Specific binding of immunoglobulin G to protein A-mesoporous silica composites for affinity column chromatography

High-performance affinity column chromatography is considered to be an important analytical tool for further advancements and popularisation of antibody-drug remedies. In this context, there is a great need for the design and development of a new protein A column system with desired functionalities at low cost. Here, we developed mesoporous silica (MPS) with pore diameters in the range of 2.3-31.2 nm, which was synthesised by a sol-gel method using organic templates, as a carrier for staphylococcal protein A. The surface of the MPS was organo-functionalised using γ-glycidoxypropyltrimethoxysilane (Gly), phenyltriethoxysilane (Ph) and 3-mercaptopropyltrimethoxysilane (SH). The specific binding of Immunoglobulin G (IgG) to the prepared protein A-MPS composites has been analysed as a function of pore size and surface properties. MPS composites with a smaller pore size (under 12.7 nm) demonstrate higher IgG binding activity than non-porous carrier composites. Of all the composites, the MPS-2.7-Gly-protein A composite, having mesochannels of size 2.7 nm and covalently bound to protein A, exhibits the highest binding efficiency. The molecular ratio of immobilised protein A to bound IgG is found to be approximately 1 : 1. These results imply that the composite MPS-2.7-Gly-protein A is at least 15 times more efficient than commercial carrier composites such as acrylic polymer-protein A. In addition, this composite shows remarkable stability towards low pH and chaotropic agents. Furthermore, the possibility of reusing the MPS-2.7-Gly-protein A composite is established by cycling it 5 times, with no loss in IgG extraction capacity. We expect that development of such MPS will have a significant impact on the industrial-scale advancement of high-efficiency and low-cost protein A affinity column chromatography.