T lymphocytes dominate local leukocyte infiltration in response to intradermal injection of functionalized...

Graphene-based nanomaterials (GBN) have many potential biomedical applications. However, information regarding their biological properties and interactions with cells and/or soluble factors within a complex tissue is limited. The objective of this study was to use the growing feather (GF) of chickens as a minimally invasive cutaneous test-site to assess and monitor leukocyte recruitment in response to intradermal GBN injection. Specifically, the dermis of 20 GFs per chicken was injected with 10 μl of phosphate-buffered saline (PBS)-vehicle or 10 μl of 300 μg ml^-1 oxygen-functionalized (f) GBN (6 chickens/treatment). GFs were collected before- (0) and at 0.25, 1, 2, 3, 4, 5, and 7 days post-injection and used for leukocyte-population analysis of immunofluorescently stained pulp cell suspensions or histological examination. Based on flow-cytometric cell population analysis, lymphocytes and macrophages were the major leukocyte-populations infiltrating GFs in response to f-GBN presence. Compared with PBS-controls, levels of T cells (γδ-, αβ-, CD4- and CD8-T cells) were greatly elevated in f-GBN-injected GFs within 6 h and remained elevated throughout the 7-day examination period. f-GBN's effects on local tissue leukocyte recruitment were not reflected in the blood, except for a higher percentage of lymphocytes on 7 days. These observations together with a visual examination of f-GBN-injected GF tissue-sections suggest a delayed-type hypersensitivity-like, inflammatory cell-mediated response to the non-biodegradable f-GBN. The GF 'in vivo test-tube'system together with blood sampling provided unique insight into the time-course, qualitative, and quantitative aspects of immune system activities initiated by the presence of f-GBN in a complex tissue of a living animal. Copyright © 2017 John Wiley & Sons, Ltd.