One-Pot Assembly of Drug-Eluting Silk Coatings with Applications for Nerve Regeneration

Clinical use of polymeric scaffolds for tissue engineering often suffers from their inability to promote strong cellular interactions. Functionalization with biomolecules may improve outcomes; however, current functionalization approaches using covalent chemistry or physical adsorption can lead to loss of biomolecule bioactivity. Here, we demonstrate a novel bottom-up approach for enhancing the bioactivity of poly(l-lactic acid) electrospun scaffolds though interfacial coassembly of protein payloads with silk fibroin into nanothin coatings. In our approach, protein payloads are first added into an aqueous solution with Bombyx mori-derived silk fibroin. Phosphate anions are then added to trigger coassembly of the payload and silk fibroin, as well as noncovalent formation of a payload-silk fibroin coating at poly(l-lactic) acid fiber surfaces. Importantly, the coassembly process results in homogeneous distribution of protein payloads, with the loading quantity depending on payload concentration in solution and coating time. This coassembly process yields greater loading capacity than physical adsorption methods, and the payloads can be released over time in physiologically relevant conditions. We also demonstrate that the coating coassembly process can incorporate nerve growth factor and that coassembled coatings lead to significantly more neurite extension than loading via adsorption in a rat dorsal root ganglia explant culture model.

Advances of regenerated and functionalized silk biomaterials and application in skin wound healing

The cocoon silk of silkworms (Bombyx mori) has multiple potential applications in biomedicine due to its good biocompatibility, mechanical properties, degradability, and plasticity. Numerous studies have confirmed that silk material dressings are more effective than traditional ones in the skin wound healing process. Silk material research has recently moved toward functionalized biomaterials and achieved remarkable results. Herein, we summarize the recent advances in functionalized silk materials and their efficacy in skin wound healing. In particular, transgenic technology has realized the specific expression of human growth factors in the silk glands of the silkworms, which lays the foundation for fabricating novel and low-cost functionalized materials. Without a green and safe preparation process, the best raw silk materials cannot be made into medically safe products. Therefore, we provide an overview of green and gentle approaches for silk degumming and silk sericin (SS) extraction. Moreover, we summarize and discuss the processing methods of silk fibroin (SF) and SS materials and their potential applications, such as burns, diabetic wounds, and other wounds. This review aims to enhance our understanding of new advances and directions in silk materials and guide future biomedical research.

WIV, a protein domain found in a wide number of arthropod viruses, which probably facilitates infection

The most powerful approach to detect distant homologues of a protein is based on structure prediction and comparison. Yet this approach is still inapplicable to many viral proteins. Therefore, we applied a powerful sequence-based procedure to identify distant homologues of viral proteins. It relies on three principles: (1) traces of sequence similarity can persist beyond the significance cutoff of homology detection programmes; (2) candidate homologues can be identified among proteins with weak sequence similarity to the query by using 'contextual' information, e.g. taxonomy or type of host infected; (3) these candidate homologues can be validated using highly sensitive profile-profile comparison. As a test case, this approach was applied to a protein without known homologues, encoded by ORF4 of Lake Sinai viruses (which infect bees). We discovered that the ORF4 protein contains a domain that has homologues in proteins from >20 taxa of viruses infecting arthropods. We called this domain 'widespread, intriguing, versatile' (WIV), because it is found in proteins with a wide variety of functions and within varied domain contexts. For example, WIV is found in the NSs protein of tospoviruses, a global threat to food security, which infect plants as well as their arthropod vectors; in the RNA2 ORF1-encoded protein of chronic bee paralysis virus, a widespread virus of bees; and in various proteins of cypoviruses, which infect the silkworm Bombyx mori. Structural modelling with AlphaFold indicated that the WIV domain has a previously unknown fold, and bibliographical evidence suggests that it facilitates infection of arthropods.

