Title:
Method And Apparatus For Continuous Removal Of Submicron Sized Particles In A Closed Loop Liquid Flow System
Kind Code:
A1


Abstract:
A method and apparatus for continuous removal of submicron sized artificial oxygen carriers (rAOC) and other materials such as cancer cells and bacteria from blood and other liquids. A centrifuge rotor having a curved shape is offset on a spinning rotor base and creates contiguous areas of low to high centrifugal force depending on the distances from the axis of the rotor base. This creates a density gradient field that separates materials of different densities input to the centrifuge that exit via different outputs. A monitor detects any red blood cells (RBC) with the rAOC before they exit the centrifuge. If there are any RBC detected logic circuitry changes the speed of rotation of the rotor, and the flow rate of pumps inputting and removing separated blood and rAOC to and from the centrifuge until there are no RBC in the rAOC exiting the centrifuge.



Inventors:
Ostafin, Agnes (Layton, UT, US)
Mizukami, Hiroshi (Pasadena, CA, US)
Application Number:
13/322790
Publication Date:
03/29/2012
Filing Date:
08/24/2010
Assignee:
OSTAFIN AGNES
MIZUKAMI HIROSHI
Primary Class:
Other Classes:
494/10, 494/60, 494/68
International Classes:
B04B13/00; B04B7/04; B04B7/12; B04B15/00
View Patent Images:



Primary Examiner:
CLEVELAND, TIMOTHY C
Attorney, Agent or Firm:
PEACOCK LAW P.C. (201 THIRD STREET, N.W. SUITE 1340, ALBUQUERQUE, NM, 87102, US)
Claims:
1. A rotor for a centrifuge used to separate components having different densities from a mixture of the components, the rotor comprising: a rotor base having a central axis and the rotor base is rotated about the central axis when the centrifuge is in use; a first rotor element that is curved and is attached to and has an orientation extending away from the rotor base, the first rotor element having a first end and a second end; and a second rotor element that is curved and is attached to and has an orientation extending away from the rotor base, the second rotor element having a first end and a second end, the second end of the first rotor element being connected to the first end of the second rotor element to form a composite rotor element; wherein the composite rotor element is positioned on the rotor base so that the first end of the first rotor element and the second end of the second end of the second rotor element are at different distances from the central axis.

2. The centrifuge rotor of claim 1 further comprising: a centrifuge housing in which the composite rotor element on the rotor base is mounted and is rotated; a first output port through the sidewall of the centrifuge housing for removing a first component of the mixture of components input to the centrifuge housing; a second output port through the sidewall of the centrifuge housing for removing a second component of the mixture of components input to the centrifuge housing, the spacing between the first and second output ports being substantially the same spacing as the spacing between the first end of the first rotor element and the second end of the second rotor element; an input port through the sidewall of the centrifuge housing through which the mixture of components is input to the centrifuge housing, said input port being closer to the second end of the second rotor element than to the first end of the second rotor element which is connected to the second end of the first rotor element to form the composite rotor element.

3. The centrifuge rotor of claim 2 wherein when the rotor base with composite rotor element mounted thereon is rotated inside the centrifuge housing the orientation of the composite rotor element on the rotor base creates a density gradient that separates two components of the mixture of components that is input to the centrifuge housing, where the two components have different densities, and a first of the two components moves in a first direction inside the centrifuge housing and is removed from the centrifuge housing at the first output port while a second of the two components moves in a second, opposite direction inside the centrifuge housing and is removed from the centrifuge housing at the second output port.

4. The centrifuge rotor of claim 3 further comprising: a monitor port through the sidewall of the centrifuge housing, the monitor port being closer to the second output port at the second end of the second rotor element than the input port is, the monitor port being used to extract a sample of the second of the two components moving toward the second output port, the sample being used to determine if the first of the two components has been separated from the second component.

5. The centrifuge rotor of claim 4 further comprising: an outwardly extending end at the first end of the first rotor segment and at the second end of the second rotor segment, wherein as the rotor turns inside the centrifuge housing these two ends create a pressure pushing the first component of the mixture of components toward the first output port and pushing the second component of the mixture of components toward the second output port.

6. The centrifuge rotor of claim 5 further comprising: a sensor connected to the monitor output port to monitor the sample of the second of the two components moving toward the second output port and extracted at the monitor port for the presence of any of the first of the two components, the sensor generating an output signal if any of the first of the two components is present; and electronics receiving the output signal from the sensor, the electronics causing a change in the rate at which the first of the two components is removed from the centrifuge at the first output port, and changing the rate at which the second of the two components is removed from the centrifuge at the second output port to eliminate the presence of any of the first of the two components in the sample taken at the monitor output port, thus assuring there is none of the first of the two components present with the second of the two components exiting the centrifuge at the second output port.

7. The centrifuge rotor of claim 6 wherein the electronics also causes a change in the rate at which the mixture of components is input to the centrifuge housing to assure there is none of the first of the two components present with the second of the two components exiting the centrifuge at the second output port.

