Lipid-based nanoparticles for contrast-enhanced MRI and molecular imaging

Organic Nanoparticles in Progressing Cardiovascular Disease Treatment and Diagnosis

Cardiovascular diseases (CVDs), the world's most prominent cause of mortality, continue to be challenging conditions for patients, physicians, and researchers alike. CVDs comprise a wide range of illnesses affecting the heart, blood vessels, and the blood that flows through and between them. Advances in nanomedicine, a discipline focused on improving patient outcomes through revolutionary treatments, imaging agents, and ex vivo diagnostics, have created enthusiasm for overcoming limitations in CVDs' therapeutic and diagnostic landscapes. Nanomedicine can be involved in clinical purposes for CVD through the augmentation of cardiac or heart-related biomaterials, which can be functionally, mechanically, immunologically, and electrically improved by incorporating nanomaterials; vasculature applications, which involve systemically injected nanotherapeutics and imaging nanodiagnostics, nano-enabled biomaterials, or tissue-nanoengineered solutions; and enhancement of sensitivity and/or specificity of ex vivo diagnostic devices for patient samples. Therefore, this review discusses the latest studies based on applying organic nanoparticles in cardiovascular illness, including drug-conjugated polymers, lipid nanoparticles, and micelles. Following the revised information, it can be concluded that organic nanoparticles may be the most appropriate type of treatment for cardiovascular diseases due to their biocompatibility and capacity to integrate various drugs.

Progress of Mesoporous Silica Coated Gold Nanorods for Biological Imaging and Cancer Therapy

For unique surface plasmon absorption and fluorescence characteristics, gold nanorods have been developed and widely employed in the biomedical field. However, limitations still exist due their low specific surface area, instability and tendency agglomerate in cytoplasm. Mesoporous silica materials have been broadly applied in field of catalysts, adsorbents, nanoreactors, and drug carriers due to its unique mesoporous structure, highly comparative surface area, good stability and biocompatibility. Therefore, coating gold nanorods with a dendritic mesopore channels can effectively prevent particle agglomeration, while increasing the specific surface area and drug loading efficiency. This review discusses the advancements of GNR@MSN in synthetic process, bio-imaging technique and tumor therapy. Additionally, the further application of GNR@MSN in imaging-guided treatment modalities is explored, while its promising superior application prospect is highlighted. Finally, the issues related to in vivo studies are critically examined for facilitating the transition of this promising nanoplatform into clinical trials.

Liposomal MRI probes containing encapsulated or amphiphilic Fe(III) coordination complexes

Liposomes containing high-spin Fe(III) coordination complexes were prepared towards the production of T1 MRI probes with improved relaxivity. The amphiphilic Fe(III) complexes were anchored into the liposome with two alkyl chains to give a coordination sphere containing mixed amide and hydroxypropyl pendant groups. The encapsulated complex contains a macrocyclic ligand with three phosphonate pendants, [Fe(NOTP)]3-, which was chosen for its good aqueous solubility. Four types of MRI probes were prepared including those with intraliposomal Fe(III) complex (LipoA) alone, amphiphilic Fe(III) complex (LipoB), both intraliposomal and amphiphilic complex (LipoC) or micelles formed with amphiphilic complex. Water proton relaxivities r1 and r2 were measured and compared to a small molecule macrocyclic Fe(III) complex containing similar donor groups. Micelles of the amphiphilic Fe(III) complex had proton relaxivity values (r1 = 2.6 mM-1 s-1) that were four times higher than the small hydrophilic analog. Liposomes with amphiphilic Fe(III) complex (LipoB) have a per iron relaxivity of 2.6 mM-1 s-1 at pH 7.2, 34 °C at 1.4 T whereas liposomes containing both amphiphilic and intraliposomal Fe(III) complexes (lipoC) have r1 of 0.58 mM-1 s-1 on a per iron basis consistent with quenching of the interior Fe(III) complex relaxivity. Liposomes containing only encapsulated [Fe(NOTP)]3- have a lowered r1 of 0.65 mM-1 s-1 per iron complex. Studies show that the biodistribution and clearance of the different types liposomal nanoparticles differ greatly. LipoB is a blood pool agent with a long circulation time whereas lipoC is cleared more rapidly through both renal and hepatobiliary pathways. These clearance differences are consistent with lower stability of LipoC compared to LipoB.

Development of targeted photodynamic therapy drugs by combining a zinc phthalocyanine sensitizer with TSPO or EGFR binding groups: the impact of the number of targeting agents on biological activity

Drug-targeted delivery has become a top priority in the world of medicine in order to develop more efficient therapeutic agents. This is important as a critical underlying problem in cancer therapy stems from the inability to deliver active therapeutic substances directly to tumor cells without causing collateral damage. In this work, zinc(II) phthalocyanine (ZnPc) was selected as a sensitizer and was linked to different targeting agents, which would be recognized by overexpressed proteins in cancer cells. As targeting agents, we first selected the two ligands (DAA1106, PK11195) of the translocator protein (TSPO) and then Erlotinib a binding group of the ATP domain of tyrosine kinase in epidermal growth factor (EGFR). ZnPc was connected via an ethylene glycol chain to either one (n = 1) or four (n = 4) targeting agents. The biological activity of these conjugates ZnPc(ligand)n was investigated on MDA-MB-231 breast human cancer cells and human hepatoma HepG2 cells, first in the dark (cytotoxicity) and then under irradiation (photodynamic therapy). The dark cytotoxicity was extremely low (IC50 ≥ 50 μM) for all of these compounds, which is a required criterion for further photodynamic application. After irradiation at 650 nm, only the conjugates bearing one targeting ligand such as ZnPc-[DAA1106]1, ZnPc-[PK11195]1, and ZnPc-[Erlo]1 showed photodynamic activity, while those linked to 4 targeting agents were inactive. Importantly, fluorescence imaging microscopy showed the colocalization of ZnPc-[DAA1106]1, ZnPc-[PK11195]1 and ZnPc-[erlo]1, at mitochondria, a result that justifies the observed photodynamic activity of these conjugates. This study first shows the impact of the number and the mode of organization of targeting agents on the ability of the sensitizer to cross the cell membrane. When zinc(II) phthalocyanine carries a single targeting agent, a significant photodynamic activity on MDA-MB-231 breast human cancer cells was measured and localization at the mitochondria was demonstrated by fluorescence imaging, thus proving the potential of the sensitizer linked to a targeting agent to improve selectivity. Another important conclusion from this study for the design of future effective PDT drugs using multivalence effects is to control the arrangement of the targeting agents in order to design molecules that will be able to pass the cell membrane barriers.

