Monitoring Molecular Uptake and Cancer Cells’ Response by Development of Quantitative Drug Derivative Probes for Chemical Imaging

Infrared (IR) spectroscopic imaging combines the molecular specificity of vibrational spectroscopy with imaging capabilities of microscopy, potentially allowing for simultaneous quantitative observations of drugs and cellular response. However, accurately quantifying drug concentration within changing cells is complicated by the overlap between exogenous molecules' and native cellular spectra. Here, we address this challenge by developing a derivative of the widely used chemotherapeutic doxorubicin as a spectral bioprobe (DOX-IR) using a strongly absorbing metal-carbonyl moiety [(Cp)Fe(CO)₂]. The developed protocol for synthesis is validated by complete spectral characterization of DOX-IR, and an IR calibration curve is obtained for the two distinguishable peaks within the biosilent spectral region. The strong absorbance allowed cellular uptake of DOX-IR to be quantified using routinely available IR microscopes without any modifications. The capability to quantify drug compounds in a nondestructive and high-throughput manner using IR spectroscopic imaging provides straightforward analysis without perturbing the sample.