Identification of long noncoding RNAs of silkworm at the early stage of Bombyx mori bidensovirus infection

Bombyx mori bidensovirus (BmBDV) is one of the most important pathogens of silkworm. It mainly infects midgut cells of silkworm and causes losses to the sericulture industry. Long noncoding RNAs (lncRNAs) have been reported to play an important role in the regulation of antiviral immune response in silkworm. To explore whether lncRNAs are involved in BmBDV infection and immune response of silkworm, we performed a comparative transcriptome analysis to identify the lncRNAs and mRNAs between the BmBDV infected and noninfected silkworm larvae at the early stage. A total of 16,069 genes and 974 candidate lncRNAs were identified, among which 142 messenger RNA (mRNAs) and four lncRNAs were differentially expressed (DE). Target gene prediction revealed that 142 DEmRNAs were coexpressed with four DElncRNAs, suggesting that the expression of mRNA is mainly affected through trans-regulation activities. A regulatory network of DElncRNAs and DEmRNAs was constructed, showing that many genes targeted by different DElncRNAs are involved in metabolism and immunity, which implies that these genes and lncRNAs play an important role in the replication of BmBDV. Our results will help us to improve our understanding of lncRNA-mediated regulatory roles in BmBDV infection, providing a new perspective for further exploring the interaction between host and BmBDV.

Effects of protein aggregation induced by NaCl and temperature on gelation of silkworm (Antheraea pernyi) pupa raw powder

Edible insects have great potential for producing protein-rich ingredients. This study aimed to investigate the effects of protein aggregation induced by NaCl (0-1 M) and temperature (65-95 °C) on gelation of Antheraea pernyi (A. pernyi) pupa raw powder. No thermal aggregates were observed at low temperature (65 °C), on the basis of there being no significant enhancement in turbidity and particle size (P > 0.05), regardless of NaCl concentrations. At elevated temperatures (75-95 °C), protein solutions exhibited significantly higher turbidity and particle size (P < 0.05), accompanied by an initial rise in surface hydrophobicity followed by a decline, alongside declining sulfhydryl. This marks the beginning of massive thermal aggregation driven by molecular forces. In addition, covalent (disulfide bonds) and non-covalent (hydrogen bonding, electrostatic interactions, and hydrophobicity) forces were influenced by NaCl, leading to variability in the protein aggregation and gelation. Correlation analysis indicates that the higher protein aggregation induced by ions was beneficial to the construction of more compact three-dimensional structures, as well as to the rheology, texture, and water-holding capacity of A. pernyi pupa gels. However, excessive salt ions destroyed the gel structure. Our findings will aid the use of A. pernyi pupae as textural ingredients in formula foods.

Serpin-4 Negatively Regulates Prophenoloxidase Activation and Antimicrobial Peptide Synthesis in the Silkworm, Bombyx mori

The prophenoloxidase (PPO) activation and Toll antimicrobial peptide synthesis pathways are two critical immune responses in the insect immune system. The activation of these pathways is mediated by the cascade of serine proteases, which is negatively regulated by serpins. In this study, we identified a typical serpin, BmSerpin-4, in silkworms, whose expression was dramatically up-regulated in the fat body and hemocytes after bacterial infections. The pre-injection of recombinant BmSerpin-4 remarkably decreased the antibacterial activity of the hemolymph and the expression of the antimicrobial peptides (AMPs) gloverin-3, cecropin-D, cecropin-E, and moricin in the fat body under Micrococcus luteus and Yersinia pseudotuberculosis serotype O: 3 (YP III) infection. Meanwhile, the inhibition of systemic melanization, PO activity, and PPO activation by BmSerpin-4 was also observed. Hemolymph proteinase 1 (HP1), serine protease 2 (SP2), HP6, and SP21 were predicted as the candidate target serine proteases for BmSerpin-4 through the analysis of residues adjacent to the scissile bond and comparisons of orthologous genes in Manduca sexta. This suggests that HP1, SP2, HP6, and SP21 might be essential in the activation of the serine protease cascade in both the Toll and PPO pathways in silkworms. Our study provided a comprehensive characterization of BmSerpin-4 and clues for the further dissection of silkworm PPO and Toll activation signaling.

