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Natural killer (NK)-cell-based immunotherapy is emerging as an attractive approach for cancer treatment. However, to facilitate and expedite clinical implementation, important questions must be answered regarding the in vivo functionality and trafficking patterns of the transferred cells. We have recently developed a noninvasive cell-tracking technique, based on gold nanoparticles (GNPs) as cell-labeling and contrast agents for whole-body computed tomography (CT) imaging. Herein, we report the implementation of this technique for longitudinal and quantitative tracking of NK cell kinetics, the migration and biodistribution in tumor-bearing mice. NK cells were successfully labeled with GNPs, without impairing their biological function, as assessed both in vitro, by cytokine release and cytotoxicity assays, and in vivo, using a xenograft model of human tumors. Using CT, we longitudinally tracked the migration of intravenously injected NK cells and observed an accumulation of effector cell clusters at the tumor site, up to 72 h. Fluorescence imaging of the cells over time correlated with ex vivo quantitative analysis of gold content in the tumor, validating the accuracy and reliability of our technique. Our cell-tracking approach thus offers a valuable tool for preclinical studies, as well as for clinical applications, to elucidate the fate of NK cells and promote the implementation of NK-cell-based immunotherapy.

Nanoplasmonic biosensors incorporating noble metal nanocavity arrays are widely used for the detection of various biomarkers. Gold nanorods (GNRs) have unique properties that can enhance spectroscopic detection capabilities of such nanocavity-based biosensors. However, the contribution of the physical properties of multiple GNRs to resonance enhancement of gold nanocavity arrays requires further characterization and elucidation. In this work, we study how GNR aspect ratio (AR) and surface area (SA) modify the plasmonic resonance spectrum of a gold triangular nanocavity array by both simulations and experiments. The finite integration technique (FIT) simulated the extinction spectrum of the gold nanocavity array with 300 nm periodicity onto which the GNRs of different ARs and SAs are placed. Simulations showed that matching of the GNRs longitudinal peak, which is affected by AR, to the nanocavity array's spectrum minima can optimize signal suppression and shifting. Moreover, increasing SA of the matched GNRs increased the spectral variations of the array. Experiments confirmed that GNRs conjugated to a gold triangular nanocavity array of 300 nm periodicity caused spectrum suppression and redshift. Our findings demonstrate that tailoring of the GNR AR and SA parameters to nanoplasmonic arrays has the potential to greatly improve spectral variations for enhanced plasmonic biosensing.

Genetically engineered T cells are a powerful new modality for cancer immunotherapy. However, their clinical application for solid tumors is challenging, and crucial knowledge on cell functionality in vivo is lacking. Here, we fabricated a nanoprobe composed of dendrimers incorporating a calcium sensor and gold nanoparticles, for dual-modal monitoring of engineered T cells within a solid tumor. T cells engineered to express a melanoma-specific T-cell receptor and loaded with the nanoprobe were longitudinally monitored within melanoma xenografts in mice. Fluorescent imaging of the nanoprobe's calcium sensor revealed increased intra-tumoral activation of the T cells over time, up to 24 h. Computed tomography imaging of the nanoprobe's gold nanoparticles revealed the cells' intra-tumoral distribution pattern. Quantitative analysis revealed the intra-tumoral T cell quantities. Thus, this nanoprobe reveals intra-tumoral persistence, penetration and functional status of genetically engineered T cells, which can advance T cell-based immunotherapy and promote next-generation live cell imaging.

Nanosystems for monitoring and tracking T cells provide an important basis for evaluating the functionality and efficacy of T cell-based immunotherapy. To this end, we designed herein an efficient nanoprobe for T cell monitoring and tracking using poly(amidoamine) (PAMAM) dendrimer-entrapped gold nanoparticles (Au DENPs) conjugated with Fluo-4 for dual-mode computed tomography (CT) and fluorescence imaging. In this study, PAMAM dendrimers of generation 5 (G5) were modified with hydroxyl-terminated polyethylene glycol (PEG) and then used to entrap 2.0 nm Au NPs followed by acetylation of the excess amine groups on the dendrimer surface. Subsequently, the calcium ion probe was covalently attached to the dendrimer nanohybrids through the PEG hydroxyl end groups to gain the functional {(Au0)25-G5.NHAc-(PEG)14-(Fluo-4)2} nanoprobe. This nanoprobe had excellent water solubility, high X-ray attenuation coefficient, and good cytocompatibility in the given concentration range, as well as a high T cell labeling efficiency. Confocal microscopy and flow cytometry results demonstrated that the nanoprobe was able to fluorescently sense activated T cells. Moreover, the nanoprobe was able to realize both CT and fluorescence imaging of subcutaneously injected T cells in vivo. Thus, the developed novel dendrimer-based nanosystem may hold great promise for advancing and improving the clinical application of T cell-based immunotherapy.

