Araneus Ventricosus Research Articles

Insights into the Evolutionary Dynamics: Characterization of Disintegrin and Metalloproteinase Proteins in the Venom Gland Transcriptome of the Hemiscorpius lepturus Scorpion.

The Disintegrin and Metalloproteinase (ADAM) family, also known as the metalloproteinase/disintegrin/cysteine-rich (MDC) proteins, includes both secreted and transmembrane molecules involved in critical biological processes, such as cell migration, adhesion, and signaling. This study aimed to investigate the evolutionary relationships and structural characteristics of disintegrin and metalloproteinase proteins identified in the venom gland transcriptome of the scorpion Hemiscorpius lepturus. Using bioinformatics tools, we analyzed the open reading frame, conserved motifs, and primary, secondary, and tertiary structures of these proteins. Five proteins, named HLDis- Met1, HLDisMet2, HLDisMet3, HLDisMet4, and HLDisMet5, were identified. Their predicted 3- D structures were within normal ranges (Z-score between -4 to -9). Phylogenetic analysis revealed that HLDisMet1 shares similarities with proteins from various spider species (Nephila pilipes, Argiope bruennichi, Araneus ventricosus, and Trichonephila inaurata madagascariensis), HLDisMet2 with the scorpion Centruroides sculpturatus, HLDis- Met4 with the scorpion Tityus serrulatus, and HLDisMet5 with several snake species (Python bivittatus, Vipera anatolica senliki, Protobothrops mucrosquamatus, and Naja naja). These findings highlight the significant similarities between HLDisMet proteins and those found in other venomous species, suggesting a complex and diverse evolutionary pathway for venom components. The cross-species conservation observed may indicate a convergent evolutionary strategy, where different species independently develop similar venom components to adapt to similar ecological niches or prey types. This study highlights the evolutionary significance of venom diversification and its potential applications in understanding venom biology across different species.

Spiders manipulate and exploit bioluminescent signals of fireflies

Predators often search for prey while moving through the environment, but there are important exceptions, including the way sedentary predators sometimes rely on signals for drawing prey to within striking distance1,2. Some spiders, for instance, leave the remnants of previously-captured prey in their webs where they function as static lures that effectively attract a diverse array of additional prey3456. However, important questions remain concerning how specific the targeted prey may be and how dynamic, instead of static, signalling might be. With these questions as our rationale, we initiated research on Araneus ventricosus (L. Koch, 1878), an orb-weaving spider, as the predator and the firefly Abscondita terminalis males as the prey (Figure 1A-C). Using two lanterns situated on their abdomen (Figure 1D,F), A. terminalis males make female-attracting multi-pulse flash trains (Figure 1J), whereas sedentary females attract males by making single-pulse signals (Figure 1C,K) with a single lantern (Figure 1E,G). Drawing from extensive field observations, we propose that A. ventricosus practices deceptive interspecific communication by first ensnaring firefly males in its web and then predisposing the entrapped male fireflies to broadcast bioluminescent signals that deviate from female-attracting signals typically made by A. terminalis males and instead mimic the male-attracting signals typically made by females. The outcome is that the entrapped male fireflies broadcast false signals that lure more male fireflies into the web.

Dragline silk fibers from golden orb‐web spider Trichonephila clavata ensure structural and mechanical robustness against ultraviolet radiation

AbstractA diurnal spider, Trichonephila clavata (T. clavata), is often called a golden orb‐weaver because its dragline or lifeline silk fibers exhibit a golden color. However, little is known about the biological roles of the golden pigment. Meanwhile, Araneus ventricosus, which is a nocturnal spider, spins colorless silk fibers. Here, we investigated the effect of ultraviolet (UV) irradiation on physical properties of silk fibers obtained from these diurnal and nocturnal spiders. After UV exposure, the dragline silk of the nocturnal spiders appeared abraded and became insoluble due to gelation, whereas the diurnal spider silk remained intact. A dynamic mechanical thermal analysis under different humidity conditions revealed that the storage modulus of the silk from the nocturnal spider dropped markedly at low humidity levels after UV irradiation. This indicated that the molecular weight of this silk degraded under UV exposure and that the number of terminal amino and carboxyl groups increased due to the breakage of the main protein chains. In contrast, the structural and mechanical properties of the diurnal spider silk were maintained regardless of the UV irradiation. Therefore, the golden pigments in the dragline silk of T. clavata most likely played a role in protecting the silk from UV damage.

