Plasmonic Nanotheranostics: Merging Imaging and Therapy on a Unified Platform for Precision Oncology

Plasmonic nanoplatforms have emerged as a powerful and versatile class of cancer theranostic agents, enabling the seamless integration of diagnostic imaging and therapeutic intervention within a single nanoscale system. By exploiting localized surface plasmon resonance (LSPR), these nanostructures concentrate electromagnetic energy into nanoscale volumes, thereby enhancing optical contrast, improving photothermal conversion efficiency, and enabling plasmon-mediated photochemical processes. This review provides a comprehensive and critical overview of recent advances in plasmonic cancer theranostics, with particular emphasis on the mechanistic foundations, nanostructure design strategies, and system-level integration that enable imaging-guided and feedback-controlled therapy. We discuss how nanoparticle geometry, composition, and surface engineering govern key plasmonic functions, including surface-enhanced Raman scattering (SERS), photoacoustic imaging, computed tomography contrast, and nonlinear optical responses, as well as therapeutic modalities such as photothermal therapy (PTT), photodynamic therapy (PDT), and triggered drug delivery. Special attention is given to synergistic combination therapies—PTT−PDT, PTT−chemotherapy, and plasmonic phototherapy−immunotherapy—in which plasmonic nanoplatforms serve as central integrators that amplify therapeutic efficacy while minimizing systemic toxicity. We further highlight intelligent and tumor-microenvironment-responsive designs that enable real-time monitoring and adaptive treatment within closed-loop theranostic frameworks. Finally, we analyze key translational challenges, including biosafety, biodistribution, scalable manufacturing, regulatory pathways, and clinical integration, and outline emerging opportunities in biodegradable nanoplatforms, AI-assisted design, and personalized oncology. Collectively, this review underscores the transformative potential of plasmonic nanoplatforms to advance precision, image-guided cancer therapy from laboratory innovation toward clinical reality.