Application of surface selective site-directed crystallization in a visual assay of DNA†

Abstract

Visual analysis methods have received widespread attention due to their simplicity, economy, and intuitive results. In this work, a visual DNA quantitative analysis method based on surface selective site-directed crystallization (SSSC) was developed. Firstly, we explored the formation of calcium carbonate crystals with unique polymorphism induced by the surface of functionalized glass slides with different groups; among them, the calcite induced by the –COOH functional group has a uniform shape, larger size, and even distribution, so it serves as a signal promoter. In contrast, due to the –N(CH₃)₃ group acting as a signal inhibitory molecule by inhibiting crystallization, the signal molecule is captured through DNA hybridization, and the crystallization reaction is performed. The calcite growing on the DNA site is visible to the naked eye, and the DNA molecules hybridized on the surface of the glass slide are further quantified. The detection limit of this proposed visual method is 0.1 fM, and only a smartphone is needed to complete basic quantification. This work provides a basis for research into the use of single crystals as digital readouts in the field of DNA analysis, with the advantages of being simple and economical and requiring minimal equipment.