Quantifying Platinum Binding on Protein-Functionalized Magnetic Microparticles with Single Particle-ICP-TOF-MS: A SciX Interview with Strock Award Recipient Benjamin T. Manard

Platinum and platinum-based materials and compounds have been found essential for a variety of applications, resulting in their being identified as critical materials for ensuring a secure energy supply and a positive economic future. Platinum is used for catalysis in fuel cells, hydrogen production, petroleum refining, and to provide environmental benefits–namely in automotive catalytic converters and renewable energy technologies. A recent paper by Benjamin T. Manard of the Chemical Sciences Division at Oak Ridge National Laboratory (Oak Ridge, Tennessee) and associates describes an analytical procedure, single particle-inductively coupled plasma-time-of-flight-mass spectrometry (SP-ICP-TOF-MS), being utilized to determine the platinum-binding efficiency of protein-coated magnetic microparticles. Manard will be receiving the Lester W. Strock Award, given by the New England Section of the Society for Applied Spectroscopy in recognition of a selected publication of substantive research or application of analytical atomic spectrochemistry in the fields of earth science, life sciences, or stellar and cosmic sciences. The award will be presented at this year’s SciX conference, to be held from October 20 through October 25, in Raleigh, North Carolina. As part of an ongoing series of this year’s SciX conference honorees, Benjamin spoke to us about this study, its significance, and the next steps in its development.

In your paper (1), you discuss the initial evaluation of a single particle-inductively coupled plasma-time-of-flight-mass spectrometry (SP-ICP-TOF-MS)-based method, that was developed to determine the platinum binding efficiency of protein-coated magnetic microparticles. What are the benefits of determining this?

There is a need to develop and engineer novel enzymes which can be used to recover critical materials (for example, platinum) from complex matrices. Such critical materials could be used in a wide variety of applications, including electronic devices. An approach to test these respective enzymes involved attaching them to protein-coated magnetic microparticles. With this configuration, the enzyme could be used to capture such material and efficiently separate it out of a matrix using the magnetic properties of the microparticles. One difficultly in this approach is being able to accurately quantify the amount of platinum which was captured. Initially, our team employed a bulk digestion-based method of the microparticles, with ICP-MS detection, to determine the amount of platinum which was captured. Unfortunately, while a sensitive and robust approach, this technique homogenizes the sample which prevents us from discerning from free- and bound- platinum. This accelerated our motivation to start employing “single particle (SP)” ICP-MS in our laboratory. This SP approach allowed for the direct determination of the platinum content, on the per-particle level. When the method was established, we were able to quickly identify which enzymes could capture platinum more effectively.

What is the significance of measuring the platinum binding efficiency of protein-coated magnetic microparticles?

The significance is immediately recognized when trying to compare platinum loading per particle. This information can provide the analytical basis for next generation engineering of enzymes to assist in recovering of critical materials. Being able to measure the platinum binding efficiency of the protein-coated magnetic microparticles allows for the direct comparison of different enzymes. This information can subsequently guide the engineering of enzymes for this specific application.

What made you believe that this technique would be the best to help fulfill your analytical goals?

As mentioned previously, the immediate benefit was realized in SP-ICP-MS’s ability to discern between bound platinum, on the particle level, versus any free and background platinum. Additionally, when combining the SP-ICP-MS analysis with a high throughput introduction system (2), we were able to analyze many samples, respective standards, and blanks rapidly and efficiently. This development is critical when the analysis of multiple samples (such as enzyme-coated particles) is to be accomplished with their own respective experimental variables.

Were there any other measurement techniques considered?

For sure; in fact, our initial approach was to use laser-induced breakdown spectroscopy (LIBS), and subsequently a bulk-digestion-based ICP-MS approach. We believe this SP-ICP-MS approach was easily deemed the best choice.

Were any changes or adaptation of existing equipment involved, and were there challenges associated with making these changes?

No real changes to existing equipment were made. The key development would have been regarding the sample introduction system. Here, we employed an automated single cell introduction system which allowed for sample mixing for efficient introduction (2). In fact, once configured, we were able to analyze these particles, unattended, for over 8 h.

Other than the technique and equipment being used, does your work differ from what has been previously done by yourself or others?

Most of my research is directed toward elemental and isotopic analysis relevant to national security application spaces (3,4). This project was, of course, a change of pace for us. It was fun to dive into a biological-based arena. In addition to being a different application space, this was truly the first time our laboratory implemented single particle-ICP-MS. With the recent procurement of a TOF-based instrument, we were excited to put its advantages (compared to other ICP-MS platforms) to use!

Briefly state your findings.

Here, we can characterize magnetic microparticles, which would be used as a substrate for enzyme binding. This was extremely important as we needed a very uniform substrate such that any analytical differences could be attributed to the enzyme itself, and not the microparticle. Once characterized, we demonstrated its usefulness for capturing platinum. We report in this manuscript that the azurin-coated microparticles had nearly 2x more platinum bound in comparison to the streptavidin-coated particles. Additionally, more than 65% of the particle population for the azurin-coated particles had effectively captured platinum.

Was there anything you observed that was unexpected in terms of analysis results and that stands out from your perspective?

The primary result, which we thought was extraordinary, was the characterization of the very monodisperse, magnetic, microparticles. In fact, we had explored other manufacturers for very robust and well-characterized substrates, and the results were indicating that these would not be friendly to making effective analytical determinations. For instance, if vendors were selling different nominal size particles, the distribution of these particles was quite variable. This inconsistency would make the ability to quantify platinum particles more challenging.

Were there any serious or noteworthy limitations or challenges you encountered in your work?

