Enhancing Photoelectric Response of an Au@Ag/AgI Schottky Contact through Regulation of Localized Surface Plasmon Resonance.

Carrier generation and migration are both pivotal to photoelectric (PE) response. Formation of a Schottky contact is conducive to promote carrier migration but cannot fundamentally magnify carrier generation, limiting the eventual PE performance. In this work, an Au@Ag/AgI Schottky contact is established by in situ growth of AgI nanotriangles on the surface of Au@Ag nanoparticles (NPs), and PE enhancement of the Schottky contact is realized by regulating localized surface plasmon resonance (LSPR) properties. In comparison with Ag/AgI Schottky contact, assembly of Au NPs in the center of Ag NPs adjusts the dominated LSPR property from hot-electron transfer (HET) to plasmon-induced resonance energy transfer (PIRET). With the concurrent manipulation of HET and PIRET, additional energy can be employed for carrier generation, while photogenerated electrons offset by hot electrons are reduced, which jointly enlarges PE responses of the Au@Ag/AgI Schottky contact up to 4 times. Benefitted from the etching of thiols to Ag-based materials, the Au@Ag/AgI Schottky contact is further applied to the construction of a photoelectrochemical cysteine sensor. This work proposes a general strategy to enhance PE responses of Schottky contacts, which may advance the design of LSPR-related PE systems.

Enhanced electrochemiluminescence cytosensing based on abundant oxygen vacancies contained 2D nanosheets emitter coupled with DNA device cycle-amplification.

Developing efficient and sensitive cytosensing method has great significance for the detection of low abundant circulating tumor cells (CTCs). Electrochemiluminescence (ECL) biosensor, as an attractive analytical tool, has shown a great potential in sensitive cell counting. Its detection efficiency is strongly dependent on the electrochemiluminescent materials, whose property is related to its morphology and surface vacancies. Herein, the ultrathin Lu2O3-S nanosheets contain abundant oxygen vacancies were newly synthesized. Its special two-dimensional (2D) structure morphology and surface vacancy endowed it intensified and stable ECL emission. The possible mechanism was deduced from experiments and discussed. Then, through integrating with a DNA device cycle-amplification system plus signal conversion pretreatment, we constructed a crossed enhanced ECL cytosensing platform. In this system, the target cells were transformed into programmable sequences, which could be next coupled with DNA device cycle-amplification on the modified electrode surface. Using Ag2S quantum dots as the energy acceptor toward Lu2O3-S donor, and CCRF-CEM cells (CEM) as the model CTCs, an enhanced ECL cytosensing platform was proposed, displaying good analytical performance for acute lymphoblastic leukemia cancer cell detection. The ECL signal responded proportionately on the CEM cells concentration in a wide range of 5 × 10 to 1 × 106 cells/mL, and a low detection limit of 10 cells/mL was obtained. This work provided an alternative way to design high-performance ECL luminophores, and also would be an effective solution for CTCs counting.

Applications of DNA-nanozyme-based sensors.

Since the discovery of the enzyme-like activities of nanomaterials, the study of nanozymes has become one of the most popular research frontiers of diverse areas including biosensors. DNA also plays a very important role in the construction of biosensors. Thus, the idea of combined applications of nanozymes with DNA (DNA-nanozyme) is very attractive for the development of nanozyme-based biosensors, which has attracted considerable interest of researchers. To date, many sensors based on DNA-functionalized or templated nanozymes have been reported for the detection of various targets and highly accelerated the development of nanozyme-based sensors. In this review, we summarize the main applications and advances of DNA-nanozyme-based sensors. Additionally, perspectives and challenges are also discussed at the end of the review.

Fe-Porphyrin-Based Covalent Organic Framework As a Novel Peroxidase Mimic for a One-Pot Glucose Colorimetric Assay.

Covalent organic frameworks (COFs) have recently emerged as very fascinating porous polymers due to their attractive design synthesis and various applications. However, the catalytic application of COF materials as enzymatic mimics remains largely unexplored. In this work, the Fe-porphyrin-based covalent organic framework (Fe-COF) has been successfully synthesized through a facile postsynthetic strategy for the first time. In the presence of hydrogen peroxide (H2O2), the Fe-COF can catalyze a chromogenic substrate (3,3',5,5'-tetramethylbenzidine (TMB)) to produce color, and this just goes to show that it has an inner peroxidase-like activity. Moreover, the kinetic studies indicate that the Fe-COF nanomaterial has a higher affinity toward both the substrate H2O2 and TMB than the natural enzyme, horseradish peroxidase (HRP). Under the optimized conditions, the Fe-COF nanomaterial was applied in a colorimetric sensor for the sensitive detection of H2O2. The detection range was from 7 to 500 µM, and the detection limit was 1.1 µM. Furthermore, the combination of the Fe-COF with glucose oxidase (GOx) can be implemented to measure glucose by a one-pot method, and the obtained detection range was from 5 to 350 µM; the detection limit was 1.0 µM. It was proved that the sensor can be successfully used to detect the concentration of glucose in human serum samples. As a peroxidase mimic, the Fe-COF exhibits the advantages of easy preparation, good stability, and ultrahigh catalytic efficiency. We believed that the proposed method in this work would facilitate the applications of COF-based composites as enzymatic mimics in biomedical fields.

