In situ forming hydrogel recombination with tissue adhesion and antibacterial property for tissue adhesive.

In situ forming hydrogels with strong adhesive strength and antibacterial activity are of great interest to serve as tissue adhesive in fields like wound dressing and mass hemorrhage. In this study, hybrid hydrogel (GOHA) based on gelatin and oxidized hyaluronic acid was developed and endowed with excellent mechanical strength and tissue adhesion. According to our results, GOHA hydrogel exhibits a fast gelation time of around 60 s, robust compression strength of 223.43 ± 24.28 kPa, and strong adhesion of 14.33 ± 0.78 kPa to porcine skin, which is much higher than that of commercial fibrin glue (around 1.00 kPa). Meanwhile, through the loading of levofloxacin, obvious antibacterial activity can be obtained for wider applications. Notably, it would not compromise the hemocompatibility and cytocompatibility in vitro. In summary, this kind of hybrid hydrogel shows great potential as tissue adhesive in biomedical fields.

Multi-Crosslinked Hydrogels with Instant Self-Healing and Tissue Adhesive Properties for Biomedical Applications.

Due to the defects like long gelling time, inferior mechanical properties and weak adhesion, in situ forming hydrogels are still restricted in biomedical applications like viscera rupture and targeted therapy. To address these problems, a new kind of multi-crosslinked hydrogel (G-OKG-DA) consisting of gelatin, oxidized konjac glucomannan (OKG), and dopamine (DA) is proposed in this study. The resulting hybrid hydrogel is endowed with a short gelling time (≈3 min) and injectable capacity. According to the mechanical and adhesive tests, G-OKG-DA hydrogel shows a robust tensile strength of 23.94 kPa, as well as a higher adhesive strength (≈150 kPa) than commercial fibrin glue. In addition, an instant self-healing behavior of G-OKG-DA hydrogel can be found, which is attributed to multi-cross-linking reactions including Schiff-based dynamic covalent bonds between OKG and gelatin, oxidative polymerization of DA, and catechol-mediated chemistry like Michael addition and DA-quinone coupling. Importantly, the multi-crosslinked hydrogel will not compromise its hemocompatibility and cytocompatibility in vitro, suggesting potential applications in biomedical fields as tissue adhesive and implants.

Genipin-crosslinked gelatin-based composite hydrogels reinforced with amino-functionalized microfibrillated cellulose.

Herein, a strong and stable gelatin-based composite hydrogel was fabricated by incorporation of amino-functionalized microfibrillated cellulose (AMFC) into gelatin matrix along with genipin crosslinking. The hydrogel consists of chemical and physical crosslinks among gelatin chains and AMFC fibrils. The morphology, swelling behavior and compressive properties of the composite hydrogels were investigated. The results show that the mechanical properties and structural stability of the gelatin hydrogels were improved remarkably by the addition of AMFC due to the formation of a hybrid network structure. The composite hydrogel has a compressive strength up to 1.52 MPa at a strain of 80 %, which is 41.2 and 1.8 times higher than that of the conventional physical and genipin-crosslinked gelatin hydrogels, respectively. Moreover, the developed gelatin-based composite hydrogels reinforced with AMFC exhibit good enzymatic stability, high surface hydrophobicity, tunable swelling property and excellent biocompatibility, which are expected to have potential applications in biomedical and pharmaceutical fields.

Green synthesis of silver nanoparticles using soluble soybean polysaccharide and their application in antibacterial coatings.

In the present work, a facile and green synthesis approach for the production of monodispersed, small-sized (2.9 ± 0.7 nm) and stable silver nanoparticles (AgNPs) using soluble soybean polysaccharide (SSPS) was reported. SSPS was used as the reducing and stabilizing agent. The obtained SSPS-stabilized AgNPs (SA) were characterized by UV-vis absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The antimicrobial activity of the SA colloidal dispersion (SACD) was evaluated based on the growth kinetics of bacteria E. coli and S. aureus. Afterwards, the colloidal dispersion was applied as a coating material to Kraft paper. The SACD-coated Kraft paper exhibited excellent antimicrobial activity against above bacteria strains and P. aeruginosa. The effects of SACD coating on surface wettability, barrier property and microstructure of the Kraft paper were also studied. The results suggested that the SSPS-stabilized AgNPs have great potential in antibacterial applications.

Preparation of gelatin-based hydrogels with tunable mechanical properties and modulation on cell-matrix interactions.

