Towards new functional nanostructures for medical imaging

Nanoparticle enhanced optical biosensing technologies for Prostate Specific Antigen biomarker detection

Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process for PCa is primarily conducted with the help of a FDA approved biomarker known as Prostate Specific Antigen (PSA). The PSA-based screening is challenged with the inability to differentiate between the cancerous PSA and Benign Prostatic Hyperplasia (BPH), resulting in high rates of false-positives. Optical techniques such as optical absorbance, scattering, surface plasmon resonance (SPR), and fluorescence have been extensively employed for Cancer diagnostic applications. One of the most important diagnostic applications involves utilization of nanoparticles (NPs) for highly specific, sensitive, rapid, multiplexed, and high performance Cancer detection and quantification. The incorporation of NPs with these optical biosensing techniques allow realization of low cost, point-of-care, highly sensitive, and specific early cancer detection technologies, especially for PCa. In this work, the current state-of-the-art, challenges, and efforts made by the researchers for realization of low cost, point-of-care (POC), highly sensitive, and specific NP enhanced optical biosensing technologies for PCa detection using PSA biomarker are discussed and analyzed.

Polyelectrolyte Coatings Can Control Charged Fluorocarbon Nanodroplet Stability and Their Interaction with Macrophage Cells

Fluorocarbon nanodroplets, ∼100 to ∼400 nm in diameter, are of immense interest in a variety of medical applications including the imaging and therapy of cancer and inflammatory diseases. However, fluorocarbon molecules are both hydrophobic and lipophobic; therefore, it is challenging to synthesize fluorocarbon nanodroplets with the optimal stability and surface properties without the use of highly specialized surfactants. Here, we hypothesize that we can decouple the control of fluorocarbon nanodroplet size and stability from its surface properties. We use a simple, two-step procedure where standard, easily available anionic fluorosurfactants are used to first stabilize the fluorocarbon nanodroplets, followed by electrostatically attaching functionalized polyelectrolytes to the nanodroplet surfaces to independently control their surface properties. Herein, we demonstrate that PEGylated polyelectrolyte coatings can effectively alter the fluorocarbon nanodroplet surface properties to reduce coalescence and its uptake into phagocytic cells in comparison with non-PEGylated polyelectrolyte coatings and uncoated nanodroplets, as measured by flow cytometry and fluorescence microscopy. In this study, perfluorooctyl bromide (PFOB) was used as a representative fluorocarbon material, and PEGylated PFOB nanodroplets with diameters between 250 and 290 nm, depending on the poly(ethylene glycol) block length, were prepared. The PEGylated PFOB nanodroplets had superior size stability in comparison with uncoated and non-PEGylated polyelectrolyte nanodroplets in saline and within macrophage cells. Of significance, non-PEGylated nanodroplets were rapidly internalized by macrophage cells, whereas PEGylated nanodroplets were predominantly colocalized on the cell membrane. This suggests that the PEGylated-polyelectrolyte coating on the charged PFOB nanodroplets may afford adjustable shielding from cells of the reticuloendothelial system. This report shows that using the same fluorosurfactant as a base layer, modularly assembled PFOB nanodroplets tailored for a variety of end applications can be created by selecting different polyelectrolyte coatings depending on their unique requirements for stability and interaction with phagocytic cells.

Heterogeneous Nanostructures Fabricated via Binding Energy-Controlled Nanowelding

A novel concept for fabricating heterogeneous nanostructures based on different melting temperatures is developed. Au-Ag composite cross-structures are fabricated by nanowelding technologies. During the fabrication of Au-Ag composite cross-structures, Ag nanowires transform into ordered particles decorating the Au nanowire surfaces with an increase in the welding temperature because of the different melting temperatures of Au and Ag. To compare and explain the melting temperatures, the thicknesses of Au and Ag nanowires as parameters are analyzed. Scanning electron microscopy and focused ion beam imaging are used to observe the morphologies and cross sections of the fabricated samples. The evolution of 3D nanostructures is observed by atomic force microscopy, whereas the compositions and binding energies of the nanostructures are determined by X-ray diffraction and X-ray photoelectron spectroscopies. In addition, the atomic structures are analyzed by transmission electron microscopy, and the optical properties of the fabricated nanostructures are evaluated by spectrometry. Furthermore, color filter electrodes are fabricated, and their polarization properties are evaluated by sheet resistance measurements and observing the color and brightness of light-emitting diodes. The proposed method is suitable for application in various fields such as biosensors, optics, and medicine.

