Gold-enhanced brachytherapy by a nanoparticle-releasing hydrogel and 3d-printed subcutaneous radioactive implant approach

Brachytherapy (BT) is a widely used clinical procedure for localized cervical cancer treatment. In addition, gold nanoparticles (AuNPs) have been demonstrated as powerful radiosensitizers in BT procedures. Prior to irradiation by a BT device, their delivery to tumors can enhance the radiation effect by generating low-energy photons and electrons, leading to reactive oxygen species (ROS) production, lethal to cells. No efficient delivery system has been proposed until now for AuNP topical delivery to localized cervical cancer in the context of BT. This article reports an original approach developed to accelerate the preclinical studies of AuNP-enhanced BT procedures. First, a AuNP-containing hydrogel (Pluronic F127, alginate) is developed and tested in mice for degradation, AuNP release, and biocompatibility. Then, custom-made 3D-printed radioactive BT inserts covered with a AuNP-containing hydrogel cushion are designed and administered by surgery in mice (HeLa xenografts), which allows measuring AuNP penetration in tumors (~100 m), co-registered with the presence of ROS produced through the interactions of radiation and AuNPs. Overall, the application of a biocompatible AuNPs-releasing hydrogel in the vicinity of cervical cancer prior to BT could decrease the total amount of radiation needed per BT treatment, with benefits on the preservation of healthy tissues surrounding cancer

A 3D-printable hydrogel formulation for the local delivery of therapeutic nanoparticles to cervical cancer

Cervical cancer is the fourth most common malignancy among women. Compared to other types of cancer, therapeutic agents can be administrated locally at the mucosal vaginal membrane. Thermosensitive gels have been developed over the years for contraception, or for the treatment of bacterial, fungal, and sexually transmitted infections. These formulations often carry therapeutic nanoparticles and are now being considered in the arsenal of tools for oncology. They can also be 3D-printed for a better geometrical adjustment to the anatomy of the patient, thus enhancing the local delivery treatment. In this study, a localized delivery system composed of a Pluronic F127-alginate hydrogel with efficient nanoparticle (NP) release properties was prepared for intravaginal application procedures. The kinetics of hydrogel degradation and its NP releasing properties were demonstrated with ultra-small gold nanoparticles (~80% of encapsulated AuNPs released in 48 h). The mucoadhesive properties of the hydrogel formulation were assayed by the periodic acid/Schiff’s reagent staining, which revealed that 19% of mucins were adsorbed on the gel’s surface. The hydrogel formulation was tested for cytocompatibility in three cell lines (HeLa, CRL 2616, and BT-474; no sign of cytotoxicity revealed). The release of AuNPs from the hydrogel and their accumulation in vaginal membranes were quantitatively measured in vitro/ex vivo with positron emission tomography (PET), a highly sensitive imaging modality allowing real-time imaging of nanoparticle diffusion (lag time to start of permeation 3.3 h, 47% of AuNPs accumulated in the mucosa after 42 h). Finally, the potential of the AuNPs-containing Pluronic F127-alginate hydrogel for 3D-printing was demonstrated, and the geometrical precision of the 3D-printed systems was measured by magnetic resonance imaging (MRI, <0.5 mm precision; deviation from the design values <2.5%). In summary, this study demonstrates the potential of Pluronic F127-alginate formulations for the topical administration of NP-releasing gels applied to vaginal wall therapy. This technology could open new possibilities for photothermal and radiosensitizing oncology applications

Methane dry reforming over Ni catalysts supported on Ce–Zr oxides prepared by a route involving supercritical fluids

Ce0.5Zr0.5O2 mixed oxides were prepared in a flow reactor in supercritical isopropanol with acetylacetone as a complexing agent. Variation of the nature of the Zr salt and the temperature of synthesis affected the phase composition, morphology and specific surface area of oxides. X-ray diffraction and Raman spectroscopy studies revealed formation of metastable t” and t’ phases. Oxides are comprised of agglomerates with sizes depending on the synthesis parameters. Loading NiO decreases the specific surface area without affecting X-ray particle sizes of supports. Such sintering was the most pronounced for a support with the highest specific surface area, which resulted in the lowest surface content of Ni as estimated by X-ray photoelectron spectroscopy and in the formation of flattened NiO particles partially embedded into the support. The catalytic activity and stability of these samples in the dry reforming of methane were determined by the surface concentration of Ni and the morphology of its particle controlled by the metal-support interaction, which also depends on the type of catalyst pretreatment. Samples based on ceria-zirconia oxides prepared under these conditions provide a higher specific catalytic activity as compared with the traditional Pechini route, which makes them promising for the practical application