Electrospun mini-MiSp spidroin/poly(L-lactide-co-ε-caprolactone) nanofibrous scaffolds for ARPE-19 cells

Age-related macular degeneration, a type of retinal degenerative disease, is the primary cause of severe visual impairment and irreversible blindness in people older than 50, due to age-related deterioration of the photoreceptors and the retinal pigment epithelium (RPE), which could be restored by cell therapy. However, the success of cell therapy depends on biocompatible scaffolds, which serve as carriers for the growth of RPE cells for repairing damaged or diseased retinas. In this study, the plasmid pET-SUMO-R2C for expressing a mini-spidroin, fusing the second repetitive region to the C-terminal domain of the minor ampullate spidroin gene from the spider Araneus ventricosus, was constructed and named R2C. The spidroin R2C was expressed, purified and wet spun into silk-like fibers, possessing a Young’s modulus of 3.51 ± 0.92 GPa and toughness of 24.67 ± 9.51 MPa. The spidroin R2C, mixed with poly(L-lactide-co-ε-caprolactone) (PLCL) at a ratio of 3:1, was electrospun into nanofibrous scaffolds, composed of nanometric fibers with a diameter of 751.70 ± 19.48 nm. After co-culturing with the R2C/PLCL scaffolds, the transcriptomic differences of the ARPE-19 cells were analyzed, showing that fourteen genes that are mainly related to inflammation, tumors and keratinization were upregulated more than three times, while seven genes that are mostly related to substance transport and homeostasis were downregulated more than three times. The R2C/PLCL scaffolds have the potential to be further studied to serve as a suitable carrier for RPE transplantation in the future.

Complete gene sequence and mechanical property of the fourth type of major ampullate silk protein.

Spiders spin a great diversity of silk types for daily survival and reproduction. Of the six orb-weaver silk types, the dragline silk forming orb web frame attracts the most attention because of its extremely high tensile strength and toughness. So far, four types of major ampullate silk proteins (MaSp1-4) that make up dragline silk have been identified. These MaSp types have diversified amino acid motifs that underlie the impressive mechanical property of dragline silk by forming particular structures. Existing knowledge of MaSp4 proteins is fragmented, making it difficult to illuminate the structure and function of MaSp4. Here, we report the full-length MaSp4 gene with 11,334 bp from the orb-weaving spider Araneus ventricosus. Removing the only intron, the spliced complete transcript of MaSp4 gene is 6897 bp and encodes 2298 amino acids. Analysis of the primary structure of A. ventricosus MaSp4 protein reveals the repetitive region lacks poly-A and GGX motifs but has the unique GPGPQ motifs. Quantitative real-time PCR analyses show high levels of MaSp4 mRNA were detected in major ampullate gland. Structural characterization using CD- and FTIR sepctroscopy reveals a mainly α-helical solution conformation and a very high β-turn content within fibers. Collectively, our new findings provide complete template for recombinant silk protein with specific properties and support that the GPGPQ motif found in MaSp4 could increase flexibility in dragline silk by packing in more β-turns, expanding the repertoire of sequences known to form β-turn that is available for artificial chimeric silk fibers. STATEMENT OF SIGNIFICANCE: Dragline silk forming orb web frame attracts the most attention because of its extremely high tensile strength and toughness. So far, four types of major ampullate silk proteins (MaSp1-4) that make up dragline silk have been identified. Existing knowledge of MaSp4 proteins is fragmented, making it difficult to illuminate the structure and function of MaSp4. Here, we report the full-length MaSp4 gene from the orb-weaving spider Araneus ventricosus. We further identify the sequence, structure, and mechanical property of MaSp4 protein, providing a new insight into the structure-funtion relationships associated with MaSp4. Collectively, our new findings provide complete template for recombinant silk protein with specific properties and support that the GPGPQ motif found in MaSp4 could increase flexibility in dragline silk by packing in more β-turns, expanding the repertoire of sequences known to form β-turn that is available for artificial chimeric silk fibers.

