A self-assembling nanoparticle drug delivery system for the delivery of drugs including peptides, proteins, nucleic acids or synthetic chemical drugs is provided. The self-assembling nanoparticle drug delivery system described herein includes viral capsid proteins, such as Hepatitis B Virus core protein, encapsulating the drug, a lipid bi-layer envelope and targeting or facilitating molecules anchored in the lipid bilayer. A method for construction of the self-assembling nanoparticle drug delivery system is also provided.