Synthesis and biological evaluation of (18)F-labeled fluoropropyl tryptophan analogs as potential PET probes for tumor imaging

In the search for an efficient, fluorine-18 labeled amino acid based radiotracer for tumor imaging with positron emission tomography (PET), two new tryptophan analogs were synthesized and characterized in vitro and in vivo. Both are tryptophan alkyl-derivatives, namely 2-(3-[(18)F]fluoropropyl)-dl-tryptophan ([(18)F]2-FPTRP) and 5-(3-[(18)F]fluoro-propyl)-dl-tryptophan ([(18)F]5-FPTRP). Standard reference compounds and precursors were prepared by multi step approaches. Radiosynthesis was achieved by no-carrier-added nucleophilic [(18)F]fluorination in 29-34% decay corrected yields with radiochemical purity over 99%. In vitro cell uptake assays showed that both compounds are substrates for amino acid transport and enter small cell lung cancer cells (NCI-H69) most probably almost exclusively via large neutral amino acids transporter(s) (LAT). Small animal PET imaging with xenograft bearing mice revealed high tumor/background ratios for [(18)F]2-FPTRP comparable to the well established tyrosine analog O-(2-[(18)F]fluroethyl)-l-tyrosine ([(18)F]FET). Radiometabolite studies showed no evidence of involvement of a biotransformation step in tumor accumulation

Synthesis and pharmacological evaluation of 11C-labeled piperazine derivative as a PET probe for sigma-2 receptor imaging

Introduction: Both subtypes of sigma (σ) receptors, σ1 and σ2, are over-expressed in many cancers with σ2 proposed as a biomarker of tumor proliferation. We are interested in developing a high affinity selective σ2 radioligand for in vivo monitoring of proliferative status of solid tumors and response to anti-cancer therapies. 1-Cyclohexyl-4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]piperazine (PB28) represents one of the lead candidates in the development of σ receptor ligands for therapeutic and diagnostic applications. However, the utility of PB28 is limited due to its relatively high lipophilicity. Methods: A more hydrophilic analogue (–)-(S)-1was radiolabeledwith 11C via standard O-alkylation. In vitro autoradiography with [11C](–)-(S)-1 was done using rat brain slices. PET imaging was performed in mice bearing EMT6, C6 or PC-3 tumors after i.v. injection of [11C](–)-(S)-1. Results: [11C](–)-(S)-1 was produced in 53% ± 7% isolated decay-corrected yield with radiochemical and chemical purity over 99% and specific activity greater than 100 GBq/μmol. In vitro autoradiography with [11C(–)-(S)-1 resulted in a heterogeneous binding of the tracer in the rat brain with the highest radioactivity signals in the cortex region followed by cerebellum. This binding was successfully blocked by 10 μM of either haloperidol, (+)- (R)-1 or PB28. For C6 xenografts low target-to-nontarget ratio and high non-specific binding did not allow clear tumor visualization. No accumulation was visible in EMT6 tumor or in PC-3 tumor. Rat and mouse brain uptake was low and homogeneous while stronger signal was detected in the spinal cord. High accumulation of radioactivity was observed in liver and intestine suggesting hepatobiliary clearance. Conclusions: Despite excellent in vitro properties, [11C](–)-(S)-1 did not provide high enough specific binding in vivo and is, therefore, not a useful PET tracer for imaging σ2 expression in tumor

Gene expression levels of matrix metalloproteinases in human atherosclerotic plaques and evaluation of radiolabeled inhibitors as imaging agents for plaque vulnerability.

