Facile synthesis of extremely biocompatible double‐network hydrogels based on chitosan and poly(vinyl alcohol) with enhanced mechanical properties

An easy and ecofriendly method for designing double‐network (DN) hydrogels based on chitosan and poly(vinyl alcohol) (PVA) with high mechanical performance is described. When covalent bonds in the networks are used as crosslinking agents in the achievement of a higher mechanical strength, the irreversible deformation of these hydrogels after a large force is applied is still one of the most important obstacles. To overcome this problem, we used physical crosslinking for both networks. The mechanical strength, surface morphology, and cytotoxicity of the films were studied by tensile testing, scanning electron microscopy analysis, and an MTT assay. The synthesized chitosan–PVA DN hydrogels showed a large improvement in the tensile strength to 11.52 MPa with an elongation of 265.6%. The surface morphologies of the films demonstrated the effective interactions between the two networks and a suitable porosity. Also, because of the use of a natural polymer and honey as a plasticizer, the cell culture indicated that the synthesized DN hydrogels had good biocompatibility (with 327.49 ± 11.22% viability) and could be used as capable biomaterials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45752.     

An innovative α‐calcium sulfate hemihydrate bioceramic as a potential bone graft substitute

The microstructural, in vitro and in vivo properties of the microwave‐synthesized samples were investigated using the optical microscope, scanning electron microscope, X‐ray diffraction, differential scanning calorimeter, contact angle goniometer, cell cytotoxicity assay, and chick chorioallantoic membrane (CAM) model in the study. When the calcium sulfate dihydrate (CSD) precursor underwent microwave irradiation treatment at temperatures between 100°C and 160°C, the crystal morphologies and crystalline structures were transformed from (tablet‐like CSD (monoclinic)) → (tablet‐like CSD (monoclinic) + long column α‐calcium sulfate hemihydrate (α‐CSH, hexagonal)) → (long column CSD (monoclinic) + short column α‐CSH (hexagonal)) → (uniform short column α‐CSH (hexagonal)). The high‐purity α‐CSH with uniform short column crystals around 10 μm in length can be synthesized at 160°C for 10 minutes and exhibits a higher hydrophilic feature in blood. Moreover, the cell cytotoxicity assay indicated that the microwave‐synthesized samples possessed well biocompatibility. In vivo results also demonstrated that the microwave‐synthesized α‐CSH not only induces angiogenesis formation but also facilitates osteogenesis. Therefore, the microwave‐synthesized α‐CSH is a promising bone graft substitute that can be applied in dental and orthopedic fields.     

Tough and Self‐Recoverable Thin Hydrogel Membranes for Biological Applications

Tough and self‐recoverable hydrogel membranes with micrometer‐scale thickness are promising for biomedical applications, which, however, rarely be realized due to the intrinsic brittleness of hydrogels. In this work, for the first time, by combing noncovalent DN strategy and spin‐coating method, we successfully fabricated thin (thickness: 5–100 µm), yet tough (work of extension at fracture: 10⁵–10⁷ J m^?3) and 100% self‐recoverable hydrogel membranes with high water content (62–97 wt%) in large size (≈100 cm²). Amphiphilic triblock copolymers, which form physical gels by self‐assembly, were used for the first network. Linear polymers that physically associate with the hydrophilic midblocks of the first network, were chosen for the second network. The inter‐network associations serve as reversible sacrificial bonds that impart toughness and self‐recovery properties on the hydrogel membranes. The excellent mechanical properties of these obtained tough and thin gel membranes are comparable, or even superior to many biological membranes. The in vitro and in vivo tests show that these hydrogel membranes are biocompatible, and postoperative nonadhesive to neighboring organs. The excellent mechanical and biocompatible properties make these thin hydrogel membranes potentially suitable for use as biological or postoperative antiadhesive membranes.     

