Event date:
Oct 4 2022 9:30 am

A research talk: Bifunctional Near-Infrared Light Responsive Gold Nanorods for Phototherapy of Gram-Negative Escherichia Coli

Increasing prevalence of antibiotic resistance presents a global health crisis. Gram-negative bacteria, in particular are resistant to a wide range of drugs due to their specialized outer membranes. Enediyne natural products have exhibited remarkable potency against biological cells. Their potency comes from Bergman cyclization of the enediyne core that generates reactive diradical species and can be triggered by a heat stimulus. Plasmonic gold nanoparticles have the capability of converting irradiated light into heat via non radiative properties. Gold nanorods (AuNRs) can be tuned to strongly absorb near-infrared (NIR) radiation which lies in the biological transparency window. We have shown that octa-4-en-2,6-diyne-1,8-diamine (EDDA) molecules functionalized on AuNR surface can be activated to generate diradical species through NIR irradiation of nanorods. In order to localize the nanorods on bacterial cells, we also coated our AuNRs with Polymyxin B nonapeptide (PMBN), a cationic cyclic peptide that specifically targets the lipopolysaccharide component of the outer membrane of Gram-negative pathogens. We have explored our strategy by treating DH5⍺ strain of Escherichia coli with our bifunctional AuNRs. We find that, following attachment of nanorods to DH5⍺, 785nm NIR laser irradiation results in a significant reduction in the viability of bacterial cells. We identify that the photothermal heat generation of nanorods and reactive diradical generation by EDDA both contribute towards DH5⍺ cell death.


Mohammad Azhar Mehfooz (Ph.D. candidate Indiana University, Bloomington) completed his B.S. in Chemistry in 2017 under the supervision of Professor Basit Yameen. His senior year project was titled “Synthesis and functionalization of Gold nanoparticles for the early detection Lung cancer biomarkers” The advisors for this project were Professor Basit Yameen and Professor Habib-ur-Rehman. He was also trained by Professor Rahman Shah Zaib Saleem and Professor Ghayoor Abbas Chotana in Summer research projects. 

He joined Indiana University Chemistry department in Fall of 2017 where he is currently a Ph.D. candidate. He has completed a major in Materials Chemistry with an Analytical Chemistry minor. He works in the research labs of Professor Jeffrey Zaleski who specializes in Enediyne Chemistry and Bergman Cyclization reactions. For his thesis, he has received training in Microbiology from our collaborators Dr. Feng Guo (Intelligent Systems Engineering, IU) and Dr. Joel Ybe (School of Public Health, IU).

At Indiana University Chemistry, he have had the opportunity to teach several undergraduate classes as an Associate Instructor, including C-103 Lab, C- 103 Discussion, C-127 Lab, C-127 Discussion, C118 Lab and P364 Discussion. During the course of graduate studies he has specialized in several analytical techniques including UV-Vis spectroscopy, Zeta Potential, FTIR, Mass Spec, Raman Spectroscopy, TEM, SEM, STM, Flowcytometry and Fluorescence microscopy.