Unpredictable recombination of PB transposon in Silkworm: a potential risk.

The piggyBac (PB) transposon is the most widely used vector for generating transgenic silkworms. The stability of the PB transposon in the receptor is a serious concern that requires attention because of biosafety concerns. In this study, we found that the transgene silkworm developed loss of reporter gene traits. To further investigate the regularity, we traced the genes and traits of this silkworm. After successful alteration of the silkworm genome with the MASP1 gene (named red-eyed silkworm; RES), silkworm individuals with lost reporter genes were found after long-term transgenerational breeding and were designated as the white-eyed silkworm (WES). PCR amplification indicated that exogenous genes had been lost in the WES. Testing was conducted on the PB transposons, and the left arm (L arm) did not exist; however, the right arm (R arm) was preserved. Amino acid analysis showed that the amino acid content of the WES changed versus the common silkworm and RES. These results indicate that the migration of PB transposons in Bombyx mori does occur and is unpredictable. This is because the silkworm genome contains multiple PB-like sequences that might influence the genetic stability of transgenic lines. When using PB transposons as a transgene vector, it is necessary to fully evaluate and take necessary measures to prevent its re-migration in the recipient organism. Further experiments are needed if we want to clarify the regularity of the retransposition phenomenon and the direct and clear association with similar sequences of transposons.

An injectable self-healing hydrogel with adhesive and antibacterial properties effectively promotes wound healing.

Hydrogels with self-healing capacity can undergo self-repair, establishing safer and longer-lasting products. Hydrogel wound dressings showing self-healing capacity can prolong the lifespan of the material and provide better wound protection. Therefore, in this study, Schiff base reactions (reversible imine linkages) were utilized to design injectable self-healing hydrogels with chitosan and konjac glucomannan. Oxidized konjac glucomannan was used to react with chitosan to form hydrogel. In addition to injectable, self-healing properties, the hydrogels also had adhesive and antibacterial properties, were biocompatible, and promoted wound healing. The inhibition rates of hydrogels against Staphylococcus aureus and Escherichia coli were 96% and 98%, respectively. In addition, microscopy and rheological analyses showed that the hydrogels healed within 4 h without additional exogenous stimulation. Finally, the developed hydrogels were injectable and significantly shortened wound recovery time in a full-thickness skin defect model. Thus, our findings established a novel hydrogel material that may have applications in wound healing.

Self-assembly of natural protein and imidazole molecules on gold nanoparticles: Applications in wound healing against multi-drug resistant bacteria.

Developing highly active and green antibacterial agents for pathogens, especially multidrug-resistant superbugs, is vital for solving the problem of serious antibiotic resistance. Herein, we report a unique system of gold nanoparticles coated with chicken egg white (CEW) and 2-mercapto-1-methylimidazole (MMT) as a novel antibacterial agent. The CEW was used to prepare the gold nanoparticles as a commercially available reducing and stabilizing agent, and then the MMT self-assembled on the surface of nanoparticles. The resulting Au@CEW/MMT was found to be a highly efficient antibacterial agent, and the activity is mainly attributed to the synergistic effects of MMT and Au@CEW in undermining the bacterial membrane. Meanwhile, the studies of antibacterial activities and biocompatibility of Au@CEW/MMT with different ratios of MMT conjugation to Au@CEW confirmed that Au@CEW/MMT3 (MMT:HAuCl4 = 1:50) can maintain a balance between antibacterial properties and biocompatibility. Furthermore, in an in-vivo study using the rabbit model, gauze loaded with Au@CEW/MMT3 can effectively accelerate the healing of wounds infected with methicillin-resistant S. aureus and promote the formation of collagen. Therefore, this work illustrated a promising material with broad-spectrum antibacterial activities for preclinical applications in treating wound infections.

A novel wound dressing based on a Konjac glucomannan/silver nanoparticle composite sponge effectively kills bacteria and accelerates wound healing.

