Simultaneous photoacoustic detection of multiple inflammatory biomarkers using bioconjugated gold nanorods as selective targeting agents

In vitro cell experiments have been performed to detect the upregulation of ICAM-1 and E-selectin simultaneously by photoacoustics (PA). Human umbilical vein endothelial cells (HUVECs) were grown on gelatin-coated glass slides and stimulated with inflammatory cytokines to induce the expression of the inflammatory biomarkers ICAM-1 and E-selectin. Gold nanorods (GNR) of aspect ratio (AR) 1:3 with absorption centered at 715 nm conjugated to anti-ICAM-1 antibody and GNR of AR 1:3.5 with absorption centered at 800 nm conjugated to anti-E-Selectin were exposed to HUVECs with different stimulation conditions. A focused high frequency ultrasonic transducer (60 MHz, f/1.5) was used to scan the PA signal over the top surface of the cell containing slides. Averaged PA signal intensity from the stimulated cells was about 3 folds higher (9 dB) compared to the unstimulated cells for both ICAM-1 and E selectin. The strong binding of GNRs to the upregulated biomarker was evidenced by the fluorescence imaging. Exposure of HUVEC cells to GNR conjugated to isotype control antibodies confirms a low level non-specific binding.