Long-period fiber grating humidity sensor based on spider silks

We propose a long-period fiber grating (LPFG) humidity sensor based on two kinds of spider silks. Both spider dragline silk (SpDS) and spider egg-case silk (SpECS) for sensor preparation are produced by the Araneus ventricosus. SpDS can contract up to half the original length in the axial direction when the ambient relative humidity (RH) increases due to its supercontraction property. However, the length of SpECS axial contraction is much smaller than that of SpDS as RH increases, because SpECS does not have the supercontraction property like SpDS. We fabricated a LPFG by irradiating a single-mode fiber with a high-frequency CO2 laser. One end of LPFG is fixed by ultraviolet glue, and the other end is inserted into the quartz round tube without fixing. Therefore, the unfixed end of LPFG serves as the movable end to ensure that the direction of movement of LPFG is controllable. In addition, SpDS and SpECS exert pull forces on LPFG in two opposite directions, and the overall structure forms an X shape. When the ambient RH increases, the length of SpDS becomes shorter due to the supercontraction property. It changes the structure curvature of LPFG, leading to the transmission spectrum shift. When the RH decreases, SpECS provides a recovery pull, like a spring, that restores SpDS to a taut state when it relaxes. The curvature of LPFG is reduced, and the transmission spectrum shifts in the opposite direction. Therefore, we monitor the RH by observing the wavelength shift of the transmission spectrum. Our sensor achieves humidity detection with − 0.2039 nm/%RH sensitivity in the 50%RH-80%RH range. Additionally, we can adjust the amount and length of the two spider silks to increase the maximum detection humidity range closer to 100% RH at the expense of reduced sensitivity. The proposed humidity sensor has the advantages of reversibility, good repeatability, and environmental friendliness.

Characterization of two full-length Araneus ventricosus major ampullate silk protein genes

Major ampullate silk is noted for its great tensile strength and extensibility. The impressive material properties of major ampullate silk result from their component proteins that encoded by members of the spidroin (spider fibroin) gene family. Although the major ampullate spidroin type has evolved multiple variants within specific-species, most sequences are fragmented. Here, we present two complete major ampullate spidroin genes from the orb-weaving spider Araneus ventricosus. Due to the abundant GPG motifs in their repetitive region, the two MaSp genes were grouped in MaSp2 subclass and named MaSp2C and MaSp2D, respectively. Analysis of the full-length gene sequences reveals that both of them include a single enormous exon (10,851 bp for MaSp2C and 8640 bp for MaSp2D) that mainly translates into a central repetitive region containing multiple amino acid motifs that can be organized into five ensemble types. We use gene-specific PCR primers to search the cDNA from major ampullate glands and find evidence for alternative splicing of MaSp2D transcripts into a minor spliceoform lacking the entire repetitive domain as well as the partial terminal regions. Our results not only provide new templates for protein-based materials with tailored properties, but suggest gene and transcriptional diversity of major ampullate silk.

