticles for detection. Conventional sample and conjugate pads are omitted, allowing the test strips to be dipped directly into wells containing plant extract and antibody-gold conjugate. In addition, no plastic casing was necessary, which significantly reduces waste. It was shown that CCMV concentrations as low as 4 μg/L or 400 pg per sample could be reliably detected in 15 minutes. Specificity tests confirmed that other plant viruses, cowpea mosaic virus (CPMV) and tobacco mosaic virus (TMV), did not produce false positive results. Furthermore, we describe a field-compatible sampling procedure using a manual punch and a disposable syringe. This step combines sample grinding, extraction, and conjugate reconstitution within the syringe frit, enabling the analysis of punched leaf discs without laboratory equipment. When applied to CCMV-infected cowpea plants, the assay revealed systemic infection before visual symptoms became apparent. This work demonstrates that simplified LFAs combined with innovative sampling techniques can provide sensitive, specific, and rapid diagnostics for crop monitoring and support early intervention strategies in agriculture.
Cardiac troponin I (cTnI) is a crucial biomarker for diagnosing cardiac vascular diseases, including acute myocardial infarction (AMI). This study presents a proof-of-concept chemiluminescence-based immunosensor for rapid and accurate measurement of cTnI, with the potential for online monitoring. The immunosensor incorporates a flow cell design and a sensitive complementary metal-oxide-semiconductor (CMOS) camera for optical readout. A microfluidic setup was established to enable selective and quasi-online determination of cTnI within ten minutes. The sensor was tested with recombinant cTnI in phosphate buffer, demonstrating measurements in the concentration range of 2–25 µg/L, with a limit of detection (LoD) of 0.6 µg/L (23 pmol/L) achieved using the optimized system. The immunosensor exhibited high selectivity, as no cross-reactivity was observed with other recombinant proteins such as cTnT and cTnC at a concentration of 16 µg/L. Measurements with diluted blood plasma and serum yielded an LoD of 60 µg/L (2.4 nmol/L) and 70 µg/L (2.9 nmol/L), respectively. This biosensor offers a promising approach for the rapid and sensitive detection of cTnI, contributing to the diagnosis and management of acute myocardial infarction and other cardiac vascular diseases.
The trafficking of illegal drugs by criminal networks at borders, harbors, or airports is an increasing issue for public health as these routes ensure the main supply of illegal drugs. The prevention of drug smuggling, including the installation of scanners and other analytical devices to detect small traces of drugs within a reasonable time frame, remains a challenge. The presented immunosensor is based on a monolithic affinity column with a large excess of immobilized hapten, which traps fluorescently labeled antibodies as long as the analyte cocaine is absent. In the presence of the drug, some binding sites of the antibody will be blocked, which leads to an immediate breakthrough of the labeled protein, detectable by highly sensitive laser-induced fluorescence with the help of a Peltier-cooled complementary metal-oxide-semiconductor (CMOS) camera. Liquid handling is performed with high-precision syringe pumps and microfluidic chip-based mixing devices and flow cells. The biosensor achieved limits of detection of 7 ppt (23 pM) of cocaine with a response time of 90 s and a total assay time below 3 min. With surface wipe sampling, the biosensor was able to detect 300 pg of cocaine. This immunosensor belongs to the most sensitive and fastest detectors for cocaine and offers near-continuous analyte measurement.
The trafficking of illegal drugs by criminal networks at borders, harbors, or airports is an increasing issue in public health as these routes ensure the main supply of illegal drugs. The prevention of drug smuggling, including the installation of scanners and other analytical devices to detect ultra-small traces of drugs within a reasonable time frame, remains a challenge. The presented immunosensor is based on a monolithic affinity column with a large excess of immobilized hapten, which traps fluorescently labeled antibodies as long as the analyte cocaine is absent. In the presence of the drug, some binding sites of the antibody will be blocked, which leads to an immediate breakthrough of the labeled protein, detectable by highly sensitive laser-induced fluorescence with the help of a Peltier-cooled complementary metal-oxide-semiconductor (CMOS) camera. Liquid handling is performed with high-precision syringe pumps and microfluidic chip-based mixing devices and flow cells. The biosensor achieved limits of detection of 23 pM (7 ppt) of cocaine with a response time of 90 seconds and a total assay time below 3 minutes. With surface wipe sampling, the biosensor was able to detect 300 pg of cocaine. This immunosensor belongs to the most sensitive and fastest detectors for cocaine and offers near-continuous analyte measurement.
