Fullerenes also exhibit immunomodulation properties through the release of cytokines by bovine alveolar macrophages.133 A study explored the influence of functionalization of C60 with molecules presenting different surface charges like hydroxyl groups and amino acids.134 The study concluded that negative charges upregulated TNF-α up-secretion in RAW 264.7 macrophages, but highly positively or negatively charged surfaces increased cell toxicity.