Latent bloodstain detection using a selective turn-on NIR fluorescence dye responsive to serum albumin

Abstract

Latent bloodstains can be visualized using a selective turn-on NIR fluorescence dye responsive to serum albumin. This non-destructive method can detect aged bloodstains and image latent blood fingerprint patterns against colorful backgrounds.

Switch-on near infrared emission in albumin behind dark fabric: toward application in forensic latent bloodstain detection

“…Flash column chromatography was performed on a Teledyne CombiFlash Rf+ with prepacked Teledyne RediSep Rf Gold C18 Reversed-Phase 15.5-30 g cartridges. The 1 H and 13 C NMR spectra were recorded on a Bruker Avance-400 (400 MHz) spectrometer, and the chemical shis were reported in ppm using residual solvent signals as internal standards (CD 3 OD d = 3.31 ppm for 1 H NMR and d = 49.00 ppm for 13 C NMR). Data were reported as s = singlet, d = doublet, t = triplet, q = quartet, p = pentet, m = multiplet, br = broad; coupling constants, J, were in Hz.…”

“…S16 †) d 8.85 (d, J = 6.7 Hz, 2H), 7.64 (d, J = 8.6 Hz, 2H), 7.51-7.37 (m, 4H), 7.21 (d, J = 8.3 Hz, 4H), 7.08 (d, J = 8.6 Hz, 4H), 7.06-6.99 (m, 1H), 6.93 (d, J = 8.5 Hz, 1H), 6.59 (t, J = 13.1 Hz, 2H), 6.22 (t, J = 13.0 Hz, 1H), 4.12 (t, J = 5.8 Hz, 4H), 2.93 (t, J = 8.2 Hz, 4H), 2.16 (s, 3H), 2.10-1.94 (m, 12H). 13 C NMR (101 MHz, CD 3 OD, Fig. S17 †) d 161.…”

“…3,4 Our group has previously reported an indolizine squaraine dye (SO3SQ, Scheme 1) that demonstrates "ultra-bright" switchon near infrared (NIR, 700-1000 nm) emission upon binding to albumin in fetal bovine serum (FBS), human serum albumin (HSA), and on latent blood stains. [11][12][13] Albumin has previously been shown to enhance dye emission for sensors and for in vivo biological imaging; however, these reports have not been found to be applicable in forensic imaging (Table S2 †). 9, [14][15][16][17][18][19][20][21][22][23][24][25] The albumin-SO3SQ complex displays longer lived emission (on the order of days to weeks), more selectivity for blood (since albumin is specic to and ubiquitous in blood), 26,27 and leaves DNA less perturbed than with oxidizing solutions or ultraviolet (UV, 100-400 nm) light.…”

“…9, [14][15][16][17][18][19][20][21][22][23][24][25] The albumin-SO3SQ complex displays longer lived emission (on the order of days to weeks), more selectivity for blood (since albumin is specic to and ubiquitous in blood), 26,27 and leaves DNA less perturbed than with oxidizing solutions or ultraviolet (UV, 100-400 nm) light. 13 Upon binding to albumin, the dye most likely assumes a restricted conformation with fewer avenues for non-radiative decay and thus a brighter emission compared to water alone. 12,13,28 The NIR emission of SO3SQ (l emis max = 722 nm) extends beyond the absorption of UV and visible light (400-700 nm) by molecules like hemoglobin in the blood.…”

“…13 Upon binding to albumin, the dye most likely assumes a restricted conformation with fewer avenues for non-radiative decay and thus a brighter emission compared to water alone. 12,13,28 The NIR emission of SO3SQ (l emis max = 722 nm) extends beyond the absorption of UV and visible light (400-700 nm) by molecules like hemoglobin in the blood. 29 For this reason, NIR emission is preferred over the blue emission from luminol at 425 nm.…”