Development of an electrochemical cyclooxygenase biosensor to evaluate target–drug viability and interactions

In this research, we developed a biosensor to analyze the anti-inflammatory properties of non-steroidal anti-inflammatory drugs (NSAIDs) and potential candidate molecules. The chemical interaction between commercial NSAIDs and their target, the cyclooxygenase-2 enzyme (COX), was studied using electrochemical techniques and electronic paramagnetic resonance (EPR). The modified electrode, COX@GCE biosensor, presented two main reduction processes. We observed that the first one involves one electron and one proton related to tyrosyl radical reduction to tyrosine, and the second comprises a one-electron reduction from the Fe (IV) to Fe (III) species present in the enzyme’s active site, which in the presence of hydrogen peroxide results in a catalytical process. Based on these results, an electrochemical mechanism of the COX enzyme is proposed. Additionally, the quantitative inhibitory interaction mechanisms of six commercial NSAIDs were studied using this biosensor. The NSAIDs acetylsalicylic acid, dipyrone, and ibuprofen presented the higher COX inhibitory percentual, being, therefore, the most effective NSAIDs among the studied group. Salicylic acid also presented a significant inhibition capability in both electrochemical and EPR studies. The effect of some NSAIDs, e.g., dipyrone and acetaminophen, can be explained by the redox inhibition hypothesis and can be related to the direct interaction and inactivation of the iron present in the enzyme’s active site. Ibuprofen and naproxen presented irreversible COX inhibition. Despite that, the EPR shows that these drugs have relatively weak interactions with the COX active site, suggesting they should interact with the external structures resulting in the inhibition of its activity. Finally, the developed enzymatic sensor presented a high potential to study the anti-inflammatory properties of well-known drugs and can be a useful tool in the development of new NSAIDs, in a more efficient way, therefore presenting high applicability in drug development, pharmaceutical, and biomedical applications in both academia and industry.