Radionuclides-hyaluronan-conjugate thromboresistant coatings to prevent in-stent restenosis

Development of a New Ultra-High-Precision Magnetic Abrasive Finishing for Wire Material Using a Rotating Magnetic Field

In this paper, we propose a new ultra-high-precision magnetic abrasive finishing method for wire material which is considered to be difficult with the existing finishing process. The processing method uses a rotating magnetic field system with unbonded magnetic abrasive type. It is believed that this process can efficiently perform the ultra-high-precision finishing for producing a smooth surface finish and removing a diameter of wire material. For such a processing improvement, the following parameters are considered; rotational speed of rotating magnetic field, vibration frequency of wire material, and unbonded magnetic abrasive grain size. In order to evaluate the performance of the new finishing process for the wire material, the American Iron and Steel Institute (AISI) 1085 steel wire was used as the wire workpiece. The experimental results showed that the original surface roughness of AISI 1085 steel wire was enhanced from 0.25 µm to 0.02 µm for 60 s at 800 rpm of rotational speed. Also, the performance of the removed diameter was excellent. As the result, a new ultra-high-precision magnetic abrasive finishing using a rotating magnetic field with unbonded magnetic abrasive type could be successfully adopted for improving the surface roughness and removing the diameter of AISI 1085 steel wire material.

The effects of TiO2 nanotube arrays with different diameters on macrophage/endothelial cell response and ex vivo hemocompatibility

Percutaneous coronary intervention with stenting is the most widely adopted surgical technique for the treatment of coronary disease.

Hemocompatibility of hyaluronan enhanced linear low density polyethylene for blood contacting applications

Despite their overall success, different blood-contacting medical devices such as heart valves, stents, and so forth, are still plagued with hemocompatibility issues which often result in the need for subsequent replacement and/or life-long anticoagulation therapy. Consequently, there is a significant interest in developing biomaterials that can address these issues. Polymeric-based materials have been proposed for use in many applications due to their ability to be finely tuned through manufacturing and surface modification to enhance hemocompatibility. In this study, we have developed a novel, hydrophilic biomaterial comprised of an interpenetrating polymer network (IPN) of hyaluronan (HA) and linear low density polyethylene (LLDPE). HA is a highly lubricous, anionic polysaccharide ubiquitously found in the human body. It is currently being investigated for a vast array of biomedical applications including cardiovascular therapies such as hydrogel-based regenerative cell therapies for myocardial infarction, HA-coated stents, and surface modifications of polyurethane and metals for use in blood-contacting implants. The aim of this study was to assess the in vitro thrombogenic response of the hydrophilic polymer surface, HA-LLDPE for future potential use as flexible heart valve leaflets. The results indicate that HA-LLDPE is non-toxic and reduces thromobogenicity as compared to LLDPE surfaces, asserting its feasibility for use as a blood-contacting biomaterial. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1964-1975, 2018.

Imaging of homeostatic, neoplastic, and injured tissues by HA-based probes

An increase in hyaluronan (HA) synthesis, cellular uptake, and metabolism occurs during the remodeling of tissue microenvironments following injury and during disease processes such as cancer. We hypothesized that multimodality HA-based probes selectively target and detectably accumulate at sites of high HA metabolism, thus providing a flexible imaging strategy for monitoring disease and repair processes. Kinetic analyses confirmed favorable available serum levels of the probe following intravenous (i.v.) or subcutaneous (s.c.) injection. Nuclear (technetium-HA, (99m)Tc-HA, and iodine-HA, (125)I-HA), optical (fluorescent Texas Red-HA, TR-HA), and magnetic resonance (gadolinium-HA, Gd-HA) probes imaged liver ((99m)Tc-HA), breast cancer cells/xenografts (TR-HA, Gd-HA), and vascular injury ((125)I-HA, TR-HA). Targeting of HA probes to these sites appeared to result from selective HA receptor-dependent localization. Our results suggest that HA-based probes, which do not require polysaccharide backbone modification to achieve favorable half-life and distribution, can detect elevated HA metabolism in homeostatic, injured, and diseased tissues.

Preparation and the kinetic stability of hyaluronan radiolabeled with 111In, 125I and 14C

Three different procedures for the labeling of hyaluronan (HA) with (111)In, (125)I and (14)C radionuclides were compared, and the kinetic stability of radiolabeled HA under different conditions (saline, artificial gastric juice and plasma) was established. Modification of HA structure with bifunctional chelating agents (DTPA) or with the prosthetic group (tyramine or tyrosine) was essential prior (111)In and (125)I labeling. These chemical labeling techniques were fast, simple and inexpensive, and labeled agents with a high specific activity were obtained. The only disadvantage of these methods was the occurrence of unknown functional groups in the HA molecule requiring further characterization of the compound. Conversely, HA labeling with (14)C by biotechnological synthesis was found to be rather expensive and time-consuming process. Although, the final product (14)C-HA was identical to natural HA its low specific activity presents certain limitation for its application in biological experiments. Stability studies showed that (14)C-HA and (125)I-Tm-HA were stable in all studied mediums. In the case of (125)I-Trs-HA, stability slightly decreased in rat plasma and in artificial gastric juice with increasing time. The least stable was (111)In-DTPA-HA, which degraded completely after 48h in artificial gastric juice. Kinetic stability studies may provide primary information concerning the properties of radiolabeled HA in vitro, which is essential for the use and explanation of its behavior in biological experiments.

