Patent Publication Number: US-11389810-B2

Title: Centrifuge rotor core with partial channels

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 15/599,722 filed on May 19, 2017, which claims the benefit of U.S. Application 62/338,563 filed on May 19, 2016, the entire contents of all of which are incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present disclosure is related to centrifuge rotor cores. More particularly, the present disclosure is related to centrifuge rotor cores having partial channels. 
     2. Description of Related Art 
     In the biological and chemical sciences, there is often a need to separate particulate matter suspended in a solution. In a biological experiment, for example, the particles typically are cells, subcellular organelles, viruses, virus like particles and macromolecules, such as DNA fragments. A centrifugation process is routinely used to perform the separation of these components from a solution. 
     One common centrifugation technique is tube rotor centrifugation, which employs a rotor that rotates or spins one or more tubes containing the one or more desired analytes for separation. While useful for separation of small volumes as may be needed for laboratory use during product development, the use of such tube rotor centrifugation techniques may not be considered to be rapid enough and/or to be cost effective enough for certain uses such as those common in a production environment. Thus, tube rotor centrifugation techniques have generally not proven to be easily scalable from the benchtop or lab environment to the production environment. 
     Another common centrifugation technique is continuous flow centrifugation, which employs a rotor and rotor core that rotates or spins as the desired analyte or analytes flow continually over a density gradient maintained within the rotor assembly. Such continuous flow centrifugation techniques can include various different process steps including, but not limited to static gradient loading, static gradient unloading, loading of an unmixed or discontinuous gradient, loading of a layered or step gradient, dynamic gradient loading, dynamic gradient unloading, loading of mixed or linear or continuous gradients, and any combinations thereof. 
     As disclosed in U.S. Publication No. 2003/0114289A1, which is incorporated herein in its entirety and is commonly owned by the Applicant of the present disclosure, continuous flow centrifugation can, in some instances, be configured for linear scalability, for separations of different volumes or quantities, e.g., from laboratory scale to pilot scale to industrial scale or from industrial scale pilot scales to laboratory scale, using the same or similar centrifugation systems. The method and apparatus allow the same centrifuge systems can be used for sedimentation processes of multiple scales while maintaining substantially the same separation characteristics for each process by, at least in part, interchanging different sized and configured rotor cores within the rotor housing. 
     It has been determined by the present disclosure that the rotor cores disclosed herein, which include a partial channel, provide enhancements and improvements to the prior art scalable continuous flow centrifugation. 
     SUMMARY 
     A rotor core is provided that has a plurality of partial channels, namely channels that extend less than an entire length of the rotor core. 
     A rotor assembly is provided that has an outer housing with a removable rotor core disposed therein. The rotor core has a plurality of partial channels, namely channels that extend less than an entire length of the rotor core. 
     A method for achieving a linear scale separation of particles of a product during centrifugation is provided. The method includes operating a centrifuge apparatus at certain predetermined parameters depending upon a product to be separated; placing a first rotor core in a rotor housing to define a first rotor assembly having a first volume capacity; rotating the first rotor assembly in the centrifuge apparatus and so as to achieve a first particle separation of the product; removing the first rotor core from the rotor housing and placing a second rotor core in the rotor housing to define a second rotor assembly having a second volume capacity; and rotating the second rotor assembly in the centrifuge apparatus so as to achieve a second particle separation of the product which is a linear scale with respect to the first particle separation. The first and second rotor cores have a common rotor length and each have a plurality of channels with a channel length. The channel length of at least one of the first and second cores being less than the common rotor length. Additionally, the channel length of the plurality of channels of the first rotor core is different than the channel length of the plurality of channels of the second rotor core. 
