br In this study a high efficiency
In this study, a high-efficiency NiFe2O4 NTs catalytically promoted ratiomatric ECL sensing system was designed on the new ECL emitters of DBAE and lucigenin for the first time. Here, NiFe2O4 NTs was first revealed to be an efficiently promoted sensing platform for their ex-cellent catalytic performance for the OER process, in which oxygen was released to react with DBAE and stimulated a strong ECL emission. Besides, the Envision complex, one polymer containing about 100 HRP molecules and 15 antibody molecules, was first self-assembled onto Sensors & Actuators: B. Chemical 288 (2019) 80–87
NiFe2O4 NTs to realize the simultaneous amplification of two ECL sig-nals. The reason was HRP could accelerate the decomposition of H2O2 in detection solution for the generation of ROS (O2%−), which si-multaneously participated in the both ECL emission processes and re-sulted in an amplified ECL intensity. It was worth noted that the h-BN nanosheets was first disclosed here to be an excellent scaffold for the purpose of immobilizing lucigenin, where the superior corrosion re-sistance quality was conducive to the intense and stable ECL signal of lucigenin. Based on the ratio of two ECL signals from lucigenin and DBAE, a sensitive ratiometric ECL biosensor was established for HE4 sensing, which showed great promise in the early stage ovarian cancer screening and provided extensive application for the detection of other tumor markers.
Lucigenin was obtained from Sahn Chemical Technology Co. (Shanghai, China), and 2-(Dibutylamino)ethanol (DBAE), 1-Aminopyrene (AP) was purchased from Sigma-Aldrich. Envision com-plex was received from Gene Tech (Shanghai) Company Limited. In addition, N-hydroxy succinimide (NHS) and 1-ethyl-3-(3-di-methyla-minopropyl) carbodiimide hydrochloride (EDC) were obtained from Shanghai Medpep Co. (China). Bovine serum albumin (BSA, 96–99%) were bought from Biss Inc. (Beijing, China) and glutaraldehtyde (GLD, 25% aqueous solution) was gotten from Shanghai Jinshan Tingxin Chemical Plant (China). Human GW501516 protein 4 (HE4) standard and antibody was purchased from Kelei biological Technology Co., Ltd and Ab2 was from Phygene Life Sciences Co., Ltd. Interleukin-6 (IL-6), carcinoembryonic antigen (CEA), prostate specific antigen (PSA) and α-fetoprotein (AFP) standard solutions were acquired from Linc-Bio Science Co. (Shanghai, China). Other reagents obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China) were analy-tical grade. Phosphate buffer solution (PBS) with different pH values were prepared by mixing 0.1 M Na2HPO4 and 0.1 M NaH2PO4 under monitoring of PHS-3C exact digital pH metre (Shanghai, China). NiFe2O4 nanotubes (NiFe2O4 NTs, 1 mg/mL) and hexagonal boron ni-tride nanosheets (h-BN, 5 mg/mL) were prepared in this work.
Electrochemical experiments were performed on CHI760 electro-chemical workstation (Shanghai Chenghua Instrument Co., Shanghai, China). The ECL signal was collected based on the combination of BPCL Ultra-Weak luminescence Analyzer (Institute of Biophysics, Chinese Academy of Sciences, Beijing, China) with CHI760 electrochemical workstation by a three-electrode system employing glassy carbon electrode as working electrode (GCE, 3 mm diameter), Pt electrode as counter electrode, and Ag/AgCl electrode (KCl-saturated) as reference electrode. Scanning electron microscopy (SEM, S-4800 instrument) and Transmission electron microscopy (TEM, FEI F20 S-TWIN instrument) were applied for the structural characterization of the prepared nano-materials. UV–vis absorption spectra was performed on a UV 1901 spectrophotometer (Shanghai, China). X-ray diffraction (XRD) patterns
were recorded on a Rigaku X-ray diffractometer using Ni filtered Cu Ka radiation (λ = 1.5406 Å) radiation.
The NiFe2O4 NTs was synthesized as follows. Initially, 2.4 g iron chloride hexahydrate (FeCl3.6H2O), 1.28 g nickel nitrate hexahydrate (Ni(NO3)2.6H2O) and 2.2 g p-phthalic acid were added to 132 mL N,N-dimethylformamide (DMF) and kept stirring for 10 min. Afterwards, 28 mL 0.4 mol/L NaOH solutions was added dropwise to the solution. Then the above solution was transferred into a 200 mL Teflon on liner
encased into a stainless steel autoclave and heated at 120 °C for 24 h. Subsequently, the yellow product was obtained by centrifugation, washing with ultrapure water and ethanol for three times and then dried at 60 °C for 12 h. The final product was collected by annealing at 450 °C for 4 h at a heating rate of 1 °C min−1 in air.
2.4. Preparation of h-BN nanosheets
The h-BN nanosheets was synthesized as follows: firstly, 10 mg of bulk h-BN powder was dispersed in 10 ml ethanol, followed by adding 1 ml NaOH concentrated solution. After stirring for 10 min, the above solution was transferred into a Teflon-sealed autoclave and retained at 180 °C for 24 h. Subsequently, the suspension was naturally cooled down to room temperature and vacuum-filtrated using a 0.22 μm mi-croporous membrane (Millipore) to obtain white precipitate. Then the white precipitate was redispersed into water and sonicated for 30 min. After centrifugation to remove the unexfoliated h-BN, the white sus-pension was dialyzed in a 3500 Da dialysis bag against ultrapure water to neutral. The final white suspension was freeze-dried to obtain h-BN nanosheets.