Encapsulation Of Iron Oxide Nanoparticles Research Articles

Engineering Magnetic Extracellular Vesicles Mimetics for Enhanced Targeting Chemodynamic Therapy to Overcome Ovary Cancer.

Chemodynamic therapy (CDT), employing metal ions to transform endogenous H2O2 into lethal hydroxyl radicals (•OH), has emerged as an effective approach for tumor treatment. Yet, its efficacy is diminished by glutathione (GSH), commonly overexpressed in tumors. Herein, a breakthrough strategy involving extracellular vesicle (EV) mimetic nanovesicles (NVs) encapsulating iron oxide nanoparticles (IONPs) and β-Lapachone (Lapa) was developed to amplify intracellular oxidative stress. The combination, NV-IONP-Lapa, created through a serial extrusion from ovarian epithelial cells showed excellent biocompatibility and leveraged magnetic guidance to enhance endocytosis in ovarian cancer cells, resulting in selective H2O2 generation through Lapa catalysis by NADPH quinone oxidoreductase 1 (NQO1). Meanwhile, the iron released from IONPs ionization under acidic conditions triggered the conversion of H2O2 into •OH by the Fenton reaction. Additionally, the catalysis process of Lapa eliminated GSH in tumor, further amplifying oxidative stress. The designed NV-IONP-Lapa demonstrated exceptional tumor targeting, facilitating MR imaging, and enhanced tumor suppression without significant side effects. This study presents a promising NV-based drug delivery system for exploiting CDT against NQO1-overexpressing tumors by augmenting intratumoral oxidative stress.

Development and characterization of lipid nanocapsules loaded with iron oxide nanoparticles for magnetic targeting to the blood-brain barrier.

Brain drug delivery is severely hindered by the presence of the blood-brain barrier (BBB). Its functionality relies on the interactions of the brain endothelial cells with additional cellular constituents, including pericytes, astrocytes, neurons, or microglia. To boost brain drug delivery, nanomedicines have been designed to exploit distinct delivery strategies, including magnetically driven nanocarriers as a form of external physical targeting to the BBB. Herein, a lipid-based magnetic nanocarrier prepared by a low-energy method is first described. Magnetic nanocapsules with a hydrodynamic diameter of 256.7 ± 8.5nm (polydispersity index: 0.089 ± 0.034) and a ξ-potential of -30.4 ± 0.3mV were obtained. Transmission electron microscopy-energy dispersive X-ray spectroscopy analysis revealed efficient encapsulation of iron oxide nanoparticles within the oily core of the nanocapsules. Both thermogravimetric analysis and phenanthroline-based colorimetric assay showed that the iron oxide percentage in the final formulation was 12 wt.%, in agreement with vibrating sample magnetometry analysis, as the specific saturation magnetization of the magnetic nanocapsules was 12% that of the bare iron oxide nanoparticles. Magnetic nanocapsules were non-toxic in the range of 50-300μg/mL over 72h against both the human cerebral endothelial hCMEC/D3 and Human Brain Vascular Pericytes cell lines. Interestingly, higher uptake of magnetic nanocapsules in both cell types was evidenced in the presence of an external magnetic field than in the absence of it after 24h. This increase in nanocapsules uptake was also evidenced in pericytes after only 3h. Altogether, these results highlight the potential for magnetic targeting to the BBB of our formulation.

Enhanced Magnetic Properties of Iron Oxide Nanoparticles Encapsulated in Cobalt Nanopowder Derived from Sunur-Pariaman Beach Sand

Cobalt encapsulated iron oxide nanoparticles based on Sunur-Pariaman beach sand were prepared using ball milling method. Cobalt nanoparticles with concentration of 0, 5,10 and 15 wt.% were added to the iron oxide nanoparticles. Un-encapsulated iron oxide nanoparticles revealed as pure cubic structure of magnetite phase well matched to JCPDS No. 03-0863 with crystallite size in the range of 30.86 -34.91 nm confirmed by X-Ray diffractometer (XRD). Saturation, remanance magnetization and coercivity increase with an increase of cobalt concentration for Co-encapsulated iron oxide nanopartcles showed good magnetic properties. These findings display excellence performance of cobalt encapsulated iron oxide nanparticles compared to un-encapsulated iron oxide nanoparticles and has been considered to be a potential candidate to be used as catalyst for degradation of methylene blue. The concentration of iron (Fe) and titanium (Ti) increase after being milled 100h. However, non iron oxide nanoparticles decrease.

