Rapid detection and identification of overdose drugs in saliva by surface-enhanced Raman scattering using fused gold colloids

Abstract

The number of drug-related emergency room visits in the United States doubled from 2004 to 2009 to 4.6 million. Consequently there is a critical need to rapidly identify the offending drug(s), so that the appropriate medical care can be administered. In an effort to meet this need we have been investigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect and identify numerous drugs in saliva at ng/mL concentrations within 10 minutes. Identification is provided by matching measured spectra to a SERS library comprised of over 150 different drugs, each of which possess a unique spectrum. Trace detection is provided by fused gold colloids trapped within a porous glass matrix that generate SERS. Speed is provided by a syringe-driven sample system that uses a solid-phase extraction capillary combined with a SERS-active capillary in series. Spectral collection is provided by a portable Raman analyzer. Here we describe successful measurement of representative illicit, prescribed, and over-the-counter drugs by SERS, and 50 ng/mL cocaine in saliva as part of a focused study.

Figure 1.

Chemical structures for the drugs presented in this study.

Figure 2.

Photographs of surface-enhanced Raman spectroscopy (SERS)-ID and SERS-active capillaries.

Figure 3.

Comparison of (a) Raman spectroscopy (RS) of pure cocaine on a glass slide to (b) SERS for 100 ng/mL (100 ppb) cocaine in water (as cocaine•HCl) using a fused gold colloid-doped sol-gel in a 1 mm capillary. Conditions: (a) 300 mW of 785 nm, 5 minute acquisition, (b) 75 mW of 785 nm excitation, 1 minute acquisition; both at 8 cm⁻¹ resolution. The SERS spectral intensity has been multiplied by 10 so that features are evident, and offset for clarity.

Figure 4.

SERS of illicit drugs: (a) 1-(1-phenylcyclohexyl) piperidine (PCP), (b) methamphetamine, (c) 3,4-methylenedioxymethamphetamine (MDMA), (d) lysergic acid diethylamide (LSD), and (e) heroin. Conditions as in Figure 3(b), except at 0.1 mg/mL. Ordered to show spectral similarity. Intensities normalized and offset for clarity.

Figure 5.

SERS of prescription drugs: (a) diazepam (Valium®), (b) methylphenidate (Ritalin®), (c) meperidine (Demerol®), (d) hydrocodone (Vicodin®), and (e) oxycodone (Oxycotin®). Conditions as in Figure 4. Ordered to show spectral similarity. Intensities normalized and offset for clarity.

Figure 6.

SERS of OTC drugs: (a) acetaminophen, (b) aspirin, and (c) ibuprofen. Conditions as in Figure 4. Intensities normalized and offset for clarity.

Figure 7.

SERS of (a) oxycodone as an unknown, (b) oxycodone in the spectral library, and (c) hydrocodone as the second best match in the spectral library. The Hit Quality Index (HQI) scores were (b) 0.073 and (c) 0.734, indicating (a) as the best match. Conditions as in Figure 4.

Figure 8.

SERS of (a) 50 ng/mL cocaine, (b) 1 mcg/mL PCP, (c) 1 mcg/mL diazepam, and (d) 10 mcg/mL acetaminophen extracted from saliva. Conditions as in Figure 4, except at indicated concentrations.

Figure 9.

SERS of (a) 50 ng/mL cocaine in saliva as an unknown, (b) 0.1 mg/mL cocaine in the spectral library, and (c) ethylbenzoylecgonine as the second best match in the spectral library. The HQI scores were (b) 0.287 and (c) 0.348. Conditions as in Figure 4, except at indicated concentrations.