Multifunctional nanoemulsion platform for imaging guided therapy evaluated in experimental cancer

Inorganic nanocrystals as contrast agents in MRI: synthesis, coating and introduction of multifunctionality

Inorganic nanocrystals have myriad applications in medicine, including their use as drug or gene delivery complexes, therapeutic hyperthermia agents, in diagnostic systems and as contrast agents in a wide range of medical imaging techniques. In MRI, nanocrystals can produce contrast themselves, with iron oxides having been the most extensively explored, or can be given a coating that generates MR contrast, for example gold nanoparticles coated with gadolinium chelates. These MR-active nanocrystals can be used for imaging of the vasculature, liver and other organs, as well as molecular imaging, cell tracking and theranostics. As a result of these exciting applications, the synthesis and rendering of these nanocrystals as water soluble and biocompatible are therefore highly desirable. We discuss aqueous phase and organic phase methods for the synthesis of inorganic nanocrystals, such as gold, iron oxides and quantum dots. The pros and cons of the various methods are highlighted. We explore various methods for making nanocrystals biocompatible, i.e. direct synthesis of nanocrystals coated with biocompatible coatings, ligand substitution, amphiphile coating and embedding in carrier matrices that can be made biocompatible. Various examples are highlighted and their applications explained. These examples signify that the synthesis of biocompatible nanocrystals with controlled properties has been achieved by numerous research groups and can be applied to a wide range of applications. Therefore, we expect to see reports of preclinical applications of ever more complex MRI-active nanoparticles and their wider exploitation, as well as in novel clinical settings.

Cytokines as biomarkers of nanoparticle immunotoxicity

Nanoscale objects, whether of biologic origin or synthetically created, are being developed into devices for a variety of bionanotechnology diagnostic and pharmaceutical applications. However, the potential immunotoxicity of these nanomaterials and mechanisms by which they may induce adverse reactions have not received sufficient attention. Nanomaterials, depending on their characteristics and compositions, can interact with the immune system in several ways and either enhance or suppress immune system function. Cytokines perform pleiotropic functions to mediate and regulate the immune response and are generally recognized as biomarkers of immunotoxicity. While the specificity and validity of certain cytokines as markers of adverse immune response has been established for chemicals, small and macromolecular drugs, research on their applicability for predicting and monitoring the immunotoxicity of engineered nanomaterials is still ongoing. The goal of this review is to provide guidelines as to important cytokines that can be utilized for evaluating the immunotoxicity of nanomaterials and to highlight the role of those cytokines in mediating adverse reactions, which is of particular importance for the clinical development of nanopharmaceuticals and other nanotechnology-based products. Importantly, the rational design of nanomaterials of low immunotoxicity will be discussed, focusing on synthetic nanodevices, with emphasis on both the nanoparticle-forming materials and the embedded cargoes.

Cytokines as biomarkers of nanoparticle immunotoxicity

Nanoscale objects, whether of biologic origin or synthetically created, are being developed into devices for a variety of bionanotechnology diagnostic and pharmaceutical applications. However, the potential immunotoxicity of these nanomaterials and mechanisms by which they may induce adverse reactions have not received sufficient attention. Nanomaterials, depending on their characteristics and compositions, can interact with the immune system in several ways and either enhance or suppress immune system function. Cytokines perform pleiotropic functions to mediate and regulate the immune response and are generally recognized as biomarkers of immunotoxicity. While the specificity and validity of certain cytokines as markers of adverse immune response has been established for chemicals, small and macromolecular drugs, research on their applicability for predicting and monitoring the immunotoxicity of engineered nanomaterials is still ongoing. The goal of this review is to provide guidelines as to important cytokines that can be utilized for evaluating the immunotoxicity of nanomaterials and to highlight the role of those cytokines in mediating adverse reactions, which is of particular importance for the clinical development of nanopharmaceuticals and other nanotechnology-based products. Importantly, the rational design of nanomaterials of low immunotoxicity will be discussed, focusing on synthetic nanodevices, with emphasis on both the nanoparticle-forming materials and the embedded cargoes.

