Synthesis of (poly)gallic acid in a bacterial growth medium

Bioelectronics requires versatile, efficient, and low-cost interfaces between the biological entities and the conductive unit. Conductive polymers represent a valid choice to assemble such interfaces able to extract or impinge charges between the biological units and the conductive electronic systems. A drawback in the use of such systems is that the polymerization reaction often takes place in environments whose chemical and physical characteristics clash with the mild conditions required for living biological systems. In the present work, we successfully prove that the conductive polymer poly(gallic acid) can be synthesized in medium designed for bacterial growth, characterised by the presence of several adverse conditions including numerous chemicals, high ionic strength, and almost neutral pH. The gallic acid successfully polymerizes within few hours and with a 40% yield, by exploiting the catalytic activity of the enzyme laccase from the polypore mushroom Trametes versicolor. The resulting polymer is characterised by absorption and Nuclear Magnetic Resonance spectroscopies. The viability of Rhodobacter sphaeroides culture, assessed via the coffee-ring technique, shows an important, but not complete detrimental effect of the gallic acid on the bacterial growth.