Real-time toxicity testing of silver nanoparticles to Salmonella Enteritidis using surface plasmon resonance imaging: A proof of concept

In this paper we report for the first time on the suitability of surface plasmon resonance imaging (SPRi) for performing ecotoxicity testing of nanoparticles (NPs). Specifically, the impact of silver NPs (using Ag NM-300K) and ions (using AgNO3 salt) on Salmonella Enteritidis growth was assessed in Luria Bertani medium using the culture-capture-measure (CCM) based SPRi method. Clear effects were observed at 10 mg L− 1 Ag NPs characterised by shifted SPRi detection times (TD) by ca. 2.6 h compared to the control. Comparable results were obtained using 1 mg L− 1 Ag ions. No clear effects were observed at 1 mg L− 1 Ag NPs and 0.1 mg L− 1 Ag ions. Overall results match the current trend in nanoecotoxicology using bacteria (e.g. impact of Ag NPs between 1 and 10 mg L− 1 and higher toxicity of Ag ions compared to Ag NPs). The dose dependent patterns of toxicity were coherent with those obtained using a standard plating method; however, the SPRi approach was faster (i.e. results within a few hours) and generated kinetic data (i.e. real-time monitoring). In addition, SPRi presents many valuable intrinsic advantages (e.g. label-free, multiplex, bespoke and robust) over current approaches. Consequently, a plethora of opportunities for future developments and applications of SPRi in NP testing is associated with the proof of concept reported herein.