A Review of the Resuspension of Radioactively Contaminated Particles by Vehicle and Pedestrian Traffic-Current Theory, Practice, Gaps, and Needs.

ABSTRACT: The resuspension of radioactively contaminated particles in a built environment, such as from urban surfaces like foliage, building exteriors, and roadways, is described empirically by current plume and dosimetry models used for hazard assessment and long-term risk purposes. When applying these models to radiological contamination emergencies affecting urban areas, the accuracy of the results for recent contamination deposition is impacted in two main ways. First, the data supporting the underlying resuspension equations was acquired for open, quiescent conditions with no vehicle traffic or human activities, so it is not necessarily representative of the urban environment. Second, mechanical disturbance by winds in urban canyons and during emergency operations caused by vehicle traffic and human activities are not directly considered by the equations. Accordingly, plume and dosimetry models allow the user to input certain compensating values, but the models do not necessarily supply users instructions on what values to use. This manuscript reviews the available literature to comprehensively and consistently pool data for resuspension due to mechanically induced resuspension applicable to urban contamination. Because there are few studies that directly measured radioactive resuspension due to vehicles and pedestrians, this review novelly draws on a range of other studies involving non-radioactive particles, ranging from outdoor air pollution emissions to indoor allergen transport. The results lead to tabulated, recommended values for specific conditions in the emergency phase to help users of plume and dosimetry models maintain the conservativeness needed to properly capture the potential radiation dose posed by mechanically induced resuspension. These values are of benefit to model users until better data are available. The results also suggest the types of data that may result in improved plume and dose modeling.

Logistics simulation of a remediation effort for a hypothetical radiological contamination scenario.

To mitigate the effects following a large-scale nuclear or radiological material release in an urban environment and to expedite recovery, the Integrated Wash-Aid Treatment Emergency Reuse System (IWATERS) was developed. IWATERS consists of three operations: washing contaminated surfaces with an ionic wash solution, collecting, and treating the contaminated wash solution on-site to remove contaminants, and reusing the treated solution throughout operations to preserve the clean water resource. This study develops a framework to simulate the logistics of IWATERS deployment, thereby gaining an understanding of the timeline for decontamination operations. For this purpose, the Analysis of Mobility Platform and GoldSim were leveraged for a hypothetical contamination scenario covering 65,200 m2 of an urban center. The framework reveals that remediation progress is limited by several resources, notably the availability of vermiculite, a reactive clay that is required to treat the contaminated wash solution. This study also presents how the simulation approach can be used to characterize alternatives to reduce the influence of limited resources on operational progress. Overall, this work lays the foundation for evaluating different decontamination methods through detailed logistics simulation, i.e., by refining simulation assumptions and expanding the range of scenarios the simulation can depict.

External Dose to Recovery Teams Following a Wide-area Nuclear or Radiological Release Event.

ABSTRACT: The common radionuclide 137Cs is a gamma-ray source term for nuclear reactor accidents, nuclear detonations, and potential radionuclide dispersal devices. For wide-area contamination events, one remediation option integrates water washing activities with on-site treatment of water for its immediate reuse. This remediation option includes washing building and roadways via firehose, collecting the wash water, and passing the contaminated water through chemical filtration beds. The primary objective of this study was to quantify the dose incurred to workers performing a remediation recovery effort for roadways and buildings following a wide-area release event. MicroShield® was employed to calculate the dose to workers at the roadway level and to calculate total dose rates while performing washing activities. This study finds that for a realistic contamination scenario for a wide area of a large urban environment, decontamination crews would be subjected to <220 µSv per person, much less than the 50,000 µSv limit for occupational dose. By extrapolation, one decontamination team of 48 people could continue washing operations on a total of 2.8 km2 before reaching their incurred annual dose limits. Though it is unrealistic to assign one team that entire area, we can conclude external dose will not limit worker deployment given the range of contamination levels adopted in this study.

Decontamination of urban surfaces contaminated with radioactive materials and consequent onsite recycling of the waste water.

