Engineering Ultrasound Contrast Agents for Targeted Therapeutics: A Theranostic Approach to Drug Delivery, Gene Therapy, and Immunomodulation

Engineering of ultrasound contrast agents (UCAs) has revolutionized diagnostic imaging and therapeutic applications in medical science. These agents, comprising microbubbles (MBs) and nanobubbles (NBs), are gas‐filled structures with unique acoustic properties that not only enhance ultrasound imaging quality but also enable targeted therapeutic delivery through controlled acoustic stimulation. While available microbubble‐based UCAs have demonstrated significant success in clinical imaging and drug delivery, their size (1–8 μm) restricts application to the vascular compartment. This limitation has driven the development of NBs (100–500 nm), which exploit enhanced permeability and retention effects to penetrate tumor tissues and other pathological sites. Recent advances in UCA engineering have focused on optimizing shell composition, surface modifications, and payload incorporation to create sophisticated theranostic platforms. These developments have expanded UCA applications beyond traditional imaging to include targeted drug delivery, gene therapy, and immunomodulation. This review critically examines the engineering principles and structural parameters governing UCA performance in diagnostic and therapeutic applications, emphasizing emerging strategies for enhanced therapeutic delivery. It explores how innovations in shell design, size control, and surface modification enable more effective therapeutic interventions while maintaining excellent imaging capabilities, paving the way for next‐generation theranostic applications in medicalscience.