Microfibre-Functionalised Silk Hydrogels

Silk hydrogels have shown potential for tissue engineering applications, but several gaps and challenges, such as a restricted ability to form hydrogels with tuned mechanics and structural features, still limit their utilisation. Here, Bombyx mori and Antheraea mylitta (Tasar) silk microfibres were embedded within self-assembling B. mori silk hydrogels to modify the bulk hydrogel mechanical properties. This approach is particularly attractive because it creates structured silk hydrogels. First, B. mori and Tasar microfibres were prepared with lengths between 250 and 500 μm. Secondary structure analyses showed high beta-sheet contents of 61% and 63% for B. mori and Tasar microfibres, respectively. Mixing either microfibre type, at either 2% or 10% (w/v) concentrations, into 3% (w/v) silk solutions during the solution-gel transition increased the initial stiffness of the resulting silk hydrogels, with the 10% (w/v) addition giving a greater increase. Microfibre addition also altered hydrogel stress relaxation, with the fastest stress relaxation observed with a rank order of 2% (w/v) > 10% (w/v) > unmodified hydrogels for either fibre type, although B. mori fibres showed a greater effect. The resulting data sets are interesting because they suggest that the presence of microfibres provided potential 'flow points' within these hydrogels. Assessment of the biological responses by monitoring cell attachment onto these two-dimensional hydrogel substrates revealed greater numbers of human induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) attached to the hydrogels containing 10% (w/v) B. mori microfibres as well as 2% (w/v) and 10% (w/v) Tasar microfibres at 24 h after seeding. Cytoskeleton staining revealed a more elongated and stretched morphology for the cells growing on hydrogels containing Tasar microfibres. Overall, these findings illustrate that hydrogel stiffness, stress relaxation and the iPSC-MSC responses towards silk hydrogels can be tuned using microfibres.

Customized Integrating-Sphere System for Absolute Color Measurement of Silk Cocoon with Corrugated Microstructure

Silk fiber, recognized as a versatile bioresource, holds wide-ranging significance in agriculture and the textile industry. During the breeding of silkworms to yield new varieties, optical sensing techniques have been employed to distinguish the colors of silk cocoons, aiming to assess their improved suitability across diverse industries. Despite visual comparison retaining its primary role in differentiating colors among a range of silk fibers, the presence of uneven surface texture leads to color distortion and inconsistent color perception at varying viewing angles. As a result, these distorted and inconsistent visual assessments contribute to unnecessary fiber wastage within the textile industry. To solve these issues, we have devised an optical system employing an integrating sphere to deliver consistent and uniform illumination from all orientations. Utilizing a ColorChecker, we calibrated the RGB values of silk cocoon images taken within the integrating sphere setup. This process accurately extracts the authentic RGB values of the silk cocoons. Our study not only helps in unraveling the intricate color of silk cocoons but also presents a unique approach applicable to various specimens with uneven surface textures.

Polyphosphate-loaded silk fibroin membrane as hemostatic agent in oral surgery: a pilot study

PURPOSE

Post-interventional hemorrhage can result in serious complications, especially in patients with hemostatic disorders. Identification of safe and efficient local hemostatic agents is important, particularly in the context of an ageing society and the emergence of new oral anticoagulants. The aim of this in vitro study was to investigate the potential of silk fibroin membranes coated with the inorganic polymer polyphosphate (polyP) as a novel hemostatic device in oral surgery.

METHODS

Cocoons of the silkworm Bombyx mori were degummed and dissolved. Varying amounts of long-chain polyP (2-2000 µg/mm2) were adsorbed to the surface of silk fibroin membranes. Analysis of the procoagulant effect of polyP-coated silk membranes was performed using real-time thrombin generation assays in human plasma. Increasing concentrations of polyP (0.15-500 µg/ml) served as a positive control, while uncoated silk fibroin membranes were used as negative control.

RESULTS

PolyP-coated silk fibroin membranes triggered coagulation when compared to plasma samples and pure silk fibroin membranes. A polyP-dose-dependent effect of thrombin generation could be found with a maximum (ETP = 1525.7 nM⋅min, peak thrombin = 310.1 nM, time to peak = 9.8 min, lag time = 7.6 min.) at 200 µg/mm2 of polymer loading on the silk fibroin membrane surface.

CONCLUSIONS

In this study, it was demonstrated that silk fibroin membranes coated with polyP have the potential to act as a promising novel hemostatic device.

Comparing the virulence of four major clades of Candida auris strains using a silkworm infection model: Clade IV isolates had higher virulence than the other clades

Candida auris is an emerging fungal pathogen that is feared to spread of infection because of its propensity for multidrug resistance and high mortality rate. This pathogenic yeast is classified into four major clades by phylogenetic analyses, which are referred to the South Asia clade (clade I), East Asia clade (clade II), South Africa clade (clade III), and South America clade (clade IV), based on the location of the initial isolate. In this study, we evaluated the virulence of C. auris strains belonging to four major clades and the therapeutic effects of micafungin in a silkworm infection model. The highest mortality rate at 21 h after C. auris inoculation was observed for strains from clade IV (80% or more). In contrast, it was 20% or less in those from other clades. Antifungal susceptibility tests indicated resistance to fluconazole and sensitivity to echinocandins in the blood-derived strains. Micafungin prolonged the survival of blood-derived C. auris infected silkworms. These results suggest that the silkworm infection model is useful for evaluating the virulence of C. auris and determining its therapeutic effects.

