Portable smartphone platform based on a ratio fluorescence probe for situ visual monition of cardiac disease markers in vitro

Creatine kinase (CK), as an important biochemical index of cardiac injury, is very significant for early and accurate diagnosis of acute myocardial infarction or cardiac arrest. However, the sensitivity and specificity of CK detection still face great challenges. Herein, a ratio fluorescence probe was designed and prepared by electrostatic interaction between boron and nitrogen doped carbon dots (BN-L-CDs) as a response signal and Ru(bpy)3Cl2·6H2O as independent reference signal. Notably, the BN-L-CDs@[Ru(bpy)3]2+ displayed an ultra-fast fluorescence response to CK in ATP medium and an excellent linear relationship was observed between the concentration of CK and the fluorescence recovery ratio with a detection limit as low as 1.20 U/L. Mechanism investigates demonstrated that the "ON-OFF-ON" progress could be attributed to the formation of the non-luminescent ground state complex BN-L-CDs-ATP by the interaction of BN-L-CDs with ATP and the dissociation of complex under the catalysis of CK, respectively. Besides, the ratio fluorescence probe was further applied to living cell imaging due to its excellent biocompatibility. Importantly, a portable visual sensing platform was developed by combining a ratio fluorescence probe with a mobile phone color recognition application. Therefore, this new sensor provided a new perspective for the convenient monitoring of CK and paved the way for the relevant applications of clinical diagnostics.