Free-standing spider silk webs of the thomisid Saccodomus formivorus are made of composites comprising micro- and submicron fibers.

Our understanding of the extraordinary mechanical and physico-chemical properties of spider silk is largely confined to the fibers produced by orb-weaving spiders, despite the diversity of foraging webs that occur across numerous spider families. Crab spiders (Thomisidae) are described as ambush predators that do not build webs, but nevertheless use silk for draglines, egg cases and assembling leaf-nests. A little-known exception is the Australian thomisid Saccodomus formivorus, which constructs a basket-like silk web of extraordinary dimensional stability and structural integrity that facilitates the capture of its ant prey. We examined the physical and chemical properties of this unusual web and revealed that the web threads comprise microfibers that are embedded within a biopolymeric matrix containing additionally longitudinally-oriented submicron fibers. We showed that the micro- and submicron fibers differ in their chemical composition and that the web threads show a remarkable lateral resilience compared with that of the major ampullate silk of a well-investigated orb weaver. Our novel analyses of these unusual web and silk characteristics highlight how investigations of non-model species can broaden our understanding of silks and the evolution of foraging webs.

Recombinant Spider Silk and Collagen-Based Nerve Guidance Conduits Support Neuronal Cell Differentiation and Functionality in Vitro.

Biomaterial scaffolds are under investigation as therapeutic tools to bridge nerve endings following traumatic peripheral nerve injury. The goal is to develop biocompatible nerve guidance conduits (NGCs) with internal guiding structures that promote longitudinally oriented cell migration and regeneration. In the present study, a nonwoven mesh (NWM) made of a recombinant spider silk protein was processed into a tubular structure, ensuring structural integrity of enclosed microfluidics-produced collagen fibers for cell and neurite guidance. The differentiated type of the neuroblastoma X glioma hybrid cell line NG108-15 was used as a model for studying neuronal differentiation on the individual components and on the complete NGC. Differentiated NG108-15 cells grown on recombinant spider silk NWM and collagen fibers formed neuronal networks and synapses. Additionally, whole-cell patch clamp recordings confirmed that all components supported the differentiation of NG108-15 cells into functional neurons. Our NGC demonstrated that tubes made of recombinant spider silk NWM filled with microfluidics-produced collagen fibers are well suited for peripheral nerve repair.

Microfluidic nozzle device for ultrafine fiber solution blow spinning with precise diameter control.

We present a microfluidic nozzle device for the controlled continuous solution blow spinning of ultrafine fibers. The device is fabricated by soft lithography techniques and is based on the principle of a gas dynamic virtual nozzle for precise three-dimensional gas focusing of the spinning solution. Uniform fibers with virtually endless length can be produced in a continuous process while having accurate control over the fiber diameter. The nozzle device is used to produce ultrafine fibers of perfluorinated copolymers and of polycaprolactone, which are collected and drawn on a rotating cylinder. Hydrodynamics and mass balance quantitatively predict the fiber diameter, which is only a function of flow rate and air pressure, with a small correction accounting for viscous dissipation during jet formation, which slightly reduces the jet velocity. Because of the simplicity of the setup, the precise control of the fiber diameter, the positional stability of the exiting ultrafine fiber and the potential to implement arrays of parallel channels for high throughput, this methodology offers significant benefits compared to existing solution-based fiber production methods.

Microfluidics-Produced Collagen Fibers Show Extraordinary Mechanical Properties.

Collagens are widely used as biomaterials in drug-delivery and tissue engineering applications due to their biodegradability, biocompatibility and hypoallergenicity. Besides gelatin-based materials, collagen microfibers are in the focus of biomedical research. Commonly, man-made fibers are produced by wet-spinning yielding fiber diameters higher than 8 µm. Here, assembly and continuous production of single collagen type I microfibers were established using a microfluidic chip. Microfluidics-produced microfibers exhibited tensile strength and Young's modulus exceeding that of fibers produced in classical wet-spinning devices and even that of natural tendon and they showed lower diameters. Their structural orientation was examined by polarized Fourier transform infrared spectroscopy (FTIR) showing fibril alignment within the microfiber. Cell culture tests using the neuronal cell line NG108-15 showed cell alignment and axon growth along the microfiber axes inaugurating potential applications in, for example, peripheral nerve repair.

Endocytosis of GABA(C) receptors depends on subunit composition and is regulated by protein kinase C-ζ and protein phosphatase 1.

Neuronal excitability depends on the surface concentration of neurotransmitter receptors. Type C gamma-aminobutyric acid receptors (GABA(C)R) are composed of ρ subunits that are highly expressed in the retina. Molecular mechanisms that guide the surface concentration of this receptor type are largely unknown. Previously, we reported physical interactions of GABA(C)R ρ subunits with protein kinase C-ζ (PKCζ) via adapter proteins of the ZIP protein family, as well as of protein phosphatase 1 (PP1) via PNUTS. Here, we demonstrate that co-expressing ρ1 with ZIP3 and PKCζ enhanced basal internalization of GABA(C)R, while receptor internalization was reduced in the presence of PNUTS and PP1. Co-expression of ρ1 with individual binding partners showed no alterations, except for PP1. Heterooligomeric GABA(C)R composed of ρ1 and ρ2 subunits had a significant higher endocytosis rate than ρ1 containing homooligomeric receptors. Mutant constructs lacking binding sites for protein interactions ensured the specificity of our data. Finally, substitution of serine and threonine residues with alanines indicated that GABA(C)R internalization depends on serine/threonine kinases and phosphatases, but not on tyrosine phosphorylation. We conclude that GABA(C)R internalization is reciprocally regulated by PKCζ and PP1 that are anchored to the receptor via ZIP3 or PNUTS respectively.