Simple size-selective separation and microscopic characterization of Phe–Phe nanotubes and study of its internalization inside CHO cells

Phe–Phe nanotube internalization in Chinese hamster ovary (CHO) cells is imaged through the transmission electron microscopic (TEM) study. Size-selective separation of peptide nanotubes (NTs) is of great value when we think about its application in biocompatible drug delivery. This paper describes a simple size-selective separation protocol for separating Phe–Phe NTs. During the synthesis, it is commonly observed that peptide NTs are formed with a range of sizes in their width and length and hence easy separation techniques of NTs are essential. Removal of the monomers from NTs is also important. Microscopic imaging of peptide NTs is also important in this context and particularly when these are used in the diagnostic and therapeutic purposes. Herein, we report a straightforward size-selective separation of peptide NTs by size exclusion chromatography (SEC) and imaging the fractions through TEM, confocal, and deconvolution microscopic techniques. Here, we report, for the first time, use of deconvolution fluorescence microscopy to detect NTs. As commonly used photo microscope cannot resolve the images of very small particles (e.g., less than micron scale), electron microscopy is widely used in imaging of NPs. Hence, systematic peptide NTs separation followed by these characterization techniques provides an option to study the internalization of NTs inside cells. Intake of peptide NTs inside cells is promising for their use in drug delivery as well as in imaging study.