3D inkjet printing of hybrid electroactive ink based on molecularly imprinted polymers for lipopolysaccharides detection

• Hybrid electroactive ink incorporating molecularly imprinted silica particles. • Custom designed screen-printed electrodes via hybrid 3D inkjet printing. • Specific detection of lipopolysaccharides from Pseudomonas aeruginosa . • Sensitivity, low detection limit and fast response time without redox probe. • Selectivity vs. other lipopolysaccharide species from S. enterica and E. coli . A hybrid electroactive ink based on molecularly imprinted polymer (MIP) hollow microparticles, zinc oxide nanoparticles (ZnO NPs) and conductive carbon paste (CP) is reported herein for the first time. The MIP/ZnO NPs/CP and corresponding non-imprinted NIP/ZnONPs/CP modified inks were screen-printed on plastic substrates via 3D inkjet technology to cover around 40 working screen-printed carbon electrodes (SPCE) pieces in a single batch. The custom-made electrochemical MIP/ZnONPs/CP@SPCE sensor was designed for the detection of bacterial endotoxins, i.e. , lipopolysaccharides (LPS), derived from Pseudomonas aeruginosa . Hollow MIP silica microparticles with specific properties for 3D printing application, in terms of granulation and morphology, were synthesized via sol-gel method using tetraethyl orthosilicate and (3-aminopropyl) triethoxysilane as monomers. Following the structural and morphological characterization of microparticles, the evaluation of template rebinding indicated a clear specificity of MIPs for LPS compared to the NIPs. Hybrid MIP/ZnONPs/CP and NIP/ZnONPs/CP inks were characterized using morphological and structural methods, which confirmed a viscosity of 25.000 mPa.s, a granulation of <20 µm, and a solid powder content of <27 %, as well as a homogenous incorporation of MIP particles and ZnONPs in the conductive CP. Finally, the electrochemical evaluation of the modified MIP/ZnONPs/CP@SPCE sensor revealed a good sensitivity to LPS molecules in PBS at pH 7.4, in the linear working range 1 - 100 µM, where a 0.058 µM limit of detection (LOD) and a response time less than or equal to 1 min were determined. The selectivity of the MIP/ZnONPs/CP@SPCE sensor towards LPS from Salmonella enterica and Escherichia coli was also assessed, highlighting a clear difference between these structural resembling species.