Opening up the optical imaging window using nano-luciferin

Engineered Ferritin Nanoparticles for the Bioluminescence Tracking of Nanodrug Delivery in Cancer

The identification of a highly sensitive method to check the delivery of administered nanodrugs into the tumor cells is a crucial step of preclinical studies aimed to develop new nanoformulated cures, since it allows the real therapeutic potential of these devices to be forecast. In the present work, the ability of an H-ferritin (HFn) nanocage, already investigated as a powerful tool for cancer therapy thanks to its ability to actively interact with the transferrin receptor 1, to act as an efficient probe for the monitoring of nanodrug delivery to tumors is demonstrated. The final formulation is a bioluminescent nanoparticle, where the luciferin probe is conjugated on nanoparticle surface by means of a disulfide containing linker (Luc-linker@HFn) which is subjected to glutathione-induced cyclization in tumor cell cytoplasm. The prolonged imaging of luciferase+ tumor models, demonstrated by an in vitro and an in vivo approach, associated with the prolonged release of luciferin into cancer cells by disulfide bridge reduction, clearly indicates the high efficiency of Luc-linker@HFn for drug delivery to the tumor tissues.

Noncovalently Caged Firefly Luciferins Enable Amplifiable Bioluminescence Sensing of Hyaluronidase-1 Activity in Vivo

Hyaluronidase 1 (Hyal-1) is an important enzyme involved in intracellular hyaluronic acid (HA) catabolism for performing various physiological functions, and its aberrant level is closely associated with many malignant diseases. Bioluminescence imaging is advantageous for monitoring Hyal-1 activity in vivo, but it remains challenging to design an available probe for differentiating Hyal-1 from other isoforms by a traditional strategy that covalently masks the firefly luciferase substrate. Herein, we, for the first time, present a noncovalently caging approach to construct a Hyal-1-specific bioluminogenic nanosensor by entrapping d-luciferin (d-Luc) inside the cholesterylamine-modified HA (CHA) nanoassembly to inhibit the bioluminescence production. When encountered with intracellular Hyal-1, CHA could be fully dissembled to liberate multiple copies of the loaded d-Luc, thereby emitting light by the luciferase-catalyzed bioluminescence reaction. Because of its cascade signal amplification feature, d-Luc@CHA displayed a remarkable "turn-on" response (248-fold) to 5 μg/mL Hyal-1 with a detection limit of 0.07 ng/mL. Importantly, bioluminescence imaging results validated that d-Luc@CHA could be competent for dynamically visualizing endogenous Hyal-1 changes in living cells and animals and possessed the capability of discriminating between normal and cancer cells, thus offering a promising toolbox to evaluate Hyal-1 roles in biological processes as well as to diagnose Hyal-1-related diseases.

Near infrared dye-labelled polymeric micro- and nanomaterials: in vivo imaging and evaluation of their local persistence

The use of micro- and nanomaterials as carriers of therapeutic molecules can enhance the efficiency of treatments while avoiding side effects thanks to the development of controlled drug delivery systems. The binding of a dye to a drug or to a drug carrier has opened up a wide range of possibilities for an effective in vivo optical tracing of drug biodistribution by using non-invasive real-time technologies prior to their potential use as therapeutic vectors. Here, we describe the fluorescent tagging of polymeric micro- and nanomaterials based on poly(lactic-co-glycolic) acid and on the thermoresponsive poly(N-isopropylacrylamide) with the fluorescent probe IR-820 which was chemically modified for its covalent coupling to the materials. The chemical modification of the dye and the polymers yielded micro- and nanoparticulated labelled materials to be potentially used as drug depots of different therapeutic molecules. In vitro biological studies revealed their reduced cytotoxicity. A spatiotemporal in vivo micro- and nanoparticle tracking allowed the evaluation of the biodistribution of materials showing their local persistence and high biocompatibility after pathological studies. These results underline the suitability of these materials for the local, sustained, not harmful and/or on-demand drug delivery and the remarkable importance of evaluating the biodistribution of materials and tissue persistence for their use as local drug depots.

Intracellular synthesis of d-aminoluciferin for bioluminescence generation

Chemically stable precursors were employed to intracellularly synthesize d-aminoluciferin for bioluminescence generation.

Intracellular Self-Assembly of Cyclic d-Luciferin Nanoparticles for Persistent Bioluminescence Imaging of Fatty Acid Amide Hydrolase

Fatty acid amide hydrolase (FAAH) overexpression induces several disorder symptoms in nerve systems, and therefore long-term tracing of FAAH activity in vivo is of high importance but remains challenging. Current bioluminescence (BL) methods are limited in detecting FAAH activity within 5 h. Herein, by rational design of a latent BL probe (d-Cys-Lys-CBT)2 (1), we developed a "smart" method of intracellular reduction-controlled self-assembly and FAAH-directed disassembly of its cyclic d-luciferin-based nanoparticles (i.e., 1-NPs) for persistent BL imaging of FAAH activity in vitro, in cells, and in vivo. Using aminoluciferin methyl amide (AMA), Lys-amino-d-luciferin (Lys-Luc), and amino-d-luciferin (NH2-Luc) as control BL probes, we validated that the persistent BL of 1 from luciferase-expressing cells or tumors was controlled by the activity of intracellular FAAH. With the property of long-term tracing of FAAH activity in vivo of 1, we envision that our BL precursor 1 could probably be applied for in vivo screening of FAAH inhibitors and the diagnosis of their related diseases (or disorders) in the future.

