Nanophotonics in Molecular Imaging and Biomedicine: Diagnostics, Therapies, and Translational Challenges

Nanophotonics-the manipulation of light at the nanometer scale within biological systems-is transforming molecular imaging and photobiology, enabling advanced in vivo imaging, diagnostics, and therapy guidance. This review outlines core nanophotonic principles, including surface plasmon resonance, optical confinement, and photon-matter interactions, underpinning emerging molecular imaging probes and diagnostic tools. Biocompatible nanomaterials such as quantum dots, gold nanoparticles, and photonic metamaterials enable highly sensitive, selective imaging and biosensing for early, minimally invasive disease detection and monitoring. Targeted photothermal and photodynamic therapies using near-infrared (NIR) and NIR-II light advance image-guided interventions, allowing deeper tissue penetration with minimal collateral damage. We also discuss the integration of nanophotonic components into lab-on-a-chip and microfluidic platforms for point-of-care diagnostics, accelerating clinical translation. Additionally, machine learning enhances molecular imaging analysis and probe optimization, enabling real-time data interpretation and predictive modeling tailored to patient-specific profiles. This article is a narrative review that emphasizes recent advancements from 2021-2025, identified through targeted database searches, highlighting progress, research gaps, and future perspectives for disease-specific applications. While these advances hold promise, challenges remain in biocompatibility, light penetration, scalability, and regulatory approval. Collectively, integrating nanophotonics with molecular imaging, machine learning, and personalized medicine frameworks marks a step toward next-generation precision diagnostics and image-guided therapeutics.