摘要：

In this paper we report on the development of a diagnostic test for the detection of illegal drugs in saliva using a dis-posable micro-fluidic sample preparation cartridge which was fabricated using CO 2 and excimer laser ablation of a PMMA substrate assembly. The detection method is by immunoassay sensing on a surface plasmon resonance (SPR) platform. Experimental results shows that the immunoassay detection of the two illegal drugs tested are very sensitive and have a linear range for cocaine and MDMA of 0,01 pg/ml – 1 ng/ml and 0,1 pg/ml – 100 ng/ml respectively. INTRODUCTION Saliva is increasingly being used as an "ideal" sample matrix primarily as it can be collected non-invasively causing less stress to the person being tested and its composition correlates well to serum. "Point of care" (POC) diagnostic tests for illegal drugs in saliva will be becoming more important with advancing technological progress especially in "Road-side Traffic testing" where there is an immediate need for improved POC devices that can address areas concerning: spe-cificity, sensitivity, sample collection, handling and preparation and easy non technical usability. Oral fluid is a natural ultrafiltrate of plasma as substances are transported across epithelial membranes into oral fluid by passive diffusion across a concentration gradient. Drug transport into oral fluid is regulated by the physiochemical prop-erties of the drug (molecular weight, dissociation constants, lipid solubility and protein binding) and the cell membrane. Based on a modified version of the Henderson-Hasselbach equation, it is generally presumed that unbound weakly basic drugs will concentrate in oral fluid, while the opposite occurs for weakly acidic drugs [1]. Low-molecular mass com-pounds can also be transferred into oral fluid by active secretion or diffusion through pores in the cell membrane [2]. The blood concentrations of drugs cannot easily be compared to concentrations in oral fluid but on average studies have shown a reasonable correlation [3]. Oral fluid is increasingly used as an ideal sample matrix. It can be collected non-invasively and causes less stress to the person being tested. In many countries jurisdictions have adopted the use of oral fluid to detect the presence of drugs of abuse, particularly in relation to persons driving motor vehicles. A number of studies have been made about roadside oral fluid testing[3,4,5]. Surface Plasmon resonance (SPR) is an optical pheno-menon that occurs as a result of total internal reflection of monochromatic and polarized light at an interface consisting of thin gold or silver -coated prism carrying the biological component and a liquid environment, which is in direct con-tact with the biocomponent. The specific binding of measured analyte onto the active surface of the SPR device induces a refractive index change that can be monitored. The advantage of this method over most other optical sensors is that loading of the surface with a receptor element as well as interactions with analytes fitting to the receptor can be moni-tored in real time without any additional labeling. SPR technology is dependent on fluid being moved across the sensing surface and also is highly sensitive to any substance that could bind to the gold sensing surface. Therefore any inferring substances that could non-specifically bind to the sensing surface of which there are many in saliva (e.g. mucin) would need to be removed. This is where micro-fluidics can provided a solution. THEORY The aim of this study was to develop a diagnostic test for the detection of illegal drugs in saliva [6]. Here we describe a sample preparation and analytical detection method that addresses many of these problems outlined above. A dispos-able micro-fluidic system was developed where a saliva sample could be directly injected into the unit as shown in figure 1 and 2. If there were any drugs in the sample, the small drug molecules can travel through the partition into the carrier analysis buffer, which will be afterwards transported directly to the

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