Contrast-enhanced X-ray detection of breast microcalcifications in a murine model using targeted gold nanoparticles

Au/Mn nanodot platform for in vivo CT/MRI/FI multimodal bioimaging and photothermal therapy against tongue cancer

Surgical resection is the main method for oral tongue squamous cell carcinoma (OTSCC) treatment. However, the oral physiological function and aesthetics may be seriously damaged during the operation with a high risk of recurrence. Therefore, it is important to develop an alternative strategy with precise guidance for OTSCC treatment. Herein, multifunctional Au/Mn nanodots (NDs) are designed and synthesized. They can perform multimodal bioimaging, including computed tomography (CT) and magnetic resonance imaging (MRI) simultaneously, and exhibit bright near-infrared fluorescence imaging (FI) for navigation, and even integrate photothermal therapy (PTT) property. The localization of OTSCC relies on visual and tactile cues of surgeons while lacking noninvasive pretreament labeling and guidance. Au/Mn NDs provide CT/MRI imaging, giving two means of accurate positioning pretherapy. Meanwhile, the fluorescence of the Au/Mn NDs in the near-infrared region (NIR) is beneficial for noninvasive labeling and intuitive observation with the naked eye to determine the tumor boundary during PTT. Further, Au/Mn NDs showed excellent results in ablating tumors in vivo. Above all, the Au/Mn NDs provide a key platform for multimodal bioimaging and PTT in a single nanoagent, which demonstrated attractive performance for OTSCC treatment.

Engineering gold nanoparticles for molecular diagnostics and biosensing

Advances in nanotechnology and medical science have spurred the development of engineered nanomaterials and nanoparticles with particular focus on their applications in biomedicine. In particular, gold nanoparticles (AuNPs) have been the focus of great interest, due to their exquisite intrinsic properties, such as ease of synthesis and surface functionalization, tunable size and shape, lack of acute toxicity and favorable optical, electronic, and physicochemical features, which possess great value for application in biodetection and diagnostics purposes, including molecular sensing, photoimaging, and application under the form of portable and simple biosensors (e.g., lateral flow immunoassays that have been extensively exploited during the current COVID-19 pandemic). We shall discuss the main properties of AuNPs, their synthesis and conjugation to biorecognition moieties, and the current trends in sensing and detection in biomedicine and diagnostics. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > In Vitro Nanoparticle-Based Sensing Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

In Vivo Micro-Computerized Tomography Tracking of Human Periodontal Ligament Stem Cells Labeled with Gold Nanocomplexes

Gold nanocomplexes have been proposed as contrast agents for computerized tomography (CT) and cell tracking, which is especially useful in stem cell therapy. However, their potential for long-term in vivo cell detection is still unknown. This study proposes an optimized approach to labeling human periodontal ligament stem cells (hPDLSCs) with gold nanocomplexes to evaluate their detection with micro-CT after transplantation at four different rat tissues. The gold nanocomplexes of 0.05 mg mL^-1 do not affect cell viability nor osteogenic differentiation capacity, but render fluorescent and radiopaque hPDLSCs. Excellent linear correlation with the number of labeled cells is shown over a wide range (r = 0.99, P < 0.01), with a detection limit of ≈1.2 × 10³ cells/µL. In vivo, strong, and durable detection of transplanted labeled cells within 5 days at all investigated areas is seen by micro-CT and immunohistochemical assay. This approach confirms the potential of gold nanocomplexes in longitudinal in vivo cell tracking, which may facilitate their application in CT image-guided interventions commonly used in oromaxillofacial or systemic applications of stem cell therapy.

