Optimizing tumor targeting of the lipophilic EGFR-binding radiotracer SKI 243 using a liposomal nanoparticle delivery system

Imaging drug delivery to the lungs: Methods and applications in oncology

Direct delivery to the lung via inhalation is arguably one of the most logical approaches to treat lung cancer using drugs. However, despite significant efforts and investment in this area, this strategy has not progressed in clinical trials. Imaging drug delivery is a powerful tool to understand and develop novel drug delivery strategies. In this review we focus on imaging studies of drug delivery by the inhalation route, to provide a broad overview of the field to date and attempt to better understand the complexities of this route of administration and the significant barriers that it faces, as well as its advantages. We start with a discussion of the specific challenges for drug delivery to the lung via inhalation. We focus on the barriers that have prevented progress of this approach in oncology, as well as the most recent developments in this area. This is followed by a comprehensive overview of the different imaging modalities that are relevant to lung drug delivery, including nuclear imaging, X-ray imaging, magnetic resonance imaging, optical imaging and mass spectrometry imaging. For each of these modalities, examples from the literature where these techniques have been explored are provided. Finally the different applications of these technologies in oncology are discussed, focusing separately on small molecules and nanomedicines. We hope that this comprehensive review will be informative to the field and will guide the future preclinical and clinical development of this promising drug delivery strategy to maximise its therapeutic potential.

Synthesis of Prussian Blue Nanoparticles and Their Antibacterial, Antiinflammation and Antitumor Applications

In recent years, Prussian blue nanoparticles (PBNPs), also named Prussian blue nano-enzymes, have been shown to demonstrate excellent multi-enzyme simulation activity and anti-inflammatory properties, and can be used as reactive oxygen scavengers. Their good biocompatibility and biodegradability mean that they are ideal candidates for in vivo use. PBNPs are highly efficient electron transporters with oxidation and reduction activities. PBNPs also show considerable promise as nano-drug carriers and biological detection sensors owing to their huge specific surface area, good chemical characteristics, and changeable qualities, which might considerably increase the therapeutic impact. More crucially, PBNPs, as therapeutic and diagnostic agents, have made significant advances in biological nanomedicine. This review begins with a brief description of the synthesis methods of PBNPs, then focuses on the applications of PBNPs in tissue regeneration and inflammation according to the different properties of PBNPs. This article will provide a timely reference for further study of PBNPs as therapeutic agents.

Transforming Nuclear Medicine with Nanoradiopharmaceuticals

Nuclear medicine is expected to make major advances in cancer diagnosis and therapy; tumor-targeted radiopharmaceuticals preferentially eradicate tumors while causing minimal damage to healthy tissues. The current scope of nuclear medicine can be significantly expanded by integration with nanomedicine, which utilizes nanoparticles for cancer diagnosis and therapy by capitalizing on the increased surface area-to-volume ratio, the passive/active targeting ability and high loading capacity, the greater interaction cross section with biological tissues, the rich surface properties of nanomaterials, the facile decoration of nanomaterials with a plethora of functionalities, and the potential for multiplexing several functionalities within one construct. This review provides a comprehensive discussion of nuclear nanomedicine using tumor-targeted nanoparticles for cancer radiation therapy with either pre-embedded radionuclides or nonradioactive materials which can be extrinsically triggered using various external nuclear particle sources to produce in situ radioactivity. In addition, it describes the prospect of combining nuclear nanomedicine with other modalities to enable synergistically enhanced combination therapies. The review also discusses advances in the fabrication of radionuclides as well as describes laser ablation technologies for producing nanoradiopharmaceuticals, which combine the ease of production with exceptional purity and rapid biodegradability, along with additional imaging or therapeutic functionalities. From a practical standpoint, these attributes of nanoradiopharmaceuticals may provide distinct advantages in diagnostic/therapeutic sensitivity and specificity, imaging resolution, and scalability of turnkey platforms. Coupling image-guided targeted radiation therapy with the possibility of in situ activation of nanomaterials as well as combining with other therapeutic modalities using a multifunctional nanoplatform could herald an era of exciting technological and therapeutic advances to radically transform the landscape of nuclear medicine. The review concludes with a discussion of current challenges and presents the authors' views on future opportunities to stimulate further research in this rewarding field of high societal impact.

