Nanoemulsion

Nanoemulsion is the major vehicle for delivering different types of drugs, nucleic acids, and imaging agents. Due to their attractive properties, it has been extensively used for diagnostics of cancer therapy and imaging. However, nanoemulsion is designed through multiple functions by modifications in surface and encapsulation of active compounds against cancer. In nanoemulsion, the surface alteration can be changed by targeting the surface charge, a targeting ligand. The core of the emulsion can be loaded with drugs, imaging agents, and contrast agents. In this chapter, the application of nanoemulsion against specifically liver and gastric cancer is explored briefly. The major focuses on the severity of cancer, multifunctional nature of respective drug-loaded nanoemulsions, how to defeat the physiological hurdles, targeted and non-targeted delivery of nanoemulsion, clinical and preclinical studies are discussed with trending examples from the review of the literature and future perspectives.

Synthesis and evaluation of radiogallium-labeled long-chain fatty acid derivatives as myocardial metabolic imaging agents

Since long-chain fatty acids work as the primary energy source for the myocardium, radiolabeled long-chain fatty acids play an important role as imaging agents to diagnose metabolic heart dysfunction and heart diseases. With the aim of developing radiogallium-labeled fatty acids, herein four fatty acid-based tracers, [67Ga]Ga-HBED-CC-PDA, [67Ga]Ga-HBED-CC-MHDA, [67Ga]Ga-DOTA-PDA, and [67Ga]Ga-DOTA-MHDA, which are [67Ga]Ga-HBED-CC and [67Ga]Ga-DOTA conjugated with pentadecanoic acid (PDA) and 3-methylhexadecanoic acid (MHDA), were synthesized, and their potential for myocardial metabolic imaging was evaluated. Those tracers were found to be chemically stable in 0.1 M phosphate buffered saline. Initial [67Ga]Ga-HBED-CC-PDA, [67Ga]Ga-HBED-CC-MHDA, [67Ga]Ga-DOTA-PDA, and [67Ga]Ga-DOTA-MHDA uptakes in the heart at 0.5 min postinjection were 5.01 ± 0.30%ID/g, 5.74 ± 1.02%ID/g, 5.67 ± 0.22%ID/g, and 5.29 ± 0.10%ID/g, respectively. These values were significantly lower than that of [123I]BMIPP (21.36 ± 2.73%ID/g). For their clinical application as myocardial metabolic imaging agents, further structural modifications are required to increase their uptake in the heart.

SapC–DOPS as a Novel Therapeutic and Diagnostic Agent for Glioblastoma Therapy and Detection: Alternative to Old Drugs and Agents

Glioblastoma multiforme (GBM), the most common type of brain cancer, is extremely aggressive and has a dreadful prognosis. GBM comprises 60% of adult brain tumors and the 5 year survival rate of GBM patients is only 4.3%. Standard-of-care treatment includes maximal surgical removal of the tumor in combination with radiation and temozolomide (TMZ) chemotherapy. TMZ is the “gold-standard” chemotherapy for patients suffering from GBM. However, the median survival is only about 12 to 18 months with this protocol. Consequently, there is a critical need to develop new therapeutic options for treatment of GBM. Nanomaterials have unique properties as multifunctional platforms for brain tumor therapy and diagnosis. As one of the nanomaterials, lipid-based nanocarriers are capable of delivering chemotherapeutics and imaging agents to tumor sites by enhancing the permeability of the compound through the blood–brain barrier, which makes them ideal for GBM therapy and imaging. Nanocarriers also can be used for delivery of radiosensitizers to the tumor to enhance the efficacy of the radiation therapy. Previously, high-atomic-number element-containing particles such as gold nanoparticles and liposomes have been used as radiosensitizers. SapC–DOPS, a protein-based liposomal drug comprising the lipid, dioleoylphosphatidylserine (DOPS), and the protein, saposin C (SapC), has been shown to be effective for treatment of a variety of cancers in small animals, including GBM. SapC–DOPS also has the unique ability to be used as a carrier for delivery of radiotheranostic agents for nuclear imaging and radiotherapeutic purposes. These unique properties make tumor-targeting proteo-liposome nanocarriers novel therapeutic and diagnostic alternatives to traditional chemotherapeutics and imaging agents. This article reviews various treatment modalities including nanolipid-based delivery and therapeutic systems used in preclinical and clinical trial settings for GBM treatment and detection.

