Direct Radiolabeling of Trastuzumab-Targeting Triblock Copolymer Vesicles with 89Zr for Positron Emission Tomography Imaging

Radiolabeled drug nanocarriers that can be easily imaged via positron emission tomography (PET) are highly significant as their in vivo outcome can be quantitatively PET-traced with high sensitivity. However, typical radiolabeling of most PET-guided theranostic vehicles utilizes modification with chelator ligands, which presents various challenges. In addition, unlike passive tumor targeting, specific targeting of drug delivery vehicles via binding affinity to overexpressed cancer cell receptors is crucial to improve the theranostic delivery to tumors. Herein, we developed 89Zr-labeled triblock copolymer polymersomes of 60 nm size through chelator-free radiolabeling. The polymersomes are assembled from poly(N-vinylpyrrolidone)5-b-poly(dimethylsiloxane)30-b-poly(N-vinylpyrrolidone)5 (PVPON5-PDMS30-PVPON5) triblock copolymers followed by adsorption of a degradable tannin, tannic acid (TA), on the polymersome surface through hydrogen bonding. TA serves as an anchoring layer for both 89Zr radionuclide and targeting recombinant humanized monoclonal antibody, trastuzumab (Tmab). Unlike bare PVPON5-PDMS30-PVPON5 polymersomes, TA- and Tmab-modified polymersomes demonstrated a high radiochemical yield of more than 95%. Excellent retention of 89Zr by the vesicle membrane for up to 7 days was confirmed by PET in vivo imaging. Animal biodistribution using healthy BALB/c mice confirmed the clearance of 89Zr-labeled polymersomes through the spleen and liver without their accumulation in bone, unlike the free nonbound 89Zr radiotracer. The 89Zr-radiolabeled polymersomes were found to specifically target BT474 HER2-positive breast cancer cells via the Tmab-TA complex on the vesicle surface. The noncovalent Tmab anchoring to the polymersome membrane can be highly advantageous for nanoparticle modification compared to currently developed covalent methods, as it allows easy and quick integration of a broad range of targeting proteins. Given the ability of these polymersomes to encapsulate and release anticancer therapeutics, they can be further expanded as precision-targeted therapeutic carriers for advancing human health through highly effective drug delivery strategies.

Multilayer Microcapsules with Shell-Chelated 89Zr for PET Imaging and Controlled Delivery

Radionuclide-functionalized drug delivery vehicles capable of being imaged via positron emission tomography (PET) are of increasing interest in the biomedical field as they can reveal the in vivo behavior of encapsulated therapeutics with high sensitivity. However, the majority of current PET-guided theranostic agents suffer from poor retention of radiometal over time, low drug loading capacities, and time-limited PET imaging capability. To overcome these challenges, we have developed hollow microcapsules with a thin (<100 nm) multilayer shell as advanced theranostic delivery systems for multiday PET tracking in vivo. The 3 μm capsules were fabricated via the aqueous multilayer assembly of a natural antioxidant, tannic acid (TA), and a poly(N-vinylpyrrolidone) (PVPON) copolymer containing monomer units functionalized with deferoxamine (DFO) to chelate the ⁸⁹Zr radionuclide, which has a half-life of 3.3 days. We have found using radiochromatography that (TA/PVPON-DFO)₆ capsules retained on average 17% more ⁸⁹Zr than their (TA/PVPON)₆ counterparts, which suggests that the covalent attachment of the DFO to PVPON provides stable ⁸⁹Zr chelation. In vivo PET imaging studies performed in mice demonstrated that excellent stability and imaging contrast were still present 7 days postinjection. Animal biodistribution analyses showed that capsules primarily accumulated in the spleen, liver, and lungs with negligible accumulation in the femur, with the latter confirming the stable binding of the radiotracer to the capsule walls. The application of therapeutic ultrasound (US) (60 s of 20 kHz US at 120 W cm^-2) to Zr-functionalized capsules could release the hydrophilic anticancer drug doxorubicin from the capsules in the therapeutic amounts. Polymeric capsules with the capability of extended in vivo PET-based tracking and US-induced drug release provide an advanced platform for development of precision-targeted therapeutic carriers and could aid in the development of more effective drug delivery systems.

Radiolabeled liposomes and lipoproteins as lipidic nanoparticles for imaging and therapy

Radiolabeled lipidic nanoparticles, particularly liposomes and lipoproteins, are of great interest as agents for imaging and therapy, due not only to their peculiar physicochemical and biological properties, but also to their great versatility and the ability to manipulate them to obtain the desired properties. This review provides an overview of radionuclide labeling strategies for preparing diagnostic and therapeutic nanoparticles based on liposomes and lipoproteins that have been developed to date, as well as the main quality control methods and in vivo applications.

Drug-Abuse Nanotechnology: Opportunities and Challenges

Opioid drug abuse and dependence/addiction are complex disorders regulated by a wide range of interacting networks of genes and pathways that control a variety of phenotypes. Although the field has been extensively progressed since the birth of the National Institute on Drug Abuse in 1974, the fundamental knowledge and involved mechanisms that lead to drug dependence/addiction are poorly understood, and thus, there has been limited success in the prevention of drug addiction and development of therapeutics for definitive treatment and cure of addiction disease. The lack of success in both identification of addiction in at-risk populations and the development of efficient drugs has resulted in a serious social and economic burden from opioid drug abuse with global increasing rate of mortality from drug overdoses. This perspective aims to draw the attention of scientists to the potential role of nanotechnologies, which might pave the way for the development of more practical platforms for either drug development or identification and screening of patients who may be vulnerable to addiction after using opioid drugs.

Multimodal nanoparticle imaging agents: design and applications

Molecular imaging, where the location of molecules or nanoscale constructs can be tracked in the body to report on disease or biochemical processes, is rapidly expanding to include combined modality or multimodal imaging. No single imaging technique can offer the optimum combination of properties (e.g. resolution, sensitivity, cost, availability). The rapid technological advances in hardware to scan patients, and software to process and fuse images, are pushing the boundaries of novel medical imaging approaches, and hand-in-hand with this is the requirement for advanced and specific multimodal imaging agents. These agents can be detected using a selection from radioisotope, magnetic resonance and optical imaging, among others. Nanoparticles offer great scope in this area as they lend themselves, via facile modification procedures, to act as multifunctional constructs. They have relevance as therapeutics and drug delivery agents that can be tracked by molecular imaging techniques with the particular development of applications in optically guided surgery and as radiosensitizers. There has been a huge amount of research work to produce nanoconstructs for imaging, and the parameters for successful clinical translation and validation of therapeutic applications are now becoming much better understood. It is an exciting time of progress for these agents as their potential is closer to being realized with translation into the clinic. The coming 5-10 years will be critical, as we will see if the predicted improvement in clinical outcomes becomes a reality. Some of the latest advances in combination modality agents are selected and the progression pathway to clinical trials analysed.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.