A novel method to construct a 3D FeWO4 microsphere-array electrode as a non-enzymatic glucose sensor.

As the special sensor for glucose detection, a non-noble-metal nanoarray architecture is extremely attractive due to its easy accessibility to target molecules and more exposed surface area. In this communication, we report the first synthesis of FeWO4 microsphere-array on the three-dimensional (3D) Ni foam (FeWO4 microspheres/NF) as the mimetic electrode for efficient catalytic oxidation of glucose in an alkaline medium. When used as an artificial analog glucose sensor, the result of the present sensing system can also be calculated with a sensitivity of 2810 µA mM cm-2, a linear range from 0.04 mM to 2 mM and a detection limit up to 1.4 µM (S/N = 3). This glucose sensor with satisfactory stability and reproducibility can also be applied to the detection of glucose in human serum. As a promising sensing platform, this proposed 3D FeWO4 microspheres/NF may open a new strategy for pursuing electrochemical detection of biomolecules.

Copper(II) 1,4-naphthalenedicarboxylate on copper foam nanowire arrays for electrochemical immunosensing of the prostate specific antigen.

Nanowires of copper(II)-based metal-organic frameworks (Cu-MOFs) of type Cu(II)(1,4-naphthalenedicarboxylic acid) (1,4-NDC) were deposited on the surface of a copper foam by immersion of Cu(OH)2 nanowires in a solution of 1,4-NDC. An electrochemical immunosensor for the prostate specific antigen (PSA) is obtained by using the nanowire arrays as a redox signal probe. The signal is generated by the conversion of Cu(I) and Cu(II) of Cu-MOFs nanowires. Cu(1,4-NDC) nanowires contain many uncoordinated carboxyl groups which can bind to the amino groups of the PSA antibody. When PSA antibody binds to PSA antigen during an immune response, the current signal will decrease due to the electrical insulation of PSA antigen. The decrease of current is directly proportional to the increase of PSA concentration. The immunosensor, best operated at a voltage of typically -0.08 V (vs. Ag/AgCl), has a low limit of detection (4.4 fg·mL-1) and a wide linear range (0.1 pg·mL-1 to 20 ng·mL-1). This meets the demands of clinical diagnosis (with values <4 ng·mL-1) in serum. The method was applied to the determination of PSA in spiked serum. Graphical abstractSchematic representation of the in-situ growth of ordered Cu-MOFs wrapped with Cu(OH)2 nanowires, building the core-shell structure as the 3D electrode. A novel electrochemical immunosensor for PSA detection has been exploited, using the Cu-MOFs nanowire arrays on Cu foam as a redox signal probe for the first time.

Ultrathin nickel-metal-organic framework nanobelt based electrochemical sensor for the determination of urea in human body fluids.

Ultrathin nickel-metal-organic framework (Ni-MOF) nanobelts, [Ni20(C5H6O4)20(H2O)8]·40H2O (Ni-MIL-77), have been exploited successfully for the fabrication of a non-enzymatic urea sensor. Ni-MOF ultrathin nanobelts in alkaline media can be used as an efficient catalyst for urea electrooxidation. As a non-enzymatic urea sensor, Ni-MOF ultrathin nanobelts exhibit a high sensitivity of 118.77 µA mM-1 cm-2, wide linear range of 0.01-7.0 mM, and low detection limit of 2.23 µM (S/N = 3). The selectivity, stability and reliability of ultrathin Ni-MOF nanobelts towards urea oxidation are also investigated. Moreover, Ni-MOF ultrathin nanobelts were further used to detect urea in human body fluids. All these findings confirm that the urea sensor based on Ni-MOF ultrathin nanobelts is successfully prepared and promising for applications in medical diagnostics and environmental monitoring.

Ni-Fe PBA hollow nanocubes as efficient electrode materials for highly sensitive detection of guanine and hydrogen peroxide in human whole saliva.

A sensor for the determination of guanine (G) and hydrogen peroxide (H2O2) is developed based on Ni-Fe Prussian blue analogues hollow nanocubes (Ni-Fe PBA HNCs) for the first time. As a remarkable redox probe towards G and H2O2 oxidation, Ni-Fe PBA HNCs exhibit a series of predominant sensing performances as follows: lower limit of detection, broader linear range and higher selectivity due to the homogeneous hollow structure, high specific surface and the enhanced electron transfer ability of Ni-Fe PBA HNCs. As a G sensor, it exhibits a wide linear range (0.05-4.0 mM) and a low detection limit of 0.0104 µM (S/N = 3). As a H2O2 sensor, the Ni-Fe PBA HNCs show superior sensing performances with a low detection limit of 0.291 µM (S/N = 3) and a wide detection range of 0.1-20 mM. By cause of these advantages, the real-time detection of G and H2O2 in human saliva are triumphantly accomplishment, indicating the applicability of Ni-Fe PBA HNCs.