Rheological properties of teak wood flour reinforced HDPE and maize starch composites

Teak wood flour reinforced high density polyethylene and maize starch composites were prepared by using maleic anhydride grafted polyethylene as a compatibilizer. The mechanical properties (tensile and flexural) of all the composites increased after addition of 10%–40% teak wood flour into HDPE matrix. The complex viscosity (η*) was higher for all the composites at the low frequency, but decreased with increasing frequencies indicating a shear thinning behavior of the composites. The storage modulus and loss modulus increased for the composites compared to the HDPE at low frequencies. Damping factor peak of HDPE and composites showed high below 1 Hz, but the peak start decreasing with increasing above 1 Hz. The relaxation behavior of HDPE and the composites after incorporating teak wood flour, maize starch, and compatibilizer was obtained by Han plot. Biodegradability was enhanced with the incorporation of teak wood flour, maize starch into the composites. Appreciable water uptake and the thickness swelling for the composites indicating it's potential for interior, automobile and packaging applications.     

pH and magnetic field responsive protein-inorganic nanohybrid conjugated with biotin: A biocompatible carrier system targeting lung cancer cells

Multi-stimuli responsive carrier systems, specifically targeting tumor cells are of high significance to improve the efficacy of cancer chemotherapy. In the present study, we have developed, characterized, and biologically evaluated magnetic casein-calcium ferrite hybrid biopolymeric carrier conjugated with biotin for targeted delivery of cinnamaldehyde to lung carcinoma. The dual stimuli-responsive carrier was successfully synthesized with small size, good stability, and high drug encapsulation efficiency. Natural drug cinnamaldehyde was encapsulated in the hybrid carrier, on which biotin was conjugated to facilitate selective cellular uptake. The prepared drug-carrier system exhibited pH-responsive drug release behavior with a higher release rate under acidic conditions, which can be effectively applied in targeted cancer chemotherapy. The superparamagnetic nature of calcium ferrite enabled magnetically-modulated drug delivery with faster drug release, reaching 85.5% within 4 h, in response to magnetic field stimulus. Kinetic modeling of drug release projected the diffusion-controlled release mechanism. Cell viability assay performed on L929 fibroblast and A549 lung cancer cells verified the biocompatibility and cytotoxicity of the developed formulation, respectively. The nanohybrid carrier significantly increased the anticancer potential of cinnamaldehyde with an 18-fold reduction in the IC₅₀ value, signifying the biotin-functionalized protein-inorganic nanohybrid as an efficient multifunctional platform for targeted drug delivery.     

A cationic alternating copolymer composed of ornithine and glycine with an ordered sequence for enhanced bacterial activity

The chains and segments of unordered cationic polypeptides are complex and may produce unexpected biological activities. Herein, the Ugi's 4CC reaction is adopted to synthesize a cationic alternating copolymer comprising ornithine and glycine (poly(Orn-alter-Gly)) with an ordered sequence for enhanced bacterial resistance. In this technique, potassium isocyanate, 4-(N-carbobenzyloxyamino)-1-butyraldehyde and 1-(4-Methoxyphenyl)ethylamine react to produce MPE-substituted poly(Orn-alter-Gly) in one step without using a catalyst and then poly(Orn-alter-Gly) is obtained by removing the N-(1-p-methoxyphenethyl) (MPE) group. ¹H NMR, Fourier transform infrared spectroscopy, and automatic amino acid analysis confirm that ornithine and glycine are linked alternately in the poly(Orn-alter-Gly) chains. Both MPE-substituted poly(Orn-alter-Gly) and poly(Orn-alter-Gly) have excellent antibacterial activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa as well as excellent biocompatibility. The synthesis strategy and materials provide new information on how to obtain ordered sequence cationic polypeptides.     

Hemocompatibility of polymers for use in vascular endoluminal implants

Implanted polymers for cardiovascular applications may function as structural supports, barriers, or provide a means for local drug delivery. Several thermoplastic biodegradable drug delivery polymers are potential candidates for blood-contacting implant applications. For intravascular applications specifically, a criterion for material selection is the intrinsic hemocompatibility of the baseline polymer. As an initial screening approach for selection of polymers for in vivo use, thin films of polyesters: poly(ɛ-caprolactone) (PCL), poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA); polyanhydrides: poly(fatty acid dimer-co-sebacic acid) (PFAD:SA) and poly(biscarboxyphenoxypropane-co-sebacic acid) (PCPP:SA); and poly(ethylene glycol) (PEG)-ylated polyesters: PLA:PEG, PCL:PEG and PCL:PLA:PEG polymers were spin-cast on glass cover slips and placed in an in vitro flow system exposing them at a controlled shear to overflowing human whole blood. Platelet adherence, aggregate formation, and thrombus formation, as well as leukocyte adherence were assessed following 5 min of flow. At 5 min of flow the rank order of materials, in terms of least to most thrombogenic was: PCL < PFAD:SA < PCPP:SA < PLGA < PLA. All PEGylated materials, in general, had less thrombus formation than baseline unmodified materials.     

