Figure 4.

Sample concentration using mixed a AuNP/SPMNP system for lateral flow immunoassays. (a) Polymer and antibody-coated AuNPs were combined with polymer-coated SPMNPs and human plasma spiked with malaria antigens. (b) Heating to 40 °C induced a polymer phase transition and coaggregation of the AuNPs and SPMNPs, which were collected using an external magnet. The supernatant was removed, and the particles were redispersed in a smaller volume of buffer. (c) The concentrated particles were directly applied to a standard lateral flow immunoassay and migrated down the paper strip by capillary action. The gold nanoparticles accumulated at the test and control lines, allowing for visual inspection of the results, while the SPMNPs were transported into the waste. Figure inspired by Nash et al.²²