Abstract
AbstractAntibodies play an essential role in modern medicine for diagnostic and therapeutic applications. Even though the production of antibodies is the fastest growing pharmaceutical industry area, the cost of antibodies remains high, which limits access to antibody‐based medicine both in developing and developed countries. The bottleneck and major cost factor in the production is purification of the antibody. Here, a proof‐of‐concept is presented for antibody extraction using ferrofluid microdroplets. An external magnetic field splits oil‐based ferrofluid droplets into an array of daughter microdroplets, which serve as a magnetically tunable, hydrophobic, liquid substrate with a relatively large surface area. A fusion protein (HFBI‐Protein A), added to the solution surrounding the magnetic droplets, adsorbs strongly at the liquid‐liquid interface by the hydrophobin HFBI moiety, creating a bifunctional monolayer that can catch antibody molecules. After adsorption at the liquid‐liquid interface, these antibody molecules can be released by decreasing the pH of the solution. The antibody extraction process is investigated using confocal microscopy and gel electrophoresis. In addition, the effect of HFBI on the field‐induced ferrofluid droplet splitting is examined. This study provides a proof of concept for utilizing liquid‐liquid instead of a solid‐liquid system in antibody handling.
Highlights
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This instability is governed by the critical wavelength λc, which depends on the magnetic field H and its gradient, the magnetization of the ferrofluid M and the interfacial tension σ between the ferrofluid and the phosphate-buffered saline (PBS) solution:[25]
A new approach for extracting antibody molecules using a complex functional layer at the liquid-liquid interface instead of the commonly used solid-liquid interface was investigated. This approach combines the unique properties of two synthetic functional materials: the ability of ferrofluid to create a relatively large liquid surface area due to the external magnetic field, and the self-assembly and antibody catching of the fusion protein
Summary
Ferrofluids are colloidal suspensions of superparamagnetic nanoparticles in a carrier liquid, which can be magnetically actuated and deformed due to their strong response to magnetic fields.[23]. The ferrofluid droplets continued to split faster in a constant magnetic field compared to the experiments done in pure PBS, due to adsorption of HFBI-Protein A at the ferrofluid interface. The system was left to rest for approximately 60 min to give the fusion protein enough time to catch antibody molecules, forming a HFBI-Protein A-IgG complex at the liquid-liquid interface. In this step, another sample was taken before the washing step and changing the disposable wall. To ensure that the container walls nor the bare surface of ferrofluid droplets did not contribute to antibody adsorption, control experiments were performed without the fusion protein These showed no antibodies in the extraction step (Figure 4a). The complex molecules (HFBI-ProteinA-IgG) could leave the interface during the washing steps
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