Patent Publication Number: US-9402390-B2

Title: Tissue retrieval, storage, and explant culture device for the derivation of stem cells

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to methods and apparatus for obtaining tissue samples from biological materials. 
     BACKGROUND 
     Within the normal reproductive process, the gestation of a fetus within the female of the species typically occurs within a gestational sac. The gestational sac is comprised of a pair of juxtaposed membranes comprising an outer structure, such as the chorionic membrane (chorion) that forms an outer margin, and an inner structure, such as the amniotic membrane (amnion) which is closest proximity to the fetus. In childbirth following partuation of the gestational sac, commonly referred to as afterbirth, the membrane structure is typically disposed as medical waste. However, medical discoveries are increasingly finding valuable biomedical materials in the tissues of these materials, and specifically the amnion. 
     The first known clinical uses of the amnion began a century ago for the treatment of various wounds including burn trauma and skin ulcerations on the surface. Extended usage of the intact amnion and chorion tissue came in the 1950&#39;s with more focused procedures to treat skin burn sites. The value of amnion was exemplified in the 1960&#39;s with a proposal to establish an amnion bank. 
     Contemporary medicine has seen a relative explosion in the utility of the amnion tissue in the areas of treatment for ocular disorders and thermal and chemical burns. In these treatments, intact amnion tissue is literally transposed directly over the trauma or wound site and has been proven to promote faster healing and alleviate pain. Today the most prevalent use of amnion tissue is in surgical procedures involving the eye. 
     Recent research is shifting the primary focus of medical attributes to the area of stem cell derivation. The concept of “Regenerative Medicine”, which is replacing, repairing and reconstructing diseased tissue and organs by stem cell therapies, is making rapid clinical progress. Multiple stem cell populations have been identified in the amnion and chorion. When derived at child birth, the benefits can be greater because of their pristine nature due to a lack of exposure to environmental toxins. Any or all derived stem cells may have future clinical utility and may play an extremely large and beneficial role in regenerative medicine. 
     An alternate and proven method of stem cell derivation in current practice today, and also practiced for the benefit of regenerative medicine, is that of harvesting the placental umbilical cord blood. By this practice, a single sample of blood is harvested from the umbilical cord at birth. The harvested blood is then processed to derive the appropriate beneficial stem cells and the sample is frozen for future use. The ability to cryogenically freeze living cells for thawing and renewal at a later time is a well proven and common practice for many biological materials and is commonly used for procedures such as in vitro fertilization of embryos implanted to induce pregnancy. Cord blood, amnion and chorion tissues are likewise proven biological materials that are conducive to being frozen for an unlimited time. The stem cells derived from cord blood are typically most appropriate for the treatment of hematopoietic (i.e., blood-related) illnesses, and the singular sample retrieved will typically be saved for the future benefit of the donor. By contrast, it has been found that amnion derived stem cells possess qualities that become quite beneficial for treatment of illnesses other than hematopoietic, such as skeletal and cardiovascular. Fundamentally, umbilical cord blood produces hematopoietic stem cells and amnion and chorion produce mesenchymal and epithelial stem cells, all of which are of growing benefit to the healthcare practice of regenerative medicine and are capable of being harvested and preserved for future benefit. 
     With the growing number of possible clinical applications for amnion and chorion, the devices and methods used to retrieve and preserve these tissues are of increasing interest to the health care community. As new procedures are developed, the devices must be adapted and may advantageously facilitate, optimize, and simplify retrieval and storage of amnion and chorion directly from the afterbirth. 
     SUMMARY OF THE DISCLOSURE 
     Devices and methods are disclosed for isolating biological materials and placing them in a position highly conducive to long term storage, thereby preserving the materials intact and preserving them for use by future generations. The benefits of banking and preserving these materials to aid in future medical procedures will only increase in time due to the technological advances in the healthcare industry. 
