Responsive Nd-MOF nanorods based near-infrared photoelectrochemical cytosensor and real-time monitoring HClO releasing from cells and tumor

Designing functionalized MOFs with specific reactivity and NIR photoelectrochemical and fluorescent response is critical for developing biosensing systems. Herein, SCy7, a conjugate macrocycle ligand with a specific fluorescence responsive group to HClO, was designed and synthesized. Responsive Nd-MOF nanorods were successfully prepared by using SCy7 as the organic ligand and Nd3+ as the metal central ion. Nd-MOF nanorods show good absorption characteristics in the wavelength range of 200–1200 nm with a band gap of 0.89 eV. Nd-MOF nanorods were employed as a photoactive material to construct a near-infrared photoelectrochemical cytosensor for MCF-7 cells by integrated with an aptamer. The photocurrent variation exhibits a good linear response to MCF-7 cells in the concentration range of 50–1.0 × 107 cells mL−1, and a comparatively low detection limit of 18 cells mL−1 (S/N = 3). The NIR PEC cytosensor was also employed for monitoring endogenous HClO released from MCF-7 cells as being stimulated by PMA. HClO is an electron acceptor that can convert the anodic photocurrent into cathodic photocurrent, thus achieving monitoring HClO through the conversion of photocurrent polarity. Furthermore, Nd-MOF was coated with F127 to improve its hydrophilicity and biocompatibility, and to provide a Nd-MOF@F127 with a fluorescence emission peak at 830 nm. Nd-MOF@F127 show specific fluorescence response to HClO, and thus was successfully used in imaging HClO variation in cells and breast cancer bearing mice.