We derived a theory of biomolecule binding to the surface of Au_n clusters and of the Au plane based on the hard soft acid base (HSAB) principle and the free electron metallic surface model. With the use of quantum mechanical calculations, the chemical potential (μ) and the chemical hardness (η) of the biomolecules are estimated. The effect of the gold is introduced via the empirical value of the gold chemical potential (−5.77 eV) as well as by using the expression (modified here) for the chemical hardness (η). The effect of an aqueous environment is introduced by means of the ligand molecular geometry influenced by the PCM field. This theory allows for a fast and low-cost estimation of binding biomolecules to the AuNPs surface. The predicted binding of thiolated genistein and abiraterone to the gold surface is about 20 kcal/mol. The model of the exchange reaction between these biomolecules and citrates on the Au surface corresponds well with the experimental observations for thiolated abiraterone. Moreover, using a model of the place exchange of linear mercaptohydrocarbons on 12-mercaptododecane acid methyl ester bound to the Au surface, the present results reflect the known relation between exchange energy and the size of the reagents.

This study aimed to evaluate the use of electrochemistry to generate the oxidation and reduction products of active pharmaceutical ingredients (APIs) with a hydrazone group, including dantrolene, nitrofurantoin, furazidine, and nitrofural. In the first step, cyclic voltammetry was employed to assess the electroactivity of these compounds. In the second step, the transformation products of selected APIs following electrochemical oxidation and reduction were analyzed using the ROXY EC System equipped with a µ-PrepCell™ 2.0, coupled with a high-resolution Q-TOF mass spectrometer. The identification of transformation products was based on accurate mass, isotopic distribution, and fragmentation pattern. Seventeen API impurities were identified in this study, contributing to insights into drug stability and potential risks associated with their manufacture. Experimental findings were supported by the quantum mechanical DFT calculations of the molecular energies. In addition, using commercially available in silico software, the predicted metabolic products were compared with those obtained by experimental methods. The electrochemical approach proved useful as a test for determining the stability of compounds, the detection of new impurities and structure determination using high-resolution mass spectrometry.