99mTc-Radiolabeled TPGS Nanomicelles Outperform 99mTc-Sestamibi as Breast Cancer Imaging Agent

99mTc radiolabeling of polyethylenimine capped carbon dots for tumor targeting: synthesis, characterization and biodistribution

PURPOSE

Due to the favorable physicochemical properties and the biocompatibility, carbon dots (CDs) have gained a great attention as a tumor targeting agent. This study investigates polyethylenimine capped CDs (PEI capped CDs) as a prospective nanocarrier of technetium-99m (^99mTc) for tumor targeting. Technetium-labeled CDs could be introduced as a promising candidate for single photon emission tomography (SPECT) imaging.

MATERIALS AND METHODS

Polyethylenimine capped CDs were prepared by hydrothermal method using hyperbranched PEI and citric acid. For a purpose of comparison, citrate capped CDs were also prepared by microwave irradiation. Both types of CDs were characterized and radiolabeled with ^99mTc using sodium borohydride (NaBH₄) as a reducing agent. Biodistribution and tumor targeting efficiency of the produced radiolabeled CDs have been studied in Earlich ascites tumor mice model.

RESULTS

Citrate capped CDs and PEI capped CDs have been synthesized successfully and characterized. High radiochemical yield of ^99mTc-citrate capped CDs ^99mTc-PEI capped CDs was obtained (97 ± 0.7 and 90 ± 0.2, respectively). Biodistribution studies of ^99mTc-labeled PEI capped CDs have shown a potential tumor uptake (10 ± 0.5% Radioactivity/gram tumor) with high target to non-target ratio (T/NT) around 7 at 1-h post injection. ^99mTc-citrate capped CDs have achieved a lower tumor uptake level (3.8 ± 0.3% Radioactivity/gram tumor 1 h post injection).

CONCLUSION

This study introduces PEI capped CDs as a promising nanocarrier of ^99mTc for efficient tumor targeting. Technetium-labeled PEI capped CDs could be utilized as a potential SPECT tumor imaging agent.

Radiolabelling of nanomaterials for medical imaging and therapy

Nanomaterials offer unique physical, chemical and biological properties of interest for medical imaging and therapy. Over the last two decades, there has been an increasing effort to translate nanomaterial-based medicinal products (so-called nanomedicines) into clinical practice and, although multiple nanoparticle-based formulations are clinically available, there is still a disparity between the number of pre-clinical products and those that reach clinical approval. To facilitate the efficient clinical translation of nanomedicinal-drugs, it is important to study their whole-body biodistribution and pharmacokinetics from the early stages of their development. Integrating this knowledge with that of their therapeutic profile and/or toxicity should provide a powerful combination to efficiently inform nanomedicine trials and allow early selection of the most promising candidates. In this context, radiolabelling nanomaterials allows whole-body and non-invasive in vivo tracking by the sensitive clinical imaging techniques positron emission tomography (PET), and single photon emission computed tomography (SPECT). Furthermore, certain radionuclides with specific nuclear emissions can elicit therapeutic effects by themselves, leading to radionuclide-based therapy. To ensure robust information during the development of nanomaterials for PET/SPECT imaging and/or radionuclide therapy, selection of the most appropriate radiolabelling method and knowledge of its limitations are critical. Different radiolabelling strategies are available depending on the type of material, the radionuclide and/or the final application. In this review we describe the different radiolabelling strategies currently available, with a critical vision over their advantages and disadvantages. The final aim is to review the most relevant and up-to-date knowledge available in this field, and support the efficient clinical translation of future nanomedicinal products for in vivo imaging and/or therapy.

Rebaudioside A/TPGS mixed nanomicelles as promising nanocarriers for nimodipine ocular delivery

Nimodipine (NMD), a calcium channel blocker, has demonstrated benefits in treating glaucoma. However, its ocular therapeutic application remains limited due to its poor aqueous solubility, which restrains the development of an ophthalmic formulation. Thus, the present study aimed to formulate an NMD micelle ophthalmic solution to enhance the potential of NMD in an ocular topical formulation to treat glaucoma. The NMD micelle ophthalmic solution was formulated with nanocarriers composed of rebaudioside A and D-α-tocopheryl polyethylene glycol 1000 succinate. Spherical mixed micelles were optimized and obtained at a small micelle size 13.429 ± 0.181 nm with a narrow size distribution (polydispersity index 0.166 ± 0.023) and high encapsulation efficiency rate (99.59 ± 0.09%). Compared with free NMD, NMD in micelles had much greater in vitro membrane permeability and antioxidant activity. The NMD micelle ophthalmic solution was well tolerated in rabbit eyes. It profoundly improved the in vivo intraocular permeation of NMD, and in vivo intraocular pressure reduction and improved miosis were also observed. Accordingly, this NMD micelle ophthalmic solution might be a promising ocular formulation to treat glaucoma. Graphical abstract.