Search

In this study, we report the synthesis and application of polyethylenimine, ethylenediamine branched-functionalized carbon quantum dots (CQDs.BPEI) for protein sensing. These carbon-based nanoparticles were found to act as a protein-responsive platform. On this basis, the CQDs.BPEI system was able to detect eight different proteins (four metallic and four non-metallic), even using concentrations in the range of 5–40 nM, depending on the analyte protein. The fluorescence titrations performed at 298 and 310 K displayed fluorescence quenching, which can be explained through a collisional mechanism. It was also possible to conclude that the fluorescence quench comes from the amino acid residues on the surface of the proteins. To further check the potential of the system, we developed a “nose”-based methodology to identify proteins. Using materials, such as copper acetate and ethylenediaminetetraacetic acid, our chemical “nose” approach was able to discriminate 40 nM proteins in phosphate buffered saline (pH 7.4). In this case, the identification accuracy of the random unknown set was 83%. Overall, the results evidence the potential of CQDs.BPEI as a protein-responsive probe to detect and identify proteins. [ABSTRACT FROM AUTHOR]

In this study, magnetic nanobiocomposites were prepared in different proportions and produced with galactomannan (GM), magnetic nanoparticles of NiZn and glycerol (GL). The microstructure and morphology of the samples were characterized by Scanning Electron Microscopy (SEM), X-ray powder diffraction, Fourier transform infrared (FTIR) spectroscopy, Thermal analysis (TG) and Differential scanning calorimetry (DSC). The magnetic and dielectric behavior of the films was studied by Vibrating sample magnetometer (VSM) and Impedance spectroscopy. The results showed efficient incorporation of NiZn in the polymer matrix. The degradation profiles presented thermal events that were confirmed by endothermic and exothermic processes from DSC measurements. Films presented saturation magnetization (M s ) range from 6 to 17 emu/g and superparamagnetic behavior. It was observed that the values of dielectric constant increased as a function of the nanoparticles concentration in the bionacomposite. Thus, this kind of biocomposite could be used as a versatile magnetic-dielectric in microwave devices. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) have a large number of technological applications, such as photonic devices, molecular diagnostics, antimicrobial coating and biomedical devices. These nanomaterials can be synthesized using common fungi, which represents a green approach with the additional advantage of biocompatibility. Here we applied Tip-Enhanced Raman Spectroscopy (TERS) to obtain optical characterization with resolution beyond the diffraction limit of AgNPs produced by Rhodotorula glutinis and Rhodotorula mucilaginosa fungi. Those fungi are conventional found in ordinary soil of north part of Brazil, which biosynthesize core-shell AgNPs with protein-capping layer. With TERS we were able to investigate with lateral resolution of few nanometers the size and structure of the protein capping layer, how it interacts with the Ag core, and how sensitive the system (core + protein) is to visible light illumination. Despite the complex data generated which depends on the orientation of the protein, which is highly, it was possible to detect the stretching of the S - S sulfur bridge in amino acids. This stretch band is induced by a trans C α - S conformation acid on Rm-AgNPs, thus showing the potential of characterization of TERS in nanobiosystems. [ABSTRACT FROM AUTHOR]