Optimization of the Polymer Coating for Glycosylated Gold Nanoparticle Biosensors to Ensure Stability and Rapid Optical Readouts

The development of new analytical tools to probe pathogenic infection processes and as point-of-care biosensors is crucial to combat the spread of infectious diseases or to detect biological warfare agents. Glycosylated gold nanoparticles that change color due to lectin (carbohydrate-binding protein) mediated aggregation may find use as biosensors but require a polymer coating between the particle surface and sugar to ensure stability in complex media. Here, RAFT polymerization is employed to generate glycosylated polymers to coat gold nanoparticles. Rather than being a passive component, it is shown here that the polymer coating has to be precisely tuned to achieve a balance between saline (steric) stability and speed of the readout. If the polymer is too long it can prevent or slow aggregation and hence lead to a poor readout in sensing assays. The optimized glyco-nanoparticles are also demonstrated to be useful for rapid detection of a ricin surrogate.