MO‐D‐141‐07: X‐Ray Activated Gold Nanoparticles for Tumor‐Specific Molecular Imaging

Abstract

Purpose: X‐ray radiography and computed tomography are commonly used anatomical imaging modalities still have significant shortcomings in sensitivity and specificity. Molecular imaging based on tumor‐specific nanoparticles that can probe biochemical processes in vivo can provide characterization and identification of benign and malignant lesions on the cellular level. In particular, radioluminescent nanoparticles (RLNPs) are the ideal platform for X‐ray‐mediated imaging and synergistic therapy during radiation treatment. These unique particles can emit visible light under X‐ray irradiation. However, existing RLNPs based on lanthanides may cause toxicity in vivo. Here we report new intriguing radioluminescent properties of a new type of nanoparticles made by arranging a small number of gold atoms. The objective of this work is to examine practical aspects of a new imaging modality: light emission and spectral emission characteristics. Methods: Bare gold nanoparticles (4 and 1.8 nm) and conjugated gold nanoparticles with size less than 2 nm (25 atoms size) were synthesized. Imaging was performed by irradiating the samples with X‐ray (30–80 kVp, 10–30 mA) while acquiring 10 s frames with an EMCCD camera (Princeton Instruments, 300–900 nm). The samples were further characterized by using a custom PMT‐based system. The spectral properties of the emission were measured under both optical and X‐ray excitation using a sensitive spectrometer. Results: It was found that tested gold nanoparticles had different responses to x‐ray excitation. Au25‐BSA is the most promising candidate for x‐ray luminescence imaging, with up to 4‐6‐fold increase in the optical signal compared to the controls. Conclusion: In this work, it was first time demonstrated the optical detection of small atom number gold nanoparticles excited by x‐ray source. Development of a new optical imaging probes will allow us to take advantage of the desirable features of optical molecular imaging and achieve substantially improved spatiotemporal resolution, sensitivity and specificity for tumor detection.