     According to some aspects of this disclosure, a device is provided for retrieving, capturing, transporting, and cryogenically storing tissue samples from biological material. In some applications, the device may be used to harvest and store amnion or chorion tissue samples. 
     Efficient retrieval and handling of amnion and chorion membranes is complicated by the physical characteristics of the membranes. The amnion and chorion membranes are typically extremely thin, possess a level of tensile attributes, but also exhibit a notch sensitive behavior which makes the membranes susceptible to tearing and subsequent curling up upon itself if not properly handled. Tearing and curling of the membranes can destroy cellular viability, and therefore may be deleterious to future clinical value. 
     Additionally, the amnion and chorion are living membranes when harvested at childbirth, and therefore they should be handled, transported, and preserved correctly to maximize the yield of living cells that are obtained and preserved for future use. Therefore, in addition to folding, or curling back upon itself, or any act whereby the tissue surface is touched by itself, or other capturing elements causing harmful effects, similar damage can be caused by allowing the membrane surface to dry. 
     In view of the foregoing, according to certain aspects of this disclosure a device may be provided having a working platform upon which to secure the membrane in a way that spreads it out straight, flat and secure. At birth, the amnion and chorion are intimately attached and therefore may require manual separation. In some embodiments, therefore, the methods and devices may secure a leading edge of one membrane (such as the amnion) on a platen while the membranes are separated. After separation, the entire amnion sample may remain on the platen. 
     The methods and devices disclosed herein may also create multiple smaller sub-samples from a single, larger sample. For example, a first or bottom platen assembly may be capable of being reconfigured into multiple sub-platen assemblies, so that a large sample provided on the bottom platen can be simply and efficiently separated into multiple sub-samples disposed on sub-platen assemblies. Generating multiple sub-samples from a single sample typically requires cutting or tearing of the tissue while simultaneously stabilizing the assembly so that it does not contract or curl upon itself. Accordingly, the methods and devices disclosed herein may include a second or top platen assembly configured to retain the straight and flat nature of each individual sub-sample both prior to and after separation. The top platen assembly is positioned over the bottom platen assembly, and guides are provided to consistently and accurately locate and mates the top and bottom platens with the tissue disposed therebetween, all while facilitating separation into multiple sub-assemblies carrying sub-samples at a later time, such as prior to cryogenic storage. 
     According to additional aspects of the present disclosure, the methods and devices disclosed herein may further provide a liquid containment of the mated top and bottom platens to preserve the sample as it is transported to a cryogenic storage facility intact. 
     Therefore, all means of capturing the flat sheet of tissue is accomplished by interrupted and circuitous surfaces that facilitate the flow and intimate contact of a transport liquid with the membrane top and bottom surfaces within a leak proof container device. 
     According to further aspects of the present disclosure, the methods and devices disclosed herein may enable removal of the mated top and bottom platen assembly from a transport containment, and permit easy separation of the larger tissue sample into multiple, individual, smaller sub-samples. To that end, each sub-sample may be secured in a manner that retains the flatness of the samples. In some embodiments, diskette assemblies may be provided for securing sub-samples, with each diskette assembly including a top diskette and a bottom diskette. Individual top diskettes may be mechanically coupled to the top platen, while individual bottom diskettes may be mechanically coupled to the bottom platen. In order to create multiple individual and smaller samples from a single large sample, the mated platen assembly may be removed from the transport container and placed on a flat surface. The multiple top diskettes, which protrude from the top platen, may be pushed downward and seated into the bottom platen and respective bottom diskettes. When all top diskettes are seated in their respective bottom diskettes, the top platen may be lifted and removed from the assembly. The array of multiple diskette assemblies may remain loosely attached in the exposed bottom platen. Each diskette assembly may encompass an associated portion of the tissue sample, while some or all to the diskette assemblies may continue to be adjoined by connecting membrane of the sample. A gap may be provided between adjacent diskette assemblies that permits a cutting tool, such as a scalpel, to be inserted to cut the connecting membrane. Alternatively, the diskette assemblies may be manually removed from the bottom platen in such a way to tear the connecting membrane and free each individual diskette assembly while the associated sub-sample contained within the separated diskette assembly remains secure and intact. 
