This work investigates polyaniline (PANI) nanoparticles, (synthesised using dodecylbenzenesulphonic acid (DBSA) as a dopant), as a novel, highly processable, non-diﬀusional mediating species in an enzyme biosensing application. These nanoparticles are readily dispersed in aqueous media which helps overcome some of the processability issues traditionally associated with polyaniline. Modification of screen-printed electrodes was readily achieved with these aqueous nanoparticle dispersions, where the nanoparticles were simply cast by a drop-coating method onto the surface. After suitable pH adjustment, it was shown that horseradish peroxidase (HRP) enzyme could be added to the dispersion, and cast simultaneously with the conducting polyaniline. This eﬀective fabrication method involves no electrochemical steps, and as such is easily amenable to mass production. The feasibility of casting enzyme with polyaniline nanoparticles is demonstrated in this short communication. More accurate deposition of protein-containing inks onto screen-printed carbon working electrodes could in the future transfer the drop-coating protocol from manual deposition to largescale production by mechanical methods such as ink-jet printing.