Enriched platelet wound healant

Details Enriched platelet wound healant Enriched platelet wound healant

1999-11-23

2001-10-16

Fay, Zohreh (Department: 1614)

Drug, bio-affecting and body treating compositions

Topical body preparation containing solid synthetic organic...

Skin burn or open wound treatment

C424S450000, C424S093720, C514S724000, C514S725000, C514S946000, C514S947000

Reexamination Certificate

active

06303112

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention disclosed herein generally relates to a composition of matter used in the treatment of wounds, a method of making same, and a method of using same.
There have been many different substances and methods developed in the past for treating wounds, depending upon the type and location and severity of the wound. A wound is generally defined as an injury to an area of the body of a human or animal. Although injury to the surface of the skin is the most well known type of wound, the surfaces of internal organs may also be wounded, such as during surgery, rupture of the spleen or liver, or resulting from traumatic blows to the body surface in the vicinity of an internal organ.
Medical practice characterizes wounds as chronic or acute, according to the persistency and severity of the wound. A chronic wound is one that is prolonged or lingering, rather than promptly healed. An acute wound is one that occurs relatively quickly, and heals relatively quickly as well. Tissue wounds may have a wide spectrum of manifestations, as small as merely an abnormal microscopic tear or fissure in tissue (or a surface thereof), or as large as the abrasion or ablation of the skin covering a substantial portion of the body, such as in a burn victim. Acute wounds covering a large or movable surface are usually the most difficult to guard from infection, and to heal.
The invention described herein is primarily related to substances topically applied to the exterior surface of chronic wounds, although the invention described herein also has some applications for facilitating the healing of other wounds such as acute wounds. The composition of matter described herein is especially suited to topical application to burn wounds and chronic lesions, such as ulcers on the feet of diabetics. However, the compositions of matter and the methods described herein are not limited solely to that topical application.
Wound healing is affected by the presence of various substances found in the blood and bodily fluids. The blood is the primary medium for delivering healing agents to the wound site, and for transporting foreign or harmful substances away from the wound. Whole blood is primarily comprised of three main types of cells suspended in a protein rich solution known as plasma.
The three main cell types of whole blood are erythrocytes (a.k.a. red blood cells), leukocytes (a.k.a. white blood cells) and thrombocytes (a.k.a. platelets). The red blood cells are the iron-containing cells that facilitate the transport and transfer of oxygen to body tissue, and the removal of carbon dioxide. The white blood cells perform functions such as phagocytosis of foreign bodies and production of antibodies, primarily responsible for fighting infection and foreign substances within the blood or wound site. Platelets perform many functions such as plugging leaks in blood vessels and helping begin the process leading to the formation of a blood clot; platelets contain substances known as growth factors that facilitate the formation of new tissue.
Although there are several methods for separating whole blood into its various components, one of the most convenient and expeditious methods is accomplished by differentially centrifuging blood or some of its components (i.e., apheresis). In this way, the red and white blood cells and plasma may be separated out and returned to the donor's or patient's body, leaving the sequestered platelets in essentially concentrated form for use in wound healing techniques. From blood extracted from a patient, the platelets may thus be obtained and activated for use on the same patient; methods of using a patient's own blood are called “autologous” or “autogenic” donor methods. Methods using blood donated by one or more third parties for use by a patient are called “homologous” or “heterologous” donor methods, or collectively called “allogenic” methods.
One of the proteins suspended in plasma is fibrinogen, which reacts with substances released into (or attracted by) wound sites to produce sticky strands offibrin. Such reactions result in the cross linking of the strands to form a mesh that holds and supports the deposit or growth of other tissue materials at the wound site.
The wound healing process is generally considered to occur in several stages, generally know as the healing cascade. After tissue injury, platelets are among the first cells to appear in the vicinity of the wound. Activation of a platelet by an agonist such as thrombin, or other agonists such as those listed elsewhere herein, leads to the release of granule material from within the platelet. Such granulation activation results in the release of proteins known as growth factors, primarily concentrated in the alpha granules of platelets. These released growth factors stimulate the formation of new tissue; when applied to wounds, growth factors have been known to increase the rate of collagen laydown, vascular ingrowth, fibroblast proliferation and overall healing. The release of a protein known as platelet-derived growth factor (PDGF) is a chemotactic for monocytes, neutrophils and fibroblasts into the wound, to begin the inflammatory stage of the healing process. During this time, monocytes secrete PDGF and another platelet protein known as transforming growth factor-&bgr;1, which recruits and activates fibroblagts, a prerursor to fibrinogen, to begin the repair stage of the healing process. Subsequently, wound healing continues through the process of collagen remodeling within the wound.
The presence of growth factors promotes wound healing. The invention described herein increases the amount of growth factors in the wound, and thereby facilitates the promotion of the healing rate. This may be especially important in “wounded” patients, especially those with chronic wounds who may lack sufficient circulation to facilitate the healing cascade. The invention described herein also facilitates the covering of the wound area with a substance that prevents or helps to reduce infection caused by most bacteria; and to the extent that the wound treatment material is made from autologous blood or similar biological materials, the invention described herein reduces the risks associated with the use of treatment materials made from biological materials obtained from one or more third parties. An autologous product avoids some of the common problems associated with the use of biological materials from third parties, such as (for example) screening to assure that the donor was biologically or immunologicaly compatible with the patient, and otherwise free of hepatitis, HIV and the like.
Base upon the foregoing general scientific principles, already known in the field are wound sealants made from biological materials obtained primarily from tissue other than blood platelets. For example, wound sealants include “fibrin glue,” which often is essentially a mixture of co-coagulants (thrombin and calcium), concentrated fibrinogen and other coagulation proteins. In most applications, the primary roles of fibrin glue are to seal wound surfaces to prevent loss of blood and other body fluids after surgery, and to provide adhesion between adjacent tissue surfaces. These products form a hard, cast-like covering over the area to be sealed, and tend to be non-yielding to limb movement.
The production of fibrin glue often requires obtaining fibrinogen from blood through a process known as cryoprecipitation, including both freeze-thaw cycles and relatively lengthy centrifuigation of plasma in controlled environments, to concentrate the fibrinogen in large enough amounts required for use; the precipitant thus obtained is frozen to −20° to −30° centigrade before storage. These requirements make such materials unsuitable for application during the course of surgery, especially emergency surgery without an hour or more lead time; moreover, to the extent this process depends upon the use of autologous biological materials, using this process shortly before or during surgery may result in the loss of c

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