     According to additional aspects of the present disclosure, each diskette may be placed into a vial for cryogenic storage. A cryogenic preservative solution can be added to the vial, while the diskette assemblies limit surface contact with the membrane, retain membrane flatness, and allow maximum solution intimacy with all surfaces for optimal preservation. 
     In some embodiments, one of the top and bottom diskettes may incorporate a sharp cutting element configured to cut through the sub-sample as the top diskette is mechanically seated on the bottom diskette. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Those of skill in the art will understand that the drawings portrayed and described are for illustration purposes only and not intended to limit the scope of the invention. 
         FIG. 1  is a perspective view of a device for securing a tissue sample constructed according to the present disclosure. 
         FIG. 2  is a perspective view of a bottom platen used in the device of  FIG. 1 . 
         FIG. 3  is a partial side elevation view, in cross-section, of the device of  FIG. 1  showing a diskette assembly in an actuated position. 
         FIG. 4  is a perspective view of a top platen used in the device of  FIG. 1 . 
         FIG. 5  is a perspective view of a bottom portion of the device for securing a tissue sample with biological material extending there over. 
         FIG. 6  is a perspective view showing a top platen positioned over the bottom platen with biological material disposed therebetween. 
         FIG. 7  is a perspective view of the device with the top platen secured to the bottom platen. 
         FIG. 8  is an exploded top perspective view of a diskette assembly. 
         FIG. 9  is an exploded bottom perspective view of the diskette assembly of  FIG. 8 . 
         FIG. 10  is a perspective view of a bottom platen with attached diskette lower housings. 
         FIG. 11  is a perspective view of a top platen with attached diskette upper housings. 
         FIG. 12  is a side elevation view, in cross-section, of the device of  FIG. 1  showing diskettes in the normal position. 
         FIG. 13  is a perspective view showing the device with the top platen removed and a scalpel cutting between adjacent diskettes, thereby to obtain sub-samples from the tissue sample. 
         FIG. 14  is a perspective view of the bottom platen with a diskette assembly removed for transport or storage. 
         FIG. 15  is a perspective view of a diskette assembly. 
         FIG. 16  is a side elevation view, in cross-section, of the diskette assembly of  FIG. 15 . 
         FIG. 17  is a side elevation view, in cross-section, of the diskette assembly of  FIG. 15 . 
         FIG. 18  is a perspective view of two devices for securing tissue samples in a nested stack configuration. 
         FIG. 19  is a perspective view of the two stacked devices of  FIG. 18  inserted into a transport vial. 
         FIG. 20  is an exploded perspective view showing an alternative transport vial for a single diskette assembly. 
     
    
    
     DETAILED DESCRIPTION 
     The methods and devices disclosed herein enable the successful retrieval of a large tissue sample from biological material in a sterile hospital environment. The tissue sample is captured with limited trauma and degradation to the material while encapsulating it for further transfer and ultimate preservation while in a living state. In particular, the methods and devices disclosed herein may be used to retrieve and preserve amnion tissue that is presented only during the birth of the species. A sample of living amnion tissue is deemed to comprise a highly beneficial population of stem cells, and can therefore be frozen in time to preserve cell viability for later utilization. The methods and devices disclosed herein may also facilitate cryogenic storage and return to maximum living cell viability. 
     Referring now to the drawings,  FIG. 1  illustrates an embodiment of a tissue securing device  20 . The issue securing device  20  may include a bottom platen  22  and a top platen  24 . The bottom and top platens  22 ,  24  may be provided as separate assemblies so that biological material may be positioned between the platens. Accordingly, when the top platen  24  is joined to the bottom platen  22 , a tissue sample  26  may be secured by the assembly, as described in greater detail below. 
