Hybrid scaffolds of Mg alloy mesh reinforced polymer/extracellular matrix composite for critical‐sized calvarial defect reconstruction

The challenge of developing scaffolds to reconstruct critical‐sized calvarial defects without the addition of high levels of exogenous growth factor remains relevant. Both osteogenic regenerative efficacy and suitable mechanical properties for the temporary scaffold system are of importance. In this study, a Mg alloy mesh reinforced polymer/demineralized bone matrix (DBM) hybrid scaffold was designed where the hybrid scaffold was fabricated by a concurrent electrospinning/electrospraying of poly(lactic‐co‐glycolic acid) (PLGA) polymer and DBM suspended in hyaluronic acid (HA). The Mg alloy mesh significantly increased the flexural strength and modulus of PLGA/DBM hybrid scaffold. In vitro results demonstrated that the Mg alloy mesh reinforced PLGA/DBM hybrid scaffold (Mg‐PLGA@HA&DBM) exhibited a stronger ability to promote the proliferation of bone marrow stem cells (BMSCs) and induce BMSC osteogenic differentiation compared with control scaffolding materials lacking critical components. In vivo osteogenesis studies were performed in a rat critical‐sized calvarial defect model and incorporated a variety of histological stains and immunohistochemical staining of osteocalcin. At 12 weeks, the rat model data showed that the degree of bone repair for the Mg‐PLGA@HA&DBM scaffold was significantly greater than for those scaffolds lacking one or more of the principal components. Although complete defect filling was not achieved, the improved mechanical properties, promotion of BMSC proliferation and induction of BMSC osteogenic differentiation, and improved promotion of bone repair in the rat critical‐sized calvarial defect model make Mg alloy mesh reinforced PLGA/DBM hybrid scaffold an attractive option for the repair of critical‐sized bone defects where the addition of exogenous isolated growth factors is not employed.     

A magnetic ion-imprinted polymer for lead(II) determination: A study on the adsorption of lead(II) by beverages

In this work a variety of beverage samples had been kept in a contaminated area to investigate their lead adsorption. To determine the adsorbed Pb(II), a novel magnetic lead ion-imprinted polymer, grafted onto Fe₃O₄ nanoparticles, was synthesized and used as a selective sorbent for the preconcentration of Pb(II) ions. The sorbent was characterized by different techniques. The synthesized sorbent was applied for highly accurate and selective determination of Pb(II) ions absorbed from polluted air in several beverages and results were compared. To validate the method, three certified reference materials were analyzed by the proposed method and the results showed that pre-concentrating by this sorbent and subsequent determination by flame atomic absorption spectroscopy is an accurate method for lead determination in beverage samples (recoveries higher than 95%). The limits of detection and the relative standard deviations were less than 1.7 μg kg⁻¹ and 4.1%, respectively. The sorption capacity of this new sorbent was 51.8 mg g⁻¹. Finally, this method was used for the determination of Pb(II) ions in polluted beverage samples, and the results revealed that under equal conditions, coffee exhibits more tendency to adsorb Pb(II) ions.     

加强型流动聚合体在窝沟封闭中的疗效评价

目的探讨Beautifil Flow Plus加强型流动聚合体,在窝沟封闭中的临床疗效。方法选择双侧下颌4个乳磨牙均萌出可行窝沟封闭的133例儿童,随机分为玻璃离子水门汀组66例264颗乳磨牙和Beautifil Flow Plus加强型流动聚合体组67例268颗乳磨牙,分别用玻璃离子水门汀和BF行窝沟充填,比较两组封闭后6、12、24、36个月两组封闭剂的保留率及龋齿发生率。结果 6、12个月两组封闭剂的保留率及龋齿发生率差异无显著性(P>0.05);24、36个月Beautifil Flow Plus加强型流动聚合体组封闭剂的保留率明显高于玻璃离子水门汀组,龋齿发生率明显低于玻璃离子水门汀组,差异均有显著性(P<0.05)。结论 Beautifil Flow Plus加强型流动聚合体是合适的窝沟封闭材料,充填窝沟保留率高和龋齿的发生率低。     

海洋来源的可生物降解材料

摘要:近年来,可生物降解材料在生物医学领域的研究取得了突破进展。来源于海洋的可生物降解材料有很好的生物相容性和多样的生物活性,可作为药物的缓控释载体,在组织工程学中可以作为组织替代物和多孔支架,应用十分广泛。本文着重介绍了多糖和蛋白质两大类海洋来源可生物降解材料的物理、化学、生物特性和降解性能,总结了它们在生物医学领域的应用。     

Synthesis and swelling-deswelling kinetics of poly(N-isopropylacrylamide) hydrogels grafted with LCST modulated polymers

Two types of thermo-responsive hydrogels arc synthesized to obtain comb-type grafted gels with different lower critical solution temperatures (LCSTS) between graft chains and cross-linked backbone networks: these are poly(N-isopropylacrylamide) (PIPAAm) cross-linked hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(IPAAm-(-o-DMAAiii)) maintaining a freely mobile end and poly(IPAAm-co-DMAAm) cross-linked hydrogels grafted with PIPAAm chains. The effect of graft chain hydrophilic/hydrophobic balance as well as its mobility on deswelling kinetics of these grafted gels are investigated through the polymer LCST modulation and external temperature changes. The deswelling rate of poly(IPAAm-co-DMAAm)-grafted PIPAAm gel increases with increasing in temperature. This gel shows a discontinuous increase of the deswelling rate when the temperature is applied from below to above the graft chain LCST (37°C). The deswelling rate of PIPAAm-grafted poly(IPAAm-co-DMAAm) gel increases continuously when the temperature is applied from below to above the graft chain LCST (31°C). Due to the strong hydrophilicity of backbone network, the hydrophobic aggregation force weak. In contrast to the graft-type gels, normal-type poly(IPAAm-co-DMAAm) cross-linked gel without graft chains demonstrates the discontinuous decrease for the deswelling rate when the temperature is applied from below to above the polymer LCST (36°C), entrapping water inside the gel due to the formation of an impermeable dense skin layer at the gel surface. These gel deswelling mechanisms are discussed in terms of gel structures.     