A data-driven maximum likelihood classification for nanoparticle agent identification in photon-counting CT

The nanoparticle agent, combined with a targeting factor reacting with lesions, enables specific CT imaging. Thus, the identification of the nanoparticle agents has the potential to improve clinical diagnosis. Thanks to the energy sensitivity of the photon-counting detector (PCD), it can exploit the K-edge of the nanoparticle agents in the clinical x-ray energy range to identify the agents. In this paper, we propose a novel data-driven approach for nanoparticle agent identification using the PCD. We generate two sets of training data consisting of PCD measurements from calibration phantoms, one in the presence of nanoparticle agent and the other in the absence of the agent. For a given sinogram of PCD counts, the proposed method calculates the normalized log-likelihood sinogram for each class (class 1: with the agent, class 2: without the agent) using theKnearest neighbors (KNN) estimator, backproject the sinograms, and compare the backprojection images to identify the agent. We also proved that the proposed algorithm is equivalent to the maximum likelihood-based classification. We studied the robustness of dose reduction with gold nanoparticles as the K-edge contrast media and demonstrated that the proposed method identifies targets with different concentrations of the agents without background noise.

Manganese-doped gold core mesoporous silica particles as a nanoplatform for dual-modality imaging and chemo-chemodynamic combination osteosarcoma therapy

In this study, an effective and facile strategy is reported to construct a multifunctional nanoplatform by in situ doping metal manganese on gold core mesoporous silica nanoparticles (Au@MMSN). After further modification of alendronate (Ald) on Au@MMSN, the obtained Au@MMSN-Ald efficiently integrates bone targeted chemo-chemodynamic combination therapy and dual-modality computed tomography/magnetic resonance (CT/MR) imaging into a single platform. In particular, Au@MMSN-Ald exhibits excellent tumor microenvironment responsive drug release efficiency. The doxorubicin hydrochloride (DOX) loaded Au@MMSN-Ald (DOX@Au@MMSN-Ald) is demonstrated with excellent targeted ability toward osteosarcoma. Accordingly, in a specific tumor microenvironment, DOX@Au@MMSN-Ald also displays outstanding combined efficiency for killing cancer cells in vitro and suppressing the osteosarcoma growth in vivo. Benefiting from the Au nanoparticles confined in the core and manganese ions released from the shell, CT and MR dual-modality imaging were performed to verify the effective accumulation of Au@MMSN-Ald at the tumor site. Overall, the constructed DOX@Au@MMSN-Ald nanoparticles integrated imaging guide, responsive drug release and combination therapy, which may provide some insight for further biomedical applications in efficient osteosarcoma therapy.

Multi-energy computed tomography and material quantification: Current barriers and opportunities for advancement

Computed tomography (CT) technology has rapidly evolved since its introduction in the 1970s. It is a highly important diagnostic tool for clinicians as demonstrated by the significant increase in utilization over several decades. However, much of the effort to develop and advance CT applications has been focused on improving visual sensitivity and reducing radiation dose. In comparison to these areas, improvements in quantitative CT have lagged behind. While this could be a consequence of the technological limitations of conventional CT, advanced dual-energy CT (DECT) and photon-counting detector CT (PCD-CT) offer new opportunities for quantitation. Routine use of DECT is becoming more widely available and PCD-CT is rapidly developing. This review covers efforts to address an unmet need for improved quantitative imaging to better characterize disease, identify biomarkers, and evaluate therapeutic response, with an emphasis on multi-energy CT applications. The review will primarily discuss applications that have utilized quantitative metrics using both conventional and DECT, such as bone mineral density measurement, evaluation of renal lesions, and diagnosis of fatty liver disease. Other topics that will be discussed include efforts to improve quantitative CT volumetry and radiomics. Finally, we will address the use of quantitative CT to enhance image-guided techniques for surgery, radiotherapy and interventions and provide unique opportunities for development of new contrast agents.