Comparative analysis of gut bacteria of silkworm Bombyx mori L. on exposure to temperature through 16S rRNA high throughput metagenomic sequencing

Global warming is one of the serious threats that adversely affects the development and reproduction of silkworms. The ideal temperature for silkworms to carryout normal life activities is 20-30 °C. Certain bivoltine silkworms that are raised in tropical regions are thermotolerant. But, prolonged exposure to high temperatures may be fatal. In the present study, fifth instar larvae of bivoltine silkworm were exposed to heat shock at 40 ± 2 °C for a short period of one hour per day to examine the changes in the gut microflora. The study used high throughput sequencing to evaluate the impact of intestinal microbes of silkworms in response to high temperature. The findings demonstrated that elevated temperature has a negative impact on the intestinal microbes of silkworm compared to the control which were reared under the optimum temperature (25 ± 3° C). Four hundred and fifty eight (458) species of microbes were reported in the control group whereas only 434 species were reported in the temperature exposed group. The digestive process of silkworms may also be impaired by heat shock due to their effect on digestive enzymes. So, the results indicated that heat shock has an impact on the intestinal microflora of silkworms that control the activity of associated digestive enzymes which affects the digestion and nutritional intake, eventually impacting the growth and development of silkworm larvae and cocoons produced. The morphometric parameters of silkworm larvae and cocoons also showed a considerable drop when exposed to heat shock.

Advanced Silk Fibroin Biomaterials-Based Microneedles for Healthcare

Microneedles are a promising transdermal drug delivery system that has the advantages of minimal invasiveness, painlessness, and on-demand drug delivery compared with commonly used medical techniques. Natural resources are developed as next-generation materials for microneedles with varying degrees of success. Among them, silk fibroin is a natural polymer obtained from silkworms with good biocompatibility, high hardness, and controllable biodegradability. These properties provide many opportunities for integrating silk fibroin with implantable microneedle systems. In this review, the research progress of silk fibroin microneedles in recent years is summarized, including their materials, processing technology, detection, drug release methods, and applications. Besides, the research and development of silk fibroin in a multidimensional way are analyzed. Finally, it is expected that silk fibroin microneedles will have excellent development prospects in various fields.

Insights into nanomechanical behavior of B. mori silk fibroin-hydroxyapatite bio-nanocomposite using MD simulations: Role of varying hydroxyapatite content

Nanocomposite material composed of Bombyx mori Silk Fibroin and hydroxyapatite (B. mori SF-HA) is a potential biomaterial for bone tissue engineering. Here, Bombyx mori Silk Fibroin (B. mori SF) is a flexible and tough organic, polymer phase, and hydroxyapatite (HA) is hard and stiff mineral phase. Knowledge about mechanical deformation behavior together with governing mechanisms, and the role of the two phases (SF and HA phase) and interfacial interactions between them, in B. mori SF-HA biomaterial, at fundamental level is an important factor to consider while developing the tissue grafts. Such nanometer scale behavior is often preferably investigated using molecular dynamics method. Present study aims at understanding the mechanical deformation behavior and associated physical mechanisms in B. mori SF-HA bio-nanocomposite, at nanoscale. For this purpose, computational atomistic models of B. mori SF-HA bio-nanocomposite are developed with varying HA content. Mechanical behavior analysis of these composite models under tensile loading were performed using Molecular Dynamics (MD) simulations. Elastic modulus and tensile strength values in the range of 7-20 GPa and 200-700 MPa, respectively, are obtained for B. mori SF-HA composite, in case of different HA contents, wherein, increased mechanical properties are observed with increase in HA content. Analyses of the deformation trajectories show that the deformation flow behavior in B. mori SF-HA bio-nanocomposites is mainly defined by the soft SF phase. However, energetics analyses show that, the HA phase and SF-HA interfacial interactions also play a considerable role in mechanical performance of B. mori SF-HA bio-nanocomposite. Additionally, interfacial shear strength values in B. mori SF-HA bio-nanocomposite, for different HA contents, have also been obtained. The observations made and insights gained in present work has contribution and impact in gaining an insight into the mechanistic interactions occurring at nanoscale between SF and HA phases in B. mori SF-HA bio-composite.

