Friday, December 10, 2021

Culpepper working within a fume hood in Scott R. Daly Research Laboratory
Culpepper working within a fume hood in Scott R. 
​​​​​Daly Research Laboratory 2021.

From his time spent as an undergraduate researching urban park soil through his current PhD research regarding platinum-based drug candidates used for cancer treatment, working with metals has become a specialty for National Science Foundation Graduate Research Fellow (GRFP) and GEM Consortium Institution Fellow, Johnathan Culpepper. His enthusiasm for working with metals and inorganic research stems from his interest in science that can be applied to improve human health and our society.

“Anytime I was exposed to opportunities that had less of a biological focus I would go in that direction,” Culpepper says. “As an undergraduate at the Medgar Evers College of the City University of New York, I was performing soil analysis in New York City urban parks to see if any legacy pollutants were left in the parks that children were playing in. So, there has always been some sort of metal or inorganic chemistry involved in my research.”

He continued his work with metals while obtaining his master of science degree in civil and environmental engineering (CEE) at the University of Iowa by researching lab scale groundwater remediation of chlorinated solvents and investigating how iron oxides, such as magnetite, can aid in cleaning up groundwater aquifers. Culpepper enjoyed the multidisciplinary side of the engineering program but narrowed his focus to chemistry to work toward his doctorate degree. Culpepper had a seamless transition analyzing metals in water as an environmental engineer to researching metals from an inorganic chemist’s perspective.

Headshot photo of Culpepper
NSF-GRFP Fellowship Award photos at Seamans
Center 2021.

“In chemistry I’m still working with metals, but in terms of medical applications or as catalysts,” Culpepper says. “There are always some useful applications, some end product, or some goal in mind to help society in the long run. That is what drew me to this research.”

Culpepper was able to combine his interest in metals with his interest in improving human health by searching for a solution to the fatal problem that popular anticancer drug, cisplatin, can create. Cisplatin is a platinum-based drug used to mitigate cancer but its distribution throughout the body cannot be seen under the medical imaging process known as PET (positron emission tomography). This is a problem as accumulation of cisplatin near healthy organs can result in severe side effects, such as hearing loss if gathered near the ear, or kidney failure if accumulated near the kidney, and early detection of these issues is essential to help the patient.

Culpepper sets out to create a platinum-based drug that will treat the cancer and also be detectable in the body by tagging fluorine to a boron-containing reactive site within a class of molecules called triaminoborane complexes (TBDPhos). Transition metal complexes are molecules that typically contain one central metal atom which is surrounded by groups of organic atoms (carbon, oxygen, nitrogen) known as ligands.

“I’ve been making potential platinum-based metallodrugs with fluorine that can, if stable in water, have the benefit of both having that metal site, and the new feature that allows you to image and see where that drug is going and distributing in the body real-time.”

Culpepper describes his work as a proof of concept. After the TBDPhos platinum complexes were made, water stability tested, and methods to add the fluorine atom to the boron site were achieved, Culpepper demonstrated which parts of the molecule stays intact or falls apart under conditions in water.

Culpepper standing in front of a presentation board
Presentation at the Spring 2019 American Chemical  
Society ACS National Meeting in Orlando, Florida.

Demonstrating the molecule’s stability in water imitates how it will react in the body and can aid in changing the way scientists approach designing anticancer drugs.

Culpepper successfully defended his doctoral thesis in November 2021 and while he moves on from his academic career, his findings can be used by other researchers to continue designing new drugs and tools for cancer treatment. Culpepper is now pursuing a career as a materials scientist at Corning Incorporation in New York. In this new position, he will use the knowledge and skills from his graduate experiences at Iowa to design and test various materials to develop new products.

“Most of my experiences in graduate school has either been the design or the synthesis of new complexes,” Culpepper states. “A lot of the novelty I enjoy in the sciences starts with researching a societal problem to address, making new things, characterizing them and exploring or testing their usefulness.”