8. The centrifuge rotor of claim 2 further comprising: a monitor port through the sidewall of the centrifuge housing, the monitor port being closer to the second output port at the second end of the second rotor element than the input port is, the monitor port being used to extract a sample of the second of the two components moving toward the second output port, the sample being used to determine if the first of the two components has been separated from the second component.

9. The centrifuge rotor of claim 8 further comprising: an outwardly extending end at the first end of the first rotor segment and at the second end of the second rotor segment, wherein as the rotor turns inside the centrifuge housing these two ends create a pressure pushing the first component of the mixture of components toward the first output port and the second component of the mixture of components toward the second output port.

10. The centrifuge rotor of claim 9 wherein when the rotor base with composite rotor element mounted thereon is rotated inside the centrifuge housing the orientation of the composite rotor element on the rotor base creates a density gradient that separates two components of the mixture of components that is input to the centrifuge housing, where the two components have different densities, and a first of the two components moves in a first direction inside the centrifuge housing and is removed from the centrifuge housing at the first output port while a second of the two components moves in a second, opposite direction inside the centrifuge housing and is removed from the centrifuge housing at the second output port.

11. The centrifuge rotor of claim 4 further comprising: a sensor connected to the monitor output port to monitor the sample of the second of the two components moving toward the second output port and extracted at the monitor port for the presence of any of the first of the two components, the sensor generating an output signal if any of the first of the two components is present; and electronics receiving the output signal from the sensor, the electronics causing a change in the rate at which the first of the two components is removed from the centrifuge at the first output port, and changing the rate at which the second of the two components is removed from the centrifuge at the second output port to eliminate the presence of any of the first of the two components in the sample taken at the monitor output port, thus assuring there is none of the first of the two components present with the second of the two components exiting the centrifuge at the second output port.

12. The centrifuge rotor of claim 11 wherein the electronics also causes a change in the rate at which the mixture of components is input to the centrifuge housing to assure there is none of the first of the two components present with the second of the two components exiting the centrifuge at the second output port.

13. The centrifuge rotor of claim 12 wherein when the rotor base with composite rotor element mounted thereon is rotated inside the centrifuge housing the orientation of the composite rotor element on the rotor base creates a density gradient that separates two components of the mixture of components that is input to the centrifuge housing, where the two components have different densities, and a first of the two components moves in a first direction inside the centrifuge housing and is removed from the centrifuge housing at the first output port while a second of the two components moves in a second, opposite direction inside the centrifuge housing and is removed from the centrifuge housing at the second output port.

14. A rotor for a centrifuge used to separate whole blood from other artificial blood having a density higher than any of the components of the whole blood, the rotor comprising: a rotor base having a central axis and the rotor base is rotated about the central axis when the centrifuge is in use; a first rotor element that is curved and is attached to and has an orientation extending away from the rotor base, the first rotor element having a first end and a second end; and a second rotor element that is curved and is attached to and has an orientation extending away from the rotor base, the second rotor element having a first end and a second end, the second end of the first rotor element being connected to the first end of the second rotor element to form a composite rotor element; wherein the composite rotor element is positioned on the rotor base so that the first end of the first rotor element and the second end of the second end of the second rotor element are at different distances from the central axis.

15. The centrifuge rotor of claim 14 further comprising: a centrifuge housing in which the composite rotor element on the rotor base is mounted and is rotated; a first output port through the sidewall of the centrifuge housing for removing the whole blood from the artificial blood input to the centrifuge housing; a second output port through the sidewall of the centrifuge housing for removing the higher density artificial blood input to the centrifuge housing along with the whole blood, the spacing between the first and second output ports being substantially the same spacing as the spacing between the first end of the first rotor element and the second end of the second rotor element; an input port through the sidewall of the centrifuge housing through which the mixture of whole blood and artificial blood is input to the centrifuge housing, said input port being closer to the second end of the second rotor element than to the first end of the second rotor element which is connected to the second end of the first rotor element to form the composite rotor element.

16. The centrifuge rotor of claim 15 wherein when the rotor base with composite rotor element mounted thereon is rotated inside the centrifuge housing the orientation of the composite rotor element on the rotor base creates a density gradient that separates the whole blood from the artificial blood where the components of the whole blood have a lower density than the artificial blood, and a first of the whole blood moves inside the centrifuge housing toward and is removed from the centrifuge housing at the first output port while the artificial blood moves inside the centrifuge housing toward and is removed from the centrifuge housing at the second output port.

17. The centrifuge rotor of claim 16 further comprising: a monitor port through the sidewall of the centrifuge housing, the monitor port being closer to the second output port at the second end of the second rotor element than the input port is, the monitor port being used to extract a sample of the artificial blood moving toward the second output port, the sample being used to determine if the whole blood has been completely separated from the artificial blood.

