SERS-based error calibration of a TMB-H2O2 colorimetric system.

3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 is widely used as an effective colorimetric system, in which the color reaction is implemented with peroxidase-catalyzed TMB oxidation by H2O2 that usually measured UV-vis absorption spectra or Raman spectra. However, its low accuracy significantly limits its application. Blue charge transfer complex (CTC), which is the product of TMB and H2O2 reaction and is used as the basis for partial colorimetric methods, usually causes colorimetric error owing to changes in the UV-vis absorption and Raman spectra during TMB oxidation under various environmental conditions (catalyst type, temperature, H2O2 concentration). Herein, we propose a surface-enhanced Raman spectrum (SERS)-based error calibration method to improve the accuracy of the TMB-H2O2 colorimetric system. It is found that under 633 nm laser excitation, TMB has three Raman peaks at 1189, 1335 and 1609 cm-1 in the single-electron oxidation phase, and these peaks disappear completely in the two-electron oxidation phase. By comparing these Raman peaks, we can conveniently obtain the actual process information during TMB oxidation. Using the proposed method, the accuracy of the TMB-H2O2 colorimetric system improved by more than 15%. Importantly, this SERS-based TMB-H2O2 error calibration method will open a new horizon for enzyme-linked immunosorbent assay (ELISA) and other biomedical applications.

Differential phase measurement based on synchronous phase shift determination.

Based on synchronous phase shift determination, we propose a differential phase measurement method for differential interference contrast (DIC) microscopy. An on-line phase shift measurement device is used to generate carrier interferograms and determine the phase shift of DIC images. Then the differential phase can be extracted with the least-squares phase-shifting algorithm. In addition to realizing on-line, dynamic, real-time, synchronous and high precision phase shift measurement, the proposed method also can reconstruct the phase of the specimen by using the phase-integral algorithm. The differential phase measurement method reveals obvious advantages in error compensation, anti-interference, and noise suppression. Both simulation analysis and experimental result demonstrate that using the proposed method, the accuracy of phase shift measurement is higher than 0.007 rad. Very accurate phase reconstructions were obtained with both polystyrene microspheres and human vascular endothelial.

Tracking intracellular nuclear targeted-chemotherapy of chidamide-loaded Prussian blue nanocarriers by SERS mapping.

The novel histone deacetylase drug chidamide (CHI) has been proven to regulate gene expression associated with oncogenesis via epigenetic mechanisms. However, huge side effects such as non-targeting, poor intracellular accumulation and low nuclear entry efficiency severely restrict its therapeutic efficacy. Dual-targeted nanodrug delivery systems have been proposed as the solution. Herein, we developed a CHI-loaded drug delivery nanosystem based on Prussian blue (PB) nanocarrier, which combines surface-enhanced Raman scattering (SERS) tracking function with cancer cell/nuclear-targeted chemotherapy capability. With the property of background-free SERS mapping, PB nanocarriers can serve as tracking agents to localize intracellular CHI. The incorporation of targeted molecules specifically enhances the cancer cell/nuclear internalization and chemotherapeutic effects of CHI-loaded PB nanocarriers. In vitro cytotoxicity assay clearly shows that the constructed CHI-loaded PB nanocarriers have significant inhibitory on Jurkat cell proliferation. Furthermore, SERS spectral analysis of Jurkat cells incubated with the CHI-loaded PB nanocarriers reveals obvious features of cellular apoptosis: DNA skeleton fragmentation, chromatin depolymerization, histone acetylation, and nucleosome conformation change. Importantly, this CHI-loaded PB nanocarrier will provide a new insight for lymphoblastic leukemia targeted chemotherapy.