MnO2 coated Au nanoparticles advance SERS detection of cellular glutathione.

Glutathione, referred to as GSH, abnormal physiologic level of GSH is an indication to some neurodegenerative diseases and cancers. A measurement of cellular GSH calls for rapid, sensitive, and selective methods. In this work, we rationally design and prepare Au@MnO2 core-shell composite nanoparticles combining with tetramethylbenzidine (TMB) molecules to determine intracellular GSH by Surface enhanced Raman scattering (SERS) technique. MnO2 plays multifunctional roles in the method, including the participation in catalyzing TMB to molecules form dimer charge-transfer complex (CTC) which own a great SERS signal reporter. With the addition of GSH, the MnO2 will be dissolving detaching CTC molecules from the surface of Au@MnO2 and resulting in a signal-off off SERS response and indirect and sensitive detection of GSH could be realized. The limit of detection of GSH by SERS method is as low as 0.1 µmol/L and a good linear relationship of GSH is found in the range from 0.5 to 30 µmol/L. Au@MnO2-SERS assay is successfully applied to detect cellular GSH, which is validated by using Enzyme-linked-immunoassay-based Kit. The Au@MnO2-SERS protocol has promising potential for clinical application.

A rapid and quantitative method for assessing the whiteness of whitened lignin based on an in-depth analysis of reported methods.

The modification of lignin to a lighter color has been a concern in lignin valorization. In the previous reports on lignin color reduction, the methods of assessing the whiteness of lignin varied from each other, due to the absence of a universal method for characterizing the lightness/darkness of dark samples. In this paper, the reported methods for assessing the whiteness of lignin were analyzed, including "comparison of absorbance curve", "absorbance at specific wavelength", "ISO or TAPPI brightness" and "photograph observation". Our study revealed that various defects existed in these methods. In light of the Munsell color system, we herein proposed a quantitative method for evaluating the whiteness of lignin, based on the finding that the sum of the reflectance of samples with the same Munsell value (whiteness) are substantially equal. A model for converting the reflectance of lignin to Munsell value was established, and the effectiveness of the model was verified and discussed. The standard deviation of the model ranges from 0.23-1.10. The applicability of the method to liquid was also discussed in the paper. Moreover, because the model was derived from the Munsell color system, it can also be applied to characterize other medium to dark-colored objects besides lignin.