18. The centrifuge rotor of claim 17 further comprising: an outwardly extending end at the first end of the first rotor segment and at the second end of the second rotor segment, wherein as the rotor turns inside the centrifuge housing these two ends create a pressure pushing the whole blood toward the first output port and the artificial blood toward the second output port.

19. The centrifuge rotor of claim 18 further comprising: a sensor connected to the monitor output port to monitor the sample of the artificial blood moving toward the second output port and extracted at the monitor port to test for the presence of any whole blood components, the sensor generating an output signal if any of the first of the two components is present; and electronics receiving the output signal from the sensor, the electronics causing a change in the rate at which the first of the two components is removed from the centrifuge at the first output port, and changing the rate at which the second of the two components is removed from the centrifuge at the second output port to eliminate the presence of any of the first of the two components in the sample taken at the monitor output port, thus assuring there is none of the first of the two components present with the second of the two components exiting the centrifuge at the second output port.

20. The centrifuge rotor of claim 19 wherein the electronics also causes a change in the rate at which the mixture of whole blood and artificial blood is input to the centrifuge housing to assure there is none of the whole blood components present with the artificial blood exiting the centrifuge at the second output port.

Description:

This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 61/236,810 , filed on Aug. 25, 2009.

Field of the Invention

The present invention relates to a method and apparatus for continuous removal of submicron sized particles from blood or other liquids.

BACKGROUND OF THE INVENTION

In the prior art there are a range of particulate carriers intended for the controlled delivery of biologically active substances within the body. Their sizes range from micron to submicron, and their compositions range from organic (e.g. polymers, lipids, surfactants, proteins) to inorganic (calcium phosphate, silicate, CdSe, CdS, ZnSe, gold and others). Each of these particulate carriers are designed to carry a chemically or biochemically reactive substance, and either release it over time, or at a specific location, or both.

The size of the individual particulate carriers and their load capacity is controlled by the amount of material used in the synthesis, the morphology by which the components assemble, and the specific composition of the components. The synthesized particulate carriers have the dual function of being able to solubilize or to be able to bind to the chemically or biochemically reactive substances intended for ultimate delivery. The underlying assumption is that the enclosed reactive substances will ultimately be released so that they can perform their intended functions. The particulate carriers themselves usually do not participate in the release function, except to the extent that they regulate the timing or location of release of the reactive substances they carry, and the carrier components must either decompose over time, or remain as non-active and non-toxic substances that do not cause any harm.

In the field of medicine such particulate carriers have been used to serve as artificial oxygen carriers (AOC) in artificial blood products. Artificial blood is a product made to act as a substitute for red blood cells which transport oxygen and carbon dioxide throughout the body. However, the function of real blood is complicated, and the development of artificial blood has generally focussed on meeting only a specific function, gas exchange - oxygen and carbon dioxide.

Whole blood serves many different functions that cannot be duplicated by an AOC. Artificial blood mixable with autologous blood can support patients during surgery and support transfusion services in emerging countries with limited healthcare, blood donations and storage facilities, or high risk of exposure to disease since screening procedures are too expensive. An AOC is a blood substitute, which is not dependent upon cross matching and blood-typing would mean no delay in blood availability, and could mean the difference between life and death of patients. In prior art medical applications the residual materials from particulate carriers are expected to be metabolized and/or excreted over time. However, the disposal of particulate carriers with natural metabolism of the patients is extremely difficult.

Another motivation for developing improved AOC is that despite significant advances in donated blood screening there are still concerns over the limited shelf life which is 42 days at 2°-6° C.

In the era of modern science, several decades of extensive academic, industry research efforts, clinical trials, and spending multiple billions of dollars, has led to two major classes of AOCs, namely emulsified perfluorocarbons (PFC) and polymeric hemoglobins (Hb). While these two types of AOCs each have some advantages, none are yet approved for clinical use in the U.S.

Chemically and biologically inert, emulsified, sterilized perfluorocarbons (PFCs) are stable in storage at low temperatures 2-5° C. for over a year. Further, PFCs are relatively inexpensive to produce and can be made devoid of any biological materials eliminating the possibility of spreading an infectious disease via a blood transfusion. Because they are not soluble in water they must be combined with emulsifiers able to suspend tiny droplets of PFC in the blood. In vivo the perfluorocarbon is ultimately expelled via the lungs after digestion of the emulsifier by the macrophage/monocyte system. In addition, PFCs are biologically inert materials that can dissolve about fifty times more oxygen than blood plasma but less oxygen than red blood cells. For instance, a mixture consisting of 70% blood and 30% perfluorocarbon by volume can provide the needed 5 ml of oxygen per 100 ml of blood if the partial pressure of oxygen in the lungs can be increased to 120 mm Hg by having the patient breath air with an oxygen partial pressure of approximately 180 mm Hg.