Improving collagen extraction through an alternative strategy based on succinic anhydride pretreatment to retain collagen's triple‐helix structure

The improvement of the extraction yield of collagen while retaining its triple‐helix structure continues to represent a significant challenge for the high‐value utilization of collagen. In this study, pigskin was pretreated by succinic anhydride via the chemical linking of additional carboxylic groups to epsilon amino groups with a conversion degree of 90.2% to obtain pretreatment acid‐pepsin‐solubilized collagen (PAPC). The pretreatment by succinic anhydride increased the tropocollagen distance from 1.39 to 1.42 nm. This permitted acid and pepsin to more easily enter into the fiber clearance and, thus, improved the collagen extraction yield by 9.6%. Furthermore, X‐ray diffraction, Fourier transform infrared spectroscopy, circular dichroism, ultrasensitive differential scanning calorimetry, and atomic force microscopy analysis demonstrated that the triple‐helix conformation of PAPC was well‐maintained. The equilibrium surface tension and isoelectric point of PAPC were 57.48 mN/m and 4.01, respectively; this suggested that the PAPC had surface activity and better solubility in a neutral pH solution. The novelty of PAPC lay in its facilitating fibroblast proliferation, and no extra cytotoxicity was introduced into the collagen after pretreatment. According to these results, our study revealed that succinic anhydride pretreatment as an alternative strategy retained the triple‐helix structure of collagen and improved its extraction ratio; this might be a feasible, yet promising paradigm for the high‐value utilization of collagen. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45424.     

Incorporation of chloramphenicol and captopril into poly(GL)‐b‐poly(GL‐co‐TMC‐co‐CL)‐b‐poly(GL) monofilar surgical sutures

Incorporation of chloramphenicol and captopril into coated and uncoated monofilament sutures was evaluated, as well as the derived bactericide and wound healing effects. To this end, a commercially available suture and an amorphous random copolymer constituted by trimethylene carbonate and lactide units were considered. The suture had a segmented architecture based on polyglycolide hard blocks and a soft block constituted by glycolide, trimethylene carbonate and ε‐caprolactone units. Chloramphenicol was better loaded when the coating copolymer was employed due to its protective effect whereas captopril showed an opposite behavior due to partial solubilization during immersion in the coating bath. Interestingly, the release behavior was very different for the two studied drugs since a significant retention of chloramphenicol was always detected, suggesting the establishment of interactions between drug and copolymers. On the other hand, delivery of captopril showed a typical dose dependent behavior. A low in vitro toxicity of the two drugs was determined considering both epithelial‐like and fibroblast‐like cells. Bactericide effect of chloramphenicol against Gram‐negative and Gram‐positive bacteria was demonstrated at a dose that was non‐toxic for all assayed cells. An accelerating wound healing effect of captopril was also demonstrated for early events. In this case, the use of a coating copolymer was fundamental to avoid cytotoxic effects on highly loaded sutures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44762.     

Buildup of hyperbranched polymer/alginate multilayers and their influence on protein adsorption and platelet adhesion

A hyperbranched poly(methylene bisacrylamide–aminoethyl piperazine) (HPMA) and lactobionic acid modified hyperbranched poly(methylene bisacrylamide–aminoethyl piperazine) (LA–HPMA), namely, galactosylated HPMA, were assembled with alginate through the application of the layer‐by‐layer technique to fabricate polyelectrolyte multilayer (PEM) films. We monitored the assembly process to reveal the stepwise mass increase with a quartz crystal microbalance with the dissipation technique and by the reversal of the ζ potential. The thickness of PEMs assembled in solutions with different pHs was measured by spectroscopic ellipsometry; it showed a general decreasing tendency along with the pH increase. Postincubation in a buffer solution revealed that the multilayers possessed good stability with a thickness decrease from 5 to 15%. The PEMs showed a limited protein adsorption. Serum, bovine serum albumin, and fibrinogen were adsorbed onto the multilayers with a density within hundreds of nanograms per square centimeter to 1 μg/cm² and showed a relatively smaller adsorption on the multilayers assembled at pH 9. The PEMs assembled with LA–HPMA showed the lowest adhesion and activation of platelets, regardless of the outmost layer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44769.     