Natural polymer material-based hydrogels normally show inferior mechanical stability and strength to bear large deformation and cyclic loading, therefore their applications in food, biomedical and tissue engineering fields are greatly limited. In this study, gelatin-based hydrogels with remarkable stability, as well as tunable mechanical properties, were prepared via a facile method known as the Hofmeister effect. The higher concentration of potassium sulfatesolution resulted in more dehydration and molecular chain folding, thus the treated hydrogels showed significantly improved tensile and compressive modulus, and decreased equilibrium swelling ratio, as revealed by scanning electron microscopy (SEM), Fourier transform infraredspectroscopy (FTIR), and mechanical tests, etc. Additionally, the reinforced hydrogels were recoverable and biocompatible to modulate the proliferation behavior of human umbilical vein endothelial cells. In conclusion, this paper provides a facile reference for tuning mechanical properties of gelatin-based hydrogels and cell-hydrogel interactions, which show potential capacity in tissue engineering and biomedical fields.

Hydrophobic and self-recoverable cellulose nanofibrils/N-alkylated chitosan/poly(vinyl alcohol) sponge for selective and versatile oil/water separation.

A highly hydrophobic and self-recoverable sponge was prepared with cellulose nanofibrils (CNFs), N-alkylated chitosan (NCS), and poly (vinyl alcohol) (PVA), which was then endowed with hydrophobic properties via simple thermal chemical vapor deposition (CVD). The three-dimensional (3D) interconnected microstructure of the prepared CNF/NCS/PVA sponge was found to have 96% porosity, ultra-low density (16.61-50.91 mg/cm3) and high hydrophobicity (water contact angle of 147°), which can absorb various organic solvents with an absorption capacity of 19.05-51.08 times of its original weight. Besides, the sponge could bear 80% strain and be cyclically compressed 50 times under the strain of 50%. The sponge can effectively separate oil/water mixtures and water-in-oil emulsions with high separation efficiency and fluxes. Moreover, the sponge could keep its good stability in various acidic, saline and mechanical abrasion conditions. The green preparation and good separation efficiency suggest a potential application of recyclable and versatile CNF/NCS/PVA sponges in oil/water separation.

Morphology-controllable cellulose/chitosan sponge for deep wound hemostasis with surfactant and pore-foaming agent.

Developing a facile and scalable synthetic route is important to explore the potential application of functional cellulose sponges. Here, a simple and efficient strategy to produce porous and hydrophilic cellulose sponges using surfactant and pore-foaming agent is demonstrated. The obtained cellulose sponges exhibit high water absorption capacity and rapid shape recoverability. The introduction of chitosan endows the chitosan/cellulose composite sponge with good mechanical properties. Inhibitory effects on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa are particularly proved. Besides, the result of the dynamic whole blood clotting time indicated that the chitosan/cellulose composite sponge has better coagulation ability than those of traditional gauze and gelatin sponge. Animal experiment further showed that rapid hemostasis within 105 s could be reached with the composite sponge. Good biocompatibility of the composite sponge is proved by the results of hemocompatibility and cytotoxicity, indicating an excellent candidate as a rapid hemostatic material.

Investigation on the tunable effect of oxidized konjac glucomannan with different molecular weight on gelatin-based composite hydrogels.

Herein, oxidized konjac glucomannan (OKG) with different molecular weight (Mw) were prepared as polysaccharide crosslinker to reinforce gelatin-based hydrogels. Then, properties of composite hydrogels with various OKGs were investigated via a series of methods, including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), rheology, mechanical and biocompatibility tests. The results confirmed an increased degree of crosslinking and entanglement between gelatin and OKG with higher Mw. Besides, composite hydrogels not only showed increased mechanical strength, but self-healing ability at the same time, which were closely affected by the Mw of OKG. Furthermore, both composite hydrogels could support well proliferation of cells, which showed excellent capacity in tissue engineering and biomedical applications. In brief, this work provides a facile method to promote the overall properties of gelatin-based hydrogels, meanwhile revealed the relationship and mechanism underlying the effects of OKG with different Mw on composite hydrogels.

Liquid-Exfoliated Mesostructured Collagen from the Bovine Achilles Tendon as Building Blocks of Collagen Membranes.