Biocompatible phosphonic acid-functionalized silica nanoparticles for sensitive detection of hypoxanthine in real samples.

A novel hypoxanthine biosensor fabricated by immobilizing the xanthine oxidase (XOD) onto the phosphonic acid-functionalized silica (SiO2-P) film on the surface of glassy carbon electrode (GCE) was designed and constructed in this work. A biomimetic platform was designed with the phosphonic acid-functionalized silica nanoparticles (SiO2-P NPs) synthesized by the method of reverse microemulsion and electrostatic binding. In such a platform, XOD was selected as model protein to fabricate hypoxanthine biosensor based on SiO2-P NPs. The nanocomposite was characterized with transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDS) and electrochemical impedance spectroscopy (EIS). Based on the advantageous functions of SiO2-P NPs, the entrapped XOD could preserve its bioactivity and exhibited an excellent electrochemical behavior with a formal potential of -0.37 V in phosphate buffer solution (PBS, pH=7). Response studies to hypoxanthine were carried out using current-time response curve. The biosensor exhibited a wide linear response ranging from 1.00×10(-6) to 2.61×10(-4) M. The detection limit of 2.33×10(-7) M at a signal-to-noise ratio of 3 was lower than that most reported previously. In addition, the electrode modified with XOD/(SiO2-P NPs) film also had a strong anti-interference ability in the presence of uric acid (UA) and ascorbic acid (AA). The assay results of hypoxanthine in fish samples were in a good agreement with the reference values.

Fabrication and bioproperties of raspberry-type hybrid nanoparticles of Au-thioethyl pendant ligand@chitosan.

Synthesis of nanoparticles with desired size/morphology has enormous importance, especially in the compelling field of nanotechnology. In this case, a novel kind of raspberry-type hybrid nanoparticles was prepared by hybridization of chitosan (CS) with thioethyl pendant ligand (TPL) modified Au nanoparticles (Au-TPL@CS NPs). Such method was based on ionic gelation using sodium tripolyphosphate as a counterion. The blood compatibility of Au-TPL@CS NPs was characterized by coagulation tests, plasma recalcification time, hemolysis assay, morphological changes of red blood cells (RBCs) and complement activation in vitro. The results showed that Au-TPL@CS NPs exhibited good blood compatibility. The possible underlying mechanism was also present. Finally, the direct electron transfer reactivity of the Hemoglobin/Au-TPL@CS NPs/multi-walled carbon nanotubes/glassy carbon electrode was investigated with cyclic voltammetry measurements. The biosensor exhibited a good electrocatalytic activity to the reduction of H2O2. Such new type of Au-TPL@CS NPs provides a promising platform of biological system for early illness detection and treatment in future.

Fabrication of glucose biosensor for whole blood based on Au/hyperbranched polyester nanoparticles multilayers by antibiofouling and self-assembly technique.

Acknowledging the benefits of hyperbranched polymers and their nanoparticles, herein we report the design and synthesis of sulfonic acid group functionalized hydroxyl-terminated hyperbranched polyester (H30-SO3H) nanoparticles and their biomedical application. The H30-SO3H nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance spectroscopy ((1)H NMR). The good hemocompatibility of H30-SO3H nanoparticles was also investigated by coagulation tests, complement activation and platelet activation. The novel glucose biosensor was fabricated by immobilizing the positively charged Au nanoparticles, H30-SO3H nanoparticles and glucose oxidase (GOx) onto the surface of glassy carbon electrode (GCE). It can be applied in whole blood directly, which was based on the good hemocompatibility and antibiofouling property of H30-SO3H nanoparticles. The biosensor had good electrocatalytic activity toward glucose with a wide linear range (0.2-20 mM), a low detection limit 1.2×10(-5) M in whole blood and good anti-interference property. The development of materials science will offer a novel platform for application to substance detection in whole blood.

Innovative biocompatible nanospheres as biomimetic platform for electrochemical glucose biosensor.