A novel Konjac glucomannan/silver nanoparticle (KGM/AgNP) composite sponge was successfully prepared via a simple 2-step method for biomedical applications as wound-healing materials. First, AgNPs were prepared with green deoxidizer egg white. Then, KGM powder was added to the AgNP solution and stirred vigorously, and the composite sponge was obtained by freeze-drying. The KGM/AgNP composite sponge showed excellent water absorption and water retention, and considerable mechanical properties. KGM/AgNP composite sponges displayed good antibacterial activity against test microorganisms. In vitro cytocompatibility testing showed that L929 cells could survive well in the presence of KGM/AgNPs, indicating that KGM/AgNPs have good cytocompatibility. Animal models showed that the KGM/AgNP composite sponges effectively accelerated wound healing, and histological findings showed that they promoted fibroblast growth and accelerated epithelialization. The experimental results showed that KGM/AgNP composite sponges have great potential in promoting wound healing.

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

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Silver Inlaid with Gold Nanoparticle/Chitosan Wound Dressing Enhances Antibacterial Activity and Porosity, and Promotes Wound Healing.

Silver inlaid with gold nanoparticles (Au-Ag NPs) prepared by using egg white with an average sized of 10 nm and homogeneous dispersion were tested and presented red fluorescence. Au-Ag NPs were loaded into chitosan as wound dressing (CS-Au-Ag). CS-Au-Ag released silver ions faster, in higher amount, and in a more durable manner than chitosan dressing loaded with silver nanoparticles with the same silver content (CS-Ag), consequently, showing enhanced antibacterial activity. Cytotoxicity tests indicated that CS-Au-Ag showed low cytotoxicity to L929 cells similar to CS-Ag. These data suggest that cytotoxicity, which restricts further application of silver NPs, can be eliminated by decreasing the silver content. CS-Au-Ag presented rich and well-distributed pores, good mechanical properties, and enhanced swelling and retention properties, contributing to keeping the wound moist in the presence of residual egg white. Altogether, our results suggest that CS-Au-Ag greatly promoted wound healing compared to CS-Ag in vivo, demonstrating that CS-Au-Ag presents great potential for wound dressing, promoting wound healing.

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 wound 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.

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.

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 NSC's 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.

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.

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.

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.

Repression of tyrosine hydroxylase is responsible for the sex-linked chocolate mutation of the silkworm, Bombyx mori.

Pigmentation patterning has long interested biologists, integrating topics in ecology, development, genetics, and physiology. Wild-type neonatal larvae of the silkworm, Bombyx mori, are completely black. By contrast, the epidermis and head of larvae of the homozygous recessive sex-linked chocolate (sch) mutant are reddish brown. When incubated at 30 degrees C, mutants with the sch allele fail to hatch; moreover, homozygous mutants carrying the allele sch lethal (sch(l)) do not hatch even at room temperature (25 degrees C). By positional cloning, we narrowed a region containing sch to 239,622 bp on chromosome 1 using 4,501 backcross (BC1) individuals. Based on expression analyses, the best sch candidate gene was shown to be tyrosine hydroxylase (BmTh). BmTh coding sequences were identical among sch, sch(l), and wild-type. However, in sch the approximately 70-kb sequence was replaced with approximately 4.6 kb of a Tc1-mariner type transposon located approximately 6 kb upstream of BmTh, and in sch(l), a large fragment of an L1Bm retrotransposon was inserted just in front of the transcription start site of BmTh. In both cases, we observed a drastic reduction of BmTh expression. Use of RNAi with BmTh prevented pigmentation and hatching, and feeding of a tyrosine hydroxylase inhibitor also suppressed larval pigmentation in the wild-type strain, pnd(+) and in a pS (black-striped) heterozygote. Feeding L-dopa to sch neonate larvae rescued the mutant phenotype from chocolate to black. Our results indicate the BmTh gene is responsible for the sch mutation, which plays an important role in melanin synthesis producing neonatal larval color.