Virus like particles (VLPs) are particles that structurally resemble viruses but do not contain any genetic material. They are formed when structural viral proteins spontaneously self-assemble in transfected cells. After VLPs are formed they need to be purified. Since the extract from expressing cells contains not only VLPs but also cellular DNA and proteins, VLPs purification represents a great challenge for the downstream processing.
Adenovirus serotype 3 dodecahedric virus-like particles (Ad3 VLPs) are an efficient vector for the delivery of the anticancer antibiotic drug bleomycin (BLM) – the use of Ad3 VLPs results in over 100 fold improvement of BLM bioavaliability. Ad3 VLPs are formed from penton bases of the adenovirus serotype 3 (Ad3) after these penton bases are expressed in a baculovirus/insect cell system. Ad3 VLPs are approximately 28 nm in size and have a molecular mass of 3.6 MDa. The current purification process of Ad3 VLPs consists of two purification steps, ultracentrifugation with a sucrose gradient (step 1) and ion-exchange chromatography (step 2) on Q-Sepharose and the whole procedure takes 5 days. Since Ad3 VLPs are large biomolecules, monolithic technology was applied for their purification with the aim to speed up the purification process.