Applications and potential toxicity of magnetic iron oxide nanoparticles

Owing to their unique physical and chemical properties, magnetic iron oxide nanoparticles have become a powerful platform in many diverse aspects of biomedicine, including magnetic resonance imaging, drug and gene delivery, biological sensing, and hyperthermia. However, the biomedical applications of magnetic iron oxide nanoparticles arouse serious concerns about their pharmacokinetics, metabolism, and toxicity. In this review, the updated research on the biomedical applications and potential toxicity of magnetic iron oxide nanoparticles is summarized. Much more effort is required to develop magnetic iron oxide nanoparticles with improved biocompatible surface engineering to achieve minimal toxicity, for various applications in biomedicine.

Tumor angiogenesis phenotyping by nanoparticle-facilitated magnetic resonance and near-infrared fluorescence molecular imaging

One of the challenges of tailored antiangiogenic therapy is the ability to adequately monitor the angiogenic activity of a malignancy in response to treatment. The α(v)β(3) integrin, highly overexpressed on newly formed tumor vessels, has been successfully used as a target for Arg-Gly-Asp (RGD)-functionalized nanoparticle contrast agents. In the present study, an RGD-functionalized nanocarrier was used to image ongoing angiogenesis in two different xenograft tumor models with varying intensities of angiogenesis (LS174T > EW7). To that end, iron oxide nanocrystals were included in the core of the nanoparticles to provide contrast for T(2)*-weighted magnetic resonance imaging (MRI), whereas the fluorophore Cy7 was attached to the surface to enable near-infrared fluorescence (NIRF) imaging. The mouse tumor models were used to test the potential of the nanoparticle probe in combination with dual modality imaging for in vivo detection of tumor angiogenesis. Pre-contrast and post-contrast images (4 hours) were acquired at a 9.4-T MRI system and revealed significant differences in the nanoparticle accumulation patterns between the two tumor models. In the case of the highly vascularized LS174T tumors, the accumulation was more confined to the periphery of the tumors, where angiogenesis is predominantly occurring. NIRF imaging revealed significant differences in accumulation kinetics between the models. In conclusion, this technology can serve as an in vivo biomarker for antiangiogenesis treatment and angiogenesis phenotyping.

Graphene oxide modified PLA microcapsules containing gold nanoparticles for ultrasonic/CT bimodal imaging guided photothermal tumor therapy

Theranostic microcapsules were successfully fabricated by introducing gold nanoparticles into poly(lactic acid) microcapsules through a double-microemulsion method, followed by depositing graphene oxide onto the microcapsule surface via electrostatic layer-by-layer self-assembly technique. It was proved that the obtained microcapsules could serve as a contrast agent to simultaneously enhance US imaging and X-ray CT imaging greatly both in vitro and in vivo. In addition, the in vivo therapeutic examinations showed that the microcapsule was an effective agent for photothermal therapy of cancer. The near-infrared laser light ablated the tumor completely within 9 days in the presence of the microcapsules and the tumor growth inhibition was 83.8%. The combination of real-time ultrasound with 3-D computed tomography through a single microcapsule agent is very helpful for accurately interpreting the obtained images, identifying the size and location of the tumor, as well as guiding and monitoring the photothermal therapy. Simultaneously, the effectiveness of photothermal therapy could be evaluated by the combined US and CT imaging enhanced by the microcapsule agent. Such a versatile microcapsule system might bring opportunities to the next generation of multimodal imaging guided cancer therapy.

Engineering multifunctional nanoparticles: all-in-one versus one-for-all

Multifunctional nanoparticles have been developed to overcome the conventional hurdles associated with the diagnosis and treatment of disease. However, there are often caveats involved with the development and clinical translation of multifunctional nanoparticles largely regarding the notion that additional functionality increases nanoparticle complexity. Here, we discuss two design concepts, a conventional approach, 'all-in-one', and introduce the concept of 'one-for-all' to suggest that multifunctionality does not necessarily result in multicomponent complex nanoparticles. This review focuses on the design concepts of all-in-one and one-for-all with examples of each approach and a discussion on the implications for clinical translation.

