A new chitosan derivative is prepared using chitosan.Ethyl chlorocarbonate was first introduced to the hydroxyl group of phthaloylchitosan through a nucleophilic reaction.Hydrazine was then added to recover the amino groups of chitosan and promote cross-linking.The structure of this new chitosan derivative was characterized by Fourier transform infrared(FT-IR)and proton nuclear magnetic resonance(1H NMR)spectroscopy,and its physical properties were determined by X-ray diffraction(XRD),differential scanning calorimetry(DSC),and thermogravimetric analysis(TGA).The thermal and chemical stabilities of the new derivative were improved compared with those of native chitosan.Assay of Escherichia coli adhesion on a film based on this chitosan derivative showed good adsorption and biofilm formation.
Bing-Bing ShangJun ShaYang LiuQin TuMan-Lin LuJin-Yi Wang
A new microfluidic system with four different microchambers (a circle and three equilateral concave polygons) was designed and fabricated using poly(dimethylsiloxane) (PDMS) and the soft lithography method.Using this microfluidic device at six flow rates (5,10,20,30,40,and 50 mL/h),the effects of microenvironmental geometry and aqueous flow on bacterial adhesion behaviors were investigated.Escherichia coli HB101 pGLO,which could produce a green fluorescent protein induced by L-arabinose,was utilized as the model bacteria.The results demonstrated that bacterial adhesion was significantly related to culture time,microenvironment geometry,and aqueous flow rates.Adhered bacterial density increased with the culture time.Initially,the adhesion occurred at the microchamber sides,and then the entire chamber was gradually covered with increased culture time.Adhesion densities in the side zones were larger than those in the center zones because of the lower shearing force in the side zone.Also,the adhesion densities in the complex chambers were larger than those in the simple chambers.At low flow rates,the orientation of adhered bacteria was random and disorderly.At high flow rates,bacterial orientation became close to the streamline and oriented toward the flow direction.All these results implied that bacterial adhesion tended to occur in complicated aqueous flow areas.The present study provided an on-chip flow system for physiological behavior of biological cells,as well as provided a strategic cue for the prevention of bacterial infection and biofilm formation.
Yang LiuJian-Chun WangLi RenQin TuWen-Ming LiuXue-Qin WangRui LiuYan-Rong ZhangJin-Yi Wang
