Multifunctional pH-sensitive magnetic nanoparticles for simultaneous imaging, sensing and targeted intracellular anticancer drug delivery

A novel multifunctional magnetic nanocarrier was fabricated for synchronous cancer therapy and sensing. The nanocarrier, programed to display a response to environmental stimuli (pH value), was synthesized by coupling doxorubicin (DOX) to adipic dihydrazide-grafted gum arabic modified magnetic nanoparticles (ADH-GAMNP) via the hydrolytically degradable pH-sensitive hydrazone bond. The resultant nanocarrier, DOX-ADH-GAMNP, had a mean diameter of 13.8 nm and the amount of DOX coupled was about 6.52 mg g(-1). Also, it exhibited pH triggered release of DOX in an acidic environment (pH 5.0) but was relatively stable at physiological pH (pH 7.4). Furthermore, both GAMNP and DOX were found to possess fluorescence properties when excited in the near-infrared region due to the two-photon absorption mechanism. The coupling of DOX to GAMNP resulted in a reversible self-quenching of fluorescence through the fluorescence resonant energy transfer (FRET) between the donor GAMNP and acceptor DOX. The release of DOX from DOX-ADH-GAMNP when exposed to acidic media indicated the recovery of fluorescence from both GAMNP and DOX. The change in the fluorescence intensity of DOX-ADH-GAMNP on the release of DOX can act as a potential sensor to sense the delivery of the drug. The analysis of zeta potential and plasmon absorbance in different pH conditions also confirmed the pH sensitivity of the product. This multifunctional nanocarrier is a significant breakthrough in developing a drug delivery vehicle that combines drug targeting as well as sensing and therapy at the same time.

Magnetic resonance methods and applications in pharmaceutical research

This review presents an overview of some recent magnetic resonance (MR) techniques for pharmaceutical research. MR is noninvasive, and does not expose subjects to ionizing radiation. Some methods that have been used in pharmaceutical research MR include magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) methods, among them, diffusion-weighted MRI, perfusion-weighted MRI, functional MRI, molecular imaging and contrast-enhance MRI. Some applications of MR in pharmaceutical research include MR in metabonomics, in vivo MRS, studies in cerebral ischemia and infarction, degenerative joint diseases, oncology, cardiovascular disorders, respiratory diseases and skin diseases. Some of these techniques, such as cardiac and joint imaging, or brain fMRI are standard, and are providing relevant data routinely. Skin MR and hyperpolarized gas lung MRI are still experimental. In conclusion, considering the importance of finding and characterizing biomarkers for improved drug evaluation, it can be expected that the use of MR techniques in pharmaceutical research is going to increase in the near future.

Magnetic colloids as drug vehicles

This review article is a description of the present status of magnetic drug delivery systems (DDS). These are colloidal dispersions of composite nanoparticles consisting of a (polymeric or inorganic) biocompatible matrix and magnetic units, and designed to load and release therapeutic drugs. The matrix, together perhaps with adsorbed polymers or polyelectrolytes, provides the DDS with additional colloidal stability and eventually control of the immune response, and the magnetic inclusions have the goal of providing magnetic guidance. The techniques used in the production of the particles are described. The large surface/volume ratio of the particles brings about a superlative importance of the interface aspects, which are depicted in some detail. Attention is also paid to the possibilities that magnetic DDS offer to be guided by magnetic fields, and to their fate upon entering in contact with the blood proteins and the tumor cells. A description of in vitro and in vivo biodistribution experiments helps in this description. The number of animal experiments performed using magnetic DDS is rather large, but results in humans are far from being sufficient in number, something easily understood. The hopes for improvement and the challenges that must be overcome are described in the closing section.