Nanomaterials for photo-based diagnostic and therapeutic applications

Photo-based diagnosis and treatment methods are gaining prominence due to increased spatial imaging resolution, minimally invasive modalities involved as well as localized treatment. Recently, nanoparticles (NPs) have been developed and used in photo-based therapeutic applications. While some nanomaterials have inherent photo-based imaging capabilities, others including polymeric NPs act as nanocarriers to deliver various fluorescent dyes or photosensitizers for photoimaging and therapeutic applications. These applications can vary from Magnetic Resonance Imaging (MRI) and optical imaging to photothermal therapy (PTT) and chemotherapy. Materials commonly used for development of photo-based NPs ranges from metal-based (gold, silver and silica) to polymer-based (chitosan, dextran, poly ethylene glycol (PEG) and poly lactic-co-glycolic acid (PLGA)). Recent research has paved the way for multi-modal 'theranostic' (a combination of therapy and diagnosis) nano-carriers capable of active targeting using cell-specific ligands and carrying multiple therapeutic and imaging agents for accurate diagnosis and controlled drug delivery. This review summarizes the different materials used today to synthesize photo-based NPs, their diagnostic and therapeutic applications as well as the current challenges faced in bringing these novel nano-carriers into clinical practices.

Cyclooxgenase-2 inhibiting perfluoropoly (ethylene glycol) ether theranostic nanoemulsions-in vitro study

Cylcooxgenase-2 (COX-2) expressing macrophages, constituting a major portion of tumor mass, are involved in several pro-tumorigenic mechanisms. In addition, macrophages are actively recruited by the tumor and represent a viable target for anticancer therapy. COX-2 specific inhibitor, celecoxib, apart from its anticancer properties was shown to switch macrophage phenotype from tumor promoting to tumor suppressing. Celecoxib has low aqueous solubility, which may limit its tumor inhibiting effect. As opposed to oral administration, we propose that maximum anticancer effect may be achieved by nanoemulsion mediated intravenous delivery. Here we report multifunctional celecoxib nanoemulsions that can be imaged by both near-infrared fluorescence (NIRF) and ¹⁹F magnetic resonance. Celecoxib loaded nanoemulsions showed a dose dependent uptake in mouse macrophages as measured by ¹⁹F NMR and NIRF signal intensities of labeled cells. Dramatic inhibition of intracellular COX-2 enzyme was observed in activated macrophages upon nanoemulsion uptake. COX-2 enzyme inhibition was statistically equivalent between free drug and drug loaded nanoemulsion. However, nanoemulsion mediated drug delivery may be advantageous, helping to avoid systemic exposure to celecoxib and related side effects. Dual molecular imaging signatures of the presented nanoemulsions allow for future in vivo monitoring of the labeled macrophages and may help in examining the role of macrophage COX-2 inhibition in inflammation-cancer interactions. These features strongly support the future use of the presented nanoemulsions as anti-COX-2 theranostic nanomedicine with possible anticancer applications.

Molecular MRI of the Cardiovascular System in the Post-NSF Era

Two new molecular MRI agents have been approved for clinical use within the last 3 years, and a third agent has completed phase-2 clinical trials. A wealth of preclinical data is also emerging on the general safety of many molecular MR imaging agents. In addition, since the guidelines to avoid nephrogenic systemic fibrosis (NSF) were adopted, at most institutions no new cases of NSF have been reported. Nevertheless, in the post-NSF environment, both those developing and using molecular MR imaging agents need to be increasingly aware of safety issues. This awareness should begin with the design of the agent and, even in early preclinical studies, the demonstration of safety and efficacy should both be given high priority. In this review we discuss some of the issues relevant to the design of safe molecular MR imaging agents and highlight the excellent safety profile of those agents that have been used clinically to date.

