CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of provisional U.S. Patent Appln. No. 60/446,534, filed Feb. 12, 2003; it is also related to the patent application (atty. dkt. 4278-4) entitled “Random and Non-Random Alkylene Oxide Polymer Alloy Compositions” and being filed on Feb. 12, 2004. Both applications are incorporated by reference.
The invention relates to medical and surgical uses of a random alkylene oxide copolymer.
In the medical and surgical fields, there has been an unmet need for compounds with handling characteristics that range from a viscous oil to a hard wax. Desirable compounds would have one or more of the following properties: biocompatibility, stability during storage and under physiological conditions, low toxicity and corrosiveness, readily eliminated from the body in unmodified form, easy and inexpensive to manufacture and store, and variable viscosity and hardness. Such compounds would have a wide range of uses. Compounds with oily, greasy, or waxy characteristics (in ascending degrees of hardness) can be used as lubricants of surgical instruments and implants. Applications would include use as a carrier or excipient for particulate implantable materials, bioactive agents, and other pharmaceutical agents. Random AOC compounds are also suitable as a matrix for particulate material, adhesive/cohesive, filler, and/or lubricant; they may also be used as dispersing or suspending agents, emulsifiers, extenders, thickeners, and/or bodying agents for compositions and other pharmaceutical formulations.
Currently, the medical and surgical need for the appropriate formulations is being met in a number of different and less than acceptable ways. Most have the problem of either not being completely biocompatible or not having handling characteristics that are well suited for their intended application. Compounds derived from biological sources, such as collagen, have the potential to cause immune reactions and may even have the potential to spread infectious agents. Many compounds in use fall into the category of hydrogels. Hydrogels in general lack the appropriate handling characteristics in that they lack plasticity, and are often unstable when compressive forces are applied to them. The water within hydrogels also may affect the long-term stability of pharmaceutical and biological agents. Petroleum-based hydrocarbon compounds have the appropriate handling characteristics, but are not water soluble. Silicon oils and silicon gels are neither biologically inert nor water soluble. Thus, suitable polymers for therapeutic use remain to be discovered.
In the fields of surgery and dentistry, there is a need for an implantable material that contains a particulate component that can serve as a framework for tissue ingrowth. The particulate component can be selected from a broad range of natural and synthetic implantable substances, including but not limited to native autogenous bone or cartilage, bone or cartilage from other sources that is either grafted directly or after processing, collagen, hydroxyapatite, poly-methylmethacrylate (PMMA), polytetrofluoroethylene (PTFE), polyethylene, and dimethylpolysiloxane.
The performance of particulate implants is markedly improved by the addition of a matrix to temporarily adhere the particles to one another and to form a putty that serves to improve the handling characteristics and acts as a delivery system. The majority of matrices in use or disclosed in the prior art are hydrogels, and they include collagen, glycerol, polysaccharides, mucopoly-saccharides, hyaluronic acid, plasdones, and polyvinylpyrrolidones (PVP).
Collagen, in the form of gelatin, has been used in ARTEPLAST® from Rofil Medical International. It is an injectable material comprised of micro-spheres of polymethylmethacrylate (PMMA) suspended in a gelatin solution. Following implantation, the gelatin is resorbed and replaced by native collagen. Another formulation, ARTECOLL® is a product currently available in Europe and Canada. It is comprised of smooth PMMA spheres, suspended in bovine collagen from a closed pharmaceutical herd at a concentration of 25% PMMA/75% collagen, by weight with 0.3% lidocaine. Because ARTECOLL® contains bovine collagen, testing for allergy to such collagen is recommended. Bovine collagen carries the risk of an immunogenic reaction by the recipient patient. Recently, it has been found that a disease of cattle, bovine spongiform encephalopathy (BSE) is transmitted from bovine tissue to humans. Thus, bovine collagen carries a risk of disease transmission and is not a desirable matrix for allograft bone. Human collagen is free of these animal-based diseases. However, collagen absorbs slowly in the human body, particularly in a bony site with a low degree of vascularity.