Challenges existed in the pre-planning stages in finding a manufacturer of monodisperse microparticles.

What best practices can you recommend in this type of analysis for both instrument parameters and data analysis?

Characterizing and understanding each step of the procedure (cradle to grave if you will) allowed for us to ultimately provide a thorough analysis. Additionally, we approached this analysis from using multiple techniques, combining scanning electron microscopy, SP-ICP-MS, and bulk digestion-based ICP-MS, which provided further confidence in the results that were reported.

Can you please summarize the feedback that you have received from others regarding this work?

I feel the spectroscopy community was very excited about the magnetic microparticles. In fact, we presented this work at SciX 2023 (held in Reno, Nevada), and multiple researchers asked for information regarding the particles. These particles can open the door for a wide variety of chemistries and experiments relevant in various application spaces.

What are the next steps in this research?

To further explore various enzymes, proteins, and chelators, and their ability for metal binding. Now that the ability to bind metals (in this case, platinum) to these enzyme-functionalized microparticles has been established, other arenas should be explored, including other instances of critical materials, such as lanthanides and platinum group elements.

What are your thoughts regarding your being named the recipient of the Strock Award?

It’s truly an honor. I have been involved with the atomic spectroscopy community since my PhD studies at Clemson University (under Professor R. Kenneth Marcus). I have always found it fascinating to be able to use atomic spectroscopy to tackle challenging problems in various application spaces. Here at my current position at Oak Ridge National Laboratory (ORNL), we push our group to be at the cutting edge of analytical atomic spectrochemistry, which immediately includes single particle-ICP-MS, laser ablation-ICP-MS, various ICP-MS platforms (such as TOF, triple quadrupole, and magnetic sector with multi-collector detector arrays), laser induced breakdown spectroscopy (LIBS), and many more. I believe that, with analytical atomic spectrochemistry, we can tackle challenging problems in various mission spaces within the realm of earth science, life science, national security, and environmental applications. This career path has been heavily set by the “team.” This award would not be possible without extensive collaborations with colleagues at ORNL, colleagues at the Department of Energy (DOE) Laboratories, colleagues from academia, colleagues from instrument manufacturers, and the sum of the mentors that have influenced me along this path. It’s an honor to be considered amongst the previous recipients of the Strock Award.

References

1. Bradley, V. C.; Manard, B. T.; Hendriks, L.; Dunlap, D. R.; Bible, A. N.; Sedova, A. et al. Quantifying Platinum Binding on Protein-Functionalized Magnetic Microparticles Using Single Particle-ICP-TOF-MS. Anal. Meth. 2024, 16, 3192–3201.DOI: 10.1039/D4AY00268G

2. Manard, B. T.; Bradley, V. C.; Quarles, C. D.; Hendriks, L.; Dunlap, D. R.; Hexel, C. R.; Sullivan, P.; Andrews, H. B. Towards Automated and High-Throughput Quantitative Sizing and Isotopic Analysis of Nanoparticles via Single Particle-ICP-TOF-MS. Nanomaterials2023,13 (8), 1322. DOI: 10.3390/nano13081322

3. Manard, B. T.; Rogers, K. T.; Ticknor, B. W.; Metzger, S. C.; Zirakparvar, N. A.; Roach, B. D.; Bostick, D. A.; Hexel, C. R. Direct Uranium Isotopic Analysis of Swipe Surfaces by Microextraction-ICP-MS. Anal. Chem.2021,93, 32, 11133–11139. DOI: 10.1021/acs.analchem.1c01569

4. Manard, B. T.; Quarles, Jr., C. D.; Bradley, V. C.; Spano, T. L.; Zirakparvar, N. A.; Ticknor, B. W.; Dunlap, D. R.; Cable-Dunlap, P.; Hexel, C. R.; Andrews, H. B. Uranium Single Particle Analysis for Simultaneous Fluorine and Uranium Isotopic Determinations via Laser-Induced Breakdown Spectroscopy/Laser Ablation-Multicollector-Inductively Coupled Plasma-Mass Spectrometry. J. Am. Chem. Soc. 2024, 146, 14856–14863. DOE: 10.1021/jacs.4c03965

Benjamin T. Manard is a Senior R&D Staff Scientist and the Group Leader of the Chemical & Isotopic Mass Spectrometry Group at Oak Ridge National Laboratory (ORNL). He received a B.S. in Chemistry from Georgia Southern University (2009) and a Ph.D. in Analytical Chemistry from Clemson University (2014) under Professor R. Kenneth Marcus. After graduation, Ben was awarded a Glenn T. Seaborg Postdoctoral Fellowship at Los Alamos National Laboratory (LANL) before transitioning into a Staff Scientist position. In 2018 Ben began working at ORNL within the Chemical and Isotopic Mass Spectrometry Group and has led efforts directed toward developing analytical methodologies in elemental/isotopic analysis by utilizing unique sampling mechanisms (e.g. laser ablation, single particle, and microextraction) coupled with inductively could plasma – mass spectrometry (ICP-MS) to tackle challenging problems related to national security, advanced energy generation, biosciences, and environmental applications. Ben has authored over 60 journal articles, been featured on 9 journal covers, authored 1 book chapter, and has received recognitions including The Department of Energy Secretary of Energy’s Achievement Award (2022), The Analytical Scientist’s Top 40 Under 40 Power List (2022), and The Journal of Analytical Atomic Spectroscopy Emerging Investigator (2023). Additionally, he is on the Governing Board for The Society for Applied Spectroscopy and Editorial board of Applied Spectroscopy Practica. Photo courtesy of Manard.