Mesoscaled assemblies are organized in native collagen tissues to achieve remarkable and diverse performance and functions. In this work, a facile, low-cost, and controllable liquid exfoliation method was applied to directly extract these collagen mesostructures from bovine Achilles tendons using a sodium hydroxide (NaOH)/urea aqueous system with freeze-thaw cycles and sonication. A series of collagen fibrils with diameters of 26-230 nm were harvested using this process, and in situ observations under polarizing microscopy (POM) and using molecular dynamics simulations revealed the influence of the NaOH/urea system on the tendon collagen. FTIR and XRD results confirmed that these collagen fibrils preserved typical structural characteristics of type I collagen. These isolated collagen fibrils were then utilized as building blocks to fabricate free-standing collagen membranes, which exhibited good stability in solvents and outstanding mechanical properties and transparency, with potential for utility in optical and electronic sensors. Moreover, in vitro and vivo evaluations demonstrated that these new resulting collagen membranes had good cytocompatibility, biocompatibility, and degradability for potential applications in biomedicine. This work provides a new approach for collagen processing by liquid exfoliation with utility for the formation of robust collagen materials that consist of native collagen mesostructures as building blocks.

Soluble soybean polysaccharide/nano zinc oxide antimicrobial nanocomposite films reinforced with microfibrillated cellulose.

Nanocomposite films of soluble soybean polysaccharide (SSPS)/nano zinc oxide (nZnO) reinforced with microfibrillated cellulose (MFC) were developed by solvent casting method. The structure, optical, barrier, thermal, surface wettability, mechanical properties and antimicrobial activity of the SSPS/MFC, SSPS/nZnO and SSPS/nZnO/MFC nanocomposite films were evaluated. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra indicated interactions between SSPS and the nano-fillers. The nanocomposite films containing MFC showed improved tensile strength, stiffness, ultraviolet (UV) light barrier property, thermal stability and water resistance when compared with the neat SSPS film. The nZnO-incorporated nanocomposite films exhibited good antimicrobial activity against E. coli and B. subtlis. Overall, the MFC-reinforced SSPS/nZnO nanocomposite films possessed desirable characteristics to be considered as potential candidates for antimicrobial packaging and biomedical applications.

Rapid hemostatic chitosan/cellulose composite sponge by alkali/urea method for massive haemorrhage.

Here, a simple and efficient strategy to produce porous and hydrophilic chitosan/cellulose sponge using surfactant and pore-forming agent is demonstrated. The preparation of composite sponge by LiOH/KOH/urea solvent system effectively solve the problems of uneven distribution of chitosan, poor softness and acid residue caused by soaking in chitosan acid solution. The obtained chitosan/cellulose sponges exhibit high water absorption capacity and rapid shape recoverability, as well as good mechanical properties. Effective inhibitory on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa are particularly proved. Besides, the result of the dynamic whole blood clotting time indicated that the chitosan/cellulose composite sponge has better coagulation ability than those of traditional gauze and gelatin sponge. Animal experiment further showed that rapid hemostasis within 34 s can be reached with the composite sponge. Better biocompatibility of the composite sponge is proved by the results of hemocompatibility and cytotoxicity, indicating an excellent candidate for rapid hemostasis in massive haemorrhage.

High mechanical strength gelatin composite hydrogels reinforced by cellulose nanofibrils with unique beads-on-a-string morphology.

This work prepared high mechanical strength gelatin composite hydrogels reinforced by cellulose nanofibrils with unique beads-on-a-string morphology. In detail, cellulose nanofibrils (H-Cel) with unique beads-on-a-string morphology were obtained by acid hydrolysis followed by intensive sonication. The D-H-Cel nanofibrils were prepared through oxidizing part of the non-esterified hydroxyl groups on the H-Cel into aldehyde groups. D-H-Cel were then mixed with gelatin and D-H-Cel/Gel composite hydrogels were produced. During the mixing, a giant network structure was constructed through the Schiff-base reaction between the aldehyde groups on the surface of D-H-Cel nanofibrils and the primary amino groups on gelatin macromolecular chains. Since the cellulose nanofibrils were covalently bonded to gelatin, the stress could be efficiently transferred between the reinforcing agent and matrix, resulting in a composite hydrogel with drastically increased mechanical strength. The compressive strength of D-40H-Cel/Gel hydrogel reached 3.398 MPa. SEM images showed a highly porous three-dimensional structure in the hydrogel with regulated pore size. The crosslinking indices were measured with ninhydrin assay. The composite hydrogels could maintain their shape well in buffer solution. The present work shows that natural polymer-based composite hydrogels with extremely high mechanical strength could be obtained by reinforcing with surface modified cellulose nanofibrils with unique beads-on-a-string morphology.

Injectable antibacterial cellulose nanofiber/chitosan aerogel with rapid shape recovery for noncompressible hemorrhage.