Unveiled chromosomal diversity in the Araneidae (Araneomorphae): the highest diploid number among entelegynes and the first record of the X1X2X3X4 Sex Chromosome System in the family

The Araneidae is among the most speciose spider families, but there are few karyotype studies (1.9%) and some species-rich clades are without any chromosomal study. Understanding the evolution of chromosome number and Sex Chromosome Systems is made more difficult by many uncertain evolutionary relationships within the family. In this work, the chromosomal analysis of eight araneid species (Acacesia benigna Glueck, 1994, Actinosoma pentacanthum (Walckenaer, 1841), Alpaida bicornuta (Taczanowski, 1878), Dubiepeira Levi, 1991 sp., Gasteracantha cancriformis (Linnaeus, 1758), Parawixia bistriata (Rengger, 1836), Verrucosa meridionalis (Keyserling, 1892) and Verrucosa scapofracta Lise, Kesster & Silva, 2015), contribute to discussions of some evolutionary scenarios of chromosome evolution. The gonads were submitted to colchicine treatment, hypotonization, slide preparation, and Giemsa staining. The species analyzed showed 2n♂ = 24 (11II + X1X2), except Dubiepeira sp. with 2n♂ = 41 (19II + X1X2X3), and both Verrucosa species, which presented 2n♂ = 47 (22II + X1X2X3) in V. meridionalis and 2n♂ = 50 (23II + X1X2X3X4) in V. scapofracta. The species analyzed possess all chromosomes with acro/telocentric chromosomal morphology. The 2n♂ = 24, X1X2 found in most species studied here is the most frequent karyotype in the Araneidae. This study presents the first chromosomal data for the diverse clade “Micrathenines”, the highest diploid number among entelegynes (2n♂ = 50), and the first record of an X1X2X3X4 in the Araneidae. The chromosome data suggest a series of fission events in the origin of Verrucosa karyotypes, and a close relationship between Dubiepeira sp. and Araneus ventricosus (L. Koch, 1878). Moreover, Alpaida bicornuta can be cytotaxonomically distinguished of other Alpaida species karyotyped up to now.

The novel aciniform silk protein (AcSp2-v2) reveals the unique repetitive domain with high acid and thermal stability and self-assembly capability

Orb-weaving spiders spin a mechanically and functionally diverse range of silk fibers, each composed of one or more specific silk proteins. Of all silk types, wrapping silk combines high strength and extensibility and is made of multiple aciniform silk proteins (AcSp) that can be grouped into two AcSp types (AcSp1 and AcSp2) according to their distinct repetitive regions. Here, we present a novel and complete AcSp gene from orb weaving spider Araneus ventricosus. Phylogenetic analysis of the terminal regions of spidroins reveals that the new silk protein and the published A. ventricosus AcSp2 together form a subclade, indicating that this protein is a member of AcSp2 subclass and therefore named AcSp2 variant 2 (AcSp2-v2). The repetitive region of A. ventricosus AcSp2-v2 contains 24 cysteine residues, which is the first time that cysteine has been found in repetitive regions of spidroins. Moreover, the discovery of the ability of AcSp2-v2 repetitive domain to self-assemble into silk fibers expands the repertoire of known self-assembling sequences.

Spider dragline silk for PH sensing

We develop a fiber pH sensor using a spider dragline silk (SDS). SDS obtained from an Araneus Ventricosus is a pH-sensitive natural protein. We wrap the SDS on a tapered single-mode optical fiber (TSOF) to fabricate the sensing structure. The fiber taper is too thin to confine the laser propagating in the fiber, leading to the leakage of the strong evanescent field. Therefore, the higher-order modes will couple to the SDS, and we may obtain a multimode interference (MMI) spectrum. The pH of the solution will change the protein structure of the SDS. Thus, the effective refractive index (RI) of the SDS will vary with pH. Therefore, the change of pH causes the shift of the MMI spectrum. The pH detection range is 6.5 to 7.9. Compared with other PH sensors, the materials used in this sensor are biocompatible and the sensitivity of this sensor is competitive. The maximum pH sensitivity is as high as 7.7 nm of wavelength shift per pH level. In our experiment, the resolution of optical spectrum analyze is 0.2 nm. Therefore, the pH change that corresponds to the minimum detectable wavelength shift is 0.03. The sensor is low in cost, environmental-friendly, and has good repeatability.

Spider Silk Fibroin Protein Heterologously Produced in Rice Seeds Reduce Diabetes and Hypercholesterolemia in Mice.

