Authors: Zhuangqiang Gao | Chuanyu Wang | Jiacheng He | Pengyu Chen
Source: Chemosensors (article, 2022-09-08)
Field: Materials Science — Materials Chemistry

Pd@Pt Nanodendrites as Peroxidase Nanomimics for Enhanced Colorimetric ELISA of Cytokines with Femtomolar Sensitivity Colorimetric enzyme-linked immunosorbent assay (ELISA) has been widely applied as the gold-standard method for cytokine detection over decades. However, it has become a critical challenge to further improve the detection sensitivity of ELISA as 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> core@shell nanodendrites (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> NDs) as peroxidase nanomimics (named "<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> ND ELISA"), pushing the sensitivity up to femtomolar level. Specifically, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> 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 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>K</mml:mtext><mml:mrow><mml:mtext>cat</mml:mtext></mml:mrow></mml:msub></mml:mrow></mml:math>) more than 2000-fold higher than those of horseradish peroxidase (HRP, an enzyme commonly used in ELISA). Using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> NDs as the signal labels, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> ND ELISA are excellent. More significantly, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>Pd@Pt</mml:mtext></mml:math> 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. Detection limit ; Horseradish peroxidase ; Chemistry ; Catalysis ; Reproducibility ; Peroxidase ; Catalytic efficiency ; Enzyme ; Nuclear chemistry ; Chromatography ; Biochemistry Advanced Nanomaterials in Catalysis ; Advanced biosensing and bioanalysis techniques ; Biosensors and Analytical Detection