Molecular characterization of MyD88 as a potential biomarker for pesticide-induced stress in Bombyx mori

The widespread use of pesticides hampers the immune system of non-target organisms, however, there is a lack of common biomarkers to detect such effects. Myeloid differentiation primary response factor 88 (MyD88) is a crucial junction protein in the Toll-like receptor signaling pathway, which plays an important role in the inflammatory response. In this study, we investigated MyD88 as a potential biomarker for pesticide-induced stress. Phylogenetic analysis revealed that MyD88 was a conserved protein in the evolution of vertebrates and invertebrates. MyD88s usually have death domain (DD) and Toll/interleukin-1 receptor (TIR) domain. Bombyx mori (B. mori) is an important economic insect that is sensitive to toxic substances. We found microbial pesticides enhanced the expression level of MyD88 in B. mori. Transcriptome analysis demonstrated that MyD88 expression level was increased in the fatbody after dinotefuran exposure, a third-generation neonicotinoid pesticide. Moreover, the expression of MyD88 was upregulated in fatbody and midgut by imidacloprid, a first-generation neonicotinoid pesticide. Additionally, insect growth regulator (IGR) pesticides, such as methoprene and fenoxycarb, could induce MyD88 expression in the fatbody of B. mori. These results indicated that MyD88 is a potential biomarker for pesticide-induced stress in B. mori. This study provides novel insights into screening common biomarkers for multiple pesticide stresses and important implications for the development of more sustainable pest management strategies.

Effects of beauvericin on the blood cells of Bombyx mori

In this study, silkworms were treated by injection of the bioactive depsipeptide beauvericin (BEA) to explore its effect on the cellular immunity of larvae of the silkworm Bombyx mori. The results showed that: The LC50 of BEA for silkworms on the 3rd day of the 4th instar was 362.36 µM. The total count of circulating hemocytes in the silkworms decreased at 12 h after injection with 350 µM BEA, and reached the minimum value at 72 h post-treatment; at 48 h post-treatment, a large number of nodules formed by the aggregation of blood cells of the silkworms were observed under the light microscope. The survival rate of hemocytes in the larvae treated with BEA was significantly reduced in a dose-dependent manner in vivo and in vitro. The encapsulation of Q-Sepharose Fast Flow (QFF) gel particles by hemocytes in the treatment group was significantly higher than that in the control group at 1.5 h and 3 h post-treatment (P < 0.05). Moreover, the melanization ratio of QFF gel particles kept increasing with treatment time. The melanization rate at 24 h after treatment was significantly higher than that at other times (P < 0.05), reaching 55.33 %. Under the scanning electron microscope, BEA-treated larvae showed protrusions on the surface of their blood cells in vivo. Under the transmission electron microscope, it was observed that silkworm hemocytes were vacuolated. This study demonstrated that BEA had an effect on the blood cells of silkworms, and has thrown some light on the inhibitory effect and mechanism of BEA on insect cellular immunity.

Deacetylation of ACO2 Is Essential for Inhibiting Bombyx mori Nucleopolyhedrovirus Propagation

Bombyx mori nucleopolyhedrovirus (BmNPV) is a specific pathogen of Bombyx mori that can significantly impede agricultural development. Accumulating evidence indicates that the viral proliferation in the host requires an ample supply of energy. However, the correlative reports of baculovirus are deficient, especially on the acetylation modification of tricarboxylic acid cycle (TCA cycle) metabolic enzymes. Our recent quantitative analysis of protein acetylome revealed that mitochondrial aconitase (ACO2) could be modified by (de)acetylation at lysine 56 (K56) during the BmNPV infection; however, the underlying mechanism is yet unknown. In order to understand this regulatory mechanism, the modification site K56 was mutated to arginine (Lys56Arg; K56R) to mimic deacetylated lysine. The results showed that mimic deacetylated mitochondrial ACO2 restricted enzymatic activity. Although the ATP production was enhanced after viral infection, K56 deacetylation of ACO2 suppressed BmN cellular ATP levels and mitochondrial membrane potential by affecting citrate synthase and isocitrate dehydrogenase activities compared with wild-type ACO2. Furthermore, the deacetylation of exogenous ACO2 lowered BmNPV replication and generation of progeny viruses. In summary, our study on ACO2 revealed the potential mechanism underlying WT ACO2 promotes the proliferation of BmNPV and K56 deacetylation of ACO2 eliminates this promotional effect, which might provide novel insights for developing antiviral strategies.