Silk fibroin proteins are biomaterials with diverse applications. These spider and silkworm proteins have specific biological effects when consumed by mammals; in addition to reducing blood pressure and blood glucose and cholesterol levels, they have anti-human immunodeficiency virus activity. In the present study, rice (Oryza sativa) was engineered to produce the C-terminus of the major ampullate spidroin protein from the spider Araneus ventricosus under the control of a Prolamin promoter. Homozygous transgenic rice lines were identified, and the therapeutic effect of this spider silk fibroin protein on the lipid and glucose metabolism was analyzed in a mouse model. Feeding fat-fed mice, the transgenic rice seeds for four weeks reduced serum concentrations of triglycerides, total cholesterol, low-density lipoprotein cholesterol, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase, and lowered blood glucose levels. This is the first study to investigate the effects of consumption of rice seeds heterologously expressing spider silk fibroin protein in a mammalian model. Our findings suggest that functional foods containing spider silk fibroin protein might be useful as potential pharmaceutical materials for preventing and treating diabetes, hyperlipidemia, and hypercholesterolemia

Characterization of the second type of aciniform spidroin (AcSp2) provides new insight into design for spidroin-based biomaterials

Spiders spin a range of silks from different glands for distinct functions, and each silk type exhibits distinct material properties. Silk extruded by the aciniform gland is used for prey wrapping and egg case construction and displays high toughness and extensibility. So far, only the aciniform spidroin 1 (AcSp1) gene which was firstly identified as a silk gene in aciniform gland has been obtained. Here we present the gene sequence for the second type of full-length aciniform silk protein, AcSp2. Analysis of the AcSp2 primary sequence reveals relatively conserved terminal regions and a distinct repetitive sequence relative to AcSp1. A fraction of the gene can be expressed in recombinant systems. Secondary structure analysis of the recombinant AcSp2 protein in solution reveals that the protein adopts mainly an α-helical conformation. Artificial spinning of recombinant AcSp2 demonstrates that the spidroins can be spun into fine fibers which display up to 142% extensibility. The silk fibers are dominated by β-sheet and β-turn secondary structures. Moreover, the mechanical data collected from these synthetic fibers revealed that the mechanical properties are partly correlated with the molecular weights. Overall, our studies enrich our knowledge of spidroin gene family members and provide a new insight into creation of high-performance silk fibers for next generation biomaterials. Statement of SignificanceIn this study, we presented the second type of aciniform silk protein (AcSp2) gene sequence of orb-weaving spider Araneus ventricosus, expanding the spider silk gene family members. The primary structure revealed the central repetitive sequence of the new spidroin gene is distinctly different from other AcSp1 genes. Characterization of the recombinant minispidroin fibers of AcSp2 revealed the mechanical properties are partly correlate with the molecular weights, and the spidroins can be spun into fine fibers which display up to 142% extensibility. Overall, our studies enrich our knowledge of spidroin gene family members and provide a new insight into creation of high-performance silk fibers for next generation biomaterials.

Two novel tubuliform silk gene sequences from Araneus ventricosus provide evidence for multiple loci in genome

Spiders produce a diversity of silk fibers from multiple morphologically distinct silk glands for specific tasks, and each silk type primarily composed of one or more particular silk proteins encoded by silk gene family members believed to generated by duplication and divergence of ancient silk genes. Egg case silks spun from tubuliform glands are used to construct the tough outer structure of egg cases, are important for their reproduction. Here we present two novel complete TuSp1 sequences from orb weaving spider Araneus ventricosus. Alignment of the two spidroin iterated repeats showed both extreme intragenic homogenization. The pairwise Ka/Ks analysis revealed the terminal and repetitive regions for three TuSp1 loci including the reported TuSp1 gene are all under purifying selection. Phylogenetic analysis showed the two new TuSp1 variants could derive from recent duplication events.