Magnetic resonance imaging of pancreatic islets using tissue–adhesive particles containing iron oxide nanoparticles

Post–transplantation tracking of pancreatic islets is a prerequisite for advancing cell therapy to treat type 1 diabetes. Magnetic resonance imaging (MRI) has emerged as a safe and non–invasive technique for visualizing cells in clinical applications. In this study, we proposed a novel MRI contrast agent formulation by encapsulating iron oxide nanoparticles (IONPs) in poly(lactic–co–glycolic acid) (PLGA) particles functionalized with a tissue adhesive polydopamine (PD) layer (IONP–PLGA–PD MS). Intriguingly, our particles facilitated efficient and robust labeling through a one–step process, allowing for the incorporation of a substantial amount of IONPs without detrimental impacts on the viability and functionality of pancreatic islets. The MRI signals emanating from islets labeled using our particles were found to be stable over 30 days in vitro and 60 days when transplanted under kidney capsules of diabetic mice. These results suggest that our approach provides a potential platform for monitoring the fate of pancreatic islets after transplantation.

Magnetic gelatin nanoparticles as a biocompatible carrier system for small interfering RNA in human colorectal cancer: Synthesis, optimization, characterization, and cell viability studies

Iron oxide-based nanoparticles have gained tremendous attention in developing next-generation personalized medicine modalities. Gelatin can be a good alternative for encapsulating iron oxide nanoparticles with its biocompatibility, biodegradability, low immunogenicity, and richness of functional groups. Herein, magnetic iron oxide nanoparticles (MNPs) were synthesized, coated with gelatin (Gel-MNPs), and loaded with mammalian target of rapamycin (mTOR)-silencing siRNA to induce the in vitro therapeutic effect in colorectal cancer (CRC) cells. To the best of our knowledge, this study is the first report using Gel-MNPs as siRNA carriers. We first optimized several experimental conditions for the preparation of MNPs and Gel-MNPs and the resulting optimized nanoparticles showed a narrow size and size distribution. Gelatin-coating increased the storage stability by preventing the aggregation of MNPs and did not alter the magnetic characteristics of MNPs significantly. siRNA encapsulation abilities of Gel-MNPs were determined in the range of 18.4 and 41.5% in varying siRNA amounts. Bare Gel-MNPs were highly cytocompatible against CRC cells, Caco-2, while Gel-MNPs-mTOR-siRNA exhibited a significant anticancer effect to kill these cells. Comparison with HiPerFect, a commercial siRNA transfection reagent, demonstrated that Gel-MNPs-mTOR-siRNA inhibited cell viability almost similar to or better than HiPerFect-mTOR-siRNA. Taken together, our data indicated that Gel-MNPs could potentially be used in further gene silencing approaches as a safe and multifunctional siRNA carrier candidate.

In situ encapsulation of iron oxide nanoparticles into nitrogen-doped carbon nanotubes as anodic electrode materials of lithium ion batteries.

Fe-based oxides are considered as promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities, low cost, natural abundance and environmental friendliness. However, their severe volume expansion upon cycling and poor conductivity limit their cycling stability and rate capability. To address this issue, a hybrid of Fe2O3 nanoparticles encapsulated at the endpoints of nitrogen-doped CNTs (Fe2O3@NCNTs) is designed and prepared using a metal-catalyzed graphitization-nitridization driven tip-growth process and subsequent oxidation in air. When evaluated as an anode material for LIBs, this Fe2O3@NCNT hybrid exhibits a high capacity of 1145 mA h g-1 at 100 mA g-1, excellent rate capability of 907 mA h g-1 at 5.0 A g-1 and remarkable cycling stability of 856 mA h g-1 after 800 cycles at 1 A g-1, which are much superior to those of the Fe2O3/carbon black (CB) control material. The outstanding electrochemical performance benefits from the unique nanoarchitecture of Fe2O3@NCNTs, which provides a porous conductive matrix for effective electron-ion transport, and provides space confining carbon nanocaps as well as stress buffer nanocavities for robust structural stability during the lithiation/delithiation process. The results may pave the way for the rational structural design of high-performance metal oxide-based anode materials for next-generation LIBs.