Theranostic probe based on lanthanide-doped nanoparticles for simultaneous in vivo dual-modal imaging and photodynamic therapy

Dual-modal in vivo tumor imaging and photodynamic therapy using hexagonal NaYF(4):Yb,Er/NaGdF(4) core-shell upconverting nanoparticles combined with a photosensitizer, chlorin e6, is reported. Tumors can be clearly observed not only in the upconversion luminescence image but also in the magnetic resonance image. In vivo photodynamic therapy by systemic administration is demonstrated under 980 nm irradiation.

Chains, sheets, and droplets: assemblies of hydrophobic gold nanocrystals with saturated phosphatidylcholine lipid and squalene

Assemblies of saturated 1,2-diacylphosphatidylcholine lipid and hydrophobic dodecanethiol-capped 1.8 nm diameter gold nanocrystals were studied as a function of lipid chain length and the addition of the naturally occurring oil, squalene. The gold nanocrystals formed various lipid-stabilized agglomerates, sometimes fusing with lipid vesicle bilayers. The nanocrystal assembly structure depended on the hydrocarbon chain length of the lipid fatty acids. The lipid with the shortest fatty acid length studied, dilauroylphosphatidylcholine, created extended chains of gold nanocrystals. The lipid with slightly longer fatty acid chains created planar sheets of nanocrystals. Further increases of the fatty acid chain length led to spherical agglomerates. The inclusion of squalene led to lipid- and nanocrystal-coated oil droplets.

Surface-enhanced Raman spectroscopy to probe photoreaction pathways and kinetics of isolated reactants on surfaces: flat versus curved substrates

We identify and control the photoreaction paths of self-assembled monolayers (SAMs) of thiolate-linked anthracene phenylethynyl molecules on Au substrate surfaces, and study the effects of nanoscale morphology of substrates on regioselective photoreactions. Two types of morphologies, atomically flat and curved, are produced on Au surfaces by controlling substrate structure and metal deposition. We employ surface-enhanced Raman spectroscopy (SERS), combined with Raman mode analyses using density functional theory, to identify the different photoreaction paths and to track the photoreaction kinetics and efficiencies of molecules in monolayers. The SAMs on curved surfaces exhibit dramatically lower regioselective photoreaction kinetics and efficiencies than those on atomically flat surfaces. This result is attributed to the increased intermolecular distances and variable orientations on the curved surfaces. Better understanding of the morphological effects of substrates will enable control of nanoparticle functionalization in ligand exchange in targeted delivery of therapeutics and theranostics and in catalysis.

Nanotheranostics for personalized medicine

The application of nanotechnology in the biomedical field, known as nanomedicine, has gained much interest in the recent past, as versatile strategy for selective drug delivery and diagnostic purposes. The already encouraging results obtained with monofunctional nanomedicines have directed the efforts of the scientists towards the creation of "nanotheranostics" (i.e. theranostic nanomedicines) which integrate imaging and therapeutic functions in a single platform. Nanotheranostics hold great promises because they combine the simultaneous non-invasive diagnosis and treatment of diseases with the exciting possibility to monitor in real time drug release and distribution, thus predicting and validating the effectiveness of the therapy. Due to these features nanotheranostics are extremely attractive for optimizing treatment outcomes in cancer and other severe diseases. The following step is the attempt to use nanotheranostics for performing a real personalized medicine which will tailor optimized treatment to each patient, taking into account the individual variability. Clinical application of nanotheranostics would enable earlier detection and treatment of diseases and earlier assessment of the response, thus allowing screening for patients which would potentially respond to therapy and have higher possibilities of a favorable outcome. This concept makes nanotheranostics extremely appealing to elaborate personalized therapeutic protocols for achieving the maximal benefit along with a high safety profile. Among the several systems developed up to now, this review focuses on the nanotheranostics which, due to the promising results, show the highest potential of translation to clinical applications and may transform into concrete practice the concept of personalized nanomedicine.