Biocompatibility Study of a New Dental Cement Based on Hydroxyapatite and Calcium Silicates: Focus on Liver,Kidney, and Spleen Tissue Effects

The effects of a new material based on hydroxyapatite and calcium silicates, named ALBO-MPCA, were investigated on the liver, kidney and spleen. The material was administrated orally for 120 days in an in vivo model in Wistar rats, and untreated animals served as a control. Hematological and biochemical blood parameters were analyzed. Qualitative histological analysis of tissues, change in mitotic activity of cells, and histological characteristics was conducted, as well as quantitative stereological analysis of parenchymal cells, blood sinusoids, and connective tissues. Additionally, the protein expressions of Ki67 and CD68 markers were evaluated. Histological analysis revealed no pathological changes after the tested period. It showed the preservation of the architecture of blood sinusoids and epithelial cells and the presence of mitosis. Additionally, the significantly increased number of the Ki67 in the presence of ALBO-MPCA confirmed the proliferative effect of the material noticed by stereological analysis, while immunoreactive CD68 positive cells did not differ between groups. The study showed non-toxicity of the tested material based on the effects on the hematological, biochemical, and observed histological parameters; in addition, it showed evidence of its biocompatibility. These results could be the basis for further steps toward the application of tested materials in endodontics.     

生物医用金属表面水滑石涂层的研究进展

随着我国人口老龄化和生活水平提高,人们对性能优异的生物医疗器械和植入材料需求剧增.目前,常见医用植入金属或合金的一些性能,如耐蚀性和生物相容性等,往往不能完全满足临床要求,因此有必要对医用金属材料进行表面改性处理.首先,结合水滑石(LDHs)的特点、性质及近年来的发展情况,综述了常见医用载药LDHs进展,提出了载药LDHs在缓释控释、靶向运输和癌症治疗等方面的应用前景,含有元素Mg、Zn的LDHs具有特殊作用.然后,重点总结常见医用可降解金属(镁、锌合金)和不可降解金属(钛合金)表面单一和复合LDHs涂层的制备方法,介绍不同种类LDHs涂层及其优点,着重分析当前不同医用金属表面LDHs涂层所存在的不足和潜在的应用.另外,金属表面LDHs复合涂层多方面性能均强于单一涂层,致密的LDHs涂层通常作为上层涂层可以起到封孔作用.最后,展望了含Zn、Mg元素LDHs在生物医用方向的应用前景,并分析了含Al、Li元素LDHs在生物医用方向发展需要注意之处和受阻的可能原因,为医用金属表面LDHs涂层的发展提供参考.     

Microstructures and mechanical properties of biocompatible Ti-42 wt.%Nb P/M alloy

Ti-42 wt. %Nb powder was prepared by high-energy mechanical milling (HEMM). The particle size distribution (PSD) of the as-milled powder has been investigated using a particle size distribution analyzer. The morphology and microstructure of the as-milled powder have been investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), and differential thermal analysis (DTA). Also, the corrosion property and biocompatibility of sintered specimens comprising mixed and milled powders have been investigated. The milled powders were sintered using pulse current activated sintering (PCAS). PCAS was employed in order to provide more refined grain size and full density to Ti-42 %Nb alloy on the basis of short sintering time with pressure. The density of the sintered Ti-42 %Nb specimen fabricated using the milled powder increased with increased milling time due to high free surface area and defect density. The density of the sintered Ti-42 %Nb specimen fabricated using as-mixed powder increased with increased sintering temperature up to 950 °C. The microstructure of the sintered Ti-42 %Nb specimen fabricated using 4h-milled powder was composed of Nb-rich and Nb-poor phases that are more refined and homogeneously distributed. The mechanical properties and biocompatibility of the sintered Ti-42 %Nb specimen fabricated using milled powder were superior to those of a commercial, Ti-6wt.%Al-4wt.%V alloy.     

织构化表面改性及其在生物材料上的应用

表面织构化(Surface texturing)改性是指根据材料属性选择合适的加工手段,在相对运动的摩擦副表面引入具备特定形状、尺寸、分布和排列的微观结构阵列,从而实现摩擦副摩擦学性能的调控。随着生物材料的迅速发展,生物界面的摩擦学问题是制约其服役安全与寿命的关键因素。表面改性(如合理的表面织构化设计)因强大的润滑优化功能,由此受到科研工作者的广泛关注。在生物材料服役寿命需求日益增加的背景下,首先分析和总结了典型生物材料产品——人工关节在人体服役过程中的失效原因,并将其分为了摩擦学和生物学问题,由此提出了通过表面织构化技术改进人工关节材料的耐磨性和增强其生物相容性,最终达到实现长寿命人工关节服役的目的。详细地论述了近年来表面织构在生物材料上的研究进展,分析了表面织构化参数,如形状、尺寸及排布等对摩擦学性能的影响,考察了不同织构对摩擦副在不同运动工况下承载力及耐磨性的影响,阐述了表面织构的减摩耐磨机理。最后讨论了表面织构对细胞接触引导生长的调控,如对细胞的粘附状态、形态、增殖和分化能力的影响,尽管利于细胞生长的尺寸小于润滑优化的尺寸,但通过多层次或复合设计可望实现生物相容性与摩擦学性能改善相兼具的目标。最后在现有人工关节材料表面改性的研究基础上,对延长人工关节服役寿命的研究方向、发展趋势和应用领域进行了展望。     

生物医用TiNi形状记忆合金表面改性研究进展

本文介绍了近年来TiNi形状记忆合金表面改性方面的研究发展状况,重点评述了离子注入、表面涂层和氧化法的改性结果,并提出了其中存在的问题和未来发展方向。     

激光修饰在制备生物活性表面中的应用

回顾了金属基体表面羟基磷灰石（HA）或合金层的激光重熔（LSRM）、金属表面激光熔凝（LSM）以及脉冲激光沉积钙磷层（PLD）等激光表面处理技术,利用LSRM、LSM、PLD可以明显改善基体表面的耐蚀性和生物相容性。