Magnetic nanoparticles in MR imaging and drug delivery

Magnetic nanoparticles (MNPs) possess unique magnetic properties and the ability to function at the cellular and molecular level of biological interactions making them an attractive platform as contrast agents for magnetic resonance imaging (MRI) and as carriers for drug delivery. Recent advances in nanotechnology have improved the ability to specifically tailor the features and properties of MNPs for these biomedical applications. To better address specific clinical needs, MNPs with higher magnetic moments, non-fouling surfaces, and increased functionalities are now being developed for applications in the detection, diagnosis, and treatment of malignant tumors, cardiovascular disease, and neurological disease. Through the incorporation of highly specific targeting agents and other functional ligands, such as fluorophores and permeation enhancers, the applicability and efficacy of these MNPs have greatly increased. This review provides a background on applications of MNPs as MR imaging contrast agents and as carriers for drug delivery and an overview of the recent developments in this area of research.

Chitosan-coated magnetic nanoparticles as carriers of 5-fluorouracil: preparation, characterization and cytotoxicity studies

The chitosan-coated magnetic nanoparticles (CS MNPs) were prepared as carriers of 5-Fluorouracil (CS-5-Fu MNPs) through a reverse microemulsion method. The characteristics of CS-5-Fu MNPs were determined by using transmission electron microscopy (TEM), FTIR spectroscopy and vibrating-sampling magnetometry (VSM). It was found that the synthesized CS-5-Fu MNPs were spherical in shape with an average size of 100+/-20 nm, low aggregation and good magnetic responsivity. Meanwhile, the drug content and encapsulation rate of the nanoparticles was 16-23% and 60-92%, respectively. These CS-5-Fu MNPs also demonstrated sustained release of 5-Fu at 37 degrees C in different buffer solutions. The cytotoxicity of CS-5-Fu MNPs towards K562 cancer cells was investigated. The result showed that CS-5-Fu MNPs retained significant antitumor activities. Additionally, it was observed that the FITC-labeled CS-5-Fu MNPs could effectively enter into the SPCA-1 cancer cells and induced cell apoptosis.

Controlled aggregation of superparamagnetic iron oxide nanoparticles for the development of molecular magnetic resonance imaging probes

A method for synthesizing superparamagnetic iron oxide (SPIO) multi-nanoparticle aggregates as molecular magnetic resonance imaging (MRI) contrast agents is described. The approach utilizes organic acid/base interactions in the colloid to induce highly controllable nanoparticle aggregation. Monodisperse aggregates with diameters as large as 100 nm are synthesized by manipulating the interfacial surface chemistry of the SPIO nanoparticles in tetrahydrofuran solvent. Subsequent phospholipid micelle encapsulation yields micellar multi-SPIO (mmSPIO) aggregates with enhanced T(2) relaxivity (368.0 s(-1) mmol(-1) Fe) as compared to micellar single particle SPIO (302.0 s(-1) mmol(-1) Fe). mmSPIO conjugated to anti-CA125 monoclonal antibodies were incubated with ovarian carcinoma cell lines to demonstrate targeted in vitro molecular MRI, resulting in a 66% shortening in T(2) time for CA125 positive NIH:OVCAR-3 cells and a less than 3% change in T(2) time for CA125 negative SK-OV-3 cells. The controllable aggregation of mmSPIO shows potential for the development of molecular MRI contrast agents with optimal sizes for specific diagnostic imaging applications.

A stimulus-responsive magnetic nanoparticle drug carrier: magnetite encapsulated by chitosan-grafted-copolymer

We describe a magnetic nanoparticle drug carrier for controlled drug release that responds to the change in external temperature or pH, with characteristics of longer circulation time and reduced side effects. The novel nanocarrier is characterized by a functionalized magnetite (Fe(3)O(4)) core that is conjugated with drug via acid-labile hydrazone-bond and encapsulated by the thermosensitive smart polymer, chitosan-g-poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [chitosan-g-poly(NIPAAm-co-DMAAm)]. The chitosan-g-poly(NIPAAm-co-DMAAm) smart polymer exhibits a lower critical solution temperature (LCST) of approximately 38 degrees C, signifying phase transition behavior of the smart polymer and enabling its use for triggering on-off mechanisms. The drug release response was appreciably low at a temperature less than the LCST as compared with a temperature above the LCST. In each case, there was an initial rapid drug release, followed by a controlled released in the second stage, especially in a mild acidic buffer solution of pH 5.3. We believe that the drug release occurs via a collapse of the encapsulated thermosensitive polymer and cleavage of the acid-labile hydrazone linkage.