Modified Polyethylene Glycol Encapsulated Iron Oxide Nanoparticles for Accelerated Wound Healing Application

One of the key factors required in tissue engineering/ regeneration is to create a dynamic platform to increase the interaction of cells in response to various stimuli. In this context, facile synthesis of modified polyethylene glycol (FL PEG) encapsulated Iron Oxide nanoparticles [PoeM (Fe) NPs] is reported for its wound healing application in presence of an external magnetic field. Iron Oxide nanoparticles (8 ± 2nm) are synthesized and coated with FL PEG resulting in the formation of PoeM (Fe) NPs. The synthesized nanoparticles are characterized for their UV-Vis absorbance, DLS and TEM. These PoeM (Fe) NPs show excellent biocompatibility and enhanced wound healing activity in L929 fibroblasts when compared with control groups. This study could pave the way for the development of novel biomimetic nanosystems for wound healing applications.

Study of the Effectiveness of Chitosan Encapsulated Iron Oxide Nanoparticles

The magnetic iron oxide nanoparticles have been synthesized by using co-precipitation approach. Chitosan coated nanoparticles compare the effect of surface coating on the stability and toxicity of nanoparticles. Invitro cytotoxicity of the nanoparticles are evaluated by three-(four-5) dimethyl thiazole-2-yl and -two,5, diphenyl thiazoniam bromide (MTT assay) along with glide cytometry examine for cell viability. Does dependent reduction was observed in SKMEL cancer cells administered with different concentration of the sample. I50 value obtained for the Iron nanoparticle is 217.75µg/Ml. The fluorescence primarily based real time opposite transcription PCR(RT-PCR) is widely used for the quantification of constant state mRNA ranges and is a crucial device for primary research molecular medicine and biotechnology. FTIR amino companies were acted as capping sites for the iron nanoparticles stabilization. In antibacterial studies Gentamycin 80mcg showed the higher activity of Iron nanoparticles.

Facile bioinspired synthesis of iron oxide encapsulating silica nanocapsules

Iron oxide nanoparticles have been extensively studied for a wide variety of applications. However, there remains a challenge in developing hierarchical magnetic iron oxide nanoparticles as existing synthetic techniques require harsh, toxic chemical conditions and high temperatures or give poorly defined product with weak magnetic properties. In addition, drug loading is limited to post-loading methods such as chemical conjugation or surface adsorption that have poor loading efficiency and are prone to premature drug release. We report a facile biomimetic method for making iron oxide nanoparticle-loaded silica nanocapsules based on a bimodal catalytic peptide surfactant stabilized nanoemulsion template. Iron oxide nanoparticles can be preloaded into the oil phase of the nanoemulsion at tunable concentrations, and the excellent surface activity of the designed bimodal peptide in combination with sufficient electrostatic repulsion promotes the stability of the nanoemulsions. Biosilicification induced by the catalytic peptide module leads to the formation of silica shell nanocapsules containing a magnetic oil core. The bioinspired silica nanocapsules encapsulating iron oxide nanoparticles demonstrate the next-generation of magnetic nanostructures for drug delivery applications.

Synthesis and Characterization of Modified Kaolin-Bentonite Composites for Enhanced Fluoride Removal from Drinking Water

Fluoride-contaminated drinking waters are known to cause severe health hazards such as fluorosis and arthritis. This paper presents the encapsulation of iron oxide nanoparticles in kaolin-bentonite composites adsorbents (KBNPs) for the removal of fluoride from drinking water by adsorption compared with kaolin-bentonite composite (KB). Adsorbents with an average weight of ∼200 mg and ∼7 mm diameter (granules) were prepared in the ratio of 10 : 10 : 0.1 for kaolinite, bentonite, and magnetite nanoparticles, respectively. The granules were air-dried and calcined at 750°C and contacted with 2 mg/L sodium fluoride solution at varying time periods. The adsorbents were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) formulation, and Brunauer–Emmett–Teller (BET), whereas the adsorption mechanism and the kinetics were explained using the Langmuir isotherm, Freundlich models, and pseudo-first-order and pseudo-second-order models. The results showed that the BET surface areas for the granules were 10 m2/g and 3 m2/g for KBNPs and KB, respectively. The SEM images for the adsorbents before and after adsorption confirm the plate-like morphology of kaolin and bentonite. The FTIR analyses of bentonite (3550 cm−1–4000 cm−1) and kaolin (400–1200 cm−1) correspond to the structural hydroxyl groups and water molecules in the interlayer space of bentonites and the vibrational modes of SiO4 tetrahedron of kaolin, respectively. The KBNPs composites also recorded a fluoride removal efficiency of ∼91% after 120 minutes compared with 64% for KB composites without Fe3O4 nanoparticles. The adsorptions of fluoride by the KBNPs and KB granules were found to agree with the Freundlich isotherm and a pseudo-second-order kinetic model, respectively. The results clearly show that the impregnation of clays with magnetite nanoparticles has significant effect in the removal of fluoride, and the implication of the results has been discussed to show the impact of clay-magnetite nanoparticles composites in the removal of fluoride from contaminated water.

