Triple Amplification of 3,4,9,10-Perylenetetracarboxylic Acid by Co-Based Metal-Organic Frameworks and Silver-Cysteine and Its Potential Application for Ultrasensitive Assay of Procalcitonin.

In this work, a triple-amplified biosensor with a bioactivity-maintained peculiarity was constructed for quantitative procalcitonin (PCT) detection. As everyone knows, a strong electrochemiluminescence (ECL) signal is the premise to ensure high sensitivity for trace target detection. Hence, a valid tactic was developed to achieve signal amplification of luminophor by using Co-based metal-organic frameworks (ZIF-67) and silver-cysteine (AgCys). The ZIF-67 particles, which have more atomically dispersed Co, could play the role of a co-reaction accelerator to catalyze SO to generate abundant Co and sulfate radical anions (SO). Afterward, a mass of Co was reduced to more hydroxyl radicals (OH) by HO, thus ulteriorly reducing SO to generate more SO. Remarkably, SO was reduced to SO continuously with the recycling of Co and Co, which realized an effective signal amplification. Meanwhile, the AgCys complex with superior catalysis and biocompatibility was prepared to further improve the ECL signal and maintain the bioactivity of the biomolecule. Furthermore, HWRGWVC, a heptapeptide that was used for combining the Fc fragments of an antibody by Au-S bonding to achieve the fixed point fixation, could not only maintain bioactivity of an antibody but also improved its incubation efficiency, thus further enhancing biosensor sensitivity. Under optimum conditions, the proposed biosensor realized highly sensitive assay for PCT with a wide dynamic range from 10 fg/mL to 100 ng/mL and a detection limit as low as 3.67 fg/mL. With superior stability, selectivity, and repeatability, the prepared biosensor revealed immense potential application of ultrasensitive assay for PCT in human serum.