Molecular Imaging of Pancreatic Cancer with Antibodies

Development of novel imaging probes for cancer diagnostics remains critical for early detection of disease, yet most imaging agents are hindered by suboptimal tumor accumulation. To overcome these limitations, researchers have adapted antibodies for imaging purposes. As cancerous malignancies express atypical patterns of cell surface proteins in comparison to noncancerous tissues, novel antibody-based imaging agents can be constructed to target individual cancer cells or surrounding vasculature. Using molecular imaging techniques, these agents may be utilized for detection of malignancies and monitoring of therapeutic response. Currently, there are several imaging modalities commonly employed for molecular imaging. These imaging modalities include positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance (MR) imaging, optical imaging (fluorescence and bioluminescence), and photoacoustic (PA) imaging. While antibody-based imaging agents may be employed for a broad range of diseases, this review focuses on the molecular imaging of pancreatic cancer, as there are limited resources for imaging and treatment of pancreatic malignancies. Additionally, pancreatic cancer remains the most lethal cancer with an overall 5-year survival rate of approximately 7%, despite significant advances in the imaging and treatment of many other cancers. In this review, we discuss recent advances in molecular imaging of pancreatic cancer using antibody-based imaging agents. This task is accomplished by summarizing the current progress in each type of molecular imaging modality described above. Also, several considerations for designing and synthesizing novel antibody-based imaging agents are discussed. Lastly, the future directions of antibody-based imaging agents are discussed, emphasizing the potential applications for personalized medicine.

Extracellular vesicle in vivo biodistribution is determined by cell source, route of administration and targeting

Extracellular vesicles (EVs) have emerged as important mediators of intercellular communication in a diverse range of biological processes. For future therapeutic applications and for EV biology research in general, understanding the in vivo fate of EVs is of utmost importance. Here we studied biodistribution of EVs in mice after systemic delivery. EVs were isolated from 3 different mouse cell sources, including dendritic cells (DCs) derived from bone marrow, and labelled with a near-infrared lipophilic dye. Xenotransplantation of EVs was further carried out for cross-species comparison. The reliability of the labelling technique was confirmed by sucrose gradient fractionation, organ perfusion and further supported by immunohistochemical staining using CD63-EGFP probed vesicles. While vesicles accumulated mainly in liver, spleen, gastrointestinal tract and lungs, differences related to EV cell origin were detected. EVs accumulated in the tumour tissue of tumour-bearing mice and, after introduction of the rabies virus glycoprotein-targeting moiety, they were found more readily in acetylcholine-receptor-rich organs. In addition, the route of administration and the dose of injected EVs influenced the biodistribution pattern. This is the first extensive biodistribution investigation of EVs comparing the impact of several different variables, the results of which have implications for the design and feasibility of therapeutic studies using EVs.

Passive and specific targeting of lymph nodes: the influence of the administration route

Patients diagnosed with an advanced-stage cancer present a dismal prognosis due to the presence of metastases. From the primary tumor, the cancer cells are disseminated via lymphatic circulation; metastases develop initially in lymph nodes. Therefore, the targeting of lymph nodes needs to be improved in the design of future chemotherapy, and one way to ensure this targeting is by using the subcutaneous (SC) route. Using lipid nanocapsules (LNCs) (40 nm and fluorescently-labeled with DiD) as nanocarriers, a correlation between the SC injection site (behind the neck, the right and left flanks, and above the tail) for LNC administration and specific lymph node accumulation (left and right cervical, axillary and inguinal lymph nodes) was achieved for Sprague-Dawley rats. The pharmacokinetic and biodistribution profiles confirmed the absence of LNCs in systemic circulation after SC administration due to the optimal size of the LNCs. With appropriate SC administration, LNCs can accumulate in specific lymph nodes, whereas IV administration led to a weak accumulation of LNCs in all lymph nodes. Specific accumulation followed the lymph flow: bottom-up from the lower to upper limbs and top down from the head, with two lymph circulation partitions: right upper limb and the rest. Administration above the tail presented high inguinal and axillary lymph node accumulation whereas weak accumulation was observed after administration behind the neck. LNCs administered in the left flank only accumulated in the left inguinal and axillary lymph nodes, whereas left and right inguinal and axillary lymph nodes presented accumulation after administration in the right flank. Cervical lymph nodes, in the opposite direction of lymph flow, were never targeted after SC administration, whatever the injection site.