DFT and experimental studies of iron oxide-based nanocomposites for efficient electrocatalysis

Encapsulated iron oxide nanoparticles with g-C3N4 shells (Fex-NC) promote the hydrogen evolution reaction. The interactions between Fex-NC nanocomposites were investigated by DFT.

Block Copolymer Nanosystems Encapsulating Magnetic Nanoparticles and Drug.

The goal of this study was to investigate the solution behavior of nanosystems composed of self-assembling amphiphilic diblock copolymers, poly(ethylene oxide-b-phenyl oxazoline) and poly(isoprene-b-ethylene oxide) (PEO-b-PPhOx and PI-b-PEO), with encapsulated iron oxide nanoparticles (γ-Fe₂O₃). The hybrid nanosystems were tested in aqueous solution, under physiological conditions and in mixtures with serum proteins. Light scattering methods were used to probe changes in size and mass of the formed aggregates in different solution conditions and as a function of storage time. The developed stable hybrid systems with encapsulated magnetic nanoparticles were able to entrap the anti-inflammatory drug, indomethacin. This work demonstrates versatile nanosystems with metal oxide characteristics for bio-imaging and the potential for drug delivery in aqueous media.

Magnetic particle imaging performance of liposomes encapsulating iron oxide nanoparticles

Magnetic Particle Imaging (MPI) is a new imaging modality that quantifies spatial distribution of superparamagnetic iron oxide nanoparticles in a field of view through their non-linear magnetization response to an applied magnetic field. Liposomes loaded with magnetic nanoparticles (magnetoliposomes) are potential theranostic drug carriers that can combine magnetic properties with drug carrier ability. Prior work suggests that MPI signal can be affected by dipolar interactions between magnetic nanoparticles in close proximity – for instance, in a polymer matrix. Here we evaluate if encapsulating magnetic nanoparticles in liposomes has an impact in their MPI performance. For this purpose, magnetoliposomes were prepared using charge-stabilized iron oxide nanoparticles (IONPs) and their physical, magnetic and MPI properties were characterized. Interestingly, encapsulation of IONPs in magnetoliposomes led to an increase in MPI signal per unit mass.

TMOD-16. MULTIFUNCTIONAL NANOPARTICLES USED FOR MAGNETIC RESONANCE/NIR FLUORESCENCE DUAL-MODAL IMAGING AND CHEMOTHERAPY OF GLIOMA

Abstract PURPOSE Glioma is the most common malignant brain tumor and infamous for its high invasiveness and lethality. Therefore, plenty of techniques like intraoperative MRI (iMRI) and fluorescence-guided surgery were performed to improve the surgical resection rate of glioma. In addition, the chemotherapy effect of glioma was severely restricted because of the low blood-brain barrier (BBB) permeability of traditional therapeutic drugs. Doxorubicin (DOX) is a widely used antineoplastic drug, but its application in glioma therapy is prevented by the BBB. Thus, it is urgent to develop novel diagnostic methods and drug delivery systems to improve glioma treatment effect. MATERIALS AND METHODS In this study, we constructed a multifunctional nanotheranostic agent which integrated MR imaging, fluorescence imaging and targeting chemotherapy for glioma by encapsulating iron oxide nanoparticles, DOX and indocyanine green (ICG) with PEGylated phospholipid. RESULTS The obtained multifunctional were proved with an average diameter of 22.9 nm. In vitro cell experiments demonstrated that the nanoparticle effectively enhanced cellular uptake of DOX compared with that of free DOX. In vivo MR and fluorescence imaging not only demonstrated that the nanotheranostic agent effectively crossed the BBB and selectively accumulated at the tumor area, but also easily monitored the real-time therapeutic outcome. Among all treatment groups, C6 glioma-bearing rats treated with nanoparticles exhibited the maximal degree of efficacy, including the longest survival times and smallest tumor volume. CONCLUSION All these results suggested that the multifunctional nanoparticles could be simultaneously used for iMRI and fluorescence-guided surgery to increase the resection rates, as well as delivering chemotheraputic drugs to tumor site to improve therapeutic effect. We believe that this multifunctional nanoparticle might serve as a potential theranostic treatment for glioma in the near future.

