Performance Of Biomedical Devices Research Articles

Diamond-like Carbon Coatings in the Biomedical Field: Properties, Applications and Future Development

Repairment and replacement of organs and tissues are part of the history of struggle against human diseases, in addition to the research and development (R&D) of drugs. Acquisition and processing of specific substances and physiological signals are very important to understand the effects of pathology and treatment. These depend on the available biomedical materials. The family of diamond-like carbon coatings (DLCs) has been extensively applied in many industrial fields. DLCs have also been demonstrated to be biocompatible, both in vivo and in vitro. In many cases, the performance of biomedical devices can be effectively enhanced by coating them with DLCs, such as vascular stents, prosthetic heart valves and surgical instruments. However, the feasibility of the application of DLC in biomedicine remains under discussion. This review introduces the current state of research and application of DLCs in biomedical devices, their potential application in biosensors and urgent problems to be solved. It will be useful to build a bridge between DLC R&D workers and biomedical workers in order to develop high-performance DLC films/coatings, promote their practical use and develop their potential applications in the biomedical field.

Improved processability and performance of biomedical devices with poly(lactic acid)/poly(ethylene glycol) blends

ABSTRACTTo improve the processability of micropolymer‐based devices used for biomedical applications, poly(lactic acid) (PLA) was melt‐blended with poly(ethylene glycol)s (PEGs) of different molecular weights (MWs; weight‐average MWs = 200, 800, 2000, and 4000; these PEGS are referred to as PEG200, PEG800, PEG2000, and PEG4000, respectively, in this article). The thermal properties, mechanical properties, and rheological properties of the PLA and the PLA–PEG blends were investigated. The tensile samples’ morphologies showed that the low‐MW PEGs filled molds well. The rheological properties confirmed that the low‐MW PEGs decreased the complex viscosity, and improved the processability. With decreasing PEG MW, the PLA glass‐transition temperature decreased. The nanoindenter data show that the addition of PEG decreased the modulus and hardness of PLA. The morphologies of the tensile samples showed that with increasing PEG MW, the thicknesses of the core layers increased gradually. The elongation at break was improved by approximately 247% with the addition of PEG200. Such methods can produce easily processed biological materials for producing biomedical products. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45194.

Thin Film Elastic Modulus of Degradable Tyrosine-Derived Polycarbonate Biomaterials and Their Blends

The integrity, function, and performance of biomedical devices having thin polymeric coatings are critically dependent on the mechanical properties of the film, including the elastic modulus. In this report, the elastic moduli of several tyrosine-derived polycarbonate thin films, specifically desaminotyrosyl ethyl tyrosine polycarbonates p(DTE carbonate), an iodinated derivative p(I(2)-DTE carbonate), and several discrete blends are measured using a method based on surface wrinkling. The data shows that the elastic modulus does not vary significantly with the blend composition as the weight percentage of p(I(2)-DTE carbonate) increases for films of uniform thickness in the range of 67 to 200 nm. As a function of film thickness, the observed elastic moduli of p(DTE carbonate), p(I(2)-DTE carbonate) and their 50:50 by mass blend show little variation over the range 30 to 200 nm.

Quantitative Analysis of Protein Adsorption via Atomic Force Microscopy and Surface Plasmon Resonance

Surface properties have a significant influence on the performance of biomedical devices. The influence of surface chemistry on the amount and distribution of adsorbed proteins has been evaluated by a combination of atomic force microscopy (AFM) and surface plasmon resonance (SPR). Adsorption of albumin, fibrinogen, and fibronectin was analyzed under static and dynamic conditions, employing self-assembled monolayers (SAMs) as model surfaces. AFM was performed in tapping mode with antibody-modified tips. Phase-contrast images showed protein distribution on SAMs and phase-shift entity provided information on protein conformation. SPR analysis revealed substrate-specific dynamics in each system investigated. When multi-protein solutions and diluted human plasma interacted with SAMs, SPR data suggested that surface chemistry governs the equilibrium composition of the protein layer.

