Preparation and separation of pure spherical cellulose nanocrystals from microcrystalline cellulose by complex enzymatic hydrolysis.

Spherical cellulose nanocrystals (CNCs), as a new and high value cellulose derivative, shows excellent application potential in many fields due to its special structure. The accurate and effective separation of pure spherical CNCs lays foundation for its further application. In this work, spherical CNCs were prepared by enzymatic hydrolysis of microcrystalline cellulose (MCC) with complex enzymes. In order to determine the optimal separation conditions of pure spherical CNCs, turbidity and Zeta potential were used to analyze the influence of pH on system stability, and the size and morphology of samples were characterized by DLS, AFM and SEM. The results showed that spherical CNCs with particle size of 24-76 nm can be separated from large particles with the help of alkali (pH = 9) dispersion and centrifugation speed of 3000 rpm. After three acid (pH = 4) washes, pure spherical CNCs were extracted and reducing sugars and enzyme proteins were removed. Compared with MCC, spherical CNCs had lower crystallinity but stronger reactivity and higher heat transfer. DTG results showed that the maximum weight loss temperature of spherical CNCs prepared by enzymatic hydrolysis was 309 °C.

Spherical vs rod-like cellulose nanocrystals from enzymolysis: A comparative study as reinforcing agents on polyvinyl alcohol.

In this paper, we have isolated cellulose nanocrystallines (CNCs) with different morphologies by enzymatic hydrolysis, and prepared flexible and transparent nanocomposite films with PVA matrix via solution casting. By means of SEM, UV-vis, XRD, DTG, FT-IR and mechanical methods, the effects of rod-shaped cellulose nanocrystallines (RCNCs) and spherical cellulose nanocrystallines (SCNCs) on PVA nanocomposite films were compared systematically. The results showed CNCs with different morphologies had little effect on the transparency of the composite films, and the crystallinity fluctuated with the change of CNCs additive amount. Compared with the RCNCs, SCNCs had a better improve ability to the thermal stability of the composite films by promoting pyrolysis temperature 60-80 °C. On the contrary, the maximum mechanical properties of the composite films of RCNCs were much higher than those of SCNCs, and the Young's modulus of the PVA/RCNCs composite film were increased by 120.97 % in comparison with the pure PVA.

Preparation and characterization of spherical cellulose nanocrystals with high purity by the composite enzymolysis of pulp fibers.

The spherical cellulose nanocrystals (CNCs) with high purity were prepared, the processes included composite enzymolysis of pulp fibers and the purification of product. The impurities in the crude product CNCs were analyzed with FTIR, coomassie brilliant blue-G250 and ionic chromatography. The pure CNCs were characterized with SEM, XRD, DLS and TGA. The results indicated that the crude CNCs was flocculated and washed twice with a dilute acid solution (pH = 2) to get pure spherical CNCs, the purity was approximate 99.99%. The obtained pure spherical CNCs had a narrow particle size distribution with diameter 15-40 nm. FTIR and XRD analyses proved that the crystal phase of the spherical CNCs did not change, but the crystallinity decreased slightly compared with pulp fibers. The thermal degradation showed that the spherical CNCs had better thermal stability than one from other methods, and the temperature of maximum weight loss rate (Tmax) was 329.2 °C.

Preparation and characterization of the ribbon-like cellulose nanocrystals by the cellulase enzymolysis of cotton pulp fibers.

The enzymolytic preparation of cellulose nanocrystals (CNCs) has the unique advantages due to its green chemistry process. In this work, the cotton pulp fibers were enzymolyzed with the cellulase to prepare the ribbon-like CNC, and the samples were characterized by SEM, FTIR, XRD and DLS. The results indicated the CNC with the length 250-900 nm and width 30-45 nm could be produced from cotton pulp fibers at the lower cellulase concentration, the time 5-11 h and temperature 50 ºC. When the cellulase concentration rose up to 100 /ml, the granular CNC appeared, and at 300 µ/ml all of the formed CNC were granular. FTIR and XRD analyses proved that the ribbon-like CNC had the same crystal style and chemical structure with original cotton pulp fibers, but its crystallinity was weakened slightly. Despite the fact that there are the weakened crystallinity and aggregates, the as-prepared samples were still called as CNCs for simplicity. In addition, the article has discussed the mechanism for the forming ribbon-like CNC from the enzymolysis of cotton pulp fibers.

