Jiawei Liu

Chitosan/gelatin composite sponge is an absorbable surgical hemostatic agent

Chitosan is a versatile biological material that is very well known for its hemostatic properties. The purpose of this study was to test the hemostatic properties of a chitosan composite obtained from silkworm pupae and gelatin. This spongy porous material was cross-linked with tannins and then freeze-dried under vacuum to obtain composites containing chitosan and gelatin in different proportions. Results showed that the best blood-clotting index (BCI) was achieved in vitro by a chitosan/gelatin sponge (CG) ratio of 5/5 (W/W). Furthermore, CG had the best hemostatic effect in rabbit artery bleeding and liver model tests compared to the two components separately. The better hemostatic effect of CG may be due to its ability to absorb blood platelets easily and to the higher liquid adsorption ratio. However, no obvious differences were observed in thrombin generation with both aPTT and PT tests. Cell toxicity tests with L929 cells showed that CG caused no obvious cytotoxicity. In addition, subcutaneous transplantation of CG into rabbits resulted in almost complete degradation of CG after 6 weeks, together with rich vascular generation and proliferation in the transplanted region. Thus, CG can be considered an effective absorbable hemostatic material.

Healing of skin wounds with a chitosan-gelatin sponge loaded with tannins and platelet-rich plasma.

A chitosan-gelatin sponge (CSGT) was prepared using a chitosan/ascorbic acid solution blend containing gelatin, followed by crosslinking with tannin acid and freeze-drying, thereby combining the chitosan sponge and gelatin sponge. The structure of the CSGT was observed by scanning electron microscopy and was shown to have uniform and abundant pores measuring about 145-240μm in size. We also characterized the sponges by infrared spectroscopy, thermogravimetric analysis, mechanical property tests, swelling behavior analysis, water retention capacity tests, antibacterial property analysis, and cytotoxicity tests. Our data showed that the CSGT had good thermostability and mechanical properties as well as efficient water absorption and retention capacities. Moreover, the CSGT could effectively inhibit the growth of Escherichia coli and Staphylococcus aureus with low toxicity. In animal experiments, macroscopic observations and histological examinations showed that the wound covered by the CSGT healed quickly. Additionally, loading of the CSGT with platelet-rich plasma resulted in further acceleration of wound healing. Therefore, the CSGT and the CSGT with platelet-rich plasma were suitable for application as a wound dressing and may have potential for use in various biomedical applications.

Preparation and characterization of N-chitosan as a wound healing accelerator.

Chitosan is insoluble in water due to its rigid crystalline structure, which has significantly restricted its application in wound healing. The objective of this study was to synthesize a water-soluble chitosan derivative, N-succinyl-chitosan (NSC), and evaluate its ability to accelerate the wound healing process. NSC was synthesized with succinic anhydride, hydrochloric acid, and alkaline chitosan under optimized conditions, and characterized using Fourier transform infrared, proton nuclear magnetic resonance, and X-ray diffraction spectroscopy; thermal gravimetric analysis; and a solubility test. The cytotoxicity of NSC was investigated in L929 cells, and its antibacterial activity was evaluated by the inhibition zone method and bacterial growth curves analysis. The results showed that the solubility of NSC was substantially improved compared to chitosan, and NSC was non-toxic with good antibacterial properties. An animal wound healing test indicated that NSC could significantly reduce the healing time compared to chitosan. Histopathological examination suggested that the underlying mechanisms of these effects were related to NSCs ability to promote the formation of granulation tissue and enhance epithelialization. Collectively, these results demonstrate the good potential for NSC to be applied as a wound dressing material.

In situ reduction of silver nanoparticles by chitosan-l-glutamic acid/hyaluronic acid: enhancing antimicrobial and wound-healing activity

Spongy composites with silver nanoparticles (AgNPs) were synthesized by freeze-drying a mixture of silver nitrate (AgNO3) and chitosan-l-glutamic acid (CG) derivative loaded with hyaluronic acid (HA) solution. CG/AgNP spongy composites had an interconnected porous structure and rough surfaces. When AgNPs (5-20nm) were immobilized on these spongy composites, AgNP aggregation was dependent on AgNO3 concentration. The spongy composites exhibited good mechanical properties, swelling, and water retention capacity. In vitro antibacterial activity showed that the CG/AgNP spongy composites effectively inhibited bacterial (Escherichia coli and Staphylococcus aureus) growth and penetration. Spongy composites containing low concentrations of AgNP were non-toxic to L929 cells, while CG/HA/AgNP spongy composites promoted wound healing, as determined by in vivo tests, wound contraction ratio, average healing time, and histological examination. These results indicate that the spongy composites can serve as effective antibacterial wound dressings.

In situ assembly of Ag nanoparticles (AgNPs) on porous silkworm cocoon-based would film: enhanced antimicrobial and wound healing activity

Preventing wound infection and retaining an appropriate level of moisture around wounds represent the most critical issues in wound treatment. Towards these ends, special focus has been placed on Bombyx mori cocoons because the protective function of the silkworm cocoon resembles the manner in which the skin protects the human body. We have designed a facile technique to develop a novel silkworm cocoon-based wound film (SCWF) wound dressing utilizing a CaCl2-ethanol-H2O solution. To improve the anti-bacterial performance of SCWF, we have incorporated the ability of silk sericin to act as a reducing agent for the conversion of Ag+ to Ag, yielding nanoparticles (AgNPs) linked together by peptide bonds of silkworm cocoon wound film (SCWF-AgNPs). SCWF-AgNP dressing exhibited excellent biocompatibility, anti-bacterial performance, and good extensibility. Furthermore, in vivo experiments indicated that SCWF-AgNP dressing was able to significantly accelerate the healing rate of infected wounds in New Zealand White rabbits and histological examination revealed that it aided in the successful reconstruction of intact and thickened epidermis during 14 days of healing of impaired wound tissue. These results demonstrate that the present approach might shed new light on the design of anti-bacterial materials such as SCWF-AgNPs with promising applications in wound dressing.

