Xiping Cui

Human papillomavirus (HPV) types 16 and 18 are major causes of cervical cancer, with their E6 oncogenes serving as key biomarkers for early diagnosis. Traditional molecular detection methods, such as PCR, are commonly used but still have limitations, including false positives and complex procedures. To address these challenges, we developed an amplification-free sandwich direct enzyme-linked immunoassay (sELISA). This assay combined the S9.6 antibody’s specificity for DNA-RNA hybrids with streptavidin-polymeric horseradish peroxidase (SA-polyHRP) for signal enhancement. The SA-polyHRP direct sELISA achieved a detection limit of 1.03 pM (0.012 pg/µL), demonstrating 59.6-fold higher sensitivity than the indirect sELISA using SA-coated plates with HRP-labeled secondary antibody (monomeric HRP) for tracer. The integral evaluation of immunoassays containing specificity, affinity, and robustness was accomplished by assessing selectivity for nucleic acid structure, length, GC content variations, and subtypes, respectively. Additionally, the assay was successfully applied to artificial plasma samples, showing acceptable recovery rates (76–108%) at various dilutions and further validating its potential for clinical diagnostics. Overall, this assay using the SA-polyHRP-based direct sELISA provided a rapid, highly specific, and sensitive diagnostic tool for the detection of HPV-related cancers, which will offer significant improvements in diagnostic accuracy, screening, and monitoring. Graphical abstract

As a neglected member of the platinum group elements, osmium, the metal with the highest density in the earth, is very suitable for the preparation of a peroxidase with high catalytic activity and stability, and can also be associated with the development of a sensor. In this study, we accessed Os nano-hydrangeas (OsNHs) with one-pot synthesis and utilized them in a bifunctional immunosensor that can present both catalytic chromogenic and tinctorial signal for nanozyme-linked immunosorbent assay (NLISA) and lateral flow immunoassay (LFIA) for use in folic acid (FA) detection. In the OsNHs-NLISA, the linear range is from 9.42 to 167.53 ng mL⁻¹. The limit of detection (LOD) is 4.03 ng mL⁻¹ and the IC₅₀ value is 39.73 ng mL⁻¹. In OsNHs-LFIA, the visual cut-off value and limit of detection (v-LOD) are 100 ng mL⁻¹ and 0.01 ng mL⁻¹, respectively. Additionally, the outcome from the specificity and spiked sample analysis offered recovery from the spiked milk powder sample ranging from 93.9 to 103.6% with a coefficient of variation under 4.9%, compared with UPLC-MS/MS for a correlation of R² = 0.999 and admirable validation. The promising application of the OsNHs can also be used in other bioprobes, and this bifunctional immunosensor analysis mode is suitable for diversified analytes.

In this paper, five fluorescein-labeled dehydroepiandrosterone (DHEA) derivatives (tracers) with different chain lengths between the fluorescein and hapten were synthesized and featured so as to establish a fluorescence polarization immunoassay (FPIA) for DHEA detection in human urine samples with previously prepared polyclonal antibody against DHEA. The outcomes of the structure of tracer on FPIA sensitivity were investigated. Under the optimal condition, the fluorescence polarization value (FP) decreases linearly in DHEA concentration, ranging from 1.6 to 243.3 ng mL⁻¹, with the limit of detection of 1.1 ng mL⁻¹ and IC₅₀ value of 25.1 ng mL⁻¹. Moreover, the developed FPIA was time-saving as it could complete the detection within 3 min. FPIA and commercial enzyme-linked immunosorbent assay kit were both applied to analyze the spiked human urine samples with DHEA. Excellent recoveries (92.1–108.0%) and satisfactory correlation coefficient (R² = 0.98) were acquired with the two methods, indicating that the developed FPIA was a fast and efficient screening immunoassay with accuracy and sensitivity for DHEA detection in human urine samples. Graphical abstract

A highly sensitive electrochemical biosensor employing tetrahedral DNA nanostructure and signal amplification strategies have been constructed, and this method could be used as a universal platform for trace microRNA detection.

