Intracellular Photoacoustic Imaging Using Folate Receptor Targeting Gold Nanorods

Objective Molecular imaging technology has the characteristic of "early detection", since aberrations at molecular levels occur much earlier than the changes at the anatomical level. In this study, intracellular photoacoustic molecular imaging (PMI) method was used to map the folic-acid-conjugated gold nanorods (FA-AuNRs) targeted on cancer cells. Methods We synthesized the FA-AuNRs and studied their properties including morphology, absorption spectrum, and biocompatibility. The conjugated folic acid has endowed the FA-AuNRs with the ability to target folate-receptor-expressing cancer cells. Then, PMI experiment was performed to study the target specificity of FA-AuNRs on cancer cells. Results FA-AuNRs were rod-shaped with a near-infrared absorption peak at similar to 800 nm. We observed the strong photoacoustic signals in the cytoplasm of cancer cells, while weak photoacoustic signals in the normal cells, indicating the selective uptake of FA-AuNRs inside cancer cells via folate-receptormediated endocytosis. The study demonstrated the ability of PMI to precisely map the FA-AuNRs targeted on cancer cells. Conclusion With the aid of specific targeting, information about the surface molecules of cancer cells can be obtained by PMI. This method is expected to visualize, characterize and quantify biological processes at cellular and molecular levels.