The effect of nanoparticle polyethylene glycol surface density on ligand-directed tumor targeting studied in vivo by dual modality imaging

The development and application of nanoparticles as in vivo delivery vehicles for therapeutic and/or diagnostic agents has seen a drastic growth over the last decades. Novel imaging techniques allow real-time in vivo study of nanoparticle accumulation kinetics at the level of the cell and targeted tissue. Successful intravenous application of such nanocarriers requires a hydrophilic particle surface coating, of which polyethylene glycol (PEG) has become the most widely studied and applied. In the current study, the effect of nanoparticle PEG surface density on the targeting efficiency of ligand-functionalized nanoemulsions was investigated. We synthesized 100 nm nanoemulsions with a PEG surface density varying from 5 to 50 mol %. Fluorescent and paramagnetic lipids were included to allow their multimodal detection, while RGD peptides were conjugated to the PEG coating to obtain specificity for the α(v)β(3)-integrin. The development of a unique experimental imaging setup allowed us to study, in real time, nanoparticle accumulation kinetics at (sub)-cellular resolution in tumors that were grown in a window chamber model with confocal microscopy imaging, and at the macroscopic tumor level in subcutaneously grown xenografts with magnetic resonance imaging. Accumulation in the tumor occurred more rapidly for the targeted nanoemulsions than for the nontargeted versions, and the PEG surface density had a strong effect on nanoparticle targeting efficiency. Counterintuitively, yet consistent with the PEG density conformation models, the highest specificity and targeting efficiency was observed at a low PEG surface density.

Noninvasive monitoring of orthotopic glioblastoma therapy response using RGD-conjugated iron oxide nanoparticles

Noninvasive imaging techniques have been considered important strategies in the clinic to monitor tumor early response to therapy. In the present study, we applied RGD peptides conjugated to iron oxide nanoparticles (IONP-RGD) as contrast agents in magnetic resonance imaging (MRI) to noninvasively monitor the response of a vascular disrupting agent VEGF(121)/rGel in an orthotopic glioblastoma model. RGD peptides were firstly coupled to IONPs coated with a crosslinked PEGylated amphiphilic triblock copolymer. In vitro binding assays confirmed that cellular uptake of particles was mainly dependent on the interaction between RGD and integrin α(v)β(3) of human umbilical vein endothelial cells (HUVEC). The tumor targeting of IONP-RGD was observed in an orthotopic U87 glioblastoma model. Finally, noninvasive monitoring of the tumor response to VEGF(121)/rGel therapy at early stages of treatment was successfully accomplished using IONP-RGD as a contrast agent for MRI, a superior method over common anatomical approaches which are based on tumor size measurements. This preclinical study can accelerate anticancer drug development and promote clinical translation of nanoprobes.

Engineering of lipid-coated PLGA nanoparticles with a tunable payload of diagnostically active nanocrystals for medical imaging

Polylactic-co-glycolic acid (PLGA) based nanoparticles are biocompatible and biodegradable and therefore have been extensively investigated as therapeutic carriers. Here, we engineered diagnostically active PLGA nanoparticles that incorporate high payloads of nanocrystals into their core for tunable bioimaging features. We accomplished this through esterification reactions of PLGA to generate polymers modified with nanocrystals. The PLGA nanoparticles formed from modified PLGA polymers that were functionalized with either gold nanocrystals or quantum dots exhibited favorable features for computed tomography and optical imaging, respectively.

Nanoclusters of iron oxide: effect of core composition on structure, biocompatibility, and cell labeling efficacy

Inorganic nanocrystals have a variety of applications in medicine. They may serve as contrast agents, therapeutics, and for in vitro diagnostics. Frequently, the synthesis route yields hydrophobically capped nanocrystals, which necessitates their subsequent coating to render a water-soluble and biocompatible probe. Biocompatibility is crucial for cellular imaging applications, which require large quantities of diagnostically active nanoparticles to be loaded into cells. We have previously reported the design and synthesis of a fluorescent and magnetic resonance imaging-detectable core-shell nanoparticle that encapsulates hydrophobically coated iron oxide nanocrystals. The core of soybean oil and iron oxide is covered by a shell mixture of phospholipids, some of which contained polyethylene glycol. Despite the biocompatibility of these components, we hypothesize that we can improve this formulation with respect to in vitro toxicity. To this aim, we measured the effect of six different core compositions on nanoparticle structure, cell labeling efficacy, and cell viability, as well as cell tracking potential. We methodically investigated the causes of toxicity and conclude that, even when combining biocompatible materials, the resulting formulation is not guaranteed to be biocompatible.

