Search Results (391)

The human Tau protein stands for one of the most conspicuous and crucial hallmarks of Alzheimer’s disease (AD) diagnosis, along with other tauopathies. However, the assay for direct detection of tiny Tau protein concentrations in human samples continues to pose a significant challenge for the early diagnosis of AD. Thus, an amplification-based strategy is required. In this proposed work, we established an impedimetric immunosensor to detect human Tau-441 protein in PBS buffer using a sandwich approach, wherein we employed two distinct monoclonal antibodies (HT7 and BT2) that specifically recognize the amino acids 159–198 of the target protein. Through this strategy, we were able to detect as low as 0.08 pg/mL. These findings were attributed to the use of a biotinylated antibody (BT2)-streptavidin complex, which facilitated the amplification of the normalized signal, resulting in a lower limit of detection in comparison to the directly based immunosensors. Subsequently, we investigated the designed immunosensor to assess the assay’s selectivity in the presence of different off-targets, and no cross-interaction was recorded. The outcomes of our study provide valuable new insights into the application of sandwich-based assay as a highly sensitive and selective immunosensor for the detection of small protein. Full article

Background: Cow’s milk allergy (CMA) is the most common food allergy in children, typically resolving by adolescence. In contrast, the clinical spectrum of allergies to non-cow mammalian milk and their patterns of IgE cross-reactivity are less well documented. Nutritional differences between various mammalian milks may also impact dietary management in milk-allergic patients. Objectives: To characterize clinical features, onset age, and IgE cross-reactivity patterns of non-cow mammalian milk allergies in adult patients seen at a tertiary allergy center, and to compare these findings with published cases. Methods: A retrospective analysis of patients included in the “Extended Laboratory Investigation for Rare Causes of Anaphylaxis study” with mammalian milk allergy was performed using clinical history, skin testing, and serum-specific IgE measurements. Cross-reactivity patterns were assessed in selected cases using immunoblotting, specific IgE inhibition, and basophil activation testing, and compared with published reports of non-cow mammalian milk allergy. Results: In our case series of 22 patients with mammalian milk allergy and 10 healthy control subjects, 3 patients were identified with isolated adult-onset non-cow mammalian milk allergy (n = 1 buffalo milk; n = 2 mare milk), confirmed via immunoblotting and basophil activation testing. Streptavidin-based specific IgE measurement for buffalo cheese was positive in the buffalo milk allergic patient. The literature review identified 82 cases of non-cow mammalian milk allergy. These cases typically showed late onset (mean age 8.6 years; range 1–70 years), severe reactions (CoFAR (Consortium for Food Allergy Research) grade 3 or 4 in 66%, and one fatality), and selective sensitization (affecting sheep and/or goat, camel, mare, buffalo, donkey, or combinations thereof in 56, 10, 5, 5, 4, and 2 cases, respectively). Conclusions: Non-cow mammalian milk allergies are rare but generally present later in life with selective IgE cross-reactivity, differing from the broader cross-reactivity observed in CMA. This selectivity may allow for safe dietary alternatives. These findings underscore the need for improved diagnostics and personalized dietary management in this patient population. Full article

Salmonella is a rapidly spreading and widespread zoonotic infectious disease that poses a serious threat to the safety of both poultry and human lives. Therefore, the timely detection of Salmonella in foods and animals has become an urgent need for food safety. This work describes the construction of an aptamer-based sensor for Salmonella detection, using Fe₃O₄ magnetic beads and Ag@Au core–shell nanoparticles-embedded 4-mercaptobenzoic acid (4MBA). Leveraging the high affinity between biotin and streptavidin, aptamers were conjugated to Fe₃O₄ magnetic beads. These beads were then combined with Ag@4MBA@Au nanoparticles functionalized with complementary aptamers through hydrogen bonding and π-π stacking interactions, yielding a SERS-based aptamer sensor with optimized Raman signals from 4MBA. When target bacteria are present, aptamer-conjugated magnetic beads exhibit preferential binding to the bacteria, leading to a decrease in the surface-enhanced Raman scattering (SERS) signal. And it was used for the detection of five different serotypes of Salmonella, respectively, and the results showed that the aptamer sensor exhibited a good linear relationship between the concentration range of 10²–10⁸ CFU/mL and LOD is 35.51 CFU/mL. The SERS aptasensor was utilized for the detection of spiked authentic samples with recoveries between 94.0 and 100.4%, which proved the usability of the method and helped to achieve food safety detection. Full article

