⁶⁸Ga-Labeled Gold Glyconanoparticles for Exploring Blood–Brain Barrier Permeability: Preparation, Biodistribution Studies, and Improved Brain Uptake via Neuropeptide Conjugation

New tools and techniques to improve brain visualization and assess drug permeability across the blood–brain barrier (BBB) are critically needed. Positron emission tomography (PET) is a highly sensitive, noninvasive technique that allows the evaluation of the BBB permeability under normal and disease-state conditions. In this work, we have developed the synthesis of novel water-soluble and biocompatible glucose-coated gold nanoparticles (GNPs) carrying BBB-permeable neuropeptides and a chelator of the positron emitter ⁶⁸Ga as a PET reporter for in vivo tracking biodistribution. The small GNPs (2 nm) are stabilized and solubilized by a glucose conjugate. A NOTA ligand is the chelating agent for the ⁶⁸Ga, and two related opioid peptides are used as targeting ligands for improving BBB crossing. The radioactive labeling of the GNPs is completed in 30 min at 70 °C followed by purification via centrifugal filtration. As a proof of principle, a biodistribution study in rats is performed for the different ⁶⁸Ga-GNPs. The accumulation of radioactivity in different organs after intravenous administration is measured by whole body PET imaging and gamma counter measurements of selected organs. The biodistribution of the ⁶⁸Ga-GNPs varies depending on the ligands, as GNPs with the same gold core size show different distribution profiles. One of the targeted ⁶⁸Ga-GNPs improves BBB crossing near 3-fold (0.020 ± 0.0050% ID/g) compared to nontargeted GNPs (0.0073 ± 0.0024% ID/g) as measured by dissection and tissue counting

Microdosed Lipid-Coated ⁶⁷Ga-Magnetite Enhances Antigen-Specific Immunity by Image Tracked Delivery of Antigen and CpG to Lymph Nodes

Development of vaccines to prevent and treat emerging new pathogens and re-emerging infections and cancer remains a major challenge. An attractive approach is to build the vaccine upon a biocompatible NP that simultaneously acts as accurate delivery vehicle and radiotracer for PET/SPECT imaging for ultrasensitive and quantitative <i>in vivo</i> imaging of NP delivery to target tissues/organs. Success in developing these nanovaccines will depend in part on having a “correct” NP size and accommodating and suitably displaying antigen and/or adjuvants (<i>e.g</i>., TLR agonists). Here we develop and evaluate a NP vaccine based on iron oxide-selective radio-gallium labeling suitable for SPECT­(⁶⁷Ga)/PET­(⁶⁸Ga) imaging and efficient delivery of antigen (OVA) and TLR 9 agonists (CpGs) using lipid-coated magnetite micelles. OVA, CpGs and rhodamine are easily accommodated in the hybrid micelles, and the average size of the construct can be controlled to be <i>ca</i>. 40 nm in diameter to target direct lymphatic delivery of the vaccine cargo to antigen presenting cells (APCs) in the lymph nodes (LNs). While the OVA/CpG-loaded construct showed effective delivery to endosomal TLR 9 in APCs, SPECT imaging demonstrated migration from the injection site to regional and nonregional LNs. In correlation with the imaging results, a range of <i>in vitro</i> and <i>in vivo</i> studies demonstrate that by using this microdosed nanosystem the cellular and humoral immune responses are greatly enhanced and provide protection against tumor challenge. These results suggest that these nanosystems have considerable potential for image-guided development of targeted vaccines that are more effective and limit toxicity

Novel ¹⁸F Labeling Strategy for Polyester-Based NPs for in Vivo PET-CT Imaging

Drug-loaded nanocarriers and nanoparticulate systems used for drug release require a careful in vivo evaluation in terms of physicochemical and pharmacokinetic properties. Nuclear imaging techniques such as positron emission tomography (PET) are ideal and noninvasive tools to investigate the biodistribution and biological fate of the nanostructures, but the incorporation of a positron emitter is required. Here we describe a novel approach for the ¹⁸F-radiolabeling of polyester-based nanoparticles. Our approach relies on the preparation of the radiolabeled active agent 4-[¹⁸F]­fluorobenzyl-2-bromoacetamide ([¹⁸F]­FBBA), which is subsequently coupled to block copolymers under mild conditions. The labeled block copolymers are ultimately incorporated as constituent elements of the NPs by using a modified nano coprecipitation method. This strategy has been applied in the current work to the preparation of peptide-functionalized NPs with potential applications in drug delivery. According to the measurements of particle size and zeta potential, the radiolabeling process did not result in a statistically significant alteration of the physicochemical properties of the NPs. Moreover, radiochemical stability studies showed no detachment of the radioactivity from NPs even at 12 h after preparation. The radiolabeled NPs enabled the in vivo quantification of the biodistribution data in rats using a combination of imaging techniques, namely, PET and computerized tomography (CT). Low accumulation of the nanoparticles in the liver and their elimination mainly via urine was found. The different biodistribution pattern obtained for the “free” radiolabeled polymer suggests chemical and radiochemical integrity of the NPs under investigation. The strategy reported here may be applied to any polymeric NPs containing polymers bearing a nucleophile, and hence our novel strategy may find application for the in vivo and noninvasive investigation of a wide range of NPs

Functional Single-Chain Polymer Nanoparticles: Targeting and Imaging Pancreatic Tumors <i>in Vivo</i>

The development of tools for the early diagnosis of pancreatic adenocarcinoma is an urgent need in order to increase treatment success rate and reduce patient mortality. Here, we present a modular nanosystem platform integrating soft nanoparticles with a targeting peptide and an active imaging agent for diagnostics. Biocompatible single-chain polymer nanoparticles (SCPNs) based on poly­(methacrylic acid) were prepared and functionalized with the somatostatin analogue PTR86 as the targeting moiety, since somatostatin receptors are overexpressed in pancreatic cancer. The gamma emitter ⁶⁷Ga was incorporated by chelation and allowed <i>in vivo</i> investigation of the pharmacokinetic properties of the nanoparticles using single photon emission computerized tomography (SPECT). The resulting engineered nanosystem was tested in a xenograph mouse model of human pancreatic adenocarcinoma. Imaging results demonstrate that accumulation of targeted SCPNs in the tumor is higher than that observed for nontargeted nanoparticles due to improved retention in this tissue