Nanodisco balls: control over surface versus core loading of diagnostically active nanocrystals into polymer nanoparticles

PEGylation of Metal Oxide Nanoparticles Modulates Neutrophil Extracellular Trap Formation

Novel metal oxide nanoparticle (NP) contrast agents may offer safety and functionality advantages over conventional gadolinium-based contrast agents (GBCAs) for cancer diagnosis by magnetic resonance imaging. However, little is known about the behavior of metal oxide NPs, or of their effect, upon coming into contact with the innate immune system. As neutrophils are the body's first line of defense, we sought to understand how manganese oxide and iron oxide NPs impact leukocyte functionality. Specifically, we evaluated whether contrast agents caused neutrophils to release web-like fibers of DNA known as neutrophil extracellular traps (NETs), which are known to enhance metastasis and thrombosis in cancer patients. Murine neutrophils were treated with GBCA, bare manganese oxide or iron oxide NPs, or poly(lactic-co-glycolic acid) (PLGA)-coated metal oxide NPs with different incorporated levels of poly(ethylene glycol) (PEG). Manganese oxide NPs elicited the highest NETosis rates and had enhanced neutrophil uptake properties compared to iron oxide NPs. Interestingly, NPs with low levels of PEGylation produced more NETs than those with higher PEGylation. Despite generating a low rate of NETosis, GBCA altered neutrophil cytokine expression more than NP treatments. This study is the first to investigate whether manganese oxide NPs and GBCAs modulate NETosis and reveals that contrast agents may have unintended off-target effects which warrant further investigation.

Biodegradable AuNP-Based Plasmonic Nanogels as Contrast Agents for Computed Tomography and Photoacoustics

Gold nanoparticles (AuNP) are well-established contrast agents in computed tomography (CT) and photoacoustic imaging (PAI). A wide variety of AuNP sizes, shapes, and coatings have been reported for these applications. However, for clinical translation, AuNP should be excretable to avoid long-term accumulation and possible side effects. Sub-5 nm AuNP have the benefit to be excretable through kidney filtration, therefore their loading in biodegradable nanogels holds promise to result in contrast agents that have long circulation times in the vasculature and subsequent biodegradation for excretion. Polyphosphazenes are intrinsically biodegradable polymers capable of forming nanogels with high payloads, and to release their payloads upon degradation. The significant development in polyphosphazenes that have tailored degradation kinetics, and their formulation with drugs or contrast agents, has shown potential as a biodegradable platform for imaging vasculature and endogenous molecules, by combination of CT and PA modalities. Therefore, we herein present methods for the formulation of AuNP assemblies loaded in nanogels composed of biodegradable polyphosphazenes, with a size range from 50 to 200 nm. We describe protocols for their characterization by UV-vis spectroscopy, Fourier-transform infrared spectroscopy, various microscopy techniques, elemental quantification by induced coupling plasma optical emission spectroscopy and contrast production in both CT and PAI. Finally, we detail the methods to investigate their effect on cells, distribution in cells and imaging properties for detection of endogenous molecules.

Novel Treatment for Glioblastoma Delivered by a Radiation Responsive and Radiopaque Hydrogel

Successful treatment of glioblastoma (GBM) is hampered by primary tumor recurrence after surgical resection and poor prognosis, despite adjuvant radiotherapy and chemotherapy. In search of improved outcomes for this disease, quisinostat appeared as a lead compound in drug screening. A delivery system was devised for this drug and to exploit current clinical methodology: an injectable hydrogel, loaded with both the quisinostat drug and radiopaque gold nanoparticles (AuNP) as contrast agent, that can release these payloads as a response to radiation. This hydrogel grants high local drug concentrations, overcoming issues with current standards of care. Significant hydrogel degradation and quisinostat release were observed due to the radiation trigger, providing high in vitro anticancer activity. In vivo, the combination of radiotherapy and the radiation-induced delivery of quisinostat from the hydrogel, successfully inhibited tumor growth in a mice model bearing xenografted human GBM tumors with a total response rate of 67%. Long-term tolerability was observed after intratumoral injection of the quisinostat loaded hydrogel. The AuNP payload enabled precise image-guided radiation delivery and the monitoring of hydrogel degradation using computed tomography (CT). These exciting results highlight this hydrogel as a versatile imageable drug delivery platform that can be activated simultaneously to radiation therapy and potentially offers improved treatment for GBM.

