Recent Advancements in Ultrasound Contrast Agents Based on Nanomaterials for Imaging.

Ultrasound (US) is a type of mechanical wave that is capable of transmitting energy through biological tissues. By utilization of various frequencies and intensities, it can elicit specific biological effects. US imaging (USI) technology has been continuously developed with the advantages of safety and the absence of radiation. The advancement of nanotechnology has led to the utilization of various nanomaterials composed of both organic and inorganic compounds as ultrasound contrast agents (UCAs). These UCAs enhance USI, enabling real-time monitoring, diagnosis, and treatment of diseases, thereby facilitating the widespread adoption of UCAs in precision medicine. In this review, we introduce various UCAs based on nanomaterials for USI. Their principles can be roughly divided into the following categories: carrying and transporting gases, endogenous gas production, and the structural characteristics of the nanomaterial itself. Furthermore, the synergistic benefits of US in conjunction with various imaging modalities and their combined application in disease monitoring and diagnosis are introduced. In addition, the challenges and prospects for the development of UCAs are also discussed.