Fig 2: (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.

Fig 3: Mean readouts for marker IL8 using the enzymatic Assay Format (VI) in combination with different substrates: TMB1 (), TMB2 (), and ODI (). The blank (0 ng/L) is represented by 1 ng/L on the log scale.

Fig 4: 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 5: 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.