Multimodal imaging guided photothermal therapy using functionalized graphene nanosheets anchored with magnetic nanoparticles

In this work, a nanoscale reduced graphene oxide-iron oxide nanoparticle (RGO-IONP) complex is noncovalently functionalized with polyethylene glycol (PEG), obtaining a RGO-IONP-PEG nanocomposite with excellent physiological stability, strong NIR optical absorbance, and superparamagnetic properties. Using this theranostic nanoprobe, in-vivo triple modal fluorescence, photoacoustic, and magnetic resonance imaging are carried out, uncovering high passive tumor targeting, which is further used for effective photothermal ablation of tumors in mice.

NIR-labeled perfluoropolyether nanoemulsions for drug delivery and imaging

Theranostic nanoparticle development recently took center stage in the field of drug delivery nanoreagent design. Theranostic nanoparticles combine therapeutic delivery systems (liposomes, micelles, nanoemulsions, etc.) with imaging reagents (MRI, optical, PET, CT). This combination allows for non-invasive in vivo monitoring of therapeutic nanoparticles in diseased organs and tissues. Here, we report a novel perfluoropolyether (PFPE) nanoemulsion with a water-insoluble lipophilic drug. The formulation enables non-invasive monitoring of nanoemulsion biodistribution using two imaging modalities, (19)F MRI and near-infrared (NIR) optical imaging. The nanoemulsion is composed of PFPE-tyramide as a (19)F MRI tracer, hydrocarbon oil, surfactants, and a NIR dye. Preparation utilizes a combination of self-assembly and high energy emulsification methods, resulting in droplets with average diameter 180 nm and low polydispersity index (PDI less than 0.2). A model nonsteroidal anti-inflammatory drug (NSAID), celecoxib, was incorporated into the formulation at 0.2 mg/mL. The reported nanoemulsion's properties, including small particle size, visibility under (19)F NMR and NIR fluorescence spectroscopy, and the ability to carry drugs make it an attractive potential theranostic agent for cancer imaging and treatment.

Theranostic nanoplatforms for simultaneous cancer imaging and therapy: current approaches and future perspectives

Theranostics is a concept which refers to the integration of imaging and therapy. As an evolving new field, it is related to but different from traditional imaging and therapeutics. It embraces multiple techniques to arrive at a comprehensive diagnostic, in vivo molecular images and an individualized treatment regimen. More recently, there is a trend of tangling these efforts with emerging materials and nanotechnologies, in an attempt to develop novel platforms and methodologies to tackle practical issues in clinics. In this article, topics of rationally designed nanoparticles for the simultaneous imaging and therapy of cancer will be discussed. Several exemplary nanoparticle platforms such as polymeric nanoparticles, gold nanomaterials, carbon nanotubes, magnetic nanoparticles and silica nanoparticles will be elaborated on and future challenges of nanoparticle-based systems will be discussed.

Toward an image-guided microbeam radiation therapy using gadolinium-based nanoparticles

Ultrasmall gadolinium-based nanoparticles (GBNs) induce both a positive contrast for magnetic resonance imaging and a radiosentizing effect. The exploitation of these characteristics leads to a greater increase in lifespan of rats bearing brain tumors since the radiosensitizing effect of GBNs can be activated by X-ray microbeams when the gadolinium content is, at the same time, sufficiently high in the tumor and low in the surrounding healthy tissue. GBNs exhibit therefore an interesting potential for image-guided radiotherapy.

