Gold nanoparticles, especially positron-emitter- labeled gold nanostructures, have gained steadily increasing attention in biomedical applications. Of the radionuclides used for nanoparticle positron emission tomography imaging, radiometals such as (64) Cu have been widely employed. Currently, radiolabeling through macrocyclic chelators is the most commonly used strategy. However, the radiolabel stability may be a limiting factor for further translational research. We report the integration of (64) Cu into the structures of gold nanoparticles. With this approach, the specific radioactivity of the alloyed gold nanoparticles could be freely and precisely controlled by the addition of the precursor (64) CuCl2 to afford sensitive detection. The direct incorporation of (64) Cu into the lattice of the gold nanoparticle structure ensured the radiolabel stability for accurate localization in vivo. The superior pharmacokinetic and positron emission tomography imaging capabilities demonstrate high passive tumor targeting and contrast ratios in a mouse breast cancer model, as well as the great potential of this unique alloyed nanostructure for preclinical and translational imaging.

Gold nanoparticles have been widely used for oncological applications including diagnosis and therapy. However, the non-specific mononuclear phagocyte system accumulation and potential long-term toxicity have significantly limited clinical translation. One strategy to overcome these shortcomings is to reduce the size of gold nanoparticles to allow renal clearance. Herein, we report the preparation of (64)Cu alloyed gold nanoclusters ((64)CuAuNCs) for in vivo evaluation of pharmacokinetics, systemic clearance, and positron emission tomography (PET) imaging in a mouse prostate cancer model. The facile synthesis in acqueous solution allowed precisely controlled (64)Cu incorporation for high radiolabeling specific activity and stability for sensitive and accurate detection. Through surface pegylation with 350 Da polyethylene glycol (PEG), the (64)CuAuNCs-PEG350 afforded optimal biodistribution and significant renal and hepatobiliary excretion. PET imaging showed low non-specific tumor uptake, indicating its potential for active targeting of clinically relevant biomarkers in tumor and metastatic organs.

As an emerging class of nanomaterial, nanoclusters hold great potential for biomedical applications due to their unique sizes and related properties. Herein, we prepared a 64Cu doped gold nanoclusters (64CuAuNCs, hydrodynamic size: 4.2 ± 0.5 nm) functionalized with AMD3100 or (Plerixafor) for targeted positron emission tomography (PET) imaging of CXCR4, an up-regulated receptor on primary tumor and lung metastasis in a mouse 4T1 orthotopic breast cancer model. We prepared a targeted 64CuAuNCs-AMD3100 (4.5 ± 0.4 nm) via one-step reaction with controlled conjugation of AMD3100 and specific activity, as well as improved colloid stability. In vivo pharmacokinetic evaluation showed favorable organ distribution and significant renal and fecal clearance within 48 h post injection. The expression of CXCR4 in tumors and metastasis was characterized by immunohistochemistry, western blot, and reverse transcription polymerase chain reaction analysis. PET imaging with 64CuAuNCs-AMD3100 demonstrated sensitive and accurate detection of CXCR4 in engineered tumors expressing various levels of the receptor while competitive receptor blocking studies confirmed targeting specificity of the nanoclusters. In contrast to non-targeted 64CuAuNCs and 64Cu-AMD3100 alone, the targeted 64CuAuNCs-AMD3100 detected up-regulated CXCR4 in early-stage tumors and pre-metastatic niche of lung earlier and with greater sensitivity. Taken together, we believe that 64CuAuNCs-AMD3100 could serve as a useful platform for early and accurate detection of breast cancer and metastasis providing an essential tool to guide the treatment.

Inflammation plays important roles at all stages of atherosclerosis. Chemokine systems have major effects on the initiation and progression of atherosclerosis by controlling the trafficking of inflammatory cells in vivo through interaction with their receptors. Chemokine receptor 5 (CCR5) has been reported to be an active participant in the late stage of atherosclerosis and has the potential as a prognostic biomarker for plaque stability. However, its diagnostic potential has not yet been explored. The purpose of this study was to develop a targeted nanoparticle for sensitive and specific PET/CT imaging of the CCR5 receptor in an apolipoprotein E knock-out (ApoE−/−) mouse vascular injury model. Methods The D-Ala1-peptide T-amide (DAPTA) peptide was selected as a targeting ligand for the CCR5 receptor. Through controlled conjugation and polymerization, a biocompatible poly(methyl methacrylate)-core/polyethylene glycol-shell amphiphilic comblike nanoparticle was prepared and labeled with 64Cu for CCR5 imaging in the ApoE−/− wire-injury model. Immunohistochemistry, histology, and real-time reverse transcription polymerase chain reaction (RT-PCR) were performed to assess the disease progression and upregulation of CCR5 receptor. Results The 64Cu-DOTA-DAPTA tracer showed specific PET imaging of CCR5 in the ApoE−/− mice. The targeted 64Cu-DOTA-DAPTA-comb nanoparticles showed extended blood signal and optimized biodistribution. The tracer uptake analysis showed significantly higher accumulations at the injury lesions than those acquired from the sham-operated sites. The competitive PET receptor blocking studies confirmed the CCR5 receptor–specific uptake. The assessment of 64Cu-DOTA-DAPTA-comb in C57BL/6 mice and 64Cu-DOTA-comb in ApoE−/− mice verified low nonspecific nanoparticle uptake. Histology, immunohistochemistry, and RT-PCR analyses verified the upregulation of CCR5 in the progressive atherosclerosis model. Conclusion This work provides a nanoplatform for sensitive and specific detection of CCR5’s physiologic functions in an animal atherosclerosis model.

Rationale: Paradigm shifting studies have revealed that the heart contains functionally diverse populations of macrophages derived from distinct embryonic and adult hematopoietic progenitors. Under steady state conditions, the heart is largely populated by CCR2-macrophages of embryonic descent. Following tissue injury, a dramatic shift in macrophage composition occurs whereby CCR2+ monocytes are recruited to the heart and differentiate into inflammatory CCR2+ macrophages that contribute to heart failure progression. Currently, there are no techniques to