     The bottom platen  22  is shown in  FIG. 2  as having a generally tray-like appearance formed by a bottom platen base  30  and a bottom platen side wall  32 . The bottom platen base  30  defines a bottom platen base inner surface  34 , while the bottom platen side wall  32  extends upwardly from a perimeter of the bottom platen base  30 . Together, the bottom platen side wall  32  and bottom platen base  30  define a bottom platen base receptacle  36 . As best shown in  FIG. 3 , a flange  38  coupled to a top end of the bottom platen side wall  32  may define a bottom platen engagement surface  40 . The bottom platen engagement surface  40  may extend around a perimeter of the bottom platen base receptacle  36 , thereby to provide a first surface for securing the outer edge of the tissue sample  26 . The bottom platen engagement surface  40  is spaced from the bottom platen base inner surface  34  to limit the amount of structure in direct contact with the tissue sample  26 . To provide a stable surface on which the biological material may be placed, the bottom platen engagement surface  40  may be substantially planar. 
     Turning to  FIG. 4 , the top platen  24  is illustrated as having a generally inverted, tray-like appearance formed by a top platen cover  42  and a top platen side wall  44 . The top platen cover  42  defines a top platen cover inner surface  46 , while the top platen side wall  44  extends downwardly from a perimeter of the top platen cover  42 . Together, the top platen side wall  44  and top platen cover  42  define a top platen cover receptacle  48 . As best shown in  FIG. 3 , a bottom portion of the top platen side wall  44  defines a top platen engagement surface  50 . The top platen engagement surface  50  extends around a perimeter of the top platen cover receptacle  48 , thereby to provide a second surface for securing the outer edge of the tissue sample  26 . The top platen engagement surface  50  is spaced from the top platen cover inner surface  46  to again limit direct contact with the tissue sample  26 . 
     The top platen engagement surface  50  is shaped to cooperatively interact with the bottom platen engagement surface  40 . As used herein, the term “cooperatively interact” means that the recited structures are configured so that they can be positioned in a tissue engaging position, thereby to secure the tissue sample  26  between the two engagement surfaces. Accordingly, in some embodiments, the top platen engagement surface  50  may have a shape that is a mirror image of that of the bottom platen engagement surface  40 , so that the engagement surfaces  40 ,  50  can be directly aligned. In these embodiments, the engagement surfaces  40 ,  50  may be configured to directly abut one another, or they may be configured to be spaced by a distance that is sufficiently small to firmly secure the tissue sample  26  therebetween. Alternatively, the engagement surfaces  40 ,  50  may be configured to have a closely telescoping fit, thereby to pinch an outer edge of the tissue sample  26  therebetween. The engagement surfaces  40 ,  50  may be configured to sever, shear, or otherwise separate an outer periphery of the biological material to obtain the final shape of the tissue sample  26 . Alternatively, the engagement surfaces may simply secure the tissue sample and a separate cutting step may be performed to remove the excess periphery of the biological material. 
     The bottom and top platens  22 ,  24  may be provided as separate components that can be assembled to secure the tissue sample  26 . To assist with assembly, the bottom and top platens  22 ,  24  may include alignment components so that the top platen engagement surface  50  is positioned properly with respect to the bottom platen engagement surface  40 . As shown in  FIG. 2 , the bottom platen  22  may include a first alignment structure, such as two pairs of brackets  52  extending outwardly from opposite ends of the bottom platen side wall  32 , while the top platen  24  may include a second alignment structure, such as two tabs  54  extending downwardly from opposite ends of the top platen side wall  44  that are sized for insertion between the two pairs of brackets  52 . The bracket pairs  52  and tabs  54  are located such that when the tabs  54  are inserted into the respective bracket pairs  52 , the top platen engagement surface  50  will be properly positioned relative to the bottom platen engagement surface  40 , thereby permitting cooperative interaction therebetween. 