Mesoporous Silica Nanoparticle-Based Imaging Agents for Hepatocellular Carcinoma Detection

Hepatocellular carcinoma (HCC) is characterized by poor prognosis and high mortality. The treatment of HCC is closely related to the stage, and the early-stage of HCC patients usually accompanies a more long-term survival rate after clinical treatment. Hence, there are critical needs to develop effective imaging agents with superior diagnostic precision for HCC detection at an early stage. Recently, mesoporous silica nanoparticles (MSNs) based imaging agents have gained extensive attentions in HCC detection, which can serve as a multifunctional nanoplatform with controllable size and facile surface functionalization. This perspective summarizes recent advances in MSNs based imaging agents for HCC detection by the incorporation of several clinical imaging modalities. Multi-modal imaging system has been developed for higher spatial resolution and sensitivity. Even though some limitations and challenges need to be overcome, we envision the development of novel MSNs based imaging agents will offer great potential applications in clinical HCC detection.

Development of bacterial nitroreductase enzymes for noninvasive imaging in cancer gene therapy

<p>There is strong interest in developing novel targeted cancer therapies. It has been known for over a century that certain viruses and bacteria can preferentially infect and lyse cancerous cells. Clinical utility has lagged behind the initial promise of the idea; however three therapeutic agents from the oncolytic virus field are currently in Phase IIB/Phase III clinical trials. The development path of such therapies would be substantially smoothed by an ability to nonin vasively monitor the ir location in the patient’s body post-administration. This would allay fears that viral/bacterial distribution may not be confined to the tumour and provide real time information on vector localisation and replication. This could be achieved by positron emission tomography (PET) scanning if the vector expressed a reporter protein which could activate a PET suitable imaging agent. Furthermore the potency of such therapies could be increased by if this reporter protein could also act therapeutically by converting a systemically delivered benign prodrug into a potent chemotherapeutic – thus targeting the toxicity of the prodrug specifically to cancerous cells. A promising enzyme/prodrug combination is the use of bacterial nitroreductase (NTR) enzymes to activate DNA damaging prodrugs, such as the dinitrobenzamides CB1954 and PR-104A. This thesis presents work aimed at developing the ability to noninvasively image bacterial NTR expression so that these enzymes can act as both therapeutic and reporter proteins. The primary focus of this study was to achieve this by repurposing pre-existing 2-nitroimidazole (NI) PET imaging agents, originally developed for imaging tumour hypoxia. Microplate based screening strategies were developed to enable detection of 2-NI bioreductive activation by different bacterial NTRs over-expressed heterologously in Escherichia coli, and these technologies were used to screen a 58-membered library of nitroreductase candidates. Although the most widely studied NTR for enzyme/prodrug therapy - NfsB from E. coli - was found to lack activity with 2-NI substrates, numerous NTRs from the NfsA family were able to metabolise these molecules to the cell entrapped form required for PET imaging. Following this discovery, a directed evolution study was conducted to improve the native activity of the enzyme NfsA from E. coli. In this study targeted mutagenesis of active site residues was carried out, resulting in identification of several NfsA multi-site mutants that were substantially improved in their ability to activate a range of 2-NI imaging agents. In addition to repurposing existing PET probes, this work sought to identify and engineer NTRs for efficient activation of a next - generation PET probe that is designed to be substantially less responsive to hypoxia and hence give a cleaner signal for NTR imaging (i.e. low to no background resulting from tumour hypoxia). SN 33623, a novel 5-NI analogue of the existing 2-NI PET probe EF5, was designed and synthesised by our University of Auckland collaborators. It was found that this novel probe was not only activated by NfsA enzymes, but also by a subset of NfsB enzymes. Although this subset did not include E. coli NfsB, sequence alignment and site-directed mutagenesis were used to identify two key mutations that can be introduced into E. coli NfsB (as well as engineered variants thereof) to confer high levels of SN 33623 activity. Finally work was carried out, as part of a wider collaborative project, to generate NfsA mutants that retained the ability to metabolise 2-NI imaging agents while also showing increased activation of the nitroaromatic prodrug PR-104A. Ongoing evaluation of these enzymes will include assessment of their therapeutic effect in preclinical models and their ability to be noninvasively imaged (by microPET) when expressed from the tumour targeting bacterial strain Clostridium sporogenes.</p>

Development of bacterial nitroreductase enzymes for noninvasive imaging in cancer gene therapy

