From Nanowerk: "Proteins are the most important molecules inside our body. There are thousands of [types of] proteins in a single cell alone and they control our physiological reactions, metabolism, cellular information flow, defense mechanisms - pretty much everything. No wonder then that most human diseases are related to the malfunctioning of particular proteins. In contrast to gene therapy - where a gene is placed inside a cell to either replace a defective gene or to increase the amount of a specific gene in order to produce a higher amount of a desired protein - protein therapy works by directly delivering well-defined and precisely structured proteins into the cell to replace the dysfunctional protein. This approach avoids the difficulties and potential problems of gene therapy and is generally considered the most direct and safe approach for treating disease. The problem with protein therapy, which limits its practical use in medicine, is the mode of delivery. Administration of proteins via oral, intravenous, intra-arterial, or intramuscular routes show low delivery efficiency and often the therapeutic protein is metabolized or cleared before it can enter the target tissue. A team of scientists at UCLA has now demonstrated a general, effective, low-toxicity intracellular protein delivery system based on single-protein nanocapsules. This work opens a new direction not only for protein therapy but also for cellular imaging, tumor tracking, cosmetics and many other applications."