     The tissue securing device  20  may further include a coupler assembly configured to releasably couple the bottom and top platens  22 ,  24 . As best shown with reference to  FIGS. 1 and 3 , the coupler assembly may include a latch  56  having a base rotatably coupled to the top platen  24  and a hook end  58 . Additionally, the bottom platen  22  may be formed with a coupler recess  60  configured to releasably engage the hook end  58  of the latch  56 . Accordingly, when the top platen  24  is assembled on top of the bottom platen  22 , the latch  56  may be rotated until the hook end  58  engages the coupler recess  60 , thereby to firmly secure the top platen  24  to the bottom platen  22 . As the coupler assembly is locked in place, the top platen  24  may be further pulled toward the bottom platen  22 , driving the top platen engagement surface  50  toward the bottom platen engagement surface  40  and further securing the periphery of the tissue sample  26 . 
     The tissue securing device  20  may be configured to promote exposure of the tissue sample  26  to controlled exterior environments, such as transport fluid or cryogenic media. As best shown in  FIGS. 2 and 3 , the bottom platen base  30  defines a plurality of bottom platen base apertures  62  that fluidly communicating between an exterior of the bottom platen  22  and the bottom platen base receptacle  36 . Additionally, as best shown in  FIGS. 3 and 4 , the top platen cover  42  defines a plurality of top platen cover apertures  64  fluidly communicating between an exterior of the top platen  24  and the top platen cover receptacle  48 . The bottom platen base apertures  62  and top platen cover apertures  64  promote fluid communication from an exterior of the securing device  20  and the tissue sample  26 , which can be beneficial when the device  20  is submerged in transport fluid or exposed to cryogenic media. 
     The bottom and top platens  22 ,  24  of the securing device  20  may be used on their own to obtain a relatively large tissue sample  26 . In operation, the top platen  24  is initially separated from the bottom platen  22 . Biological material may be placed over the bottom platen  22  so that an outer periphery of the biological material drapes over the sides of the bottom platen  22  ( FIG. 5 ). Using the alignment components, the top platen  24  may be assembled onto the bottom platen  22  until the top platen engagement surface  50  is properly positioned relative to the bottom platen engagement surface  40  ( FIG. 6 ). Next, the coupler assembly may be engaged to lock the top platen  24  onto the bottom platen  22  ( FIG. 7 ). During this process, the top platen engagement surface  50  is moved into a tissue engaging position relative to the bottom platen engagement surface  40 , so that a perimeter portion of what is to be the tissue sample  26  is firmly secured therebetween. The excess periphery of biological material is removed either automatically or in a separate cutting process, thereby to obtain the final shape of the tissue sample  26  ( FIG. 1 ). 
     While the bottom and top platens  22 ,  24  have separate utility, the securing device  20  may further include an array of diskette assemblies  70  for separating the tissue sample  26  into multiple, smaller sub-samples. Each diskette assembly  70  may include a diskette lower housing  72  and a diskette upper housing  74 , as best shown in  FIGS. 8 and 9 . 
     The diskette lower housing  72  may include a lower housing base  76  defining a lower housing base inner surface  78 . A lower housing side wall  80  extends upwardly from the lower housing base  76  so that the lower housing base  76  and the lower housing side wall  80  define a lower housing receptacle  82 . A lower housing shoulder  84  projects inwardly from the lower housing side wall  80  to define a lower housing engagement surface  86 . The lower housing engagement surface  86  extends around a perimeter of the lower housing receptacle  82  and is spaced a distance above the lower housing base inner surface  78 . 
     The diskette upper housing  74  may include an upper housing cover  88  defining an upper housing cover inner surface  90 . An upper housing side wall  92  extends downwardly from the upper housing cover  88  so that the upper housing side wall  92  and upper housing cover  88  define an upper housing receptacle  94 . The upper housing side wall  92  has a lower edge  96  defining an upper housing engagement surface  98 . The upper housing engagement surface  98  extends around a perimeter of the upper housing receptacle  94  and is spaced a distance below the upper housing cover inner surface  90 . The upper housing engagement surface  98  may be shaped to cooperatively interact with the lower housing engagement surface  86 , similar to the engagement surfaces  40 ,  50  described above. 