Enhancing rapid remediation strategies is paramount for recovery after a large-scale nuclear contamination event in an urban environment. Some current strategies recommend use of readily available equipment, materials, and facilities to expedite recovery. For example, applying pressurized water to contaminated surfaces may effectively remove radioactive contamination. In this study, a commercial power washer removes soluble forms of 152Eu3+, 85Sr2+, and 137Cs+ contamination from common porous building materials, and computer simulations characterize the recycling of the resultant contaminated wash water. Pressure washing the porous building materials under spray conditions typical with do-it-yourself units improved decontamination factors (DFs) for 152Eu compared to low-pressure application of tap water (majority of two-tailed t-test p-values < 0.1), but pressure did not improve DFs for 137Cs or 85Sr. For both pressurized and low-pressure applications, adding potassium ions (K+) to promote ion exchange reactions produced significantly higher DFs for tested radionuclides on asphalt, brick, and concrete. The resultant contaminated wash water can be processed through self-prepared chemical filtration beds of clay and sand. Modeled in a prior study, the beds yielded linear trends (R2 > 0.98) in sensitivity analyses between most bed configuration variables and bed performance variables, permitting flexible ad-hoc bed design. The experimental and simulation results led to estimates of the remediation rate and waste generated after cleaning 250 m2 of cesium-contaminated concrete from the combined deployment of a power washer and two different mobile treatment beds. The first treatment bed was designed to reduce treatment time and processed 1900 L of wash solution in 70 min using 880 kg of clay/sand infill material. Designed to reduce the solid waste generated, the second bed processed the same solution volume in 1040 min (17 h) using 170 kg of clay/sand infill material. The results of this analysis warrant further investigation of power washing with recycled salt solution as an effective rapid decontamination method with manageable waste.

Penetration of fission product ions into complex solids and the effect of ionic wash methods.

During washing of radiologically impacted building surfaces, penetration of radionuclide ions into complex solids associated with these surfaces may occur. This study investigates the penetration of 137Cs, 85Sr, and 152Eu solutions into numerous common building materials and radionuclide behavior when these materials were exposed to a static bath or low-pressure flow of tap water, 0.1 M potassium chloride (KCl), and 0.5 M KCl. The decontamination efficacy and the depth profile for residual contamination were measured to determine the conditions under which applying a wash solution has benefit compared to physically removing the surface material. On asphalt, 70-80% of the radionuclides were found to be within 0.02 mm of the surface. Concrete is more porous than asphalt, and 80% of the radionuclides were within 0.2 mm of the surface for 137Cs and 152Eu and 50-80% for 85Sr. Water effectively removed all contaminants from hard nonporous surfaces. Finally, this paper illustrates that a wash penalty factor concept-defined as ratio of the depth at which 50% of the radioactivity is found in the washed sample divided by the depth at which 50% of radioactivity is found in the control-can serve as a way to quantify whether the wash method increases the depth at which contamination penetrates into the material and thus the material becomes more difficult to decontaminate.

High pressure decontamination of building materials during radiological incident recovery.

The release of radiological material from a nuclear incident has the potential to cause extensive radiological contamination requiring rapid decontamination. A promising method for rapid remediation is the use of pressure washers to decontaminate building and street surfaces. Pressure washers utilize both physical removal through surface ablation and chemical removal through desorption of bonded radionuclides. To understand the extent that each removal mechanism is present, overall removals, depth profiles, and wash water were analyzed from the pressure washing of various surfaces contaminated with cesium, strontium, and europium. Removals were dependent on surface type with over 80% of the radionuclides removed from concrete, 50-80% from asphalt, and only 20-25% from brick. Generally, the closer the radionuclide was to the surface of the material, the higher the removal, with europium being removed most readily followed by cesium then strontium, though some exceptions were evident. Comparing these removals and depth profiles of radionuclides in non-decontaminated coupons revealed that cesium and europium are mostly removed through surface ablation. Strontium, on the other hand, is desorbed from the surface, especially from brick and asphalt surfaces. Correspondingly, cesium and europium were attached to the particulates that were likely removed with the pressurized water. Strontium was primarily dissolved in the wash water, supporting the observation that the radionuclide is desorbed from each surface. Finally, the faster the surfaces were brought through the high pressure spray, the lower the removals, arising from decreases in both the physical and desorption mechanisms. Pressure washers were concluded to be a promising decontamination method during radiological incident relief. However, the surface and radionuclide identity must be considered when developing proper procedures.