Detectability of fluorescent gold nanoparticles under micro-CT and optical projection tomography imaging

Purpose: Preclinical studies often compare micro-computed tomography (micro-CT) imaging with histology using optical microscopy of fluorescently labeled slides. However, correlating the images is difficult because the tissues appear differently in the two modalities. It would be valuable to have a single contrast medium visible on both radiographic and optical imaging. Approach: We have explored the detectability of fluorescently labeled gold nanoparticles under micro-CT and optical projection tomography (OPT) in agarose phantoms and a murine melanoma tumor model. Murine melanoma cells were used to induce tumor growth in the right hind legs of 12 C57Bl6 mice, with the maximal tumor size of 1    cm 3 . We injected Cy3 fluorescently coated gold nanorods directly into the tumors. The mice were scanned with in vivo micro-CT (for pre- and post-contrast scans). Once euthanized, the hind leg was dissected and scanned with a higher resolution specimen micro-CT and OPT. Results: The distribution of the gold nanoparticles appeared to be contained and isolated to the tumor. Alignment of micro-CT specimen scans with the OPT scans was possible, although there was also autofluorescence of the surrounding muscle tissue. Conclusions: This study highlights the potential use of fluorescently labeled gold nanoparticles for imaging murine melanoma tumors using micro-CT and OPT.

Stem cell-mediated delivery of nanogels loaded with ultrasmall iron oxide nanoparticles for enhanced tumor MR imaging

The development of new nanoplatforms with enhanced tumor accumulation for accurate diagnosis still remains a great challenge in current precision nanomedicine. Herein, we report the design of stem cell-mediated delivery of nanogels (NGs) loaded with ultrasmall iron oxide (Fe3O4) nanoparticles (NPs) for enhanced magnetic resonance (MR) imaging of tumors. In this study, sodium citrate-stabilized ultrasmall Fe3O4 NPs with a size of 3.16 ± 1.30 nm were first synthesized using a solvothermal route, coated with polyethyleneimine (PEI), and used as crosslinkers to crosslink alginate (AG) NGs formed via a double emulsion approach, where the AG carboxyl groups were pre-activated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. The thus prepared Fe3O4 NP-loaded NGs (AG/PEI-Fe3O4 NGs) with a size of 47.68 ± 3.41 nm are water-dispersible, colloidally stable, cytocompatible in a given concentration range, display a relatively high r1 relaxivity (r1 = 1.5 mM-1 s-1), and are able to be taken up by bone mesenchymal stem cells without compromising cell viability and stem cell characteristics. Due to the tumor-chemotaxis or tumor tropism, the BMSCs are able to mediate the enhanced delivery of AG/PEI-Fe3O4 NGs to the tumor site after intravenous injection, thus enabling significantly strengthened MR imaging of tumors when compared to free NGs. These findings suggest that the developed AG/PEI-Fe3O4NGs, once mediated by stem cells may serve as a novel, safe, effective and targeted platform for enhanced MR imaging of tumors.

Quantification of multiple mixed contrast and tissue compositions using photon-counting spectral computed tomography

Quantitative material decomposition of multiple mixed, or spatially coincident, contrast agent (gadolinium and iodine) and tissue (calcium and water) compositions is demonstrated using photon-counting spectral computed tomography (CT). Material decomposition is performed using constrained maximum likelihood estimation (MLE) in the image domain. MLE is calibrated by multiple linear regression of all pure material compositions, which exhibits a strong correlation ( R 2 > 0.91 ) between the measured x-ray attenuation in each photon energy bin and known concentrations in the calibration phantom. Material decomposition of mixed compositions in the sample phantom provides color material concentration maps that clearly identify and differentiate each material. The measured area under the receiver operating characteristic curve is > 0.95 , indicating highly accurate material identification. Material decomposition also provides accurate quantitative estimates of material concentrations in mixed compositions with a root-mean-squared error < 12 % of the maximum concentration for each material. Thus, photon-counting spectral CT enables quantitative molecular imaging of multiple spatially coincident contrast agent (gadolinium and iodine) and tissue (calcium and water) compositions, which is not possible with current clinical molecular imaging modalities, such as nuclear imaging and magnetic resonance imaging.