     The bottom platen  22  may be configured to secure the diskette lower housings  72  in defined locations to facilitate registration of each diskette lower housing  72  with an associated diskette upper housing  74 . As best shown in  FIG. 1 , the bottom platen base inner surface  34  defines an array of bottom platen base recesses  100 , each of which is sized to receive a diskette lower housing  72 . The bottom platen base recesses  100  may be formed by a series of intersecting platforms  102  that are elevated from the bottom platen base inner surface  34 , but not as high as the bottom platen engagement surface  40 . A base retainer  104  may extend upwardly from the bottom platen base inner surface  34  into each bottom platen base recess  100  and may be configured to releasably attach to a retainer aperture  106  formed in the diskette lower housing  72 , as best shown in  FIG. 10 . 
     Similarly, the top platen  24  may be configured to secure the diskette upper housings  74  in defined locations to facilitate registration with an associated diskette lower housing  72 . As best shown in  FIG. 4 , the top platen cover defines an array of cover apertures  64 . Each upper housing cover  88  is sized for insertion through the cover apertures  64 . An upper housing shoulder  108  ( FIG. 8 ) extends outwardly from the upper housing cover  88  and defines a shoulder surface  110  configured to engage the top platen cover inner surface  46 , thereby to prevent further insertion of the diskette upper housing  74  through the cover aperture  64 . A flexible cover tab  109  may project outwardly from the upper housing cover  88  that may deflect to pass through the cover aperture  64 . Once the cover tab  109  is clear of the cover aperture  64 , it may resume its original shape, thereby by to secure the diskette upper housing  74  in a normal position. Subsequently, when sufficient downward force is applied to the upper housing cover  88 , the cover tab  109  may again deflect to permit the diskette upper housing  74  to move downwardly to an actuated position, as discussed in greater detail below. 
     Each cover aperture  64  is positioned to register with an associated bottom platen base recess  100 , so that each associated cover aperture  64  and bottom platen base recess  100  define a diskette receptacle configured to ultimately receive and enclose a diskette assembly  70 . For example, bottom platen base recesses  100  and cover apertures  64  may be located relative to the alignment components of the bottom and top platens  22 ,  24 , respectively, such that when the alignment components are engaged to assemble the bottom and top platens  22 ,  24 , the lower and upper housing engagement surfaces  86 ,  98  are simultaneously aligned. 
     Each diskette assembly  70  may be configured so that the diskette lower housing  72  automatically engages the diskette upper housing  74  during operation, such as when the diskette upper housing  74  is dislodged from the top platen  24  and moved to the actuated position. For example, as best shown in  FIG. 12 , the diskette lower housing  72  may include a lower housing retainer in the form of a lower housing flange  111  flange extending inwardly from the lower housing side wall  80  and defining a lower housing flange surface  112 . The diskette upper housing  74  may include an upper housing retainer in the form of a flexible tab  114  protruding outwardly from the upper housing side wall  92  and defining an upper tab surface  116 . As the diskette upper housing  74  is driven toward the diskette lower housing  72 , the tab  114  may deflect until it passes the lower housing flange  111 , at which time the tab  114  may resume its original shape. In this position, the upper tab surface  116  will engage the lower housing flange surface  112  to resist separation of the diskette upper housing  74  from the diskette lower housing  72 . 