Drug delivery, biodistribution and anti-EGFR activity: theragnostic nanoparticles for simultaneous in vivo delivery of tyrosine kinase inhibitors and kinase activity biosensors

In vivo delivery of small molecule therapeutics to cancer cells, assessment of the selectivity of administration, and measuring the efficacity of the drug in question at the molecule level, are important ongoing challenges in developing new classes of cancer chemotherapeutics. One approach that has the potential to provide targeted delivery, tracking of biodistribution and readout of efficacy, is to use multimodal theragnostic nanoparticles to deliver the small molecule therapeutic. In this paper, we report the development of targeted theragnostic lipid/peptide/DNA lipopolyplexes. These simultaneously deliver an inhibitor of the EGFR tyrosine kinase, and plasmid DNA coding for a Crk-based biosensor, Picchu-X, which when expressed in the target cells can be used to quantify the inhibition of EGFR in vivo in a mouse colorectal cancer xenograft model. Reversible bioconjugation of a known analogue of the tyrosine kinase inhibitor Mo-IPQA to a cationic peptide, and co-formulation with peptides containing both EGFR-binding and cationic sequences, allowed for good levels of inhibitor encapsulation with targeted delivery to LIM1215 colon cancer cells. Furthermore, high levels of expression of the Picchu-X biosensor in the LIM1215 cells in vivo allowed us to demonstrate, using fluorescence lifetime microscopy (FLIM)-based biosensing, that EGFR activity can be successfully suppressed by the tyrosine kinase inhibitor, released from the lipopolyplexes. Finally, we measured the biodistribution of lipopolyplexes containing 125I-labelled inhibitors and were able to demonstrate that the lipopolyplexes gave significantly higher drug delivery to the tumors compared with free drug.

Comparison of photoacoustic and fluorescence tomography for the in vivo imaging of ICG-labelled liposomes in the medullary cavity in mice

Few reports quantitatively compare the performance of photoacoustic tomography (PAT) versus fluorescence molecular tomography (FMT) in vivo. We compared both modalities for the detection of signals from injected ICG liposomes in the tibial medullary space of 10 BALB/c mice in vivo and ex vivo. Signals significantly correlated between modalities (R² = 0.69) and within each modality in vivo versus ex vivo (PAT: R² = 0.70, FMT: R² = 0.76). Phantom studies showed that signals at 4 mm depth are detected down to 3.3 ng ICG by PAT and 33 ng by FMT, with a nominal spatial resolution below 0.5 mm in PAT and limited to 1 mm in FMT. Our study demonstrates comparable in vivo sensitivity, but superior ex vivo sensitivity and in vivo resolution for our ICG liposomes of the VevoLAZR versus the FMT2500. PAT provides a useful new tool for the high-resolution imaging of bone marrow signals, for example for monitoring drug delivery.

Nuclear imaging of liposomal drug delivery systems: A critical review of radiolabelling methods and applications in nanomedicine

The integration of nuclear imaging with nanomedicine is a powerful tool for efficient development and clinical translation of liposomal drug delivery systems. Furthermore, it may allow highly efficient imaging-guided personalised treatments. In this article, we critically review methods available for radiolabelling liposomes. We discuss the influence that the radiolabelling methods can have on their biodistribution and highlight the often-overlooked possibility of misinterpretation of results due to decomposition in vivo. We stress the need for knowing the biodistribution/pharmacokinetics of both the radiolabelled liposomal components and free radionuclides in order to confidently evaluate the images, as they often share excretion pathways with intact liposomes (e.g. phospholipids, metallic radionuclides) and even show significant tumour uptake by themselves (e.g. some radionuclides). Finally, we describe preclinical and clinical studies using radiolabelled liposomes and discuss their impact in supporting liposomal drug development and clinical translation in several diseases, including personalised nanomedicine approaches.

Detecting intratumoral heterogeneity of EGFR activity by liposome-based in vivo transfection of a fluorescent biosensor