Perfluorocarbons (PFC) dissolve more oxygen than water, but still less than normal blood. To supply the needed amount of oxygen in circulation, patients may require supplemental oxygen. Highly hydrophobic PFC requires emulsifiers to stabilize the droplet in blood. These emulsifiers interact with proteins and emulsifiers found in blood leading to instability. As a result, large quantities of PFC in circulation in the blood cannot be tolerated. Small amounts of PFC escape from the blood into the lungs where it is vaporized and breathed out. Large amounts of PFC and emulsifier can have a negative effect on lung function.

Crosslinked, polymerized or encapsulated hemoglobin (pHb) based artificial oxygen carriers (AOC) are late-comers compared with perfluorocarbon based AOCs described in previous paragraphs, and are attracting increasing attention because their oxygen delivery characteristics are similar to that of the red blood cells (hereinafter referred to as RBC).

Polymeric hemoglobins (pHb) bind O2 and CO2, with a binding mechanism much like that of red blood cells (RBC), but even a small quantity of unpolymerized Hb left in the circulation can become very toxic. As an artificial oxygen carrier (AOC), a large amount of pHb needs to be injected into a person. Premature breakdown can increase the risk of toxicity, and such a large amount can overtax the body's natural removal processes. Polymerized Hb remains costly. Animal sources of Hb run the risk of transferring, among other things prion-based diseases. Recombinant Hb is a promising approach. It requires high quality separation and purification procedures, that add to the cost.

While both polymeric hemoglobins (Hb) and perfluorocarbons (PFC) based AOC products deliver oxygen in significant quantities to cells and tissue, their side effects, such as nitric oxide related vasoconstriction, stroke, cardiac arrest, flu-like symptoms and long term chemical toxicity, have forced the termination of all the clinical trials in the U.S. An all out effort to reduce the toxicity of relatively large quantity of AOC injected into a body by metabolic decompositions has failed.

In view of the many problems experienced with artificial blood products and particulate carriers intended for the controlled delivery of biologically active substances within the body, particulate artificial oxygen carriers (AOC) have been developed that minimize the above described problems in the prior art with non-particulate AOCs. The particulate AOCs are designed to be continually circulated in a closed loop fluid circulation system, are less subject to turbulent breakup, chemical decomposition, or accumulation of debris, and are capable of exchange of small ions and gases.

However, while particulate AOC artificial oxygen carriers minimize the problems of earlier AOCs that are described above, they break down in time in the blood so there is a need in the art for a way to remove them from the body after they have served their purpose as an artificial oxygen carrier.

SUMMARY OF THE INVENTION

The need in the prior art described in the previous paragraph is satisfied by the present invention. To satisfy the above listed need in the prior art the present invention is a specialized centrifugal rotor that utilizes density gradient separation to efficiently remove particulate artificial oxygen carriers (hereinafter referred to as retrievable AOCs or rAOC) from blood or other biofluids. In addition, the rAOC is retrieved from a patients system as soon as its medical purpose is accomplished in order to alleviate the physiological stress on already compromised patients.

With the present invention the particulate rAOCs can be retrieved at any desired time using continuous flow separation employing density-gradient centrifugation, which may be supplemented with magnetic fields, affinity filtration or other methods, without suffering damage, or inflicting damage on other materials that may already be present in the flowing fluid.

Other applications for the present invention include removal and concentration of metastatic cancer cells from circulating blood, retrieval of low copy mammalian, bacterial or virus cells, and tissue and organ imaging. Depending on the application, the specific design requirement of these materials in terms of their size and composition may vary, but common to all of them are the properties summarized earlier, and the tailored ability for continuous retrieval from circulating fluids using the methods listed in the previous paragraph.

To remove the carrier particles from the blood one or more of the following continuous flow separation methods may be used: (a) centrifugation, (b) magnetic fields, and/or (c) affinity filtration without suffering damage or inflicting damage on other materials that may already be present in the flowing fluid. It is contemplated that particulate rAOCs be removed from the bloodstream as soon as possible after they have performed their function, but prior to degradation of the particulate rAOCs, and subsequent development of detrimental side effects.

To meet the criteria for retrievability of the above described particulate rAOC particles of the present invention from blood during their use, the particulate material must be submicron sized (50 nm-700 nm) hollow particles filled with a high density perfluorocarbon (PFC) and/or a poly hemoglobin (pHb) liquid. The hollow particles have one or two rigid reinforcing shells. The exterior surface of these particulate shells are coated with molecules containing exposed functional groups (COOH, NH2, SH etc.) convenient for the crosslinking of either more than one particle, or proteins like antibodies, cell receptor targets, polyhemoglobin, hemoglobin etc.

