Redox polyelectrolyte and enzyme ionic cross-linking nano- and microstructures for bioelectrochemical application

CORIA-ORIUNDO, LUCY L.; GRAMAJO, MARCOS; DANIELE ZAPPI; CORTEZ, M. LORENA; AZZARONI, OMAR; BATTAGLINI, FERNANDO

paris

Congreso; elecnano 9; 2020

Soborne University

Self-assembly systems have been widely used in enzyme immobilization withpolyelectrolytes. Depending on pI of enzyme and pKa of polyelectrolyte, at certain pH bothspecies will have opposite charges and the assembly by electrostatic interactions is formed.1However, this process is limited for enzymes with high pI (pI > 8.5), where for a neutral pHboth species will have positive charge and the assembly will not form. In this work, wepropose one-pot drop casting (OP) and layer-by-layer (LBL) self-assembly systems usingGOx (glucose oxidase, pI=4.2) or HRP (horseradish peroxidase, pI=8.6) with osmiumbipyridine complex bound to polyallylamine (OsPAA) or branched polyethyleneimine(OsBPEI) in the presence of phosphate ions and high ionic strength. The effect of divalentions and high ionic strength on polyelectrolytes and enzymes has been studied by severalauthors2 and includes the Hofmeister series analysis. In systems with GOx at pH 6 or 7, in thepresence of 10 mM phosphate ions and high ionic strength, due a self-assembly by aelectrostatic interactions and ionic cross-linking between phosphate ions and amine groups ofpolyelectrolyte and GOx, the electronic transfer between these, the incorporation of thecomponents and the catalytic response of glucose oxidation improves. On the other hand, insystems with HRP at pH 7, only in the presence of phosphate ions and high ionic strength byionic cross-linking self-assembly is formed, and a good performance of hydrogen peroxidereduction catalysis was obtained. TEM and DLS measurements showed that nanostructureswith OsPAA (d=11 nm) and microstructures with OsBPEI (d=1.5 µm) were obtained, and allenzyme in solution are incorporated to these particles. Phosphate ions at low concentrations (1mM) improve the formation and incorporation in LBL systems despite polyelectrolyte chargescreening.3 In OP systems higher concentrations is needed for cross-linking betweenpolyelectrolyte and enzyme to form these particles. Cross-linking also depends on type ofpolyelectrolyte (linear or branched) but is independent of pI of enzyme. With these systemsglucose and hydrogen peroxide biosensors were constructed, and in addition OsBPEI-GOxsystem was used as bioanode in a biofuel cell showing in all cases an improved performancerespect to similar systems. Also, LBL assembly allows to modify very small surfaces with apotential impact in the construction of micro and nanodevices.