Silicate coating to prevent leaching from radiolabeled surrogate far-field fallout in aqueous environments.

Recent characterization of radioactive particles indicate that a large percentage of the radioactivity observed during the Fukushima Daiichi nuclear meltdown was insoluble 137Cs bound within silica microparticles. Therefore, much of the decontamination research performed prior to the Fukushima incident that used either soluble radionuclides deposited onto wet surfaces or large (∼100 µm) particles characteristic of nuclear weapons fallout do not accurately represent the characteristics of potential contamination. Thus, the common practice of extrapolating radioactive decontamination methods generically to all radioactive release events is, at best, suspect. In response, a method to produce chemically-inert, radiolabeled silica particles was developed. Binding 152Eu within a sodium silicate coating required proper temperature control and ethanol was beneficial as a volatile dispersant to limit residues. In the end, a step-wise method, which first deposited 152Eu or 241Am as a nitrate salt, decomposed the salt to a sesquioxide, and finally coated the surface with sodium silicate led to dispersed particles of the desired 2 or 0.5 µm diameters. Dynamic light scattering and scanning election microscopy confirmed the particle size was unchanged. Leaching studies into several common decontaminants were performed to ensure particle inertness. Our approach allows for substitution of other radionuclides making it a robust, simple, and novel method to produce inert particle surrogates for a release event that allows direct comparison of decontamination techniques and contaminant fate studies, greatly aiding the development of response and recovery plans.

A case study of cesium sorption onto concrete materials and evaluation of wash agents: Implications for wide area recovery.

To support the viability of a wash-down approach to mitigating nuclear contamination, this study presents a characterization of the aggregate of a common concrete by optical microscopy and the sorption-desorption characteristics of cesium from these into potential wash solutions. Various minerals with weathered surfaces displayed strong affinity for 137Cs with an effective partition coefficient Kd=120 mL/g for micas,>25-90 mL/g for feldspars, and>25-30 mL/g for amphiboles. The desorption Kd into 0.1M NH4Cl varied greatly but for amphiboles, sandstones, granite, and fine-grained quartzite it was>200 mL/g as a result of irreversible sorption. These same mineral phases are prevalent in all types of building materials, extending our conclusions more broadly to the problem of wide-area urban decontamination. In contrast, ionic solutions desorbed up to 98% of 137Cs from cement, suggesting that fresh concretes with an intact surface layer of cement could be more easily decontaminated if Cs+ interactions with the underlying minerals could be avoided. For practical applications common, non-hazardous chemicals such as sodium, potassium, and ammonium salts are as effective or more effective than harsher chemicals and expensive chelating agents. For example, when treated shortly after exposure, on time-scales commensurate with early response phase activities, 0.5M KCl could remove nearly 50% of bound 137Cs from concrete aggregate. Statistical analyses showed that desorption from the fine aggregate benefited from higher K+ and NH4 + concentrations. These results suggest that contamination in large areas of the urban environment can be dramatically reduced using common chemicals obtained readily from local stores.

Wide-area decontamination in an urban environment after radiological dispersion: A review and perspectives.

