Preparation of molecularly imprinted nanoparticle-based surface plasmon resonance (SPR) sensors for angiotensin-II detection from human serum

Angiotensin II (AgII) is a short-chain peptide involved in the functioning of the renin-angiotensin-aldosterone (RAAS) system. It is actively involved in controlling many physiological activities within the human body. It acts as a powerful vasoconstrictor. It also contributes to the maintenance of fluid-electrolyte balance. The importance of AgII is not limited to its physiological regulatory functions; it is also evaluated as a biomarker in various cardiovascular and metabolic diseases. In clinical conditions such as hypertension, heart failure and chronic kidney disease, the observation of increased AgII levels in plasma or urine provides important clues about the underlying physiological processes of these diseases. In this context, measuring AgII levels provides valuable information for diagnosing these diseases in the early stages and monitoring the course of the disease. This study aims to develop molecularly imprinted nanoparticle-based surface plasmon resonance (SPR) sensors for the detection of AgII from human serum. To achieve this, AgII-imprinted (AgII-MIP) and non-imprinted nanoparticles (NIP) were synthesized using the molecular imprinting method. The synthesized nanoparticles underwent detailed analysis through Zeta-size measurements, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and FTIR spectroscopy techniques. According to the data obtained from Zeta-size measurements, the particle sizes of AgII-MIP and NIP nanoparticles were determined as 46.51 nm and 48.97 nm, respectively. The nanoparticles were then used to coat the surface of the SPR chip. Thus, SPR chips coated with AgII-MIP nanoparticles (AgII-MICspr) and NIP nanoparticles (NICspr) were successfully obtained. Characterization studies of the chips were carried out by Contact Angle and Atomic Force Microscopy. AgII solutions were made at a range of concentrations (3-100 pg/mL) and these solutions were interacted with the AgII-MICspr chip. The AgII-MICspr chip showed sensitive detection ability even for very low AgII concentration (3 pg/mL). In addition, selectivity studies were performed using AgII-MICspr and NICspr chips. Here, Angiotensin I (AgI) and vasopressin (Vp) were used as competitors. It was determined that the selectivity of the AgII-MICspr chip against AgII was 4.75 and 5.43 times higher than AgI and Vp molecules, respectively. Reusability studies were performed using the AgII-MICspr chip and it was observed that the chip preserved its functionality in the binding regions even after 10 repetitions. AgII detection studies were conducted from human serum. The chip was able to selectively detect very low concentrations of AgII even in this complex environment.