Polyphosphazene immunoadjuvants: Historical perspective and recent advances

The development of successful vaccines has been increasingly reliant on the use of immunoadjuvants - additives, which can enhance and modulate immune responses to vaccine antigens. Immunoadjuvants of the polyphosphazene family encompass synthetic biodegradable macromolecules, which attain in vivo activity via antigen delivery and immunostimulation mechanisms. Over the last decades, the technology has witnessed evolvement of next generation members, expansion to include various antigens and routes of administration, and progression to clinical phase. This was accompanied by gaining important insights into the mechanism of action and the development of a novel class of virus-mimicking nano-assemblies for antigen delivery. The present review evaluates in vitro and in vivo data generated to date in the context of latest advances in understanding the primary function and biophysical behavior of these macromolecules. It also provides an overview of relevant synthetic and characterization methods, macromolecular biodegradation pathways, and polyphosphazene-based multi-component, nanoparticulate, and microfabricated formulations.

Tuning the size and composition of manganese oxide nanoparticles through varying temperature ramp and aging time

Manganese oxide (MnO) nanoparticles (NPs) can serve as robust pH-sensitive contrast agents for magnetic resonance imaging (MRI) due to Mn2+ release at low pH, which generates a ~30 fold change in T1 relaxivity. Strategies to control NP size, composition, and Mn2+ dissolution rates are essential to improve diagnostic performance of pH-responsive MnO NPs. We are the first to demonstrate that MnO NP size and composition can be tuned by the temperature ramping rate and aging time used during thermal decomposition of manganese(II) acetylacetonate. Two different temperature ramping rates (10°C/min and 20°C/min) were applied to reach 300°C and NPs were aged at that temperature for 5, 15, or 30 min. A faster ramping rate and shorter aging time produced the smallest NPs of ~23 nm. Shorter aging times created a mixture of MnO and Mn3O4 NPs, whereas longer aging times formed MnO. Our results indicate that a 20°C/min ramp rate with an aging time of 30 min was the ideal temperature condition to form the smallest pure MnO NPs of ~32 nm. However, Mn2+ dissolution rates at low pH were unaffected by synthesis conditions. Although Mn2+ production was high at pH 5 mimicking endosomes inside cells, minimal Mn2+ was released at pH 6.5 and 7.4, which mimic the tumor extracellular space and blood, respectively. To further elucidate the effects of NP composition and size on Mn2+ release and MRI contrast, the ideal MnO NP formulation (~32 nm) was compared with smaller MnO and Mn3O4 NPs. Small MnO NPs produced the highest amount of Mn2+ at acidic pH with maximum T1 MRI signal; Mn3O4 NPs generated the lowest MRI signal. MnO NPs encapsulated within poly(lactide-co-glycolide) (PLGA) retained significantly higher Mn2+ release and MRI signal compared to PLGA Mn3O4 NPs. Therefore, MnO instead of Mn3O4 should be targeted intracellularly to maximize MRI contrast.

Nanoparticle contrast agents for X-ray imaging applications

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.

Radioprotective garment-inspired biodegradable polymetal nanoparticles for enhanced CT contrast production

Numerous formulations of nanoparticle-based X-ray computed tomography (CT) contrast agents made of heavy metal elements are under investigation for their ability to provide improved CT imaging. Thus far, most experimental nanoparticle-based CT contrast agents have been developed with atoms of a single element. However, inspired by the composites formed from multiple elements used in radioprotective garments, we hypothesized that contrast agents made of several elements whose K-edge energies are spaced out in the high photon flux region could achieve high, broadband X-ray attenuation across the energies used in X-ray source spectra. Herein, we synthesized sub-5 nm core inorganic nanoparticles containing gold, tantalum, and cerium, and encapsulated them in polymeric nanoparticles to form polymetal nanoparticles (PMNP). We found that PMNP with multiple payload elements generate higher and more stable CT contrast than contrast agents made from a single contrast generating material, demonstrating the potential benefits of incorporating multiple suitable elements as CT contrast payloads.

