An agarose-based TOCN-ECM bilayer lyophilized-hydrogel with hemostatic and regenerative properties for post-operative adhesion management

This study used a unique approach by developing a bilayer system that can simultaneously accomplish non-adhesion, hemostatic, and tissue regenerative properties. In this system, agarose was used as a carrier material, with an agarose-TEMPO-oxidized cellulose nanofiber (TOCN), (AT) layer acting as a non-adhesion layer and an Agarose-Extracellular matrix, (AE) layer acting as a tissue regenerative layer. Thrombin was loaded on the AE layer as an initiator of the healing process, by hemostasis. AT 1:4 showed 79.3 % and AE 1:4 showed 84.66 % cell viability initially confirming the biocompatible nature of the layers. The AE layer showed cell attachment and proliferation on its surface whereas on the AT layer, cells are visible but no attachment was observed. Furthermore, in vivo analysis was conducted. The non-adhesive layer was grafted between the cecum and peritoneal wall which showed that (AT 1:4) displayed remarkable non-adhesion properties as compared to a commercial product and the non-treated group. Hemostasis and tissue regeneration ability were evaluated using rat liver models. The bleeding time of AE 1:4TH was recorded as 160 s and the blood loss was 5.6 g. The results showed that (AE 1:4) displayed effective regeneration ability in the liver model after two weeks.

Nano cellulose-laden alginate/chitosan sponge with enhanced biological and hemostatic behavior

Present study describes about hybrid hemostat developed with alginate (Alg), chitosan (Chito) and TEMPO-oxidized nanofibrillar cellulose (TOCNF) via lyophilization. All samples were analyzed under scanning electron microscopy (SEM) to determine their microstructure, size, and distribution of pores. Cell viability and proliferation of the scaffolds tested using fibroblast type L929 cells, showed it to be an excellent medium for cell generation. Blood coagulation started in ∼7.5 min, and most of the fibrin network formation took place in the Alg-Chito-TOCNF sponge, making it a suitable hemostatic material.

Highly Flexible, Self-Bonding, Self-Healing, and Conductive Soft Pressure Sensors Based on Dicarboxylic Cellulose Nanofiber Hydrogels

Conductive hydrogels have gained a great deal of interest in the flexible electronics industry because of their remarkable inherent properties. However, a significant challenge remains for balancing hydrogel's conductivity, self-healing, and strength properties. Herein, double network ionic hydrogels were fabricated by concurrently introducing borax into dicarboxylic cellulose nanofiber (DCNFs) and polyacrylamide (PAM) hydrogels. The incorporation of borax provided a superabsorbent feature to the PAM/DCNF hydrogels (without borax) with the equilibrium water absorption rate increased from 552 to 1800% after 42 h. The compressive strength of the prepared hydrogel was 935 kPa compared to 132 kPa for the PAM hydrogel, with high cycling stability (stable after 1000 compression cycles with 50% strain). The hydrogel pressure sensor had a very sensitive response (gauge factor = 1.36) in the strain range from 10 to 80%, which made it possible to detect mechanical motion accurately and reliably. The developed hydrogels with high-performance, environmentally friendly properties are promising for use in future artificial skin and human-machine interface applications.

Ice-Crystal-Templated "Accordion-Like" Cellulose Nanofiber/MXene Composite Aerogels for Sensitive Wearable Pressure Sensors

Exfoliated MXene nanosheets are integrated with cellulose nanofibers (CNFs) to form composite aerogels with high electric conductivity. The combination of CNFs and MXene nanosheets forms a unique "accordion-like" hierarchical architecture with MXene-CNF pillared layers through ice-crystal templating. Benefiting from the special "layer-strut" structure, the MXene/CNF composite aerogels have low density (50 mg/cm³), excellent compressibility and recoverability, as well as superior fatigue resistance (up to 1000 cycles). When being used as a piezoresistive sensor, the composite aerogel exhibits high sensitivity upon different strains, stable sensing performance with various compressive frequencies, broad detection range, and quick responsiveness (0.48 s). Moreover, the piezoresistive sensors are shown to have an excellent real-time sensing ability for human motions such as swallowing, arm bending, walking, and running. The composite aerogels also have a low environmental impact with the natural biodegradability of CNFs. The designed composite aerogels can serve as a promising sensing material for developing next-generation sustainable and wearable electronic devices.

Carbonized Cellulose Nanofibril with Individualized Fibrous Morphology: toward Multifunctional Applications in Polycaprolactone Conductive Composites

Drying cellulose nanofibril (CNF) from aqueous suspensions often leads to aggregated fibril morphology, negatively affecting its performance in ensuing applications. In this work, we introduced a new solvent drying approach to acquire dry CNF from aqueous suspensions and subsequently pyrolyzed the CNF precursor to obtain carbonized CNF (CCNF) without loss of its fibrous morphology. The fibrous CCNF was dispersed homogeneously in polycaprolactone (PCL) thermoplastic resin, greatly enhancing PCL composite tensile performance. After being further mixed with carbon black (CB), the CCNF helped to minimize CB aggregation due to formation of interconnected three-dimensional (3D) structures. The CCNF/CB/PCL composite exhibited superior electrical conductivity ascribed to electrons transporting more efficiently among CB aggregates. The composite is also suitable for applications such as 3D printed electromagnetic interference (EMI) shielding and deformation sensing. Specifically, the 3D printed EMI shielding composite efficiently absorbed EM radiation in the frequency range of 4-26 GHz, and the 3D printed deformation sensor exhibited excellent sensitivity, durability, and flexibility in monitoring mechanical distortions. Herein, this study sheds light on the development of multifunctional conductive composites embedded with fibrous CCNF from sustainable resources.