Using silkworm excrement to restore vegetation and soil ecology in heavily contaminated mining soils by multiple metal(loid)s: A recyclable sericulture measure

Ecological restoration of heavily contaminated soils by multiple metal(loid)s in mining areas is very difficult. In this study, we provided an attractive measure of using silkworm excrement (SE) and its modified materials to restore the soil heavily contaminated by arsenic (As), antimony (Sb), cadmium (Cd), lead (Pb) and chromium (Cr). We investigated the adsorption capacities and the associated remediation mechanisms for antimonite [Sb(III)] and antimonate [Sb(V)] by raw SE, biochar-modified SE (BC700), iron-modified BC700 (MBC) and sulfhydryl-modified BC700 (SH). Then, we selected SE and SH to compare their outcomes to restore the vegetations and the soil bacterial communities in the investigated soil mentioned above. The results showed that SE displayed the best characteristics for metal(loid) physical adsorption. But SH conferred the strongest capacity to adsorb Sb (max 23.92 mg g-1), suggesting the process of chemical adsorption played a key role in adsorbing Sb via functional groups (-SH). SE and SH both significantly (1) promoted the growth of pakchoi (Brassica campestris L., New Zealand No.2), community abundance of soil bacteria (283-936 OTUs), and the quantity of bacterial genera correlated with resistance, plant growth promotion and specified carbon metabolism; (2) but reduced bacterial genera correlated with pathogenicity. In this study, we suggested an attractive recyclable measure to restore the disturbed ecological environment in mining areas, i.e, using mulberry to restore the vegetation→ using leaves of mulberry to rear silkworms→ using SE to immobilize metal(loid)s in soils growing mulberry or other plants.

The effects of polylactic acid bioplastic exposure on midgut microbiota and metabolite profiles in silkworm (Bombyx mori): An integrated multi-omics analysis

Polylactic acid (PLA) is a highly common biodegradable plastic and a potential threat to health and the environment. However, limited data are available on the effects of PLA exposure in the silkworm (Bombyx mori), a model organism used in toxicity studies. In this study, silkworms with or without PLA exposure (P1: 1 mg/L, P5: 5 mg/L, P25: 25 mg/L, and P0: 0 mg/L) for the entire 5th instar period were used to investigate the impact of PLA exposure on midgut morphology, larvae growth, and survival. Mitochondrial damage was observed in the P5 and P25 groups. The weights of the P25 posterior silk gland (5th day in the 5th instar), mature larvae and pupae were all significantly lower than those of the controls (P < 0.05). Dead worm cocoon rates and larva-pupa to 5th instar larvae ratios showed a positive and negative dose-dependent manner with respect to PLA concentrations, respectively. Additionally, reactive oxygen species levels and superoxide dismutase activity of the P25 midgut were significantly higher and lower when compared with controls, respectively (P < 0.05). The molecular mechanisms underlying the effects of PLA and associated physiological responses were also investigated. In the midgut metabolome, 127 significantly different metabolites (variable importance projection >1 and P < 0.05) were identified between the P0 and P25 groups and were mainly enriched for amino acid metabolism and energy supply pathways. The 16 S rDNA data showed that PLA altered microbial richness and structural composition. Microbiota, classified into 34 genera and 63 species, were significantly altered after 25 mg/L PLA exposure (P < 0.05). Spearman's correlation results showed that Bifidobacterium catenulatum and Schaalia odontolytica played potentially vital roles during exposure, as they demonstrated stronger correlations with the significantly different metabolites than other bacterial species. In sum, PLA induced toxic effects on silkworms, especially on energy- and protein-relevant metabolism, but at high concentrations (25 mg/L). This prospective mechanistic investigation on the effects of PLA on larval toxicity provides novel insight regarding the ecological risks of biodegradable plastics in the environment.