Iron Oxide Nanoparticles for Breast Cancer Theranostics

BACKGROUND

Breast cancer is the second leading cause of death in women worldwide. The extremely fast rate of metastasis and ability to develop resistance mechanism to all the conventional drugs make them very difficult to treat which are the causes of high morbidity and mortality of breast cancer patients. Scientists throughout the world have been focusing on the early detection of breast tumor so that treatment can be started at the very early stage. Moreover, conventional treatment processes such as chemotherapy, radiotherapy, and local surgery suffer from various limitations including toxicity, genetic mutation of normal cells, and spreading of cancer cells to healthy tissues. Therefore, new treatment regimens with minimum toxicity to normal cells need to be urgently developed.

METHODS

Iron oxide nanoparticles have been widely used for targeting hyperthermia and imaging of breast cancer cells. They can be conjugated with drugs, proteins, enzymes, antibodies or nucleotides to deliver them to target organs, tissues or tumors using external magnetic field.

RESULTS

Iron oxide nanoparticles have been successfully used as theranostic agents for breast cancer both in vitro and in vivo. Furthermore, their functionalization with drugs or functional biomolecules enhance their drug delivery efficiency and reduces the systemic toxicity of drugs.

CONCLUSION

This review mainly focuses on the versatile applications of superparamagnetic iron oxide nanoparticles on the diagnosis, treatment, and detecting progress of breast cancer treatment. Their wide application is because of their excellent superparamagnetic, biocompatible and biodegradable properties.

Protein-loaded soluble and nanoparticulate formulations of ionic polyphosphazenes and their interactions on molecular and cellular levels

Nanoparticulate and water-soluble formulations of ionic polyphosphazenes and protein cargo - lysozyme (LYZ) were prepared by their self-assembly in aqueous solutions at near physiological pH (pH 7.4) in the presence and absence of an ionic cross-linker - spermine tetrahydrochloride. Efficiency of LYZ encapsulation, physico-chemical characteristics of formulations, and the effect of reaction parameters were investigated using asymmetric flow field flow fractionation (AF4) and dynamic light scattering (DLS) methods. The effect of both polymer formulations on encapsulated LYZ was evaluated using soluble oligosaccharide substrate, whereas their ability to present the protein to cellular surfaces was assessed by measuring enzymatic activity of encapsulated LYZ against Micrococcus lysodeikticus cells. It was found that both soluble and cross-linked polymer matrices reduce lysis of bacterial cells by LYZ, whereas activity of encapsulated protein against oligosaccharide substrate remained practically unchanged indicating no adverse effect of polyphosphazene on protein integrity. Moreover, nanoparticulate formulations display distinctly different behavior in cellular assays when compared to their soluble counterparts. LYZ encapsulated in polyphosphazene nanoparticles shows approximately 2.5-fold higher activity in its ability to lyse cells as compared with water-soluble LYZ-PCPP formulations. A new approach to PEGylation of polyphosphazene nanoparticles was also developed. The method utilizes a new ionic polyphosphazene derivative, which contains graft (polyethylene glycol) chains. PEGylation allows for an improved control over the size of nanoparticles and broader modulation of their cross-linking density, while still permitting for protein presentation to cellular substrates.

