Fig. 2

Screening of aptamers for ability to capture 133 nM of rPfLDH for the development of APTEC-based µPAD biosensors. A Enhanced-colour scanned images of the tested µPAD sensors following exposure to rPfLDH and subsequent Malstat staining of captured enzyme. LDHp11, rLDH4, rLDH7, pL1 and 2008s aptamers were screened in this study. The original scanned images are presented in Additional file information (Additional file 1: Fig. S2). Unenhanced images were used to construct the measurements of ∆I presented in Fig. 2B nd C. Figure legend (annotations at the left) show the various zones monitored for the measurement B – background area of the test; 1 –Zone 1 (test zone); 2 –Zone 2 (control zone); 3 – Zone 3 (test zone and wicking area). B Comparison of the analysed colorimetric intensity of the aptamer-rPfLDH complex after colour development, ∆I vs. the background. *- indicates screened aptamer responses with Zones 1 and 3 exhibiting significant difference in measured colorimetric intensities compared to its Zone 2 control (p ≤ 0.025; two-tailed, unpaired, Student’s t-test). C Comparison of the contrast of individual sensors (the difference in colour intensity between the test zones and the control zones for individual sensors). Annotation shows results of the comparison of ANOVA analysis comparing the influence of the sequence tested with the mean contrast obtained at µPAD sensors. ‡—indicates significant difference in a particular aptamer’s colorimetric intensity for zones 1 and 3, compared to those obtained using LDHp11 aptamer (Tukey post hoc test, p ≤ 0.05)