How RGD peptides influence the M cell targeting properties of carboxymethyl starch-based nanocapsules: Binding mechanism and delivery applications

The structural properties of ligand-mediated carriers play pivotal role in their architecture and properties. Here, the impact of grafting degree of RGD peptides on the M cell targeting ability of carboxymethyl starch (CMS) was systematically investigated. The prepared M cell-targeting starch-based materials (CMS@R) demonstrated remarkable M cell targeting capabilities, which could be attributed to the specific binding between RGD peptides and the integrin α 5 β 1 on M cell surface. Furthermore, an increased grafting density of RGD peptides was found to enhance the M cell targeting efficiency of CMS@R. However, RGD peptides would reduce the electronegativity of CMS and increases the steric hindrance between the starch-based materials, which are not conductive to the binding between the starch-based materials. Nanocapsules fabricated with CMS@R with relatively lower RGD grafting degree exhibited good controlled release property (87.73% of the encapsulated OVA could reaching M cells) and high transport efficiency through the M cells pathways (apparent permeability: 8.32 × 10 -5 cm/sec). Therefore, appropriate RGD peptides grafting degree tailoring of starch-based materials, except their molecular weight, is required to meet both requirements of the M cells binding affinity and structural stability of the starch-based nanocapsules during oral delivery.