Activatable Hybrid Polyphosphazene-AuNP Nanoprobe for ROS Detection by Bimodal PA/CT Imaging

Overproduction of reactive oxygen species (ROS) is often related to inflammation or cancer and can cause tissue damage. Probes that have been previously reported to image ROS typically rely on imaging techniques that have low depth penetration in tissue, thus limiting their use to superficial disease sites. We report herein a novel formulation of hybrid nanogels loaded with gold nanoparticles (AuNP) to produce contrast for computed tomography (CT) and photoacoustics (PA), both being deep-tissue imaging techniques. The polyphosphazene polymer has been designed to selectively degrade upon ROS exposure, which triggers a switch-off of the PA signal by AuNP disassembly. This ROS-triggered degradation of the nanoprobes leads to a significant decrease in the PA contrast, thus allowing ratiometric ROS imaging by comparing the PA to CT signal. Furthermore, ROS imaging using these nanoprobes was applied to an in vitro model of inflammation, that is, LPS-stimulated macrophages, where ROS-triggered disassembly of the nanoprobe was confirmed via reduction of the PA signal. In summary, these hybrid nanoprobes are a novel responsive imaging agent that have the potential to image ROS overproduction by comparing PA to CT contrast.

Reactive oxygen species mediated theranostics using a Fenton reaction activable lipo-polymersome

Recently, reactive oxygen species (ROS)-induced apoptosis has been widely studied by researchers through various means. Among them, the singlet oxygen produced by the Fenton reaction is particularly effective in killing tumor cells. Although photodynamic therapy (PDT) takes advantage of the spatial-temporal control of ROS production, the design of the Fenton reaction in an ingenious way is still a question worth exploring. Herein, we have designed and prepared a succinic peroxide-filled Fenton reaction activable Pt/Fe₃O₄@SP-PLGA lipo-polymersome that displays ROS mediated chemodynamic therapy (CDT). The therapeutic element, ˙OH, is generated under NIR irradiation/tumor acidic pH environment through engineering the reaction between succinic peroxide (SP) and iron oxide. Instead of using single endogenous H₂O₂ or even encapsulation, the conjugation with SP in the Pt/Fe₃O₄@SP-PLGA lipo-polymersome provides a more stable, high-yielding peroxygen source. The results also showed that after the addition of cisplatin, the amount of ROS production increased significantly. The proof-of-concept design of the Fenton reaction activable Pt/Fe₃O₄@SP-PLGA lipo-polymersome with enhanced ROS-generation characteristics provides a general approach to afford potent ROS-mediated cancer therapy.

The Toxicity Assessment of Iron Oxide (Fe₃O₄) Nanoparticles on Physical and Biochemical Quality of Rainbow Trout Spermatozoon

The aim of this study was to evaluate the in vitro effect of different doses (50, 100, 200, 400, and 800 mg/L) of Fe₃O₄ nanoparticles (NPs) at 4 °C for 24 h on the kinematics of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) spermatozoon. Firstly, Fe₃O₄ NPs were prepared at about 30 nm from Iron (III) chloride, Iron (II) chloride, and NH₃ via a co-precipitation synthesis technique. Then, the prepared Fe₃O₄ NPs were characterized by different instrumental techniques for their chemical structure, purity, morphology, surface properties, and thermal behavior. The size, microstructure, and morphology of the prepared Fe₃O₄ NPs were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) spectroscopy, and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). The thermal properties of the Fe₃O₄ NPs were determined with thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimeter (DSC) analysis techniques. According to our results, there were statistically significant (p < 0.05) decreases in the velocities of spermatozoon after treatment with 400 mg/L Fe₃O₄ NPs. The superoxide dismutase (SOD) and catalase (CAT) activities were significant (p < 0.05) decrease after 100 mg/L in after exposure to Fe₃O₄ NPs in 24 h. As the doses of Fe₃O₄ NPs increases, the level of malondialdehyde (MDA) and total glutathione (tGSH) significantly (p < 0.05) increased at doses of 400 and 800 mg/L.

Single-trigger dual-responsive nanoparticles for controllable and sequential prodrug activation

Here we have developed a novel approach where two synergistically acting drugs were completely inactivated upon chemical immobilization on a nanoparticle template and activated in response to a chemical stimulus. The activation rate of each drug payload is controlled using a biologically inert bioorthogonal chemistry approach. By exploiting the subtle differences in the 'click-to-release' bioorthogonal reaction, we engineered a single delivery platform capable of releasing the payloads in a time-staggered manner in response to a single dose of a highly specific, yet reactive, small molecule. Incorporation of both di-axial, 'fast release', and di-equatorial, 'slow release', TCO linkers into our nanodrug assembly inhibited the activity of the drug molecules and enabled us to control the timing and activation of each payload. This single-trigger dual-responsive nanoparticle construct and its release kinetics were characterized using two molecular fluorescent probes and tested in vitro for efficient delivery of molecular payloads. In this manuscript we show that this approach was also successful in the treatment of triple negative BT-20 breast cancer cells. Our nanodrug loaded with the slow-releasing doxorubicin and fast-releasing PAC-1 prodrugs displayed a greater therapeutic response than the nanodrug which released both payloads simultaneously.

