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Microspheres containing radioactive 166holmium-acetylacetonate are employed in emerging radionuclide therapies for the treatment of malignancies. At the molecular level, details on the coordination geometries of the Ho complexes are however elusive. Infrared ion spectroscopy (IRIS) was used to characterize several 165Ho-acetylacetonate complexes derived from non-radioactive microspheres. The coordination geometry of four distinct ionic complexes were fully assigned by comparison of their measured IR spectra with spectra calculated at the density functional theory (DFT) level. The coordination of each acetylacetonate ligand is dependent on the presence of other ligands, revealing an asymmetric chelation motif in some of the complexes. A fifth, previously unknown constituent of the microspheres was identified as a coordination complex containing an acetic acid ligand. These results pave the way for IRIS-based identification of microsphere constituents upon neutron activation of the metal center.

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Pluronics P94 are block-copolymer showing prolonged circulation time and tumor-cell internalization in vitro, suggesting a potential for tumor accumulation and as a drug carrier. Here we report the results of the radiolabeled-P94 unimers (P94-111In-DTPA) on tumor uptake/retention and biodistribution after intravenous and intratumoral injection to tumor-bearing mice. Intravenous administration results in a high radioactive signal in the liver; while in tumor and other healthy tissues only low levels of radioactivity could be measured. In contrast, the intratumoral injection of P94 resulted in elevated levels of radioactivity in the tumor and low levels in other organs, including the liver. Independently from the injection route, the tumor tissue presented long retention of radioactivity. The minimal involvement of off-target tissues of P94, together with the excellent tracer retention over-time in the tumor designates Pluronic P94 copolymer as a highly promising carrier for anti-tumor drugs.

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Chemotherapeutic drugs have multiple drawbacks, including severe side effects and suboptimal therapeutic efficacy. Nanomedicines assist in improving the biodistribution and target accumulation of chemotherapeutic drugs, and are therefore able to enhance the balance between efficacy and toxicity. Multiple types of nanomedicines have been evaluated over the years, including liposomes, polymer-drug conjugates and polymeric micelles, which rely on strategies such as passive targeting, active targeting and triggered release for improved tumor-directed drug delivery. Based on the notion that tumors and metastases are highly heterogeneous, it is important to integrate imaging properties in nanomedicine formulations in order to enable non-invasive and quantitative assessment of targeting efficiency. By allowing for patient pre-selection, such next generation nanotheranostics are useful for facilitating clinical translation and personalizing nanomedicine treatments.

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Lipid based nanoparticles represent a class of nanocarriers that have caused great expectation, particularly due to their suitability to incorporate BCS class II and IV drugs. The use of solid lipid nanoparticles (SLNs) as a nanocarrier for antineoplastic agents has been underexplored when compared to the encapsulation of the same agents in polymeric particles. The preparation and efficacy assessment of a SLN platform as drug delivery carrier for anticancer agents, herein proposed as a strategy to find innovative formulations, could dramatically improve the outcome of cancer therapy. Considering these lipid nanoparticles, despite the great amount of insights described in the literature, it seems that improving their manufacturability could be the missing step to convert this system into a drug product. A way to circumvent that problem would be to select a preparation method that could take advantage of the pharmaceutical industry installed capabilities, thus speeding-up the scale-up translational steps while maintaining both regulatory compliance and flexibility. The High Pressure Homogenization (HPH) has proved to be a reliable process for SLN preparation. However, the use of the high-shear mixer, a well established process to manufacture coarse dispersions at industrial scale, has still not been fully explored to prepare SLN. In this study, we explore the possibility of using the hot emulsification/solidification method to prepare SLN's that complies with the current pharmaceutical quality requirements. Thus, a high-shear based process that consistently accomplishes performance requirements was optimized in order to standardize the nanocarrier production following the identification of some process and formulation critical parameters. A hydrophobic drug, Paclitaxel (Ptx) was successfully incorporated using the proposed developed method. The particles physicochemical characteristics changes caused by the drug entrapment as well as the particles stability were also evaluated. In addition the ability of SLN to travel across biological barriers due to its matrix lipid nature was explored upon comparing the efficacy of the drug loaded SLN with the conventional marketed drug product (Taxol®). The cellular uptake studies showed that the developed Ptx loaded SLN were in fact internalized and demonstrated higher efficacy in the cancer cells death process than Taxol. The experimental data demonstrated that the hot homogenization technique using a high-shear mechanical homogenizer allows the preparation of suitable size (around 150 nm) SLN. Overall, the results obtained can be particularly impactful in the forthcoming SLN research.

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