Visual and quantitative determination of KAT Tip60 activity in circulating tumor cells using a smartphone

Visual detection of histone acetylation in cells is highly desirable for medical diagnostics, particularly in cancer. Currently, a single substrate-indicated multi-mode visual platform has been developed for detecting the activity of acetyltransferase (KAT Tip60) in circulating tumor cells (CTCs) of esophageal cancer. o-Phenylenediamine (OPD) serves as a single indicator in our constructed multi-mode analytical method, where the introduction of Cu(II) stimulates a change in fluorescent/UV–vis signals and colors. However, coenzyme A (CoA), a byproduct of the acetylation process, effectively prevents the interaction between Cu(II) and OPD, and this competitive reaction is aptly associated with the KAT Tip60-domonicated acetylation process. Good linear relationships are observed between the optical signals in the multi-mode method and the logarithms of the Tip60 concentration, with detection limits of 0.0045 ng/mL (fluorescence) and 0.058 ng/mL (UV–vis), respectively, calculated as 3σ/slope. To meet the needs of smart/precision medicine, a smartphone-based visualization approach tailored to the red-green-blue (RGB) color space is developed via Cu(II)-OPD redox catalysis. This approach is successfully employed for the analysis of Tip60-indicated acetylation in CTCs of esophageal cancer. This study establishes an important foundation for advancing RGB color-based smartphone modes for actual analyses, and integrating another catalytic unit based on the single OPD substrate presents a viable strategy for analyzing other biomarkers in cancer-targeted clinical applications.