A Luminescent PEI/Cy5‐Citrate‐Functionalized Carbonated Apatite Nanoplatform for In Vitro Gene Delivery and In Vivo Traceability

ABSTRACT The development of multifunctional nanoplatforms that enable efficient gene delivery and real‐time traceability remains a critical challenge in nanomedicine. Hydroxyapatite‐based nanoparticles (HAPs), owing to their intrinsic biocompatibility and tunable surface chemistry, represent attractive building blocks for integrated systems. Here, we report a multifunctional core–shell nanoplatform based on mature citrate‐coated carbonated HAP nanoparticles (Cit‐CO 3 HAP), engineered through sequential surface functionalization with Cyanine 5 (Cy5) and polyethyleneimine (PEI) to combine in vitro gene delivery with nanocarrier traceability. Plasmid DNA is efficiently loaded via isothermal adsorption onto the engineered nanocarriers, enabling stable complex formation. Confocal microscopy and flow cytometry analyses indicate efficient cellular internalization and sustained transgene expression in breast and cervical cancer cell models. Comprehensive cytocompatibility studies in both cancerous and non‐cancerous cell models confirm high cell viability, highlighting the favorable biological profile of the system. In vivo experiments with Cy5/Cit‐CO 3 HAP nanoparticles further demonstrate longitudinal traceability, prolonged intratumoral retention, and a progressive decrease in detectable Cy5‐associated fluorescence over time, with no persistent fluorescence accumulation in major organs at the evaluated time points. Collectively, these findings establish PEI/Cy5/Cit‐CO 3 HAP nanoparticles as a versatile and biocompatible luminescent nanoplatform for traceable gene delivery, and provide a modular strategy for next‐generation gene‐delivery and bioimaging applications.