Despite decades of research in the epidermal growth factor receptor (EGFR) signalling field, and many targeted anti-cancer drugs that have been tested clinically, the success rate for these agents in the clinic is low, particularly in terms of the improvement of overall survival. Intratumoral heterogeneity is proposed as a major mechanism underlying treatment failure of these molecule-targeted agents. Here we highlight the application of fluorescence lifetime microscopy (FLIM)-based biosensing to demonstrate intratumoral heterogeneity of EGFR activity. For sensing EGFR activity in cells, we used a genetically encoded CrkII-based biosensor which undergoes conformational changes upon tyrosine-221 phosphorylation by EGFR. We transfected this biosensor into EGFR-positive tumour cells using targeted lipopolyplexes bearing EGFR-binding peptides at their surfaces. In a murine model of basal-like breast cancer, we demonstrated a significant degree of intratumoral heterogeneity in EGFR activity, as well as the pharmacodynamic effect of a radionuclide-labeled EGFR inhibitor in situ. Furthermore, a significant correlation between high EGFR activity in tumour cells and macrophage-tumour cell proximity was found to in part account for the intratumoral heterogeneity in EGFR activity observed. The same effect of macrophage infiltrate on EGFR activation was also seen in a colorectal cancer xenograft. In contrast, a non-small cell lung cancer xenograft expressing a constitutively active EGFR conformational mutant exhibited macrophage proximity-independent EGFR activity. Our study validates the use of this methodology to monitor therapeutic response in terms of EGFR activity. In addition, we found iNOS gene induction in macrophages that are cultured in tumour cell-conditioned media as well as an iNOS activity-dependent increase in EGFR activity in tumour cells. These findings point towards an immune microenvironment-mediated regulation that gives rise to the observed intratumoral heterogeneity of EGFR signalling activity in tumour cells in vivo.

Self-assembled PEG–carboxymethylcellulose nanoparticles/α-cyclodextrin hydrogels for injectable and thermosensitive drug delivery

Novel cellulose hydrogels based on the inclusion complex between α-cyclodextrin and binary-drug loaded nanoparticles (carboxymethylcellulose–betulinic acid/hydroxycamptothecine nanoparticles) were prepared in aqueous media for the first time.

Ginsenoside nanoparticle: a new green drug delivery system

Ginsenoside Rb1 is shown to self-assemble with anticancer drugs to form stable nanoparticles, which have greater anticancer effectsin vitroandin vivothan the free drugs.

Recent Advances in the Development and Application of Radiolabeled Kinase Inhibitors for PET Imaging

Over the last 20 years, intensive investigation and multiple clinical successes targeting protein kinases, mostly for cancer treatment, have identified small molecule kinase inhibitors as a prominent therapeutic class. In the course of those investigations, radiolabeled kinase inhibitors for positron emission tomography (PET) imaging have been synthesized and evaluated as diagnostic imaging probes for cancer characterization. Given that inhibitor coverage of the kinome is continuously expanding, in vivo PET imaging will likely find increasing applications for therapy monitoring and receptor density studies both in- and outside of oncological conditions. Early investigated radiolabeled inhibitors, which are mostly based on clinically approved tyrosine kinase inhibitor (TKI) isotopologues, have now entered clinical trials. Novel radioligands for cancer and PET neuroimaging originating from novel but relevant target kinases are currently being explored in preclinical studies. This article reviews the literature involving radiotracer design, radiochemistry approaches, biological tracer evaluation and nuclear imaging results of radiolabeled kinase inhibitors for PET reported between 2010 and mid-2015. Aspects regarding the usefulness of pursuing selective vs. promiscuous inhibitor scaffolds and the inherent challenges associated with intracellular enzyme imaging will be discussed.

Epidermal growth factor receptor-targeted peptide conjugated phospholipid micelles for doxorubicin delivery

Specific targeting of tumor cells to achieve higher drug levels in tumor tissue and to overcome side effects is the major goal in cancer chemotherapy. In this study, we used a tumor targeting peptide, GE11, to conjugate onto the surface of doxorubicin encapsulated phospholipid micelles. The GE11 peptide triggered specific binding to epidermal growth factor receptor (EGFR), leading to enhanced cellular uptake and cytotoxicity in vitro and highly accumulation in the tumors in vivo. The results indicated that GE11 conjugated phospholipid micelles should have potential applications in cancer therapy.

A novel self-assembled targeted nanoparticle platform based on carboxymethylcellulose co-delivery of anticancer drugs

The folate–PEG–carboxymethylcellulose–betulinic acid was synthesized by introducing folate, PEG, and betulinic acid into carboxymethylcellulose, and then self-assembled into nanoparticles with HCPT being encapsulated.

Self-assembled targeted folate-conjugated eight-arm-polyethylene glycol–betulinic acid nanoparticles for co-delivery of anticancer drugs

Folate-8arm-PEG–betulinic acid nanoparticles prepared via a self-assembly process are stable in circulation, resulting in the EPR effect of solid tumors, and are efficiently internalized by cancer cells.

Cellulose-graft-poly(l-lactic acid) nanoparticles for efficient delivery of anti-cancer drugs

BA-loaded cellulose-graft-poly(l-lactic acid) nanoparticles were fabricated by employing cellulose and poly(l-lactic acid) as materials and betulinic acid as a model drug. The nanoparticles have appropriate size and excellent antitumor activities.

