Conjugation of polyethylene glycol to ferritin nanocage
Shuhaida Mohamed Salleh
Date of Issue2015
School of Chemical and Biomedical Engineering
Research has shown that protein cages have potential applications such as drug delivery vehicle and MRI contrast agents. However, their application is hampered by their immunogenicity. In this project, a polymer is conjugated to the protein cage to reduce immunogenic response. Archaeoglobus fulgidus ferritin mutant (AfFtn-AA) with 24 subunits that self-assemble to protein cage in the presence of iron ions was used. The amino acid glutamic acid at site 94 was substituted with cysteine residue, providing a thiol group at each subunit. The protein cage was then conjugated to polyethylene glycol (PEG) molecules of molecular weights 2, 5 and 10 kDa and a 4-arm PEG of molecular weight 20 kDa. Two conditions were tested to optimize the conjugation reaction and the modified protein cage was characterized by dynamic light scattering (DLS), matrix assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry and transmission electron microscopy (TEM). The conjugation reaction with different sizes of PEG molecules led to a shift in peaks in the DLS and MALDI TOF analysis gave the profile of each protein-polymer conjugate. The conjugation of the protein cage to PEG implies that the protocol is effective and can be used as a platform for future work as carrier for drug delivery.