Fluid-fluid and fluid-solid interfaces of biological origin, commonly referred to as biointerfaces, play a vital role in drug development. From the skin to the epithelial lining in the lungs and gut to the blood-brain barrier, in vivo biointerfaces act as important therapeutic targets as well as challenging barriers for efficient delivery of drugs. Further, with the explosion of biologics such as monoclonal antibodies, biointerfaces are also prevalent in various steps of drug manufacturing such as in bioreactors and play a key role in determining drug stability and efficacy. A thorough understanding of biointerfaces is thus indispensable for modern drug discovery and delivery. This Methods Collection describes a set of important experimental advances that are revolutionizing our understanding of biointerfaces including developments in visualization, measurement of transport properties, and evaluation of rheological characteristics.

The scope of this special issue includes but is not limited to the following concepts:

1. Developments in experimental and computational platforms that can study the fundamental mechanics of biological interfaces in health and disease with an emphasis on techniques that can inform drug development.
2. Experimental advances in characterizing the interfacial physics including the rheology, adhesion, and stability of biologics such as monoclonal antibodies at fluid-fluid and fluid-solid interfaces.
3. Experimental methods for characterizing transport of biologics across biointerfaces including measurement of chemical species transport and electrical activity.
4. Advances in experimental techniques for biointerface visualization with an emphasis on techniques that can aid in the development of theranostics.