<p>There is strong interest in developing novel targeted cancer therapies. It has been known for over a century that certain viruses and bacteria can preferentially infect and lyse cancerous cells. Clinical utility has lagged behind the initial promise of the idea; however three therapeutic agents from the oncolytic virus field are currently in Phase IIB/Phase III clinical trials. The development path of such therapies would be substantially smoothed by an ability to nonin vasively monitor the ir location in the patient’s body post-administration. This would allay fears that viral/bacterial distribution may not be confined to the tumour and provide real time information on vector localisation and replication. This could be achieved by positron emission tomography (PET) scanning if the vector expressed a reporter protein which could activate a PET suitable imaging agent. Furthermore the potency of such therapies could be increased by if this reporter protein could also act therapeutically by converting a systemically delivered benign prodrug into a potent chemotherapeutic – thus targeting the toxicity of the prodrug specifically to cancerous cells. A promising enzyme/prodrug combination is the use of bacterial nitroreductase (NTR) enzymes to activate DNA damaging prodrugs, such as the dinitrobenzamides CB1954 and PR-104A. This thesis presents work aimed at developing the ability to noninvasively image bacterial NTR expression so that these enzymes can act as both therapeutic and reporter proteins. The primary focus of this study was to achieve this by repurposing pre-existing 2-nitroimidazole (NI) PET imaging agents, originally developed for imaging tumour hypoxia. Microplate based screening strategies were developed to enable detection of 2-NI bioreductive activation by different bacterial NTRs over-expressed heterologously in Escherichia coli, and these technologies were used to screen a 58-membered library of nitroreductase candidates. Although the most widely studied NTR for enzyme/prodrug therapy - NfsB from E. coli - was found to lack activity with 2-NI substrates, numerous NTRs from the NfsA family were able to metabolise these molecules to the cell entrapped form required for PET imaging. Following this discovery, a directed evolution study was conducted to improve the native activity of the enzyme NfsA from E. coli. In this study targeted mutagenesis of active site residues was carried out, resulting in identification of several NfsA multi-site mutants that were substantially improved in their ability to activate a range of 2-NI imaging agents. In addition to repurposing existing PET probes, this work sought to identify and engineer NTRs for efficient activation of a next - generation PET probe that is designed to be substantially less responsive to hypoxia and hence give a cleaner signal for NTR imaging (i.e. low to no background resulting from tumour hypoxia). SN 33623, a novel 5-NI analogue of the existing 2-NI PET probe EF5, was designed and synthesised by our University of Auckland collaborators. It was found that this novel probe was not only activated by NfsA enzymes, but also by a subset of NfsB enzymes. Although this subset did not include E. coli NfsB, sequence alignment and site-directed mutagenesis were used to identify two key mutations that can be introduced into E. coli NfsB (as well as engineered variants thereof) to confer high levels of SN 33623 activity. Finally work was carried out, as part of a wider collaborative project, to generate NfsA mutants that retained the ability to metabolise 2-NI imaging agents while also showing increased activation of the nitroaromatic prodrug PR-104A. Ongoing evaluation of these enzymes will include assessment of their therapeutic effect in preclinical models and their ability to be noninvasively imaged (by microPET) when expressed from the tumour targeting bacterial strain Clostridium sporogenes.</p>

Radiolabeled Silicon-Rhodamines as Bimodal PET/SPECT-NIR Imaging Agents

Radiolabeled fluorescent dyes are decisive for bimodal imaging as well as highly in demand for nuclear- and optical imaging. Silicon-rhodamines (SiRs) show unique near-infrared (NIR) optical properties, large quantum yields and extinction coefficients as well as high photostability. Here, we describe the synthesis, characterization and radiolabeling of novel NIR absorbing and emitting fluorophores from the silicon-rhodamine family for use in optical imaging (OI) combined with positron emission tomography (PET) or single photon emission computed tomography (SPECT), respectively. The presented photostable SiRs were characterized using NMR-, UV-Vis-NIR-spectroscopy and mass spectrometry. Moreover, the radiolabeling conditions using fluorine-18 or iodine-123 were extensively explored. After optimization, the radiofluorinated NIR imaging agents were obtained with radiochemical conversions (RCC) up to 70% and isolated radiochemical yields (RCY) up to 54% at molar activities of g.t. 70 GBq/µmol. Radioiodination delivered RCCs over 92% and allowed to isolate the 123I-labeled product in RCY of 54% at a molar activity of g.t. 7.6 TBq/µmol. The radiofluorinated SiRs exhibit in vitro stabilities g.t. 70% after two hours in human serum. The first described radiolabeled SiRs are a promising step toward their further development as multimodal PET/SPECT-NIR imaging agents for planning and subsequent imaging-guided oncological surgery.