Nanomaterial-based contrast agents

Medical imaging, which empowers the detection of physiological and pathological processes within living subjects, has a vital role in both preclinical and clinical diagnostics. Contrast agents are often needed to accompany anatomical data with functional information or to provide phenotyping of the disease in question. Many newly emerging contrast agents are based on nanomaterials as their high payloads, unique physicochemical properties, improved sensitivity and multimodality capacity are highly desired for many advanced forms of bioimaging techniques and applications. Here, we review the developments in the field of nanomaterial-based contrast agents. We outline important nanomaterial design considerations and discuss the effect on their physicochemical attributes, contrast properties and biological behaviour. We also describe commonly used approaches for formulating, functionalizing and characterizing these nanomaterials. Key applications are highlighted by categorizing nanomaterials on the basis of their X-ray, magnetic, nuclear, optical and/or photoacoustic contrast properties. Finally, we offer our perspectives on current challenges and emerging research topics as well as expectations for future advancements in the field.

A Novel Strategy for Liposomal Drug Separation in Plasma by TiO2 Microspheres and Application in Pharmacokinetics

Purpose

Liposomes are nano-scale materials with a biofilm-like structure. They have excellent biocompatibility and are increasingly useful in drug delivery systems. However, the in vivo fate of liposomal drugs is still unclear because existing bioanalytical methods for quantitation of total and liposomal-encapsulated drugs have limits. A novel strategy for liposomal-encapsulated drug separation from plasma was developed via the specific coordinate binding interaction of TiO₂ microspheres with the phosphate groups of liposomes.

Methods

Liposomal-encapsulated docetaxel was separated from plasma by TiO₂ microspheres and analyzed by the UPLC-MS/MS method. The amount of TiO₂, pH of the dilutions, plasma dilution factors and incubation time were optimized to improve extraction recovery. The characterization of the adsorption of liposome-encapsulated drugs by TiO₂ microspheres was observed by electron microscopy. For understanding the mechanism, pseudo-first and the pseudo-second order equations were proposed for the adsorption process. The study fully validated the method for quantitation of liposomal-encapsulated in plasma and the method was applied to the pharmacokinetic study of docetaxel liposomes.

Results

The encapsulated docetaxel had a concentration range of 15-4000 ng/mL from the plasma sample using a TiO₂ extraction method. Successful method validation proved the method was sensitive, selective and stable, and was suitable for quantitation of docetaxel liposomes in plasma samples. Extraction recovery of this method was higher than that of SPE method. As shown in electron microscopy, the liposomes adsorbed on TiO₂ microspheres were intact and there was no drug leakage. The study proposed pseudo-first and the pseudo-second order equations to facilitate the adsorption of liposomal drugs with TiO₂ microspheres. The proposed strategy supports the pharmacokinetic study of docetaxel liposomes in rats.

Conclusion

TiO₂ extraction method was stable, reproducible, and reliable for quantitation of encapsulated docetaxel. Because of versatility of lipids, it is expected to a universal bioanalysis method for the pharmacokinetic study of liposomes.

One-Pot, One-Step Synthesis of Drug-Loaded Magnetic Multimicelle Aggregates

Lipid-based formulations provide a nanotechnology platform that is widely used in a variety of biomedical applications because it has several advantageous properties including biocompatibility, reduced toxicity, relative ease of surface modifications, and the possibility for efficient loading of drugs, biologics, and nanoparticles. A combination of lipid-based formulations with magnetic nanoparticles such as iron oxide was shown to be highly advantageous in a growing number of applications including magnet-mediated drug delivery and image-guided therapy. Currently, lipid-based formulations are prepared by multistep protocols. Simplification of the current multistep procedures can lead to a number of important technological advantages including significantly decreased processing time, higher reaction yield, better product reproducibility, and improved quality. Here, we introduce a one-pot, single-step synthesis of drug-loaded magnetic multimicelle aggregates (MaMAs), which is based on controlled flow infusion of an iron oxide nanoparticle/lipid mixture into an aqueous drug solution under ultrasonication. Furthermore, we prepared molecular-targeted MaMAs by directional antibody conjugation through an Fc moiety using Cu-free click chemistry. Fluorescence imaging and quantification confirmed that antibody-conjugated MaMAs showed high cell-specific targeting that was enhanced by magnetic delivery.

Liposomal Drug Delivery And Its Potential Impact On Cancer Research

Liposomes are one of the most versatile drug carriers due to their functional properties, such as higher biocompatibility, the ability to encapsulate hydrophilic and hydrophobic products, and higher biodegradability. Liposomes are a better and more significant nanocarrier for cancer therapy. The key to developing a better cancer-targeted nanocarrier is the development of targeted liposomes using various approaches. Several traditional and novel liposome preparation methods are briefly discussed in this mini-review. The current state of liposome targeting, active and passive liposome targeting in cancer therapy, ligand directed targeting (antibody, aptamer, and protein/peptide-mediated targeting), and other miscellaneous approaches such as stimuli-responsive liposome-based targeting, autophagy inhibition mediated targeting, and curcumin loaded liposomal targeting are all discussed within. All of this gathered and compiled information will shed new light on liposome targeting strategies in cancer treatment and will pique the interest of aspiring researchers and academicians.

Gold nanostructures: synthesis, properties, and neurological applications

Recent advances in technology are expected to increase our current understanding of neuroscience. Nanotechnology and nanomaterials can alter and control neural functionality in both in vitro and in vivo experimental setups. The intersection between neuroscience and nanoscience may generate long-term neural interfaces adapted at the molecular level. Owing to their intrinsic physicochemical characteristics, gold nanostructures (GNSs) have received much attention in neuroscience, especially for combined diagnostic and therapeutic (theragnostic) purposes. GNSs have been successfully employed to stimulate and monitor neurophysiological signals. Hence, GNSs could provide a promising solution for the regeneration and recovery of neural tissue, novel neuroprotective strategies, and integrated implantable materials. This review covers the broad range of neurological applications of GNS-based materials to improve clinical diagnosis and therapy. Sub-topics include neurotoxicity, targeted delivery of therapeutics to the central nervous system (CNS), neurochemical sensing, neuromodulation, neuroimaging, neurotherapy, tissue engineering, and neural regeneration. It focuses on core concepts of GNSs in neurology, to circumvent the limitations and significant obstacles of innovative approaches in neurobiology and neurochemistry, including theragnostics. We will discuss recent advances in the use of GNSs to overcome current bottlenecks and tackle technical and conceptual challenges.

