What is a tiny sphere of liquid that can carry drugs through the body called?

A tiny sphere of liquid that can carry drugs through the body is referred to as a liposome. Liposomes are spherical vesicles that are composed of a lipid bilayer, forming a barrier that encloses a central aqueous compartment. This unique structure allows liposomes not only to encapsulate hydrophilic (water-soluble) drugs within their aqueous core but also to carry lipophilic (fat-soluble) drugs within their lipid membrane.

Liposomes are critically important in drug delivery systems because they can mimic cell membranes, enhance the bioavailability of therapeutic agents, and improve their stability in circulation. Their ability to encapsulate various types of drugs makes them versatile carriers in medical applications, particularly in targeted therapy where they can deliver medication directly to diseased cells while minimizing side effects.

As for the other options: micelles are also aggregates of surfactant molecules, but they typically carry hydrophobic substances and are more effective for certain applications rather than extensive drug delivery. Vesicles are a broader category and can include any membrane-bound compartments but do not specifically imply the characteristics of drug delivery like liposomes do. Bubbles, while being spherical in form, do not serve the purpose of drug transport in the body in the same way that liposomes do.