Monodispersed Renewable Particles by Cascade and Density Gradient Size Fractionation to Advance Lignin Nanotechnologies.

Control over particle size and shape heterogeneity is highly relevant to the design of photonic coatings and supracolloidal assemblies. Most developments in the area have relied on mineral and petroleum-derived polymers that achieve well-defined chemical and dimensional characteristics. Unfortunately, it is challenging to attain such control when considering renewable nanoparticles. Herein, a pathway toward selectable biobased particle size and physicochemical profiles is proposed. Specifically, lignin is fractionated, a widely available heterogeneous polymer that can be dissolved in aqueous solution, to obtain a variety of monodispersed particle fractions. A two-stage cascade and density gradient centrifugation that relieves the need for solvent pre-extraction or other pretreatments but achieves particle bins of uniform size (~60 to 860 nm and polydispersity, PDI<0.06, dynamic light scattering) along with characteristic surface chemical features is introduced. It is found that the properties and associated colloidal behavior of the particles are suitably classified in distinctive size populations, namely, i) nanoscale (50-100 nm), ii) photonic (100-300 nm) and iii) near-micron (300-1000 nm). The strong correlation that exists between size and physicochemical characteristics (molar mass, surface charge, bonding and functional groups, among others) is introduced as a powerful pathway to identify nanotechnological uses that benefit from the functionality and cost-effectiveness of biogenic particles.

Formation and Identification of Lignin-Carbohydrate Complexes in Pre-hydrolysis Liquors.

The lignin-carbohydrate complexes (LCCs) typically present in the liquors produced in the pre-hydrolysis of biomass cause severe difficulties in downstream fractionation. To address this issue, a series of LCC samples were accessed from solutions obtained from the pre-hydrolysis of extractive-free pine wood meal (H-LCC) and compared with LCC obtained from the corresponding residues (B-LCC). Chromatographic and spectroscopic techniques revealed that 8.2% of the lignins were degraded at 160 °C, resulting from the breakage of ß-O-4' linkages during pre-hydrolysis. Meanwhile, (reactive) hemicelluloses were mainly removed from the fibers' cell walls. Some hemicelluloses in the pre-hydrolysis liquor, such as glucomannans, were associated with degraded lignin fragments via ether and ester bonds. However, the newly formed LCCs were pH-labile and underwent rapid hydrolysis. Overall, we reveal details about LCC formation and degradation during pre-hydrolysis at given temperatures, critically important in efforts to improve biomass processing and valorization.

Composites based on electrospun fibers modified with cellulose nanocrystals and SiO2 for selective oil/water separation.

Membranes for water remediation require structural stability, efficient operation, and durability. In this work, we used cellulose nanocrystals (CNC) to reinforce hierarchical nanofibrous membranes based on polyacrylonitrile (PAN). Hydrolysis of the electrospun nanofibers (H-PAN) enabled hydrogen bonding with CNC and provided reactive sites for grafting cationic polyethyleneimine (PEI). In a further modification, anionic silica particles (SiO2) were adsorbed on the fiber surfaces, obtaining CNC/H-PAN/PEI/SiO2 hybrid membranes, which developed swelling resistance (swelling ratio of 6.7 compared to 25.4 measured for a CNC/PAN membrane). Hence, the introduced hydrophilic membranes contain highly interconnected channels, they are non-swellable and exhibit mechanical and structural integrity. By contrast with untreated PAN membranes, those obtained after modification displayed high structural integrity and allowed regeneration and cyclic operation. Finally, wettability and oil-in-water emulsion separation tests demonstrated remarkable oil rejection and separation efficiency in aqueous media.

Locust bean gum adsorption onto softwood kraft pulp fibres: isotherms, kinetics and paper strength.

The adsorption of locust bean gum (LBG) onto Northern Bleached Softwood Kraft (NBSK) pulp improved paper tensile and burst strength and lowered refining energy by strengthening inter-fibre bonding. Adsorption kinetics and isotherms were investigated to develop a fundamental understanding of the adsorption mechanism. The adsorption rate followed pseudo-second-order kinetics and the activation energy was 99.34 kJ·mol-1, suggesting chemisorption. The adsorption rate constant increased rapidly with temperature from 25 to 45 °C (k = 1.93 to 24.03 g·mg-1·min-1), but the amount adsorbed at equilibrium decreased (q e = 1.91 to 0.48 mg·g-1 o.d. fibre). LBG adsorption to NBSK at 25 °C was consistent with the Langmuir adsorption model for LBG < 2.1 wt% of o.d. fibre, suggesting reversible, homogenous adsorption to a finite number of sites on the fibre surface. Refining to 3000 rev increased the heterogeneity of the NBSK pulp surface leading to multi-layer Freundlich adsorption with adsorption constant n = 5.00, and the equilibrium constant K f = 2.57 mg·g-1·(mg·L-1)-1/n at 25 °C. Favorable adsorption conditions for negatively charged LBG were identified: 25 °C for 10 min, low dosage level (< 2 wt%), lightly refined (< 3000 rev) NBSK pulp at low fibre consistency (< 0.5 wt%), high agitation rate (> 150 r.p.m.), acidic or neutral conditions (pH 2-7) without salt addition. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10570-021-04133-w.

Improved biphasic calcium phosphate combined with periodontal ligament stem cells may serve as a promising method for periodontal regeneration.

The study aimed to investigate if a construct of porous improved biphasic calcium phosphate (BCP) combined with osteogenically induced periodontal ligament stem cells (PDLSCs) could repair periodontal defect. Human PDLSCs were cultured, identified, and osteogenically induced, and then seeded on the improved BCP, assessed by scanning electron microscopy and MTT method. Afterwards, PDLSC-seeded scaffolds were used in six Beagle dogs' alveolar bone dehiscence model, and new bone formation was assessed by three-dimensional micro-computed tomographic imaging, fluorescence, and light microscopy at 4th, 8th and 12th week postoperatively. Results showed that PDLSCs were positive for STRO-1 and vimention, while negative for cytokeratin. They had the capacity to undergo osteogenic differentiation in vitro. When seeded on the improved BCP, PDLSCs exhibited significantly great viability. The use of PDLSC-seeded improved BCP promoted effective periodontal regeneration. In conclusion, this study demonstrates the potential of improved BCP combined with PDLSCs as a promising method for periodontal regeneration.