Colorimetric detection of cancer biomarker based on enzyme enrichment and pH sensing

Colorimetric pH sensing is a favorable strategy which can be used to detect cancer biomarkers due to its convenience and visibility. However, low target abundance and interference from complex compositions limited its practical application. To address this problem, we proposed a sensitive pH-based colorimetric strategy based on glucose oxidase (GOD) enrichment and catalysis for amplified detection of cancer biomarker while avoiding the interference from samples and analysis processes. In detail, an isothermal DNA signal amplification strategy with dendritic product, multi-branched rolling circle amplification (mb-RCA), is used to effective enrich natural acid-generating enzyme GOD for further catalysis and pH-based colorimetric analysis. Moreover, mb-RCA is integrated with magnetic separation system to avoid potential interference. In the analysis using human plateletderived growth factor-BB (human PDGF-BB) as a model protein biomarker, this strategy shows favorable specificity and detection limits (0.94 pM). Therefore, it is believed that the successful construction of this pH-based colorimetric strategy is valuable in promoting the practical application of pH in bioanalysis, and it can provide guidance for the development of other high-performance sensors.