An overview on enzyme-mimicking nanomaterials for use in electrochemical and optical assays

Various kinds of nanomaterials have been described in recent years that represent stable and low-cost alternatives to biomolecules (such as enzymes) for use in (bio)analytical methods. The materials typically include, metal/metal oxides, metal complexes, nanocomposites, porphyrins, phthalocyanines, smart polymers, and carbonaceous nanomaterials. Due to their biomimetic and other properties, such nano-materials may replace natural enzymes in chemical sensors, biosensors, and in various kinds of bioassays. This overview (with 252 references) highlights the analytical potential of such nanomaterials. It is divided into sections on (a) the types of nanomaterials according to their intrinsic nature, (b) non-enzymatic sensor designs (including electrochemical, colorimetric, fluorescent and chemiluminescent methods), and (c), applications of non-enzymatic sensors in the biomedical, environmental and food analysis fields. We finally address current challenges and future directions.

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Graphical abstract This review discusses different types of nanomaterials, which are explored as a potential biomimetic material to replace the natural enzyme in the field of biosensors, and have found widespread applications in biomedical, food and environmental analysis.

     

Bacteriostatic activities of N-substituted tris-thioureas bearing amino acid and aniline substituents

A series of tri-substituted thiourea derivatives were synthesized by the reaction of 1,3,5-triacetylbenzoyl isothiocyanate with aminoacids and aniline derivatives. All thiourea derivatives were characterized by FT-IR, ¹H and ¹³C NMR spectroscopy. Antibacterial activities against wild-type Escherichia coli American Type Culture Collection 8739 were determined by use of the turbidimetric methodto evaluate the effect of varying amino groups on the synthesized thioureas. Tris-thiourea derivatives bearing ortho-chloroaryl substituents showed excellent antibacterial activity against E. coli with minimal inhibitory concentration (MIC) of 96 ppm. The optimum inhibition was dependent on the type of amines and the position of the halogen in aniline.     

Time and spectrally resolved fluorescence of Xe2 molecules excited with synchrotron radiation

Time and energy resolved fluorescence of Xe has been investigated using pulsed synchrotron radiation. The radiative lifetime of the relaxed Xe*₂ (I_u) and its collisional mixing with Xe*₂ (O⁺_u) are measured. Rate constants for molecular formation are deduced. Different steps of the reaction kinetics are isolated by using various excitation wavelengths.     

Changes in electrolyte structure in solid state cells during discharge: Extended x-ray absorption fine structure study

The first EXAFS study of a solid state battery system is reported. The working cell is based on a copper(I) iodide-sulphonium iodide electrolyte. The EXAFS results clearly indicate that cell modification occurs during cell discharge.     

Synthesis,characterization, and biological evaluation of new polyester containing Schiff base metal complexes

The production of new biocidal polyester Schiff base metal complexes [PESB–M(II)] via polycondensation reaction between chelated Schiff base diol and adipoyl chloride is reported. The resulting polyesters were characterized by physico-chemical and spectroscopic methods. The analytical data of all the synthesized polyesters were found to be in good agreement with 1:1 molar ratio of chelated Schiff base diol to adipoyl chloride. Thermogravimetric analyses of synthesized polyesters were studied by TG in nitrogen atmosphere up to 1073 K and results indicate that Cu(II) polyester complex exhibited better heat resistant properties than the other polyesters complexes. Magnetic moment and UV–visible spectra were examined to explain the structure of all the polyesters which reveled that Mn(II), Co(II), Ni(II) have octahedral geometry while Cu(II) possess a distorted octahedral geometry. These newly developed polyesters were also tested for their antibacterial activity against several bacteria and fungi. Among all the tested compounds PESB–Cu(II) possess the highest bactericidal and fungicidal activity.     

Particle tracking to reveal gelation of hectorite dispersions

Passive microrheological techniques using particle tracking have been developed for the study of the gelation of hectorite suspensions. By following the Brownian motion of the particles, it is possible to determine the increasing caging of the particles with time, as the system gels. Since only the Brownian motion is followed, the gelation process itself should not be affected by the measurement. As gelation proceeds the increasing heterogeneity of the particle environments can be monitored by a variety of measures, including kurtosis. An effective viscosity can be extracted from the measurements and used to indicate the gelation process.