Healing of skin wounds using a new cocoon scaffold loaded with platelet-rich or platelet-poor plasma

The cocoons of the silkworm Bombyx mori are widely used as biofunctional materials. In the present study, cocoon composites (CCs) were treated with a solution consisting of calcium chloride, ethanol, and distilled water, resulting in partial dissolution, followed by freeze-drying, yielding cocoon scaffolds (CCSs). The CCSs were then immersed in autologous platelet-rich plasma (PRP) or platelet-poor plasma (PPP) obtained from rabbits and freeze-dried again, allowing us to harvest the other two composite materials (CCSs + PRP and CCSs + PPP). Analysis of the physical and biological properties of the materials demonstrated that the water absorption and retention capacities of CCSs had improved. After loading with PRP or PPP, both of the composite materials significantly promoted the growth of L929 cells, with CCSs + PRP showing slightly better results. Additionally, in vivo studies showed that both of the composite materials could enhance the process of wound healing, with the CCSs + PRP exhibiting the best results. Thus, our results suggested that these composites may have potential applications in the biomedical field.

Accelerated wound-healing capabilities of a dressing fabricated from silkworm cocoon

Silk fibroin materials have shown some success in wound dressing applications; however, their use for this purpose remains limited by a complex production process and wasted sericin. In the present study, Bombyx mori cocoon materials are used because the protective function of the silkworm cocoon resembles the manner in which the skin protects the human body. A series of silkworm cocoon sol-gel film (SCSF) wound dressings are prepared by immersion in a CaCl2-ethanol-H2O solution for different treatment times. The accelerated wound-healing capabilities of SCSFs are systematically evaluated. Among them, the SCSF sample immersed for 90min exhibits stronger biocompatibility and antibacterial performance compared to other SCSFs. SCSF-90 also exhibits excellent transparency, a high swelling ratio, and good extensibility. Furthermore, in vivo experiments indicate that SCSF-90 can significantly accelerate the healing rate of wounds in New Zealand white rabbits, compared to the standard Mepitel® dressing, and histological examinations reveal that SCSF-90 aided in the successful reconstruction of intact and thickened epidermis. These results demonstrate that the proposed approach may be utilized in the design of antibacterial materials with promising applications in wound dressing.

Evaluation of artificial skin made from silkworm cocoons

The protective characteristics of silkworm cocoons are the result of thousands of years of evolution. In this study, we attempted to combine the cocoon’s protective characteristics with the function of human skin to explore the possibility of using silkworm cocoons in the field of artificial skin application. We retained the natural structure of the cocoon shells and softened it by a degumming process. This process was performed so that the mechanical and permeation properties of the cocoon material meet the criteria of artificial skin with respect to tension and suturing; the cocoon material was also found to have strong antibacterial activity and cell compatibility. These properties of the cocoon suggest that it has a high potential to be used as an artificial skin. Overall, we expect the silkworm cocoon to be a type of biological material with extensive possibilities of application as artificial skin.

Cellobiose as a model compound for cellulose to study the interactions in cellulose/lithium chloride/N-methyl-2-pyrrolidone systems

Abstract To investigate the solvent/solute interactions that take place during the dissolution of cellulose, cellobiose was employed as a model of the longer-chain cellulose molecule in a dissolution study of the cellobiose/LiCl/N-methyl-2-pyrrolidone (NMP) system, conducted using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), 13C, 35Cl, and 7Li NMR spectroscopy, and conductivity measurements. For the LiCl/NMP system, FTIR and 13C NMR analyses of the NMP carbonyl moiety showed a strong dependence on the LiCl concentration, which suggested an association between the Li+ cations and the carbonyl groups of NMP. As the cellobiose molecules are dissolved in the LiCl/NMP solvent, the Li+–Cl− ion-pairs in LiCl/NMP are dissociated. Strong hydrogen bonds are then formed between the hydroxyl groups of cellobiose and the Cl− anions, resulting in breakage of the intermolecular hydrogen bonds of cellobiose. Meanwhile, the Li+ cations are further associated with the extra free NMP molecules. However, the NMP molecules do not directly interact with the dissolved cellobiose. Based on these results, we propose that our study is conducive to a more in-depth comprehension of the dissolution mechanism of cellulose in LiCl/NMP.

Preparation of a partially carboxymethylated cotton gauze and study of its hemostatic properties

In this study, we attempted to modify cotton gauze by partial carboxymethylation by varying the reaction time and concentration of monochloroacetic acid and sodium hydroxide. For each experiment, the relative value of the degree of substitution (DS) of the modified cotton gauze was evaluated and the whole blood clotting time (WBCT) and water absorption property were compared with cotton gauze and Surgicel. This revealed that, following an initial decrease, WBCT gradually increased. Using rabbit ear artery and liver haemorrhage models, the performance of the optimal modified gauze was compared to that of Surgicel and unmodified cotton gauze. The average bleeding times in the presence of modified cotton gauze in the rabbit ear arteries and the liver were 51.7s and 60.6s, while those with Surgicel and the unmodified cotton gauze were 76.8s and 95.5s, and 93.2s and 129.2s, respectively. The hemostatic and biocompatibility properties were evaluated using in vivo degradation experiments. This revealed that the modified gauze and Surgicel were totally degraded within 6 weeks.