Acute kidney injury (AKI) is frequently associated with reactive oxygen species (ROS) and causes high mortality in clinics annually, and nanotechnology-mediated antioxidative therapy is emerging as a novel strategy for AKI treatment. Herein, four kinds of natural antioxidants are able to coordinate with iron (Fe) ions to form ultra-small coordination polymer nanodots (CPNs) with good water dispersibility and strong ROS scavenging ability. In particular, Fe-curcumin CPNs (Fe-Cur CPNs) are applied for cellular ROS scavenging and rhabdomyolysis-induced AKI relief.

Photodynamic therapy (PDT) is a promising recognized treatment for cancer. To date, PDT drugs are injected systemically, and the tumor area is irradiated to induce cell death. Current clinical protocols have several drawbacks, including limited accessibility to solid tumors and insufficient selectivity of drugs. Herein, we propose an alternative approach to improve PDT effectiveness by magnetic targeting of responsive carriers conjugated to the PDT drug. We coordinatively attached a

Individuals with spinal cord injury (SCI) usually suffer from permanent neurological deficits, while spontaneous recovery and therapeutic efficacy are limited. Here, we demonstrate that when given intranasally, exosomes derived from mesenchymal stem cells (MSC-Exo) could pass the blood brain barrier and migrate to the injured spinal cord area. Furthermore, MSC-Exo loaded with phosphatase and tensin homolog small interfering RNA (ExoPTEN) could attenuate the expression of PTEN in the injured spinal cord region following intranasal administrations. In addition, the loaded MSC-Exo considerably enhanced axonal growth and neovascularization, while reducing microgliosis and astrogliosis. The intranasal ExoPTEN therapy could also partly improve structural and electrophysiological function and, most importantly, significantly elicited functional recovery in rats with complete SCI. The results imply that intranasal ExoPTEN may be used clinically to promote recovery for SCI individuals.

Current medicine could greatly improve by intelligent treatment systems able to respond autonomously to early stages of diseases from within a patient. As an initial study en route to such a system...

Exosomes, nanovesicles that are secreted by different cell types, enable intercellular communication at local or distant sites. Alhough they have been found to cross the blood brain barrier, their migration and homing abilities within the brain remain unstudied. We have recently developed a method for longitudinal and quantitative in vivo neuroimaging of exosomes based on the superior visualization abilities of classical X-ray computed tomography (CT), combined with gold nanoparticles as labeling agents. Here, we used this technique to track the migration and homing patterns of intranasally administrated exosomes derived from bone marrow mesenchymal stem cells (MSC-exo) in different brain pathologies, including stroke, autism, Parkinson's disease, and Alzheimer's disease. We found that MSC-exo specifically targeted and accumulated in pathologically relevant murine models brains regions up to 96 h post administration, while in healthy controls they showed a diffuse migration pattern and clearance by 24 h. The neuro-inflammatory signal in pathological brains was highly correlated with MSC-exo accumulation, suggesting that the homing mechanism is inflammatory-driven. In addition, MSC-exo were selectively uptaken by neuronal cells, but not glial cells, in the pathological regions. Taken together, these findings can significantly promote the application of exosomes for therapy and targeted drug delivery in various brain pathologies.