     The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of a centrifuge apparatus according to the present disclosure; 
         FIG. 2  is a sectional view of an exemplary embodiment of a rotor assembly according to the present disclosure; 
         FIG. 3  is a top perspective view of an exemplary embodiment of a rotor core according to the present disclosure; 
         FIG. 4  is a partially exploded view of the rotor core according of  FIG. 3 ; 
         FIG. 5  is a schematic view of a first exemplary embodiment of a flow path through the rotor core of  FIG. 3 ; 
         FIG. 6  is a schematic view of an alternate exemplary embodiment of a flow path through the rotor core of  FIG. 3 ; 
         FIG. 7  is a top perspective view of an alternate exemplary embodiment of a rotor core according to the present disclosure; 
         FIG. 8  is a view of the rotor core of  FIG. 7  illustrating flow channels; 
         FIG. 9  is a side view of the rotor core of  FIG. 7 ; 
         FIG. 10  is a sectional view of the rotor core of  FIG. 7 ; 
         FIG. 11  is a top perspective view of another alternate exemplary embodiment of a rotor core according to the present disclosure; 
         FIG. 12  is a view of the rotor core of  FIG. 11  illustrating flow channels; 
         FIG. 13  is a side view of the rotor core of  FIG. 11 ; 
         FIG. 14  is a sectional view of the rotor core of  FIG. 11 ; 
         FIG. 15  is a top perspective view of a prior art rotor core used to compare to the rotor core of  FIG. 11 ; 
         FIG. 16  is a graph comparing the performance of the rotor core as in  FIG. 11  and  FIG. 15 ; 
         FIG. 17  is a bottom perspective view of yet another alternate exemplary embodiment of a rotor core according to the present disclosure; 
         FIG. 18  is a top perspective view of the rotor core of  FIG. 17 ; and 
         FIG. 19  is a view of the rotor core of  FIG. 17  illustrating flow channels. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings and in particular with simultaneous reference to  FIGS. 1-4 , a centrifuge apparatus  10  according to the present disclosure is shown in use with an exemplary embodiment of rotor core  12  having a plurality of separation channels  14  defined therein. 
     Advantageously, rotor core  12  allows centrifuge apparatus  10  to be utilized in a process for separating components of a product sample in which the volume of the product sample can be scaled up or down while maintaining substantially the same selected separation parameters of the process or to enable one centrifuge to be used for multiple scale processes that do not necessarily need to be scaleable but should have a similar functioning process. 
     According to the present disclosure rotor core  12  has channels  14  with a channel length (C L ) that extends less than an overall length of the rotor core, referred to herein as a rotor length (R L ). Thus, rotor cores  12  of the present disclosure are referred to as having “partial channels”, namely having channels  14  that extends less than the entire length of the rotor core. In some embodiments, channel length (C L ) is between 5% and 90% of rotor length (R L ), preferably between 20% and 80%, with between 25% and 75% being most preferred, and any subranges between these ranges. 
     Exchanging a rotor core  12  having channels  14  of a first partial channel length (C L ) in centrifuge assembly  10  with a rotor core  12  having channels  14  of a second channel length (C L )—where the second channel length is longer or shorter than the first—allows different volumes of analyte or analytes to be processed in a linearly scaled essentially similar manner. 
     Rotor core  12  has channels  14  with a channel width (C W )—where the channel width (C W ) and channel length (C L ), as well as the number of channels, define the volume of the rotor core. Since the present disclosure provides rotor cores  12  having partial channels  14 , the channel width (C W ) is increased to provide the same volume as rotor cores having longer channels. Stated another way, by providing rotor cores  12  having channels  14  of partial or limited channel length (C L ), the rotor cores having increased or wider channel widths (C W ). As used herein, the channel width (C W ) is defined as a measurement of arc length of channel  14  at the outer diameter of rotor core  12 . 
     Without wishing to be bound by any particular theory, it is believed that rotor cores  12  of the present disclosure—that have partial channels  14 —provide increased stability of the separation gradient during rotation by centrifuge apparatus  10 . Simply stated, partial channels  14  of the present disclosure are shorter than the channels of the prior art and assuming a common channel volume, result in wider channels than those of the prior art. It is believed that the short, wide partial channels  14  of the present disclosure provide increased stability of the separation gradient during rotation by centrifuge apparatus  10 . 
     It is also believed that increased gradient stability provides an environment where the density gradient ‘profile’ can be retained for a substantially longer period of time and therefore allow for a process to be conducted where the analyte or analytes can be successfully collected and the gradient remain in an essentially similar profile as compared to each other. This means that the analyte or analytes accumulation and resolution of impurities remains essentially the same for either scale of operation hence they are of a linear scale. 
     In some embodiments, rotor core  12  has an aspect ratio of channel width (C W ) to channel length (C L ) from 10:1 to 1:10, preferably 1:1 to 1:10, more preferably from 1:1 to 1:5, with 1:1 to 1:3 being most preferred, and any subranges there between. 
     Centrifuge  10  includes a tank assembly within which is housed a drive motor  16  and a rotor assembly  18 . Drive motor  16  is used to spin rotor assembly  18  at speeds sufficient for separation of the desired analyte or analytes. 
     Rotor assembly  18  includes an outer rotor housing  20  with removable rotor core  12  positioned therein. Housing  20  includes a central portion  22  and a pair of end caps  24 ,  26 . At least one of end caps  24 ,  26  is selectively removable from central portion  22  so as to allow rotor core  12  to be inserted or removed from housing  20 . In some embodiments, one of end caps  24 ,  26  can be permanently connected to or integrally formed with the central portion  22 . 
