ABSTRACT
We report that Fe3O4@Au core-shell nanoparticles (NPs) serve as a multifunctional molecule delivery platform. This platform is also suitable for sensing the doxorubicin (DOX) through DNA hybridization, and the amount of carried DOX molecules was determined by size-dependent Fe3O4@Au NPs. The limits of detection (LODs) for DOX was found to be 1.839 nM. In our approach, an Au nano-shell coating was coupled with a specially designed DNA sequence using thiol bonding. By means of a high-frequency magnetic field (HFMF), a high release percentage of such a molecule could be efficiently achieved in a relatively short period of time. Furthermore, the thickness increase of the Au nano-shell affords Fe3O4@Au NPs with a larger surface area and a smaller temperature increment due to shielding effects from magnetic field. The change of magnetic property may enable the developed Fe3O4@Au-dsDNA/DOX NPs to be used as future nanocarrier material. More importantly, the core-shell NP structures were demonstrated to act as a controllable and efficient factor for molecule delivery.
ABSTRACT
Cellulose is the most abundant renewable polysaccharide with a high potential for degradation to useful end products. In nature, most cellulose is produced as crystalline cellulose. Therefore, cellulases with high hydrolytic activity against crystalline cellulose are of great interest. In this study, a crystalline cellulose degradation enzyme was investigated. The cDNA encoding a ß-glucanase, CbhYW23-2, was cloned from the ruminal fungus Piromyces rhizinflatus. To examine the enzyme activities, CbhYW23-2 was expressed in Escherichia coli as a recombinant His(6) fusion protein and purified by immobilized metal ion-affinity chromatography. Response surface modeling (RSM) combined with central composite design (CCD) and regression analysis was then employed for the planned statistical optimization of the ß-glucanase activities of CbhYW23-2. The optimal conditions for the highest ß-glucanase activity of CbhYW23-2 were observed at 46.4°C and pH 6.0. The results suggested that RSM combined with CCD and regression analysis were effective in determining optimized temperature and pH conditions for the enzyme activity of CbhYW23-2. CbhYW23-2 also showed hydrolytic activities toward Avicel, carboxymethyl cellulose (CMC), lichenan, and pachyman. The results also proved that the high activity of CbhYW23-2 on crystalline cellulose makes it a promising candidate enzyme for biotechnological and industrial applications.