18F-Labeled perfluorocarbon droplets for positron emission tomography imaging

INTRODUCTION

Nanoscale perfluorocarbon (PFC) droplets have been used to create imaging agents and drug delivery vehicles. However, development and characterization of new formulations of PFC droplets are hindered because of the lack of simple methods for quantitative and sensitive assessment of whole body tissue distribution and pharmacokinetics of the droplets. To address this issue, a general-purpose method for radiolabeling the inner core of nanoscale perfluorocarbon droplets with a hydrophobic and lipophobic fluorine-18 compound was developed, so that positron emission tomography (PET) and quantitative biodistribution studies can be employed to evaluate PFC nanodroplets in vivo.

METHODS

A robust method to produce [¹⁸F]CF₃(CF₂)₇(CH₂)₃F from a tosylate precursor using [¹⁸F]F^- was developed. The product's effectiveness as a general label for different PFCs and its ability to distinguish the in vivo behavior of different PFC droplet formulations was evaluated using two types of PFC nanodroplets: fluorosurfactant-stabilized perfluorohexane (PFH) nanodroplets and lipid-stabilized perfluorooctylbromide (PFOB) nanodroplets. In vivo assessment of the ¹⁸F-labeled PFH and PFOB nanodroplets were conducted in normal mice following intravenous injection using small animal PET imaging and gamma counting of tissues and fluids.

RESULTS

[¹⁸F]CF₃(CF₂)₇(CH₂)₃F was produced in modest yield and was stable with respect to loss of fluoride in vitro. The labeled fluorocarbon was successfully integrated into PFH nanodroplets (~175 nm) and PFOB nanodroplets (~260 nm) without altering their mean sizes, size distributions, or surface charges compared to their non-radioactive analogues. No leakage of the radiolabel from the nanodroplets was detected after droplet formation in vitro. PET imaging and biodistribution data for the two droplet types tested showed significantly different tissue uptake and clearance patterns.

CONCLUSION

A convenient method for producing ¹⁸F-labeled PFC droplets was developed. The results highlight the potential utility of the strategy for pre-clinical evaluation of different PFC droplet formulations through direct PFC core labeling using a fluorinated radiolabel.

Size reduction of cosolvent-infused microbubbles to form acoustically responsive monodisperse perfluorocarbon nanodroplets

Perfluorocarbon (PFC) nanodroplet agents are exciting new biomaterials that can be remotely vapourized by ultrasound or light to change into micron-scale gas bubbles in situ. After PFC nanodroplet vapourization, the micron-scale gas bubble can interact strongly with ultrasound radiation, such that the bubbles can be used for cancer imaging and therapy. For these phase-change agents to be useful, however, PFC nanodroplets must be produced in the range of 100 to 400 nm in diameter with high size control and monodispersity, restrictions that remain a challenge. Here, we address this challenge by taking advantage of the size control offered by microfluidics, in combination with the size reduction provided by cosolvent-infused PFC bubbles through both condensation and cosolvent dissolution. In this approach, PFC bubbles with a high percentage of cosolvent (in this study, diethyl ether, DEE) are produced using microfluidics at a temperature above the boiling point. After synthesis, these bubbles become much smaller through both condensation of the gas into liquid droplets and from dissolution of the DEE into the continuous phase. This approach demonstrates that monodisperse, cosolvent-incorporated PFC bubbles can directly form monodisperse PFC nanodroplets a factor of 24 times smaller than the precursor bubbles. We also demonstrate that these nanoscale droplets can be converted to echogenic microbubbles after exposure to ultrasound, showing that these PFC nanodroplets are viable for the in situ production of ultrasound contrast agents. We show that this system can overcome the minimum droplet size limit of standard microfluidics, and is a powerful new tool for generating monodisperse, PFC phase-change ultrasound contrast agents for treating and imaging cancer.

Dendrimers for theranostic applications

Recently, there have been tremendous advances in the development of various nanotechnology-based platforms for diagnosis and therapy. These nanoplatforms, which include liposomes, micelles, polymers, and dendrimers, comprise highly integrated nanoparticles that provide multiple functions, such as targeting, imaging, and therapy. This review focuses on dendrimer-based nanocarriers that have recently been developed for ‘theranostics (or theragnosis)’, a combination of therapy and diagnostics. We discuss the in vitro and in vivo applications of these nanocarriers in strategies against diseases including cancer. We also explore the use of dendrimers as imaging agents for fluorescence imaging, magnetic resonance imaging, X-ray computed tomography, and nuclear medical imaging.

