Fig. 3

Responses of rLDH7-based µPAD APTEC sensors towards varying concentrations of rPfLDH target. µPAD sensors were constructed using the rLDH7 aptamer and exposed to varying concentrations of rPfLDH before the attached rPfLDH was visualised using the Malstat colour assay. A Contrast-enhanced photographs of µPAD sensors following application of varying concentrations of rPfLDH and subsequent colour development. Annotations indicate the concentration of rPfLDH in the sample applied to the sensor. The original scanned images are presented in Additional file information (Additional file 1: Fig. S3) and were used to construct the measurements of ∆I presented in Fig. 3B and C. B Scatterplot of the measured colour intensities at the various zones of the µPAD as a function of the applied rPfLDH concentration. Binding affinity curves based on concentration-dependent detection fitted from colour intensity using Eq. 3 are presented as lines, with measurements reporting the mean ± standard error of the estimated variable. The kinetic parameters estimated from the fit are annotated for each zone. *—indicates that a particular fitted variable. Annotated has p < 0.05 for the null hypothesis of this value being = 0 (determined via t statistic testing). A baseline \({I}_{0}\) of 22 pixels was set for all fitted models, based on the average Zone 2 responses. C Semi-logarithmic scatterplot of the measured contrast between test and control zones. †—indicates that the values for Zone 1 contrast have mean values that are significantly above zero; (p ≤ 0.05; 1-sample t-test). D Responses of commercially-available, antibody-based, RDT devices (OnSite^® Malaria Pf/Pan Ag Rapid Test) towards varying concentrations of rPfLDH target used in this study. The target protein was dissolved in buffer, before being applied to the RDT. Images were captured and contrast-enhanced, as was performed for APTEC tests. The “Pan” test line is specific to PLDH, while the “Pf” test line is specific to PfHRP2