Fubao Xing

Preparation of aligned porous gelatin scaffolds by unidirectional freeze-drying method

Porous gelatin scaffolds with microtubule orientation structure were manufactured by unidirectional freeze-drying technology, and their porous structure was characterized by scanning electron microscopy. Scaffolds with tunable pore size and high porosity up to 98% were obtained by adjusting the concentration of the gelatin solution and crosslinking agent during the preparation process. All the porous gelatin scaffolds exhibited oriented microtubule pores, with width and length from 50 to 100 microm and 100 to 500 microm, respectively. Meanwhile, the properties of the scaffolds, such as porosity, water adsorption ability and compressive strength, were studied. In vitro enzymatic degradation results showed that the absolute weight loss of the gelatin scaffolds exhibited an increasing trend from low to high gelatin concentration used to prepare gelatin scaffolds; in vitro cell culture results indicated that the porous gelatin scaffolds were non-toxic to cartilage cells, since the cells spread and grew well.

Factors that Affect Pickering Emulsions Stabilized by Graphene Oxide

Stable Pickering emulsions were prepared using only graphene oxide (GO) as a stabilizer, and the effects of the type of oil, the sonication time, the GO concentration, the oil/water ratio, and the pH value on the stability, type, and morphology of these emulsions were investigated. In addition, the effects of salt and the extent of GO reduction on emulsion formation and stability were studied and discussed. The average droplet size decreased with sonication time and with GO concentration, and the emulsions tended to achieve good stability at intermediate oil/water ratios and at low pH values. In all solvents, the emulsions were of the oil-in-water type, but interestingly, some water-in-oil-in-water (w/o/w) multiple emulsion droplets were also observed with low GO concentrations, low pH values, high oil/water ratios, high salt concentrations, or moderately reduced GO in the benzyl chloride-water system. A Pickering emulsion stabilized by Ag/GO was also prepared, and its catalytic performance for the reduction of 4-nitrophenol was investigated. This research paves the way for the fabrication of graphene-based functional materials with novel nanostructures and microstructures.

An environmentally friendly method for the fabrication of reduced graphene oxide foam with a super oil absorption capacity

Three kinds of graphene oxide (GO) foams were fabricated using different freezing methods (unidirectional freezing drying (UDF), non-directional freezing drying, and air freezing drying), and the corresponding reduced graphene oxide (RGO) foams were prepared by their thermal reduction of those GO foams. These RGO foams were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The absorption process and the factors that influence the absorption capacity were investigated. The RGO foams are hydrophobic and showed extremely high absorbing abilities for organic liquids. The absorption capacity of the RGO foams made by UDF was higher than 100 g g(-1) for all the oils tested (gasoline, diesel oil, pump oil, lubricating oil and olive oil) and had the highest value of about 122 g g(-1) for olive oil. The oil absorption capacity of the GO foams was lower than that of the RGO foams, but for olive oil, the absorption capacity was still high than 70 g g(-1), which is higher than that of most oil absorbents.

Porous graphene oxide/carboxymethyl cellulose monoliths, with high metal ion adsorption.

Orderly porous graphene oxide/carboxymethyl cellulose (GO/CMC) monoliths were prepared by a unidirectional freeze-drying method. The porous monoliths were characterized by Fourier transform infrared spectra, X-ray diffraction and scanning electron microscopy. Their properties including compressive strength and moisture adsorption were measured. The incorporation of GO changed the porous structure of the GO/CMC monoliths and significantly increased their compressive strength. The porous GO/CMC monoliths exhibited a strong ability to adsorb metal ions, and the Ni(2+) ions adsorbed on GO/CMC monolith were reduced by NaBH4 to obtain Ni GO/CMC monolith which could be used as catalyst in the reduction of 4-nitrophenol to 4-aminophenol. Since CMC is biodegradable and non-toxic, the porous GO/CMC monoliths are potential environmental adsorbents.

Zeolite/Polymer Composite Hollow Microspheres Containing Antibiotics and the In Vitro Drug Release

Hemorrhage remains a leading cause of early death after trauma, especially those with infectious complications in combat wounds. The aim of this study was to develop antibiotics-loaded zeolite (Zel)/polymer composites for hemostatic materials. The composite materials were fabricated from zeolite and various biodegradable polymers, including chitosan (CS), gelatin (Gel) and alginate (Alg), using the inversed emulsion method. The morphology of the composites was observed by SEM, and the results showed that the prepared Zel/polymer composites can form hollow microspheres under appropriate conditions. The microspheres contained three sizes of pores, nano-pore of zeolite, micrometer-sized pores between zeolite particles, and void cores having a size of tens of micrometers. It was these pores that made the composites have unexpected water-absorbing capacity. When antibiotics were loaded into the composite microspheres, they exhibited a prolonged drug-releasing period. Thus, we can make full use of the characteristics of chitosan, zeolite and antibiotics to create potential dual-functional hemostatic materials.

Fabrication of Chitosan Scaffolds with Tunable Porous Orientation Structure for Tissue Engineering.