Hydrocortisone is a typical glucocorticoid commonly used in livestock production; however, its overuse can result in hormone residues in milk. Long-term consumption of such milk may lead to a series of health issues. Therefore, the timely and rapid detection of hydrocortisone in milk is crucial for protecting human health. In this study, a magnetic particle-based direct chemiluminescence immunoassay (MP-DCLIA) incorporating a streptavidin–biotin signal amplification system was developed for the rapid and high-throughput detection of hydrocortisone in milk. Automated operations reduce human error and enhance the accuracy and repeatability of tests. The assay can be completed in 12 min with a linear detection range of 13.09–261.71 μg/L, a limit of detection (LOD) of 4.94 μg/L, a limit of quantification (LOQ) of 14.84 μg/L, and intra- and inter-batch variations of less than 5%. The method demonstrated stability and exhibited no cross-reactivity with structural analogues. Spiked recoveries of milk samples ranged from 85.85% to 100.30%, with results strongly correlating with those obtained from LC-MS/MS. The MP-DCLIA offers rapidity, high efficiency, stability, and precision, making it a promising tool for practical testing applications. Full article

Hedgehog (HH) signaling plays important roles in the development of the nervous system (Sonic hedgehog), bone, cartilage (Indian Hedgehog) and testis (Desert Hedgehog). Research on HH and testes has mostly been conducted in HH-knockout mice and rats, etc. The relationship between HH and cellular junctions has mostly been found in the nervous system and intestine. However, few research studies concerning the link between HH signaling and cell junctions in testis function have been reported. We identified the members of HH signaling that are involved in Eriocheir sinensis testes: HH, Smoothen, Patched, Kif27 and Ci. HH has only one homolog in E. sinensis and is expressed in several types of germ cells in the testes. We found that Kif27 colocalized with Ci in the testes. The knockdown of HH induced enlarged interstitial spaces of the seminiferous tubules. A biotin–streptavidin immunofluorescence experiment indicated that the hemolymph–testis barrier (HTB) was disrupted. Western blot results showed that pinin, HH signaling and cell proliferation- and apoptosis-related protein levels were downregulated. Further immunofluorescent results showed the dislocation of several junction proteins, the abnormality of F-actin and the slowdown of germ cell proliferation and apoptosis. While β-catenin entered the spermatocyte nucleus, it did not activate Wnt-β-catenin signaling, which indicated that the disturbance of the cell cycle in germ cells was not caused by Wnt-β-catenin signaling. In summary, HH signaling plays some roles beyond our understanding in the regulation of the HTB and the germ cell cycle in E. sinensis testes. Full article

The assurance of food safety requires sensitive monitoring of multiple mycotoxins due to their severe impacts on the food industry and high health risks posed to consumers. Herein, we proposed a chemiluminescent/colorimetric dual-signal readout microfluidic method, incorporating a streptavidin-biotin-alkaline phosphatase (SA-Biotin-ALP) signal amplification system for the highly sensitive detection of Deoxynivalenol (DON), Ochratoxin A (OTA), and Aflatoxin B1 (AFB1). The indirect competitive enzyme-linked immunoassay (ic-ELISA) was integrated into microfluidic chip, resulting in sensitive detection ranges of DON in the range of 4–128 ng/mL, 2–64 ng/mL for OTA, and 0.2–6.4 ng/mL for AFB1, with the limit of detection (LOD) being 2.636 ng/mL, 1.492 ng/mL, and 0.131 ng/mL, respectively. Recovery rates in beer samples ranged from 91.93% to 109.31%. Furthermore, a dual-mode microfluidic workstation (DMMW) was developed to facilitate rapid, automated detection for these mycotoxins, simplifying the detection procedure, enhancing the detection efficiency, and reducing the requirement for specialized personnel, thus confirming significant potential for the rapid detection of mycotoxins in complex matrices such as beer. Full article