Direct incorporation of lipophilic nanoparticles into monodisperse perfluorocarbon nanodroplets via solvent dissolution from microfluidic-generated precursor microdroplets

Multifunctional medical agents based on imaging or therapy nanoparticles (NPs) incorporated into perfluorocarbon (PFC) droplets are promising new agents for cancer detection and treatment. For the first time, monodisperse PFC nanodroplets labeled with NPs have been produced. Lipophilic, as-synthesized, hydrocarbon-stabilized NPs are directly miscibilized into lipophobic PFCs using a removable cosolvent, diethyl ether (DEE), which eliminates the need of the typical time-consuming and expertise-specific NP surface modification steps previously required for NP incorporation into PFCs. This NP-DEE/PFC solution is then used to synthesize monodisperse, micrometer-scale, DEE-infused NP-PFC precursor droplets in water using microfluidics. After precursor microdroplet generation, the DEE cosolvent is removed by dissolution and evaporation, resulting in dramatically smaller, monodisperse, NP-labeled nanodroplets, with final droplet sizes far smaller than the minimum droplet size limit of the microfluidic system, and easily controlled by the amount of DEE mixed in the PFC phase prior to precursor droplet synthesis. Using this technique, unmodified lipophilic quantum dot (QD) NPs were integrated into monodisperse and PFC nanodroplets 165 times smaller in volume than the precursor microdroplets, with dimensions down to 470 nm. The final droplet sizes scaled with the PFC concentrations in the precursor microdroplets, and the QDs remain localized within the droplets after DEE is removed from the system. This method is robust and versatile, and it comprises a platform technology for other unmodified lipophilic NPs and molecules to be incorporated into different types of PFC droplets for the production of new NP-PFC hybrid agents for medical imaging and therapy applications.

Molecular imaging for theranostics in gastroenterology: one stone to kill two birds

Molecular imaging in gastroenterology has become more feasible with recent advances in imaging technology, molecular genetics, and next-generation biochemistry, in addition to advances in endoscopic imaging techniques including magnified high-resolution endoscopy, narrow band imaging or autofluorescence imaging, flexible spectral imaging color enhancement, and confocal laser endomicroscopy. These developments have the potential to serve as "red flag" techniques enabling the earlier and accurate detection of mucosal abnormalities (such as precancerous lesions) beyond biomarkers, virtual histology of detected lesions, and molecular targeted therapy-the strategy of "one stone to kill two or three birds"; however, more effort should be done to be "blue ocean" benefit. This review deals with the introduction of Raman spectroscopy endoscopy, imaging mass spectroscopy, and nanomolecule development for theranostics. Imaging of molecular pathological changes in cells/tissues/organs might open the "royal road" to either convincing diagnosis of diseases that otherwise would only be detected in the advanced stages or novel therapeutic methods targeted to personalized medicine.

Superparamagnetic iron oxide based nanoprobes for imaging and theranostics

The need to target, deliver and subsequently evaluate the efficacy of therapeutics in the treatment of a disease has provided added impetus in developing novel and highly efficient contrast agents. Superparamagnetic iron oxide nanoparticles (SPIONs) have offered tremendous potential in designing advanced magnetic resonance imaging (MRI) diagnostic agents, due to their unique physicochemical properties. There has been tremendous effort devoted in the recent past in developing synthetic methodologies through which their size, hydrodynamic radii, chemical composition and morphologies could be tailored at the nanoscale. This enables one to fine tune their magnetic behavior, and thus their MRI response. While novel synthetic strategies are being assembled for directing SPIONs to the diseased site as well as imparting them stealth and biocompatibility, it is also essential to evaluate their biological toxicological profiles. This review highlights recent advances that have been made in the synthesis of SPIONs, subsequent functionalization with desired entities, and a discussion on their use as MRI contrast agents in cardiovascular research.

