Development of an Electrochemical Nanobiosensor for Isolation and Detection of Cancerous Exosomes Containing PSMA and CD63 Antigens in Urine for Prostate Cancer Diagnosis

Cancer is a disease that results from the abnormal proliferation and growth of cells. It begins when mutations occur in the genes that regulate cell growth. Under normal conditions, if a cell undergoes an irreparable mutation, it will self-destruct; however, if it cannot eliminate itself, these cells or their progeny may divide uncontrollably with incorrect genetic information. Cancerous cells form tumors, leading to numerous alterations in biochemical processes, gene expression patterns, and disrupting the balance between cell proliferation and death. Studies have shown that cancer is the second leading cause of human mortality worldwide. Despite significant advancements in modern medical science over the past century, the etiological and pathogenic aspects of the disease remain largely unknown, and there is often no definitive cure. Therefore, the development of effective, biocompatible, and cost-effective methods for cancer treatment is essential.

Biosensors are a subset of chemical sensors. A biosensor is a device in which a biologically active layer is immobilized on a transducer as the sensing element. The biological component in a biosensor is highly selective for interacting with the analyte (the substance to be measured) and detecting it. The physical transducer converts these biological interactions into a measurable effect, such as an electrical signal, light emission, or mechanical movement. Among these, electrochemical biosensors have gained significant attention in recent decades due to their unique features. These sensors, which can measure target species at very low concentrations and offer specific responses, may serve as an excellent alternative to clinical measurements for detecting cancer at its early stages. Among the growing field of electrochemical biosensors, those based on immobilizing biological agents such as DNA, RNA, and antibodies on electrode surfaces are particularly noteworthy.

DNA biosensors are based on single-stranded DNA immobilized on a substrate, designed to detect a key biological species. Various methods can be employed for detecting the analyte, including optical, mass, and electrochemical sensor-based approaches. Among these methods, electrochemical techniques are widely used due to their simplicity, low cost, high selectivity, and miniaturization potential. Therefore, electrochemical DNA-based biosensors hold promise for the rapid and cost-effective detection of genetic diseases and pathogenic biological species. The performance of a biosensor is typically evaluated based on sensitivity, selectivity, reproducibility, stability, detection limit, and response time. Improving these factors can make biosensors a superior option compared to other diagnostic methods due to their lower cost, small-scale production, and ease of use. This research will investigate the impact of nanomaterials on the performance of biosensors through electrochemical methods such as cyclic voltammetry and electrochemical impedance spectroscopy.

Prostate cancer (PCa) is a leading cause of cancer-related deaths in men and is the most commonly diagnosed cancer in 112 countries worldwide. The prostate-specific antigen (PSA) biomarker, originating from prostate epithelial cells, is widely used in serum tests for early detection of PCa, contributing to a reduction in prostate cancer-related mortality. However, the low sensitivity and nonspecific nature of the PSA test has led to overdiagnosis or misdiagnosis in some cases. Specifically, elevated PSA levels in serum can be associated with non-malignant conditions like benign prostatic hyperplasia (BPH), which often presents similar symptoms to PCa. In such cases, conventional PSA testing has a low diagnostic sensitivity of 58.3%, particularly in the diagnostic gray zone for early-stage PCa, where it cannot effectively differentiate between PCa and BPH, requiring a prostate biopsy for definitive diagnosis.

Another biomarker for prostate cancer diagnosis is the prostate-specific membrane antigen (PSMA), which is highly expressed in the prostate, approximately 100 times more than in other tissues. In certain prostate cancers, PSMA is the second most highly upregulated gene product, with an 8 to 12-fold increase over levels seen in non-cancerous prostate cells. Due to this high expression, PSMA is being developed as a potential biomarker for the treatment and imaging of various cancers. In prostate cancer, tumors with higher PSMA expression are associated with faster progression and a higher percentage of patients suffering from relapse. Laboratory studies using prostate cancer cell lines with reduced PSMA levels have shown a significant decrease in cell proliferation, migration, invasion, adhesion, and survival.