Preparation and characterization of the spherical nanosized cellulose by the enzymatic hydrolysis of pulp fibers.

In this work, the pulp fibers were enzymolyzed to prepare the nanosized cellulose (NC). The as-prepared samples were characterized by optical microscopy, electron microscopy, and Raman spectra. The experimental results indicated that enzymatic hydrolysis of pulp fibers could produce the spherical NC with a mean particle size of about 30nm, which had the excellent monodispersity and uniformity. When the concentration of complex enzymes was 20u/mL (cellulase: xylanase=9: 1), the yield of NC was 13.6%. The single cellulase was used, even if the enzyme concentration reached up to 200u/mL, only a mixture of strip and granular flocculation were obtained. The positive synergistic effect between xylanase and cellulase could be due to the enzymolysis of hemicellulose located on the cellulose microfibers to be favorable of cutting and splitting of the microfibers by the endoglucanase in cellulase.

Geodesic Video Stabilization in Transformation Space.

We present a novel formulation of video stabilization in the space of geometric transformations. With the setting of the Riemannian metric, the optimized smooth path is cast as the geodesics on the Lie group embedded in transformation space. While solving the geodesics has a closed-form expression in a certain space, path smoothing can be easily implemented by using geometric interpolation, rather than optimizing any space-time energy function. Specially, by using the geodesic solution in the space of rigid transformations, our approach even gains speedup 10× faster than state-of-the-art methods for path smoothing and motion compensation, and guarantees no extra distortion drawn into the stabilized frames. The experiments demonstrate the efficiency and effectiveness of our algorithm on stabilizing a variety of shaky videos.

Extracellular matrix metalloproteinase inducer (EMMPRIN) is present in smooth muscle cells of human aneurysmal aorta and is induced by angiotensin II in vitro.

The aim of the present study was to determine whether EMMPRIN (extracellular matrix metalloproteinase inducer) is present and is up-regulated in human aneurysmal aortas, and to assess a possible association with AngII (angiotensin II)-induced aneurysm formation. The presence of EMMPRIN was assessed in 41 surgical specimens from patients with a TAA (thoracic aortic aneurysm) (Type A aortic dissection, n=12; Type B aortic dissection, n=7; and TAA without dissection, n=7) or an AAA (abdominal aortic aneurysm, n=15) by immunohistochemistry. EMMPRIN expression in aortic aneurysm tissues was compared with 12 aortas obtained during autopsy (free of any vascular diseases), and scored for both staining intensity and the percentage of vascular cells stained. EMMPRIN protein levels in cultured human aortic SMCs (smooth muscle cells) following stimulation of AngII were analysed by Western blotting. Significant EMMPRIN immunoreactivity was detected in aortic aneurysm lesions from patients with TAAs and AAAs. In the aneurysmal wall, alpha-actin-positive SMCs were the main source of EMMPRIN. The frequency of EMMPRIN overexpression was significantly higher (P=0.026) in TAAs with dissection (68.4%) than TAAs without dissection (14.3%). AngII stimulation up-regulated the expression of EMMPIRN in cultured human aortic SMCs, which was suppressed by the addition of the AT1R (AngII type 1 receptor) antagonist losartan. In conclusion, the present study is the first to report the expression of EMMPRIN in aortic aneurysmal diseases, and we speculate that EMMPRIN may be important in the pathogenesis of these diseases. Whether these abnormalities are potential therapeutic targets deserve further investigation.