Nuclear or radiological terrorism in the form of uncontrolled radioactive contamination presents a unique challenge in the field of nuclear decontamination. Potential targets require an immediate decontamination response, or mitigation plan to limit the social and economic impact. To date, experience with urban decontamination of building materials - specifically hard, porous, external surfaces - is limited to nuclear weapon fallout and nuclear reactor accidents. Methods are lacking for performing wide-area decontamination in an urban environment so that in all release scenarios the area may be re-occupied without evaluation and/or restriction. Also lacking is experience in developing mitigation strategies, that is, methods of mitigating contamination and its resultant radiation dose in key areas during the immediate aftermath of an event and after lifesaving operations. To date, the tremendous strategy development effort primarily by the European community has focused on the recovery phase, which extends years beyond the release event. In this review, we summarize the methods and data collected over the past 70 years in the field of hard, external surface decontamination of radionuclide contaminations, with emphasis on methods suitable for response to radiological dispersal devices and their potentially unique physico-chemical characteristics. This review concludes that although a tremendous amount of work has been completed primarily by the European Community (EU) and the United Kingdom (UK), the few studies existing on each technique permit only very preliminary estimates of decontamination factors for various building materials and methods and extrapolation of those values for use in environments outside the EU and UK. This data shortage prevents us from developing an effective and detailed mitigation response plan and remediation effort. Perhaps most importantly, while the data available does include valuable information on the practical aspects of performing the various remediation methods including costs, coverage rates, manpower, pitfalls, etc., it lacks the details on lessons learned, best practices, and standard procedures, for instance, that would be required to develop a mitigation strategy. While the urban decontamination problem is difficult and there is much more research to do, the existing literature provides a framework for a response plan. Using this framework, in conjunction with computer modeling and relevant data collection, can lead to development of appropriate plans and exercises that would permit development of a mitigation and remediation response.

Evaluation of solid-supported room-temperature ionic liquids containing crown ethers as media for metal ion separation and preconcentration.

Extraction chromatographic (EXC) resins incorporating an appropriate crown ether in an oxygenated organic solvent such as 1-octanol are well established as sorbents for the analytical-scale separation and preconcentration of radiostrontium from a variety of sample types. Recent solvent extraction studies employing crown ethers in various 1-alkyl-3-methylimidazolium-based (CnC1im(+)) room-temperature ionic liquids (RTILs) indicate that under certain conditions, distribution ratios (DSr) for strontium far in excess of those observed with conventional organic solvents are observed. To determine if this increase in liquid-liquid extraction efficiency will lead to improved strontium sorbents, several EXC resins and sol-gel glasses incorporating di-tert-butylcyclohexano-18-crown-6 (DtBuCH18C6) in either 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (C10C1imTf2N) or the related hydroxyalkyl-functionalized IL 1-(12-hydroxydodecyl)-3-butylimidazolium bis[(trifluoromethyl)sulfonyl]imide (C12OHC4im Tf2N) were prepared and characterized. Unexpectedly the performance of these materials was not uniformly better than that of a conventional EXC resin, an apparent result of the greater viscosity of the ionic liquids and the lower solubility of the crown ether in ILs versus conventional organic solvents.

Novel tandem column method for the rapid isolation of radiostrontium from human urine.

A method has been developed for the isolation of strontium from human urine for subsequent determination in sample volumes as low as 5-20 mL. This method involves the acidification of the sample using methanesulfonic acid and its decolorization using charcoal, treatment of the filtrate with Diphonix(®) resin, and subsequent concentration of strontium on Sr resin. Data from retention model simulations provided the initial conditions which were then optimized by actual column separations. Diphonix(®) resin was shown to be effective at removing alkali metal ions from the urine matrix under conditions that retain higher valence ions. The suggested processing method provides 99% recovery of Sr(2+), a concentration factor of 50, and an expected per sample processing time of less than 1 h.

Sequestration, fluorometric detection, and mass spectroscopy analysis of lanthanide ions using surface modified magnetic microspheres for microfluidic manipulation.

Several methods for rapid sequestration, fluorometric detection, and the subsequent mass spectroscopic analysis of lanthanide ions using surface modified polystyrene magnetic microspheres are demonstrated. Mixed-ligand antenna complexes of Eu(3+) in which one of the ligands is attached to the surface of the microspheres have been used as a means for the sequestration, immobilization, and detection of these ions. Using the ion-exchange properties of these microspheres, this scheme has been extended to the detection of nonluminescent ions. The principles of these assays form the basis for operation of a portable microfluidic device for general analytical and nuclear forensics applications and indicate the manner in which the established methods of analytical chemistry, such as liquid-liquid extraction and ion-exchange chromatography, can be adapted for such miniature devices.

