Mechanistic study of the adsorption of Iodinated Contrast Media agents on monolayer Graphene surface

Iodinated Contrast Media agents (ICMs), essential in diagnostic imaging, have seen a surge in usage within the healthcare sector. This rise has sparked significant environmental concerns, primarily due to the fact that ICMs can evade capture by standard wastewater treatment facilities, subsequently accumulating in environmental waters [1]. This situation underscores the urgent necessity to develop more sustainable and effective methods for the removal and recovery of ICMs from aquatic systems. Over the past ten years, the scientific community has been actively exploring various materials that could serve as potential adsorbents to extract ICMs from natural waters [2]. Although practical experiments have demonstrated the effectiveness of different adsorbents in removing ICMs, there is a pressing need for a detailed mechanistic understanding of the adsorption process. In response to this need, our research delves into the mechanistic adsorption behaviour of ICMs using a model of activated carbon, represented by a monolayer graphene surface. By focusing on the interactions at the molecular level, we aim to advance the predictive modelling of ICM adsorption and contribute to the development of more targeted and efficient removal strategies for these pervasive substances in our water systems. We utilized molecular docking and Density Functional Theory (DFT) simulations to scrutinize the adsorption process on a molecular level [3]. Additionally, we applied Quantitative Structure-Activity Relationship (QSAR) modelling to link molecular characteristics with adsorption energy, aiding in understanding the influential factors in the adsorption process and building a predictive model [4]. We developed a variety of QSAR models through the combination of Multiple Linear Regression and genetic algorithm. To evaluate and prioritize these models, our study employs Maximum Likelihood estimation alongside established evaluative criteria. These criteria aid in determining the probability for model accuracy of each model, thereby refining the QSAR methodologies. Based on our results for 24 ICMs involved in this study we observed the varying adsorption energies from -4.40 Kcal/mol (Methiodal) to -40.35 Kcal/mol (Iobitiridol) suggesting a selective adsorption of ICMs. We observed that van der Waals interactions such as π-π stacking to be the primary mechanism of adsorption. Our DFT results also highlighted a significant correlation between adsorption energy and the Molecular weight of the ICMs. Furthermore, based on our final QSAR model, we observed that structural properties such as molecular complexity, presence/absence of Iodine atoms and molecular complexity play a strong role in the adsorption of ICMs on the adsorbent.

References:

1. Sengar, A., Vijayanandan, A., 2021. Comprehensive review on iodinated X-ray contrast media: Complete fate, occurrence, and formation of disinfection byproducts. Science of the total environment 769, 144846.

2. Dekker, H.M., Stroomberg, G.J., Prokop, M., 2022. Tackling the increasing contamination of the water supply by iodinated contrast media. Insights into Imaging 13, 30.

3. Orio, M., Pantazis, D.A., Neese, F., 2009. Density functional theory. Photosynthesis research 102, 443–453.

4. Roy, K., 2017. Advances in QSAR modeling. Applications in Pharmaceutical, Chemical, Food, Agricultural and Environmental Sciences; Springer: Cham, Switzerland 555, 39.