The rapid and accurate detection of foodborne pathogens is essential for ensuring food safety. Escherichia coli O157:H7 (E. coli O157:H7) and Salmonella Typhimurium (S. Typhimurium) are major foodborne pathogenic bacteria that pose significant public health risks, highlighting the need for effective detection methods. In this study, highly sensitive double-antibody sandwich-based enzyme-linked immunosorbent assays (ELISAs) were developed for the rapid detection of E. coli O157:H7 and S. Typhimurium, utilizing a streptavidin-polymerized horseradish peroxidase (SA-PolyHRP)-based signal enhancement system. Systematic optimization was performed on key parameters, including the capture antibody concentration, detection antibody, and blocking agent. Compared to the method using SA-HRP, substitution with SA-PolyHRP significantly improved detection sensitivity, achieving limits of detection (LODs) of 1.4 × 10⁴ CFU/mL for E. coli O157:H7 and 6.0 × 10³ CFU/mL for S. Typhimurium, with sensitivity enhancements of 7.86-fold and 1.83-fold, respectively. Specificity tests confirmed no cross-reactivity with non-target or closely related pathogenic strains. The matrix effect was effectively mitigated through 10-fold and 100-fold dilutions for E. coli O157:H7 and S. Typhimurium, respectively. Both pathogens were successfully detected in beef samples spiked with 5 CFU after 5 h of incubation. This study demonstrates the effectiveness of PolyHRP-based signal enhancement for the highly sensitive and specific detection of foodborne pathogens, offering a promising approach for rapid food safety monitoring and public health protection. Full article

Aflatoxin M1 (AFM1) appears in the milk of animals that have consumed feed contaminated with aflatoxin B1. AFM1 presence in milk is regulated by the European Commission, which has set the maximum allowable limits for adult and infant consumption to 50 and 25 pg/mL, respectively. Here, a rapid and sensitive method for detecting AFM1 in milk based on an immersible silicon photonic chip is presented. The chip features two U-shaped silicon nitride waveguides formed as Mach–Zehnder interferometers. One interferometer is functionalized with AFM1–bovine serum albumin conjugate and the other with BSA to serve as a blank. The chip is connected to a broad-band white LED and a spectrophotometer by a bifurcated optical fiber and an assay is performed by immersing the chip in a mixture of milk with the anti-AFM1 antibody. Then, the chip is sequentially immersed in biotinylated anti-rabbit IgG antibody and streptavidin solutions for signal enhancement. The assay is completed in 20 min and the detection limit for AFM1 in undiluted milk is 20 pg/mL. Given its analytical performance and the absence of pumps and fluidics that lead to a compact instrument design, the proposed immunosensor is ideal for the on-site detection of AFM1 in milk samples. Full article

3D-printed microdevices have become increasingly important to the advancement of point-of-care (POC) immunoassays. Despite its great potential, using 3D-printed surfaces on the solid support for immunorecognition has been limited due to the non-ideal adsorption properties for many photocurable resins. In this work, we report a simple surface modification protocol that works for diverse commercial photocurable resins, improving ELISAs performed directly on 3D-printed devices. This surface modification strategy involves surface activation via air plasma followed by the one-step incubation of GLYMO-labeled streptavidin. We successfully immobilized biotinylated anti-activin A antibodies on the 3D-printed surfaces and performed the complete ELISA protocol on the 3D-printed surfaces. We demonstrated that this protocol achieved an improved performance over passive adsorption for ELISAs. The present method is also compatible with diverse commercial resins and works with both microwells and microchannels. Finally, this method demonstrated a comparable limit of detection to the ELISA performed using commercial microwells. We believe the simplicity and broad compatibility of the present surface modification strategy will facilitate the development of 3D-printed POC ELISA devices. Full article

