A review of imaging methods for measuring drug release at nanometre scale: a case for drug delivery systems

Introduction: Current drug delivery research is focused on improving the efficacy of drug delivery systems, with emphasis on precise targeting, accurate dose delivery, strategies for overcoming the tissue barrier and monitoring the effects of drugs on their targets. To realize these goals, it is essential to determine the spatio-temporal bio-distribution of particles in the whole animal. Enabling such a measurement at the nanometer scale helps in the design of efficient systems. Areas covered: This article discusses the need for molecular imaging in drug delivery development and also reviews promising imaging methods. Moreover, the physics behind each method is explained and evaluated to derive advantages and limitations. The review enables the readers to select, use and modify the existing methods to implement imaging protocols for studying drug release from particular drug delivery. Expert opinion: Currently, the difference in pharmacodynamics obtained via various imaging modalities cannot be verified and hinders clinical use. To establish imaging as a scientific tool, its translation into clinical use is vital. Presently, there is no single imaging method suitable for drug-release studies. However, hybrid imaging has the potential to provide the desired imaging system.