Acid Leaching Vermiculite: A Multi-Functional Solid Catalyst with a Strongly Electrostatic Field and Brönsted Acid for Depolymerization of Cellulose in Water.

Vermiculite is a natural mineral. In this study, vermiculite and acid-activated vermiculite was used as a solid acid catalyst for the hydrolysis of cellulose in water. The catalysts were characterized by XRD, FT-IR, and BET. The effects of time, temperature, mass ratio and water amount on the reaction were investigated in the batch reactor. The results showed that the highest total reducing sugars (TRS) yield of 40.1% could be obtained on the vermiculite activated by 35 (wt)% H2SO4 with the mass ratio of catalyst to cellulose of 0.18 and water to cellulose of 16 at 478 K for 3.5 h. The acid-activated vermiculite was a stable catalyst through calcination at 628 K and the yield of TRS decreased to 36.2% after three times reuse. The results showed that the crystal structure of vermiculite was destroyed and the surface -OH groups increased after the acid treatment. However, the synergistic effect of a strongly electrostatic polarization and Brönsted acid was responsible for the efficient conversion of cellulose. The mechanism of cellulose hydrolysis on the acid-activated vermiculite was suggested. This work provides a promising strategy to design an efficient solid catalyst for the cellulose hydrolysis, and expands the use of vermiculite in a new field.

[Comparative studies on the material performances of natural bone-like apatite from different bone sources].

The compressive strength of the original bone tissue was tested, based on the raw human thigh bone, bovine bone, pig bone and goat bone. The four different bone-like apatites were prepared by calcining the raw bones at 800 degrees C for 8 hours to remove organic components. The comparison of composition and structure of bone-like apatite from different bone sources was carried out with a composition and structure test. The results indicated that the compressive strength of goat bone was similar to that of human thigh bone, reached (135.00 +/- 7.84) MPa; Infrared spectrum (IR), X-ray diffraction (XRD) analysis results showed that the bone-like apatite from goat bone was much closer to the structure and phase composition of bone-like apatite of human bones. Inductively Coupled Plasma (ICP) test results showed that the content of trace elements of bone-like apatite from goat bone was closer to that of apatite of human bone. Energy Dispersive Spectrometer (EDS) results showed that the Ca/P value of bone-like apatite from goat bone was also close to that of human bone, ranged to 1.73 +/- 0.033. Scanning electron microscopy (SEM) patterns indicated that the macrographs of the apatite from human bone and that of goat bone were much similar to each other. Considering all the results above, it could be concluded that the goat bone-like apatite is much similar to that of human bone. It can be used as a potential natural bioceramic material in terms of material properties.

Developing novel Ca-zeolite/poly(amino acid) composites with hemostatic activity for bone substitute applications.

The novel Ca-zeolite/poly(amino acid) (CaY/PAA) composites for bone substitute applications with hemostatic activity were prepared using the in situ melting polymerization method. In this study, Ca-zeolite (CaY) loaded with Ca2+ was obtained from Y-type zeolite (NaY) by ion-exchange method. The properties of the CaY/PAA composites and PAA, including composition, structure, compressive strength, in vitro degradability in phosphate-buffered solution (PBS), bioactivity, cytocompatibility and in vitro coagulation tests were characterized and investigated. The results showed that compressive strength of the CaY/PAA composites ranged from 145 to 186 MPa, demonstrating sufficient mechanical strength for load-bearing bone substitute. After soaking in PBS for 16 weeks, the weight loss of 25CaY/PAA and 50CaY/PAA were 4.1 and 1.6 wt%, respectively, and the pH values for CaY/PAA composites increased to about 8.0 in 2 weeks and then gradually stabilized around 7.4, indicating good stability in PBS. Scanning electron microscope and energy dispersive spectrometer results showed that the composites were bioactive and new apatite layers attached on their surfaces. Mesenchymal stem cells (MSCs) exhibited high-proliferation in the extract solution of the CaY/PAA composites and were well spread on the surfaces of the composites. Cells on the CaY/PAA composite groups showed higher alkaline phosphatase (ALP) activity indicating the potential to promote cell differentiation. The in vitro coagulation tests showed that CaY/PAA composites have shorter clotting time and better performance of promoting blood coagulation than other samples, presenting improved hemostatic activity. In summary, the results demonstrated that the CaY/PAA composites had good mechanical strength, stability, bioactivity, cytocompatibility and hemostatic activity for bone substitute applications.

Evaluation of absorbable hemostatic agents of polyelectrolyte complexes using carboxymethyl starch and chitosan oligosaccharide both in vitro and in vivo.

Absorbable hemostatic agents with a high hemostatic efficacy play an important role in surgical and severely traumatic hemostasis. In the present study, by applying polyelectrolyte assembly, polyelectrolyte complexes (PECs), using carboxymethyl starch (CMS) and chitosan oligosaccharide (COS), with controllable physicochemical properties were prepared and optimized for hemorrhage control. Particle size, zeta potential, morphology and water absorption of the PECs with different CMS/COS ratios were systematically evaluated. The results of in vitro degradation in PBS suggested that CMS/COS PECs were degradable and their degradation rates, which decreased with the increase of the COS content, were suitable for absorbable hemostatic agents. The in vivo hemostatic efficacy of the PECs with 10 wt% COS content (PEC 10), which was evaluated in a rabbit hepatic hemorrhage model, was better than CMS but decreased with the increase of the COS content. The plasma coagulation evaluation revealed that the PECs could significantly activate and accelerate the coagulation cascade through both the intrinsic and extrinsic pathways but could not directly affect the common pathway. CMS/COS PECs also showed antimicrobial activity against S. aureus, which enhanced with the increase of the COS content, but failed against E. coli. Moreover, PEC 10 displayed excellent cytocompatibility with MC3T3-L1 and good tissue compatibility in a rabbit liver model. These findings not only suggest that CMS/COS PECs with a suitable COS content were promising absorbable hemostatic agents for internal use but they are also useful to understand the underlying principles for designing PEC based hemostatic agents.