     In some embodiments, centrifuge apparatus  10  can include a lift assembly  28  to raise one or more of drive motor  16  and the rotor assembly  18 . Additionally, centrifuge apparatus  10  can include a console assembly  30 , which is in communication with drive motor  16  and, when present, lift assembly  28  to control the respective functions thereof. 
     In this manner, rotor cores  12  having channels  14  of differing channel lengths (C L ) can be received in rotor assembly  18  and the rotor assembly can be installed in the centrifuge apparatus  10  to process—preferably in a linearly scalable manner—differing volumes of analyte or analytes. 
     In some embodiments, rotor assembly  18  includes an insert  32  at a first face  34  and/or a second face  36  of rotor core  12 . In the illustrated embodiment, insert  32  is removable in a bore  38  of rotor core  12  located by a pair of pins  40 , a spring  42 , and a seal or O-ring  44 . Spring  42  normally biases insert  32  upwards along pins  40  away from faces  34 ,  36 . In this manner, insert  32  can assist in seating rotor core  12  in housing  20  and end caps  24 ,  26  in a desired manner. 
     While rotor core  12  is illustrated in  FIG. 2  having insert  32  at both faces  34 ,  36 , it is contemplated by the present disclosure for the rotor core to have at least one of the inserts integrally formed therewith as illustrated in  FIGS. 5-6 . Without wishing to be bound by any particular theory, it is believed by the present disclosure that rotor core  12  having integral insert  32  at least at one of faces  34 ,  36 , improved flow through rotor assembly  18  by eliminating a region of reduced flow (i.e., dead leg) that can form around the insert. Although not illustrated, it is contemplated by the present disclosure for both inserts  32  to be integral to rotor core  12 . 
     A first exemplary embodiment of the flow path through rotor core  12  of  FIG. 3  is illustrated in  FIG. 5 , and an alternate, opposite flow path through the rotor core is illustrated in  FIG. 6 . 
     Rotor core  12  of  FIGS. 3-4 and 5-6  includes a flow path defined by an axial channel  44 , a plurality of radial channels  46 , the plurality of separation channels  14 , a plurality of face channels  48 , and, when insert  32  is present, a plurality of insert channels  50 . Preferably, the number of separation channels  14  is common with the number of radial and face channels  46 ,  48 . Of course, it is contemplated by the present disclosure for core  12  to not include insert  32  and here, the core includes any desired number of face channels  48  such as six or less channels, more preferably four channels. 
     As shown in  FIG. 5 , centrifuge apparatus  10  can be operated so that the flow of analyte or analytes through the flow path enters rotor core  12  at insert  32  proximate face  36 , passes axially through the rotor core via axial channel  44 , passes radially through the rotor core via radial channels  46 , and enters separation channels  14 . After passing through separation channels  14 , which include a density gradient, any unseparated analyte or analytes and/or flow through passes over face  34  via face channels  48 , then over insert  32  via insert channels  50  before exiting rotor assembly  18 . 
     Preferably, core  12  includes a port or opening  52  connecting radial channels  46  and separation channels  14  that includes a taper such that the port is wider at an interface with separation channels  14 . Without wishing to be bound by any particular theory, the taper of port  52 , when the flow path is as illustrated in  FIG. 5 , spreads the particles in the analyte or analytes across a greater area of the separation gradient, which can mitigate the impact of the particles on the gradient and maintain the separation performance (e.g., stability) of the gradient. Simply, it is believed that the momentum of the analyte or analytes and/or flow through traveling radially outward can physically disrupt or cut through the gradient in separation channels  14 . The taper of port  52  is believed to lessen this effect by spreading the momentum across a larger area of the gradient. 
     It should be recognized that radial channels  46  are illustrated as being perpendicular to an axis of rotation (A) of rotor core  12 . Of course, it is contemplated by the present disclosure for radial channels  46  to be angled with respect to a normal line (N) through the axis (A). For example, it is contemplated by the present disclosure for radial channels  46  to angled with respect to the normal line (A) by between ±30 degrees, more preferably between ±10 degrees, with ±5 degrees being most preferred, and any subranges there between. 
     Again without wishing to be bound by any particular theory, it is believed by the angle of radial channels  46  can be used to slow or reduce the momentum with which the analyte or analytes and/or flow through impacts the gradient in separation channels  14 . For example, the momentum flow through radial channels  46  of  FIG. 5  can be slowed by providing the radial channels with a downward angle with respect to normal line (A). 
