Self-Assembly of Drug-Loaded Liposomes on Genetically Engineered Target-Recognizing M13 Phage: A Novel Nanocarrier for Targeted Drug Delivery

Liposomes have been a center of research for many years due to their numerous applications in chemistry, biology, medicine, and nanotechnology. They can be used to entrap materials such as drugs either within the central aqueous compartment if they are water soluble, or within the hydrophobic domain of the lipid bilayer if they are oil soluble. In addition, their surface can bemodified to realize targeted delivery. For example, in biomedicine, liposomes are used as vehicles to deliver drugs and genes to specific parts of the body. When used in the delivery of certain anticancer drugs, liposomes help to shield healthy cells from the drug toxicity and prevent concentration in vulnerable tissues. In addition, the liposomes allowmuch smaller doses of drug to be used, thus reducing the side effects of that drug. On the other hand, zinc phthalocyanine (ZnPc) is a potential drug that is being tested as a photosensitizer for photodynamic therapy (PDT). PDT involves the systemic administration of a photosensitizer followed by illumination with light of an appropriate wavelength, which results in the formation of singlet oxygen (O2) for destroying cancer cells. [6] ZnPc has a high absorption coefficient at 650–700 nm with optimal tissue penetration. It has a long lifetime in the triplet excited state, thus resulting in the highly efficient production of O2 which is the main cytotoxic species in PDT. However, it is insoluble in water and must be incorporated into unilamellar liposomes (Figure 1a). The main drawback of liposomes is their instability in biological media, as well as their sensitivity to many external parameters, such as temperature or osmotic pressure. This instability problem affects the application of liposomes in drug/gene delivery and PDT. Attempts have been made to stabilize liposomes by adsorbing some