Exosomes are promising vectors for anti-tumor therapy, due to their biocompatibility, low immunogenicity, and innate ability to interact with target cells. However, promoting clinical application of exosome-based therapeutics requires elucidation of key issues, including exosome biodistribution, tumor targeting and accumulation, and the ability to overcome tumor barriers that limit the penetration of various nano-carriers and drugs. Here, we examined these parameters in exosomes derived from mesenchymal stem cells (MSC-exo) and from the A431 squamous cell carcinoma line (A431-exo), which both have potential use in cancer therapy. Using our novel technique combining gold nanoparticle (GNP) labeling of exosomes and non-invasive computed tomography imaging (CT), we longitudinally and quantitatively tracked the two intravenously-injected exosome types in A431 tumor-bearing mice. CT imaging up to 48 h and subsequent ex vivo analysis revealed tumor homing abilities of both exosome types, yet there was significantly higher tumor accumulation of MSC-exo as compared to A431-exo. Moreover, MSC-exo demonstrated the ability to penetrate the tumor and distribute throughout its bulk, while non-encapsulated GNPs remained concentrated at the tumor periphery. Histological analysis showed penetration of MSC-exo not only into the tumor tissue, but also into tumor cell cytoplasm. While the proportion of biodistribution between organs at 48 h was similar for both exosome types, more rapid clearance was indicated for A431-exo. Thus, our findings demonstrate an effect of exosome type on tumor targeting abilities and biodistribution, and suggest that MSC-exo may have superior abilities for tumor-targeted therapy.

Fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) is a powerful tool for cancer detection, staging, and follow-up. However, 18F-FDG-PET imaging has high rates of false positives, as it cannot distinguish between tumor and inflammation regions that both feature increased glucose metabolic activity. In the present study, we engineered liposomes coated with glucose and the chelator dodecane tetraacetic acid (DOTA) complexed with copper, to serve as a diagnostic technology for differentiating between cancer and inflammation. This liposome technology is based on FDA-approved materials and enables complexation with metal cations and radionuclides. We found that these liposomes were preferentially uptaken by cancer cell lines with high metabolic activity, mediated via glucose transporter-1. In vivo, these liposomes were avidly uptaken by tumors, as compared to liposomes without glucose coating. Moreover, in a combined tumor-inflammation mouse model, these liposomes accumulated in the tumor tissue and not in the inflammation region. Thus, this technology shows high specificity for tumors while evading inflammation and has potential for rapid translation to the clinic and integration with existing PET imaging systems, for effective reduction of false positives in cancer diagnosis.

X-ray imaging is the most widely used diagnostic imaging method in modern medicine and several advanced forms of this technology have recently emerged. Iodinated molecules and barium sulfate suspensions are clinically approved X-ray contrast agents and are widely used. However, these existing contrast agents provide limited information, are suboptimal for new X-ray imaging techniques and are developing safety concerns. Thus, over the past 15 years, there has been a rapid growth in the development of nanoparticles as X-ray contrast agents. Nanoparticles have several desirable features such as high contrast payloads, the potential for long circulation times, and tunable physicochemical properties. Nanoparticles have also been used in a range of biomedical applications such as disease treatment, targeted imaging, and cell tracking. In this review, we discuss the principles behind X-ray contrast generation and introduce new types of X-ray imaging modalities, as well as potential elements and chemical compositions that are suitable for novel contrast agent development. We focus on the progress in nanoparticle X-ray contrast agents developed to be renally clearable, long circulating, theranostic, targeted, or for cell tracking. We feature agents that are used in conjunction with the newly developed multi-energy computed tomography and mammographic imaging technologies. Finally, we offer perspectives on current limitations and emerging research topics as well as expectations for the future development of the field. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Biological logic gates are smart probes able to respond to biological conditions in behaviors similar to computer logic gates, and they pose a promising challenge for modern medicine. Researchers are creating many kinds of smart nanostructures that can respond to various biological parameters such as pH, ion presence, and enzyme activity. Each of these conditions alone might be interesting in a biological sense, but their interactions are what define specific disease conditions. Researchers over the past few decades have developed a plethora of stimuli-responsive nanodevices, from activatable fluorescent probes to DNA origami nanomachines, many explicitly defining logic operations. Whereas many smart configurations have been explored, in this review we focus on logic operations actuated through fluorescent signals. We discuss the applicability of fluorescence as a means of logic gate implementation, and consider the use of both fluorescence intensity as well as fluorescence lifetime.

