We demonstrate the use of spatially offset Raman spectroscopy (SORS) in the identification of counterfeit pharmaceutical tablets and capsules through different types of packaging. The technique offers a substantially higher sensitivity than that available from conventional backscattering Raman spectroscopy. The approach is particularly beneficial in situations where the conventional Raman backscattering method is hampered or fails because of excessive surface Raman or fluorescence signals emanating from the packaging, capsule shell, or tablet coating contaminating the much weaker subsurface Raman signals of the active pharmaceutical ingredients and excipients held in the product. It is demonstrated that such interfering signals can be effectively suppressed by SORS.There is an increasing need for the noninvasive verification of the authenticity of pharmaceutical products on the market. The number of generic copies of popular and well-known drugs is steadily increasing worldwide. The targeted drugs in the developed world often include so-called lifestyle drugs and drugs for chronic diseases. More seriously, in Africa and Asia, frequently the life-saving medicines, such as anti-infective drugs, are plagued by this problem. For example, the infiltration of the market by fake antimalarial drugs currently presents a major crisis in eastern Asia. 1 Although the generic copy often has the correct molecule as its active pharmaceutical ingredient (API), the formulation of the drug can be very different, affecting the effectiveness of treatment. The worst case and potentially life-threatening scenario is when the generic product does not contain the supposed active ingredient at all. In recent years, large amounts of counterfeit drugs have been discovered and withdrawn from the official supply chain both in the UK and the United States, and the spread of drug sales over the Internet further exacerbates the problem. 2 Terrorists are also believed to be partially funding their activities from the sale of counterfeit drugs. The reason for this rapid increase is that these operations are fast, have a low risk for detection, and produce large profits. To combat this increasing problem, the U.S. Food and Drug Administration (FDA) formed an internal task force in 2003. A very recent article in the Lancet gives a general overview of the counterfeit drug problem together with examples and current methods of analysis. 3 Given the extent of the problem and its current trend, it is becoming increasingly important to verify the actual content of drugs throughout the entire supply chain. This task is complicated by the fact that once tablet packaging is opened, it becomes of no use, something which calls for a noninvasive method of analysis. Ideally, the method should be fast and provide clear and easy-to-interpret results. A handheld instrument is also highly desirable as many of these operations need to be performed in the field. One potential candidate technique for this analysis is near-infrared spectroscopy (NIR), which is a ...
We present a Raman spectroscopic method for the noninvasive detection of liquid explosives within bottles, and other packaging, of substantially higher sensitivity and wider applicability than that currently available via conventional Raman spectroscopy. The approach uses a modification of the spatially offset Raman spectroscopy (SORS) concept, which permits the interrogation of a wide range of containers, including transparent, colored, and diffusely scattering plastic and glass beverage, medicine, and cosmetic bottles, with no change in experimental geometry. The enhanced sensitivity is achieved by the technique's inherent ability to effectively suppress fluorescence and Raman contributions originating from the wall of the container. The application is demonstrated on the noninvasive detection of hydrogen peroxide solution, a critical component of a number of liquid explosives. In contrast to conventional Raman spectroscopy, the modified SORS concept enables the detection of concealed hydrogen peroxide solution in all the studied cases.
Beads labelled using surface enhanced resonance Raman scattering (SERRS) are highly sensitive and specific tags, with potential applications in biological assays, including molecular diagnostics. The beads consist of a nucleus containing dye labelled silver-nanoparticle aggregates surrounded by a polymer core. The nuclei generate strong SERRS signals. To illustrate the coding advantage created by the sharp, molecularly specific SERRS signals, four specially designed SERRS dyes have been used as labels and three of these have been combined in a multiplex analysis. These dyes use specific groups such as benzotriazole and 8-hydroxyquinoline to improve binding to the surface of the silver particles. The aggregation state of the particles is held constant by the polymer core, this nucleus also contains many dye labels, yielding a very high Raman scattering intensity for each bead. To functionalise these beads for use in biological assays an outer polymer shell can be added, which allows the attachment of oligonucleotide probes. Oligonucleotide modified beads can then be used for detection of specific oligonucleotide targets. The specificity of SERRS will allow for the detection of multiple targets within a single assay.
In support of the efforts to combat the illegal sale and distribution of counterfeit anti-malarial drugs, we evaluated a new analytical approach for the characterization and fast screening of fake and genuine artesunate tablets using a combination of Raman spectroscopy, Spatially Offset Raman Spectroscopy (SORS) and Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) imaging. Vibrational spectroscopy provided chemically specific information on the composition of the tablets; the complementary nature of Raman scattering and FTIR imaging allowed the characterization of both the overall and surface composition of the tablets. The depth-resolving power of the SORS approach provided chemically specific information on the overall composition of the tablets, non-invasively, through a variety of packaging types. Spatial imaging of the tablet surface (using ATR-FTIR) identified the location of domains of excipients and active ingredients with high sensitivity and enhanced spatial resolution. The advantages provided by a combination of SORS and ATR-FTIR imaging in this context confirm its potential for inclusion in the analytical protocol for forensic investigation of counterfeit medicines.
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