The three novel complete aciniform spidroin variants from Araneus ventricosus reveal diversity of gene sequences within specific spidroin type

Orb-weaving spiders produce multiple types of silks with distinct functions and material features, and all these silks are mainly composed of proteins which encoded by specific spidroin (spider silk protein) gene family members. Moreover, nearly all spidroins have evolved one or more variants within specific-species. However, the majority of variant sequences are fragmentary, limiting us to investigate the molecular structures and evolution relationships between spidroin variant genes. As the silk that is used to wrap prey and form an egg case liner, aciniform silk is given high toughness and tensile strength. To date, only one aciniform spidroin 1 (AcSp1) gene sequence from orb weavers Araneus ventricosus was reported, and it is still unknown whether presence of multiple AcSp1 variants in this species. Here, we present three novel complete AcSp1 variant gene sequences from Araneus ventricosus. The primary structures revealed the varying length of these variants, and partial repetitive sequences of two AcSp1 variants were deleted. Phylogenetic analysis showed AcSp1 seems to undergo multiple rounds of gene duplication, and the AcSp1-v4 likely originates from a recent duplication event. In brief, the generation of multiple AcSp1 variant genes contributes to transcript diversification and could result in varying tensile properties of aciniform silks.

Accumulation of cesium in glue balls of spiders' orb webs

Spiders capture prey by applying sticky coating substances to the spiral line of their orb webs. The main constituents of these sticky substances are glycoproteins and salts. This sticky substance is an intelligent material. Salt plays a key role regarding the properties of the sticky substance. Spiders typically weave a new orb webs by recycling used orb webs, and salts, typically salts of the alkali metals sodium and potassium, were therefore assumed to be recycled in this process. Here, we fed cesium (Cs) carbonate (which is an alkali metal salt) to spiders (Araneus ventricosus) to test this hypothesis. After feeding, we mapped the sticky substance in the spiders' orb web using an in‐house time‐of‐flight secondary ion mass spectrometer with high lateral resolution. The results showed that Cs ion was ingested and integrated into the sticky substance, and it showed properties similar to those of sodium ion and potassium ion.

Complete mitogenomes of two orb-weaver spiders, Argiope bruennichi and Araneus ventricosus

We performed high-throughput sequencing on the complete mitogenomes of two Araneidae species, a wasp spider (Argiope bruennichi) and a large nocturnal spider (Araneus ventricosus). The two mitogenomes contain 14,060 bp and 14,607 bp, and GC content of 26.6% and 26.5%, respectively. The two mitogenomes contain 13 protein-coding genes (PCGs), 22 transfer RNAs, 2 ribosomal RNAs, and 1 control region. We performed a phylogenetic analysis with the concatenated 13 PCGs, which showed that Argiope and Araneus are clearly classified and clustered within Araneidae clade. Our study serves to enrich evolutionary and ecological studies.

ПАУКИ-КРУГОПРЯДЫ (ARANEI: ARANEIDAE) ОСТРОВА АСКОЛЬД (ЗАЛИВ ПЕТРА ВЕЛИКОГО, ПРИМОРЬЕ)

The fauna of spiders on the islands of the Peter the Great Gulf in the south of the Far East is poorly studied. Data on the species composition, abundance and biotopic distribution of orb-weaver spiders (Aranei: Araneidae) of Askold Island are given in the paper for the first time. The island is located in the Peter the Great Gulf in the south of Primorskii krai. The material was collected in autumn of 2014, 2015 and in August 2016. In autumn, random collection of spiders was made. In summer 2016, 21 key sites were selected on the island. The size of each site is 3×25 m. The spiders were collected using a sweeping method supplemented with a manual method. The biotopic correspondence of 12 species of spiders belonging to 7 genera was revealed. It has been established that the distribution of spiders throughout the island is uneven. The greatest diversity is noted in broad-leaved polydominant forests. Araneus ventricosus (L. Koch, 1878) whose density reaches 15 specimens per 100 m2 dominates there. Rocky beaches have the lowest species diversity. The only species is found there – A. ventricosus (density 4 specimens per 100 m2). Only Neoscona adianta (Walckenaer, 1802) (density 10 specimens per 100 m2) inhabits the swampy area with sedges. The map of the density of orb-weaver spiders has been compiled on the basis of original data of the author and satellite images. This map allows to estimate the distribution and density of population of spiders over the area of Askold island in the summer. Alenatea cf. wangi Zhu et Song, 1999 and Pronoides brunneus Schenkel, 1936 are recorded on the islands of the Peter the Great Gulf for the first time.

