| Abstract [eng] |
Mindaugas Dzvinko's Integrated Master's Thesis. Thesis supervisor: Assoc. Prof. Dr. Nora Šlekienė. Centre of Pharmacy and Pharmacology, Institute of Biomedical Sciences, Faculty of Medicine, Vilnius University. Thesis topic: Investigation of Antidepressant Binding to Biomembranes Using Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). Relevance of the topic: Drug interactions with serum albumin directly determine their pharmacokinetic properties and therapeutic efficacy; however, these interactions remain poorly studied for antidepressants. The real-time QCM-D method enables precise evaluation of molecular interaction kinetics, making it a valuable tool for addressing this gap in knowledge. Research aim: To investigate the interactions of fluoxetine, venlafaxine, and mirtazapine with bovine serum albumin using the quartz crystal microbalance with dissipation monitoring (QCM-D) method. Research objectives: 1. To investigate the interaction of fluoxetine with bovine serum albumin by determining binding kinetics. 2. To investigate the interaction of venlafaxine with bovine serum albumin by determining binding kinetics. 3. To investigate the interaction of mirtazapine with bovine serum albumin by determining binding kinetics. 4. To compare the interaction characteristics of fluoxetine, venlafaxine, and mirtazapine based on the results of QCM-D analysis. Research methods: An experimental study was conducted in which the binding kinetics of three antidepressants (fluoxetine, venlafaxine, and mirtazapine) with bovine serum albumin (BSA) were investigated using the quartz crystal microbalance with dissipation monitoring (QCM-D) method. BSA was immobilized on a gold sensor surface via the active groups of 11-mercaptoundecanoic acid. The interaction of the antidepressants with BSA was evaluated using solutions at concentrations of 0.1, 1, 10, and 100 µM, with frequency and dissipation changes recorded in real time. Research results: QCM-D analysis demonstrated that all three antidepressants studied (fluoxetine, venlafaxine, and mirtazapine) interact with immobilized BSA. The most prominent were dissipation (ΔD) changes (frequency changes were too small for analysis), and therefore kinetic parameter analysis was performed based on ΔD data. Due to weak signals at lower concentrations, further studies were conducted using 100 µM antidepressant solutions. Fluoxetine associated rapidly (k_a = 8.52×10² M⁻¹s⁻¹) and dissociated slowly (kd = 9.97×10⁻⁵ s⁻¹, K_D = 1.17×10⁻⁷ M). Venlafaxine associated most slowly (ka = 7.33×10¹ M⁻¹s⁻¹) but formed an exceptionally stable complex (kd = 7.40×10⁻⁶ s⁻¹, K_D = 1.01×10⁻⁷ M). Mirtazapine associated rapidly (ka = 7.53×10² M⁻¹s⁻¹) but dissociated most quickly (kd = 8.58×10⁻⁴ s⁻¹, K_D = 1.14×10⁻⁶ M). The interaction of all drugs with BSA was spontaneous (ΔG: fluoxetine −38.9, venlafaxine −39.3, mirtazapine −33.4 kJ/mol). Conclusions: 1. Fluoxetine exhibits a high association rate and a low dissociation rate constant, forming a stable complex with BSA (K_D = 1.17×10⁻⁷ M). 2. Venlafaxine associates most slowly but has the lowest dissociation rate constant, forming an exceptionally stable complex (K_D = 1.01×10⁻⁷ M). 3. Mirtazapine associates rapidly but dissociates most quickly, forming the least stable complex (K_D = 1.14×10⁻⁶ M). 4. Fluoxetine and venlafaxine display similar affinity for albumin (K_D ~10⁻⁷ M) but differ in their kinetics. Mirtazapine stands out for its rapid dissociation and lowest affinity (K_D ~10⁻⁶ M). The interaction of all three drugs with BSA is spontaneous (ΔG < 0), and the Gibbs energy values of fluoxetine and venlafaxine (−38.9 and −39.3 kJ/mol) are greater in magnitude than that of mirtazapine (−33.4 kJ/mol). |
