Antibody Conjugation of Fluorescent Nanodiamonds for Targeted Innate Immune Cell Activation

[Image: see text] Background: fluorescent nanodiamonds (FND) are nontoxic, infinitely photostable nanoparticles that emit near-infrared fluorescence and have a modifiable surface allowing for the generation of protein–FND conjugates. FND-mediated immune cell targeting may serve as a strategy to visualize immune cells and promote immune cell activation. Methods: uncoated-FND (uFND) were fabricated, coated with glycidol (gFND), and conjugated with immunoglobulin G (IgG–gFND). In vitro studies were performed using a breast cancer/natural killer/monocyte co-culture system, and in vivo studies were performed using a breast cancer mouse model. Results: in vitro studies demonstrated the targeted immune cell uptake of IgG–gFND, resulting in significant immune cell activation and no compromise in immune cell viability. IgG–gFND remained at the tumor site following intratumoral injection compared to uFND which migrated to the liver and kidneys. Conclusion: antibody-conjugated FND may serve as immune drug delivery vehicles with “track and trace capabilities” to promote directed antitumor activity and minimize systemic toxicities.