Closed, lipid bilayer spheres that encapsulate ingredients, target their delivery to specific tissues, and control their release are called:

Liposomes are closed, lipid bilayer spheres specifically designed to encapsulate and deliver various ingredients to targeted tissues while controlling their release. Due to their unique structure, liposomes can effectively fuse with cell membranes, allowing for the efficient delivery of therapeutic agents or cosmetic ingredients directly into cells. This property makes them particularly useful in the field of esthetics for enhancing the efficacy of active ingredients, such as vitamins and antioxidants, by overcoming barriers to absorption.

In contrast, other options may have overlapping characteristics but do not precisely fit the description provided in the question. Microspheres, for instance, refer to small spherical particles that can contain drugs or other materials but do not inherently possess a lipid bilayer structure for targeted delivery like liposomes. Vesicles are broader in definition and may include various types of membrane-bound structures, lacking the specific targeting characteristics of liposomes. Nanoparticles, while they may also be utilized for drug delivery, often differ in size scale and material composition compared to liposomes and are not exclusively lipid-based.

Understanding the specific functions and structural characteristics of liposomes is crucial for estheticians who want to utilize advanced delivery systems in their treatments and products.