Background

Developing new drug-based therapeutic approaches against Intestinal Bowel Disease (IBD) must overcome numerous challenges, including potential off-target effects, large-scale production costs, and the need to ensure tissue-specific delivery, systemic safety, and low toxicity. Our group and others have recently demonstrated that artificially synthesized nanoparticles could target low doses of drugs (e.g., siRNAs, proteins, or peptides) to colonic tissues or colonic immune cells, such as macrophages (Ulbrich and Lamprecht, 2010; Chen et al., 2017). However, these synthetic NPs to date have two major limitations: i) each constituent of the synthesized nanoparticle must be examined for potential in vivo toxicity before clinical application; and ii) the production scale is limited. The use of nanoparticles derived from natural sources may overcome these limitations. In this context, we reported that a special population of ginger-derived nanoparticles (GDNP-2) could reduce colitis and colitis-associated colon cancer (Zhang et al., 2016). Naturally occurring GDNP-2 is also safer and cheaper than synthetic NPs. We further identified 6-shogaol as a major candidate that may account for the anti-inflammatory and anti-cancer activities of GDNP-2 (Yang et al., 2020). To construct a nanocarrier that is more clearly defined than GDNP-2, we characterized ginger lipid-derived nanoparticles (GLDNP) and demonstrated that they could be used as a natural carrier to deliver natural anti-inflammatory drug candidates such as 6-shogaol, M2, or M13 to the colon and reduced colitis in mice (Yang et al., 2020).

Atomic force microscopy (AFM) is a versatile and powerful technique to characterize the morphology of nanoscale and submicron structured materials. It has been widely used to visualize different types of NPs, including metal-, inorganic- (non-metallic), and organic-NPs. AFM has the advantages of simplicity in sample preparation and no need for electric conducting treatment (Morris et al., 2010). In previous studies, our group and others have extensively used AFM to analyze the morphology and structure of GLDNP (Zhang et al., 2017; Wang et al., 2019; Sung et al., 2020; Yang et al., 2020). However, no attempt has been taken to document the procedure of sample preparation and AFM parameter setting. In the following protocol, we will use the GLDNP as the specimen to demonstrate the process of obtaining AFM pictures for nanostructure characterization.