Green Synthesis of Biocompatible Gold Nanoparticles Using <i>Andrographis paniculata</i> Leaves Extract for Targeted Detection of Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Cells

High Resolution Image Download MS PowerPoint Slide Globally, breast cancer is the second leading cause of cancer-related mortality among women. Early detection, accurate diagnosis, and timely treatment are critical for improving survival rates. Therefore, developing a rapid and highly sensitive diagnostic method for early-stage breast cancer detection is essential. Human epidermal growth factor receptor 2 (HER2) is a well-characterized indicator of aggressiveness and poor prognosis in various cancers, including breast cancer. HER2-positive breast cancer represents about 15–20% of all cases, highlighting the significance of HER2 as both a prognostic and predictive biomarker. Gold nanoparticles (AuNPs) have emerged as promising tools in cancer diagnostics due to their unique optical and physicochemical properties. Among these, green-synthesized AuNPs are particularly attractive for biomedical applications due to their eco-friendliness and biocompatibility. Andrographis paniculata is a medicinal herb traditionally employed in the treatment of several diseases. Its leaf extract (ALE) contains various bioactive compounds, including flavonoids and diterpenoids, known for their strong reducing capabilities suitable for AuNP synthesis. In this study, we synthesized AuNPs using ALE (ALE-AuNPs) through a green, one-pot method. The ALE-AuNPs ranged from 11.12 ± 2.10 to 43.53 ± 10.53 nm in size, with a zeta potential of −21.00 ± 0.89 to −44.60 ± 2.36 mV. Cytotoxicity testing on MCF-7 cells indicated good biocompatibility. For targeted detection, the ALE-AuNPs were further functionalized with polyethylene glycol (PEG) and anti-HER2 antibodies, forming ALE-AuNPs+PEG+anti HER2. This nanoconjugate successfully detected HER2-positive MCF-7 cells via a 3,3′,5,5′-tetramethylbenzidine-based colorimetric assay. To the best of our knowledge, this is the first report of a simple green synthesis of AuNPs from ALE for use as a colorimetric probe in HER2-positive breast cancer detection.