Lenka Zajickova1,2,Lucie Janu1,Vinicius Santana1,Martina Buchtelová1,Beata Beliancinova1,Eva Dvorakova1,David Necas1,Nada Souawda1,Matus Sedivy1,Petr Neugebauer1
Ceitec But1,Masaryk University2
Lenka Zajickova1,2,Lucie Janu1,Vinicius Santana1,Martina Buchtelová1,Beata Beliancinova1,Eva Dvorakova1,David Necas1,Nada Souawda1,Matus Sedivy1,Petr Neugebauer1
Ceitec But1,Masaryk University2
Amino-group-containing plasma polymers (PPs) have been of particular interest for various biomaterials applications because they allow amide covalent coupling and, under certain pH conditions, offer a positively-charged surface for electrostatic binding. Therefore, they were successfully applied to immobilize DNA and various proteins. However, assessing what plasma parameters and the film structural properties are essential for successful and stable immobilization is difficult. PPs do not have a well-defined structure of conventional polymers that can be described as a repetition of a particular unit and the molecular weight of the polymer chain. Since they are deposited from a complex environment of many gaseous reactants created by dissociating original gas feed, their chemical structure cannot be derived only from the starting reactants. We studied the plasma polymerization of cyclopropylamine (CPA) mixed with Ar in three CCP reactor setups and different plasma conditions. The response of immunosensors constructed with the plasma polymerized CPA (PP-CPA) films revealed the surprisingly long reactivity of the film surfaces. It opens the question of whether such phenomena could be explained by the free radicals (species with unpaired spins) trapped in the PP films. Therefore, we investigated the presence and dynamics of the free radicals in the PP-CPA films deposited under mild varied conditions using electron paramagnetic resonance (EPR). We detected a surprisingly high amount of unpaired spin density with the life time in months. Another open question in the performance of amine PPs is the role of primary amine groups (-NH2). In the example of two immunosensors having the same nitrogen and NH2 amount, we demonstrate that amount of NH2 groups detected by TFBA chemical derivatization cannot explain the efficientcy of the antibody covalent coupling and nitrile groups belong to other factors that should be taken into account for the surface reactivity in aqueous media.