Chitosan, as an example of natural macromolecular biomaterials, was used to fabricate highly porous chitosan scaffolds with microtubules having a tubular orientation structure using the unidirectional freeze-drying method. The porous structure of the scaffolds was characterized via scanning electron microscopy. The factors that affect the porous structure of the scaffolds, such as the concentration of chitosan solution and addition of glutaraldehyde as cross-linking agent, have been extensively studied in order to find a facile and efficient way to control the porosity, tubular morphology and orientation of the microtubules. The properties of the chitosan scaffolds, including water absorption ability, compressive strength, protein adsorption and in vitro enzymatic biodegradation in the presence of lysozyme, were also investigated. In vitro cell-culture results showed that the chitosan scaffold was non-toxic to cartilage cells and the cells could spread and grow well on the scaffolds.

Porous CS monoliths and their adsorption ability for heavy metal ions

Highly porous chitosan (CS) monoliths were prepared by a unidirectional freeze-drying method and the adsorption performance of the monoliths for metal ions in aqueous solution was evaluated. The porous CS monoliths have excellent adsorption for a range of metal ions. The effect of the amount of porous CS monoliths, the pH, the adsorption time, the amount of the cross-linking agent, and the amount of disodium ethylenediamine tetraacetate (EDTA) on the saturated adsorption efficiency (Ade) were determined. The pH had the greatest influence on the adsorption behavior. Under optimal conditions (C(CU²⁺) = 800 mg/L, pH 6, and cross-linking agent = 0.15%) for the CS monoliths, the Ade for Cu(2+) exceeded 99%, and the saturated adsorption capacity (Q(s)) reached a value of 141.8 mg/g (2.23 mmol/g) in 4h. Moreover, the addition of EDTA can both increase the Q(s) and shorten the time that achieved the level. If EDTA was added, this level was achieved in 2h. The porous CS monoliths can be regenerated by soaking them in acid and their Ade is maintained.

Molecularly imprinted photonic crystals for the direct label-free distinguishing of L-proline and D-proline

Novel molecularly imprinted photonic crystals (IPCs) for the highly sensitive label-free detection of L-proline and for the chiral recognition of L/D-proline were reported. A series of L-proline imprinted polyacrylamide photonic crystals (PAM-LPIPCs) and poly(acrylamide-co-acrylic acid) photonic crystals (PAM-co-AA-LPIPCs) were fabricated via the in situ polymerization of polystyrene opal. The PAM-LPIPCs exhibit good molecular response in L-proline solutions and can be visualized by the naked eye much like a pH test paper. The concentration of imprinted molecules (L-proline) in aqueous solution can be detected by the chromatic signal (structural color) or the optical signal (λmax). Furthermore, the responsivity and sensitivity of the PAM-co-AA-LPIPCs can be improved by increasing the amount of the imprinted content or the proportion of AA, or by decreasing the ratio of the cross-linking agent. When all these factors were balanced, a PAM2-co-AA0.4-LP0.5 IPC with good strength, high responsivity, high sensitivity and specific molecular recognition was obtained. It is found that the presented crystals can show obvious response to L-proline solution even at a low concentration of 1%. The PAM2-co-AA0.4-LP0.5 IPC not only very selectively distinguishes between L-proline and nicotinic acid, but it is also good at chiral recognition between L-proline and D-proline. What is more, the response is rapid and reversible and the IPC is recyclable.

Antibiotic-containing biodegradable bead clusters with porous PLGA coating as controllable drug-releasing bone fillers.

The construction of inorganic bone fillers with a suitable degradation period to match the new bone growth is an urgent task since most bone fillers have an either too fast or slow degradation rate. Calcium sulfate, as a commonly used implanting material, shows good biocompatibility, biodegradability, osteoconductivity and mechanical properties. However, its degradation rate and the drug-release rate are too rapid to meet the requirements for clinical application. In this paper, calcium sulfate bead clusters (CSBC), with or without loaded drug, were prepared; and two kinds of coatings, porous or nonporous, were deposited on the surface of the beads to extend the degradation and the drug release period. The results show that poly(lactic acid-glycolic acid) (PLGA) coatings, incorporated with different porogens can form in situ porous coatings that obviously lengthen the degradation period of the beads from 30 days to around 60–90 days. Consequently, the drug-release rate was significantly reduced, and the release period increased from about 10 days to over 50 days.

A facile method to prepare reduced graphene oxide with nano-porous structure as electrode material for high performance capacitor

A facile method to prepare reduced graphene oxide (M-rGO) nanosheets with enhanced electrochemical performance has been established by using Mg powder as the reductant. The structural, morphological and electrochemical properties of the M-rGO have been characterized. The prepared M-rGO possesses well-developed nano-porous structure and superior surface characteristics. Electrochemical analyses show that the M-rGO has a maximum specific capacitance of 577.4 F g−1 at the scan rate of 1 mV s−1, and an excellent rate performance of 324.9 F g−1 at 1 V s−1. The CV curves of M-rGO can keep rectangular in shape even at a scan rate of 500 mV s−1 without obvious distortion. Such outstanding electrochemical performances of M-rGO can be attributed to both the presence of nano-pores in M-rGO and the pseudocapacitance arising from residual oxygen-containing functional groups.