The influence of size, shape and vessel geometry on nanoparticle distribution

Abstract

Nanoparticles (NPs) are emerging as promising carrier platforms for targeted drug delivery and imaging probes. To evaluate the delivery efficiency, it is important to predict the distribution of NPs within blood vessels. NP size, shape and vessel geometry are believed to influence its biodistribution in circulation. Whereas, the effect of size on nanoparticle distribution has been extensively studied, little is known about the shape and vessel geometry effect. This paper describes a computational model for NP transport and distribution in a mimetic branched blood vessel using combined NP Brownian dynamics and continuum fluid mechanics approaches. The simulation results indicate that NPs with smaller size and rod shape have higher binding capabilities as a result of smaller drag force and larger contact area. The binding dynamics of rod-shaped NPs is found to be dependent on their initial contact points and orientations to the wall. Higher concentration of NPs is observed in the bifurcation area compared to the straight section of the branched vessel. Moreover, it is found that Péclet number plays an important role in determining the fraction of NPs deposited in the branched region and the straight section. Simulation results also indicate that NP binding decreases with increased shear rate. Dynamic NP re-distribution from low to high shear rates is observed due to the non-uniform shear stress distribution over the branched channel. This study would provide valuable information for NP distribution in a complex vascular network.

Keywords: Nanoparticle distribution; Péclet number; Shape effect; Vascular network.

Fig. 1

Illustrations of rod and sphere particles: a rod, b sphere, respectively

Fig. 2

A bifurcation microchannel for NP deposition simulation. a Dimensions of the geometry, b the region defined as straight section and bifurcation area

Fig. 3

Trajectory snapshots of a nanosphere (a) and a nanorod (b) under shear flow. The arrows illustrate the adhesive force once the particles interact with the wall

Fig. 4

Normalized binding probability for a NP size of 100 nm; b NP size of 200 nm

Fig. 5

A snap shot of the particle distribution in the branched vessel for a spheres; b rods

Fig. 6

100 nm nanoparticle distribution along the channel. Shear rates at the bifurcation region are a 200 s⁻¹, b 400 s⁻¹, c 800 s⁻¹, d 1,200 s⁻¹, e 2,000 s⁻¹

Fig. 7

Adhesion of NPs depends on particle shape and their orientation. Nanorods have smaller contact area and bonding force during transient rotation, but with maximal bonding force after laying down with long axis aligned with wall

Fig. 8

200 nm nanoparticle distribution along the channel. Shear rates at the bifurcation region are a 200 s⁻¹, b 400 s⁻¹, c 800 s⁻¹, d 1,200 s⁻¹, e 2,000 s⁻¹

Fig. 9

Ratio of the number of deposited NPs on branched region and straight section depends on the Péclet number. The simulation data are fitted by quadratic lines through least square method. a 100 nm NPs; b 200 nm NPs

Fig. 10

100 nm NP distribution along a channel with width of 10 μm (a) and 2 μm (b) with a shear rate of 200 s⁻¹ at the bifurcation