Towards a nanoscale mammographic contrast agent: development of a modular pre-clinical dual optical/x-ray agent

Contrast-enhanced digital mammography (CEDM) can provide improved breast cancer detection and characterization compared to conventional mammography by imaging the effects of tumour angiogenesis. Current small-molecule contrast agents used for CEDM are limited by a short plasma half-life and rapid extravasation into tissue interstitial space. To address these limitations, nanoscale agents that can remain intravascular except at sites of tumour angiogenesis can be used. For CEDM, this agent must be both biocompatible and strongly attenuate mammographic energy x-rays. Nanoscale perfluorooctylbromide (PFOB) droplets have good x-ray attenuation and have been used in patients for other applications. However, the macroscopic scale of x-ray imaging (50-100 µm) is inadequate for direct verification that PFOB droplets localize at sites of breast tumour angiogenesis. For efficient pre-clinical optimization for CEDM, we integrated an optical marker into PFOB droplets for microscopic assessment (≪50 µm). To develop PFOB droplets as a new nanoscale mammographic contrast agent, PFOB droplets were labelled with fluorescent quantum dots (QDs). The droplets had mean diameters of 160 nm, fluoresced at 635 nm and attenuated x-ray spectra at 30.5 keV mean energy with a relative attenuation of 5.6 ± 0.3 Hounsfield units (HU) mg(-1) mL(-1) QD-PFOB. With the agent loaded into tissue phantoms, good correlation between x-ray attenuation and optical fluorescence was found (R(2) = 0.96), confirming co-localization of the QDs with PFOB for quantitative assessment using x-ray or optical methods. Furthermore, the QDs can be removed from the PFOB agent without affecting its x-ray attenuation or structural properties for expedited translation of optimized PFOB droplet formulations into patients.

Dendrimer nanoscaffolds for potential theranostics of prostate cancer with a focus on radiochemistry

Dendrimers are a class of structurally defined macromolecules featured with a central core, a low-density interior formed by repetitive branching units, and a high-density exterior terminated with surface functional groups. In contrast to their polymeric counterparts, dendrimers are nanosized and symmetrically shaped, which can be reproducibly synthesized on a large scale with monodispersity. These unique features have made dendrimers of increasing interest for drug delivery and other biomedical applications as nanoscaffold systems. Intended to address the potential use of dendrimers for the development of theranostic agents, which combines therapeutics and diagnostics in a single entity for personalized medicine, this review focuses on the reported methodologies of using dendrimer nanoscaffolds for targeted imaging and therapy of prostate cancer. Of particular interest, relevant chemistry strategies are discussed due to their important roles in the design and synthesis of diagnostic and therapeutic dendrimer-based nanoconjugates and potential theranostic agents, targeted or nontargeted. Given the developing status of nanoscaffolded theranostics, major challenges and potential hurdles are discussed along with the examples representing current advances.

CT/fluorescence dual-modal nanoemulsion platform for investigating atherosclerotic plaques

Macrophages have become widely recognized as a key target for atherosclerosis imaging, since they contribute significantly to the progression of atherosclerosis. Dual-modal imaging contrast agents with unique X-ray computed tomography (CT) and optical imaging capabilities have great potential in disease diagnosis because of complementary combination of the high spatial resolution of CT with the high sensitivity of optical imaging. Here, a kind of quantum dots (QDs)-iodinated oil nanoemulsion of 80 nm was developed as a CT/fluorescence dual-modal contrast agent. Hydrophobic QDs were embedded in iodinated oil, which subsequently dispersed in water to form the oil-in-water nanoemulsion. The morphology and hydrodynamic size of the nanoemulsion were characterized, CT values and fluorescence properties were detected. Its cytotoxicity and affinity to three different cells were determined in vitro by MTT assay. In vitro Micro-CT and confocal microscopy cell imaging ability of the nanoemulsion were confirmed by co-incubating with murine macrophage cells and human liver cells. Then in vivo accumulation of this nanoemulsion in macrophages in atherosclerotic rabbits was investigated with clinic CT and fluorescence imaging. The results not only indicated the nanoemulsion could be served as a dual-modal contrast agent, but revealed it could specifically target to macrophages and visualize atherosclerotic plaques.

Intracellular growth of nanoscale perfluorocarbon droplets for enhanced ultrasound-induced phase-change conversion

Perfluorocarbon (PFC) nanodroplets (NDs) have been proposed as phase-change contrast agents for ultrasound imaging. Since the ultrasound energy required to convert PFC droplets to microbubbles is inversely related to size, the conversion of PFC NDs at clinically-relevant pressures is challenging. We propose that if PFC NDs can accumulate in a close-packed configuration and grow in size in situ, phase-change conversion can occur at lower ultrasound pressures compared with isolated NDs. In this article, we show that PFC NDs can be designed to grow in size after loading in cells, from 0.26 ± 0.09 μm to 1.7 ± 0.6 μm after 2 h. This growth allowed for a substantial decrease in the ultrasound conversion threshold (to 1.4 MPa and 4.8 MPa at 1 MHz and 18 MHz, respectively), whereas non-coalesced NDs in cells and NDs alone were not converted up to the maximum applied pressure (2.1 MPa and 6.3 MPa at 1 MHz and 18 MHz, respectively). These results indicate that PFC NDs with conversion pressures too high for diagnostically feasible conversion can be used as phase-change agents if they can be induced to grow in size in situ.