Biocompatible superparamagnetic sub-micron vaterite particles for thermo-chemotherapy: From controlled design to in vitro anticancer synergism.

A promising candidate for the development of controlled and targeted nanoscale drug delivery system but less studied so far is calcium carbonate (CaCO3) in the form of porous polycrystalline vaterite spheres. Vaterite has been shown to exhibit various beneficial properties such as excellent biocompatibility, high drug loading capacity, and pH-sensitive decomposition under mild conditions. However, fabricating vaterite particles with improved porosity, high surface area and loading a payload into the common synthesis method is still a challenge. Here we report on the synthesis of a highly porous, spherical superparamagnetic vaterite particles (PMVP) of size ∼800 nm encapsulating Iron oxide nanoparticles (IONPs) in a one-step reaction and loaded with DOX molecules through electrostatic attractions and physisorption for cancer thermo-chemotherapy application. The main advantage of the PMVP-DOX is that it can be magnetically targeted into the tumor region and once exposed to the tumor tissues characteristic acidic pH, the PMVP nanoparticle dissociates, releasing the DOX and intelligently converts the pH-triggered drug release into a tumor triggered drug release. Simultaneous application of alternating magnetic field (AMF) generates localized heat of the tumor tissues due to the hyperthermic capability of the IONPs in the PMVP and results in the synergistic tumoricidal activities.

Encapsulation of Iron Oxide Nanoparticles and Oil-in-Water Nanocarriers in Microgels with Biomedical Potential.

Here we report on the design and characterization of calcium-alginate microgels (MGs) containing positively charged iron oxide nanoparticles (IONPs) and negatively charged oil-in-water (O/W) nanocarriers (NCs). To provide ionic compatibility of IONPs with the negatively charged NCs and alginate in MGs, they were coated with the anionic polysaccharides alginate, carrageenan or sulfobutyl-β-cyclodextrin. The mixing of both nanostructures (coated-IONPs and O/W NCs) with alginate solutions provide homogeneous dispersions able to form spherical hydrogels with different sizes (250-1400 micrometers) and encapsulating the nanostructures with high efficiency. MGs loaded with both nanostructures were reactive to continuous (attractive interaction) and alternating magnetic field (heat release similar to non-encapsulated IONPs). The encapsulation of both nanostructures in MGs was maintained even after 7 days of storage at 40 °C. We postulate that the above results will be of interest for the design of hydrogel formulations with therapeutic applications.

Cross-Linked Polystyrene Shells Grown on Iron Oxide Nanoparticles via Surface-Grafted AGET-ATRP in Microemulsion.

Most applications of nanoparticles require robust stabilization, for example, by surface-bound ligands or the encapsulation within polymer shells. Furthermore, for biomedical applications, the particles must be dispersible in a complex biological environment. Thus, high-quality nanoparticles synthesized in organic solvents must be transferred into aqueous media. Here, we present a novel scalable method enabling the robust hydrophilic encapsulation of non-agglomerated nanoparticles by growing polystyrene shells via AGET-ATRP in microemulsion. To demonstrate this approach, we encapsulate iron oxide nanoparticles (diameter: 13.7 ± 0.6 nm). Because the ATRP initiator is grafted onto the nanoparticles' surface, the shells are covalently attached to the iron oxide cores. By varying the amount of monomers, the shell thickness can be adjusted precisely, as indicated by the increasing hydrodynamic size from ∼22 to 26 nm (DLS, number mean) with an increasing amount of added monomers. Moreover, the degree of cross-linking can be controlled by the amount of added divinylbenzene (DVB). To evaluate the robustness of the polymer shells against ion infusion, we introduce a novel colorimetric method, which is based on the formation of the red iron thiocyanate complex. After addition of HCl, the increase in absorbance at 468 nm indicates leaching of iron ions from the polymer-encapsulated core particles. These measurements confirm that with increasing shell thickness, significantly improved shielding is achieved. Furthermore, high concentrations of added DVB [33-50% (v/v) in a monomer mixture] improve the shielding effect. However, when smaller amounts of DVB were added [10-25% (v/v)], the shielding effect was diminished, even in comparison to non-cross-linked polymer shells. This finding suggests a higher porosity of shells with a low degree of cross-linking.

