This project investigated how the intrinsic physicochemical properties of nano-aluminium layered double hydroxides (NA) influence their immunomodulatory mechanisms at cellular and tissue levels. Owing to their mild alkalinity, NA particles effectively neutralize acidic microenvironments. At the cellular level, NA rapidly buffers endosomal acidity and releases magnesium ions that increase ionic strength, facilitating endosomal escape and enabling cytosolic delivery of associated antigens. Once in the cytosol, NA particles engage the autophagy pathway and interfere with the acidification of autophagolysosomes, thereby modulating cellular functions. Because the divalent metal cation in NA can be readily substituted with other metals (e.g. zinc), the immunological properties of NA are strongly influenced by their chemical composition. At the tissue level, NA neutralizes extracellular acidity and reshapes the functional state of local immune cells, including CD8⁺ T cells and macrophages.
1. Metal composition of NA regulates dendritic cell antigen presentation.
This project demonstrated that modifying the metal composition of NA markedly alters dendritic cell (DC) activation. By partially or fully substituting magnesium ions with zinc ions to produce zinc-modified NA (ZNA), we observed enhanced DC maturation and activation with increasing zinc content. Mechanistic studies showed that conventional NA primarily inhibits autophagy, whereas the incorporation of zinc ions restores and enhances autophagic flux. This enhancement promotes more efficient antigen cross-presentation, thereby strengthening both humoral responses and CD8⁺ T-cell immunity.
2. Magnesium ions released from NA modulate macrophage inflammatory responses.
We found that magnesium ions liberated from NA exert a notable anti-inflammatory effect on macrophages. In inflamed liver and lung tissues, NA uptake significantly increased intracellular magnesium levels, driving macrophages toward an anti-inflammatory phenotype and reducing local tissue inflammation. This effect is mediated largely through activation of the SIRT1/Nrf2 signalling pathway by released magnesium ions.
3. NA enhances CD8⁺ T-cell function by restoring cellular mechanics and signalling.
A key discovery of this project is that NA directly influences CD8⁺ T-cell activation by modifying cell biomechanical properties. Acidic microenvironments were found to stiffen CD8⁺ T cells and impair their cytotoxic function. NA-mediated neutralization of extracellular acidity effectively restored T-cell softness and improved effector activity. Furthermore, magnesium ions released from NA interacted with the LFA-1 receptor on CD8⁺ T cells, enhancing cytotoxic function via the calcium–NFAT2–IFN signalling pathway. While magnesium alone had a moderate activating effect, its combination with interleukin-12 (IL-12) proved particularly beneficial: magnesium ions mitigated cytokine-induced exhaustion and preserved the functional fitness of CD8⁺ T cells under strong stimulatory conditions.