Quantitative nucleic acid detection is widely used in molecular diagnostics for infectious diseases. Here, we demonstrate that the previously developed MLFIA (magnetically localized fluorescent immunoassay) has the potential to detect Polymerase Chain Reaction (PCR) and loop-mediated isothermal amplification (LAMP) products using biotinylated and fluorescent primers and streptavidin-coated magnetic nanoparticles. The functionalized nanoparticles separate amplified DNA from non-incorporated primers in situ, allowing the quantification of DNA products. We compare magnetically localized fluorescence detection to commercial technologies based on the DNA intercalation of fluorescent dyes. Our system allows the detection of PCR and LAMP products but is approximately 10 times less sensitive than standard commercial assays. Future optimizations, such as enhancing the signal-to-noise ratio and improving nanoparticle functionalization, could significantly increase sensitivity and bring it closer to current diagnostic standards. This work highlights the potential of magnetically localized fluorescence detection to detect DNA. Full article

The quantitative analysis of nucleic acid markers is extensively utilized in cancer detection. However, it faces significant challenges, such as the need for specialized detection devices and the inherent complexity of testing procedures. To address these issues, this study proposes a simplified, rapid, and user-friendly platform for cancer nucleic acid marker detection. We firstly designed a polydimethylsiloxane (PDMS) device for the isothermal amplification reaction of nucleic acid biomarkers based on reverse-transcription recombinase-aided amplification (RT-RAA) technology. Specifically, three potential cancer nucleic acid biomarkers, carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), and prostate cancer antigen 3 (PCA3) were amplified from human serum or urine samples in the PDMS device at body temperature. The reaction chamber was directly integrated with nucleic acid test strips labeled with colloidal gold nanoparticles, allowing for the visual observation of the detection results for the amplification products. The optimal reaction conditions, such as pH, reaction time, antibody, and streptavidin concentration, were defined after a series of optimization studies. The findings demonstrated that the optimal RT-RAA reaction time was 20 min, the primary antibodies were labeled with colloidal gold to the greatest extent at pH 8.5, and the optimal concentrations of secondary antibody and streptavidin were 1.0 mg/mL and 0.5 mg/mL, respectively. Furthermore, this novel detection approach could not only exhibit excellent sensitivity and specificity but also show high accuracy for the analysis of nucleic acid biomarkers in both clinical serum and urine samples. Therefore, the simplified and more convenient operation platform provides a new insight for the semi-quantitative analysis of cancer nucleic acid biomarkers and the rapid screening of early cancer, thereby offering a promising alternative to oncological point-of-care testing (POCT) diagnostics. Full article

In this study, we developed a low-cost, high-sensitivity chemiluminescence competitive aptamer sensor for the detection of aflatoxin B₁ (AFB₁) in wheat samples. The optical fiber sensor was self-made, and it utilized biotin and streptavidin (SA) link aptamer and horseradish peroxidase (HRP) for the chemiluminescence detection, achieving competitive assay between the AFB₁ and AFB₁ antigen. We adjusted the experimental conditions of the sensor base on the date of optimization of the experimental conditions and chose coated antigens on the surface of carboxyl magnetic particles. Under conditions optimized by testing key parameters, the assay results showed that the chemiluminescence intensity and AFB₁ concentration demonstrated a strong linear relationship (R² = 0.995), the dynamic range was from 0.1 to 10 ng/mL with a detection limit of 0.09 ng/mL, and the aptamer exhibited good specificity and anti-interference ability. Testing the wheat samples showed that the spiked recovery rate ranged from 79.19% to 113.21%. The sensor possesses characteristics of low detection limits, simple manufacturing methods, and affordability, providing a novel solution for the development of low-cost and high-sensitivity AFB₁ detection equipment. Full article

