Glioblastoma (GBM) is the most common cancer of the brain. GBM is very fast growing and is considered one of the most lethal cancers, with a 5 year survival rate of only 5%. One of the major challenges in treating GBM is finding drugs that can cross the blood brain barrier (BBB), which is composed of very tight junctions in the blood vessel walls of the brain. These tight junctions are so restrictive that they prevent most small molecule drugs from reaching the brain, and 98% of all small molecule drugs are incapable of penetrating this barrier. These inventors have developed a novel strategy to use M13 bacteriophage as a courier to deliver therapeutics and imaging molecules across the BBB.