MRI in Pregnancy and Precision Medicine: A Review from Literature

Magnetic resonance imaging (MRI) offers excellent spatial and contrast resolution for evaluating a wide variety of pathologies, without exposing patients to ionizing radiations. Additionally, MRI offers reproducible diagnostic imaging results that are not operator-dependent, a major advantage over ultrasound. MRI is commonly used in pregnant women to evaluate, most frequently, acute abdominal and pelvic pain or placental abnormalities, as well as neurological or fetal abnormalities, infections, or neoplasms. However, to date, our knowledge about MRI safety during pregnancy, especially about the administration of gadolinium-based contrast agents, which are able to cross the placental barrier, is still limited, raising concerns about possible negative effects on both the mother and the health of the fetus. Contrast agents that are unable to cross the placenta in a way that is safe for the fetus are desirable. In recent years, some preclinical studies, carried out in rodent models, have evaluated the role of long circulating liposomal nanoparticle-based blood-pool gadolinium contrast agents that do not penetrate the placental barrier due to their size and therefore do not expose the fetus to the contrast agent during pregnancy, preserving it from any hypothetical risks. Hence, we performed a literature review focusing on contrast and non-contrast MRI use during pregnancy.

Liposomal Fe(III) Macrocyclic Complexes with Hydroxypropyl Pendants as MRI Probes

Paramagnetic liposomes containing Fe(III) complexes were prepared by incorporation of mononuclear (Fe(L1) or Fe(L3)) or dinuclear (Fe₂(L2)) coordination complexes of 1,4,7-triazacyclononane macrocycles containing 2-hydroxypropyl pendant groups. Two different types of paramagnetic liposomes were prepared. The first type, LipoA, has the mononuclear Fe(L1) complex loaded into the internal aqueous core. The second type, LipoB, has the amphiphilic Fe(L3) complex inserted into the liposomal bilayer and the internal aqueous core loaded with either Fe(L1) (LipoB1) or Fe₂(L2) (LipoB2). LipoA enhances both T₁ and T₂ water proton relaxation rates. Treatment of LipoA with osmotic gradients to produce a nonspherical liposome produces a liposome with a chemical exchange saturation transfer effect as shown by an asymmetry analysis but only at high osmolarity. LipoB1, which contains an amphiphilic complex in the liposomal bilayer, produced a broadened Z-spectrum upon treatment of the liposome with osmotic gradients. The r₁ relaxivity of LipoB1 and LipoB2 were higher than the r₁ relaxivity of LipoA on a per Fe basis, suggesting an important contribution from the amphiphilic Fe(III) center. The r₁ relaxivities of paramagnetic liposomes are relatively constant over a range of magnetic field strengths (1.4-9.4 T), with the ratio of r₂/r₁ substantially increasing at high field strengths. MRI studies of LipoB1 in mice showed prolonged contrast enhancement in blood compared to the clinically employed Gd(DOTA), which was injected at a 2-fold higher dose per metal than the Fe(III)-loaded liposomes.

Polymerizable Gd(iii) building blocks for the synthesis of high relaxivity macromolecular MRI contrast agents

A new synthetic strategy for the preparation of macromolecular MRI contrast agents (CAs) is reported. Four gadolinium(iii) complexes bearing either one or two polymerizable methacrylamide groups were synthesized, serving as monomers or crosslinkers for the preparation of water-soluble, polymeric CAs using Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization. Using this approach, macromolecular CAs were synthesized with different architectures, including linear, hyperbranched polymers and gels. The relaxivities of the polymeric CAs were determined by NMR relaxometry, revealing an up to 5-fold increase in relaxivity (60 MHz, 310 K) for the linear polymers compared with the clinically used CA, Gd-DOTA. Moreover, hyperbranched polymers obtained from Gd(iii) crosslinkers, displayed even higher relaxivities up to 22.8 mM⁻¹ s⁻¹, approximately 8 times higher than that of Gd-DOTA (60 MHz, 310 K). A detailed NMRD study revealed that the enhanced relaxivities of the hyperbranched polymers were obtained by limiting the local motion of the crosslinked Gd(iii) chelate. The versatility of RAFT polymerization of Gd(iii) monomers and crosslinkers opens the doors to more advanced polymeric CAs capable of multimodal, bioresponsive or targeting properties.

A new synthetic strategy for the preparation of efficient macromolecular MRI contrast agents is reported.

LDL-mimetic lipid nanoparticles prepared by surface KAT ligation for in vivo MRI of atherosclerosis

Low-density lipoprotein (LDL)-mimetic lipid nanoparticles (LNPs), decorated with MRI contrast agents and fluorescent dyes, were prepared by the covalent attachment of apolipoprotein-mimetic peptide (P), Gd(iii)-chelate (Gd), and sulforhodamine B (R) moieties on the LNP surface. The functionalized LNPs were prepared using the amide-forming potassium acyltrifluoroborate (KAT) ligation reaction. The KAT groups on the surface of LNPs were allowed to react with the corresponding hydroxylamine (HA) derivatives of P and Gd to provide bi-functionalized LNPs (PGd-LNP). The reaction proceeded with excellent yields, as observed by ICP-MS (for B and Gd amounts) and MALDI-TOF-MS data, and did not alter the morphology of the LNPs (mean diameter: ca. 50 nm), as shown by DLS and cryoTEM analyses. With the help of the efficient KAT ligation, a high payload of Gd(iii)-chelate on the PGd-LNP surface (ca. 2800 Gd atoms per LNP) was successfully achieved and provided a high r₁ relaxivity (r₁ = 22.0 s⁻¹ mM⁻¹ at 1.4 T/60 MHz and 25 °C; r₁ = 8.2 s⁻¹ mM⁻¹ at 9.4 T/400 MHz and 37 °C). This bi-functionalized PGd-LNP was administered to three atherosclerotic apoE^−/− mice to reveal the clear enhancement of atherosclerotic plaques in the brachiocephalic artery (BA) by MRI, in good agreement with the high accumulation of Gd in the aortic arch as shown by ICP-MS. The parallel in vivo MRI and ex vivo studies of whole mouse cryo-imaging were performed using triply functionalized LNPs with P, Gd, and R (PGdR-LNP). The clear presence of atherosclerotic plaques in BA was observed by ex vivo bright field cryo-imaging, and they were also observed by high emission fluorescent imaging. These directly corresponded to the enhanced tissue in the in vivo MRI of the identical mouse.