Exosomes, a subtype of extracellular vesicles, are nanovesicles of endocytic origin. Exosomes contain a plethora of proteins, lipids, and genetic materials of parent cells to facilitate intercellular communications. Tracking exosomes in vivo is fundamentally important to understand their biodistribution pattern and the mechanism of biological actions in experimental models. Until now, a number of tracking protocols have been developed, including fluorescence labeling, bioluminescence imaging, magnetic resonance imaging, and computed tomography (CT) tracking of exosomes. Recently, we have shown the tracking and quantification of exosomes in a spinal cord injury model, by using two tracking approaches. More specifically, following intranasal administration of gold nanoparticle-encapsulated exosomes to rats bearing complete spinal cord injury, exosomes in the whole central nervous system were tracked by using microCT, and quantified by using inductively coupled plasma and flame atomic absorption spectroscopy. In addition, optical imaging of fluorescently labeled exosomes was performed to understand the abundance of migrating exosomes in the spinal cord lesion, as compared to the healthy controls, and to further examine their affinity to different cell types in the lesion. Thus, the protocol presented here aids in the study of exosome biodistribution at both cellular and organ levels, in the context of spinal cord injury. This protocol will also enable researchers to better elucidate the fate of administered exosomes in other models of interest.

Bacterial infection and biofilm buildup is a major challenge for wound healing. In the present work we developed a method to track bacteria in vivo in order to analyze the progress of the healing. Regulated irrigation combined with negative pressure (RI-NPT) is a nonpharmaceutical therapeutic strategy for reducing bacterial load in acute and chronically infected wounds. Here, we analyzed RI-NPT hydrokinetics and efficacy of bacterial load reduction in wounds. Escherichia coli were loaded with gold nanoparticles, in order to make them "visible" and trackable using computed tomography (CT). Bacteria were tracked using CT in a low-flow rat wound model over time. CT tracking revealed that while regulated negative pressure-assisted wound therapy reduced bacterial load to a limited extent (5%), RI-NPT significantly increased bacterial outflow and clearance (by 45%). This nanotechnology-based approach demonstrates the ability to track bacteria in vivo at real time and also the ability of the RI-NPT technology to effectively reduce bacterial load.

Multimodal imaging, integrating different imaging modalities, is emerging as a promising strategy for improving both preclinical and clinical imaging. Computed tomography (CT) and magnetic resonance imaging (MRI) are among the widely clinically-used imaging techniques. These imaging modalities are used for disease diagnosis and screening, each providing different and complementary information about the patient and the disease state. Nanoparticles are considered promising contrast agents for in vivo imaging applications, providing improved imaging and targeting capabilities compared to the commonly used contrast compounds. In this project, we present the development of a novel hybrid nanostructure, comprising of iron oxide core and gold shell nanoparticle for dual model CT and MRI imaging. The hybrid structures presented herein have potential to serve as a unique platform for precision imaging.

Exosomes have many biological functions as short- and long distance nanocarriers for cell-to-cell communication. They allow the exchange of complex information between cells, and thereby modulate various processes such as homeostasis, immune response and angiogenesis, in both physiological and pathological conditions. In addition, due to their unique abilities of migration, targeting, and selective internalization into specific cells, they are promising delivery vectors. As such, they provide a potentially new field in diagnostics and treatment, and may serve as an alternative to cell-based therapeutic approaches. However, a major drawback for translating exosome treatment to the clinic is that current understanding of these endogenous vesicles is insufficient, especially in regards to their in vivo behavior. Tracking exosomes in vivo can provide important knowledge regarding their biodistribution, migration abilities, toxicity, biological role, communication capabilities, and mechanism of action. Therefore, the development of efficient, sensitive and biocompatible exosome labeling and imaging techniques is highly desired. Recent studies have developed different methods for exosome labeling and imaging, which have allowed for in vivo investigation of their bio-distribution, physiological functions, migration, and targeting mechanisms. These improved imaging capabilities are expected to greatly advance exosome-based nanomedicine applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

X-ray CT instruments are among the most available, efficient, and cost-effective imaging modalities in hospitals. The field of CT molecular imaging is emerging which relies mainly on the detection of gold nanoparticles and iodine-containing compounds directed to tagging a variety of abundant biomolecules. Here for the first time we attempted to detect enzymatic activity, while the low sensitivity of CT scanners to contrast reagents made this a challenging task. Therefore, we developed a new class of nanosized cathepsin-targeted activity-based probes (ABPs) for functional CT imaging of cancer. ABPs are small molecules designed to covalently modify enzyme targets in an activity-dependent manner. Using a CT instrument, these novel probes enable detection of the elevated cathepsin activity within cancerous tissue, thus creating a direct link between biological processes and imaging signals. We present the generation and biochemical evaluation of a library of ABPs tagged with different sized gold nanoparticles (GNPs), with various ratios of cathepsin-targeting moiety and a combination of different polyethylene glycol (PEG) protective layers. The most potent and stable GNP-ABPs were applied for noninvasive cancer imaging in mice. Surprisingly, detection of CT contrast from the tumor had reverse correlation to GNP size and the amount of targeting moiety. Interestingly, TEM images of tumor sections show intercellular lysosomal subcellular localization of the GNP-ABPs. In conclusion, we demonstrate that the covalent linkage is key for detection using low sensitive imaging modalities and the utility of GNP-ABPs as a promising tool for enzymatic-based CT imaging.