Prussian blue nanoparticles as nanocargoes for delivering DNA drugs to cancer cells

We studied the use of Prussian blue nanoparticles (PBNPs) as novel nanocarriers for sending DNA drugs into cancer cells. 11-mercaptoundecanoic acid (MUA) was used to functionalize the surfaces of PBNPs (nanocubes with an average dimension of 75 nm) for subsequent covalent grafting of a 33-mer DNA drug with a FAM reporter at the 3' end. The PBNPs synthesis and DNA drug conjugation were characterized by transmission electron microscopy (TEM) and Fourier-transform infrared absorption (FTIR), respectively. The drug was a decoy oligodeoxynucleotide (dODN) that inhibits the signal transducer and activator of transcription 3 (STAT3). The DNA-PBNPs drug (dODN@MUA-PBNPs) was delivered into human prostate carcinoma 22rv1 cells by endocytosis in vitro as confirmed by confocal fluorescence microscopy. MTT cell viability assays were carried out to assess the effect of the DNA-PBNPs drug. The results showed that the dODN molecules were successfully conjugated to the MUA modified PBNPs via amide and/or disulfide bond formation and could thus be successfully delivered into the cancer cells. The control experiments showed that the unconjugated dODN molecules were not able to enter the cancer cells no matter whether non-functionalized PBNPs were present or not. It was also found that the DNA-PBNPs drugs were internalized and then distributed homogeneously throughout the cell, including cytoplasmic and nucleic regions, after endocytosis. The cancer cell-killing ability increased with the amount of dODN conjugated on PBNPs and the dosage of DNA-PBNPs drug internalized.

Receptor-based targeting of therapeutics

Receptor-based targeting of therapeutics may be a fascinating proposition to improve the therapeutic efficacy of encapsulated drugs. The development of safe and effective nanomedicines is a prerequisite in the current nanotechnological scenario. Currently, the surface engineering of nanocarriers has attracted great attention for targeted therapeutic delivery by selective binding of targeting ligand to the specific receptors present on the surface of cells. In this review, we have discussed the current status of various receptors such as transferrin, lectoferrin, lectin, folate, human EGF receptor, scavenger, nuclear and integrin, which are over-expressed on the surface of cancer cells; along with the relevance of targeted delivery systems such as nanoparticles, polymersomes, dendrimers, liposomes and carbon nanotubes. The review also focuses on the effective utilization of receptor-based targeted delivery systems for the management of cancer in effective ways by minimizing the drug-associated side effects and improving the therapeutic efficacy of developed nano-architectures.

(89)Zr-labeled paramagnetic octreotide-liposomes for PET-MR imaging of cancer

PURPOSE

Dual-modality PET/MR platforms add a new dimension to patient diagnosis with high resolution, functional, and anatomical imaging. The full potential of this emerging hybrid modality could be realized by using a corresponding dual-modality probe. Here, we report pegylated liposome (LP) formulations, housing a MR T(1) contrast agent (Gd) and the positron-emitting (89)Zr (half-life: 3.27 days), for simultaneous PET and MR tumor imaging capabilities.

METHODS

(89)Zr oxophilicity was unexpectedly found advantageous for direct radiolabeling of preformed paramagnetic LPs. LPs were conjugated with octreotide to selectively target neuroendocrine tumors via human somatostatin receptor subtype 2 (SSTr2). (89)Zr-Gd-LPs and octreotide-conjugated homolog were physically, chemically and biologically characterized.

RESULTS

(89)Zr-LPs showed reasonable stability over serum proteins and chelator challenges for proof-of-concept in vitro and in vivo investigations. Nuclear and paramagnetic tracking quantified superior SSTr2-recognition of octreotide-LP compared to controls.

CONCLUSIONS

This study demonstrated SSTr2-targeting specificity along with direct chelator-free (89)Zr-labeling of LPs and dual PET/MR imaging properties.

The use and importance of liposomes in positron emission tomography

Among different imaging modalities, Positron Emission Tomography (PET) gained importance in routine hospital practice depending on ability to diagnose diseases in early stages and tracing of therapy by obtaining metabolic information. The combination of PET with Computed Tomography (CT) forms hybrid imaging modality that gives chance to obtain better images having higher resolution by fusing both functional and anatomical images in the same imaging modality at the same time. Therefore, better contrast agents are essentially needed. The advance in research about developing drug delivery systems as specific nanosized targeted systems gained an additional importance for obtaining better diagnosis and therapy of different diseases. Liposomes appear to be more attractive drug delivery systems in delivering either drugs or imaging ligands to target tissue or organ of diseases with higher accumulation by producing in nano-scale, long circulating by stealth effect and specific targeting by modifying with specific ligands or markers. The combination of positron emitting radionuclides with liposomes are commonly in research level nowadays and there is no commercially available liposome formulation for PET imaging. However by conjugating positron emitter radionuclide with liposomes can form promising diagnostic agents for improved diagnosis and following up treatments by increasing image signal/contrast in the target tissue in lower concentrations by specific targeting as the most important advantage of liposomes. More accurate and earlier diagnosis of several diseases can be obtained even in molecular level with the use of stable and effectively radiolabeled molecular target specific nano sized liposomes with longer half-lived positron emitting radionuclides.