INTRODUCTION Atherosclerotic plaque rupture is the primary cause for myocardial infarction and stroke. During plaque progression macrophages and mast cells secrete matrix-degrading proteolytic enzymes, such as matrix metalloproteinases (MMPs). We studied levels of MMPs and tissue inhibitor of metalloproteinases-3 (TIMP-3) in relation to the characteristics of carotid plaques. We evaluated in vitro two radiolabeled probes targeting active MMPs towards non-invasive imaging of rupture-prone plaques. METHODS Human carotid plaques obtained from endarterectomy were classified into stable and vulnerable by visual and histological analysis. MMP-1, MMP-2, MMP-8, MMP-9, MMP-10, MMP-12, MMP-14, TIMP-3, and CD68 levels were investigated by quantitative polymerase chain reaction. Immunohistochemistry was used to localize MMP-2 and MMP-9 with respect to CD68-expressing macrophages. Western blotting was applied to detect their active forms. A fluorine-18-labeled MMP-2/MMP-9 inhibitor and a tritiated selective MMP-9 inhibitor were evaluated by in vitro autoradiography as potential lead structures for non-invasive imaging. RESULTS Gene expression levels of all MMPs and CD68 were elevated in plaques. MMP-1, MMP-9, MMP-12 and MMP-14 were significantly higher in vulnerable than stable plaques. TIMP-3 expression was highest in stable and low in vulnerable plaques. Immunohistochemistry revealed intensive staining of MMP-9 in vulnerable plaques. Western blotting confirmed presence of the active form in plaque lysates. In vitro autoradiography showed binding of both inhibitors to stable and vulnerable plaques. CONCLUSIONS MMPs differed in their expression patterns among plaque phenotypes, providing possible imaging targets. The two tested MMP-2/MMP-9 and MMP-9 inhibitors may be useful to detect atherosclerotic plaques, but not the vulnerable lesions selectively

Studies toward the Development of New Silicon-Containing Building Blocks for the Direct ¹⁸F‑Labeling of Peptides

Silicon-containing prosthetic groups have been conjugated to peptides to allow for a single-step labeling with ¹⁸F radioisotope. The fairly lipophilic di-<i>tert</i>-butylphenylsilane building block contributes unfavorably to the pharmacokinetic profile of bombesin conjugates. In this article, theoretical and experimental studies toward the development of more hydrophilic silicon-based building blocks are presented. Density functional theory calculations were used to predict the hydrolytic stability of di-<i>tert</i>-butylfluorosilanes <b>2</b>–<b>23</b> with the aim to improve the in vivo properties of ¹⁸F-labeled silicon-containing biomolecules. As a further step toward improving the pharmacokinetic profile, hydrophilic linkers were introduced between the lipophilic di-<i>tert</i>-butylphenylsilane building block and the bombesin congeners. Increased tumor uptake was shown with two of these peptides in xenograft-bearing mice using positron emission tomography and biodistribution studies. The introduction of a hydrophilic linker is thus a viable approach to improve the tumor uptake of ¹⁸F-labeled silicon–bombesin conjugates

Design, Synthesis, and Initial Evaluation of a High Affinity Positron Emission Tomography Probe for Imaging Matrix Metalloproteinases <b>2</b> and <b>9</b>

The activity of matrix metalloproteinases (MMPs) is elevated locally under many pathological conditions. Gelatinases MMP2 and MMP9 are of particular interest because of their implication in angiogenesis, cancer cell proliferation and metastasis, and atherosclerotic plaque rupture. The aim of this study was to identify and develop a selective gelatinase inhibitor for imaging active MMP2/MMP9 in vivo. We synthesized a series of <i>N</i>-sulfonylamino acid derivatives with low to high nanomolar inhibitory potencies. (<i>R</i>)-2-(4-(4-Fluorobenzamido)­phenylsulfonamido)-3-(1<i>H</i>-indol-3-yl)­propanoic acid (<b>7</b>) exhibited the best in vitro binding properties: MMP2 IC₅₀ = 1.8 nM, MMP9 IC₅₀ = 7.2 nM. Radiolabeling of <b>7</b> with no carrier added ¹⁸F-radioisotope was accomplished starting from iodonium salts as precursors. The radiochemical yield strongly depended on the iodonium counteranion (ClO₄^– > Br^– > TFA^– > tosylate). ¹⁸F-<b>7</b> was obtained in up to 20% radiochemical yield (decay corrected), high radiochemical purity, and >90 GBq/μmol specific radioactivity. The radiolabeled compound showed excellent stability in vitro and in mice in vivo