Fabrication of biodegradable polyurethane electrospun webs of fibers modified with biocompatible graphene oxide nanofiller

A successful optimization of the electrospinning parameters for obtainment of biodegradable polyester urethane (DP) webs of fibers, neat and graphene oxide (GO) modified, was performed. The effect of the processing parameters (distance between the needle tip and the collector, applied voltage, and flowing rate), solution type and polymer concentration, on the fiber-forming process and the obtained fibers’ morphology was examined. The best homogeneity of the fibers was achieved for 12 wt% DP dissolved in 80:20 wt% mixture of chloroform and ethanol, applying similar processing parameters for the neat and modified samples (0.5 ml/h pumping rate, 15 kV applied voltage, and 150 mm distance to the collector, for the neat sample, and 0.4 ml/h, 18 kV, and 110 mm, for the GO modified samples). The main novelty of this work is the modification of DP with low quantities (0.5, 1.0 and 2.0 wt%) of GO – the “next generation” nanomaterial for stem cell control. The morphological characterization revealed a fibrous microstructure consisting of randomly oriented fibers with a diameters ranging from hundreds nanometers to couple micrometers, representing a feasible imitation of the structure of extracellular matrix (ECM). The XRD studies showed high dispersion of GO in DP matrix and even exfoliation for the sample that contains 2 wt% GO. Raman studies neatly complemented the highest filler/matrix interactions and the superior levels of dispersion for this sample. TGA was used to analyze the thermo-oxidative degradation and also to determine the actual content of GO present in the samples.

Internal valvuloplasty combined with sleeve wrapping in the treatment of severe deep venous incompetence: A case report

Background The main cause of severe chronic venous insufficiency is deep venous incompetence. Deep venous reconstructive surgeries are reserved for cases that do not show a good response to conservative therapies. Method We present the case of a 68-year-old man presenting with swelling, pain, and pigmentation in his left lower limb for 14 years and ulcers for 10 years. Descending venography identified a Kistner’s grade IV reflux in the deep vein of the left lower limb. Internal valvuloplasty was performed following Kistner’s method. Meanwhile, external wrapping with a 1-cm-wide polyester-urethane vascular patch was performed to strengthen the vein wall in the venospasm condition. Results Symptoms were immediately relieved postoperatively. Refractory ulcers healed five months after the procedure. At the six-month follow-up, color duplex ultrasound of the deep vein of the left lower limb showed no reflux in the proximal segment of the femoral vein. Conclusion Internal valvuloplasty combined with sleeve wrapping is feasible in the treatment of severe deep venous incompetence with good short-term results.

Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials

For soft robotics and programmable metamaterials, novel approaches are required enabling the design of highly integrated thermoresponsive actuating systems. In the concept presented here, the necessary functional component was obtained by polymer syntheses. First, poly(1,10-decylene adipate) diol (PDA) with a number average molecular weight Mn of 3290 g·mol−1 was synthesized from 1,10-decanediol and adipic acid. Afterward, the PDA was brought to reaction with 4,4′-diphenylmethane diisocyanate and 1,4-butanediol. The resulting polyester urethane (PEU) was processed to the filament, and samples were additively manufactured by fused-filament fabrication. After thermomechanical treatment, the PEU reliably actuated under stress-free conditions by expanding on cooling and shrinking on heating with a maximum thermoreversible strain of 16.1%. Actuation stabilized at 12.2%, as verified in a measurement comprising 100 heating-cooling cycles. By adding an actuator element to a gripper system, a hen’s egg could be picked up, safely transported and deposited. Finally, one actuator element each was built into two types of unit cells for programmable materials, thus enabling the design of temperature-dependent behavior. The approaches are expected to open up new opportunities, e.g., in the fields of soft robotics and shape morphing.