Cardiovascular diseases are the number one cause of death worldwide and responsible for 3.9 million deaths in Europe and over 1.8 million deaths in the European Union (2017) [1]. Cardiac Troponin I (cTnI) is part of a triple protein complex and the most important biomarker for acute events such as heart attacks. Once a heart attack occurs, the blood stream within the heart is interrupted and further oxygen supply cannot be maintained. As a result, heart cells undergo apoptosis and their proteins will be released into the blood stream. Within the project CardioMet of the European Metrology Program of Research and Innovation (EMPIR) a biosensor for online-monitoring of acute myocardial infarction by detecting cTnI is being developed.
The development of novel photonic microchips is a promising approach to advance the detection of biomarkers through multichannel real-time analysis. This study reports the successful development of a backside released CMOS chip designed for the multichannel real-time detection of biomarkers. Operating at a wavelength of 1550 nm, the microchip features three detection channels in addition to a reference channel, enabling simultaneous analysis of multiple biomarkers.
The microchip incorporates micro-ring resonators that are directly functionalized with specific bioreceptors, which significantly improves the affinity towards target biomarkers. The employed surface functionalization strategy enables versatile immobilization of receptor molecules and serves as a starting point for various analytical applications.
A tunable laser is utilized as the excitation source, providing precise wavelength tuning and stable optical output, essential for achieving optimal resonance conditions within the micro-ring resonators. Our chips use integrated multi-mode interferometers as beam-splitter, grating coupler and Ge-photodiodes, resulting in an ultra-small footprint. The complete chip including metal pads has an area of 1 mm2.
The results indicate that the developed multichannel photonic microchip system enables online detection of multiple biomarkers. The compact and highly miniaturized design of this microchip positions them as promising candidates for point-of-care diagnostics and personalized medicine applications. With further advancements, this technology opens a path to transform biomarker detection across various medical fields, offering rapid, reliable, and cost-effective diagnostic solutions. In conclusion, the presented multichannel photonic microchips signify a substantial leap forward in real-time biomarker detection, providing a robust platform for future research and clinical applications.
Photonic micro-ring resonators (MRR) are widely studied for their high sensitivity across applications like environmental monitoring, healthcare, and chemical analysis. Their evanescent field sensing requires partially unembedded waveguides compatible with CMOS processing. Our approach uses local backside etching with an additional buried oxide (BOX) etch to release waveguides while preserving the back-end of line (BEOL) structure, enabling spatial separation of the sensing area and electronics. The BOX etch critically affects sensor performance, as waveguide surface roughness can alter MRR properties and coupling. We analyzed MRR design variations, comparing wet and dry etching techniques for their effects on optical performance across rib and strip waveguides in quasi-TE and quasi-TM modes. Wafer-level measurements show that backside-released MRR achieve high extinction ratios with slightly reduced quality factors, advancing high-sensitivity photonic sensors.
Photonic micro-ring resonators (MRR) are widely studied for their high sensitivity across applications like environmental monitoring, healthcare, and chemical analysis. Their evanescent field sensing requires partially unembedded waveguides compatible with CMOS processing. Our approach uses local backside etching with an additional buried oxide (BOX) etch to release waveguides while preserving the back-end of line (BEOL) structure, enabling spatial separation of the sensing area and electronics. The BOX etch critically affects sensor performance, as waveguide surface roughness can alter MRR properties and coupling. We analyzed MRR design variations, comparing wet and dry etching techniques for their effects on optical performance across rib and strip waveguides in quasi-TE and quasi-TM modes. Wafer-level measurements show that backside-released MRR achieve high extinction ratios with slightly reduced quality factors, advancing high-sensitivity photonic sensors.