Targeted delivery of nanoparticles for the treatment of lung diseases

Targeted delivery of drug molecules to organs or special sites is one of the most challenging research areas in pharmaceutical sciences. By developing colloidal delivery systems such as liposomes, micelles and nanoparticles a new frontier was opened for improving drug delivery. Nanoparticles with their special characteristics such as small particle size, large surface area and the capability of changing their surface properties have numerous advantages compared with other delivery systems. Targeted nanoparticle delivery to the lungs is an emerging area of interest. This article reviews research performed over the last decades on the application of nanoparticles administered via different routes of administration for treatment or diagnostic purposes. Nanotoxicological aspects of pulmonary delivery are also discussed.

Recent advances in nanooncology

Nanobiotechnology is playing an important role in advances in oncology and currently nanooncology is the most important chapter of nanomedicine. Nanobiotechnologies have refined molecular diagnostics and enabled early detection of tumors and discovery of biomarkers of cancer. Various nanoparticles are the basis of diagnostic assays for cancer as well as contrast materials for MRI. Nanobiotechnology is facilitating the discovery and development of drugs for cancer. Several nanobiotechnologies, mostly based on nanoparticles, have been described to facilitate drug delivery in cancer, which is important for optimizing the effect of drugs and reducing toxic side effects. Nanoparticles for targeted drug delivery in cancer enable combination of diagnostics and therapeutics and act as adjuncts to hyperthermia and photodynamic therapy. Several applications of nanobiotechnology in cancer surgery include use of nanoparticles to visualize tumor during surgery as aid to proper removal, and nanorobotics for remotely controlled diagnostics combined with therapeutics. Selected new developments in nanooncology have been highlighted in this review and these point to an important role in development of personalized oncology.

Gadolinium chelate coated gold nanoparticles as contrast agents for both X-ray computed tomography and magnetic resonance imaging

Functionalized gold nanoparticles were applied as contrast agents for both in vivo X-ray and magnetic resonance imaging. These particles were obtained by encapsulating gold cores within a multilayered organic shell which is composed of gadolinium chelates bound to each other through disulfide bonds. The contrast enhancement in MRI stems from the presence of gadolinium ions which are entrapped in the organic shell, whereas the gold core provides a strong X-ray absorption. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in the lungs, spleen, and liver.

Synthesis, characterization, and in vitro testing of superparamagnetic iron oxide nanoparticles targeted using folic Acid-conjugated dendrimers

Organic-coated superparamagnetic iron oxide nanoparticles (OC-SPIONs) were synthesized and characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. OC-SPIONs were transferred from organic media into water using poly(amidoamine) dendrimers modified with 6-TAMRA fluorescent dye and folic acid molecules. The saturation magnetization of the resulting dendrimer-coated SPIONs (DC-SPIONs) was determined, using a superconducting quantum interference device, to be 60 emu/g Fe versus 90 emu/g Fe for bulk magnetite. Selective targeting of the DC-SPIONs to KB cancer cells in vitro was demonstrated and quantified using two distinct and complementary imaging modalities: UV-visible and X-ray fluorescence; confocal microscopy confirmed internalization. The results were consistent between the uptake distribution quantified by flow cytometry using 6-TAMRA UV-visible fluorescence intensity and the cellular iron content determined using X-ray fluorescence microscopy.

