Lysine Dendrigraft Nanocontainers. Influence of Topology on Their Size and Internal Structure

Abstract

Poly-l-ysine dendrigrafts are promising systems for biomedical applications due to their biodegradability, biocompatibility, and similarity to dendrimers. There are many papers about the use of dendrigrafts as nanocontainers for drug delivery. At the same time, the number of studies about their physical properties is limited, and computer simulations of dendrigrafts are almost absent. This paper presents the results of a systematic molecular dynamics simulation study of third-generation lysine dendrigrafts with different topologies. The size and internal structures of the dendrigrafts were calculated. We discovered that the size of dendrigrafts of the same molecular weight depends on their topology. The shape of all studied dendrigrafts is close to spherical. Density profile of dendrigrafts depends on their topology.

Keywords: dendrigrafts; molecular dynamics simulation; poly-l-lysine.

Figure 1

Three different lysine dendrigrafts: (a) dendrigraft 1; (b) dendrigraft 2; and (c) dendrigraft 3 with eight lysine residues in each main chain (core) marked by black points and 15 lysine residues (marked by green, red and blue points) in each of the eight side chains. Only one of the eight side chains is shown in Figure 1a–c for clarity: (a) dendrigraft 1, with 14 intermediate lysine residues (green), without branching lysine (red), and with one terminal lysine (blue) in each side chain; (b) dendrigraft 2, with eight intermediate lysines (green), three branching points (red), and four terminal lysine residues (blue) in each side chain; (c) dendrigraft 3, without intermediate lysine residues (green) and with seven branching points (red) and eight terminal lysine residues (blue) in each side chain.

Figure 2

(a) The variation of the gyration radius R_g with time t in picoseconds and (b) the distribution function for dendrigrafts 1, 2, and 3.

Figure 3

Distribution of side chain end-to-end distance (distance between the C_α atom of the main chain and terminal NH₃⁺ group of the corresponding side chain) for dendrigrafts 1, 2, and 3.

Figure 4

Snapshots of dendrigrafts: dendrigraft 1 (a); dendrigraft 2 (b); and dendrigraft 3 (c).

Figure 5

Normalized density profiles for dendrigrafts 1, 2, and 3 of generations G = 3, where r is the radial distance from the dendrigraft’s center of mass.

Figure 6

Distribution of (a) all charged NH₃⁺ groups and (b) terminal charged NH₃⁺ groups for dendrigrafts 1, 2, 3.

Figure 7

Distribution of end-to-end distance for dendrigrafts 1, 2, 3.