     Movement of the diskette upper housing  74  from the normal position to the actuated position may facilitate separating one or more sub-samples  120  from the tissue sample  26 . In the normal position, where the diskette upper housing  74  engages the top platen  22 , the upper housing engagement surface  98  is positioned above the top platen engagement surface  50  and is aligned with but spaced from the lower housing engagement surface  86 , as shown in  FIG. 12 . In the actuated position, the diskette upper housing  74  is disengaged from the top platen  22  and moved downwardly so that the upper housing engagement surface  98  is positioned below the top platen engagement surface  50 , as best shown in  FIG. 3 . When in the actuated position, the upper housing engagement surface  98  may be in a tissue engaging position such that a periphery of the sub-sample  120  is pinched between the lower and upper housing engagement surfaces  86 ,  98  ( FIG. 3 ). The engagement surfaces  86 ,  98  may abut or may be spaced by a distance sufficiently small so that the sub-sample  120  is secured therebetween. In some embodiments, the lower and upper housing side walls  80 ,  92  may be configured to shear, cut, or otherwise sever through the tissue sample  26 . 
     Each diskette assembly  70  may be configured to promote fluid communication from the exterior environment to an interior space surrounding the tissue sub-sample  120 . As best shown in  FIGS. 8-12 , each upper housing cover  88  defines a plurality of upper housing cover passages  130  fluidly communicating between an exterior of the upper housing cover  88  and the upper housing receptacle  94 . Additionally, each lower housing base  76  defines a plurality of lower housing base apertures  132  fluidly communicating between an exterior of the lower housing base  76  and the lower housing receptacle  82 . A bottom surface  134  of the diskette lower housing  72  may further be formed with channels  136  extending between each of the lower housing base apertures  132 , thereby to further promote fluid flow into the lower housing receptacle  82 . Additionally, the upper housing engagement surface  98  may be configured to promote additional fluid flow to the sub-sample  120 . More specifically, the upper housing engagement surface  98  may be formed with a series of upper housing engagement surface passages  138  ( FIG. 12 ) that fluidly communicate between an exterior of the diskette upper housing  74  and the upper housing receptacle  94 . 
     In some embodiments, the device  20  may be configured to facilitate a separate cutting step to separate the sub-sample  120 . In these embodiments, the sub-sample  120  is not separated simultaneously as the diskette upper housing  74  is moved to the actuated position. Instead, movement of the diskette upper housing  74  only secures a periphery of the sub-sample  120  between the lower and upper housing engagement surfaces  86 ,  98 . A separate cutting step may be facilitated by sufficiently spacing the bottom platen base recesses  100  so that a cutting gap  142  is provided between lower housing side wall peripheries  140  of adjacent diskette lower housings  74  ( FIG. 3 ). The platforms  102  may extend between the adjacent bottom platen base recesses  100 , and therefore an upper platform surface  144  may be aligned with the cutting gap  142  to provide stop for the cutting blade, as shown in  FIG. 13 . An individual diskette assembly  70  holding a sub-sample  120  may then be separated from the bottom platen  22 , as shown in  FIG. 14 . 
     A diskette assembly  70  having engaged diskette lower and upper housings  72 ,  74  is illustrated in  FIGS. 15-17 . From these drawings it will be appreciated that a periphery of the sub-sample  120  is secured within the housings  72 ,  74  with minimal direct contact. Additionally, it is seen how the upper housing cover passages  130 , lower housing base apertures  132 , channels  136 , and upper housing engagement surface passages  138  promote fluid communication between an exterior of the diskette assembly  70  and the sub-sample  120 . 
       FIG. 18  illustrates two devices  20  stacked in a nested configuration. The stacked devices  20  may be inserted into a transport vessel  150  as shown in  FIG. 19 . The transport vessel  150  may be filled with a preservative solution, which may intimately contact the tissue samples  26  through the various apertures and passages in the platens  22 ,  24  and diskette housings  72 ,  74  noted above. When the devices  20  arrive at the intended destination, such as a cryogenic storage facility, the entire device  20  holding the full tissue sample  26  may be stored, or individual sub-samples  120  housed in diskette assemblies  70  may be separated and stored as needed. If the entire device  20  is cryogenically stored and only a sub-sample  120  is later needed, the device  20  may be thawed and the sub-sample  120  separated without direct handling of the tissue sample  26 . Similarly, the device  20  permits an explant culture procedure for stem cell derivation to be performed, and is capable of being immersed in a cryogenic preservation medium and returned to cryogenic storage more than one time without directly handling the tissue sample. 