LDL-mimetic lipid nanoparticles, decorated with MRI contrast agents and fluorescent dyes, were prepared by the covalent attachments of an apoB100-mimetic peptide, Gd(iii)-chelate, and rhodamine to enhance atherosclerosis in the in vivo imaging.

Liposome-Based Bioassays

This review highlights the potential of using liposomes in bioassays. Liposomes consist of nano- or micro-sized, synthetically constructed phospholipid vesicles. Liposomes can be loaded with a number of reporting molecules that allow a dramatic amplification of the detection threshold in bioassays. Liposome-based sensors bind or react with the biological components of targets through the introduction of properly tailored vectors anchored on their external surface. The use of liposome-based formulations allows the set-up of bioassays that are rapid, sensitive, and often suitable for in-field applications. Selected applications in the field of immunoassays, as well as recognition/assessment of corona proteins, nucleic acids, exosomes, bacteria, and viruses are surveyed. The role of magnetoliposomes is also highlighted as an additional tool in the armory of liposome-based systems for bioassays.

Relaxometric Studies of Gd-Chelate Conjugated on the Surface of Differently Shaped Gold Nanoparticles

Nowadays, magnetic resonance imaging (MRI) is one of the key, noninvasive modalities to detect and stage cancer which benefits from contrast agents (CA) to differentiate healthy from tumor tissue. An innovative class of MRI CAs is represented by Gd-loaded gold nanoparticles. The size, shape and chemical functionalization of Gd-loaded gold nanoparticles appear to affect the observed relaxation enhancement of water protons in their suspensions. The herein reported results shed more light on the determinants of the relaxation enhancement brought by Gd-loaded concave cube gold nanoparticles (CCGNPs). It has been found that, in the case of nanoparticles endowed with concave surfaces, the relaxivity is remarkably higher compared to the corresponding spherical (i.e., convex) gold nanoparticles (SPhGNPs). The main determinant for the observed relaxation enhancement is represented by the occurrence of a large contribution from second sphere water molecules which can be exploited in the design of high-efficiency MRI CA.

Mn(II)-Based Lipidic Nanovesicles as High-Efficiency MRI Probes

Although nowadays there is a renewed and growing interest in Mn-based contrast agents, there are only few studies dealing with Mn-based lipophilic nanoparticles and how they may be optimized as MRI contrast agents. Three amphiphilic paramagnetic Mn(II) complexes based on derivatives of EDTA and 1,4-DO2A were used for the preparation of lipidic nanoparticles. The length and position of the aliphatic chains were found to control whether either vesicular liposomes, nonvesicular bicelles, or a mixture of both was produced as well as the size and morphology of phospholipid-based self-assembling nanoaggregates. These differences determine whether hydrophilic Gd-based contrast agents or fluorescent dyes can be entrapped in the aqueous core of the nanoaggregate. Structural characterization was performed by cryo-TEM. Detailed ¹H NMR relaxometric analyses were carried out on all systems. The effect of entrapping gadoteridol in the aqueous core (where present) was studied by preparing diamagnetic amphiphilic Zn(II) analogues. In the case of homogeneous systems, the data were also fitted to obtain the relaxometric parameters for comparison with literature data. The results of these studies demonstrate enhanced relaxivity of the nanoaggregates with respect to monomeric analogues. This work allowed us to understand how to control the formation of different types of nanovesicles (liposomes, bicelles, and micelles), optimize their MRI contrast, and provide different in vivo biodistribution characteristics.

Time-course study of a gold nanoparticle contrast agent for cardiac-gated micro-CT imaging in mice

Although micro-computed tomography (micro-CT) images have high contrast for bone or air, between soft tissues the contrast is typically low. To overcome this inherent issue, attenuating exogenous contrast agents are used to provide contrast enhancement in the vasculature and abdominal organs. The aim of this study is to measure the contrast enhancement time course for a gold nanoparticle blood-pool contrast agent and use it to perform cardiac-gated 4D micro-CT scans of the heart. Six healthy female C57BL/6 mice were anesthetized and imaged after receiving an injected dose of MVivo gold nanoparticle blood-pool contrast agent. Following the injection, we performed micro-CT scans at 0, 0.25, 0.5, 0.75, 1, 2, 4, 8, 24, 48 and 72 h. The mean CT number was measured for 7 different organs. No contrast enhancement was noticed in the bladder, kidneys or muscle during the time-course study. However, it clearly appears that the contrast enhancement is high in both right ventricle and vena cava. To perform cardiac-gated imaging, either the gold nanoparticle agent (n = 3) or an iodine-based (n = 3) contrast agent was introduced and images representing 9 phases of the cardiac cycle were obtained in 6 additional mice. A few typical cardiac parameters were measured or calculated, with similar accuracy between the gold and iodinated agents, but better visualization of structures with the gold agent. The MVivo Au contrast agent can be used for investigations of cardiac or vascular disease with a single bolus injection, with an optimal cardiac imaging window identified during the first hour after injection, demonstrating similar image quality to iodinated contrast agents and excellent measurement accuracy. Furthermore, the long-lasting contrast enhancement of up to 8 h can be very useful for scanning protocols that require longer acquisition times.

Iron Oxide Nanoparticles: An Alternative for Positive Contrast in Magnetic Resonance Imaging

Iron oxide nanoparticles have been extensively utilised as negative (T2) contrast agents in magnetic resonance imaging. In the past few years, researchers have also exploited their application as positive (T1) contrast agents to overcome the limitation of traditional Gd3+ contrast agents. To provide T1 contrast, these particles must present certain physicochemical properties with control over the size, morphology and surface of the particles. In this review, we summarise the reported T1 iron oxide nanoparticles and critically revise their properties, synthetic protocols and application, not only in MRI but also in multimodal imaging. In addition, we briefly summarise the most important nanoparticulate Gd and Mn agents to evaluate whether T1 iron oxide nanoparticles can reach Gd/Mn contrast capabilities.