Duchenne muscular dystrophy (DMD) is a degenerative lethal, X-linked disease of skeletal and cardiac muscles caused by mutations in the dystrophin gene. Cell therapy using different cell types, including mesenchymal stromal cells (MSCs), has been considered as a potential approach for the treatment of DMD. MSCs can be obtained from autologous sources such as bone marrow and adipose tissues or from allogeneic placenta and umbilical cord. The safety and therapeutic impact of these cells has been demonstrated in pre-clinical and clinical studies and their functions are attributed to paracrine effects that are mediated by secreted cytokines and extracellular vesicles. Here, we studied the therapeutic effects of placenta-derived MSCs (PL-MSCs) and their secreted exosomes using mouse and human myoblasts from healthy controls, Duchenne patients and mdx mice. Treatment of myoblasts with conditioned medium or exosomes secreted by PL-MSCs increased the differentiation of these cells and decreased the expression of fibrogenic genes in DMD patient myoblasts. In addition, these treatments also increased the expression of utrophin in these cells. Using a quantitative miR-29c reporter, we demonstrated that the PL-MSC effects were partly mediated by the transfer of exosomal miR-29c. Intramuscular transplantation of PL-MSCs in mdx mice resulted in decreased creatine kinase levels. PL-MSCs significantly decreased the expression of TGF-β and the level of fibrosis in the diaphragm and cardiac muscles, inhibited inflammation and increased utrophin expression. In vivo imaging analyses using MSCs labeled with gold nanoparticles or fluorescent dyes demonstrated localization of the cells in the muscle tissues up to 3 weeks post treatment. Altogether, these results demonstrate that PL-MSCs and their secreted exosomes have important clinical applications in cell therapy of DMD partly via the targeted delivery of exosomal miR-29c.

Development of versatile nanoscale platforms for cancer diagnosis and therapy is of great importance for applications in translational medicine. In this work, we present the use of γ-polyglutamic acid (γ-PGA) nanogels (NGs) to load polypyrrole (PPy) for thermal/photoacoustic (PA) imaging and radiotherapy (RT)-sensitized tumor photothermal therapy (PTT). First, a double emulsion approach was used to prepare the cystamine dihydrochloride (Cys)-cross-linked γ-PGA NGs. Next, the cross-linked NGs served as a reactor to be filled with pyrrole monomers that were subjected to in situ oxidation polymerization in the existence of Fe(III) ions. The formed uniform PPy-loaded NGs having an average diameter of 38.9 ± 8.6 nm exhibited good water-dispersibility and colloid stability. The prominent near-infrared (NIR) absorbance feature due to the loaded PPy endowed the NGs with contrast enhancement in PA imaging. The hybrid NGs possessed excellent photothermal conversion efficiency (64.7%) and stability against laser irradiation, and could be adopted for PA imaging and PTT of cancerous cells and tumor xenografts. Importantly, we also explored the cooperative PTT and X-ray radiation-mediated RT for enhanced tumor therapy. We show that PTT of tumors can be more significantly sensitized by RT using the sequence of laser irradiation followed by X-ray radiation as compared to using the reverse sequence. Our study suggests a promising theranostic platform of hybrid NGs that may be potentially utilized for PA imaging and combination therapy of different types of tumors.