The single shell coated emulsion particles (rAOC) of the present invention have a higher density than other components of blood such as red blood cells, white blood cells and plasma. Accordingly, centrifugal forces may be utilized to separate the particles from other blood components, but density gradient is used rather than a sedimentation velocity method as in the prior art. In the prior art red blood cells are the furthest moving particles in a centrifugal field, but with the present invention the novel AOC is the furthest moving particles in the centrifugal field. With the AOC being the furthest moving particles in a centrifugal field they may be separated from all other blood components.

rAOCs in the blood have a higher density than the blood and are separated therefrom by continuous flow density gradient centrifugation that utilizes the higher density of the rAOC particles to accomplish their separation. Affinity filtration may also be used to separate the rAOC nano or sub-nano size particles from the blood.

In addition, paramagnetic materials may be added to the higher density PFC in each nanoparticle, and the magnetic susceptibility is used for the retrieval of the polymerized hemoglobin. The flowing liquid containing paramagnetic and diamagnetic materials (the natural blood component) must be exposed to a magnetic field during the centrifugal separation so that they will deviate in the direction of the flow of particles with paramagnetic materials away from the diamagnetic particles, thus making it possible to separate and collect both types of particles.

Description of the Drawing

The invention will be better understood upon reading the following Detailed description in conjunction with the drawings in which:

FIG. 1 is a perspective view of the novel centrifuge that utilizes density gradient separation to efficiently remove particulate artificial oxygen carriers from blood or other biofluids;

FIG. 2 is a top view of the novel centrifuge that better shows the novel rotor used in the centrifuge;

FIG. 3 is a linear graphical representation of the novel rotor of the centrifuge;

FIG. 4 is a block diagram of the circuits required for operation of the novel centrifuge that utilizes density gradient separation to efficiently remove particulate artificial oxygen carriers from blood or other biofluids;

FIGS. 5A and 5B are transmission electron microscope images of submicron sized blood substitutes optimized for use with the described invention;

FIG. 6 is a cross sectional diagram showing how a single shelled rAOC is constructed; and

FIG. 7 is a cross sectional representation of a double shelled, dual core oxygen carrier (DCOC) that wraps a PFC emulsion core wrapped with a first shell on the outside of which is PolyHB that is wrapped with a second shell; and

DETAILED DESCRIPTION

Prior art coated particulate carriers intended for the controlled delivery of biologically active or medicinal substances within the body, or to serve as artificial oxygen carriers (AOC), break down in time in the blood so there is a need in the art for a way to remove them from the body after they have served their purpose. Hereinafter, only AOC are specifically mentioned but the teaching also applies to particulate carriers intended for the controlled delivery of biologically active or medicinal substances within the body.

To meet the criteria for coated/particulate artificial oxygen carriers that can be temporarily substituted for blood, and for the retrievability of such coated AOCs (hereinafter referred to only as retrievable rAOC) from blood using the present invention, the rAOCs described herein are particulates having shells 12 (see FIGS. 5A and 5B) that must be submicron sized (50-1000 nm) hollow particles around a high density perfluorocarbon (PFC) emulsified nanoparticle. The reinforcing shell 12 is rigid and consists of a combination of lipids and inorganic materials like calcium phosphate, silicate, or biocompatible organic polymers such as, but not exclusively: polycaprolactone, polylactic acid, polyglycolic acid, polyethylene oxide, chitosan or chondroitin. The rAOCs nanoemulsion core particles 11 are denser than blood and the higher density is used to retrieve them from blood using a special centrifuge. Such shelled rAOCs are shown in and described very briefly with reference to FIGS. 5, 6, and 7.

Simply, the novel means of the present invention for removing such rAOCs from blood comprises having a novel centrifuge rotor 24 that creates a density gradient that separates the rAOCS from the blood. In the prior art separation of mixed components is based sedimentation velocity. This is possible because the density of rAOC is 1.98 g/ml, while the density of most of the blood components are only slightly over 1.0 g/ml. A mixture of blood and rAOCs withdrawn from the body are input to a specific point in the centrifuge where the rotation of the centrifuge rotor 24 causes the blood to flow in one direction and the rAOCs to flow in the opposite direction, and they are both removed from the centrifuge. Before the separated rAOCs are retrieved a sample of the rAOC flow is removed from the centrifuge and input to a red blood cell (RBC) sensor which looks for any red blood cells. If any red blood cells are detected electronics of the system adjusts the speed of the pumps inputting and removing the RBC and rAOC from the centrifuge until no RBC are detected in the rAOCs to be removed from the centrifuge. In addition, the rotational speed of the novel rotor inside the centrifuge may also be adjusted. This is shown in and described hereinafter in greater detail with reference to FIG. 4.

