A Surface-Driven Polyelectrolyte Reaction Network capable of Signal Modulation

Biochemical communication is ubiquitous in life. The efficient means by which biology use feedback mechanisms to dynamically regulate concentrations myriad signaling molecules have inspired chemists to design chemical reaction networks (CRNs). Strategies to encode, transmit, and process information in CRNs, however, is still in its infancy. Here, we designed a microfluidic flow setup wherein a polyelectrolyte reaction network is maintained under out-of-equilibrium conditions using pH gradients. The network, comprises two weakly charged polyelectrolytes (polyallylamine, PAH, and polyacrylic acid, PAA) in solution and one immobilized on the surface (poly-L-lysine, PLL). We chose PAH and PAA as their complexation process is known to be history dependent (i.e., the preceding state of the system can determine the next state). Surprisingly, we found that the hysteresis diminished as the PLL-coated surface supported rather than perturbed the formation of the PAH-PAA complex. The role of the surface is further exploited to demonstrate that the network can enable event-driven processing. Overall, this work established that reversible switching between the assembled and disassembled state of polyelectrolytes can exploited to modulate signals encoded in the frequency and duration of pH pulses. We envision that the strategy employed to process information in this polyelectrolyte reaction network could open novel routes to modulate signals of many other biologically relevant reactions.