A cage-like PbS nanostructure was functionalized with platinum nanoparticles, and the resulting material (PtNP@PbS) was deposited on a glassy carbon electrode in order to study the direct electron transfer to FADH2 in glucose oxidase (GOx) and further to construct a glucose biosensor. The PtNP@PbS nanostructure and the biosensor were characterized using scanning electron microscopy, UV-vis and electrochemical impedance spectroscopy, and by cyclic voltammetry. Compared to the use of cage-like PbS alone, the PtNP@PbS nanostructure shows much higher electrochemical activity and an enhanced direct electron transfer rate. The GOx loaded onto the nanostructure displays good enzymatic activity and an apparent electron transfer rate constant of 3.0 s−1. The glucose biosensor is operated best at −0.4 V (vs. SCE) and then exhibits a linear range that extends from 4 μM to 1.1 mM, with a detection limit as low as 1 μM (at an S/N ratio of 3). The biosensor is selective, acceptably repeatable and stable. It was applied to the determination of glucose in human serum samples.

The authors have prepared a platinum nanoparticle-assembled nanoflake-like SnS2 nanocomposite of the type PtNP@SnS2 as a support for immobilization of glucose oxidase (GOx) to obtain an electrochemical glucose biosensor based on direct electron transfer of GOx. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, static water contact angle measurements, and cyclic voltammetry were used to characterize the nanocomposite and the glucose biosensor. The nanocomposite has a large surface-to-volume ratio, excellent hydrophiliciy, and high electrochemical activity. This promotes the direct electron transfer between GOx and the surface of a glassy carbon electrode (GCE). The GOx immobilized on the nanocomposite displays good bioactivity, and the surface coverage of the modified electrode is 4.15 × 10−11 mol·cm−2. Under optimum conditions and at a working voltage of −0.4 V vs. SCE, the glucose biosensor exhibits a linear response in the 0.1 to 1.0 mM and 1.0 to 12 mM glucose concentration ranges, with a lower detection limit of 2.5 μM (at an S/N ratio of 3). The biosensor shows excellent selectivity and was successfully applied to the determination of glucose in human serum samples.

•Perovskite-type CaTiO3NPs was exploited as efficient matrix to immobilize proteins.•A novel and sensitive electrochemical biosensor was constructed based on CaTiO3NPs.•The proposed glucose biosensor presented high sensitivity and low detection limit.•The CaTiO3NPs provided the promising perovskite nanomaterials for biosensing applications.In this work, novel perovskite-type calcium titanate nanoparticles (CaTiO3NPs) were for the first time exploited for the immobilization of proteins and the development of electrochemical biosensor. The CaTiO3NPs were synthesized with a simple and cost-effective route at low temperature, and characterized by scanning electron microscopy, X-ray photoelectron spectroscopic spectrum, electrochemical impedance spectrum, UV–visible spectroscopy, Fourier transform infrared spectrum, and cyclic voltammetry, respectively. The results indicated that CaTiO3NPs exhibited large surface area, and greatly promoted the direct electron transfer between enzyme molecules and electrode surface. The immobilized enzymes on this matrix retained its native bioactivity and exhibited a surface controlled, quasi-reversible two-proton and two-electron transfer reaction with an electron transfer rate of 3.35 s−1. Using glucose oxidase as model, the prepared glucose biosensor showed a high sensitivity of 14.10±0.5 mA M−1 cm−2, a wide linear range of 7.0×10−6 to 1.49×10−3 M, and a low detection limit of 2.3×10−6 M at signal-to-noise of 3. Moreover, the biosensor also possessed good reproducibility, excellent selectivity and acceptable storage life. This research provided a new-type and promising perovskite nanomaterials for the development of efficient biosensors.

3D ordered silver nanoshells silica photonic crystal beads as a novel encoded surface enhanced Raman scattering substrate are proposed for the development of highly efficient multiplex bioassays.

A novel and recyclable poly(polyethylene glycol diacrylate/maleamic acid) (p(PEGDA/MALA)) copolymer hydrogel beads were for the first time synthesized through a microfluidic method and used for the removal of heavy mental ions from water. The monodisperse and size-controlled pregel droplets were firstly prepared by a microfluidic device and then polymerized to the hydrogel beads under UV irradiation. The synthesized p(PEGDA/MALA) hydrogel beads were characterized using various techniques and showed good adsorption property for Pb2+. The influencing factors on the adsorption process of Pb2+ were investigated in detail. The experiment results indicated that Pb2+ adsorption process was pH dependent, and agreed with the Langmuir monolayer model and pseudo-second-order equation. The adsorbing mechanism of copolymer hydrogel beads for Pb2+ mainly resulted from the electrostatic interaction and chelation action. The competitive adsorption experiment indicated that the affinity order in multicomponent adsorption was Pb2+>Cu2+>Cd2+. The well-designed p(PEGDA/MALA) copolymer hydrogel beads had excellent adsorption capacity and high recyclability and showed a promising application prospect in the decontamination of heavy metal ions in water.

3D ordered silver nanoshells silica photonic crystal beads as a novel encoded surface enhanced Raman scattering substrate are proposed for the development of highly efficient multiplex bioassays.