The molecular structure of novel pyriform spidroin (PySp2) reveals extremely complex central repetitive region

Orb-weaving spiders produce a diversity of silk fibers throughout their entire lifecycle, and each silk type is given a specific purpose. As a dry fiber material with wet glue, pyriform silks are different from other silk fibers and make the attachment discs which are used for bonding fibers together and attaching dragline silk to other substrates. To date, only two full-length pyriform spidroin 1 (PySp1) gene sequences were identified. Here we present a novel full-length pyriform spidroin 2 (PySp2) from orb-weaving spider, Araneus ventricosus. Although the A. ventricosus PySp2 lack the long linker regions, the central repetitive region of PySp2 is more complex than PySp1 and can be classified into four types of repetitive regions including three novel repetitive sequences and one type of repetitive region that is similar to PySp1 repeats. Prediction of hydrophobicity of A. ventricosus PySp2 reveals the two new repetitive regions display strong hydrophilicity. Analysis of CD spectrum and secondary structure prediction for A. ventricosus PySp2 repeat unit reveal α-helix conformation dominates the repetitive region. Furthermore, recombinant protein-based artificial fibers show the single repeat unit is sufficient for self-assembling into silk fiber.

Natural spider silk as a photonics component for humidity sensing.

Biological microfibers are remarkable materials with diversity in their chemistry, structure and functions that provide a range of solutions for photonic structures. Here we proposed and demonstrated a humidity detection technique for spectral tuning of whispering gallery modes (WGMs) in a cylindrical microresonator formed by a piece of spider egg sac silk (SpEss) from Araneus Ventricosus. We launched a supercontinuum laser into the SpEss via a tapered single-mode fiber to excite WGMs. When the ambient humidity changed, the profile diameter and effective refractive index of the SpEss changed, which caused the WGM resonant dips to shift. The experimental results showed that when the relative humidity (RH) changed from 20% to 75% RH, the average testing sensitivity of the proposed sensor was 389.1 pm/%RH and the maximum testing sensitivity was 606.7 pm/%RH in the range of 60% to 75% RH. Also, the proposed SpEss-based humidity sensor showed a fast response time of 494 ms and good repeatability with fluctuations less than 8% compared with the initial test values. The SpEss-based sensor expanded the application of spider silk as a biodegradable and biocompatible material in biochemical sensing.

Spider silk-based humidity sensor

We select a section of spider egg sac silk (SESS) from an Araneus ventricosus for humidity sensing. SESSs are composed of tubiliform fibers, which suggests that the silk fibroin is more sensitive to ambient humidity. We employ a section of single mode fiber (SMF) and a section of SESS to configure an interference-cavity structure. The change of ambient humidity will cause a change in the SESS diameter, which will change the length of the interference-cavity. The change of the interference-cavity length will cause the interference spectrum to redshift, and the SESS-based sensor will perform the humidity-sensing characteristic. The testing results indicate that the higher the ambient humidity, the higher the sensitivity. The maximum value of the sensitivity is 0.99 nm/%RH in the humidity range of 90%–99%. The sensor is protected from temperature disturbance, and the temperature sensitivity is 33 pm/°C. Spider silk is a kind of natural moisture-sensitive material, which is environmentally friendly and does not demand additional sensitization. Therefore, the spider silk is very promising candidates for optical-based chemical and biological sensors that are biocompatible, biodegradable, and highly sensitive.