Injectable nanomaterials that interact with host tissue presents an attractive platform to actively engage resident cell populations. Nanomaterials that have a high aspect ratio, i.e. are asymmetric, allow a cell to generate a bending moment and interact with the nanostructure as a mechanical cue. We first demonstrate a facile fabrication strategy to generate high yield of these nanowires made from polycaprolactone with aspect ratios of up to 100 with simple benchtop equipment via a melt templating technique using anodized alumina as a mold material. When cultured with 3T3 fibroblasts in vitro, we observed no differences in proliferation and apoptosis of these cells compared to cells grown in the absence of these structures. We observed a marked decrease in expression levels of key fibroblast activation markers such as Collagen 1 and TGFβ as well as a phenotypic deviation from myofibroblast morphology.
Given their compatibility in vitro, we explored whether these same systems could serve as an ideal platform to present long-term, spatially confined biological signaling to surrounding immune cells when used in vivo. When coupled with cytokine-binding antibodies, these nanowires assemble into porous matrices when injected into the subcutaneous space. These scaffolds then accumulate and sequester their target cytokine inside this nodule, and by judicious choice of antibody binding site, can provide exquisite cellular specificity and activation by means of locally concentrating and potentiating these signaling proteins.
Nanowires were found to be well tolerated in vivo and incite minimal macrophage mediated foreign body response. Nanowires conjugated with antibodies were designed to capture endogenous interleukin-2 (IL-2), an important leukocyte activating cytokine. As a proof of concept, we first explored how these nanowire-antibody conjugates could potentiate a specific subset of CD25- cells, and showed that not only were we able to see cellular specificity by means of which antibody is present, but also achieved tissue level specificity – i.e. limiting off target tissue effects that were seen when antibody was injected without being conjugated to the nanowire matrix.
These self-assembling nanowire matrices show promise as scaffolds to present engineered, local receptor-ligand interactions for cytokine mediated disease. We demonstrated how an orthogonal antibody that activates CD25+ cells, primarily regulatory T cells, could rebalance the local immune compartment during an inflammatory disease event in a transgenic model of autoimmune disease in the skin. We observed decreased effector T cell activity and improved regulatory T cell function as well as tissue level improvements such as a significant decrease in plaque formation local to injection sites.
