Andrea Robinson Group

Fluorine-18 is the most utilized radioisotope in positron emission tomography (PET), but the wide application of fluorine-18 radiopharmaceuticals is hindered by its challenging labelling conditions. As such, many potentially important radiotracers remain underutilized. Herein, we describe the use of [¹⁸F]ethenesulfonyl fluoride (ESF) as a novel radiofluoride relay reagent that allows radiofluorination reactions to be performed in minimally equipped satellite nuclear medicine centres. [¹⁸F]ESF has a simple and reliable production route and can be stored on inert cartridges. The cartridges can then be shipped remotely and the trapped [¹⁸F]ESF can be liberated by simple solvent elution. We have tested 18 radiolabelling precursors, inclusive of model and clinically used structures, and most precursors have demonstrated comparable radiofluorination efficiencies to those obtained using a conventionally dried [¹⁸F]fluoride source.

Purpose

Paclitaxel (PTX)-coated drug eluting balloon catheters (DEBc) used in the management of neointimal hyperplasia (NIH) have been associated with safety concerns. Alternative coating agents and targeted delivery systems may improve safety and DEBc efficacy. Utilizing a multi-platform approach we designed, developed and evaluated Lumi-Solve, a novel DEBc, coated with ultraviolet (UV) 365 nm-activated caged metacept-3 (c-MCT-3), an epigenetic agent from the histone deacetylase inhibitor (HDACi) class.

Methods

In vitro catheter and contrast media transmission of UV365nm was evaluated spectroscopically. UV365nm conversion of c-MCT-3 to MCT-3 was evaluated chromatographically. Cellular toxicity and HDACi activity of c-MCT-3 ∓UV365nm was evaluated in vitro. In vivo UV365nm conversion of c-MCT-3 to MCT-3 was evaluated in an ovine carotid artery model.

Results

Catheter material and dilute contrast media did not attenuate UV365nm transmission or c-MCT-3 activation. c-MCT-3 demonstrated less cellular toxicity than MCT-3 and PTX. UV365nm-activated c-MCT-3 demonstrated HDACi activity. In vivo activation of c-MCT-3 produced MCT-3.

Conclusions

Lumi-Solve, a novel DEBc device developed utilizing a combination of chemical, fibre-optic and catheter based technology platforms, demonstrated potential for targeted delivery of bioactive HDACi to the blood vessel wall supporting direct application to the management of NIH and warranting additional in vivo studies.

Photothermal therapy (PTT), a simple and minimally invasive procedure, is an attractive option for cancer therapy. To date, inorganic agents have been widely employed as photothermal agents; however, organic molecules may provide a solution to rapid metabolic/in vivo clearance. Herein, we prepared lipid (S 75)-stabilized meso-tritolyl-BF₂-oxasmaragdyrin nanoparticles (TBSNPs) using thin-film hydration and homogenization. Assessment of the physicochemical properties of the TBSNPs reveals the formation of particles of size <12 nm stabilized within the lipid matrix. The TBSNPs exhibit near infrared fluorescence (NIRF) being accompanied by an increase in non-radiative decay, leading to excellent photothermal properties. In vitro studies demonstrate excellent biocompatibility, hemocompatibility, cellular internalization, and photothermal efficacy (p = 0.0004). Extensive in vivo assessment of TBSNPs also highlights the non-toxic nature of the material and passive tumor homing. The strong NIRF exhibited by the material is exploited for whole-body imaging in the rodent model. The novel material also shows excellent photothermal efficacy (p = 0.0002) in a 4T1 xenograft mice model. The organic nature of the material coupled with its small size and strong NIRF provides an advantage for bio-elimination and potential clinical image-guided therapy over the inorganic counterparts.

A value addition to the existing NIR fluorescence imaging agents has been synthesized in the form of glucosamine conjugated BF₂-oxasmaragdyrin by treating meso–p-carboxyphenyl BF₂-oxasmaragdyrin with 6-amine-6-deoxy-1-O-Boc-2-N-Boc-β-D-glucosamine in the presence of HBTU. The glucosamine conjugated BF₂-oxasmaragdyrin was thoroughly characterized by HRMS, 1D, and 2D NMR spectroscopy. The photophysical studies revealed that the conjugates are highly stable, absorb in visible- far-red region (400-700 nm) and emits in far-red region (715 nm) with moderate quantum yields. The electrochemical studies showed that the molecules are stable under redox conditions with one reversible reduction and three reversible oxidations. The glucosamine conjugated BF₂-oxasmaragdyrin was found to be highly biocompatible with good cellular uptake in L929 and MDA-MB-231 cells.

Cell-penetrating peptides (CPPs) are excellent cell internalizing agents for hydrophobic drug/dye moieties. We exploited this property of CPPs for the cell internalization of BF₂-oxasmaragdyrin by constructing covalent conjugates of BF₂-oxasmaragdyrin with CPPs (CRGDK and polyarginine (R₉)) using a solid-phase peptide synthesis (SPPS) methodology. The CPP-conjugated BF₂-oxasmaragdyrins were purified by reversed-phase HPLC and characterized by mass spectrometry. The CPP-conjugated BF₂-oxasmaragdyrins were found to be photostable, absorb in the visible-NIR region (400–700 nm), emit in the NIR−I region (∼715–720 nm) with moderate quantum yields, and be biocompatible, with excellent cellular imaging potential in breast cancer cells (MDA-MB-231). The R₉conjugate, being the first water-soluble BF₂-oxasmaragdyrin, also possesses excellent photothermal transduction efficacy with 750 nm laser irradiation and is a potential theranostic agent.