Spectrophotometric estimation of creatinine using aminoadipic acid functionalized gold nanoparticles

In this work, we describe a highly responsive and selective spectrophotometric technique for measuring creatinine by utilizing gold nanoparticles functionalized with aminoadipic acid (AAA-AuNPs). The synergistic electrostatic interaction and hydrogen bonding between creatinine and the surface functionalized AAA-AuNPs control this sensing mechanism. This aggregation process results in a noticeable red shift of the localized surface plasmon resonance band from 522 nm to 620 nm, as well as a distinct color change from red to blue. Over the range of 1.5-25.0 nM, the absorbance response shows a greater linear association with creatinine concentration under ideal experimental circumstances. When compared to the traditional Jeffs approach, the method has an impressively low limit of detection of 1.49 nM, indicating nearly an order of magnitude increase in sensitivity. The sensing mechanism is further explained by density functional theory calculations, which show that the AAA-Au complex preferentially interacts with creatinine through NAu coordination accompanied by enhanced charge transfer orbital delocalization and reduces the energy gap between the highest and lowest occupied molecular orbitals in strong agreement with the experimental observations. Additionally, the examination of creatinine in artificial urine, human urine, and serum samples using this method produced outstanding results, indicating its potential as a trustworthy tool for clinical diagnostics.