Evaluation of the interactions between collagen and the surface of a bioactive glass during in vitro test

Interactions between biomaterials and the body environment usually determine the lifetime and performance of biomedical devices used as implants. Among a variety of different types of interactions that occur whenever biomaterials are implanted into the body, adsorption of biomacromolcules onto the surface of biomaterials can guide other relevant processes such as cell attachment, cell differentiation, cell proliferation, tissue growth and biomaterials degradation. In this work, fundamental mechanisms associated with the interactions between collagen and the surface of biomaterials were studied by using Atomic Force Microscopy (AFM). The ultimate goal of this work is to isolate and simulate phenomena occurring at the molecular level, when biological entities are brought in contact with biomaterials. These results can then be used to design and test new biomedical devices. This manuscript reports the evaluation of interactions between collagen and the surface of bioactive glasses. These bioactive glasses are known to bond to soft and hard tissues through the formation of a hydroxy-carbonate-apatite layer. Collagen was grafted onto AFM cantilevers. AFM force-displacement curves were obtained using these modified tips against the surface of a bioactive glass at different stages of an in vitro test performed in a simulated body fluid. The results showed that the structure of the bioactive glass surface affects the adsorption of collagen on the biomaterial. The magnitude of the adhesion force measured is highly dependent on the deposition of a hydroxyl-carbonate-apatite at the surface of the glass.

Enzymatically-tailored pectins differentially influence the morphology, adhesion, cell cycle progression and survival of fibroblasts

Improved biocompatibility and performance of biomedical devices can be achieved through the incorporation of bioactive molecules on device surfaces. Five structurally distinct pectic polysaccharides (modified hairy regions (MHRs)) were obtained by enzymatic liquefaction of apple (MHR-B, MHR-A and MHR-α), carrot (MHR-C) and potato (MHR-P) cells. Polystyrene (PS) Petri dishes, aminated by a plasma deposition process, were surface modified by the covalent linking of the MHRs. Results clearly demonstrate that MHR-B induces cell adhesion, proliferation and survival, in contrast to the other MHRs. Moreover, MHR-α causes cells to aggregate, decrease proliferation and enter into apoptosis. Cells cultured in standard conditions with 1% soluble MHR-B or MHR-α show the opposite behaviour to the one observed on MHR-B and -α-grafted PS. Fibronectin was similarly adsorbed onto MHR-B and tissue culture polystyrene (TCPS) control, but poorly on MHR-α. The Fn cell binding site (RGD sequence) was more accessible on MHR-B than on TCPS control, but poorly on MHR-α. The disintegrin echistatin inhibited fibroblast adhesion and spreading on MHR-B-grafted PS, which suggests that MHRs control fibroblast behaviour via serum-adhesive proteins. This study provides a basis for the design of intelligently-tailored biomaterial coatings able to induce specific cell functions.

Biomedical coatings by the covalent immobilization of polysaccharides onto gas-plasma-activated polymer surfaces

As the surface properties of polymeric biomaterials play an important role in the performance of biomedical devices, highly hydrophilic, ultrathin coatings were applied onto hydrophobic, perfluorinated and organosilicon polymers by the covalent immobilization of polysaccharides using a reductive amination reaction. Gas plasma (r.f. glow discharge) methods were employed to equip the surfaces of these normally unreactive polymeric substrates with chemical groups capable of reacting with polysaccharides in aqueous solution. In one variant, ammonia plasmas were used to introduce into the polymer surfaces a submonolayer of amine groups. Alternatively, an n-heptylamine process vapour was used to deposit a thin plasma polymer film that possessed surface amine groups. The polysaccharides were activated for covalent immobilization by periodate oxidation, which produced hemiacetal structures, as revealed by NMR and XPS. The hemiacetal structures in the polysaccharide chains were reacted with the surface amine groups on the polymers. The resulting Schiff base linkages were stabilized by reduction to secondary amine linkages using sodium cyanoborohydride. Detailed surface analysis is important for verification that the intended chemistries have indeed been achieved in such multilayer coating schemes. X-ray photoelectron spectroscopy provided a thickness estimate of 1 ± 0.3 nm for the polysaccharide coatings in the dehydrated state. Copyright © 2000 John Wiley & Sons, Ltd.