FIG. 1 is a perspective view of the novel centrifuge rotor 24 that utilizes density gradient separation to efficiently remove particulate artificial oxygen carriers (rAOC) from blood (RBC) or other biofluids. The case of the centrifuge and input and output ports therethrough are not shown in FIG. 1 to make the drawing simpler so the invention can be better understood. Rotor 24 comprises a circular rotor base 25 that is mounted on an axis 27 to a motor driven shaft (not shown). As shown in FIG. 1 rotor base 25 is rotated in a counter clockwise direction for the rotor 24 configuration shown and described herein. This direction is important, based on the arrangement of rotor elements 26a and 26b and their position on rotor base 25, to create a density based gradient that separates RBC (output at port 29) from the rAOC (output at port 28) from a mixture of RBC and rAOC that is input to the centrifuge at port 31. Distances d3, d4 and dr are shown in all of FIGS. 1, 2 and 3 to better understand how the Figures relate to each other. The thickness of rotor 26a,26b is 0.5 cm, the width is 2 cm, and the length is 15 cm, and the volume of the rotor will be only 15 ml.

Rotor 24 is made up of two curved elements 26a and 26b that are joined together to form a curved element 26a,26b that is oriented perpendicular to rotor base 25. The curvature of element 26b is slightly larger than the curvature of element 26a, and curved composite element 26a,26b is offset on rotor base 25 as may be seen in FIG. 1, but is better seen in the top view of FIG. 2. In FIG. 1 the far left end and the far right end of curved element 26a,26b curve outward a small amount to direct the flow of separated whole blood to output port 29 and to direct the separated/retrieved rAOC to output port 28 where they exit the centrifuge via their respective ports 28, 29 (not shown) through the case wall (not shown) of the centrifuge. The different curvatures of elements 26a and 26b and the position of the composite curved element 26a,26b on rotor base 25 create differing distances d3, d4 and dr in FIG. 1 where d4>dr>d3. These distances are shown in FIGS. 1, 2 and 3 to help understand rotor 24 in all the Figures. As shown in FIGS. 1, 2 and 3 a mixture of whole blood (RBC) and AOCs is typically extracted from a body (not shown) and is input to the centrifuge at input port 31. As mentioned above the length of rotor 26a,26b is 15 cm but the separation capacity per unit time could be increased by enlarging the width of the rotor 26a,26b to greater than 2 cm. In an alternative embodiment of the invention the curvatures of rotor segments 26a and 26b may be the same.

FIG. 2 is a top view of the novel rotor 24 used in a centrifuge. As previously mentioned the different curvatures of rotor elements 26a and 26b and the offset of composite rotor element 26a,26b on rotor base 25 are best seen in FIG. 2. More particularly, rotor 26a,26b being belt shaped in the general shape of an ellipsoid with overlapping ends. With rotor 26a,26b being off centered on base 25 regions of high, medium and low centrifugal force are created depending on the distances from the axis of rotation 27. As previously mentioned the far left end and the far right end of curved composite element 26a,26b curve outward a small amount to direct the flow of separated whole blood (RBC) to output port 29 and to direct the separated/retrieved rAOC to output port 28 where they exit the centrifuge via their respective ports 28, 29 (not shown) through the case wall (not shown) of the centrifuge. The curvature of composite rotor element 26a,26b and its position on rotor base 25 is best seen in this Figure. Input 31 where the composite mixture of RBC and rAOC is input to the centrifuge is offset from the junction of rotor elements 26a and 28b and is closer to rAOC output port 28 by a circumferential distance “x” as shown. The reason for this is described further in this Detailed Description. The other input and output ports have been previously described with reference to FIG. 1 so the description is not repeated here. While two rotor segments are shown in FIGS. 1 and 2, in alternative embodiments of the invention there may be more than two rotor segments.

FIG. 3 is a linear graphical representation of the novel rotor 24 of the centrifuge. This Figure shows how the distance between the face of composite rotor elements 26a,26b and the axis of rotation 27 of rotor 24 changes. Thus, the magnitude of centrifugal force at different regions of rotor 24 are depicted by the distance from the axis of rotation 27, which is stretched and shown as the dotted line at the top of FIG. 2. The distances d3, d4 and dr are shown in all of FIGS. 1, 2 and 3 to better understand how the Figures relate to each other. The rate of change in distance is basically linear except where rotor element 26a meets rotor element 26b. This is due to the fact the curvature of element 26a is different than the curvature of element 26b. In alternative embodiments of the invention the rate of change in distance may be uniform, and in another alternative embodiment the rate of change may be non-linear. Distances d3, d4 and dr between the face of rotor element 26a,26b and axis 27 are shown to link FIG. 3 with FIGS. 1 and 2. The input port 31 and output ports 28, 29 and 30 and their relative position with respect to the linear depiction of rotor 24 is shown.

