A biocompatible bacterial cellulose/tannic acid composite with antibacterial and anti-biofilm activities for biomedical applications.

Biofilm-associated infections are in a high rate of recurrence and biofilms show formidable resistance to current antibiotics, making them a growing challenge in biomedical field. In this study, a biocompatible composite was developed by incorporating tannic acid (TA) and MgCl2 to bacterial cellulose (BC) for antimicrobial and anti-biofilm purposes. The morphology was investigated by scanning electron microscopy (SEM), and chemical structure were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS). In vitro release profiles of tannic acid revealed that the Mg2+ cross-links help impede the release of TA from BC matrix, while composite BC-TA lacked Mg2+ ionic cross-links, thus more TA was released from the hydrogel. The BC-TA-Mg composites also displayed strong antibacterial activity against S. aureus, E. coli and P. aeruginosa. Moreover, the composites significantly reduced biofilm formation of S. aureus and P. aeruginosa after 24 h incubation by ∼80% and ∼87%, respectively. As a consequence, the BC-TA-Mg composites are a very promising material for combating biofilm-associated infections in biomedical and public health fields.

Fast determination of trace dimethyl fumarate in milk with near infrared spectroscopy following fluidized bed enrichment.

Near infrared spectroscopy (NIRS) has been proved to be a powerful analytical tool in different fields. However, because of the low sensitivity in near infrared region, it is a significant challenge to detect trace analytes with normal NIRS technique. A novel enrichment technique called fluidized bed enrichment has been developed recently to improve sensitivity of NIRS which allows a large volume solution to pass through within a short time. In this paper, fluidized bed enrichment method was applied in the determination of trace dimethyl fumarate in milk. Macroporous styrene resin HZ-816 was used as adsorbent material, and 1 L solution of dimethyl fumarate was run to pass through the material for concentration. The milk sample was pretreated to remove interference matters such as protein, fat, and then passed through the material for enrichment; after that, diffuse reflection NIR spectra were measured for the analyte concentrated on the material directly without any elution process. The enrichment and spectral measurement procedures were easy to operate. NIR spectra in 900-1,700 nm were collected for dimethyl fumarate solutions in the concentration range of 0.506-5.060 µg/mL and then used for multivariate calibration with partial least squares (PLS) regression. Spectral pretreatment methods such as multiplicative scatter correction, first derivative, second derivative, and their combinations were carried out to select the optimal PLS model. Root mean square error of cross-validation calculated by leave-one-out cross-validation is 0.430 µg/mL with ten PLS factors. Ten samples in an independent test set were predicted by the model with the mean relative error of 5.33%. From the results shown in this work, it can be concluded that the NIR technique coupled with on-line enrichment method can be expanded for the determination of trace analytes, and its applications in real liquid samples like milk and juice may also be feasible.

Improvement of antifouling characteristics in a bioreactor of polypropylene microporous membrane by the adsorption of Tween 20.

Surface modification by physical adsorption of Tween 20 was accomplished on polypropylene microporous membranes (PPMMs). Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR) and field emission scanning electron microscope (FE-SEM) were used to characterize the chemical and morphological changes on the membrane surfaces. Water contact angles and relative pure water fluxes were measured. The data showed that the hydrophilic performance for the modified membranes increased with the increase in the adsorption amount of Tween 20 onto the surface or into the pores of polypropylene microporous membranes. To test the antifouling property of the membranes by the adsorption of Tween 20 in a membrane bioreactor (MBR), filtration for active sludge was performed using synthetic wastewater. With the help of the data of water fluxes and the FE-SEM photos of the modified PPMMs before or after operating in a MBR for about 12 d, the PPMMs with monolayer adsorption of Tween 20 showed higher remained flux and stronger antifouling ability than unmodified membrane and other modification membranes studied.