Redefining Chinese calligraphy rice paper: an economical and cytocompatible substrate for cell biological assays

Abstract

Paper is a permeable porous material composed of a solid network of fibers. It is cheap, abundant, disposable and recyclable and has self-powered fluid wicking properties that are useful in building analytical devices. Paper-based cell assays are still in their infancy compared with enzyme- and protein-based analyses. For the first time, we show the potential of rice paper (an organic paper specifically used in Chinese calligraphy) for building cell analysis platforms. Rice paper's solution wicking and surface characterizations prove that it has a similar chemical configuration as that of a standard Whatman filter paper. Moreover, lactate dehydrogenase (LDH) release assay and WST-1 cell growth assay show that rice paper has better cell-compatibility features and improved cell distribution. The cell anchors and spreads along the cellulose fiber of the rice paper, whereas the porous rice paper matrix provides a sufficient surface area for cell growth. Cell-based immunohistochemistry was conducted to measure the expression of O-linked N-acetylglucosamine (O-GlcNAc) protein on prostate cancer cell DU145. An enhanced colorimetric signal was observed from cells grown on rice paper-based cell culture platform than those grown on 2D culture dish. The feasibility of fabricating rice paper with both direct crafting and wax printing—as well as on-paper cell immunoassays for on-demand applications—confirms the potential of rice paper as a new substrate for building paper devices for cell biology studies.