Electrochemical catch-and-release of biomolecules for development of new bioelectronic devices

Examensarbete för masterexamen
Cindric, Filip
Jacobsson Krstovic, Oliver
Purification is a key step when producing pharmaceuticals. A possible alternative to today’s techniques, is by utilising weak polyelectrolyte brushes on an electrode surface. These have been proven successful regarding capture and on-demand release of biomolecules using electrochemistry. However, it has been difficult to achieve this at physiological pH. The reason is the repulsion that occurs between the brushes and the biomolecules. In this study, the brushes used are PAA and are negatively charged at physiological pH. Also, many biomolecules have low isoelectric points, making them negatively charged as well. Two strategies will be evaluated to overcome the issue with capture and release at physiological pH. The first involves the polymer poly(L)lysine (PLL). PLL is cationic at physiological pH and is therefore expected to have an electrostatic attraction to the anionic brushes. Furthermore, it is possible to end-couple PLL in order to conjugate to the biomolecule of interest. The second strategy tests self-manufactured liposomes, where three different lipids will be tested. These are the zwitterionic lipid DPPC and the cationic lipids DOTAP and MVL5. The idea is that the formed cationic liposomes will electrostatically attract to the anionic brushes. The capture and release of PLL was successful. Also, it is proved that lower molecular weight PLL is more suitable for the purpose than higher molecular weight PLL. Applied electrical potentials managed to partly release the PLL but to achieve complete release, a pH 2 solution was injected. At this state, the pH is far below pKa of the brushes and the electrostatic attraction is removed. For the second strategy, immobilisation was more challenging. Different liposome compositions were created, but only one managed to interact with the brushes at physiological pH. Furthermore, the release was incomplete even when different pH solutions were injected. The conclusion is that both of the strategies are worth to consider. However, further development is required to ensure capture and later release with electrochemistry, especially with the second strategy involving liposomes.
polyelectrolyte brushes, electrochemistry, poly(L)lysine, liposomes, electrostatic attraction.
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