Effects of bisphosphonate ligands and PEGylation on targeted delivery of gold nanoparticles for contrast-enhanced radiographic detection of breast microcalcifications

A preclinical murine model of hydroxyapatite (HA) breast microcalcifications (µcals), which are an important clinical biomarker for breast cancer detection, was used to investigate the independent effects of high affinity bisphosphonate (BP) ligands and a polyethylene glycol (PEG) spacer on targeted delivery of gold nanoparticles (Au NPs) for contrast-enhanced radiographic detection. The addition of BP ligands to PEGylated Au NPs (BP-PEG-Au NPs) resulted in five-fold greater binding affinity for targeting HA µcals, as expected, due to the strong binding affinity of BP ligands for calcium. Therefore, BP-PEG-Au NPs were able to target HA µcals in vivo after intramammary delivery, which enabled contrast-enhanced radiographic detection of µcals in both normal and radiographically dense mammary tissues similar to previous results for BP-Au NPs, while PEG-Au NPs did not. The addition of a PEG spacer between the BP targeting ligand and Au NP surface enabled improved in vivo clearance. PEG-Au NPs and BP-PEG-Au NPs were cleared from all mammary glands (MGs) and control MGs, respectively, within 24-48 h after intramammary delivery, while BP-Au NPs were not. PEGylated Au NPs were slowly cleared from MGs by lymphatic drainage and accumulated in the spleen. Histopathology revealed uptake of PEG-Au NPs and BP-PEG-Au NPs by macrophages in the spleen, liver, and MGs; there was no evidence of toxicity due to the accumulation of NPs in organs and tissues compared with untreated controls for up to 28 days after delivery. STATEMENT OF SIGNIFICANCE: Au NP imaging probes and therapeutics are commonly surface functionalized with PEG and/or high affinity targeting ligands for delivery. However, direct comparisons of PEGylated Au NPs with and without a targeting ligand, or ligand-targeted Au NPs with and without a PEG spacer, on in vivo targeting efficiency, biodistribution, and clearance are limited. Therefore, the results of this study are important for the rationale design of targeted NP imaging probes and therapeutics, including the translation of BP-PEG-Au NPs which enable improved sensitivity and specificity for the radiographic detection of abnormalities (e.g., µcals) in women with dense breast tissue.

An update on nanoparticle-based contrast agents in medical imaging

Despite the great value of current exogenous contrast agents for providing main diagnostic information, they still have certain drawbacks such as short blood half life, nonspecific biodistribution, fast clearance, slight renal toxicity and poor contrast in fat patients. Nanoparticles (NPs) are used as novel contrast agents that represent a promising strategy for the non invasive diagnosis. As a platform, nanoparticulates are compatible for developing targeted contrast agents. Advances in nanotechnology will provide enhanced sensitivity and specificity for tumor imaging enabling earlier detection of metastases. This article focuses on fundamental issue such as biological interactions, clearance routes, coating of NPs and presents a wide discussion about most recent category of NPs that are used as contrast agents and thebenefits/concerns issues associated with their use in clinical procedures.

Nanoparticle Functionalization and Its Potentials for Molecular Imaging

Functionalization enhances the properties and characteristics of nanoparticles through surface modification, and enables them to play a major role in the field of medicine. In molecular imaging, quality functional images are required with proper differentiation which can be seen with high contrast to obtain viable information. This review article discusses how functionalization enhances molecular imaging and enables multimodal imaging by which images with combination of functions particular to each modality can be obtained. This also explains how nanoparticles interacting at molecular level, when functionalized with molecules can target the cells of interest or substances with high specificity, reducing background signal and allowing simultaneous therapies to be carried out while imaging. Functionalization allows imaging for a prolonged period and enables to track the cells over a period of time. Recent researches and progress in functionalizing the nanoparticles to specifically enhance bioimaging with different modalities and their applications are reviewed in this article.