Liposomes and inorganic nanoparticles for drug delivery and cancer imaging

Recently, there have been several advancements in material sciences and nanosciences. At the moment these new techniques are slowly entering into clinical settings in drug delivery and imaging. In this review, we will look more closely at the applications that are at the forefront of this translation and examine critical aspects that are involved in the process. Nanoparticles have been increasingly used in clinical settings for drug delivery over the past two decades. Lipid-based nanoparticles are front-runners, but other innovative strategies, such as small inorganic nanoparticles, are entering into the field, particularly for imaging applications. Lipid-based nanoparticles can be metabolized and consumed by the body and are regarded as safe for clinical use. They are usually large with hydrodynamic diameters of approximately 100-200 nm; however, phospholipid-containing particles such as microbubbles with diameters as low as 10 microm in size and micelles with diameters of 10-40 nm can also be used. Hollow liposomes with a large aqueous inner cavity can carry high payloads of drugs and imaging moieties, but are easily trapped by liver kupffer cells and can result in lower tissue penetration rates. New classes of particles with hydrodynamic diameters of < 10 nm, which are cleared by the kidneys, have recently been developed. These particles have been used primarily for imaging applications since they offer only small loading capacities for drugs. However, new strategies such as surface-coupled prodrugs have been developed to facilitate drug delivery in small nanoparticles. We describe different strategies for targeted delivery, imaging and controlled release, and discuss the ability of small inorganic particles as well as larger nanoparticles to be used broadly in human diagnostics and drug delivery.

Nanoparticles labeled with positron emitting nuclides: advantages, methods, and applications

Over the past decade, positron emitter labeled nanoparticles have been widely used in and substantially improved for a range of diagnostic biomedical research. However, given growing interest in personalized medicine and translational research, a major challenge in the field will be to develop disease-specific nanoprobes with facile and robust radiolabeling strategies and that provide imaging stability, enhanced sensitivity for disease early stage detection, optimized in vivo pharmacokinetics for reduced nonspecific organ uptake, and improved targeting for elevated efficacy. This review briefly summarizes the major applications of nanoparticles labeled with positron emitters for cardiovascular imaging, lung diagnosis, and tumor theranostics.

Recent advances in stealth coating of nanoparticle drug delivery systems

Modifying surfaces of nanoparticles (NPs) with polyethylene glycol (PEG), the so-called PEGylation, is the most commonly used method for reducing premature clearance of NPs from the circulation. However, several reports point out that PEGylation may negatively influence the performance of NPs as a drug carrier. Alternative surface modification strategies, including substitute polymers, conditional removal of PEG, and biomimetic surface modification, may provide solutions for the limitations of PEG.

Specific delivery of kinase inhibitors in nonmalignant and malignant diseases

INTRODUCTION

Kinase inhibitors have been hailed as a breakthrough in the treatment of cancer. Extensive research is now being devoted to the development of kinase inhibitors as a treatment for many nonmalignant diseases. However, the use of kinase inhibitors in both malignant and nonmalignant diseases is also associated with side effects and the development of resistance. It may be worthwhile to explore whether cell-specific delivery of kinase inhibitors improves therapeutic efficacy and reduces side effects.

AREAS COVERED

This review aims to provide an overview of the preclinical studies performed to examine the specific targeting of kinase inhibitors in vitro and in vivo. It gives an introduction to kinase signaling pathways induced during disease, along with the possible problems associated with their inhibition. It also discusses the studies on specific delivery and shows that altering the specificity of kinase inhibitors by targeting methods improves their effectivity and safety.

EXPERT OPINION

Compared with the delivery of cytotoxic compounds, the specific delivery of kinase inhibitors has not yet been studied extensively. The studies discussed in this review provide an insight into methods used to target kinase inhibitors to different organs. The targeting of different kinase inhibitors has improved their therapeutic possibilities, but many questions still remain to be studied.