Improving Biocompatibility of Implantable Metals by Nanoscale Modification of Surfaces: An Overview of Strategies,Fabrication Methods,and Challenges

The human body is an intricate biochemical–mechanical system, with an exceedingly precise hierarchical organization in which all components work together in harmony across a wide range of dimensions. Many fundamental biological processes take place at surfaces and interfaces (e.g., cell–matrix interactions), and these occur on the nanoscale. For this reason, current health‐related research is actively following a biomimetic approach in learning how to create new biocompatible materials with nanostructured features. The ultimate aim is to reproduce and enhance the natural nanoscale elements present in the human body and to thereby develop new materials with improved biological activities. Progress in this area requires a multidisciplinary effort at the interface of biology, physics, and chemistry. In this Review, the major techniques that have been adopted to yield novel nanostructured versions of familiar biomaterials, focusing particularly on metals, are presented and the way in which nanometric surface cues can beneficially guide biological processes, exerting influence on cellular behavior, is illustrated. Frontispiece adapted from Reference 94 .

     

Lactobacilli isolated from the Armenian fermented milk product matsoun: Growth properties,antibacterial and proteolytic activity and their dependence on pH

Growth, antibacterial and proteolytic activities of two new lactobacilli strains isolated from matsoun (Armenian traditional dairy product) and their pH dependence were studied. The results demonstrated the antibacterial activity of lactobacilli against Gram‐positive and Gram‐negative test strains. This activity was stable when pH of cell culture medium was adjusted to the value of 6.5. At pH 8, the antibacterial activity of only one strain was stable. Both strains were able to hydrolyse casein in pH range of 5.5–8 with maximal activity at pH 5.5. Controlled pH conditions were suitable for biomass yield, while noncontrolled pH was better for expression of antibacterial activity.     

Short range wake potentials of FLASH resistive tapered collimator and European XFEL undulator intersection

The longitudinally dispersion free hybrid TE/TM numerical scheme is applied for the calculation of short range longitudinal and transverse wake potentials for the FLASH free electron laser facility resistive tapered collimator and European XFEL undulator intersection. All the investigated structures have cylindrical symmetry. The contributions of transitive resistive wakes in loss and kick factors are evaluated. The results are confirmed by the comparison with analytical approximations and other numerical codes.     

Site Selective Synthesis of Pentaarylpyridines via Multiple Suzuki–Miyaura Cross‐Coupling Reactions

Pentaarylpyridines were conveniently prepared in one step by pentafold Suzuki–Miyaura reactions of pentachloropyridine. Moreover, site selective reactions were performed, leading to various substituted arylpyridines. Pentaarylpyridines were studied in detail by means of DFT calculations and by optical spectroscopy.

     

Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700°C. This behavior is likely related to a transition in the growth mode from a predominantly “base growth” to that of a “tip growth.” For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO₂ layer.