Three-dimensional photonic nitrocellulose for minimally invasive detection of biomarker in tumor interstitial fluid

Nitrocellulose (NC) materials have been widely used in various bioassays, including blotting, flow-through and lateral-flow assays due to their unique features such as exceptional biofunctionality, biocompatibility and capillary action. But for now, the application is limited to in vitro diagnostics using one-dimensional and twodimensional NC materials. Potential of three-dimensional (3D) NC material for bioassays, especially for in vivo detection, remains to be explored. Here we report the fabrication of 3D NC material (i.e. microneedle) for minimally invasive bioassays in tumor interstitial fluid, which contains highly concentrated species related to tumor development and progression. The material provides enough mechanical strength and biocompatibility for penetration into mouse skin, and the highly ordered photonic structure on the surface of the microneedle greatly improves the sensitivity for fluorescence immunoassay of trace biomarkers. Using our method, tumor necrosis factor-alpha (TNF-alpha) in mouse TIF is quantitatively detected as the proof-of-concept target. The level of TNF-alpha is found to increase with tumor growth, which demonstrate the potential of the method for future application in diagnostics and treatment of cancer.