X-ray computed tomography (CT) is a robust, precise, fast, and reliable imaging method that enables excellent spatial resolution and quantification of contrast agents throughout the body. However, CT is largely inadequate for molecular imaging applications due mainly to its low contrast sensitivity that forces the use of large concentrations of contrast agents for detection. To overcome this limitation, we generated a new class of iodinated nanoscale activity-based probes (IN-ABPs) that sufficiently accumulates at the target site by covalently binding cysteine cathepsins that are exceptionally highly expressed in cancer. The IN-ABPs are comprised of a short targeting peptide selective to specific cathepsins, an electrophilic moiety that allows activity-dependent covalent binding, and tags containing dendrimers with up to 48 iodine atoms. IN-ABPs selectively bind and inhibit activity of recombinant and intracellular cathepsin B, L, and S. We compared the in vivo kinetics, biodistribution, and tumor accumulation of IN-ABPs bearing 18 and 48 iodine atoms each, and their control counterparts lacking the targeting moiety. Here we show that although both IN-ABPs bind specifically to cathepsins within the tumor and produce detectable CT contrast, the 48-iodine bearing IN-ABP was found to be optimal with signals over 2.1-fold higher than its nontargeted counterpart. In conclusion, this study shows the synthetic feasibility and potential utility of IN-ABPs as potent contrast agents that enable molecular imaging of tumors using CT.

Cancer immunotherapy has made enormous progress in offering safer and more effective treatments for the disease. Specifically, programmed death ligand 1 antibody (αPDL1), designed to perform immune checkpoint blockade (ICB), is now considered a pillar in cancer immunotherapy. However, due to the complexity and heterogeneity of tumors, as well as the diversity in patient response, ICB therapy only has a 30% success rate, at most; moreover, the efficacy of ICB can be evaluated only two months after start of treatment. Therefore, early identification of potential responders and nonresponders to therapy, using noninvasive means, is crucial for improving treatment decisions. Here, we report a straightforward approach for fast, image-guided prediction of therapeutic response to ICB. In a colon cancer mouse model, we demonstrate that the combination of computed tomography imaging and gold nanoparticles conjugated to αPDL1 allowed prediction of therapeutic response, as early as 48 h after treatment. This was achieved by noninvasive measurement of nanoparticle accumulation levels within the tumors. Moreover, we show that the nanoparticles efficiently prevented tumor growth with only a fifth of the standard dosage of clinical care. This technology may be developed into a powerful tool for early and noninvasive patient stratification as responders or nonresponders.

Aim: Our goal was to develop an efficient nanoparticle-based system that can overcome the restrictive mechanism of the blood–brain barrier (BBB) by targeting insulin receptors and would thus enable drug delivery to the brain. Methods: Insulin-coated gold nanoparticles (INS-GNPs) were synthesized to serve as a BBB transport system. The effect of nanoparticle size (20, 50 and 70 nm) on their ability to cross the BBB was quantitatively investigated in Balb/C mice. Results: The most widespread biodistribution and highest accumulation within the brain were observed using 20 nm INS-GNPs, 2 h post injection. In vivo CT imaging revealed that particles migrated to specific brain regions, which are involved in neurodegenerative and neuropsychiatric disorders. Conclusion: These findings promote the optimization of nanovehicles for transport of drugs through the BBB. The insulin coating of the particles enabled targeting of specific brain regions, suggesting the potential use of INS-GNPs for delivery of various treatments for brain-related disorders.

Efforts to develop novel cell-based therapies originated with the first bone marrow transplant on a leukemia patient in 1956. Preclinical and clinical examples of cell-based treatment strategies have shown promising results across many disciplines in medicine, with recent advances in immune cell therapies for cancer producing remarkable response rates, even in patients with multiple treatment failures. However, cell-based therapies suffer from inconsistent outcomes, motivating the search for tools that allow monitoring of cell delivery and behavior in vivo. Noninvasive cell imaging techniques, also known as cell tracking, have been developed to address this issue. These tools can allow real-time, quantitative, and long-term monitoring of transplanted cells in the recipient, providing insight on cell migration, distribution, viability, differentiation, and fate, all of which play crucial roles in treatment efficacy. Understanding these parameters allows the optimization of cell choice, delivery route, and dosage for therapy and advances cell-based therapy for specific clinical uses. To date, most cell tracking work has centered on imaging modalities such as MRI, radionuclide imaging, and optical imaging. However, X-ray computed tomography (CT) is an emerging method for cell tracking that has several strengths such as high spatial and temporal resolution, and excellent quantitative capabilities. The advantages of CT for cell tracking are enhanced by its wide availability and cost effectiveness, allowing CT to become one of the most popular clinical imaging modalities and a key asset in disease diagnosis. In this review, we will discuss recent advances in cell tracking methods using X-ray CT in various applications, in addition to predictions on how the field will progress.