In this work, the silica- phytic acid (SiO2-PA) nanocomposites were synthesized by the method of reverse microemulsion and electrostatic binding. The newly designed materials were used to develop a novel glucose biosensor by immobilizing glucose oxidase (GOx) onto the SiO2-PA nanocomposites film on the surface of glassy carbon electrode (GCE). The characteristics of SiO2-PA nanocomposites and GOx were obtained by using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) technique. All the results indicated that silica nanoparticales were modified with phosphate radicals successfully and the biomimetic surface was built. The entrapped GOx could preserve its bioactivity and exhibited an excellent electrochemical behavior with a formal potential of -0.548 V in phosphate buffer solution (PBS) (pH=7). Response studies to glucose were carried out using differential pulse voltammetry (DPV). The results indicated that the modified electrode can be used to determine glucose without interference from l-ascorbic acid (AA) and uric acid (UA) with the low detection limit of 0.012 mM. The comparison tests of DPVs of different electrodes in the absence and presence of glucose were also studied. The biosensor can also be used for quantification of the concentration of glucose in real samples.

Preparation of PNIPAM-g-P (NIPAM-co-St) microspheres and their blood compatibility.

The poly(N-isopropylacrylamide)-g-poly(N-isopropylacrylamide-co-styrene) microspheres (PNNS-MSs) were prepared by an emulsifier-free emulsion polymerization method. The blood compatibility of PNNS-MSs was characterized by in vitro for coagulation tests, hemolysis assay, plasma recalcification time, complement activation, platelet activation, and cytotoxicity experiments. The results showed that the PNNS-MSs have good blood compatibility and lack cytotoxicity, which may be attributed to the formation of a strong interfacial hydration layer that result from amphiphilic molecular structure of the PNIPAM shell and minimal interaction between PNNS-MSs interfaces and blood components. The PNNS-MSs provide a promising platform of blood circulation system for early illness diagnosis and therapy.

Preparation of anionic polyurethane nanoparticles and blood compatible behaviors.

The anionic polyurethane nanoparticles (APU-NPs) were obtained by an emulsion polymerization method. It was found that the average size of the prepared APU-NPs is about 84 nm, and the APU-NPs have zeta-potential of -38.9 mV. The bulk characterization of synthesized APU-NPs was investigated by FTIR. The blood compatibility of APU-NPs was characterized by in vitro for coagulation tests, complement activation, platelet activation, cytotoxicity experiments, and hemolysis assay. The results showed that the APU-NPs synthesized in this paper are blood compatible with low level of cell cytotoxicity, and the results were significant for their potential use in vivo.

Electrogenerated chemiluminescence from CdS hollow spheres composited with carbon nanofiber and its sensing application.

The electrogenerated chemiluminescence (ECL) from nanometre-sized CdS hollow spheres and carbon nanofiber (CdSHS-CNF) nanocomposites in aqueous solution and their sensing applications were studied by entrapping them in carbon paste. The CdSHS-CNF nanocomposites exhibited a peak at -1.02 V (vs. Ag/AgCl) in 0.1 M pH 8.0 PBS containing 20 mM H(2)O(2) during the cyclic sweep between 0 and -1.2 V at 40 mV s(-1). Compared with CdS hollow spheres (CdSHS), carbon nanofiber (CNF) and CdS nanocrystals and carbon nanofiber (CdSNC-CNF) nanocomposites, CdSHS-CNF not only enhanced the electrochemiluminescent intensity but also decreased the ECL starting potentials. Furthermore, by immobilizing cholesterol oxidase (ChOx) on CdSHS-CNF nanocomposites modified electrode, a sensitive and selective method was developed for detection of cholesterol using oxygen as a coreactant which captured more electrons from electrochemically reduced CdSHS-CNF than H(2)O(2). Under optimal conditions, the sensor could be used for the determination of cholesterol from 1 × 10(-6) to 4.4 × 10(-4) M with a correlation coefficient of 0.9991 and a detection limit was 8 × 10(-7) M at 3σ. The unique ECL intensity and stability of CdSHS-CNF would promote the application of nanometre-sized semiconductor hollow spheres based composites in fabricating sensors for chemical and biochemical analysis.

Preparation of polypropylene superhydrophobic surface and its blood compatibility.

The blood compatibility of the superhydrophobic polypropylene surface that prepared by Erbil's method was preliminarily evaluated by platelet-rich plasma (PRP) adhesion study, fresh human whole blood contacting experiments and scanning electron microscopy, using original polypropylene films as the controls. The results show that the superhydrophobic character of polymer surface was in favor of anticoagulation.