Surface modifications at the oxide/water interface: Implications for Cu binding, solution chemistry and chemical stability of iron oxide nanoparticles

The oxidation of magnetite into maghemite and its coating by natural organic constituents are common changes that affect the reactivity of iron oxide nanoparticles (IONP) in aqueous environments. Certain ubiquitous compounds such as humic acids (HA) and phosphatidylcholine (PC), displaying a high affinity for both copper (Cu) and IONP, could play a critical role in the interactions involved between both compounds. The adsorption of Cu onto four different IONP was studied: magnetite nanoparticles (magnNP), maghemite NP (maghNP), HA- and PC-coated magnetite NP (HA-magnNP and PC-magnNP, respectively). According to the results, the percentage of adsorbed Cu increases with increasing pH, irrespective of the IONP. Thus, protonation/deprotonation reactions are likely involved within Cu adsorption mechanism. Contrary to the other studied IONP, HA-magnNP favor Cu adsorption at most of the pH tested including acidic pH (pH = 3), suggesting that part of the active surface sites for Cu²⁺ were not grabbed by protons. The Freundlich adsorption isotherm of HA-magnNP provides the highest sorption constant K_F (bonding energy) and n value which supports a heterogeneous sorption process. The heterogeneous adsorption between HA-magnNP and Cu²⁺ can be explained by both the diversity of the binding sites HA procured and the formation of multidendate complexes between Cu²⁺ and some of the HA functional groups. Such favorable adsorption process was neither observed on PC-coated-magnNP nor on maghNP, whose behaviors were comparable to that of magnNP. On another hand, HA and PC coatings considerably reduced iron (Fe) dissolution from magnNP as compared with magnNP. It was suggested that HA and PC coatings either provided efficient shield against Fe leaching or fostered dissolved Fe re-adsorption onto the functional groups at the coated magnNP surfaces. Thus, this study can help to better understand the complex interfacial reactions between cations-organic matter-colloidal surfaces which are relevant in environmental and agricultural contexts. This work showed that magnetite NP properties can be affected by surface modifications, which drive NP chemical stability and Cu adsorption, thereby affecting the global water chemistry.

Soy Lecithin-Derived Liposomal Delivery Systems: Surface Modification and Current Applications

The development of natural phospholipids for nanostructured drug delivery systems has attracted much attention in the past decades. Lecithin that was derived from naturally occurring in soybeans (SL) has introduced some auspicious accomplishments to the drug carrying aspect, like effectual encapsulation, controlled release, and successful delivery of the curative factors to intracellular regions in which they procure these properties from their flexible physicochemical and biophysical properties, such as large aqueous center and biocompatible lipid, self-assembly, tunable properties, and high loading capacity. Despite the almost perfect properties as a drug carrier, liposome is known to be quite quickly eliminated from the body systems. The surface modification of liposomes has been investigated in many studies to overcome this drawback. In this review, we intensively discussed the surface-modified liposomes that enhancing the targeting, cellular uptake, and therapeutic response. Moreover, the recent applications of soy lecithin-derived liposome, focusing on cancer treatment, brain targeting, and vaccinology, are also summarized.

An 89Zr-HDL PET Tracer Monitors Response to a CSF1R Inhibitor

The immune function within the tumor microenvironment has become a prominent therapeutic target, with tumor-associated macrophages (TAMs) playing a critical role in immune suppression. We propose an ⁸⁹Zr-labeled high-density lipoprotein (⁸⁹Zr-HDL) nanotracer as a means of monitoring response to immunotherapy. Methods: Female MMTV-PyMT mice were treated with pexidartinib, a colony-stimulating factor 1 receptor (CSF1R) inhibitor, to reduce TAM density. The accumulation of ⁸⁹Zr-HDL within the tumor was assessed using PET/CT imaging and autoradiography, whereas TAM burden was determined using immunofluorescence. Results: A significant reduction in ⁸⁹Zr-HDL accumulation was observed in PET/CT images, with 2.9% ± 0.3% and 3.7% ± 0.2% injected dose/g for the pexidartinib- and vehicle-treated mice, respectively. This reduction was corroborated ex vivo and correlated with decreased TAM density. Conclusion: These results support the potential use of ⁸⁹Zr-HDL nanoparticles as a PET tracer to quickly monitor the response to CSF1R inhibitors and other therapeutic strategies targeting TAMs.

Preparation and Characterization of a New Low Refractive Index Ferrofluid

In this research, a new low refractive index ferrofluid is proposed by coating magnetic nanoparticles with a layer of silver, applying the method of modified chemical co-precipitation. This preparation method is green and environmentally friendly without toxic gases being released. Coated nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and vibration sample magnetometery (VSM). These characterizations show that the silver nanoparticles grow on the surface of magnetic nanoparticles in this new ferrofluid. The hysteresis loop of this new ferrofluid demonstrates that it maintains superparamagnetic properties. A new method of refractive index measurement is applied in this research by employing a long-period grating (LPG) optical fiber sensor. The change value in the refractive index per unit concentration reduces by 16.46% compared to the conventional ferrofluid.

Biodistribution of gadolinium- and near infrared-labeled human umbilical cord mesenchymal stromal cell-derived exosomes in tumor bearing mice

We speculate that exosomes derived from human umbilical cord mesenchymal stromal cells (HUC-MSCs) will accumulate within tumors and have the potential for both tumor location or drug delivery.

Methods: To determine proof of concept, HUC-MSC exosomes were labeled with an MRI contrast agent, gadolinium, or a near infrared dye. Exosome accumulation within ectopic osteosarcoma tumor-bearing mice was determined by 14.1 T MRI or bioimaging over 24-48 h after injection. In vitro studies examine the accumulation and physiological effect of exosomes on human and mouse osteosarcoma cell lines by MTT assay, confocal microscopy, and flow cytometry.

Results: Systemic HUC-MSC exosomes accumulated continuously in tumor over a 24-48 h post-injection period. In contrast, synthetic lipid nanoparticles accumulate in tumor only for the first 3 h post-injection.

Conclusion: These results suggest that HUC-MSCs exosomes accumulate within human or mouse osteosarcoma cells in vitro and in vivo over a 24 to 48 h after infusion.