       FIG. 20  illustrates a diskette assembly  70  disposed in an individual cryogenic vial  160 . The cryogenic vial  160  may be filled with a preservative solution and prepared for cryogenic storage, thereby allowing individual sub-samples  120  to be separated and stored with minimal handling of the tissue. 
     INDUSTRIAL APPLICABILITY 
     The device as described allows a placental tissue sample to be secured, transported in an appropriate protection medium, transferred to an appropriate cryogenic preservation medium and frozen intact. The device further allows, at a future time, a thawing procedure followed by an explant stem cell derivation culture procedure, which upon conclusion allows the return to cryogenic preservation for a second or more times. 
     The device may be used to capture a tissue sample at a child birthing event; permit immersion in a medium for transportation preservation to the next laboratory site; permit transfer from a transportation medium to a cryo-preservation medium; permit cryogenic storage; permit removal and thawing from cryogenic storage; and permit subsequent explant culturing to derive Mesenchymal-like stem cells, all with minimal or no direct handling of the sample. Furthermore, the device allows the sample to sustain repetitive cycles of cryogenic freezing, thawing, and explant stem cell derivation. 
     Additionally, portions of the device may be constructed of a biomimetic material that can serve as a tissue scaffold that can be directly utilized after a placental tissue derived Mesenchymal-type stem cell derivation procedure. 
     In view of the foregoing, the subject matter disclosed herein may facilitate one or more of the following advantages: 
     (1) Providing a staging platform or work surface upon which to present and stabilize a large and unwieldy tissue sample for further manipulation and preparation. This is accomplished by a rigid bottom platen assembly. Optional detachable legs are offered as a means of additional elevation of the working surface as needed; 
     (2) After staging, the sample may be secured in a manner that retains flatness and prevents folding, curling, shrinkage or other movement, as the sample will normally tend to migrate in many directions. This is accomplished by mating a rigid top platen assembly over the bottom platen assembly, and having the ability to clamp the two platen halves together, thus capturing the large tissue sample between the halves. 
     (3) Because a singular large sample may be most conducive to transportation for further professional preservation, the platen assemblies may be configured to permit nested stacking in a compact manner that facilitates insertion into a transport container. Also, because exposure to air should be limited, the large tissue sample may be quickly placed within a preserving liquid solution, and the components comprising the platen assembly may facilitate maximum intimate liquid contact with top and bottom tissue surfaces when the platens are immersed in the solution. Discrete passages may be formed in the surfaces contacting and retaining the tissue sample to promote fluid contact with the tissue sample. In some embodiments, the platen materials in contact with the tissue sample may be formed of a hydrophilic material to maximize surface wetting. 
     (4) The ability to separate the large tissue sample into multiple sub-samples may provide additional advantages. When tissue samples are cryogenically preserved, a common practice is to thaw the entire tissue sample, extract the desired sub-sample, and then re-freeze the remainder of the tissue sample. Each thaw and freeze cycle is believed to diminish the viability of the sample. Accordingly, it may be advantageous to provide the ability to freeze and thaw smaller pieces of the large sample on a more selective basis, as permitted by the use of the diskette assemblies taught herein. 
     (5) Similar to transport conditions, when the large tissue sample is transformed into smaller multiple sub-samples for cryogenic storage, the sub-samples are typically immersed in a cryogenic preservation medium. The methods and apparatus disclosed herein promote intimate contact between the surfaces of the tissue sample and the preservation medium. 
     It will be appreciated that the foregoing description provides examples of the disclosed assembly and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.