3D-Printed graphene/polylactic acid electrode for bioanalysis: Biosensing of glucose and simultaneous determination of uric acid and nitrite in biological fluids

Abstract Additive manufacturing, also known as 3D-printing, is receiving great interest by chemists due to the easy design of novel materials, fast prototyping and reducing waste, which enables large-scale fabrication of electrochemical devices. Herein we demonstrate the development of (bio)sensors for the analysis of biological fluids using 3D-printing. Fused deposition modelling was used to fabricate (bio)sensing platforms from commercially-available filaments made of polylactic acid containing graphene (G-PLA). An enzymatic glucose biosensor fabricated on the G-PLA surface was developed and applied for glucose sensing in blood plasma using chronoamperometry. Oxygenated groups from the polymeric matrix provides suitable condition to enzyme immobilization by crosslinking with glutaraldehyde. The biosensor presented a limit of detection (LOD) of 15 µmol L-1, inter-day and intra-day precision lower than 5%, and adequate recovery values (90-105%) for the analysis of plasma. We also show that the surface treatment of the 3D-printed sensor (mechanical polishing followed solvent immersion) provides improved electrochemical properties for the direct detection of nitrite and uric acid. Differential-pulse voltammetry and multiple-pulse amperometry under flow conditions were evaluated and compared for the determination of both species in saliva and urine. Highlights are presented for the amperometric detection within a linear range from 0.5 to 250 µmol L-1 for both analytes, LODs of 0.02 and 0.03 µmol L-1 for uric acid and nitrite, respectively, and high precision (RSD