Towards a classification strategy for complex nanostructures

The range of possible nanostructures is so large and continuously growing, that collating and unifying the knowledge connected to them, including their biological activity, is a major challenge. Here we discuss a concept that is based on the connection of microscopic features of the nanomaterials to their biological impacts. We also consider what would be necessary to identify the features that control their biological interactions, and make them resemble each other in a biological context.

Controlled in-cell activation of RNA therapeutics using bond-cleaving bio-orthogonal chemistry

In vitro exogenous activation of siRNA nanodrug using bio-orthogonal de-click chemistry.

Temporal control of siRNA activation is a major challenge for RNAi-based therapeutics. The majority of the reported siRNA delivery systems rely on environmental factors, such as differences in extracellular and intracellular redox potential, ATP concentration, or pH to activate an siRNA payload. However dynamic endogenous environments are far too complex to rely on for controllable siRNA release and can result in premature siRNA activation prior to reaching the intended biological target. In addition, there are uncertainties about timing, degree and rate of the siRNA activation with spontaneous release approaches. Herein we describe a bio-orthogonal chemistry approach to address this important challenge. With our approach we were able achieve two major goals: complete siRNA inactivation upon immobilization of the payload on the surface of iron oxide nanoparticles and controlled in-cell activation with the addition of a small non-toxic chemical trigger after sufficient cellular uptake of the nanoparticles was confirmed. We have demonstrated our in-cell activation approach using two siRNAs against green fluorescent protein (GFP) and cyclin dependent kinase 8 (CDK8) in GFP expressing MDA-MB-231 cell line. We anticipate that this methodology will potentially advance the clinical translation of RNAi-based therapeutics, as the described bio-orthogonal chemistry can be generalized for any siRNA of choice.

Biodegradable "Smart" Polyphosphazenes with Intrinsic Multifunctionality as Intracellular Protein Delivery Vehicles

A series of biodegradable drug delivery polymers with intrinsic multifunctionality have been designed and synthesized utilizing a polyphosphazene macromolecular engineering approach. Novel water-soluble polymers, which contain carboxylic acid and pyrrolidone moieties attached to an inorganic phosphorus-nitrogen backbone, were characterized by a suite of physicochemical methods to confirm their structure, composition, and molecular sizes. All synthesized polyphosphazenes displayed composition-dependent hydrolytic degradability in aqueous solutions at neutral pH. Their formulations were stable at lower temperatures, potentially indicating adequate shelf life, but were characterized by accelerated degradation kinetics at elevated temperatures, including 37 °C. It was found that synthesized polyphosphazenes are capable of environmentally triggered self-assembly to produce nanoparticles with narrow polydispersity in the size range of 150-700 nm. Protein loading capacity of copolymers has been validated via their ability to noncovalently bind avidin without altering biological functionality. Acid-induced membrane-disruptive activity of polyphosphazenes has been established with an onset corresponding to the endosomal pH range and being dependent on polymer composition. The synthesized polyphosphazenes facilitated cell-surface interactions followed by time-dependent, vesicular-mediated, and saturable internalization of a model protein cargo into cancer cells, demonstrating the potential for intracellular delivery.