Comparative seasonal analysis of Eri silkworm (Samia ricini Donovan) gut composition: implications for lignocellulose degradation

Conversion of biomass such as lignocelluloses to an alternative energy source can contribute to sustainable development. Recently, biomass-degrading enzymes are reported to be common resources in insect-microbe interacting systems. Northeast India harbors ample sericigenous insect resources which are exploited for their silk products. Samia ricini Donovan is an economically important poly-phytophagous silkmoth capable of digesting foliage from different plant species, suggesting the versatility of a robust gut system. Here, a gut bacterial profile was determined by 16S rRNA gene characterization across the holometabolous life cycle during the summer and winter seasons, revealing 3 phyla, 13 families, and 22 genera. Comparative analysis among the seasonal gut isolates revealed a high diversity in summer, predominated by the genus Bacillus due to its high occurrence in all developmental stages. Shannon's diversity index demonstrated the second and fourth instars of summer as well as the fifth instar of winter to be relatively better developmental stages for gut bacteria assembly. Bacterial community shifts in concert to host developmental changes were found to be apparent between early instars and late instars in summer, which differed from those of winter. Forty-three and twenty-nine gut bacterial isolates were found to be cellulolytic and xylanolytic enzyme producers, respectively. The present results illustrate the gut microbiota of S. ricini over the seasons and support the holometabolous life cycle effect as the most likely factor shaping the gut bacterial microbiota. These findings may provide leads for the development of new cleaner and environmentally friendly lignocellulose-degrading enzymes.

The DEAD/H-box helicase DHX9 contributes to suppression of Bombyx mori nucleopolyhedrovirus propagation in B. mori cells

Antiviral immune responses are mainly triggered through the recognition of virus-derived nucleic acids by host-specific pattern recognition receptors (PRRs). Here, we identified and characterized homologs of human PRRs for virus-derived DNA in Bombyx mori upon infection with a nucleopolyhedrovirus (NPV), a member of the family Baculoviridae. We found that progeny virus production of B. mori NPV was promoted in B. mori cells silenced with B. mori homolog of DEAD/H box polypeptide 9 gene (Bm-DHX9), but not in cells silenced with the other examined genes. Silencing of Bm-DHX9 expression has no effect on apoptosis induction, one of the major antiviral responses in B. mori cells. We also showed that Bm-DHX9 has the ability to bind DNA containing unmethylated C-phosphate-G-motif, which are characteristic of microbial pathogens and contained in the NPV genome with high frequency. Our findings suggest that Bm-DHX9 has the potential for sensing NPV-derived DNA to induce antiviral immune responses.

The RNase III enzyme Dicer1 is essential for larval development in Bombyx mori

MicroRNAs (miRNAs) are important regulators of nearly all aspects of biological processes in eukaryotes. During the biogenesis of miRNAs, the RNase III enzyme Dicer processes double-strand precursor miRNAs into mature miRNAs and promotes the assembly of RNA-induced silencing complexes (RISCs). Dicer has been reported to participate in a wide range of physiological processes, including development and immunity, in some insect species. However, the physiological roles of Dicer in lepidopterans remain poorly understood. In this study, we investigated the function of Bombyx mori Dicer1. We first performed sequence alignment and found that the sequence of functional domains of Dicer1 are varied among Lepidoptera, Diptera, Coleoptera, Blattaria, and Orthoptera. Using a binary clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated protein 9 genome editing approach, we showed that BmDicer1 mutants have arrested development from the 3rd instar into the 4th instar. RNA sequencing analysis indicated that the defects in BmDicer1 mutants are due to dysregulation of genes that encode proteins involved in metabolism, protein degradation, absorption, and renin-angiotensin pathways. Analysis using quantitative real-time polymerase chain reaction showed that mutation of BmDicer1 altered expression of miRNAs and their target genes. Therefore, our study demonstrates the critical roles of BmDicer1 in miRNA biogenesis and larval development in silkworm.

Ice Recrystallization Inhibition Activity of Silk Proteins

The cryopreservation of cells, tissue, and organs is essential in both fundamental research and practical applications, such as modern regenerative medicine and technological applications. However, the formation of ice crystals during ice recrystallization can have harmful or even fatal effects on biological systems. To address this challenge, we explore the ice recrystallization inhibition (IRI) activity of two natural silk proteins of Bombyx mori, fibroin and sericin. We found that silk fibroin (SF) had higher ice recrystallization inhibition activity than silk sericin (SS). Moreover, SF aqueous solutions perform better in inhibiting ice recrystallization than SF phosphate-buffered saline solutions. Sum-frequency generation spectroscopy shows that stronger electrostatic interactions are responsible for the higher IRI ability of SF. This work is significant for broadening the applications of silk proteins in biomedical fields.