Whole blood including rAOCs obtained from a person who is connected in a closed loop system with a density gradient centrifuge is input to the centrifuge at input port 31. The whole blood is separated from the rAOC because the density of the rAOCs is greater than the density of the whole blood and any of its individual components. The whole blood is output at output port 29 and is returned to the person from whom the blood and rAOCs was withdrawn. The rAOCs are output at port 28 and stored for future use or disposal. In addition, at a particular location near where the rAOCs exit the centrifuge via rAOC output port 28, a small sample is removed from the density gradient centrifuge and exits the centrifuge at monitor output port 30. The sample is input to a red blood cell sensor 32 of a control circuit 38 to be checked for the presence of any remaining red blood cells (RBC) with the rAOCs about to exit the centrifuge. This is better shown in and described with reference to FIG. 4. If any RBC are detected control circuit 38 adjusts the speed of the blood and rAOC pumps 36 and 37 that are part of circuit 38 to permit the centrifuge to fully separate any remaining RBC from the rAOC before the rAOC reaches monitor output port 30. This feedback operation assures that only rAOCs exit rAOC output port 28.

The centrifugal field generated in the density gradient centrifuge as novel rotor 24 turns about its axis 27 (FIGS. 1 and 2) creates a density gradient field that changes between output ports 28 and 29. Depending on the shape of rotor elements 26a and 26b, how they are joined, and how they are positioned on rotor base 25 this density field may change uniformly or it may non-linearly. The result is that the lower density whole blood fraction is separated from the higher density rAOC fraction. In an alternative embodiment another output port may be added somewhere between output ports 28 and 29 to separate intermediate density fractions of blood. The separated whole blood and rAOC are withdrawn through their respective output ports as previously described. The whole blood collected may be subjected to further fractionation. For example, further fractionation may be used to separate platelets and white blood cells from the whole blood in a manner known in the art.

More particularly as novel rotor 24 turns the density gradient field it creates causes the less dense, faster moving fractions of whole blood to move toward whole blood output port 29 and the more dense rAOC, however, migrate toward an area of the chamber having the greatest centrifugal force. By selecting the proper fluid in flow and out flow rates through the centrifuge, the physical dimensions of the rotor, and the speed of rotation of the rotor in the centrifuge, faster moving cells and slower moving cells may be separately extracted from the separation chamber and subsequently collected. In this manner, white blood cells and platelets may be separated and subsequently collected in separate collect reservoirs. Therefore, the combination of density centrifugation and centrifugal elutriation provides methods of separating blood components based on both density and sedimentation velocity properties.

The basic design of the centrifuge rotor 26a,26b is a belt shaped semicircular rotor placed slightly off-centered from the axis of rotation as shown in FIGS. 1 and 2. FIG. 1 is a three dimensional view of the rotor 26a,26b on the spinning rotor base 25, and FIG. 2 is a top view of rotor 26a,26b on the spinning rotor base 25. In FIG. 3 the rotor 26a,26b is shown stretched out in a linear configuration to help show the location of the rotor on rotor base 25 with respect to axis of rotation 27.

The semicircular rotor 26a,26b consists of two curved segments 26a and 26b, one segment (26b) slightly more distanced from the axis of rotation 27 than the other segment (26a) and therefore experiencing higher centrifugal force, while the other segment (26a) is closer to the axis of rotation and therefore experiences less centrifugal force than segment (26b). A mixture of the blood and high-density particles (rAOC) enter the outer wall of the higher centrifugal force segment 26b as indicated as “Whole blood and rAOC input 31) in FIGS. 1, 2 and 3.

With reference to FIG. 3, as the centrifugation begins the rAOC of the input mixture 31 remain at the wall of the furthest out rotor segment 26b, as it is the most dense material and moves towards the higher centrifugal field. This is to the right in FIG. 3 and the output is indicated as “Flow of rAOC Fr”. In FIGS. 1 and 2 this is clockwise and the output is indicated as “rAOC output 28”. All the blood components move toward the left in FIG. 3 toward closer rotor segment 26a because their densities are smaller and they essentially float on top of the rAOC. In FIGS. 1 and 2 this is counterclockwise and the blood components output is indicated as “Whole blood output 29”.

More particularly, as the blood and rAOC continue to be injected into rotor 26a, 26b at input 31 (shown in FIGS. 1-3), the blood components move towards the lower centrifugal field while the rAOC move to the higher centrifugal field. The thickness of belt shaped rotor 24 is only 5 mm. The separation of the rAOC and blood is carried out very quickly and form layers based are density of the particles. With separation being accomplished quickly it is possible maintain the rate of rAOC and blood inflow sufficiently fast to make the process “continuous-flow density separation”. As mentioned above the rAOC leave the rotor at output 28 at the end of highest centrifugal force, while the blood components move leave the rotor at output 29 at the end of lowest centrifugal force. The semicircular rotor has a small offset, bend and protrusion near the junction of segments 26a and 26b to make the separation of rAOC from the blood complete. In FIGS. 1, 2 and 3 this indicated by the number 40, but offset 40 is best seen in FIGS. 2 and 3. More specifically, it is possible to enhance the change of centrifugal force by creating a protrusion at the site where distinctive separation of two layers is made, since their sedimentation coefficients are predominantly a function of (1−ρ/δ), the particulates will be positioned close to the outer wall of the rotor when the density equilibrium is established.

