Electrically conductive biomaterials that can efficiently deliver electrical signals to cells or improve electrical communication among cells have received considerable attention for potential tissue engineering applications. Conductive hydrogels are desirable particularly for neural applications, as they can provide electrical signals and soft microenvironments that can mimic native nerve tissues. In this study, conductive and soft polypyrrole/alginate (PPy/Alg) hydrogels are developed by chemically polymerizing PPy within ionically cross-linked alginate hydrogel networks. The synthesized hydrogels exhibit a Young's modulus of 20-200 kPa. Electrical conductance of the PPy/Alg hydrogels could be enhanced by more than one order of magnitude compared to that of pristine alginate hydrogels. In vitro studies with human bone marrow-derived mesenchymal stem cells (hMSCs) reveal that cell adhesion and growth are promoted on the PPy/Alg hydrogels. Additionally, the PPy/Alg hydrogels support and greatly enhance the expression of neural differentiation markers (i.e., Tuj1 and MAP2) of hMSCs compared to tissue culture plate controls. Subcutaneous implantation of the hydrogels for eight weeks induces mild inflammatory reactions. These soft and conductive hydrogels will serve as a useful platform to study the effects of electrical and mechanical signals on stem cells and/or neural cells and to develop multifunctional neural tissue engineering scaffolds.

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BackgroundHydrogels that possess hydrophilic and soft characteristics have been widely used in various biomedical applications, such as tissue engineering scaffolds and drug delivery. Conventional hydrogels are not electrically conductive and thus their electrical communication with biological systems is limited.MethodTo create electrically conductive hydrogels, we fabricated composite hydrogels of hyaluronic acid and polypyrrole. In particular, we synthesized and used pyrrole-hyaluronic acid-conjugates and further chemically polymerized polypyrrole with the conjugates for the production of conductive hydrogels that can display suitable mechanical and structural properties.ResultsVarious characterization methods, using a rheometer, a scanning electron microscope, and an electrochemical analyzer, revealed that the PPy/HA hydrogels were soft and conductive with ~ 3 kPa Young’s modulus and ~ 7.3 mS/cm conductivity. Our preliminary in vitro culture studies showed that fibroblasts were well attached and grew on the conductive hydrogels.ConclusionThese new conductive hydrogels will be greatly beneficial in fields of biomaterials in which electrical properties are important such as tissue engineering scaffolds and prosthetic devices.

Electrically conducting biomaterials have gained great attention in various biomedical studies especially to influence cell and tissue responses. In addition, wrinkling can present a unique topography that can modulate cell-material interactions. In this study, we developed a simple method to create wrinkle topographies of conductive polypyrrole (wPPy) on soft polydimethylsiloxane surfaces via a swelling-deswelling process during and after PPy polymerization and by varying the thickness of the PPy top layers. As a result, various features of wPPy in the range of the nano- and microscales were successfully obtained. In vitro cell culture studies with NIH 3T3 fibroblasts and PC12 neuronal cells indicated that the conductive wrinkle topographies promote cell adhesion and neurite outgrowth of PC12 cells. Our studies help to elucidate the design of the surface coating and patterning of conducting polymers, which will enable us to simultaneously provide topographical and electrical signals to improve cell-surface interactions for potential tissue-engineering applications.

Background: The study was to analyze the therapeutic effect and risk factors of in-hospital mortality in patients with acute Stanford type A aortic dissection operated by Sun’s procedure. Methods: From Jan. 2010 to March 2016, 72 patients whose data was fully accessible underwent Sun’s procedure in our hospital due to acute Stanford type A aortic dissection. Patients were divided into the survival group and the death group, and the risk factors for in-hospital mortality were collected and analyzed. Results: All 72 patients were diagnosed as acute Stanford type A aortic dissection by CT angiography in which the ascending aorta, aortic arch and descending aorta were involved; these patients were operated by Sun’s procedure. The operation of proximal aorta included 39 Bentall procedure, one David surgery, and 32 ascending aorta replacement. The in-hospital mortality rate was 19.4% (14 patients). Studies showed the risk factors for the in-hospital mortality included the body mass index, cardiopulmonary bypass time, operation time, intraoperative transfusion of red blood cells and plasma volume, and the total perioperative transfusion of red blood cells, plasma and cryoprecipitate volume. Independent risk factors included the body mass index and cardiopulmonary bypass time. Conclusion: Acute Stanford type A aortic dissection is a severe, complex disease with high in-hospital mortality, though the Sun’s procedure is an effective surgical approach in treating this kind of disease in some center. Body mass index and cardiopulmonary bypass time are independent risk factors for in-hospital mortality.