Magnetic drug-targeting carrier encapsulated with thermosensitive smart polymer: core-shell nanoparticle carrier and drug release response

A novel magnetic drug-targeting carrier consisting of magnetic nanoparticles encapsulated with a smart polymer with characteristics of controlled drug release is described. The carrier is characterized by functionalized magnetite (Fe(3)O(4)) and conjugated therapeutic agent doxorubicin, which is encapsulated with the thermosensitive polymer, dextran-g-poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [dextran-g-poly(NIPAAm-co-DMAAm)]. The surface of magnetite nanoparticles was functionalized by chemical bonding with 3-mercaptopropionic acid hydrazide (HSCH(2)CH(2)CONHNH(2)) via Fe-S covalent bonds. The anticancer therapeutic drug, doxorubicin, was attached to the surface of the functionalized magnetic nanoparticles through an acid-labile hydrazone-bond, formed by the reaction of hydrazide group of HSCH(2)CH(2)CONHNH(2) with the carbonyl group of doxorubicin. The dextran-g-poly(NIPAAm-co-DMAAm) smart polymer exhibits a lower critical solution temperature (LCST) of approximately 38 degrees C, which is representative of a phase transition behavior. This behavior allows for an on-off trigger mechanism. At an experimental temperature lower than LCST, the drug release was very low. However, at a temperature greater than LCST, there was an initially rapid drug release followed by a controlled released in the second stage, especially, in the mild acidic buffer solution of pH 5.3. The release of drug is envisaged to occur by the collapse of the encapsulated thermosensitive polymer and cleavage of the acid-labile hydrazone linkage. The proposed carrier is appropriately suitable for magnetic targeting drug delivery system with longer circulation time, reduced side effects and controlled drug release in response to the change in external temperature.

Nanoscale Energy Deposition by X-ray Absorbing Nanostructures

Here we wish to demonstrate a unique property of nanomaterials: energy deposition with nanometer precision from low-energy electrons released from these nanostructures interacting with hard X-ray radiation in aqueous solution. Three effects combine to cause this phenomenon: (1) localized absorption of X-rays by nanostructures, (2) effective release of low-energy electrons from small nanostructures, and (3) efficient deposition of energy in water in the form of radicals and electrons. This combination creates localized X-ray absorption and localized energy deposition of nanometer precision. We confirmed the theoretically predicted nanoscale energy deposition distribution by measuring hydroxyl radical-induced DNA strand breaks, and observed enhanced damage to a 5600-bp DNA molecule from approximately 10 chemically conjugated small gold nanoparticles under X-ray radiation. These results provide a general guidance to applications of this new concept in many fields including radiation chemistry, radiology, radiation oncology, biochemistry, biology, and nanotechnology.

Nanomedicine for drug delivery and imaging: a promising avenue for cancer therapy and diagnosis using targeted functional nanoparticles

The diagnosis and treatment of cancer or tumor at the cellular level will be greatly improved with the development of techniques that enable the delivery of analyte probes and therapeutic agents into cells and cellular compartments. Organic and inorganic nanoparticles that interface with biological systems have recently attracted widespread interest in the fields of biology and medicine. The new term nanomedicine has been used recently. Nanoparticles are considered to have the potential as novel intravascular or cellular probes for both diagnostic (imaging) and therapeutic purposes (drug/gene delivery), which is expected to generate innovations and play a critical role in medicine. Target-specific drug/gene delivery and early diagnosis in cancer treatment is one of the priority research areas in which nanomedicine will play a vital role. Some recent breakthroughs in this field recently also proved this trend. Nanoparticles for drug delivery and imaging have gradually been developed as new modalities for cancer therapy and diagnosis. In this article, we review the significance and recent advances of gene/drug delivery to cancer cells, and the molecular imaging and diagnosis of cancer by targeted functional nanoparticles.

Core-shell magnetite nanoparticles surface encapsulated with smart stimuli-responsive polymer: synthesis, characterization, and LCST of viable drug-targeting delivery system

We describe here the synthesis of a novel magnetic drug-targeting carrier characterized by a core-shell structure. The core-shell carrier combines the advantages of a magnetic core and the stimuli-responsive property of the thermosensitive biodegradable polymer shell (e.g., an on-off mechanism responsive to external temperature change). The composite nanoparticles are approximately 8 nm in diameter with approximately 3 nm shell. The lower critical solution temperature (LCST) is approximately 38 degrees C as determined by UV-vis absorption spectroscopy. The carrier is composed of cross-linked dextran grafted with a poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [dextran-g-poly(NIPAAm-co-DMAAm)] shell and superparamagnetic Fe3O4 core. Fourier transform infrared spectroscopy (FTIR) confirmed the composition of the carrier. The synthesized magnetic carrier system has potential applications in magnetic drug-targeting delivery and magnetic resonance imaging.