Monodisperse, submicrometer droplets via condensation of microfluidic-generated gas bubbles

Microfluidics (MFs) can produce monodisperse droplets with precise size control. However, the synthesis of monodisperse droplets much smaller than the minimum feature size of the microfluidic device (MFD) remains challenging, thus limiting the production of submicrometer droplets. To overcome the minimum micrometer-scale droplet sizes that can be generated using typical MFDs, the droplet material is heated above its boiling point (bp), and then MFs is used to produce monodisperse micrometer-scale bubbles (MBs) that are easily formed in the size regime where standard MFDs have excellent size control. After MBs are formed, they are cooled, condensing into dramatically smaller droplets that are beyond the size limit achievable using the original MFD, with a size decrease corresponding to the density difference between the gas and liquid phases of the droplet material. Herein, it is shown experimentally that monodisperse, submicrometer droplets of predictable sizes can be condensed from a monodisperse population of MBs as generated by MFs. Using perfluoropentane (PFP) as a representative solvent due to its low bp (29.2 °C), it is demonstrated that monodisperse PFP MBs can be produced at MFD temperatures >3.6 °C above the bp of PFP over a wide range of sizes (i.e., diameters from 2 to 200 μm). Independent of initial size, the generated MBs shrink rapidly in size from about 3 to 0 °C above the bp of PFP, corresponding to a phase change from gas to liquid, after which they shrink more slowly to form fully condensed droplets with diameters 5.0 ± 0.1 times smaller than the initial size of the MBs, even in the submicrometer size regime. This new method is versatile and flexible, and may be applied to any type of low-bp solvent for the manufacture of different submicrometer droplets for which precisely controlled dimensions are required.

Zr- and Hf-based nanoscale metal-organic frameworks as contrast agents for computed tomography

Nanoscale metal-organic frameworks (NMOFs) of the UiO-66 structure containing high Zr (37 wt%) and Hf (57 wt%) content were synthesized and characterized, and their potential as contrast agents for X-ray computed tomography (CT) imaging was evaluated. Hf-NMOFs of different sizes were coated with silica and poly(ethylene glycol) (PEG) to enhance biocompatibility, and were used for in vivo CT imaging of mice, showing increased attenuation in the liver and spleen.

Silica-coated quantum dots for optical evaluation of perfluorocarbon droplet interactions with cells

There has been recent interest in developing new, targeted, perfluorocarbon (PFC) droplet-based contrast agents for medical imaging (e.g., magnetic resonance imaging, X-ray/computed tomography, and ultrasound imaging). However, due to the large number of potential PFCs and droplet stabilization strategies available, it is challenging to determine in advance the PFC droplet formulation that will result in the optimal in vivo behavior and imaging performance required for clinical success. We propose that the integration of fluorescent quantum dots (QDs) into new PFC droplet agents can help to rapidly screen new PFC-based candidate agents for biological compatibility early in their development. QD labels can allow the interaction of PFC droplets with single cells to be assessed at high sensitivity and resolution using optical methods in vitro, complementing the deeper depth penetration but lower resolution provided by PFC droplet imaging using in vivo medical imaging systems. In this work, we introduce a simple and robust method to miscibilize silica-coated nanoparticles into hydrophobic and lipophobic PFCs through fluorination of the silica surface via a hydrolysis-condensation reaction with 1H,1H,2H,2H-perfluorodecyltriethoxysilane. Using CdSe/ZnS core/shell QDs, we show that nanoscale, QD-labeled PFC droplets can be easily formed, with similar sizes and surface charges as unlabeled PFC droplets. The QD label can be used to determine the PFC droplet uptake into cells in vitro by fluorescence microscopy and flow cytometry, and can be used to validate the fate of PFC droplets in vivo in small animals via fluorescence microscopy of histological tissue sections. This is demonstrated in macrophage and cancer cells, and in rabbits, respectively. This work reveals the potential of using QD labels for rapid, preclinical, optical assessment of different PFC droplet formulations for their future use in patients.

