# Nano(bio)Materials Do Not Affect Macrophage Phenotype—A Study Conducted by the REFINE Project

## TL;DR

This study shows that nano(bio)materials do not change macrophage behavior, using a standardized method to differentiate human monocytes into macrophages.

## Contribution

A standardized procedure for differentiating human monocytes into macrophages to study nano(bio)material interactions was developed and validated.

## Key findings

- The standard operating procedure for macrophage differentiation produced consistent results across two institutions.
- Nano(bio)materials did not significantly alter the phenotype of M1 or M2 macrophages.
- Donor variability in macrophage responses was observed, reflecting in vivo heterogeneity.

## Abstract

Macrophages are well known for their involvement in the biocompatibility, as well as biodistribution, of nano(bio)materials. Although there are a number of rodent cell lines, they may not fully recapitulate primary cell responses, particularly those of human cells. Isolation of tissue-resident macrophages from humans is difficult and may result in insufficient cells with which to determine the possible interaction with nano(bio)materials. Isolation of primary human monocytes and differentiation to monocyte-derived macrophages may provide a useful tool with which to further study these interactions. To that end, we developed a standard operating procedure for this differentiation, as part of the Regulatory Science Framework for Nano(bio)material-based Medical Products and Devices (REFINE) project, and used it to measure the secretion of bioactive molecules from M1 and M2 differentiated monocytes in response to model nano(bio)materials, following an initial assessment of pyrogenic contamination, which may confound potential observations. The SOP was deployed in two partner institutions with broadly similar results. The work presented here shows the utility of this assay but highlights the relevance of donor variability in responses to nano(bio)materials. Whilst donor variability can provide some logistical challenges to the application of such assays, this variability is much closer to the heterogeneous cells that are present in vivo, compared to homogeneous non-human cell lines.