Arginine–glycine–aspartate (RGD)-targeted positron-labeled dendritic polylysine nanoprobe for tumor PET imaging

This work investigated the optimization of the ⁶⁸Ga radiolabeling of the dendritic polylysine-1,4,7-triazacyclononane-1,4,7-triacetic acid conjugate (DGL-NOTA). Under pH = 4.0, reaction temperature of 70 °C, and incubation time of 10.0 min, the conjugate (DGL-NOTA) radiochemical yield was between 50% and 70%. After separation and purification, the radiochemical purity was greater than 98%. The radiolabeled formulation (⁶⁸Ga-NOTA-DGL-PEG-RGDyC) remained stable in both phosphate buffer and serum (all radiochemically greater than 95%) for up to 2 hours with a specific activity of 30 GBq/μmol. Cellular experimental studies have shown that radiolabeled preparations can rapidly enter U87MG cells, and after 2 hours, there was still retention of imaging agents in the cells. In vivo distribution studies had shown that the tracer is excreted by the kidneys. Two hours after injecting the imaging agent, the U87MG tumor tissue uptake value was (4.67 ± 0.09)% ID/g. Positron emission tomography (PET) imaging in animals showed that ⁶⁸Ga-NOTA-DGL-PEG-RGDyC had good targeting and can be enriched in tumor sites. Through hemolysis testing and morphological changes of red blood cells, it was proved that NOTA-DGL-PEG-RGDyC has good blood compatibility.

This work investigated the optimization of the ⁶⁸Ga radiolabeling of the dendritic polylysine-1,4,7-triazacyclononane-1,4,7-triacetic acid conjugate (DGL-NOTA).

Anti-prostate cancer activity of 8-hydroxyquinoline-2-carboxaldehyde-thiosemicarbazide copper complexes in vivo by bioluminescence imaging

Copper 8-hydroxyquinoline-2-carboxaldehyde-thiosemicarbazide complex (CuHQTS) is a copper complex with strong anticancer activity against cisplatin-resistant neuroblastoma and prostate cancer cells in vitro by cell proliferation assay or fluorescent microscopic imaging. This study aimed to evaluate anti-prostate cancer activity of CuHQTS in vivo by bioluminescence imaging (BLI) and tumor size measurement, using athymic nu/nu mice implanted with prostate cancer cells carrying luciferase reporter gene (Luc-PC3). Growth of Luc-PC3 cells (1 × 10⁵ cells) implanted in athymic nu/nu mice treated with CuHQTS for 2 weeks was suppressed by measurement of luciferase signals (6.18 × 10⁷ to 5.36 × 10⁷ p/s/cm²/sr) with BLI, compared with luciferase signals of Luc-PC3 cells (4.66 × 10⁷ to 1.51 × 10⁸ p/s/cm²/sr, p < 0.05) in the mice treated with normal saline of placebo control. Moreover, the size of PC-3 xenograft tumor (126.5 ± 34.2 mm³) in athymic nu/nu mice treated with CuHQTS was significantly smaller than the size of PC-3 xenograft tumor (218.6 ± 48.0 mm³, p < 0.05) in athymic nu/nu mice treated with normal saline of placebo control, suggesting in vivo tumor growth inhibition activity of CuHQTS on prostate cancer. The findings of this study support further investigation of CuHQTS as a promising new anticancer agent for the treatment of metastatic prostate cancer refractory to anticancer drugs currently available.

Dual passively active tumor-targeting micelles for pH-triggered intracellular anticancer drug release

Novel passive–active dual tumor-targeting micelles for pH-triggered intracellular nitrogen mustard release were developed based on hydrophobic cores conjugated with anticancer drugs and shells functionalized with folic acid ligands for tumor cell targeting. The amphiphilic triblock copolymer, 4-( bis(2-chloroethyl)amino)benzaldehyde, N-(2-hydroxypropyl)methacrylamide, and folic acid copolymer (poly(mustard-acetal)- b-PHPMA- b-PFA), was synthesized via reversible addition fragmentation chain transfer polymerization. The amphiphilic copolymer was subsequently self-assembled into nanosized micelles of 83 nm with the nitrogen mustard drug safely encapsulated in the core. The cleavage of anticancer drug within the cores of micelles was effectively actuated under biologically relevant conditions, mildly acidic microenvironments (endosomal/lysosomal pH in the cytosol). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and fluorescence microscopy image analysis revealed that folate-conjugated nanosized micelles exhibited at least ~2.2-fold higher cellular uptake than folate unconjugated micelles against KB cells overexpressing folate receptors on the surface. Thus, poly(mustard-acetal)- b-PHPMA- b-PFA micelles could potentially be used as a promising system for triggering the release of nitrogen mustard drug.

Brachytherapy using injectable seeds that are self-assembled from genetically encoded polypeptides in situ

Brachytherapy is a common clinical technique involving implantation of sealed radioactive "seeds" within a tumor to selectively irradiate the tumor mass while minimizing systemic toxicity. To mitigate the disadvantages associated with complex surgical implantation and subsequent device removal procedures, we have developed an alternative approach using a genetically encoded peptide polymer solution composed of a thermally responsive elastin-like polypeptide (ELP) radiolabeled with (131)I that self-assembles into radionuclide seeds upon intratumoral injection. The formation of these nontoxic and biodegradable polymer seeds led to prolonged intratumoral retention (~85% ID/tumor 7 days postinjection) of the radionuclide, elicited a tumor growth delay in 100% of the tumors in two human xenografts (FaDu and PC-3), and cured more than 67% of tumor-bearing animals after a single administration of labeled ELP. These results suggest that in situ self-assembly of biodegradable and injectable radionuclide-containing polypeptide seeds could be a promising therapeutic alternative to conventional brachytherapy.