Contradictory results in clinical trials are preventing the advancement and implementation of cell-based therapy. To explain such results, there is a need to uncover the mystery regarding the fate of the transplanted cells. To answer this need, we developed a technique for noninvasive in vivo cell tracking, which uses gold nanoparticles as contrast agents for CT imaging. Herein, we investigate the design principles of this technique for intramuscular transplantation of therapeutic cells. Longitudinal studies were performed, displaying the ability to track cells over long periods of time. As few as 500 cells could be detected and a way to quantify the number of cells visualized by CT was demonstrated. Moreover, monitoring of cell functionality was demonstrated on a mouse model of Duchenne muscular dystrophy. This cell-tracking technology has the potential to become an essential tool in pre-clinical as well as clinical trials and to advance the future of cell therapy.

Recent studies have proposed that abnormal glutamatergic neurotransmission and glial pathology play an important role in the etiology and manifestation of depression. It was postulated that restoration of normal glutamatergic transmission, by enhancing glutamate uptake, may have a beneficial effect on depression. We examined this hypothesis using unique human glial-like mesenchymal stem cells (MSCs), which in addition to inherent properties of migration to regions of injury and secretion of neurotrophic factors, were differentiated to express high levels of functional glutamate transporters (excitatory amino acid transporters; EAAT). Additionally, gold nanoparticles (GNPs), which serve as contrast agents for CT imaging, were loaded into the cells for non-invasive, real-time imaging and tracking of MSC migration and final location within the brain. MSC-EAAT (2×105; 10 μl) were administered (i.c.v.) to Flinder Sensitive Line rats (FSLs), a genetic model for depression, and longitudinal behavioral and molecular changes were monitored. FSL rats treated with MSC-EAAT showed attenuated depressive-like behaviors (measured by the forced swim test, novelty exploration test and sucrose self-administration paradigm), as compared to controls. CT imaging, Flame Atomic Absorption Spectroscopy analysis and immunohistochemistry showed that the majority of MSCs homed specifically to the dentate gyrus of the hippocampus, a region showing structural brain changes in depression, including loss of glial cells. mRNA and protein levels of EAAT1 and BDNF were significantly elevated in the hippocampus of MSC-EAAT-treated FSLs. Our findings indicate that MSC-EAATs effectively improve depressive-like manifestations, possibly in part by increasing both glutamate uptake and neurotropic factor secretion in the hippocampus.

Designing personalized cancer nanomedicines is a challenging process. The emerging field of nanoinformatics can facilitate this process by enabling computational design of nanocarrier-encapsulated drugs. Recent data show that quantitative structure–nanoparticle assembly calculations predict particle formation and size, and can lead to safer and more effective personalized cancer therapeutics.

Aim: Longitudinal tracking of transplanted cells in clinical and experimental setups is crucial for evaluating the efficiency of retinal cell replacement therapies. Materials & methods: Gold nanoparticle-labeled photoreceptor precursors were transplanted in the vitreous and subretinal space of rats and were longitudinally tracked for over a month using optical coherence tomography, computed tomography and fluorescence fundus imaging. Results: This multimodal imaging approach enabled high-resolution long-term tracking and estimation of cell survival in the retina and vitreous, while displaying no toxic effects on the cells or the retina. Conclusion: These observations highlight the applicability of using gold nanoparticle for retinal cell tracking in existing experimental settings and its translational potential for providing more efficient retinal cell therapy in humans.

Immune checkpoint blockade (ICB) has shown unprecedented clinical success in treatment of cancer. However, not all patients show adequate response, and the treatment can lead to a broad range of adverse effects. Therefore, early identification of potential responders to therapy, using non-invasive means, is a critical challenge for improving ICB. Herein, we engineered anti-Programmed Death Ligand 1 (aPDL1) nanoparticles with enhanced ICB immunotherapy efficacy. Using a mouse model for colon cancer, we show that the nanoparticles accumulated, penetrated and efficiently prevented tumor growth. Moreover, we found a direct correlation between the amount of nanoparticle accumulation within the tumor at 48 hours, as determined by CT, and the therapeutic response. This enabled subject stratification as potential responders or non-responders, at an early time point. Thus, by integrating prognostic and ICB-based therapeutic functions into one nanoparticle, we obtained a straightforward approach for potential imageguided stratification of cancer patient subpopulations.

