Forensics Applications of Raman Spectroscopy, ATR FT-IR, and Chemometrics

As forensic analysis continues to advance, such as in the understanding of source identification and analysis of trace quantities of bodily fluids, spectroscopic techniques and machine learning are playing a significant role. Igor K. Lednev, a chemistry professor at the University at Albany, SUNY, in Albany, New York, has been working in this field with his team. The analytical methods currently under investigation include Raman spectroscopy, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, and advanced chemometric classification and analysis methods. We recently interviewed him about his work.

In one recent study, you reported the development of a multivariate discriminant model using ATR FT-IR spectra of dry urine to identify the sex of the donor (1). Which specific analytes are being measured for this discriminant analysis? What specific chemometric approach was required for optimizing the discrimination?

We utilized one of the multivariate statistical methods called partial least-squares discriminant analysis (PLS-DA).To improve further the discrimination, we also applied genetic algorithm (GA) analysis to the derivative urine spectra. The GA is a computational method that identifies spectral regions that contribute the most to the differentiation power of the model. In addition, the spectral regions selected by GA may be instrumental for understanding the chemical origin of sex differences in urine samples. Although a specific biochemical assignment based on the regions selected by GA was challenging, there was good agreement with the characteristic spectral peaks of creatinine. Creatinine is a waste product from creatine, which is consumed in muscles. Detection and quantification of creatinine in biological fluids, particularly urine, have been previously investigated. It has been shown that the concentration of creatinine in urine depends on the muscle mass and donor sex, as the urine of male subjects typically has a higher concentration of creatinine than that of females. Let me also mention that this was a collaborative project between our laboratory and Prof. Takeaki Ozawa’s laboratory at the University of Tokyo. A very talented PhD student, Ayari Takamura, spent half a year in our laboratory conducting research.

Research using ATR FT-IR spectroscopy was used to discriminate sex and race based on the analysis of bloodstain samples (15). In this work, ATR FT-IR spectra were acquired from dry bloodstains and PLS-DA was used to classify these sample spectra. What do you think is the basis of the fundamental chemical differences in these samples that was detected using ATR FT-IR?

To address this question, we used GAs and determined ATR FT-IR spectral regions that contributed the most to the differentiation of blood samples based on the donor sex and race. Specifically for the sex differentiation, we observed a region corresponding to lipid contribution that is consistent with the literature, reporting different levels of high-density lipoprotein (HDL) cholesterol and double bond index in fatty acids within the blood serum of males and females. In addition, a spectral region with a contribution from carbohydrates was selected by GA that is consistent with the literature data, indicating higher levels of glucose in blood of female donors. As for the race differentiation, the results of our analysis of ATR FT-IR spectral data are consistent with the literature indicating that the levels of lipoproteins, apolipoproteins, hemoglobin, and total protein concentration in blood varies with the donor race.

What would you consider to be the most meaningful contributions of your work, including teaching and patent work?

An academic career is attractive to me because it gives plenty of opportunity to make various meaningful contributions including those to a scientific field, profession, and even society. Training the next generation of experts is probably the most important duty of the university professor. I am very happy that all students graduated from our lab are developing successful careers in pharma, major crime laboratories, and academia. I guess publishing about 250 research papers and reaching the h-index of 58 might indicate a noticeable contribution to the scientific field, but I leave it for my peers to evaluate. After many years of fundamental research, I have shifted the focus of our program toward applied science during the last decade or so, specifically targeting the development of new methods for medical diagnostics and forensic purposes. Most recently, I cofounded two startup companies aiming at the commercialization of our patented technologies. Should this activity be successful, it will probably make the most meaningful societal contribution.

Would you share with our readers to describe your work ethic, philosophy, and how you plan your daily or weekly work schedule?

This is a serious question, which deserves a separate conversation. Briefly, my work ethic is probably quite standard: be honest, be respectful, and work hard. Although this might sound trivial, it is not. One of the key elements of my teaching philosophy is to make sure that students learn how to learn. As for the research training, my main approach is to give students as much independence and responsibility as they can handle. In my opinion, and based on many years of experience, this is the best way to prepare students for their future careers. I am investing time and significant effort to generate a priority “wish” list for my activities. My daily and weekly work schedule includes my duties (teaching, service, and professional) and then, if there is time left, top activities from the priority list.

