Fig 2: Normalized colorimetric signals in (a) assay buffer with labels oCNPs (Assay Scheme III); (b) in urine (1:3) with oCNPs (c) in assay buffer using HRP (Assay Scheme VI); (d) in urine (1:3) with HRP. Calibration curves for 0 to 295 µg/L: IL8, VEGF, and DCN; including standard deviations of three replicates. The blank signal (0 ng/L) is represented by 15 ng/L on the log scale.

Fig 3: Schematic presentation of the detection of IL8 binding (Incubation Steps 3, 4, and 5) for tested Assay Formats (I)–(VI) including the limit of detection (LOD) (ng/L), dynamic range (ng/L), and coefficient of variation (%). * visually determined.

Fig 4: JPEG images of colorimetric subarrays after incubation with different labels based on Formats (I)–(VI). The corresponding IL8 concentrations are indicated in the columns as 15, 135, 1215, 10,931, and 98,376 ng/L.

Fig 5: (a) Schematic presentation of six distinct assay formats for colorimetric detection: (I) cAB + IL8 + gold-labeled dAB, (II) cAB + IL8 + carbon-labeled dAB, (III) cAB + IL8 + oxidized carbon-labeled dAB, (IV) cAB + IL8 + biot. dAB + neutravidin–carbon, (V) cAB + IL8 + biot. dAB + strp–gold, and (VI) cAB + IL8 + biot. dAB + strp-HRP + enzyme substrate. Slides treated via gold nanoparticles were further stained by silver (Ag). (b) Illustration of the antibody (in orange) coupling process using gold (red) and carbon (black) nanoparticles.