A nanobursa mesh: a graded electrospun nanofiber mesh with metal nanoparticles on carbon nanotubes.

A new type of material, a "nanobursa" mesh (from "bursa" meaning "sac or pouch"), is introduced. This material consists of sequential layers of porous polymeric nanofibers encapsulating carbon nanotubes, which are functionalized with different metal nanoparticles in each layer. The nanobursa mesh is fabricated via a novel combination of twin-screw extrusion and electrospinning. Use of this hybrid process at industrially-relevant rates is demonstrated by producing a nanobursa mesh with graded layers of Pd, Co, Ag, and Pt nanoparticles. The potential use of the fabricated nanobursa mesh is illustrated by modeling of catalytic hydrocarbon oxidation.

Shell-core bi-layered scaffolds for engineering of vascularized osteon-like structures.

Bottom-up assembly of osteon-like structures into large tissue constructs represents a promising and practical strategy toward the formation of hierarchical cortical bone. Here, a unique two-step approach, i.e., the combination of electrospinning and twin screw extrusion (TSE) techniques was used to fabricate a microfilament/nanofiber shell-core scaffold that could precisely control the spatial distribution of different types of cells to form vascularized osteon-like structures. The scaffold contained a helical outer shell consisting of porous microfilament coils of polycaprolactone (PCL) and biphasic calcium phosphates (BCP) that wound around a hollow electrospun PCL nanofibrous tube (the core). The porous helical shell supported the formation of bone-like tissues, while the luminal surface of nanofibrous core enabled endothelialization to mimic the function of Haversian canal. Culture of mouse pre-osteoblasts (POBs, MC 3T3-E1) onto the coil shells revealed that coils with pitch sizes greater than 135 µm, in the presence of BCP, favored the proliferation and osteogenic differentiation of POBs. The luminal surface of PCL nanofibrous core supported the adhesion and spreading of mouse endothelial cells (ECs, MS-1) to form a continuous endothelial lining with the function similar to blood vessels. Taken together, the shell-core bi-layered scaffolds with porous, coil-like shell and nanofibrous tubular cores represent a new scaffolding technology base for the creation of osteon analogs.

Biomass pretreatment strategies via control of rheological behavior of biomass suspensions and reactive twin screw extrusion processing.

Twin screw extrusion based pretreatment of biomass is an attractive option due to its flexibility to carry out chemical reactions under relatively high stresses, temperatures and pressures. However, extrusion processes are rarely utilized in biomass pretreatment because such processing is constrained by rheological behavior of typical biomass suspensions. Without the manipulation of their rheological behavior, biomass suspensions become unprocessable within the extruder at modest biomass concentrations. Here it is demonstrated that gelation agents can render biomass suspensions processable. Specifically, carboxy methyl cellulose, CMC, could be used in conjunction with alkaline pretreatment of hardwood-type biomass and enabled separation of lignin from cellulose fibers. Furthermore, recycled black liquor, obtained upon pretreatment, was determined to be as effective as CMC for rendering biomass suspensions flowable by again facilitating the concomitant application of high shearing stresses and chemical treatment for the pretreatment of the biomass in the twin screw extruder.

Evaluation of the treatment of chromite ore processing residue by ferrous sulfate and asphalt.

The effectiveness of the treatment of chromite ore processing residue (COPR) with ferrous sulfate and encapsulation into asphalt were explored separately and in combination. The asphalt treatment was conducted by mixing COPR or ferrous sulfate pretreated COPR with varying amounts of asphalt. To assess the efficacy of the treatment, the leachability of toxicity characteristic leaching procedure (TCLP) total chromium (Cr) from all treated samples was determined for curing periods up to 16 months. X-ray absorption near edge structure (XANES) analyses were also performed to evaluate the Cr(6+) concentration in the selected samples. The combination treatment of ferrous sulfate and the encapsulation of the treated COPR into asphalt reduced the TCLP total Cr concentration to lower than the regulatory limit of 5mg/L for Cr contaminated soils, after 16 months. However, the Cr concentrations were still higher than the universal treatment standards (UTS) of 0.6 mg/L for hazardous waste. On the other hand, treatment with ferrous sulfate alone or the encapsulation of the COPR in asphalt failed to meet the TCLP total Cr concentration of 5mg/L, after 16 months. XANES analyses results showed that more than 75% Cr(6+) reduction was achieved upon pretreatment with ferrous sulfate.