PB@Au Core-Satellite Multifunctional Nanotheranostics for Magnetic Resonance and Computed Tomography Imaging in Vivo and Synergetic Photothermal and Radiosensitive Therapy

To integrate multiple diagnostic and therapeutic strategies on a single particle through simple and effective methods is still challenging for nanotheranostics. Herein, we develop multifunctional nanotheranostic PB@Au core-satellite nanoparticles (CSNPs) based on Prussian blue nanoparticles (PBNPs) and gold nanoparticles (AuNPs), which are two kinds of intrinsic theranostic nanomaterials, for magnetic resonance (MR)-computed tomography (CT) imaging and synergistic photothermal and radiosensitive therapy (PTT-RT). PBNPs as cores enable T₁- and T₂-weighted MR contrast and strong photothermal effect, while AuNPs as satellites offer CT enhancement and radiosensitization. As revealed by both MR and CT imaging, CSNPs realized efficient tumor localization by passively targeted accumulation after intravenous injection. In vivo studies showed that CSNPs resulted in synergistic PTT-RT action to achieve almost entirely suppression of tumor growth without observable recurrence. Moreover, no obvious systemic toxicity of mice confirmed good biocompatibility of CSNPs. These results raise new possibilities for clinical nanotheranostics with multimodal diagnostic and therapeutic coalescent design.

A Functional CT Contrast Agent for In Vivo Imaging of Tumor Hypoxia

Hypoxia, which has been well established as a key feature of the tumor microenvironment, significantly influences tumor behavior and treatment response. Therefore, imaging for tumor hypoxia in vivo is warranted. Although some imaging modalities for detecting tumor hypoxia have been developed, such as magnetic resonance imaging, positron emission tomography, and optical imaging, these technologies still have their own specific limitations. As computed tomography (CT) is one of the most useful imaging tools in terms of availability, efficiency, and convenience, the feasibility of using a hypoxia-sensitive nanoprobe (Au@BSA-NHA) for CT imaging of tumor hypoxia is investigated, with emphasis on identifying different levels of hypoxia in two xenografts. The nanoprobe is composed of Au nanoparticles and nitroimidazole moiety which can be electively reduced by nitroreductase under hypoxic condition. In vitro, Au@BSA-NHA attain the higher cellular uptake under hypoxic condition. Attractively, after in vivo administration, Au@BSA-NHA can not only monitor the tumor hypoxic environment with CT enhancement but also detect the hypoxic status by the degree of enhancement in two xenograft tumors with different hypoxic levels. The results demonstrate that Au@BSA-NHA may potentially be used as a sensitive CT imaging agent for detecting tumor hypoxia.

Improved sensitivity of computed tomography towards iodine and gold nanoparticle contrast agents via iterative reconstruction methods

Computed tomography is a widely used medical imaging technique that has high spatial and temporal resolution. Its weakness is its low sensitivity towards contrast media. Iterative reconstruction techniques (ITER) have recently become available, which provide reduced image noise compared with traditional filtered back-projection methods (FBP), which may allow the sensitivity of CT to be improved, however this effect has not been studied in detail. We scanned phantoms containing either an iodine contrast agent or gold nanoparticles. We used a range of tube voltages and currents. We performed reconstruction with FBP, ITER and a novel, iterative, modal-based reconstruction (IMR) algorithm. We found that noise decreased in an algorithm dependent manner (FBP > ITER > IMR) for every scan and that no differences were observed in attenuation rates of the agents. The contrast to noise ratio (CNR) of iodine was highest at 80 kV, whilst the CNR for gold was highest at 140 kV. The CNR of IMR images was almost tenfold higher than that of FBP images. Similar trends were found in dual energy images formed using these algorithms. In conclusion, IMR-based reconstruction techniques will allow contrast agents to be detected with greater sensitivity, and may allow lower contrast agent doses to be used.