Poly(acryloyl hydrazide)-grafted cellulose nanocrystal adsorbents with an excellent Cr(VI) adsorption capacity

In this study, we prepared poly(acryloyl hydrazide) (PAH)-grafted cellulose nanocrystal (CNC-PAH) particles via the atom transfer radical polymerization method for application to Cr(VI) adsorption. The closely-packed PAH chains grafted on the cellulose nanocrystal (CNC) surface provide a high density of amine groups that can adsorb Cr(VI) through strong electrostatic, hydrogen bonding and chelating interactions. CNC-PAH exhibited the optimum Cr(VI) adsorption capacity at the solution pH = 3, where its electrostatic attraction with Cr(VI) was maximized. Cr(VI) was chemisorbed in CNC-PAH by following the Langmuir isotherm mechanism (homogeneous monolayer adsorption). The Cr(VI) adsorption kinetics of CNC-PAH was controlled predominantly by intra-particle diffusion resistance imparted by the PAH shell layer. Thermodynamic analysis revealed that Cr(VI) adsorption of CNC-PAH is a spontaneous and endothermic process. Importantly, CNC-PAH grafted with the higher M_w (∼50 kg mol^-1) PAH exhibited a rapid Cr(VI) adsorption rate and remarkably high Cr(VI) adsorption capacity (∼457.6 mg g^-1 at 298.15 K), exceeding those of previously reported adsorbents owing to its numerous Cr(VI)-adsorptive amine groups provided by the closely-packed grafted PAH polymers. Furthermore, CNC-PAH showed excellent reusability to maintain its high adsorption ability during repeated adsorption-desorption cycles owing to the covalently binding nature of the PAH polymers.

Effects of Methylenediphenyl 4,4'-Diisocyanate and Maleic Anhydride as Coupling Agents on the Properties of Polylactic Acid/Polybutylene Succinate/Wood Flour Biocomposites by Reactive Extrusion

Polylactic acid (PLA)/polybutylene succinate (PBS)/wood flour (WF) biocomposites were fabricated by in situ reactive extrusion with coupling agents. Methylenediphenyl 4,4'-diisocyanate (MDI) and maleic anhydride (MA) were used as coupling agents. To evaluate the effects of MDI and MA, various properties (i.e., interfacial adhesion, mechanical, thermal, and viscoelastic properties) were investigated. PLA/PBS/WF biocomposites without coupling agents revealed poor interfacial adhesion leading to deteriorated properties. However, the incorporation of MDI and/or MA into biocomposites showed high performances by increasing interfacial adhesion. For instance, the incorporation of MDI resulted in improved tensile, flexural, and impact strengths and an increase in tensile and flexural modulus was observed by the incorporation of MA. Specially, remarkably improved thermal stability was found in the PLA/PBS/WF biocomposites with 1 phr MDI and 1 phr MA. Also, the addition of MDI or MA into biocomposites increased the glass transition temperature and crystallinity, respectively. For viscoelastic property, the PLA/PBS/WF biocomposites with 1 phr MDI and 1 phr MA achieved significant enhancement in storage modulus compared to biocomposites without coupling agents. Therefore, the most balanced performances were evident in the PLA/PBS/WF biocomposites with the hybrid incorporation of small quantities of MDI and MA.

Silver-Incorporated Nanocellulose Fibers for Antibacterial Hydrogels

A free-standing, antibacterial hydrogel was fabricated using silver-nanoparticle-immobilized cellulose nanofibers (CNFs) and alginate. Surface hydroxyl groups of CNFs were oxidized to carboxylate groups using (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TCNF), followed by the treatment with silver nitrate solution for surface adsorption of silver ions. In situ reduction of silver ions to produce silver nanoparticles was performed for the silver-adsorbed CNFs. Electron microscopy, X-ray diffraction, and spectroscopic analysis revealed that higher amounts of silver nanoparticles were immobilized on the surface of TCNF than on the surface of native CNF. Silver-nanoparticle-immobilized TCNF was embedded in alginate gels and silver ions from the matrix were slowly released for 7 days. Silver-nanoparticle-loaded alginate gels showed comparable antibacterial activity to silver-ions-loaded alginate gels, although the former showed a significantly lower cytotoxicity against animal cells. Thus, the antibacterial gels can potentially be applied to various skin surfaces to prevent bacterial infection while minimizing skin damage.

Effects of rigidity of an internal fixation device. A comprehensive biomechanical investigation

Internal fixation with instrumentation often accompanies surgical fusion to augment spinal stability, provide temporary fixation while the surgical fusion mass unites, and enhance postoperative mobilization of a patient. Some surgeons, however, feel that the existing plate-screw designs are too rigid and are the primary cause of "iatrogenic" adverse effects clinically observed. A three-part study, involving in vitro experimental protocol, analytical finite-element-based models, and an in vivo canine investigation, was undertaken to study the role of decreasing rigidity of a device on the biomechanical response of the stabilized segments. Two alternatives--the use of one variable screw placement (Steffee plate [unilateral, 1VSP model]) as opposed to two VSP plates (bilateral, 2VSP model) and two VSP plates with polymer washers placed in between the integral nut and plate (2MVSP model)--were considered for achieving a reduction in the rigidity of the conventional VSP system. The load-displacement data obtained from the in vitro experiments and the stress distributions within the stabilized and intact models predicted by the finite-element models revealed that the unilateral VSP system is less rigid and is likely to reduce stress shielding of the vertebral bodies compared with the 2VSP model. The undesirable effects associated with the use of the 1VSP plate system are the presence of coupled motions due to the inherent asymmetry and the likely inability to provide enough rigidity for decompression procedures requiring a complete excision of the disc. The use of two MVSP plates overcomes these deficiencies.(ABSTRACT TRUNCATED AT 250 WORDS)