Therapeutic drug monitoring (TDM) at the point of care is of paramount significance in healthcare. It enables timely monitoring of drug concentrations in a patient's body-fluids, especially in the bloodstream, ensuring personalized dosing for optimal therapeutic outcomes while minimizing side effects and toxicity. TDM is crucial for treating sepsis patients, as their altered pharmacokinetics make accurate antibiotic dosing challenging. Additionally, they need quick dose adjustments to match evolving clinical needs. TDM ensures individually optimal antibiotic levels for best efficacy. Recently, we exploited the advantages of deep-UV Raman spectroscopy in drug sensing of antibiotics for TDM. Firstly, deep-UV excitation enhances the Raman scattering, which is particularly useful for compounds with weak Raman signals, including low concentrated drugs. Secondly, it effectively minimizes fluorescence interference, a common challenge in conventional Raman spectroscopy. This makes deep-UV excitation especially suitable for monitoring active ingredients, such as fluoroquinolones and β-lactam antibiotics, in body fluids like urine and plasma at clinically relevant concentrations. Therefore, deep-UV Raman spectroscopy holds significant potential as a tool for personalized antibiotic dosing through rapid TDM at the point of care.
We report on OH diffusion effects at preparation of hollow core fibers with large central hexagonal and square shaped cores. The fibers with up to 30 μm central hole diameter are suitable for chemical sensor applications, especially for gases. We demonstrate the single mode guidance at selective bands in the UV, VIS and NIR region. Key feature of low loss in specific spectral windows of such fiber structures is the control of thickness and homogeneity of the web bridges. The fibers achieve a minimum loss of 2 dB/m and effective single mode propagation in the wavelength range between 270 nm and 1500 nm. The thinness of the bridges beneath one micrometer results in a deep impregnation of OH by diffusion from the cavities during thermal processing, e.g. fiber drawing. Up to 1000 ppm by weight of OH had been measured in the silica web surrounding the hollow core. Obviously, the OH sources are atmospheric humidity and condensed water originating from using a hydrogen-oxygen torch at final preform fabrication. The paper shows the good agreement between OH diffusion simulation and experimental observation of OH impregnation in the hollow core web.
We report about the experimental combination of UV resonance Raman sensing (UV-RRS) and fiber enhanced Raman sensing (FERS) on pharmaceuticals. The results show that the chemical sensitivity is highly improved and at the same time the sample volume is reduced compared to conventional measurements. A hundreds-fold improvement of the limit of detection (LOD) has been achieved with the combination of resonance Raman enhancement and fiber enhancement. The enhanced Raman signal has a reliable linear relationship with the concentration of the analyte, and therefore shows great potential for quantitative analysis of pharmaceuticals.
Fiber enhanced Raman sensing is presented for versatile and extremely sensitive analysis of pharmaceutical drugs and biogenic gases. Elaborated micro-structured optical fibers guide the light with very low losses within their hollow core and provide at the same time a miniaturized sample container for the analytes. Thus, fiber enhanced Raman spectroscopy (FERS) allows for chemically selective detection of minimal sample amounts with high sensitivity. Two examples are presented in this contribution: (i) the detection of picomolar concentrations of pharmaceutical drugs; and (ii) the analysis of biogenic gases within a complex mixture of gases with analytical sensitivities in the ppm range.
The structure of the antimalarial drug halofantrine is analyzed by means of density functional theory (DFT) calculations, IR, and Raman spectroscopy. Strong, selective enhancements of the Raman bands of halofantrine at 1621 and 1590 cm−1 are discovered by means of UV resonance Raman spectroscopy with excitation wavelength exc=244 nm. These signal enhancements can be exploited for a localization of small concentrations of halofantrine in a biological environment. The Raman spectrum of halofantrine is calculated by means of DFT calculations [B3LYP/6-311+G(d,p)]. The calculation is very useful for a thorough mode assignment of the Raman bands of halofantrine. The strong bands at 1621 and 1590 cm−1 in the UV Raman spectrum are assigned to combined CC stretching vibrations in the phenanthrene ring of halofantrine. These bands are considered as putative marker bands for interactions with the biological target molecules. The calculation of the electron density demonstrates a strong distribution across the phenanthrene ring of halofantrine, besides the electron withdrawing effect of the Cl and CF3 substituents. This strong and even electron density distribution supports the hypothesis of stacking as a possible mode of action of halofantrine. Complementary IR spectroscopy is performed for an investigation of vibrations of polar functional groups of the halofantrine molecule.
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