Listening for the therapeutic window: Advances in drug delivery utilizing photoacoustic imaging

The preclinical landscape of photoacoustic imaging has experienced tremendous growth in the past decade. This non-invasive imaging modality augments the spatiotemporal capabilities of ultrasound with optical contrast. While it has principally been investigated for diagnostic applications, many recent reports have described theranostic delivery systems and drug monitoring strategies using photoacoustics. Here, we provide an overview of the progress to date while highlighting work in three specific areas: theranostic nanoparticles, real-time drug monitoring, and stem cell ("living drug") tracking. Additionally, we discuss the challenges that remain to be addressed in this burgeoning field.

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

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

Molecular Imaging of the Heart

Multimodality cardiovascular imaging is routinely used to assess cardiac function, structure, and physiological parameters to facilitate the diagnosis, characterization, and phenotyping of numerous cardiovascular diseases (CVD), as well as allows for risk stratification and guidance in medical therapy decision-making. Although useful, these imaging strategies are unable to assess the underlying cellular and molecular processes that modulate pathophysiological changes. Over the last decade, there have been great advancements in imaging instrumentation and technology that have been paralleled by breakthroughs in probe development and image analysis. These advancements have been merged with discoveries in cellular/molecular cardiovascular biology to burgeon the field of cardiovascular molecular imaging. Cardiovascular molecular imaging aims to noninvasively detect and characterize underlying disease processes to facilitate early diagnosis, improve prognostication, and guide targeted therapy across the continuum of CVD. The most-widely used approaches for preclinical and clinical molecular imaging include radiotracers that allow for high-sensitivity in vivo detection and quantification of molecular processes with single photon emission computed tomography and positron emission tomography. This review will describe multimodality molecular imaging instrumentation along with established and novel molecular imaging targets and probes. We will highlight how molecular imaging has provided valuable insights in determining the underlying fundamental biology of a wide variety of CVDs, including: myocardial infarction, cardiac arrhythmias, and nonischemic and ischemic heart failure with reduced and preserved ejection fraction. In addition, the potential of molecular imaging to assist in the characterization and risk stratification of systemic diseases, such as amyloidosis and sarcoidosis will be discussed. © 2019 American Physiological Society. Compr Physiol 9:477-533, 2019.

[99mTc-HYNIC-N-dodecylamide]: a new hydrophobic tracer for labelling reconstituted high-density lipoproteins (rHDL) for radioimaging

Despite the widespread use of nanotechnology in radio-imaging applications, lipoprotein based delivery systems have received only limited attention so far. These studies involve the synthesis of a novel hydrophobic radio-imaging tracer consisting of a hydrazinonicotinic acid (HYNIC)-N-dodecylamide and 99mTc conjugate that can be encapsulated into rHDL nanoparticles (NPs). These rHDL NPs can selectively target the Scavenger Receptor type B1 (SR-B1) that is overexpressed on most cancer cells due to excess demand for cholesterol for membrane biogenesis and thus can target tumors in vivo. We provide details of the tracer synthesis, characterization of the rHDL/tracer complex, in vitro uptake, stability studies and in vivo application of this new radio-imaging approach.

Optimization of Phase-Change Contrast Agents for Targeting MDA-MB-231 Breast Cancer Cells

Breast cancer remains a leading cause of death for women throughout the world. Recent advances in medical imaging technologies and tumor targeting agents signify vast potential for progress toward improved management of this global problem. Phase-change contrast agents (PCCAs) are dynamic imaging agents with practical applications in both the research and clinical settings. PCCAs possess characteristics that allow for cellular uptake where they can be converted from liquid-phase PCCAs to gaseous microbubbles via ultrasound energy. Previously, we reported successful internalization of folate-targeted PCCAs in MDA-MB-231 breast cancer cells followed by ultrasound-mediated activation to produce internalized microbubbles. This study examines the binding, internalization and activation of folate-receptor targeted PCCAs in MDA-MB-231 breast cancer cells as a function of gaseous core compositions, incubation time and ultrasound exposure period. In vitro results indicate that internalization and ultrasound-mediated activation of PCCAs were significantly greater using a 50:50 mixture of decafluorobutane:dodecafluoropentane compared with other core compositions: 50:50 octafluoropropane:decafluorobutane (p < 0.0001), decafluorobutane (p < 0.04) and dodecafluoropentane (p < 0.0001). Furthermore, it was found that PCCAs composed of perfluorocarbons with higher boiling points responded with greater activation efficiency when exposed to 12 s of ultrasound exposure as opposed to 4 s of ultrasound exposure. When evaluating different incubation times, it was found that incubating the PCCAs with breast cancer cells for 60 min did not produce significantly greater internalization and activation compared with incubation for 10 min; this was concluded after comparing the number of microbubbles present per cell before ultrasound versus post-ultrasound, and finding a ratio of intracellular microbubbles post-ultrasound/pre-ultrasound, 3.46 versus 3.14, respectively. The data collected in this study helps illustrate further optimization of folate-receptor targeted PCCAs for breast cancer targeting and imaging.

Dual integrin αvβ 3 and NRP-1-Targeting Paramagnetic Liposome for Tumor Early Detection in Magnetic Resonance Imaging

Enhanced MRI (magnetic resonance imaging) plays a vital role in the early detection of tumor but with low specificity. Molecular imaging of angiogenesis could efficiently deliver contrast agents to the tumor site by specific targeted carriers. We designed and synthesized dual-targeted paramagnetic liposomes functionalized with two angiogenesis-targeting ligands, the αVβ3 integrin-specific RGD (Arg-Gly-Asp) and the neuropilin-1 (NRP-1) receptor-specific ATWLPPR (Ala-Thr-Trp-Leu-Pro-Pro-Arg) (A7R). These liposomes were proved to be in the nanoparticle range and demonstrated to effectively encapsulate paramagnetic MRI contrast agents Gd-DTPA (gadolinium-diethylenetriamine pentaacetic acid). T1 relaxivity of various liposome formulations was lower than pure Gd-DTPA but with no statistically significant difference. In vitro cellular uptake and competitive inhibition assay showed the higher binding affinity of dual-targeted liposomes to HUVECs (human umbilical vein endothelial cells) and A549 cells compared with pure Gd-DTPA, non-targeted, and single-targeted liposomes, which was proved to be mediated by the binding of RGD/ανβ3-integrin and A7R/NRP1. For MR imaging of mice bearing A549 cells in vivo, dual-targeted liposomes reached the highest SER (signal enhancement rate) value with a significant difference at all experimental time points. It was about threefold increase compared to pure Gd-DTPA and non-targeted liposomes and was 1.5-fold of single-targeted liposomes at 2 h post injection. The SER was lowered gradually and decreased only by 40% of the peak value in 6 h. Dual-targeted liposomes were likely to exert a synergistic effect and the specificity of delivering Gd-DTPA to the tumor site. Therefore, dual-ανβ3-integrin-NRP1-targeting paramagnetic liposome with a RGD-ATWLPPR heterodimeric peptide might be a potent system for molecular imaging of tumor.