The magnetic biochar derived from banana peels as a persulfate activator for organic contaminants degradation

The magnetic biochar (γ-Fe2O3@BC) derived from banana peels was synthesized by a facile one-pot thermal process and used as the cost-effective and recyclable persulfate (PS) activator for organic contaminants degradation. The results showed that the encapsulated iron oxide nanoparticles not only introduced the magnetism into biochar for easy separation, but also influenced the catalytic ability for PS activation. The γ-Fe2O3@BC was found to be highly effective for bisphenol A (BPA) degradation without pH adjustment. A complete removal of BPA was obtained within 20 min with an observed rate constant (kobs) of 0.1849 min−1, which was almost two times as large as that (0.0956 min−1) of pure biochar. Further, it exhibited high mineralization efficiency for the degradation of various organic contaminants. The high catalytic activity could be attributed to large BET surface area, dispersed iron species, abundant oxygen functional groups and rich doped nitrogen. Radical quenching experiments and electron spin resonance (ESR) studies confirmed that OH, SO4− and O2− were all involved in the radical oxidation process which was responsible for BPA degradation. A mechanism of PS activation by the γ-Fe2O3@BC catalyst was proposed based on the synergistic effect of biochar and iron.

Tumor-Specific Drug Release and Reactive Oxygen Species Generation for Cancer Chemo/Chemodynamic Combination Therapy.

The combination of chemotherapeutic drugs and reactive oxygen species (ROS) is a promising strategy to achieve improved anticancer effect. Herein, a nanomedicine (LaCIONPs) that can achieve tumor‐specific chemotherapeutic drug release and ROS generation is developed for cancer chemo/chemodynamic combination therapy. The LaCIONPs are constructed by encapsulation of iron oxide nanoparticles (IONPs) and β‐lapachone (La) in nanostructure assembled by hydrogen peroxide (H2O2)‐responsive polyprodrug and pH‐responsive polymer. Through the enhanced permeability and retention effect, the nanosized LaCIONPs can accumulate in tumor tissue. After the LaCIONPs are internalized by tumor cells, the structure of LaCIONPs is disintegrated in acidic intracellular environment, leading to rapid release of La and iron ions. Then the released La generates massive H2O2 through tumor specific catalysis. On the one hand, H2O2 further reacts with iron ions to produce highly toxic hydroxyl radicals for chemodynamic therapy. On the other hand, H2O2 also activates the release of camptothecin from the polyprodrug for chemotherapy. The potent antitumor effect of the LaCIONPs is demonstrated by both in vitro and in vivo results. Therefore, the LaCIONP is a promising nanomedicine for tumor‐specific chemo/chemodynamic combination therapy.

In vivo fate of free and encapsulated iron oxide nanoparticles after injection of labelled stem cells.

Nanoparticle contrast agents are useful tools to label stem cells and monitor the in vivo bio-distribution of labeled cells in pre-clinical models of disease. In this context, understanding the in vivo fate of the particles after injection of labelled cells is important for their eventual clinical use as well as for the interpretation of imaging results. We examined how the formulation of superparamagnetic iron oxide nanoparticles (SPIONs) impacts the labelling efficiency, magnetic characteristics and fate of the particles by comparing individual SPIONs with polyelectrolyte multilayer capsules containing SPIONs. At low labelling concentration, encapsulated SPIONs served as an efficient labelling agent for stem cells. The bio-distribution after intra-cardiac injection of labelled cells was monitored longitudinally by MRI and as an endpoint by inductively coupled plasma-optical emission spectrometry. The results suggest that, after being released from labelled cells after cell death, both formulations of particles are initially stored in liver and spleen and are not completely cleared from these organs 2 weeks post-injection.