Here an injectable antibacterial aerogel was fabricated with oxidized cellulose nanofiber and chitosan for rapid hemostasis of noncompressible hemorrhage application. Especially, cellulose nanofiber was modified with carboxyl groups by pre-oxidizing in 2,2,6,6-tetramethylpiperidine-1-oxyl combined with high pressure homogenization. Whereafter, the realized carboxyl group of cellulose nanofiber was reacted with the amidogen of chitosan to yield a strong composite aerogel with a nanofiber/nanosheet interlaced structure, which increased the compressive mechanical strength up to 75.4 kPa. In addition, the nanocellulose/chitosan composite aerogel exhibits high water absorption capacity, rapid shape recovery and good antibacterial ability (via Escherichia coli and Staphylococcus aureus). Once absorbing water, the nanocellulose5/chitosan5 compressed aerogel could rapidly recover its shape within 30 s. The in vitro coagulation ability measurement showed that the composite aerogel has a good adhesion and aggregation effect to red blood cells and platelets. Hemolysis and cytotoxicity analysis results indicated a good biocompatibility for the composite aerogel.

One-step fabrication of chitosan sponge and its potential for rapid hemostasis in deep trauma.

In this paper, a facile and efficient preparation strategy for a porous and hydrophilic chitosan sponge is demonstrated, combining a surfactant and a pore-foaming agent. The resulting chitosan sponge possesses an interconnected pore structure and soft texture, exhibits fast water absorption rate and capacity, and the compressed sponge can achieve full shape recovery 5 s after absorbing water. Moreover, our process removes the residual acid commonly found in chitosan sponges prepared by the acid method. In addition, the results demonstrate the useful characteristics of our chitosan sponge, in terms of its contribution to improved blood coagulation, together with its compression strength and biocompatibility. It also demonstrates effective antibacterial properties in relation to both Escherichia coli and Staphylococcus aureus. Further testing via animal experimentation reveals that rapid hemostasis can be achieved within 50 s using our chitosan sponge.

Preparation and properties of microfibrillated chitin/gelatin composites.

Microfibrillated chitin/gelatin composite films were prepared by solvent casting method, and the nano-sized microfibrillated chitin as reinforce phase to improve oxygen resistance, water-resistant and mechanical performance in this system. The morphologies were analyzed by scanning electron microscope (SEM), and the mechanical properties were investigated by texture analyzer. Oxygen permeability property, optical property and swelling property were investigated. The results indicated that the elastic modulus and tensile strength of microfibrillated chitin/gelatin composite film reached 2.2 GPa and 74.5 MPa respectively when the content of microfibrillated chitin is 8 wt%. The swelling ratio decreased to 11.63 with the 6 wt% content of microfibrillated chitin. In addition, chitin microfibrils effectively enhanced the oxygen resistance of composite film without obvious loss of transmittance. This work expects to provide a pathway to improve gelatin performance.

Pullulan dialdehyde crosslinked gelatin hydrogels with high strength for biomedical applications.

Herein the construction of a strong gelatin hydrogel is presented by using pullulan dialdehyde (PDA) as a macromolecular crosslinker. The resultant PDA crosslinked gelatin hydrogels (G-PDA) exhibit extremely high mechanical strength, manifested in the achieved optimal compressive stress of 5.80 MPa at 80% strain, which is up to 152 times higher than pure gelatin hydrogel. The G-PDA were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The extent of crosslinking was determined by ninhydrin assay. The results suggested that the synergistic effect of dual-crosslinking, which is composed of short- and long-range covalent crosslinking and thermoreversible physical crosslinking, may played a key role in enhancing the load-bearing capacity of ensuing hydrogels. The swelling and enzymatic degradation of G-PDA are gradually limited with increasing PDA concentration. The result from MTT assay demonstrated that G-PDA is non-cytotoxic against MC3T3 cells, regardless of the concentrations of PDA.

A porous collagen-carboxymethyl cellulose/hydroxyapatite composite for bone tissue engineering by bi-molecular template method.