Dermal permeation of biocides and aromatic chemicals in three generic formulations of metalworking fluids.

Metalworking fluids (MWF) are complex mixtures consisting of a variety of components and additives. A lack of scientific data exists regarding the dermal permeation of its components, particularly biocides. The aim of this study was to evaluate the dermal permeation of biocides and other aromatic chemicals in water and in three generic soluble oil, semi-synthetic, and synthetic MWF types in order to evaluate any differences in their permeation profiles. An in vitro flow-through diffusion cell study was performed to determine dermal permeation. An infinite dose of different groups of chemicals (6 biocides and 29 aromatic chemicals) was applied to porcine skin, with perfusate samples being collected over an 8-h period. Perfusate samples were analyzed by gas chromatography/mass spectrometry (GC-MS) and ultra-performance liquid chromatography/mass spectroscopy (UPLC-MS), and permeability was calculated from the analysis of the permeated chemical concentration-time profile. In general, the permeation of chemicals was highest in aqueous solution, followed by synthetic, semi-synthetic, and soluble oil MWF. The absorption profiles of most of the chemicals including six biocides were statistically different among the synthetic and soluble oil MWF formulations, with reduced permeation occurring in oily formulations. Permeation of almost all chemicals was statistically different between aqueous and three MWF formulation types. Data from this study show that permeation of chemicals is higher in a generic synthetic MWF when compared to a soluble oil MWF. This indicates that a soluble oil MWF may be safer than a synthetic MWF in regard to dermal permeation of chemicals to allow for an increased potential of systemic toxicity. Therefore, one may conclude that a synthetic type of formulation has more potential to produce contact dermatitis and induce systemic toxicological effects. The dilution of these MWF formulations with water may increase dermal permeability of biocides, allowing for an enhanced risk for systemic toxicological effects and dermatitis potential.

Encapsulation and release of plasminogen activator from biodegradable magnetic microcarriers.

There are a number of therapies available to recanalize occluded arteries. However, even though proven beneficial, these approaches are not without significant shortcomings. Previous research showed that by encapsulating therapeutic thrombolytic enzymes in liposomic formulations, the reperfusion times in vivo were significantly lower than for administration of free thrombolytic. Like liposomes, biodegradable, diblock polymers of poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) have been shown to have therapeutic benefit as delivery vehicles for a variety of drug delivery concepts. We report on new formulations based on tissue plasminogen activator (tPA) encapsulated in magnetic, PLA-PEG microcarriers. We studied the tPA encapsulation efficiency, loading, and release after varying the molecular weight of polymer, carrier size, tPA solution composition, and use of ultrasound to enhance release. We loaded 3.3-9.4wt% tPA and 12-17wt% magnetite into the carriers, depending on the exact formulation. The release of tPA was complete 20min after reconstitution. Ultrasound insonation failed to enhance tPA release rates in smaller carriers but significantly enhanced release in larger carriers. With these formulations, we should be able to achieve lytic concentrations if we can magnetically concentrate 5mg of carrier within about 11ml of blood volume near the clot.

Capture of magnetic carriers within large arteries using external magnetic fields.

Our overall research goal is to advance the safety and effectiveness of acute ischemic stroke therapy by improving the benefit/risk ratio of thrombolysis and hence, the long-term outcome of acute ischemic stroke victims. Our approach is the development of a novel tissue plasminogen activator (t-PA) delivery system based on t-PA-loaded magnetic nano- and microcarriers guided directly to the site of vascular occlusion by external magnetic fields. Such a t-PA delivery system would conveniently combine the advantages of both intravenous (systemic) and intraarterial (catheter-facilitated) thrombolysis: non-invasiveness - the magnetic t-PA carriers can be injected intravenously and targeted, as drug delivery is magnetically guided to and t-PA focally released at and within the vascular clot to induce lysis. The focus of our discussion are the two necessary, fundamental and interrelated bioengineering steps: the research and development of well-characterized, biocompatible, functionally active and t-PA-loaded (encapsulated) magnetic nano- and microcarriers able to induce effective thrombolysis, and the design of magnetic guidance systems for targeted tPA-delivery allowing also the triggered release of the thrombolytic agent at the clot site. In this paper, we theoretically demonstrated magnetic trapping of blood borne magnetic nano- and microcarriers from human large vessels, especially arteries. Then, some preliminary experiments using primate models (monkeys) were done to identify successful in vivo sequestration of magnetic carriers in large and smaller arterial branches after arterial upstream and systemic venous injection. Histology (hematoxylin-eosin stain) verified intraarterial carrier concentration (identified as black carrier agglomerates on H and E staining) at the arterial region above the surface magnet. The results revealed the feasibility of magnetic drug-targeting at arteries and solidified the proposed t-PA delivery system.

