Quantitative assessment of disease markers using the naked eye: point-of-care testing with gas generation-based biosensor immunochromatographic strips

Pt@AuNF nanozyme and horseradish peroxidase-based lateral flow immunoassay dual enzymes signal amplification strategy for sensitive detection of zearalenone

Lateral flow immunoassay (LFIA) has been employed extensively for the rapid, accurate, and portable detection of foodborne toxins. Here, the platinum gold nanoflower core-shell (Pt@AuNF) nanozyme with excellent optical properties, good catalytic ability and controllable reaction conditions were prepared to effectively improve the performance of lateral flow immunoassay (LFIA) strips. The Pt@AuNF nanozyme and horseradish peroxidase (HRP) combined with monoclonal antibody were used as signal probes based on the dual enzymes catalytic signal amplification strategy to detect Zearalenone sensitively. Dual enzymes catalyze the decomposition of hydrogen peroxide into hydroxyl radicals, and under the influence of hydroxyl radicals, colorless 3,3',5,5' -tetramethylbenzidine (TMB) is oxidized to blue ox-TMB, which is superimposed on the strips for signal amplification to broaden the detection range. The limit of detection (LOD) of the Pt@AuNF-HRP labeled LFIA strips after signal amplification was 0.052 ng/mL, and the detection range was 0.052-7.21 ng/mL. Compared with the Pt@AuNF labeled strips, while reducing the probes amount by half to achieve antibody conservation, the detection range was expanded by 5-fold based on achieving improved sensitivity. The study provided a meaningful reference for expanding the detection range based on immunoassay.

AuPt nanoalloy with dual functionalities for sensitive detection of HPV16 DNA

Human papillomavirus type 16 (HPV16), one of the high-risk types, is responsible for 53% of cervical cancers. The development of an early diagnostic approach with high sensitivity, low-cost, point-of-care testing (POCT) for HPV16 is urgent. In our work, a novel dual-functional AuPt nanoalloy-based lateral flow nucleic acid biosensor (AuPt nanoalloy-based LFNAB) was established with excellent sensitivity for detecting HPV16 DNA for the first time. The AuPt nanoalloy particles were prepared by a one-step reduction method, which was simple, rapid, and green. The AuPt nanoalloy particles retained the performance of initial Au nanoparticles owing to the catalytic activity enabled by Pt. Such dual-functionalities offered two kinds of detection alternatives (i.e., normal mode and amplification mode, respectively). The former is produced just by the black color from the AuPt nanoalloy material itself, and the latter is more color sensitive from its superior catalytic activity. The optimized AuPt nanoalloy-based LFNAB exhibited satisfactory quantitative ability in detecting the target HPV16 DNA in the range of 5-200 pM with a LOD of 0.8 pM at the "amplification mode". The proposed dual-functional AuPt nanoalloy-based LFNAB displayed great potential and promising opportunity in POCT clinical diagnostics.

Highly sensitive and portable mRNA detection platform for early cancer detection

Pancreatic cancer, at unresectable advanced stages, presents poor prognoses, which could be prevented by early pancreatic cancer diagnosis methods. Recently, a promising early-stage pancreatic cancer biomarker, extracellular vesicles (EVs) related glypican-1 (GPC1) mRNA, is found to overexpress in pancreatic cancer cells. Current mRNA detection methods usually require expensive machinery, strict preservation environments, and time-consuming processes to guarantee detection sensitivity, specificity, and stability. Herein, we propose a novel two-step amplification method (CHAGE) via the target triggered Catalytic Hairpin Assembly strategy combined with Gold-Enhanced point-of-care-testing (POCT) technology for sensitive visual detection of pancreatic cancer biomarker. First, utilizing the catalyzed hairpin DNA circuit, low expression of the GPC1 mRNA was changed into amplification product 1 (AP1, a DNA duplex) as the next detection targets of the paper strips. Second, the AP1 was loaded onto a lateral flow assay and captured with the gold signal nanoparticles to visualize results. Finally, the detected results can be further enhanced by depositing gold to re-enlarge the sizes of gold nanoparticles in detection zones. As a result, the CHAGE methodology lowers the detection limit of mRNA to 100 fM and provides results within 2 h at 37 °C. Furthermore, we demonstrate the successful application in discriminating pancreatic cancer cells by analyzing EVs' GPC1 mRNA expression levels. Hence, the CHAGE methodology proposed here provides a rapid and convenient POCT platform for sensitive detection of mRNAs through unique probes designs (COVID, HPV, etc.).

A Sensitive, Point-of-Care Detection of Small Molecules Based on a Portable Barometer: Aflatoxins In Agricultural Products

Sensitive and point-of-care detection of small toxic molecules plays a key role in food safety. Aflatoxin, a typical small toxic molecule, can cause serious healthcare and economic issues, thereby promoting the development of sensitive and point-of-care detection. Although ELISA is one of the official detection methods, it cannot fill the gap between sensitivity and point-of-care application because it requires a large-scale microplate reader. To employ portable readers in food safety, Pt-catalysis has attracted increasing attention due to its portability and reliability. In this study, we developed a sensitive point-of-care aflatoxin detection (POCAD) method via a portable handheld barometer. We synthesized and characterized Au@PtNPs and Au@PtNPs conjugated with a second antibody (Au@PtNPs-IgG). A competitive immunoassay was established based on the homemade monoclonal antibody against aflatoxins. Au@PtNPs-IgG was used to catalyze the production of O₂ from H₂O₂ in a sealed vessel. The pressure of O₂ was then recorded by a handheld barometer. The aflatoxin concentration was inversely proportional to the pressure recorded via the barometer reading. After optimization, a limit of detection of 0.03 ng/mL and a linear range from 0.09 to 16.0 ng/mL were achieved. Recovery was recorded as 83.1%–112.0% along with satisfactory results regarding inner- and inter-assay precision (relative standard deviation, RSD < 6.4%). Little cross-reaction was observed. Additionally, the POCAD was validated by high-performance liquid chromatography (HPLC) by using peanut and corn samples. The portable POCAD exhibits strong potential for applications in the on-site detection of small toxic molecules to ensure food safety.

Biosensors for detecting viral and bacterial infections using host biomarkers: a review

A schematic diagram showing multiple modes of biosensing platforms for the diagnosis of bacterial or viral infections.