     Conversely and as shown in  FIG. 6 , centrifuge apparatus  10  can be operated so that the flow of analyte through the flow path enters rotor core  12  at insert  32  proximate face  34 . Here the flow passes or analytes over insert  32  via insert channels  50 , passes over face  34  via face channels  48 , where the flow enters separation channels  14 . After passing through separation channels  14 , which include a centrifugation gradient, any unseparated analyte or analytes and/or flow through passes enters rotor core  12  via radial channels  46 , flows into radial channel  44 , and exits rotor core  12  at insert  32  at face  36 . 
     Referring now to  FIGS. 7 through 10 , another alternate embodiment of rotor core  112  is shown. Here, rotor core  112  has the same geometry and dimensions including rotor length (R L ) and channel width (C W ) as rotor core  12  shown in  FIGS. 3 through 6 . However, rotor core  112  has partial channels  114  with have a channel length (C L ) that results in a volume of rotor core  112  that is 100 ml. 
     Accordingly, it can be seen that use of rotor assembly  18  in centrifuge assembly  10  can be easily scaled, in a linear manner, by starting with the rotor core  12  of  FIGS. 3 through 6  that has a volume of 50 ml, then using the rotor core  112  of  FIGS. 7 through 10  that has a volume of 100 ml. 
     It should be recognized the present disclosure is illustrated above with respect to rotor cores  12  and  112 , which have three separation channels  14 ,  114 . Of course, it is contemplated by the present disclosure for rotor cores having any desired number of separation channels. 
     For example, and referring to  FIGS. 11 through 14 , another alternate embodiment of rotor core  212  is shown. Here, rotor core  212  includes six partial channels  214  with have a channel length (C L ) that is 25% of rotor length (R L ). Further, it is contemplated by the present disclosure for rotor core  212  to have any desired channel length (C L ) that less than rotor length (R L ). 
     Rotor core  212  of  FIGS. 11 through 14  has partial channels  214  and can be compared to the prior art rotor core  212 ′ shown in  FIG. 15 . Rotor core  212 ′ is commercially available from the Applicant under the tradename PK3-400. 
     For ease of comparison, rotor core  212  and rotor core  212 ′ have a common rotor volume of 400 ml. Here, rotor core  212  has partial channels  214  with channel length (C L ) that is less than the rotor length (R L ). By contrast, while the prior art rotor core  212 ′ has channels  214 ′ with a channel length (C L ) that is equal to the rotor length (R L )—namely lacks the partial channels of the present disclosure. As a result, channels  212  have a channel width (C W ) that is substantially wider than the channel width (C W ) of rotor core  212 ′ but have the same volume. 
       FIG. 16  is a graph comparing the performance of rotor core  212  to the performance of the prior art rotor core  212 ′. During the comparison test, rotor core  212  was configured with the flow direction illustrated in  FIG. 5 . The standardized parameters for both tests include use of a commercially available PKII ultracentrifuge, a rotor speed of 35,000 rpm, a separation gradient that includes 200 ml load volume of 55% w/w sucrose solution and 200 ml load volume of water. 
     As can be seen from  FIG. 16 , the gradient collected from both tests illustrate a collection that is considered, for the purposes of the present application, linear with respect to one another. Thus, the results of the comparison in  FIG. 16  illustrate linearity between the separation using the prior art rotor core  212 ′ that has full length channels  214 ′ and rotor core  212  that has the shorter, wider partial channels  214  according to the present disclosure. 
     More features of the partial channel rotor cores of the present disclosure are disclosed with respect to  FIGS. 17 through 19 . Rotor core  314  illustrates an example of radial channels  346  that are angled—by a positive angle—with respect to a normal line (A). 
     Rotor core  314  includes a tapered region  354  within channels  314 . Tapered region  354  can be used to provide further scalability to the volume of rotor core  314 . 
     In some embodiments, axial channels  346  have ports  352  at the interface with separation channels  314  that terminate in the tapered region. Additionally and without wishing to be bound by any particular theory, termination of ports  352  in tapered region  354  is believed to reduce or mitigate effects of momentum of the analyte or analytes and/or flow through on the gradient in channels  314 . 
     It should also be noted that the terms “first”, “second”, “third”, “upper”, “lower”, and the like may be used herein to modify various elements. These modifiers do not imply a spatial, sequential, or hierarchical order to the modified elements unless specifically stated. 
     While the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated, but that the disclosure will include all embodiments falling within the scope of the appended claims.