Tunable, biodegradable gold nanoparticles as contrast agents for computed tomography and photoacoustic imaging

Gold nanoparticles (AuNP) have been proposed for many applications in medicine. Although large AuNP (>5.5 nm) are desirable for their longer blood circulation and accumulation in diseased tissues, small AuNP (<5.5 nm) are required for excretion via the kidneys. We present a novel platform where small, excretable AuNP are encapsulated into biodegradable poly di(carboxylatophenoxy)phosphazene (PCPP) nanospheres. These larger nanoparticles (Au-PCPP) can perform their function as contrast agents, then subsequently break down into harmless byproducts and release the AuNP for swift excretion. Homogeneous Au-PCPP were synthesized using a microfluidic device. The size of the Au-PCPP can be controlled by the amount of polyethylene glycol-polylysine (PEG-PLL) block co-polymer in the formulation. Synthesis of Au-PCPP nanoparticles and encapsulation of AuNP in PCPP were evaluated using transmission electron microscopy and their biocompatibility and biodegradability confirmed in vitro. The Au-PCPP nanoparticles were found to produce strong computed tomography contrast. The UV-Vis absorption peak of Au-PCPP can be tuned into the near infrared region via inclusion of varying amounts of AuNP and controlling the nanoparticle size. In vitro and in vivo experiments demonstrated the potential of Au-PCPP as contrast agents for photoacoustic imaging. Therefore, Au-PCPP nanoparticles have high potency as contrast agents for two imaging modalities, as well as being biocompatible and biodegradable, and thus represent a platform with potential for translation into the clinic.

Self-Assembly of Colloidal Nanocrystals: From Intricate Structures to Functional Materials

Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micrometer colloids and block copolymer assembly. We outline the extensive catalog of superlattices prepared to date using hydrocarbon-capped nanocrystals with spherical, polyhedral, rod, plate, and branched inorganic core shapes, as well as those obtained by mixing combinations thereof. We also provide an overview of structural defects in nanocrystal superlattices. We then explore the unique possibilities offered by leveraging nontraditional surface chemistries and assembly environments to control superlattice structure and produce nonbulk assemblies. We end with a discussion of the unique optical, magnetic, electronic, and catalytic properties of ordered nanocrystal superlattices, and the coming advances required to make use of this new class of solids.

Gold silver alloy nanoparticles (GSAN): an imaging probe for breast cancer screening with dual-energy mammography or computed tomography

Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening.

Film-Stabilizing Attributes of Polymeric Core-Shell Nanoparticles

Self-organization of nanoparticles into stable, molecularly thin films provides an insightful paradigm for manipulating the manner in which materials interact at nanoscale dimensions to generate unique material assemblies at macroscopic length scales. While prior studies in this vein have focused largely on examining the performance of inorganic or organic/inorganic hybrid nanoparticles (NPs), the present work examines the stabilizing attributes of fully organic core-shell microgel (CSMG) NPs composed of a cross-linked poly(ethylene glycol dimethacrylate) (PEGDMA) core and a shell of densely grafted, but relatively short-chain, polystyrene (PS) arms. Although PS homopolymer thin films measuring from a few to many nanometers in thickness, depending on the molecular weight, typically dewet rapidly from silica supports at elevated temperatures, spin-coated CSMG NP films measuring as thin as 10 nm remain stable under identical conditions for at least 72 h. Through the use of self-assembled monolayers (SAMs) to alter the surface of a flat silica-based support, we demonstrate that such stabilization is not attributable to hydrogen bonding between the acrylic core and silica. We also document that thin NP films consisting of three or less layers (10 nm) and deposited onto SAMs can be fully dissolved even after extensive thermal treatment, whereas slightly thicker films (40 nm) on Si wafer become only partially soluble during solvent rinsing with and without sonication. Taken together, these observations indicate that the present CSMG NP films are stabilized primarily by multidirectional penetration of relatively short, unentangled NP arms caused by NP layering, rather than by chain entanglement as in linear homopolymer thin films. This nanoscale "velcro"-like mechanism permits such NP films, unlike their homopolymer counterparts of comparable chain length and thickness, to remain intact as stable, free-floating sheets on water, and thus provides a viable alternative to ultrathin organic coating strategies.

MnFe2O4–Fe3O4 core–shell nanoparticles as a potential contrast agent for magnetic resonance imaging

In recent years, magnetic core–shell nanoparticles have received widespread attention due to their unique properties that can be used for various applications.