Interaction of Huntingtin Exon-1 Peptides with Lipid-Based Micellar Nanoparticles Probed by Solution NMR and Q-Band Pulsed EPR

Lipid-based micellar nanoparticles promote aggregation of huntingtin exon-1 peptides. Here we characterize the interaction of two such peptides, htt^NTQ ₇ and htt^NTQ ₁₀ comprising the N-terminal amphiphilic domain of huntingtin followed by 7 and 10 glutamine repeats, respectively, with 8 nm lipid micelles using NMR chemical exchange saturation transfer (CEST), circular dichroism and pulsed Q-band EPR. Exchange between free and micelle-bound htt^NTQ  _n peptides occurs on the millisecond time scale with a K_D ∼ 0.5-1 mM. Upon binding micelles, residues 1-15 adopt a helical conformation. Oxidation of Met⁷ to a sulfoxide reduces the binding affinity for micelles ∼3-4-fold and increases the length of the helix by a further two residues. A structure of the bound monomer unit is calculated from the backbone chemical shifts of the micelle-bound state obtained from CEST. Pulsed Q-band EPR shows that a monomer-dimer equilibrium exists on the surface of the micelles and that the two helices of the dimer adopt a parallel orientation, thereby bringing two disordered polyQ tails into close proximity which may promote aggregation upon dissociation from the micelle surface.

Shape-, size- and structure-controlled synthesis and biocompatibility of iron oxide nanoparticles for magnetic theranostics

In the past decade, iron oxide nanoparticles (IONPs) have attracted more and more attention for their excellent physicochemical properties and promising biomedical applications. In this review, we summarize and highlight recent progress in the design, synthesis, biocompatibility evaluation and magnetic theranostic applications of IONPs, with a special focus on cancer treatment. Firstly, we provide an overview of the controlling synthesis strategies for fabricating zero-, one- and three-dimensional IONPs with different shapes, sizes and structures. Then, the in vitro and in vivo biocompatibility evaluation and biotranslocation of IONPs are discussed in relation to their chemo-physical properties including particle size, surface properties, shape and structure. Finally, we also highlight significant achievements in magnetic theranostic applications including magnetic resonance imaging (MRI), magnetic hyperthermia and targeted drug delivery. This review provides a background on the controlled synthesis, biocompatibility evaluation and applications of IONPs as cancer theranostic agents and an overview of the most up-to-date developments in this area.

Engineering a pH-Sensitive Liposomal MRI Agent by Modification of a Bacterial Channel

MscL is a bacterial mechanosensitive channel that serves as a cellular emergency release valve, protecting the cell from lysis upon a drop in external osmolarity. The channel has an extremely large pore (30 Å) and can be purified and reconstituted into artificial membranes. Moreover, MscL is modified to open in response to alternative external stimuli including changes in pH. These properties suggest this channel's potential as a triggered "nanopore" for localized release of vesicular contents such as magnetic resonance imaging (MRI) contrast agents and drugs. Toward this end, several variants of pH-triggered MscL nanovalves are engineered. Stealth vesicles previously been shown to evade normal in vivo clearance and passively accumulate in inflamed and malignant tissues are reconstituted. These vesicles are loaded with 1,4,7,10-tetraazacyclododecane tetraacetic acid gadolinium complex (Gd-DOTA), an MRI contrast reagent, and the resulting nanodevices tested for their ability to release Gd-DOTA as evidenced by enhancement of the longitudinal relaxation rate (R₁ ) of the bulk water proton spins. Nanovalves that are responsive to physiological pH changes are identified, but differ in sensitivity and efficacy, thus giving an array of nanovalves that could potentially be useful in different settings. These triggered nanodevices may be useful in delivering both diagnostic and therapeutic agents.

Recent development of nanoparticles for molecular imaging

Molecular imaging enables us to non-invasively visualize cellular functions and biological processes in living subjects, allowing accurate diagnosis of diseases at early stages. For successful molecular imaging, a suitable contrast agent with high sensitivity is required. To date, various nanoparticles have been developed as contrast agents for medical imaging modalities. In comparison with conventional probes, nanoparticles offer several advantages, including controllable physical properties, facile surface modification and long circulation time. In addition, they can be integrated with various combinations for multimodal imaging and therapy. In this opinion piece, we highlight recent advances and future perspectives of nanomaterials for molecular imaging.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.

Microemulsion-made gadolinium carbonate hollow nanospheres showing magnetothermal heating and drug release

Gadolinium carbonate (Gd₂(CO₃)₃) hollow nanospheres and their suitability for drug transport and magnetothermally-induced drug release are presented. The hollow nanospheres are prepared via a microemulsion-based synthesis using tris(tetramethylcyclopentadienyl)gadolinium(iii) and CO₂ as the starting materials. Size, structure and composition of the as-prepared Gd₂(CO₃)₃ hollow nanospheres are comprehensively validated by several independent analytical methods (HRTEM, HAADF-STEM, DLS, EDXS, XRD, FT-IR, DTA-TG). Accordingly, they exhibit an outer diameter of 26 ± 4 nm, an inner cavity of 7 ± 2 nm, and a wall thickness of 9 ± 3 nm. As a conceptual study, the nanocontainer-functionality of the Gd₂(CO₃)₃ hollow nanospheres is validated upon filling with the anti-cancerogenic agent doxorubicin (DOX), which is straightforward via the microemulsion (ME) strategy. The resulting DOX@Gd₂(CO₃)₃ nanocontainers provide the option of multimodal imaging including optical and magnetic resonance imaging (OI, MRI) as well as magnetothermal heating and drug release. As a proof-of-concept, we could already prove the intrinsic DOX-based fluorescence, a low systemic toxicity according to in vitro studies as well as the magnetothermal effect and a magnetothermally-induced DOX release. In particular, the latter is new for Gd-containing nanoparticles and highly promising in view of theranostic nanocontainers and synergistic physical and chemical tumor treatment.

