Hu Xuetao

Bacteria counting method based on polyaniline/bacteria thin film

A simple and rapid bacteria counting method based on polyaniline (PANI)/bacteria thin film was proposed. Since the negative effects of immobilized bacteria on the deposition of PANI on glass carbon electrode (GCE), PANI/bacteria thin films containing decreased amount of PANI would be obtained when increasing the bacteria concentration. The prepared PANI/bacteria film was characterized with cyclic voltammetry (CV) technique to provide quantitative index for the determination of the bacteria count, and electrochemical impedance spectroscopy (EIS) was also performed to further investigate the difference in the PANI/bacteria films. Good linear relationship of the peak currents of the CVs and the log total count of bacteria (Bacillus subtilis) could be established using the equation Y=-30.413X+272.560 (R(2)=0.982) over the range of 5.3×10(4) to 5.3×10(8)CFUmL(-1), which also showed acceptable stability, reproducibility and switchable ability. The proposed method was feasible for simple and rapid counting of bacteria.

Near-infrared spectroscopy coupled chemometric algorithms for prediction of antioxidant activity of black goji berries (Lycium ruthenicum Murr.)

In this study, near-infrared (NIR) spectroscopy coupled with partial least-squares (PLS) regression and various efficient variable selection algorithms, synergy interval-PLS (Si-PLS), backward interval PLS (Bi-PLS) and genetic algorithm-PLS (GA-PLS) were applied comparatively for the prediction of antioxidant activity in black wolfberry (BW). The eight assays were used for quantification of antioxidant content. The developed models were assessed using correlation coefficients (R2) of the calibration (Cal.) and prediction (Pre.); root mean square error of prediction, RMSEP; standard Error of Cross-Validation, RMSECV and residual predictive deviation, RPD. The performance of the built model greatly improved by the application of Si-PLS, Bi-PLS and GA-PLS compared with full spectrum PLS. The R2 values determined for calibration and prediction set ranged from 0.8479 to 0.9696 and 0.8401 to 0.9638, respectively. These findings revealed that NIR spectroscopy combined with chemometric algorithms can be used for quantification of antioxidant activity in BW samples.

Near infrared spectroscopy coupled with chemometric algorithms for predicting chemical components in black goji berries (Lycium ruthenicum Murr.)

Fourier-transform near infrared spectroscopy coupled with chemometric algorithms was applied comparatively for the quantification of chemical compositions in black wolfberry. The compositional parameters, i.e. total flavonoid content, total anthocyanin content, total carotenoid content, total sugar, and total acid were performed for quantification. Model results were evaluated using the correlation coefficients of determination for calibration (R2) and prediction (r2), root-mean-square error of prediction and residual predictive deviation. The findings revealed that the performances of models based on variable selection such as synergy interval-PLS, backward interval-PLS and genetic algorithm-PLS were better than the classical PLS. The performance of the developed models yielded 0.88 ≤ R2 ≤ 0.97, 0.87 ≤ r2 ≤ 0.94 and 1.75 ≤ RPD ≤ 4.00. The overall results showed that the FT-NIR spectroscopy in conjunction with chemometric algorithms could be used for the quantification of the chemical composition of black wolfberry samples.

Micro-sensors based on hypha-templated coaxial microfibers

Biological templates show great potential in the fabrication of advanced materials since they are green, renewable and easy to obtain. Hyphae of Penicillium are demonstrated to be a versatile template for the fabrication of coaxial microfibers. Five kinds of nanomaterials, including ZnO, Fe3O4, Cu(OH)2, polypyrrole (PPy) and polyaniline (PANI), are coated on the hyphal surface without any modification. SEM, EDS, XRD and FT-IR were employed to confirm the morphology and chemical components of the prepared microfibers. The results showed that the fabricated nanomaterials were attached firmly on the hyphal surface to form an outside shell. An adsorption experiment showed that the cations could be attached on the hyphal surface with the help of related functional groups, which explained well the formation mechanism of the coaxial structure. Microsensors based on PANI/hypha, PPy/hypha and ZnO/hypha microfibers were fabricated and tested with TMA as the model gas. The prepared sensors showed a good linear response toward TMA with an R2 higher than 0.977, relative standard deviation for reproducibility measurement lower than 7.2%, and fast response–recovery speed, which demonstrate the applicability of the prepared coaxial microfibers.