Cancer cell invasion: treatment and monitoring opportunities in nanomedicine

Cell invasion is an intrinsic cellular pathway whereby cells respond to extracellular stimuli to migrate through and modulate the structure of their extracellular matrix (ECM) in order to develop, repair, and protect the body's tissues. In cancer cells this process can become aberrantly regulated and lead to cancer metastasis. This cellular pathway contributes to the vast majority of cancer related fatalities, and therefore has been identified as a critical therapeutic target. Researchers have identified numerous potential molecular therapeutic targets of cancer cell invasion, yet delivery of therapies remains a major hurdle. Nanomedicine is a rapidly emerging technology which may offer a potential solution for tackling cancer metastasis by improving the specificity and potency of therapeutics delivered to invasive cancer cells. In this review we examine the biology of cancer cell invasion, its role in cancer progression and metastasis, molecular targets of cell invasion, and therapeutic inhibitors of cell invasion. We then discuss how the field of nanomedicine can be applied to monitor and treat cancer cell invasion. We aim to provide a perspective on how the advances in cancer biology and the field of nanomedicine can be combined to offer new solutions for treating cancer metastasis.

Optimization of gadolinium-based MRI contrast agents for high magnetic-field applications

The search for higher spatial resolution and better sensitivity stimulates the development of high-field (3 T) and ultrahigh field (>3 T) MRI scanners. Gadolinium-based MRI contrast agents, commercial ones used in clinics, as well as recently developed more efficient ones, become less and less effective as the magnetic field is increased above 3 T and, therefore, special contrast agents for ultrahigh-field MRI have to be developed. As the relaxivity, defined as relaxation enhancement per Gd-ion, is rather limited, marked boosts in performance can only be achieved by creating systems transporting many paramagnetic centers to the desired site. To obtain maximum efficiency gadolinium chelates with more than one water molecule in the first coordination sphere must be used. The rotational correlation time should be in the range of 0.5-1 ns and the residence time of first sphere water molecules should be short (<10 ns).

Luminescence targeting and imaging using a nanoscale generation 3 dendrimer in an in vivo colorectal metastatic rat model

Surgery is currently the best approach for treating either primary or metastatic hepatic malignancies. Because only 20% of hepatic cancers are operable in patients, several types of regional therapy (RT) are emerging as alternate treatment modalities. However, RTs can have their own limitations at controlling tumor growth or may lack the ability to detect such metastases. Additional strategies can be implemented to enhance their efficacy. An animal model of hepatic metastases coupled with a gastroduodenal artery (GDA) cannulation technique may provide a site to apply such therapies. In our study, splenic injections were performed with CC531 adenocarcinoma cells, which generated metastatic hepatic tumors in WAG/RijHsd rats. Cannulation of GDA was achieved via a polyethylene catheter. Infusion of generation 3 polyamidoamine 4-amino-1,8-naphthalimide dendrimer containing 8 europium ions (Eu-G3P4A18N) via the GDA resulted in luminescence of the hepatic metastatic nodules. Imaging of the metastatic hepatic nodules was obtained with the help of a cooled charge coupled device (CCD) camera.

FROM THE CLINICAL EDITOR

Hepatic malignancies represent a major therapeutic challenge, despite the available surgical and oncologic treatment modalities. In this paper, an animal model of hepatic adenocarcinoma is used in demonstrating successful targeting of spleen metastases with generation 3 polyamidoamine 4-amino-1,8-naphthalimide dendrimer containing 8 europium ions (Eu-G3P4A18N) for luminescence imaging.

Design and fabrication of magnetic nanoparticles for targeted drug delivery and imaging

Magnetic nanoparticles (MNPs) represent a class of non-invasive imaging agents that have been developed for magnetic resonance (MR) imaging. These MNPs have traditionally been used for disease imaging via passive targeting, but recent advances have opened the door to cellular-specific targeting, drug delivery, and multi-modal imaging by these nanoparticles. As more elaborate MNPs are envisioned, adherence to proper design criteria (e.g. size, coating, molecular functionalization) becomes even more essential. This review summarizes the design parameters that affect MNP performance in vivo, including the physicochemical properties and nanoparticle surface modifications, such as MNP coating and targeting ligand functionalizations that can enhance MNP management of biological barriers. A careful review of the chemistries used to modify the surfaces of MNPs is also given, with attention paid to optimizing the activity of bound ligands while maintaining favorable physicochemical properties.