Rapidly growing industrial biotechnology and bio-manufacturing require simple and cost-effective bioseparation tools. A novel strategy of bioseparation based on the streptavidin-decorated polyhydroxyalkanoate (PHA) nano-granules was developed in this study. By fusing to the N-terminus of PHA-associated phasin protein, the streptavidin was one-step immobilized on the surface of PHA nano-granules simultaneously with the accumulation of PHA in recombinant Escherichia coli. About 1.95 g/L of PHA nano-granules (54.51 wt% of cell dry weight) were produced after 48 h bacterial cultivation. The following qualitative and quantitative characterizations demonstrated that the streptavidin accounted for approximately 6.78% of the total weight of the purified PHA nano-granules and confirmed a considerable biotin affinity of 0.1 ng biotin/μg surface protein. As a proof of concept, the nano-granules were further functionalized with biotinylated oligo(dT) for mRNA isolation and about 1.26 μg of mRNA (occupied 2.59%) was purified from 48.45 μg of total RNA, achieving good integrity and high purity with few DNA and rRNA contaminations. Moreover, the nano-granules retained more than 80% of their initial mRNA recovery efficiency after ten cycles of repeated use. The PHA-SAP nano-granules were also functionalized with biotinylated magnetic beads, allowing magnetic recovery of the PHA nano-granules from cell lysates that still needs optimization. Our study provides a novel and expandable platform of PHA nano-granules that can be further functionalized with various biological groups for bioseparation applications. The functional PHA nano-granules have a great potential to serve as bioseparation resin for large-scale purification processes after suitable optimizations for “bench-to-factory” translation, contributing to scalable and sustainable bioprocessing. Full article

Due to cyanobacterial toxin (cyanotoxin) contamination issues in 2018, the city of Salem, Oregon, issued a 33-day do-not-drink advisory for vulnerable people among the 200,000 residents. After the incident, the state of Oregon put in place drinking water rules to require the routine testing of raw water, as well as finished water, in cases where the raw water cyanotoxin concentrations exceeded trigger values. The United States Environmental Protection Agency (EPA) total microcystins drinking water health advisory level (HAL) for small children is 0.3 µg/L. This is equivalent to the minimum reporting level (MRL) for EPA Method 546. Consequently, there was no ability to provide early warnings via toxin testing for total microcystins using the EPA method. In this study, we performed a comparison of the precision and accuracy of the enzyme-linked immunosorbent assay (ELISA) described in the EPA method to a more sensitive assay, the Streptavidin-enhanced Sensitivity (SAES) assay. Based on these precision and accuracy studies and quantitation limit determinations and confirmations, the EPA Office of Ground Water and Drinking Water (OGWDW) has concluded the SAES kit meets the requirements of EPA Method 546. With an MRL that is one-third of the original concentration, the new kit provides a small but critical window for identifying early warnings. Challenges remain with providing early warnings due to the variability in bloom dynamics; however, the new MRL allowed Oregon to lower the trigger level for susceptible systems, thereby providing an additional early warning. Full article

The association between microRNAs and various diseases, especially cancer, has been established in recent years, indicating that miRNAs can potentially serve as biomarkers for these diseases. Determining miRNA concentrations in biological samples is crucial for disease diagnosis. Nevertheless, the stem-loop reverse transcription quantitative PCR method, the gold standard for detecting miRNA, has great challenges in terms of high costs and enzyme limitations when applied to clinical biological samples. In this study, an isothermal signal amplification method based on a duplex-specific nuclease (DSN) enzyme-driven DNA walker and an improved catalytic hairpin assembly (CHA) was designed for miRNA detection. First, biotin–triethylene glycol-modified trigger-releasable DNA probes were conjugated to the streptavidin-coated magnetic beads for recognizing the target miRNA. The DSN enzyme specifically hydrolyzes DNA strands when the DNA probe hybridizes with the targeted miRNA. This recycling process converts the input miRNA into short trigger fragments (catalysts). Finally, three hairpins of improved CHA are driven by this catalyst, resulting in the three-armed CHA products and a fluorescence signal as the output. This dual-cycle biosensor shows a good linear relationship in the detection of miR-21 and miR-141 over the final concentration range of 250 fM to 50 nM, presenting an excellent limit of detection (2.95 amol). This system was used to detect miR-21 and miR-141 in MCF-7 and 22RV1 cells, as well as in 1% human serum. This system can be used to evaluate the expression levels of miRNAs in different biological matrices for the clinical diagnosis and prognosis of different cancers. Full article