Improvement of in vitro thrombolysis employing magnetically-guided microspheres.

Significant shortcomings in clinical thrombolysis efficiencies and arterial recanalization rates still exist to date necessitating the development of additional thrombolysis-enhancing technologies. For example, to improve tPA-induced systemic clot lysis several supplementary treatment methods have been proposed, among them ultrasound-enhanced tissue plasminogen activator (tPA) thrombolysis which has already found some clinical applicability. The rationale of this study was to investigate whether biodegradable, magnetic spheres can be a useful adjuvant to currently existing tPA-induced thrombolysis and further enhance clot lysis results. Based on an envisioned, novel thrombolysis technology--magnetically-guided, tPA-loaded nanocarriers with triggered release of the shielded drug at an intravascular target site--we evaluated the lysis efficiencies of magnetically-guided, non-medicated magnetic spheres in various combinations with tPA and ultrasound. When tPA was used in conjunction with magnetic spheres and a magnetic field, the lysis efficiency under static, no-flow conditions improved by 1.7 and 2.7 fold for red and white clots, respectively. In dynamic lysis studies, the addition of ultrasound and magnetically-guided spheres to lytic tPA dosages resulted in both maximum clot lysis efficiency and shortest reperfusion time corresponding to a 2-fold increase in lysis and 7-fold reduction in recanalization time, respectively. Serial microscopic evaluations on histochemical sections reconfirmed that tPA penetration into and fragmentation of the clot increased with escalating exposure time to tPA and magnetic spheres/field. These results delineate the effectiveness of magnetic spheres as an adjuvant to tPA therapy accelerating in vitro lysis efficiencies beyond values found for tPA with and without ultrasound. We demonstrated that the supplementary use of magnetically-guided, non-medicated magnetic spheres significantly enhances in vitro static and dynamic lysis of red and white blood clots.

2D modeling and preliminary in vitro investigation of a prototype high gradient magnetic separator for biomedical applications.

High gradient magnetic separation (HGMS) of magnetic materials from fluids or waste products has many established industrial applications. However, there is currently no technology employing HGMS for ex-vivo biomedical applications, such as for the removal of magnetic drug- or toxin-loaded spheres from the human blood stream. Importantly, human HGMS applications require special design modifications as, in contrast to conventional use where magnetic elements are permanently imbedded within the separation chambers, medical separators need to avoid direct contact between the magnetic materials and blood to reduce the risk of blood clotting and to facilitate convenient and safe treatment access for many individuals. We describe and investigate the performance of a magnetic separator prototype designed for biomedical applications. First, the capture efficiency of a prototype HGMS separator unit consisting of a short tubing segment and two opposing magnetizable fine wires along the outside of the tubing was investigated using 2D mathematical modeling. Second, the first-pass effectiveness to remove commercially available, magnetic polystyrene spheres from human blood using a single separator unit was experimentally verified. The theoretical and experimental data correlated well at low flow velocities (<5.0 cm/s) and high external magnetic fields (>0.05 T). This prototype separator unit removed >90% in a single pass of the magnetic spheres from water at mean flow velocity < or =8.0 cm/s and from blood mimic fluids (ethylene glycol-water solutions) at mean flow velocity < or =2.0 cm/s. In summary, we describe and prove the feasibility of a HGMS separator for biomedical applications.

A comprehensive in vitro investigation of a portable magnetic separator device for human blood detoxification.