Encapsulation of Paclitaxel in Macromolecular Nanoshells

An electrostatic layer-by-layer self-assembly technique was used to encapsulate solid core paclitaxel nanoparticles within a polymeric nanometer-scale shell. This approach provides a new strategy for the development of polymeric vehicles that control drug release and target diseased tissues and cells specific to the ailment, such as breast cancer. Core paclitaxel nanoparticles, 153 +/- 28 nm in diameter, were prepared using a modified nanoprecipitation technique. A nanoshell composed of multilayered polyelectrolytes, poly(allylamine hydrochloride) and poly(styrene-4-sulfonate) was assembled stepwise onto core charged drug nanoparticles. In vitro studies were performed to determine the anticancer activity of paclitaxel core-shell nanoparticles. Paclitaxel core-shell nanoparticles induced cell cycle arrest in the G2/M phase after 24 and 48 h of incubation with a human breast carcinoma cell line, MCF-7. Changes in MCF-7 cell morphology, fragmentation of the nucleus, and loss of cell-cell contacts indicated that the cells responded to paclitaxel core nanoparticles upon treatment for 24 and 48 h. Cells arrested in G2/M phase illustrated abnormal microtubule and actin cytoskeleton morphology. The core-shell drug nanoparticles fabricated using this procedure provide a new approach in the delivery of paclitaxel devoid of Cremophor EL, a solvent that causes adverse side effects in patients undergoing chemotherapy for treatment of metastasized mammary cancers.

Hybrid Gadolinium Oxide Nanoparticles: Multimodal Contrast Agents for in Vivo Imaging

Luminescent hybrid nanoparticles with a paramagnetic Gd2O3 core were applied as contrast agents for both in vivo fluorescence and magnetic resonance imaging. These hybrid particles were obtained by encapsulating Gd2O3 cores within a polysiloxane shell which carries organic fluorophores and carboxylated PEG covalently tethered to the inorganic network. Longitudinal proton relaxivities of these particles are higher than the positive contrast agents like Gd-DOTA which are commonly used for clinical magnetic resonance imaging. Moreover these particles can be followed up by fluorescence imaging. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in lungs and liver.

Encapsulation and suspension of hydrophobic liquids via electro-hydrodynamics

There are situations in which bioactive products of interest in biotechnology turn out to be hydrophobic. To reach high uniform levels of such products in water-based host fluids, such as those existing in many biological environments, one strategy consists on dividing the bioactive product into tiny micrometer (or sub-micrometer) pieces, since these are much more amenable of being uniformly dispersed and stabilized in the host fluid. On the other hand, if the bioactive product must act at specific locations, these micrometer pieces need to be hold in place, an objective that may be achieved by encapsulating them in mats of fibers. Here we demonstrate how these tasks may be accomplished by resorting to the generation and control of electrified coaxial jets of a hydrophilic liquid surrounding the hydrophobic liquid carrying the bioactive substance. When the process is carried out inside a dielectric liquid, double oil/water/oil and simple oil/water emulsions may be formed. On the other hand, when the process runs in air and a biopolymer is added to the hydrophilic liquid, then non woven mats of beaded nanofibers, encapsulating the bioactive product in the beads, are generated.

Carving Out Niches for Nanostructures: Implementation and Interplay of Building Blocks, Methods, and Tools

The number and diversity of techniques to create well-defined polymeric architectures has set the foundation to reinvent macromolecular chemistry’s tenor. This development offers the chance to build refined structures with multifaceted, cross-disciplinary applications. We discuss a few advances in the design and development of selected nanoobjects with far-reaching potential. Herein, well-defined building blocks and introduced methods to establish three-dimensional architectures will be presented. Sequential attachment strategies and tools taken from biological chemistries achieve new levels of specificity.