Design of an Optical Genosensor Based on Gold Nanoparticles for the Diagnosis of Breast Cancer Using miR-122

INTRODUCTION: Early and accurate detection of breast cancer remains a major clinical challenge. In this study, we developed a rapid, optical genosensor based on gold nanoparticles for the detection of miR-122, a microRNA associated with breast cancer. The biosensor design relies on acid-triggered aggregation of functionalized AuNPs, enabling colorimetric detection without amplification. METHODS: The R-122 oligonucleotide probe was designed using bioinformatics software. The designed genosensor was developed based on previously reported patented nanoplasmonic principles, employing gold nanoparticles for amplification-free optical detection of miR-122. Gold nanoparticles were synthesized via the citrate reduction method to obtain a uniform colloidal solution. RESULTS: The optical sensor exhibited a distinct absorption peak at 520 nm. Clinical serum samples containing complementary and non-complementary sequences produced clearly distinguishable color changes upon hybridization, confirming specific detection of the target sequence. Optimal visual discrimination was achieved by mixing 15 μL of nanobiosensor, 5.2 μL of acid, and 10 μL of PBS. DISCUSSION: The results demonstrate that the developed colorimetric AuNP-based genosensor provides an ultra-low detection limit and simple operation, showing promise for rapid clinical screening compared with previously reported SERS and electrochemical assays. CONCLUSION: The proposed AuNP-based colorimetric genosensor enables rapid and specific detection of miR-122 without amplification. Its simplicity, cost-effectiveness, and reliable visual output indicate strong potential for future point-of-care breast cancer diagnostics.