Human aortic endothelial cell response to 316L stainless steel material microstructure

Endothelialization of Whey Protein Isolate-Based Scaffolds for Tissue Regeneration

BACKGROUND

Whey protein isolate (WPI) is a by-product from the dairy industry, whose main component is β-lactoglobulin. Upon heating, WPI forms a hydrogel which can both support controlled drug delivery and enhance the proliferation and osteogenic differentiation of bone-forming cells. This study makes a novel contribution by evaluating the ability of WPI hydrogels to support the growth of endothelial cells, which are essential for vascularization, which in turn is a pre-requisite for bone regeneration.

METHODS

In this study, the proliferation and antioxidant levels in human umbilical vascular endothelial cells (HUVECs) cultured with WPI supplementation were evaluated using real-time cell analysis and flow cytometry. Further, the attachment and growth of HUVECs seeded on WPI-based hydrogels with different concentrations of WPI (15%, 20%, 30%, 40%) were investigated.

RESULTS

Supplementation with WPI did not affect the viability or proliferation of HUVECs monitored with real-time cell analysis. At the highest used concentration of WPI (500 µg/mL), a slight induction of ROS production in HUVECs was detected as compared with control samples, but it was not accompanied by alterations in cellular thiol levels. Regarding WPI-based hydrogels, HUVEC adhered and spread on all samples, showing good metabolic activity. Notably, cell number was highest on samples containing 20% and 30% WPI.

CONCLUSIONS

The demonstration of the good compatibility of WPI hydrogels with endothelial cells in these experiments is an important step towards promoting the vascularization of hydrogels upon implantation in vivo, which is expected to improve implant outcomes in the future.

Evaluation of in vitro corrosion behavior of zinc-hydroxyapatite and zinc-hydroxyapatite-iron as biodegradable composites

Zinc (Zn) based biomaterials have been emerged as one of the capable biodegradable materials for biomedical applications because of the ideal degradation properties. In the present work, corrosion kinetics of Zn-hydroxyapatite (HA), and Zn-HA-iron (Fe) materials developed using microwave sintering process were investigated. The effect of the inclusion of HA and Fe in Zn on corrosion properties have been evaluated in the simulated body fluid solution. Further, the wettability test of the developed composites was performed to confirm the hydrophilic nature of the surface of all samples. Zn-3HA was found to have better hydrophilicity as compared to other samples. Increased corrosion rate and pH of Zn-5HA-2Fe samples were attributed to the addition of HA and Fe in the Zn matrix. The corrosion rate and weight loss rate from electrochemical and immersion testing of all samples were found in the order from highest to lowest: Zn-5HA-2Fe > Zn-3HA > Zn-3HA-2Fe > Zn. The highest cell viability nearly 100% was obtained for Zn-3HA samples, whereas other samples also showed sufficient biocompatibility to be utilized for biomedical applications.

Effect of Microstructure on Contact Angle and Corrosion of Ductile Iron: Iron-Graphite Composite

Ductile iron samples with similar compositions and varying microstructures were uniformly abraded, and the effects of phase fractions (ferrite, pearlite, and graphite) on the apparent contact angle (with water) and corrosion characteristics of ductile iron were investigated. We also investigated the effect of droplet volume on the apparent contact angle of ductile iron. Irrespective of the droplet size, the ductile iron system followed the Wenzel model of wetting, and the contact angle increased with increasing droplet volume. The Wenzel and Cassie-Baxter contact angles were calculated, and the calculated results agreed well with the experimental results. It was experimentally proven that pearlite is more susceptible to corrosion than ferrite and graphite, and a higher portion of pearlite in the microstructure can be detrimental to the corrosion resistance of the material. Understanding the relationship between the microstructure, contact angle, and corrosion can be used to develop materials with higher contact angle and corrosion-resistant microstructures. Using metal pipes that have high contact angles is desirable because artificial coatings on metal pipes can degrade over time leading to high cost of replacement and contamination to water systems.

P(VDF-TrFE) polymer-based thin films deposited on stainless steel substrates treated using water dissociation for flexible tactile sensor development

In this work, deionized (DI) water dissociation was used to treat and change the contact angle of the surface of stainless steel substrates followed by the spin coating of P(VDF-TrFE) material for the fabrication of tactile sensors. The contact angle of the stainless steel surface decreased 14° at −30 V treatment; thus, the adhesion strength between the P(VDF-TrFE) thin film and the stainless steel substrate increased by 90%. Although the adhesion strength was increased at negative voltage treatment, it is observed that the crystallinity value of the P(VDF-TrFE) thin film declined to 37% at −60 V. In addition, the remanent polarization value of the P(VDF-TrFE) thin film declined from 5.6 μC/cm² to 4.61 μC/cm² for treatment voltages between −5 V and −60 V. A maximum value of approximately 1000 KV/cm of the coercive field value was obtained with the treatment at −15 V. The d33 value was approximately −10.7 pC/N for the substrate treated at 0 V and reached a minimum of −5 pC/N for treatment at −60 V. By using the P(VDF-TrFE) thin-film as the sensing material for tactile sensors, human pulse measurements were obtained from areas including the carotid, brachial, ankle, radial artery, and apical regions. In addition, the tactile sensor is suitable for monitoring the Cun, Guan, and Chi acupoints located at the radial artery region in Traditional Chinese Medicine (TCM). Waveform measurements of the Cun, Guan, and Chi acupoints are crucial because, in TCM, the various waveforms provided information regarding the health conditions of organs.

The underlying biological mechanisms of biocompatibility differences between bare and TiN-coated NiTi alloys

TiN coating has been demonstrated to improve the biocompatibility of bare NiTi alloys; however, essential biocompatibility differences between NiTi alloys before and after TiN coating are not known so far. In this study, to explore the underlying biological mechanisms of biocompatibility differences between them, the changes of bare and TiN-coated NiTi alloys in surface chemical composition, morphology, hydrophilicity, Ni ions release, cytotoxicity, apoptosis, and gene expression profiles were compared using energy-dispersive spectroscopy, scanning electron microscopy, contact angle, surface energy, Ni ions release analysis, the methylthiazoltetrazolium (MTT) method, flow cytometry and microarray methods, respectively. Pathways binding to networks and real-time polymerase chain reaction (PCR) were employed to analyze and validate the microarray data, respectively. It was found that, compared with the bare NiTi alloys, TiN coating significantly decreased Ni ions content on the surfaces of the NiTi alloys and reduced the release of Ni ions from the alloys, attenuated the inhibition of Ni ions to the expression of genes associated with anti-inflammatory, and also suppressed the promotion of Ni ions to the expression of apoptosis-related genes. Moreover, TiN coating distinctly improved the hydrophilicity and uniformity of the surfaces of the NiTi alloys, and contributed to the expression of genes participating in cell adhesion and other physiological activities. These results indicate that the TiN-coated NiTi alloys will help overcome the shortcomings of NiTi alloys used in clinical application currently, and can be expected to be a replacement of biomaterials for a medical device field.