Short-term triphenyltin exposure alters microbial homeostasis in the silkworm (Bombyx mori) midgut

Triphenyltin (TPT) is a widespread synthetic chemical used in many fields and its potential risk to organisms has been comprehensively investigated using different animal models and species. Currently, little is known about the effects of TPT exposure on microbial midgut diversity, therefore we explored these effects in the lepidopterous silkworm model using 16S rDNA sequencing. In total, 5273 and 5065 operational taxonomic units (OTUs) were identified in control and TPT-exposure group samples, ranging from 424 to 728 OTUs/sample. Alpha-diversity analyses revealed that TPT exposure induced the fluctuations of gut microbial diversity and abundance while beta-diversity analyses identified a distinct impact on major gut microbiota components. In our microbiome analyses, 23 phyla and 353 genera were recognized in the control group, while 20 phyla and 358 genera were recognized in the TPT exposure group. At the genus level, midgut microbiota were composed of several predominant bacterial genera, including Muribaculaceae, Lactobacillus, and UCG-010. In the TPT exposure group, o__Bacillales, f__Bacillaceae, and f__Caldicoprobacteraceae abundance was relatively high, while f__Oscillospiraceae, f__Fusobacteriaceae, and f__SC_I_84 abundance was relatively high in the control group. Gene function analyses in silkworm microbiota after TPT exposure showed that biosynthesis of ansamycins, fructose and mannose metabolism, glycerolipid metabolism, type II diabetes mellitus, glycolysis/gluconeogenesis, lipid metabolism, translation proteins, atrazine degradation, DNA repair and recombination proteins, nicotinate and nicotinamide metabolism were significantly increased. Collectively, our silkworm model identified gut microbial diversity risks and the adverse effects from TPT exposure, which were similar to other aquatic animals. Therefore, TPT levels in environmental samples must be monitored to prevent ecological harm.

Unique Material Properties of Bombyx mori Silk Fiber Incorporated with 3-Azidotyrosine

Silk fiber produced by the silkworm Bombyx mori is a nature-derived proteinous fiber with excellent mechanical strength and broad biocompatibility. To alter its material properties and make it more suitable for textile, biomedical, and electronics applications, chemical modifications and genetic engineering methods have been extensively studied. Here, we report that the translational incorporation of a synthetic amino acid, 3-azidotyrosine (3-AzTyr), into B. mori silk fiber can improve its material properties. Such an incorporation considerably increased the fiber's mechanical strength and remarkably changed its solubility, whereas its crystalline hierarchical structure was not perturbed, as shown by X-ray analyses. These changes were probably caused by the intra- and/or intermolecular crosslinkings involving the azido group of 3-AzTyr during the degumming process to remove a coating protein. These findings indicate that the incorporation of synthetic amino acids could be an efficient method to improve the properties of silk-based materials.

Mulberry Leaves (Morus Rubra)-Derived Blue-Emissive Carbon Dots Fed to Silkworms to Produce Augmented Silk Applicable for the Ratiometric Detection of Dopamine

Silk fibers (SF) reeled from silkworms are constituted by natural proteins, and their characteristic structural features render them applicable as materials for textiles and packaging. Modification of SF with functional materials can facilitate their applications in additional areas. In this work, the preparation of functional SF embedded with carbon dots (CD) is reported through the direct feeding of a CD-modified diet to silkworms. Fluorescent and mechanically robust SF are obtained from silkworms (Bombyx mori) that are fed on CDs synthesized from the Morus rubra variant of mulberry leaves (MB-CDs). MB-CDs are introduced to silkworms from the third instar by spraying them on the silkworm feed, the mulberry leaves. MB-CDs are synthesized hydrothermally without adding surface passivating agents and are observed to have a quantum yield of 22%. With sizes of ≈4 nm, MB-CDs exhibited blue fluorescence, and they can be used as efficient fluorophores to detect Dopamine (DA) up to the limit of 4.39 nM. The nanostructures and physical characteristics of SF weren't altered when the SF are infused with MB-CDs. Also, a novel DA sensing application based on fluorescence with the MB-CD incorporated SF is demonstrated.