Targeted tumor MRI with gadobutrol-loaded anti-HER2 immunoliposomes

Background Immunoliposomes have been used to deliver MR contrast agents to cancer tissue by targeting tumor associated antigens, thus enabling the visualization of biological processes at the cellular level. Purpose To develop and evaluate the feasibility of specific HER2 targeted liposomal MR contrast agent. Material and Methods Gd-loaded anti-HER2 immunolipomes (Gd-ILs) and non-targeted PEGylated liposomes (Gd-NTLs) were prepared and characterized. Tumor bearing animals were randomized into three groups: Gd- ILs, Gd- NTLs and gadobutrol. Animals were imaged prior and 5, 15, 60, 120 and 180 min after i.v. injection of different contrast agents. The signal intensity enhancement percentage, signal- to- noise ratio and contrast- to -noise ratio was used to qualify tumor enhancement of different groups. After imaging, tumors were excised for histological examination. Results In vivo dynamic MR images, the specific targeted contrast agent bound to tumor tissue and result in a gradual and persisting enhancement for at least 3 hours in mice bearing tumor xenografts, reaching a maximum of 87.7% enhancement after 120 min post-injection. Gd-ILs demonstrated superior tumor enhancement over control non target contrast agent and gadobutrol in HER2 overexpressing tumors at 60, 120 and 180 min post- injection. The SNR and CNR of Gd-ILs in the tumors were significantly greater than that of Gd-NTLs at 60, 120, 180 min post- injection. Conclusion The results indicate the feasibility of Gd-ILs providing prolonged circulation, specific tumor enhancement and cancer cell recognition as targeted contrast agent.

Design of Novel Ophthalmic Formulation Containing Drug Nanoparticles and Its Usefulness as Anti-glaucoma Drugs

The ophthalmic application of drugs is the primary route of administration for the therapy of glaucoma; however, in traditional formulations, only small amounts of the administered drug penetrate the cornea to reach the desired intraocular tissue due to corneal barriers. Recently, nanoparticulate drug delivery is expected as a technology to overcome the difficulties in delivering drugs across biological barriers (improvement of bioavailability). In this study, we attempted to establish a new method for preparing solid drug nanoparticles by using a bead mill and various additives, and succeeded in preparing a high quality dispersion containing drug nanoparticles. For a more concrete example, a mean particle size of disulfiram (DSF) treated with bead mill is 183 nm. The corneal penetration and corneal residence time of DSF from the ophthalmic dispersion containing DSF nanoparticles were significantly higher than those from a 2-hydroxypropyl-β-cyclodextrin solution containing DSF (DSF solution). It is known that the administration of DSF has intraocular pressure (IOP)-reducing effects. The IOP-reducing effects of the ophthalmic dispersion containing DSF nanoparticles were significantly greater than those of the DSF solution in rabbits (the IOP was enhanced by placing the rabbits in a dark room for 5 h). In addition, the ophthalmic dispersion containing DSF nanoparticles is better tolerated by corneal epithelial cells than DSF solution. It is possible that dispersions containing DSF nanoparticles provide new possibilities for effectively treating glaucoma, and that ocular drug delivery systems using drug nanoparticles may expand their usage for therapy in the ophthalmologic field.

In vivo detection of cucurbit[6]uril, a hyperpolarized xenon contrast agent for a xenon magnetic resonance imaging biosensor

The Hyperpolarized gas Chemical Exchange Saturation Transfer (HyperCEST) Magnetic Resonance (MR) technique has the potential to increase the sensitivity of a hyperpolarized xenon-129 MRI contrast agent. Signal enhancement is accomplished by selectively depolarizing the xenon within a cage molecule which, upon exchange, reduces the signal in the dissolved phase pool. Herein we demonstrate the in vivo detection of the cucurbit[6]uril (CB6) contrast agent within the vasculature of a living rat. Our work may be used as a stepping stone towards using the HyperCEST technique as a molecular imaging modality.

Towards advanced paramagnetic nanoassemblies of highly ordered interior nanostructures as potential MRI contrast agents

A novel paramagnetic amphiphile designed to form nanoassemblies of highly ordered nanostructures was explored as an advanced MRI contrast agent.

Fluorescence-Magnetism Functional EuS Nanocrystals with Controllable Morphologies for Dual Bioimaging

Multiple functions incorporated in one single component material offer important applications in biosystems. Here we prepared a divalent state of rare earth EuS nanocrystals (NCs), which provides luminescent and magnetic properties, using both 1-Dodecanethiol (DT) and oleylamine (OLA) as reducing agents. The resultant EuS NCs exhibit controllable shapes, uniform size, and bright luminescence with a quantum yield as high as 3.5%. OLA as a surface ligand plays an important role in tunable morphologies, such as nanowires, nanorods, nanospheres et al. Another attractive nature of the EuS NCs is their paramagnetism at room temperature. In order to expand the biological applications, the resultant EuS NCs were modified with amphiphilic block copolymer F127 and transferred from oil to water phase. The excellent biocompatibility of EuS NCs is demonstrated as well as preservation of their luminescence and paramagnetic properties. The EuS NCs offer multifunction and great advantages of bright luminescence, paramagnetic, controllable morphologies, and good biocompatibility promising applications in the field of simultaneous magnetic resonance and fluorescence bioimaging.

Molecular Imaging of Brain Tumors Using Liposomal Contrast Agents and Nanoparticles

The first generation of cross-sectional brain imaging using computed tomography (CT), ultrasonography, and eventually MR imaging focused on determining structural or anatomic changes associated with brain disorders. The current state-of-the-art imaging, functional imaging, uses techniques such as CT and MR perfusion that allow determination of physiologic parameters in vivo. In parallel, tissue-based genomic, transcriptomic, and proteomic profiling of brain tumors has created several novel and exciting possibilities for molecular targeting of brain tumors. The next generation of imaging translates these molecular in vitro techniques to in vivo, noninvasive, targeted reconstruction of tumors and their microenvironments.