Surface-engineered nanoprobes for multimodal bioimaging: from molecular design to theranostic integration

Bioimaging technologies are indispensable for deciphering cellular dynamics, disease mechanisms, and therapeutic responses. However, conventional agents are limited by photobleaching, poor tissue penetration, and nonspecific distribution. These shortcomings hinder real-time visualization of deep tissues and complex pathologies. Surface-engineered nanoprobes have revolutionized bioimaging and theranostics by addressing these limitations. This review systematically explores the molecular design principles and biomedical applications of these advanced nanoprobes. We highlight several major surface engineering strategies (ligand-mediated targeting, environmental responsiveness, charge engineering, surface coating and core-shell structure) and their applications to high-resolution, dynamic and real-time, multimodal imaging. Finally, we outline future perspectives for surface-engineered nanoprobes, emphasizing critical challenges in clinical translation. These insights provide foundational guidance for advancing next-generation nanotheranostic platforms with enhanced clinical relevance and functional sophistication.