Colorimetric enzyme-linked immunosorbent assay (ELISA) has been widely applied as the gold-standard method for cytokine detection for decades. However, it has become a critical challenge to further improve the detection sensitivity of ELISA, as it is limited by the catalytic activity of enzymes. Herein, we report an enhanced colorimetric ELISA for ultrasensitive detection of interleukin-6 (IL-6, as a model cytokine for demonstration) using Pd@Pt core@shell nanodendrites (Pd@Pt NDs) as peroxidase nanomimics (named “Pd@Pt ND ELISA”), pushing the sensitivity up to femtomolar level. Specifically, the Pd@Pt NDs are rationally engineered by depositing Pt atoms on Pd nanocubes (NCs) to generate rough dendrite-like Pt skins on the Pd surfaces via Volmer–Weber growth mode. They can be produced on a large scale with highly uniform size, shape, composition, and structure. They exhibit significantly enhanced peroxidase-like catalytic activity with catalytic constants (Kcat) more than 2000-fold higher than those of horseradish peroxidase (HRP, an enzyme commonly used in ELISA). Using Pd@Pt NDs as the signal labels, the Pd@Pt ND ELISA presents strong colorimetric signals for the quantitative determination of IL-6 with a wide dynamic range of 0.05–100 pg mL−1 and an ultralow detection limit of 0.044 pg mL−1 (1.7 fM). This detection limit is 21-fold lower than that of conventional HRP-based ELISA. The reproducibility and specificity of the Pd@Pt ND ELISA are excellent. More significantly, the Pd@Pt ND ELISA was validated for analyzing IL-6 in human serum samples with high accuracy and reliability through recovery tests. Our results demonstrate that the colorimetric Pd@Pt ND ELISA is a promising biosensing tool for ultrasensitive determination of cytokines and thus is expected to be applied in a variety of clinical diagnoses and fundamental biomedical studies.
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This content will become publicly available on March 2, 2025
Light-Enhanced Micropyramidal Sensors for Interleukin-6 Impedance Detection
The inflammation marker Interleukin 6 (IL-6) typically remains below 5 pg/mL in the serum of healthy individuals but can increase tenfold during inflammation in chronic conditions like COVID-19 and rheumatoid arthritis, as well as acute conditions like sepsis. This study is focused on the rapid detection of IL-6 to monitor both chronic and acute diseases. The novel sensor, designed with gold-coated micropyramids on the electrodes, was fabricated using the two-photon polymerization method, enabling low-volume sensing capabilities (2-3 μL). The micropyramids were surface functionalized with interleukin-6 antibodies towards developing an affinity biosensor specific to the physiological relevant range of IL-6 of 5.1 and 18.8 pg/mL in mild inflammation. Sensing was achieved by measuring impedance changes associated with IL-6 binding to the antibodies on the micropyramids interfaced using electrochemical impedance spectroscopy. It was observed that the signals from the lowest detection concentration was enhanced by 3 times at 1500 hz when the 532 nm green laser was incident on the micropyramids. This innovative approach can be expanded to the detection of cytokines not only in serum but also in respiratory samples. As a result, it opens up new avenues for monitoring local inflammation within the lungs and assessing systemic inflammation levels throughout the body.
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- NSF-PAR ID:
- 10476213
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- The international IEEE Aerospace Conference
- Format(s):
- Medium: X
- Location:
- Big Sky, Montana
- Sponsoring Org:
- National Science Foundation
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