Preparation of lysozyme imprinted magnetic nanoparticles via surface graft copolymerization

Molecular imprinting as a facile and promising separation technique has received considerable attention because of their high selectivity for target molecules. In this study, we imprinted lysozyme (Lys) on the surface of core–shell magnetic nanoparticles via surface imprinting. The magnetic supports were functionalized with maleic acid and then coated with imprinted polymer layers. The structure and morphology of the resulting magnetic imprinted nanoparticles were characterized by transmission electron microscopy, scanning electron microscope, dynamic light scatting, vibrating sample magnetometer, and thermogravimetric analysis. Binding experiments were carried out to evaluate the properties of magnetic molecularly imprinted polymers (magnetic MIPs) and magnetic non-molecularly imprinted polymers (magnetic NIPs). The protein adsorption results showed that the magnetic MIPs had significant specific recognition toward the template protein and could be easily separated from solution by an external magnetic field. Moreover, the MIPs exhibited fast kinetics for the rebinding of the target protein due to the thin-imprinted layer and showed good reusability by four adsorption–desorption cycles. Therefore, the surface imprinting approach combined with magnetic nanoparticles provided an easy and fast method for the specific recognition of Lys.     

Fabrication of a live cell-containing multilayered polymer hydrogel membrane with micrometer-scale thickness to evaluate pharmaceutical activity

We propose a spinning-assisted layer-by-layer method for simple fabrication of a multilayered polymer hydrogel membrane that contains living cells. Hydrogel formation occurred based on the spontaneous cross-linking reaction between two polymers in aqueous solution. A water-soluble 2-methacryloyloxyethyl phosphorylcholine polymer bearing phenylboronic acid groups (PMBV) and poly(vinyl alcohol) (PVA) were used as polymers for hydrogel membrane formation. Changing the number of hydrogel membrane layers, polymer concentration, spinning rate, and processing time for diffusion-dependent gelation of PMBV and PVA facilitated the regulation of the multilayered polymer hydrogel membrane thickness and morphology. We concluded that a multilayered polymer hydrogel membrane prepared using 5.0 wt% PMBV and 5.0 wt% PVA at a spinning rate of 2000 rpm was suitable for precise spatial control of cells in single layers. This multilayered polymer hydrogel membrane was used to prepare a single cell-laden layer to minimize barriers to the diffusion of bioactive compounds while preserving the three-dimensional (3-D) context. The pharmaceutical effects of one of the anticancer agents, paclitaxel, on a human cervical cancer line, HeLa cells, were evaluated in vitro, and the usability of this culture model was demonstrated.     

Comparison of medical-grade ultrahigh molecular weight polyethylene microstructure by atomic force microscopy and transmission electron microscopy

Atomic force microscopy is used to image the topography of surfaces of bulk medical-grade ultrahigh molecular weight polyethylene (UHMWPE). Comparison with transmission electron microscopy images demonstrates that the AFM can resolve the plate-like stacks of crystalline lamellae characteristic of UHMWPE without aggressive surface treatment. Surface preparation for the AFM must be carried out by cryomicrotomy at extremely low temperatures to prevent smearing of surface features. Chemically-etched surfaces of UHMWPE require substantially less surface preparation for AFM imaging.     

Solid Polymer Electrolytes from Copolymers Based on Vinyl Dimethyl Phosphonate and Vinylidene Fluoride

Solid polymer electrolytes are prepared by mixing various amounts of lithium bis(trifluoromethanesulfonyl)imide with poly(vinylidene fluoride‐co‐vinyl dimethyl phosphonate) statistical copolymers with different compositions. Such copolymers are obtained by conventional radical copolymerization of vinylidene fluoride (VDF) with vinyl dimethyl phosphonate (VDMP) initiated by peroxides. A morphological study of the obtained solid polymer electrolytes (SPEs) shows that only samples prepared from the copolymer with the lower amount of VDMP (16 mol%) result in the formation of homogeneous electrolytes while aggregates of lithium salts are observed for the other copolymers. The best ionic conductivity values are accordingly observed for the copolymers with the lower VDMP amount and are reaching 5 × 10^?3 mS cm^?1 at 100 °C. The dependence of the ionic conductivity versus temperature suggests that the ionic conductivity is controlled by the motion of polymer segments. Indeed, the ionic conductivity can be increased by adding a small amount of trimethylphosphate plasticizer and can reach 1.9 × 10^?2 mS cm^?1 at 20 °C. Finally, the prepared SPEs exhibit a high electrochemical stability and a good resistance to flame because of the presence of fire‐retardant phosphate groups in their structure.     

MAPLE Deposition of Macromolecules

Macromolecules are poised to feature prominently as components in organic electronics, medical implants, drug delivery systems, and sensors. A common theme for the role polymers will play in all of these is as a thin film. In all applications, it is paramount to have precise control over film thickness, structure, morphology, surfaces roughness, etc. Here, matrix‐assisted pulsed laser evaporation (MAPLE) is reviewed as a route to processing polymer and other soft matter thin films with control over the above‐mentioned parameters. After briefly discussing the experimental setup and current proposed mechanism of film formation via MAPLE, the use of MAPLE to process thin films is highlighted for use in various technologies and applications. Future directions and challenges for MAPLE processing of thin films are also discussed.