The traditional gold-nanoparticle-based lateral flow immunoassay (LFIA) cannot satisfy the requirements for the sensitive detection of dehydroepiandrosterone (DHEA) in human urine. To enhance the sensitivity of the LFIA, platinum–iridium nanocubes (Pt–Ir NCs) with high catalytic efficiency and stability were synthesized and labelled with polyclonal antibody (pAb) to form a pAb–Pt–Ir probe. For the detection of DHEA, a novel LFIA with Pt–Ir NCs as an optical label and an enhanced LFIA in which the peroxidase-like activity of the Pt–Ir NCs was triggered by the introduction of the chromogenic substrate 3-amino-9-ethyl-carbazole (AEC) were developed and compared with a LFIA with platinum nanocubes (PtNCs) as an optical label. The visual limit of detection was 0.5 ng mL⁻¹ for Pt–Ir-LFIA and 0.05 ng mL⁻¹ for AEC-enhanced Pt–Ir-LFIA, in comparison to 100 ng mL⁻¹ for PtNCs-LFIA and 50 ng mL⁻¹ for AEC-enhanced PtNCs-LFIA. The average recoveries from spiked urine samples ranged from 90.8% to 110.4%, with a coefficient of variation below 12.6%, suggesting the accuracy and reliability of our developed immunoassay. Achieving excellent sensitivity, specificity, and reproducibility, Pt–Ir-LFIA provided a promising platform for monitoring DHEA.

A highly sensitive colorimetric sensing strategy based on enzyme@metal-organic framework (GAA@Cu-MOF) and IrO₂/MnO₂ nanocomposite was exploited innovatively for screening of α-glucosidase (GAA) inhibitors. IrO₂/MnO₂ nanocomposite exhibits excellent oxidase-mimicking activity which can directly catalyze the oxidation of 3,3^,5,5^,-tetramethylbenzidine (TMB) into a blue product with an absorption maximum at 652 nm. And GAA@Cu-MOF can decompose L-ascorbic acid-2-O-α-D-glucopyranosyl (AAG) to ascorbic acid (AA). The produced AA can destroy the IrO₂/MnO₂ nanocomposite and reduce its oxidase-like activity. However, the generation of AA is restricted when GAA inhibitors are added to the system, which allows the oxidase-like activity of the IrO₂/MnO₂ nanocomposite to be maintained. In view of this, a method for screening of GAA inhibitors was developed. In addition to enhancing the stability of GAA, the method can also effectively avoid the potential interference of H₂O₂ in the screening process of GAA inhibitors, which helps to improve the sensitivity of the method. Therefore, highly sensitive determination for acarbose and ascorbic acid are achieved with detection limits of 6.27 nM and 1.23 μM, respectively. The proposed method was successfully applied to screen potential GAA inhibitors from oleanolic acid derivatives. Graphical abstract

Platinum nanoflowers (PtNFs) were utilized in a competitive enzyme-linked immunosorbent assay (ELISA) and in a lateral flow immunoassay (LFIA) for superior peroxidase-like activity and intense brown color, respectively. PtNFs were linked to the polyclonal antibody (pAb) to form the pAb-PtNFs probes for the dual immunoassay. Based on optimized pAb-PtNF probes, both enzyme-linked immunosorbent assay (PtNFs-ELISA) and lateral flow immunoassay (PtNFs-LFIA) perform very well. The absorbance at 450 nm decreases linearly in the DHEA concentration range 2.1 to 118.1 ng mL⁻¹, and the limit of detection is 1.3 ng mL⁻¹ and the IC₅₀ value is 15.7 ng mL⁻¹ of PtNFs-ELISA. The visual cut-off value of PtNFs-LFIA is 10.0 ng mL⁻¹. The average recoveries from spiked samples range from 95.0 to 108.9% with a coefficient of variation below 12.2%. Excellent recoveries and correlation between the two methods were observed. Furthermore, the designed immunosensors exhibited good selectivity, confirming a broad development prospect in DHEA monitoring. Graphical Abstract