A gold nanoparticle and aptamer-based theranostic probe for fluorescence detection and photothermal therapy of HeLa cells

Background ntegrating diagnosis and therapy into a single nanoprobe remains challenging for small gold nanoparticles (AuNPs), which offer excellent tumor delivery but limited photothermal performance. This study aimed to develop a theranostic probe that reconciles these two functions. Methods A theranostic probe (SGC@AuNPs) was assembled by adsorbing FAM-labeled SGC8C aptamer onto 13 nm AuNPs. Upon target recognition, the aptamer desorbs from the AuNP surface, simultaneously restoring fluorescence via relief of nano-surface energy transfer (NSET) quenching and triggering aggregation that enhances near-infrared photothermal conversion. A complementary strand (CS) served as a proof-of-concept model to characterize aggregation and photothermal conversion efficiency ( η ), and the system was further validated with purified PTK7 protein and cellular assays in PTK7-overexpressing HeLa cells versus HEK293 controls. Results Target-induced aggregation increased the hydrodynamic diameter to 343.58 nm and elevated η from 14.7% to 66.6% (Δ T = 10.5 °C, 808 nm, 1.0 W/cm²). Validation with purified PTK7 protein confirmed an η of 59.3% with stable cycling. At the cellular level, SGC@AuNPs selectively labeled PTK7-overexpressing HeLa cells (13.29-fold brighter than HEK293) and, under 808 nm irradiation, reduced HeLa viability to 48.1% while sparing HEK293 cells (98.0%). Conclusions This aggregation-enhanced strategy reconciles delivery efficiency with photothermal performance, offering a generalizable framework for smart tumor theranostic nanoplatforms.