Multifunctional nanoparticles for multimodal imaging and theragnosis

Nanomedicine is the biomedical application of nanoscale materials for diagnosis and therapy of disease. Recent advances in nanotechnology and biotechnology have contributed to the development of multifunctional nanoparticles as representative nanomedicine. They were initially developed to enable the target-specific delivery of imaging or therapeutic agents for biomedical applications. Due to their unique features including multifunctionality, large surface area, structural diversity, and long circulation time in blood compared to small molecules, nanoparticles have emerged as attractive preferences for optimized therapy through personalized medicine. Multimodal imaging and theragnosis are the cutting-edge technologies where the advantages of nanoparticles are maximized. Because each imaging modality has its pros and cons, the integration of several imaging agents with different properties into multifunctional nanoparticles allows precise and fast diagnosis of disease through synergetic multimodal imaging. Moreover, nanoparticles are not only used for molecular imaging but also applied to deliver therapeutic agents to the disease site in order to accomplish the simultaneous imaging and therapy called theragnosis. This tutorial review will highlight the recent advances in the development of multifunctional nanoparticles and their biomedical applications to multimodal imaging and theragnosis as nanomedicine.

Folate receptor-targeted fluorescent paramagnetic bimodal liposomes for tumor imaging

RATIONALE AND OBJECTIVE

Receptor-targeted delivery of imaging and therapeutic agents can lead to enhanced efficacy for both. Multimodality imaging offers unique advantages over traditional single modality imaging. Tumor marker folate receptor (FR)-targeted fluorescent paramagnetic bimodal liposomes were synthesized to co-deliver paramagnetic and fluorescence agents for magnetic resonance (MR) and optical bimodal imaging contrast enhancement.

MATERIALS AND METHODS

Fluorescent and paramagnetic bimodal liposomes were synthesized with a mean diameter of 136 nm and a low polydispersity index. The liposomes incorporated folate-PEG(3350)-CHEMS for FR targeting, Gd(III)[N,N-Bis-stearylamidomethyl-N'-amidomethyl]diethylenetriamine tetraacetic acid (Gd-DTPA-BSA) for MR contrast, and calcein for fluorescence. To determine the specificity and efficiency of delivery, the liposomes were evaluated in FR-positive KB and HeLa cells and FR-negative A549 cells, which were analyzed by fluorescence microscopy, magnetic resonance imaging (MRI), and flow cytometry (FCM).

RESULTS

FR-specific and efficient cellular uptake of the FR-targeted bimodal liposomes was confirmed by fluorescence microscopy and by FCM. The mean fluorescence intensity (MFI) of KB cells treated with FR-targeted liposomes was 45× that of cells treated with nontargeted liposomes, and 18× that of cells treated with FR-targeted liposomes and excess folic acid (FA). The MFI of HeLa cells treated with targeted liposomes was 33× that of nontargeted liposomes, and was 16× that of the mixture of targeted liposomes and free FA. In contrast, the MFI of A549 cells treated with FR-targeted liposomes was nearly the same as those treated with nontargeted liposomes. The T(1)-weighted MR images of HeLa and KB cells incubated with FR-targeted liposomes had much higher signal intensity than those treated with nontargeted liposomes or free Gd-DTPA. Furthermore, the FR-targeting effect could be blocked by excess free FA.

CONCLUSION

FR-targeted fluorescent paramagnetic bimodal liposomes provided a novel platform for bimodal tumor imaging and theranostic delivery.

Cancer nanotheranostics: improving imaging and therapy by targeted delivery across biological barriers

Cancer nanotheranostics aims to combine imaging and therapy of cancer through use of nanotechnology. The ability to engineer nanomaterials to interact with cancer cells at the molecular level can significantly improve the effectiveness and specificity of therapy to cancers that are currently difficult to treat. In particular, metastatic cancers, drug-resistant cancers, and cancer stem cells impose the greatest therapeutic challenge for targeted therapy. Targeted therapy can be achieved with appropriately designed drug delivery vehicles such as nanoparticles, adult stem cells, or T cells in immunotherapy. In this article, we first review the different types of nanotheranostic particles and their use in imaging, followed by the biological barriers they must bypass to reach the target cancer cells, including the blood, liver, kidneys, spleen, and particularly the blood-brain barrier. We then review how nanotheranostics can be used to improve targeted delivery and treatment of cancer cells. Finally, we discuss development of nanoparticles to overcome current limitations in cancer therapy.