Physical,morphological, and biological studies on PLA/nHA composite nanofibrous webs containing Equisetum arvense herbal extract for bone tissue engineering

A series of herbal extract incorporated into poly(lactic acid) (PLA) composite nanofibrous scaffolds were successfully prepared by using electrospinning technique. Equisetum arvense extract (EE) and nanohydroxyapatite (nHA) in different quantities were loaded into PLA solution to fabricate composite nanofibrous webs under various electrospinning conditions. Uniform nanofibers were obtained with an average diameter of 157 ± 47 nm in the case of those containing the herbal extract. Characterization of the webs was carried out by means of Fourier transform infrared (FTIR) spectroscopy, field emission‐scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDX), and differential scanning calorimetry (DSC) techniques. Mechanical properties, porosity, and contact angle of the prepared webs were also determined. Releasing behavior was investigated in phosphate buffer solution (pH 7.2) medium. Moreover, cell studies and osteogenic capacity were assessed in vitro using human adipose tissue‐derived mesenchymal stem cell (AT‐MSC). Evaluations of cell attachment, spreading, and proliferation of AT‐MSC were done by SEM observation and thiazolyl blue (MTT) assay. Osteogenic differentiation capability of AT‐MSC on the nanofibrous webs was analyzed by alkaline phosphatase activity and calcium content assay. It was found that with the addition of nHA and EE to PLA nanofibrous webs, their surface hydrophobicity was reduced while the tensile strength and Young's modulus were increased satisfactorily. Regarding the samples containing EE and nHA, cellular adhesion was observed with flattened normal morphology. Osteogenic differentiation of AT‐MSC on PLA/nHA/EE webs showed the highest mineralization capacity after 3 weeks which, was about 1.8 and 3 times higher than that of PLA/nHA and tissue culture polystyrene as control, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45343.     

Quiescent crystallization of poly(lactic acid) studied by optical microscopy and light‐scattering techniques

The crystallization behavior of poly(lactic acid) (PLA) has been studied extensively, and this has resulted in different reported values for the nucleation densities (Ns) and crystal growth rates (Gs) for similar grades. These inconsistencies may be magnified when they are used in subsequent modeling studies. Therefore, the quiescent crystallization behaviors of three PLA grades were studied with polarized optical microscopy and small‐angle light‐scattering experiments. The Gs and Ns were determined at several isothermal crystallization temperatures with a device that provided near‐instantaneous cooling to the isothermal crystallization temperature. Two growth rate regimes, which were attributed to α and α′ crystallization with a transition around 120 °C, were observed. Avrami analysis revealed that the poly(l ‐lactic acid) homopolymer crystal growth was three‐dimensional and was unaffected by the presence of stereocomplex PLA. The PLA copolymer crystals had a transition from an initial sheaflike conformation to three‐dimensional growth. Furthermore, the lamellar twisting of the homopolymer was observed at the isothermal crystallization temperature around 144 °C. These findings can be used for future modeling studies to predict material behavior in various industrial processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44566.     

Preparation,Characterization, and Surface Functionality of Polyester Bioplastic-based Green Composites Containing Powdered Curcumin Products

The structural and thermal properties, antibacterial activity, and biocompatibility of composite materials containing polylactide and curcumin powder were evaluated. Glycidyl methacrylate-grafted polylactide and curcumin powder were used to enhance the desired characteristics of these composites. The water resistance of glycidyl methacrylate-grafted polylactide/curcumin powder composites was greater than that of the polylactide/curcumin powder composites. A biocompatibility evaluation with tail skin fibroblasts indicated that both materials were nontoxic for biomedical material applications. Moreover, curcumin powder enhanced the Escherichia coli(BCRC10239) andStaphylococcus aureus (BCRC107801) antibacterial activities of the membranes. Membranes of glycidyl methacrylate-grafted polylactide- or polylactide-containing curcumin powder had better antibacterial activity.     

海藻酸钙/聚精氨酸微胶囊的制备及其生物相容性

以海藻酸盐、 聚精氨酸为壁材, 采用高压静电法制备了球形度好、 表面光洁、 粒径均匀的新型药物载体——海藻酸钙/聚精氨酸微胶囊。参照医疗器械生物学评价标准, 对其生物相容性进行了研究。细胞毒性试验结果显示, 当海藻酸钙/聚精氨酸微胶囊的含量为0.1、 0.5、 1.0 mg/mL时, 微胶囊对L929细胞生长无明显抑制作用, 海藻酸钙/聚精氨酸微胶囊浸提产物在10.0 mg/mL时仍无细胞毒性作用。海藻酸钙/聚精氨酸微胶囊不引起急性全身毒性反应, 不引起溶血反应。通过本组试验可见, 采用高压静电法制备的药物载体——海藻酸钙/聚精氨酸微胶囊具有较好的生物相容性, 具有开发和应用价值。