Surface treatment of NiTi for medical applications

This article gives an overview of methods applied for surface treatment of nickel-titanium shape memory alloys in medical applications. The different methods are classified into the three major groups: <I>removal</I>, <I>oxidation</I> and <I>coating</I>. The principle behind each group of methods is explained and the pros and cons of the different methods are discussed.

Biomimetic hemocompatible coatings through immobilization of hyaluronan derivatives on metal surfaces

Biomimetic coatings offer exciting options to modulate the biocompatibility of biomaterials. The challenge is to create surfaces that undergo specific interactions with cells without promoting nonspecific fouling. This work reports an innovative approach toward biomimetic surfaces based on the covalent immobilization of a carboxylate terminated PEGylated hyaluronan (HA-PEG) onto plasma functionalized NiTi alloy surfaces. The metal substrates were aminated via two different plasma functionalization processes. Hyaluronan, a natural glycosaminoglycan and the major constituent of the extracellular matrix, was grafted to the substrates by reaction of the surface amines with the carboxylic acid terminated PEG spacer using carbodiimide chemistry. The surface modification was monitored at each step by X-ray photoelectron spectroscopy (XPS). HA-immobilized surfaces displayed increased hydrophilicity and reduced fouling, compared to bare surfaces, when exposed to human platelets (PLT) in an in vitro assay with radiolabeled platelets (204.1 +/- 123.8 x 10 (3) PLT/cm (2) vs 538.5 +/- 100.5 x 10 (3) PLT/cm (2) for bare metal, p < 0.05). Using a robust plasma patterning technique, microstructured hyaluronan surfaces were successfully created as demonstrated by XPS chemical imaging. The bioactive surfaces described present unique features, which result from the synergy between the intrinsic biological properties of hyaluronan and the chemical composition and morphology of the polymer layer immobilized on a metal surface.

Reactive epoxy-functionalized thin films by a pulsed plasma polymerization process

A novel plasma functionalization process based on the pulsed plasma polymerization of allyl glycidyl ether is reported for the generation of robust and highly reactive epoxy-functionalized surfaces with well-defined chemical properties. Using a multitechnique approach including X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and ellipsometry, the effect of the plasma deposition parameters on the creation and retention of epoxy surface functionalities was characterized systematically. Under optimal plasma polymerization conditions (duty cycle: 1 ms/20 ms and 1 ms/200 ms), reactive uniform films with a high level of reproducibility were prepared and successfully used to covalently immobilize the model protein lysozyme. Surface derivatization was also carried out with ethanolamine to probe for epoxy groups. The ethanolamine blocked surface resisted nonspecific adsorption of lysozyme. Lysozyme immobilization was also done via microcontact printing. These results show that allyl glycidyl ether plasma polymer layers are an attractive strategy to produce a reactive epoxy functionalized surface on a wide range of substrate materials for biochip and other biotechnology applications.

Biorecognition through layer-by-layer polyelectrolyte assembly: in-situ hybridization on living cells

Encapsulated cells were formed from the assembly of cationic and anionic alternating layers using a number of polyelectrolyte-based systems. Chitosan, alginate, hyaluronic acid, and oligonucleotides were used as polyelectrolytes to encapsulate individual E. coli cells, which were used as a model. Zeta potential measurements taken for both chitosan/alginate and chitosan/hyaluronic acid systems indicate successful layer-by-layer (LbL) deposition and gave full reversal of the surface change eight times. Layer adsorption was further observed by fluorescence microscopy, and, through a newly developed protocol for sample preparation, transmission electron microscopy micrographs clearly showed the presence of LbL assembly on the outer layer of the cell membrane, in the nanometer range. A second generation of E. coli cells could be grown from encapsulated first generation cells, demonstrating that the cellular activity was not affected by the presence of polyelectrolyte multilayers. Hybridization between attached oligonucleotide sequences and the complementary sequence was demonstrated by both fluorescence spectroscopy and microscopy. Fluorescence energy transfer data recorded after hybrid formation showed that at a molar ratio of 10:20 (donor:acceptor), Q and I were 92.3% and 52.5%, respectively, which suggests that fluorescein fluorescence was quenched by 92.3% and that the fluorescence of rhodamine was enhanced by 52.5%. Oligonucleotide incorporation was stabilized by deposition of four alternating layers, hence offering not only the potential use of the encapsulated cell as a bio-recognition system but also its application in a number of fields such as oligonucleotide delivery, gene therapy, and the use of DNA as an immunocompatible coating.

Coronary stents: a materials perspective

The objective of this review is to describe the suitability of different biomaterials as coronary stents. This review focuses on the following topics: (1) different materials used for stents, (2) surface characteristics that influence stent-biology interactions, (3) the use of polymers in stents, and (4) drug-eluting stents, especially those that are commercially available.

Engineering of Biomaterials Surfaces by Hyaluronan

This review addresses the area of study that defines the field of surface modification of biomedical materials and devices by hyaluronan (HA), as related to the exploitation of HA biological properties. To provide a comprehensive view of the subject matter, initial sections give a quick introduction to basic information on HA-protein and HA-cell interactions, together with some discussion on the bioactive role of HA in wound healing and related phenomena. This is followed by a description of current theories that correlate HA properties to its molecular structure in aqueous media, underlying how HA molecular details are crucial for its biological interaction and role. Finally, existing approaches to surface modification by HA are reviewed, stressing the need for HA-surface engineering founded on the knowledge and control of the surface-linked HA molecular conformation at the solid/aqueous interface.