A portable magnetic separator device is being developed for a proposed magnetically based detoxification system. In this paper, the performance of this device was evaluated via preliminary in vitro flow experiments using simple fluids and a separator unit consisting of one tube and two metal wires, each at the top and bottom of the tube. The effects of the following factors were observed: mean flow velocity U(o) (0.14-45 cm s(-1)), magnetic field strength micro(o)H(o) (0.125-0.50 T), wire size R(w) (0.125, 0.250 and 0.500 mm), wire length L(w) (2, 5 and 10 cm), wire materials (nickel, stainless steel 304 and 430) and tube size (outer radius R(o) = 0.30 mm and inner radius R(i) = 0.25 mm; R(o) = 0.50 mm and R(i) = 0.375 mm; and R(o) = 2.0 mm and R(i) = 1.0 mm). Our observations showed that the experimental results fit well with the corresponding theoretical results from the model we previously developed at a low flow velocity area (for example, U(o) < or = 20 cm s(-1)), strong external magnetic field (for example, > or = 0.30 T) and long wire length (for example, L(w) = 10 cm). The experimental results also showed that more than 90% capture efficiency is indeed achievable under moderate systemic and operational conditions. Pressure drop measurements revealed that the device could work well under human physiological and clinical conditions, and sphere buildup would not have any considerable effect on the pressure drop of the device. The breakthrough experiments demonstrated that a lower flow rate V, higher applied magnetic field micro(o)H(o) and diluted sphere suspension, i.e. lower C(o), would delay the breakthrough. All the results indicate the promise of this portable magnetic separator device to efficiently in vivo sequestrate nano-/micro-spheres from blood flow in the future magnetically based detoxification system.

Three-dimensional modeling of a portable medical device for magnetic separation of particles from biological fluids.

A portable separator has been developed to quantitatively separate blood-borne magnetic spheres in potentially high-flow regimes for the human detoxification purpose. In the separator design, an array of biocompatible capillary tubing and magnetizable wires is immersed in an external magnetic field that is generated by two permanent magnets. The wires are magnetized and the high magnetic field gradient from the magnetized wires helps to collect blood-borne magnetic nano/micro-spheres from the blood flow. In this study, a 3D numerical model was created and the effect of tubing-wire configurations on the capture efficiency of the system was analyzed using COMSOL Multiphysics 3.3(R). The results showed that the configuration characterized by bi-directionally alternating wires and tubes was the best design with respect to the four starting configurations. Preliminary in vitro experiments verified the numerical predictions. The results helped us to optimize a prototype portable magnetic separator that is suitable for rapid sequestration of magnetic nano/micro-spheres from the human blood stream while accommodating necessary clinical boundary conditions.

Synthesis and characterization of highly-magnetic biodegradable poly(d,l-lactide-co-glycolide) nanospheres.

The objective of this study was to develop high magnetization, biodegradable/biocompatible polymer-coated magnetic nanospheres for biomedical applications. Magnetic spheres were prepared by a modified single oil-in-water emulsion-solvent evaporation method utilizing highly-concentrated hydrophobic magnetite and poly(d,l lactide-co-glycolide) (PLGA). Hydrophobic magnetite prepared using oleic acid exhibited high magnetite concentrations (84 wt.%) and good miscibility with biopolymer solvents to form a stable oily suspension. The oily suspension was then emulsified within an aqueous solution containing poly(vinyl alcohol). After rapid evaporation of the organic solvent, we obtained solid magnetic nanospheres. We characterized these spheres in terms of external morphology, microstructure, size and zeta potential, magnetite content and distribution within the nanospheres, and magnetic properties. The results showed good encapsulation where the magnetite distorted the smooth surface morphology only at the highest magnetite concentrations. The mean diameter was 360-370 nm with polydispersity indices of 0.12-0.20. We obtained high magnetite content (40-60%) and high magnetization (26-40 emu/g). The high magnetization properties were obtained while leaving sufficient polymer to retain drugs making these biodegradable spheres suitable as a potential platform for the design of magnetically-guided drug delivery and other in vivo biomagnetic applications.