Nanomaterials functionalized with glucose have shown a great potential in cancer diagnosis and treatment. We have recently demonstrated that gold nanoparticles (GNP), functionalized with glucose, can be used for specific and sensitive tumor detection when combined with computed tomography (CT) - GNP functionalized with glucose in the second carbon position were used as a metabolically targeted contrast agents, and were able to discriminate between cancer and inflammation, which is a superior ability when comparing the FDG-PET which is not tumor specific. Here we aim to understand the uptake mechanisms of the glucose functionalized GNP using a comprehensive in vitro study in several cell types with different metabolic features, and examining the glucose transporter-1 (GLUT1) involvement in the uptake process. We found that the glucose functionalized GNP are not toxic to the cells in the tested concentrations and we demonstrate that the cellular uptake of GNP, when functionalized with glucose in the second carbon position, strongly depends on GLUT1 expression in the cells, which triggers clathrin-mediated endocytosis of the nanoparticles. This study can promote control and development of glucose-functionalized nanoparticles for many biological applications.

A major challenge for treatment of neurodegenerative disorders is the need to overcome the restrictive mechanism of the blood-brain-barrier (BBB) for delivery of therapeutic agents into the brain. Our goal was to develop an efficient nanoparticle-based system with the ability to bypass the BBB by targeting insulin receptors. We demonstrate that insulincoated gold-nanoparticles (INS-GNPs) can serve as an effective endogenous BBB transport system for delivering therapeutics into the brain. We further conducted a quantitative in-vivo investigation of the effect of nanoparticle size (20, 50 and 70nm) on the ability of INS-GNPs to cross the BBB. The most widespread bio-distribution and highest accumulation within the brain (5% of the injected dose) was observed using 20nm INS-GNPs, two hours post-injection. In-vivo CT imaging revealed that particles migrated to specific brain regions, rich in insulin receptors, which are important targets for the treatment of various neurodegenerative disorders. The findings described herein suggest the potential beneficial use of INS-GNPs as nano-vehicles for the transport of drugs through the BBB.

Sonodynamic therapy (SDT) triggered by ultrasound (US) has attracted increasing attention owing to its abilities to overcome critical limitations including low tissue-penetration depth and phototoxicity in photodynamic therapy. Herein, the design of a new type of sonosensitizer is revealed, namely, ultrasmall oxygen-deficient bimetallic oxide MnWO

Recently, nanoparticles have emerged as promising contrast agents for various imaging applications. In this paper, we present the synthesis and characterization of a novel hybrid nano-structure, consisting of an iron oxide@gold nanoparticle, labeled with technetium-99m, for trimodal SPECT/CT/MRI imaging. The particles showed efficient capabilities as CT/MRI imaging agent and high radiochemical yield, indicating a potential single hybrid material for multimodal SPECT/CT/MRI.

One of the main limitations of the highly used cancer imaging technique, PET-CT, is its inability to distinguish between cancerous lesions and post treatment inflammatory conditions. The reason for this lack of specificity is that [(18)F]FDG-PET is based on increased glucose metabolic activity, which characterizes both cancerous tissues and inflammatory cells. To overcome this limitation, we developed a nanoparticle-based approach, utilizing glucose-functionalized gold nanoparticles (GF-GNPs) as a metabolically targeted CT contrast agent. Our approach demonstrates specific tumor targeting and has successfully distinguished between cancer and inflammatory processes in a combined tumor-inflammation mouse model, due to dissimilarities in angiogenesis occurring under different pathologic conditions. This study provides a set of capabilities in cancer detection, staging and follow-up, and can be applicable to a wide range of cancers that exhibit high metabolic activity.

A major problem in the treatment of head and neck cancer today is the resistance of tumors to traditional radiation therapy, which results in 40% local failure, despite aggressive treatment. The main objective of this study was to develop a technique which will overcome tumor radioresistance by increasing the radiation absorbed in the tumor using cetuximab targeted gold nanoparticles (GNPs), in clinically relevant energies and radiation dosage. In addition, we have investigated the biological mechanisms underlying tumor shrinkage and the in vivo toxicity of GNP. The results showed that targeted GNP enhanced the radiation effect and had a significant impact on tumor growth (P < 0.001). The mechanism of radiation enhancement was found to be related to earlier and greater apoptosis (TUNEL assay), angiogenesis inhibition (by CD34 level) and diminished repair mechanism (PCNA staining). Additionally, GNPs have been proven to be safe as no evidence of toxicity has been observed.