We welcome Ms. Emily Tom, who has joined our research team as an undergraduate researcher. Emily is senior in materials science and engineering program. She will assist our team in research on zinc- and magnesium-based biodegradable alloys.
Congratulations to Roger Guillory for defending his PhD dissertation entitled “Degradable Zinc Material Characteristics and its Influence on Biocompatibility and in an In Vivo Murine Model” on August 20, 2019. Roger is also leaving us to take a postdoctoral fellow position at Northwestern University in Evanston (near Chicago). We wish him both professional and personal successes in his new place and in this new chapter of his live!
Our collaborators from Northeastern University in Shenyang published a new paper on Reverse Flotation of Hematite from Quartz with Magnetic Seeding Aggregation in the Minerals Engineering journal. In this work, fine magnetite was used as a magnetic seed to enhance the separation efficiency of fine hematite from quartz during reverse micro-flotation. Gradual increases in hematite recovery and iron grade were accomplished with increasing magnetite content, whereas the iron content in quartz reject decreased. Particle size analysis, sedimentation tests, and scanning electron microscopy analysis of hematite from the separation process confirmed aggregation of hematite with magnetite particles. The measurements of magnetic susceptibility of product and reject indicate predominant aggregation of magnetite with hematite, and only marginal with quartz. Zeta-potential analysis and colloidal force analysis confirmed attractive interactions between magnetite and hematite, and repulsive between magnetite and quartz. Therefore, fine hematite aggregation with magnetite particles reduces coating of quartz with fine hematite, benefiting the flotation purification of fine hematite from quartz in terms of both recovery and grade.
We are glad to report that the journal impact factor (IF) for Surface Innovations rose to 2.333 from 1.268 in 2018. This is the third year in a row when the journal climbs in ranking. The journal is listed under two categories:
1) Materials Science, Coatings & Films
The journal climbed from 14th to 6th position among 20 listed journals. Percentile improve from 74% in last year to 30% in 2019. It places the journal under Q2 category.
2) Physical Chemistry
The journal moved from 118th position to 78th among 148 journals. The percentile improved from 81% (Q4) to 53% (Q3).
Mr. Kyle Hrubecky has joined our research team as a PhD Candidate. He will work on just-awarded NIH R01 grant, developing new zinc alloys for medical applications. Kyle worked with us in the past as undergraduate researcher, during his junior year.
The U.S. National Institute of Health has awarded us with R01 funding. Our laboratory has been working to refine the composition and microstructure of biodegradable Zn-based binary alloys and test their behavior in the vascular environment over the last four years in an effort to develop a metal with mechanical properties and biocompatibility required for endovascular stent applications. Having contributed enormously to the scientific understanding of Zn-based systems, we are now ready to develop more complex Zn-based alloys with 2-3 alloying elements that meet benchmark values for biodegradable stents, including: 1) have superior corrosion fatigue resistance that eliminates early stage (6 to 9 months) fracturing of biodegradable stents (common problem in Mg-based and Zn-based stents prototyped in the last several years); 2) maintain in vivo corrosion rates close to the 0.02 mm/year value; 3) exhibit >200 MPa yield strength, and >25-30% elongation to failure; and 4) demonstrate biocompatibility in terms of short- and long-term inflammatory responses, re-endothelialization, and suppressed intimal hyperplasia, similar or better than 316L stainless steel (industrial standard for stent materials).
Our new paper entitled In Vitro Corrosion and in Vivo Response to Zinc Implants with Electropolished and Anodized Surfaces has been published in the ACS Applied Materials & Interfaces journal. Roger Guillory, PhD candidate, and Prof. Jeremy Goldman from Biomedical Engineering led this project. In this study, pure zinc samples were electropolished (EP) and anodized (AD) to engineer oxide films with distinctive physical and degradation characteristics, as determined by potentiodynamic polarization, electrochemical impedance spectroscopy and static immersion tests. The samples were then implanted within the aortic lumen of adult Sprague Dawley rats to determine the influence of surface engineering on biocompatibility responses to Zn implants. It was found that in vitro corrosion produced a porous corrosion layer for the EP samples and a densified layer on the AD samples. The AD material was more resistant to corrosion, while localized corrosion and pitting was seen on the EP surface. Interestingly, the increased variability from localized corrosion due to surface film character translated directly to the in vivo performance, where 100% of the AD implants but only 44% of the EP implants met the biocompatibility benchmarks. Overall, the results suggest that oxide films on degradable zinc critically affect early neointimal progression and overall success of degradable Zn materials.
We are glad to share with you the content of the Issue 3-4 of 2019 of Surface Innovations with nine papers on variety of topics related to surfaces and interfaces, including Invited Feature Article on chemistry of self-adaptive materials prepared by Prof. Ekaterina Skorb and her team. Hope you will find something interesting in this collection.
The first and only one review on history of contact angles was prepared by a team of international experts led by Prof. Drelich. The contact angle is one of the most sensitive experimental values describing a junction between three phases, being influenced by the composition and properties of contacting media as well as the structure and composition of interfaces involved. The origins and importance of the contact angle in analysis of three phase systems dates back to the famous works on cohesion and adhesion of fluids published by Thomas Young in 1805 and later Athanase Dupré in 1869. Since then, the contact angle has remained one of the most important values measured experimentally during characterization of solids and their wetting characteristics. Such measurements, however, involve solid surfaces that deviate from the idealized ones used in thermodynamic and mechanical modelling of three-phase junction by Young, Dupré, and others, and there is typically more than one value of contact angle measured on such surfaces. As a result, the attention of scientists and researchers in the last two centuries has been on development of methods for accurate contact angle measurements, interpretation of experimental values, and understanding the causes for contact angle value variation and contact angle hysteresis. The article entitled Contact Angles: History of Over 200 Years of Open Questions, and published in the Surface Innovations journal, reviews advancements made in interpretation of experimental contact angles and their use in characterization of solid surfaces.
Our close collaborator Prof. Jeremy Goldman from the Biomedical Engineering program has been awarded with the NIH R15 grant entitled Inhibition of Neointimal Hyperplasia by Zinc-based Biodegradable Arterial Devices. This two-year project, to which Prof. Jaroslaw Drelich serves as Co-PI, will allow us to correlate a range of zinc and zinc alloy corrosion rates with the degree of suppressed intimal hyplerplasia. We hypothesize that a corrosion rate that is too low will preserve mechanical strength of the metal but not effectively suppress intimal hyperplasia, while a rate that is too high will prematurely degrade the mechanical scaffold and simultaneously produce toxic effects that provoke harmful inflammatory responses and ultimately exacerbate intimal hyperplasia. Under this project, we will also progress our efforts in engineering of implant surfaces by controlling the surface oxide film thickness and its quality.