Targeted delivery to bone and mineral deposits using bisphosphonate ligands

The high concentration of mineral present in bone and pathological calcifications is unique compared with all other tissues and thus provides opportunity for targeted delivery of pharmaceutical drugs, including radiosensitizers and imaging probes. Targeted delivery enables accumulation of a high local dose of a therapeutic or imaging contrast agent to diseased bone or pathological calcifications. Bisphosphonates (BPs) are the most widely utilized bone-targeting ligand due to exhibiting high binding affinity to hydroxyapatite mineral. BPs can be conjugated to an agent that would otherwise have little or no affinity for the sites of interest. This article summarizes the current state of knowledge and practice for the use of BPs as ligands for targeted delivery to bone and mineral deposits. The clinical history of BPs is briefly summarized to emphasize the success of these molecules as therapeutics for metabolic bone diseases. Mechanisms of binding and the relative binding affinity of various BPs to bone mineral are introduced, including common methods for measuring binding affinity in vitro and in vivo. Current research is highlighted for the use of BP ligands for targeted delivery of BP conjugates in various applications, including (1) therapeutic drug delivery for metabolic bone diseases, bone cancer, other bone diseases, and engineered drug delivery platforms; (2) imaging probes for scintigraphy, fluorescence, positron emission tomography, magnetic resonance imaging, and computed tomography; and (3) radiotherapy. Last, and perhaps most importantly, key structure-function relationships are considered for the design of drugs with BP ligands, including the tether length between the BP and drug, the size of the drug, the number of BP ligands per drug, cleavable tethers between the BP and drug, and conjugation schemes.

Laser-synthesized ligand-free Au nanoparticles for contrast agent applications in computed tomography and magnetic resonance imaging

Pulsed laser ablation in liquids (PLAL) has emerged as a new green chemistry method, advantageous to produce gold nanoparticles-based contrast agents with strong blood retention and for multimodal imaging.

Gold nanoparticles as contrast agents in x-ray imaging and computed tomography

Computed tomography enables 3D anatomic imaging at a high spatial resolution, but requires delivery of an x-ray contrast agent to distinguish tissues with similar or low x-ray attenuation. Gold nanoparticles (AuNPs) have gained recent attention as an x-ray contrast agent due to exhibiting a high x-ray attenuation, nontoxicity and facile synthesis and surface functionalization for colloidal stability and targeted delivery. Potential diagnostic applications include blood pool imaging, passive targeting and active targeting, where actively targeted AuNPs could enable molecular imaging by computed tomography. This article summarizes the current state of knowledge for AuNP x-ray contrast agents within a paradigm of key structure-property-function relationships in order to provide guidance for the design of AuNP contrast agents to meet the necessary functional requirements in a particular application. Functional requirements include delivery to the site of interest (e.g., blood, tumors or microcalcifications), nontoxicity during delivery and clearance, targeting or localization at the site of interest and contrast enhancement for the site of interest compared with surrounding tissues. Design is achieved by strategically controlling structural characteristics (composition, mass concentration, size, shape and surface functionalization) for optimized properties and functional performance. Examples from the literature are used to highlight current design trade-offs that exist between the different functional requirements.

Contrast-Enhanced X-ray Detection of Microcalcifications in Radiographically Dense Mammary Tissue Using Targeted Gold Nanoparticles

Breast density reduces the accuracy of mammography, motivating methods to improve sensitivity and specificity for detecting abnormalities within dense breast tissue, but preclinical animal models are lacking. Therefore, the objectives of this study were to investigate a murine model of radiographically dense mammary tissue and contrast-enhanced X-ray detection of microcalcifications in dense mammary tissue by targeted delivery of bisphosphonate-functionalized gold nanoparticles (BP-Au NPs). Mammary glands (MGs) in the mouse mammary tumor virus - polyomavirus middle T antigen (MMTV-PyMT or PyMT) model exhibited greater radiographic density with age and compared with strain- and age-matched wild-type (WT) controls at 6-10 weeks of age. The greater radiographic density of MGs in PyMT mice obscured radiographic detection of microcalcifications that were otherwise detectable in MGs of WT mice. However, BP-Au NPs provided enhanced contrast for the detection of microcalcifications in both radiographically dense (PyMT) and WT mammary tissues as measured by computed tomography after intramammary delivery. BP-Au NPs targeted microcalcifications to enhance X-ray contrast with surrounding mammary tissue, which resulted in improved sensitivity and specificity for detection in radiographically dense mammary tissues.

