# Delivery of siRNA and Chloroquine Through an Aspherical, Nanostructured Microparticle for Passive Targeting of Alveolar Macrophages and Inhibition of Local TNF-α Secretion

## TL;DR

Researchers developed a microparticle system to target alveolar macrophages and reduce inflammation by inhibiting TNF-α secretion.

## Contribution

A novel inhalable microparticle system was created for passive targeting of siRNA and chloroquine to inhibit TNF-α in lung macrophages.

## Key findings

- The microparticle system showed suitable aerodynamic properties for lung delivery with a MMAD of 3.37 µm.
- The system demonstrated slow disintegration, low toxicity, and high uptake by macrophage-like cells.
- Incorporating chloroquine significantly enhanced the siRNA's inhibitory effect on TNF-α secretion.

## Abstract

Background/Objectives: Alveolar macrophages represent the main path of defense in the peripheral pulmonary tissue, though their role in chronic inflammatory lung diseases shows that their protective function can turn pathological. This study focused on developing a system to passively target the release of the pro-inflammatory cytokine TNF-α through the local delivery of siRNA. Methods: An inhalable aspherical microparticle made up of mesoporous silica nanoparticles, crosslinked by an electrostatic LbL-system embedding the siRNA, was developed. Results: Through testing with the NGI, adequate aerodynamic properties with an MMAD as low as 3.37 µm could be determined, with a GSD as low as 1.46, suggesting a relatively small size distribution even during inhalation. To further understand the interaction of the microrods with the lung parenchyma and the resident cells, the disintegration of the rods in different simulant body fluids, their toxicity, and the cell uptake through dTHP-1 and A549 were observed. This showed slow but continuous disintegration, no toxicity in A549 cells, and high microrod uptake by dTHP-1 cells. To demonstrate the effect of the delivered siRNA on the release of TNF-α, ELISAs were carried out, establishing an inhibitory effect of the siRNA-carrying microcarrier system compared to those without siRNA or loaded with scrambled siRNA. To increase the efficacy of the siRNA, chloroquine as an endosomal escape-enhancing compound was loaded onto the mesoporous silica nanoparticles. This resulted in a significant improvement in siRNA inhibition. Conclusions: The developed formulation is able to reach the targeted structure and inhibit the secretion of TNF-α, with CQ increasing the inhibitory effect of the siRNA.