Near at the exit port 28 of the rAOC, there is a monitor output port 30, from which small samples are taken of the rAOC flowing toward its output 28 to test the purity of the rAOC. The testing of the rAOC is shown in and described with reference to FIG. 4. The purity of the rAOC might change slowly over time during centrifugal retrieval of the rAOC so the relative flow rates of pumps 36 and 37 must be adjusted to maintain the purity of the rAOC output at its port 28. The addition of all out-flows of the rAOC and blood should equal to the inflow of the blood and rAOC, i.e. Fbr=Fr+Fm+Fb.

In FIG. 4 is a block diagram of circuits required for successful operation of the novel centrifuge that utilizes density gradient separation to efficiently remove particulate artificial oxygen carriers (rAOC) from blood or other biofluids. The circuits first comprise a red blood cell (RBC) sensor 32 that receives the previously mentioned sample output from the centrifuge at monitor output 30. The concentration of any contaminating low density RBC in the sample taken at output 30 is detected spectrophotometrically. The output from RBC sensor 32 is amplified by amplifier 33 and is then input to two logic circuits 34 and 35. Circuits 34 and 35 are programmed to respond to any output from sensor 32 to provide output signals that will change the operation of pumps 36 and 37 which thereby can change either or both of the flow rate of lower density blood flowing out at blood output 29 and higher density rAOC flowing out at blood output 28. In addition, there can be a programmed logic circuit 38 that responds to the output from sensor 32 and, in cooperation with logic circuits 34 and 35, provides and output at 39 to the motor that rotates rotor 24 to change its rotational speed.

FIGS. 5 A&B shows typical electron microscope pictures of the shelled rAOC particles 11. The shells 12 of these novel rAOC particles 11 are coated with molecules containing exposed functional groups (COOH, NH2, SH etc.) convenient for the crosslinking of either more than one particle, or proteins like antibodies, cell receptor targets, polyhemoglobin, hemoglobin etc. Outer ring or shell 12 is a gas permeant calcium phosphate or polymer coating, while the interior is an oxygen carrying center containing a hemoglobin (HB) 13 nanoparticle and/or a perfluorocarbon (PFC) 14 nanoparticle.

Very briefly, single shell rAOCs 11 are made as follows. Nanoemulsion particles 13 are made from a mixture of perfluorooctylbromide (PFOB) 21, 1,2-dioleoyl-sn-glycero-phosphate (DOPA)22 and water, preferably by a stirring process, but other methods known in the art may be utilized.

The outer surface of the perfluorooctylbromide (PFOB) nanoparticles 11 has a surface of 1,2-dioleoyl-sn-glycero-phosphate (DOPA) 22 surrounding a nanomulsion particle 21. The uncoated (non-mineralized) nanoemulsion particles 13 have a negatively charged surface of PO3created by using phosphatidic acid to stabilize the nanoemulsion particles. Since the synthesis of nanoemulsion particles takes place under basic conditions, the surface charge density of the nanoemulsion is quite high with zeta potentials nearing −50 mV.

To coat the negatively charged nanoemulsions particles 13 they may be mixed with 2:00 μl of 0.1 M phosphoric acid solution. Next, a CaCl2 solution is added followed by a CEPA solution to coat the nanoemulsion particles and arrest further calcium phosphate deposition. In this process positively charged calcium ions from the phosphoric acid are attracted to the negatively charged PO3on the surface of the nanoemulsion particles 13 (DOPA) as shown in FIG. 6. The accumulation of calcium ions at the periphery of the nanoemulsion particles increases the local concentration past the stability point for calcium phosphate precipitation resulting in precipitation of calcium phosphate onto the nanoemulsion particles to form a shell. The finished shelled, particles function well as oxygen carriers in blood.

A second shell and second oxygen carrier may be added as shown in FIG. 7. First, Polylysine/Hb is deposited layer by layer onto the negatively charged carboxylated surface of the first shell made as described above. Then a mixture of perfluorocarbon (PFC) and Polyhemoglobin (PolyHB) is coated over the first shell and the same previously described method is used to place a second shell over the PFC and PolyHB. The second shell makes the rAOC particles tougher and even better able to withstand being retrieved from circulating blood using the continuous flow density gradient separation technique described above. The finished shelled, particles function well as oxygen carriers in blood.

The novel density gradient separation technique taught and claimed herein may be used to separate other mixtures of substances having different densities. It may be used to separate and remove metastatic cancer cells from circulating blood. It may also be used for retrieval of low copy mammalian, bacterial or virus cells from blood. It may also be used to remove materials added to blood to enhance tissue and organ imaging. Depending on the application, the specific design requirement of these materials in terms of their size and composition may vary, but common to all of them are the properties summarized earlier, and the tailored ability for continuous retrieval from circulating fluids.

While what has been described herein is the preferred embodiment of the invention it will be understood by those skilled in the art that numerous changes may be made without departing from the spirit and scope of the invention.