Concentration-dependent effects of alendronate and pamidronate functionalized gold nanoparticles on osteoclast and osteoblast viability

Severe osteoporotic diseases, such as Paget's disease, Osteogenesis Imperfecta, and Legg Calve Perthes disease, lack treatments that address the pathobiology of the diseases, as well as, long-term and prospective studies. Bisphosphonates, which are known to dramatically hinder the viability of osteoclast cells, along with gold nanoparticles (GNP) are a potential theranostic for osteoporotic diseases. We evaluated GNP functionalized with two different bisphosphonates, namely, alendronate and pamidronate. RANKL differentiated murine pre-osteoclasts (Raw 264.7) and murine osteoblasts (7F2) were treated with varying concentrations ranging from 0.1-5 µM of free and GNP bound bisphosphonates. GNPs with an average size of ∼15 nm were functionalized with alendronate and pamidronate through surface modification by self-assembly. MTT viability assay results show no changes in viability of the osteoclasts when treated with free bisphosphonates in the range of 1-5 µM, but significant decrease on treatment with functionalized GNP at concentrations above the range of 0.1-1 µM depending on the bisphosphonate. Osteoblast cell viability is maintained at all but the highest concentrations used. Qualitative and quantitative characterization by Western Blot for RANKL expression in the osteoblast cell line shows that expression is largely maintained. These results provide a basis for methods that use bisphosphonate functionalized GNP in the treatment of osteoporotic bone diseases. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 21-29, 2017.

Gold nanostars mediated combined photothermal and photodynamic therapy and X-ray imaging for cancer theranostic applications

Gold nanomaterials possess unique physical and chemical properties, which attracted much attention in recent years. As a new type of gold nanomaterials, gold nanostars (GNSTs) have been prepared and characterized in this study. GNSTs under near-infrared (NIR) light irradiation can exert not only cancer photothermal therapy via heat production but also photodynamic therapy via generation of reactive oxygen species. GNSTs were able to enter the cytoplasm as well as nuclei of human breast michigan cancer foundation-7 (MCF-7) cells. Under NIR light irradiation, GNSTs caused more severe DNA damage, arrest the cell cycle in G0/G1 phase, and reduce more cellular glutathione level, causing more severe apoptosis and cell death in vitro. Intratumoral injection of GNSTs with NIR light irradiation significantly inhibited tumor growth in vivo. In addition, GNSTs were demonstrated to be a contrast agent for X-ray imaging. All the in vitro and in vivo results showed that GNSTs can be used for the potential diagnosis and medical treatment of cancer.

Biodistribution of X-ray iodinated contrast agent in nano-emulsions is controlled by the chemical nature of the oily core

In this study, we investigated the role of the chemical nature of the oil droplet core of nano-emulsions used as contrast agents for X-ray imaging on their pharmacokinetics and biodistribution. To this end, we formulated PEGylated nano-emulsions with two iodinated oils (i.e., iodinated monoglyceride and iodinated castor oil) and compared them with another iodinated nano-emulsion based on iodinated vitamin E. By using dynamic light scattering and transmission electron microscopy, the three iodinated nano-emulsions were found to exhibit comparable morphologies, size, and surface composition. Furthermore, they were shown to be endowed with very high iodine concentration, which leads to stronger X-ray attenuation properties as compared to the commercial iodinated nano-emulsion Fenestra VC. The three nano-emulsions were i.v. administered in mice and monitored by microcomputed tomography (micro-CT). They showed high contrast enhancement in blood with similar half-life around 6 h but very different accumulation sites. While iodinated monoglycerides exhibited low accumulation in liver and spleen, high accumulation in spleen was observed for iodinated castor oil and in liver for vitamin E. These data clearly highlighted the important role of the oil composition of the nano-emulsion core to obtain strong X-ray contrast enhancement in specific targets such as liver, spleen, or only blood. These differences in biodistribution were partly attributed to differences in the uptake of the nanodroplets by the macrophages in vitro. Another key feature of these nano-emulsions is their long half-elimination time (several weeks), which offers sufficient retention for micro-CT imaging. This work paves the way for the design of nanoparticulate contrast agents for X-ray imaging of selected organs.