Gasotransmitters and Fine Bubbles: Emerging Strategies for Controlled Gas Delivery and Cell Culture Applications

Gasotransmitters, such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S) are endogenous gaseous mediators with diverse biological activities. However, owing to their high diffusibility and short action range, locality, persistence, and dose control are critical challenges for exogenous application in vitro and in vivo. Fine bubble technology offers a potential solution by enabling gas handling and delivery in liquid environments. According to ISO 20480-1, fine bubbles are classified as microbubbles (≥1 μm) and ultrafine bubbles (UFB; <1 μm). UFBs can remain stable in liquids, supporting their role as gas carriers in cell culture. Fine bubble-based studies indicate that different encapsulated gases can modulate cellular responses, including hypoxia-related radioresistance control, fibroblast growth regulation, and antimicrobial effects. Recent reports have further expanded bubble-based strategies for gasotransmitters, including ultrasound-controlled microbubble/nanobubble delivery systems for NO and H₂S as well as ultrasound-sensitive CO microbubbles. Further, bulk CO-UFB dispersed in culture medium represents a distinct approach for direct cell culture use, including embryo culture improvement. However, standardization and safety evaluation remain essential for implementation.