Inspired by the mechanism of bone formation, a porous collagen-carboxymethyl cellulose/hydroxyapatite (Col-CMC/HA) composite was designed and fabricated using a biomimetic template of Col and CMC protein-polysaccharide bi-molecules. The morphology, composition and physical properties of Col-CMC/HA composites were characterized systematically. It was found that the nano-HA homogenously distributed on the surface of Col-CMC bi-templates while the composite presented 3D porous structure with pore size from 100 µm to 300 µm. The porosities of composites were located at the range of 71%-85%. Besides, the compressive strength of composites was highly depended on the ratio of Col to CMC in the organic template. The optimized composite in respect to physical properties showed a compressive strength as high as 7.06 MPa, quite close to that of natural bone. The high relative growth rate of wild-type mouse embryonic fibroblasts cells was found for the composite, indicating a good biocompatibility. The organic-inorganic composite also behaved good in collagenase resistance and could be biodegraded in 8 weeks, with about 50% of initial weight left at the ratio of Col to CMC of 1:9. The results demonstrated that the Col-CMC/HA composite by bi-molecular template method was a rational and safe method to prepare biomaterials with tunable properties.

Incorporation of microfibrillated cellulose into collagen-hydroxyapatite scaffold for bone tissue engineering.

In this study, the composite of Collagen-Hydroxyapitite (COL-HA) with microfibrillated cellulose (MFC) was developed as a new bone substitute material. COL-HA was prepared by in-situ method and modified by dehydrothermal treatment. Microfibrillated cellulose (MFC), a nature polysaccharide with plenty of hydroxyl groups, was incorporated into COL-HA composites to improve the properties. The novel COL-HA-MFC scaffold with different ratios of COL-HA and MFC were fabricated by cold isostatic pressing technique and freeze-drying technology. During the forming process, a three-dimensional bone-like structure was shaped in hybrid scaffolds. The microstructural transitions of COL-HA-MFC composites were examined by Fourier transform infrared spectroscope (FTIR), Ultraviolet-visible spectrophotometer (UV), and X-ray diffraction (XRD), which indicated that HA deposited on collagen molecules and MFC bonded with COL-HA. Hydrophilicity, swelling property, mechanical property, and degradability of COL-HA-MFC composites were investigated. Biological properties, such as cytotoxicity and hemolysis, were also studied. The results showed a good swelling capacity for the scaffolds, keeping their original shapes after swelling. The compression strength and degradability of the scaffold materials could be regulated by the MFC content. The compression strength of COL-HA-MFC composite scaffords increased to 20-40 MPa, closing to that of the nature bone (1-200 MPa). The obtained scaffolds are good in biocompatibility with high level of cell growth rate (>70%) and suitable hemolysis rate (≦5%). The work might provide an efficient and alternative approach for collagen-based biomaterials with necessary properties. The COL-HA-MFC composite scaffold showed a potential application in bone tissue engineering.

Efficient removal of anionic dye (Congo red) by dialdehyde microfibrillated cellulose/chitosan composite film with significantly improved stability in dye solution.

A novel composite film with efficient removal of anionic dye (Congo red) was developed using chitosan and dialdehyde microfibrillated cellulose nano fibrils. Microfibrillated cellulose with three dimensional network structure was prepared from microcrystalline cellulose by high-pressure homogenization. Then it was surface modified by periodate to prepare dialdehyde microfibrillated cellulose (DAMFC). DAMFC/chitosan composite films were prepared by solvent-casting. During the compounding of DAMFC with chitosan, a Schiff base was formed through the reaction between the aldehyde groups of DAMFC and amino groups of chitosan. A giant network structure was therefore formed. The addition of DAMFC resulted in remarkably increased adsorption capacity of the chitosan material as well as drastically improved stability in dye solution. The adsorption performance was investigated with respect to pH, temperature, contact time, and the initial dye concentration. The possible adsorption mechanism was proposed. Various isotherm models have been used to fit the data, and kinetic parameters were evaluated.

Tannin-immobilized cellulose hydrogel fabricated by a homogeneous reaction as a potential adsorbent for removing cationic organic dye from aqueous solution.

Tannin-immobilized cellulose (CT) hydrogels were successfully fabricated by homogeneous immobilization and crosslinking reaction via a simple method. The structures and properties of hydrogels were characterized by SEM and mechanical test. Methlyene Blue (MB) was selected as a cationic dye model, and the adsorption ability of CT hydrogel was evaluated. Tannins immobilized acted as adsorbent sites which combined MB by electrostatic attraction, resulting in the attractive adsorption ability of CT hydrogel. Adsorption kinetics could be better described by the pseudo-second-order model, and the absorption behaviors were in agreement with a Langmuir isotherm. The adsorption-desorption cycle of CT hydrogel was repeated six times without significant loss of adsorption capacity. In this work, both tannin immobilization and hydrogel formation were achieved simultaneously by a facile homogeneous reaction, providing a new pathway to fabricate tannin-immobilized materials for water treatment.