Applications of AFM-IR for drug delivery vector characterization: infrared, thermal, and mechanical characterization at the nanoscale.

The development of effective drug delivery systems requires in-depth characterization of the micro- or nanostructure of the material vectors with high spatial resolution, resulting in a deep understanding of the design-function relationship and maximum therapeutic efficacy. Atomic force microscopy-infrared spectroscopy (AFM-IR) combines the high spatial resolution of AFM and the capabilities of IR spectroscopy to identify chemical composition and it has emerged as a powerful tool for the detailed characterization of a drug delivery system at the nanoscale. In addition, the instruments also allow thermal and mechanical evaluation at the nanoscale. In this review, we highlight the applications of AFM-IR in various drug delivery systems, including polymer-based carriers, lipid-contained nanocarriers, and metal-based nanocarriers. The existing challenges as well as the future perspectives for the application of AFM-IR for drug delivery vector characterization are also discussed.