This work was financially supported by the NSFC (21505006, 21735001, 21575018), the Foundation for Innovative Research Groups of NSFC (21521063), the Hunan Provincial Natural Science Foundation of China (2017JJ3332), and the Scientific Research Fund of Hunan Provincial Education Department (16C0033, 17A002). The authors thank Professor Zhihong Liu of Wuhan University and Dr Wei Liu of Hunan University for their assistance with two photon measurement and tissue preparation, respectively.