What words of wisdom do you have for any young people interested in a scientific research career?

Go for it! However, do not expect that it will be easy. Good luck!

References

(1) A. Takamura, L. Halamkova, T. Ozawa, and I.K. Lednev, Anal. Chem. 91(9), 6288–6295 (2019).

(2) C. Taylor, E. Mistek, L. Halámková, and I.K. Lednev, Vib. Spectrosc. 109, 103065 (2020).

(3) C.K. Muro, K.C. Doty, L.d.S. Fernandes, and I.K. Lednev, Forensic Chem. 1(1), 31–38 (2016).

(4) R. Rosenblatt, L. Halámková, K.C. Doty, E.A.C. de Oliveira, and I.K. Lednev, Forensic Chem. 16, 100175 (2019).

(5) A. Weber and I.K. Lednev, Forensic Chem. 19, 100248 (2020).

(6) K.C. Doty, G. McLaughlin, and I.K. Lednev, Anal. Bioanal. Chem. 408(15), 3993–4001 (2016).

(7) A. Wojtowicz, A. Weber, R. Wietecha-Posluszny, and I.K. Lednev, Spectrochim. Acta A Mol. Biomol. Spectrosc. 119172 (2020).

(8) K.C. Doty, C.K. Muro, and I.K. Lednev, Forensic Chem. 5, 1–7 (2017).

(9) B. Vyas, L. Halamkova, and I.K. Lednev, Forensic Chem. 100247 (2020). https://doi.org/10.1016/j.forc.2020.100247

(10) K. Virkler and I.K. Lednev, Forensic Sci. Int. 181, e1–e5 (2008).

(11) G. McLaughlin, M.A. Fikiet, H.-o. Hamaguchi, and I.K. Lednev, J. Raman Spec- trosc. 50, 1147–1153 (2019).

(12) G. McLaughlin, V. Sikirzhytski, and I.K. Lednev, Forensic Sci. Int. 231(1-3), 157–166 (2013).

(13) A. Sikirzhytskaya, V. Sikirzhytski, G. McLaughlin, and I.K. Lednev, J. Forensic Sci. 58(5), 1141–1148 (2013).

(14) E. Al-Hetlani L. Halámková, M.O. Amin, and I.K. Lednev, J. Biophotonics e201960123 (2019). https://doi.org/10.1002/jbio.201960123

(15) E. Mistek, L. Halámková, and I.K. Lednev, Forensic Chem. 16, 100176 (2019).

Igor K. Lednev is Professor of Chemistry at the University at Albany, State University of New York. His research is focused on the development of novel laser spectroscopy for medical diagnostics and forensic purposes. He has authored over 240 publications in peer-reviewed journals reaching h-index of 58. He is a cofounder of two startup companies targeting the commercialization of his technology protected by seven patents. He is on the editorial boards of Raman Spectroscopy, Forensic Chemistry, Spectroscopy magazine, and High Energy Chemistry journal. He served as an advisory member on the White House Subcommittee for Forensic Science. He is a cofounder of the NIJ Forensic Science Symposium at Pittcon (the world-largest Analytical Chemistry congress); the symposium became a regular annual event including 34 invited talks and a poster session. He is a Fellow of the Society for Applied Spectroscopy and the Royal Society of Chemistry (UK). Media covered his work over 90 times including TV and radio interviews, publications in the Wall Street Journal, Chemical & Engineering News, Forensic Magazine, etc. Discovery Channel Canada featured his work on forensic Raman spectroscopy. Congressman Tonko featured his research at the U.S. House of Representatives Hearing on the advancements in forensic science in September 2019. Dr. Lednev received several prestigious awards including Gold Medal Award from NY/NJ Section of the Society for Applied Spectroscopy, Guest Prof. Fellowship from the Friedrich-Schiller-University, Research Innovation Award from Research Corporation, Chancellor’s Award for Excellence in Scholarship and Creative Activities, and CAS Dean’s Award for Outstanding Achievements in Teaching. For his development work, Lednev and coworkers have just received a Phase I Small Business Technology Transfer (STTR) grant from the U.S. National Science Foundation.

Jerome Workman, Jr. is the Senior Technical Editor for LCGC and Spectroscopy. Direct correspondence to: jworkman@mjhlifesciences.com