Highly Sensitive Broadband Raman Sensing of Antibiotics in Step-Index Hollow-Core Photonic Crystal Fibers

Broadband fiber enhanced Raman spectroscopy (FERS) in aqueous media is introduced in elaborated hollowcore photonic crystal fibers. The high requirements on the filigree fiber structure were thoroughly analyzed. A preparation technique was developed for the precise selective filling of such high-performance sensor fibers. Broadband step-index light guidance in aqueous solutions was achieved for the first time in photonic crystal fibers across the whole visible and NIR spectral range. Thus, strong Raman signal enhancements could be demonstrated with various excitation wavelengths and for the high-wavenumber region. The novel fiber enhancement technique was exploited for low-concentration measurements of the frequently used broad-spectrum antibiotic moxifloxacin down to 1.7 μM in only a 4 nL sample volume. These unique abilities for chemical-selective, highly sensitive antibiotic monitoring will pave the way for rapid, minimally invasive analysis of antibiotic concentrations in serum and other body fluids from infected sites. This will allow a precise therapeutic drug monitoring and consecutive rapid dose adjustment in critically ill patients who require individual dosing due to large inter- and intraindividual changes in pharmacokinetic properties.