Glycerol is used as a matrix for demineralized allograft bone in the form of a gel. For example, GRAFTON® from Osteotech is a simple mixture of glycerol and lyophilized, demineralized bone powder (U.S. Pat. No. 5,073,373). GRAFTON® works well to allow the surgeon to place the allograft bone at the site. But glycerol has a very low molecular weight (92 daltons) and is very soluble in water, the primary component of the blood which flows at the surgical site. Glycerol also experiences a marked reduction in viscosity when its temperature rises from room temperature (typically 22° C. in an operating room) to the patient's body temperature (typically 37° C.). This combination of high water solubility and reduced viscosity causes the allograft bone with a glycerol matrix to be runny and to flow away from the site almost immediately after placement. This prevents the proper retention of the allograft bone within the site as carefully placed by the surgeon. The use of the low-molecular weight glycerol carrier also requires a high concentration of glycerol to be used to achieve the bulk viscosity. Glycerol and other low-molecular weight organic solvents are also toxic and irritating to the surrounding tissues. U.S. Pat. No. 6,306,418 describes the use of glycerol as the matrix for TEFLON® particles in the field of urology.
Surgical implantation of artificial sphincters has often been employed to treat patients suffering from urinary incontinence. The most common and widely used method to treat patients with urinary incontinence is periurethral injection of a composition commercially sold as POLYTEF™, which is a paste comprising a 1:1 by weight mixture of glycerin matrix and TEFLON® particles. After injection, however, the glycerin is readily dissipated into the body over a period of time and then metabolized or eliminated, leaving only the TEFLON® particles. A drawback of such a paste is that the size of the particles is sufficiently small so as to allow them to migrate to other locations of the body such as the lungs, brain, etc. TEFLON® particles have been known to induce tissue reaction and form TEFLON®-induced granulomas in certain individuals. This tissue reaction to TEFLON® also has caused concerns for the patient's health.
U.S. Pat. No. 4,191,747 discloses a bone defect treatment with denatured bone meal freed from fat and ground into powder. The bone meal is mixed with a polysaccharide in a solution of saline and applied to the bone defect site.
U.S. Pat. No. 5,290,558 discloses a flowable, demineralized bone powder composition using an osteogenic bone powder mixed with a low molecular weight polyhydroxy compound possessing from 2 carbons to about 18 carbons including a number of classes of different sugars such as monosaccharides, disaccharides, water-dispersible oligosaccharides, and polysaccharides.
U.S. Pat. No. 5,356,629 discloses making a rigid gel in the form of a bone cement to fill defects in bone by mixing biocompatible particles preferably PMMA coated with polyhydroxyethylmethacrylate in a matrix (e.g., hyaluronic acid) to obtain a molded semisolid mass which can be suitably worked for implantation into bone. The hyaluronic acid can also be utilized in monomeric form or in polymeric form preferably having a molecular weight not greater than about one million daltons. It is noted that non-bioabsorbable but biocompatible particles can be derived from xenograft bone, homologous bone, autogenous bone, as well as other substances. The bioactive substance can also be an osteogenic agent such as demineralized bone powder, in addition to morselized cancellous bone, aspirated bone marrow, and other autogenous bone sources. This is a cement used for implantation of hip prosthesis.
Ersek et al. describe the clinical use of soft particles delivered as a biphasic hydrogel material (Plast. Reconstr. Surg. 95:985-992, 1995). The material comprises solid particles of dimethylpolysiloxane ranging in size from 100 micron to 600 micron suspended in a gel (CHCH2)2N(CH2)3—CO of the plasdone family.
BIOPLASTIQUE® material from Uroplasty, a biphasic material, consists of solid silicone particles, ranging from 100 microns to 400 microns in size, suspended in a polyvinylpyrrolidone (C6H9NO)n(PVP). But this material elicits a low-grade inflammatory response upon injection. In a rabbit model, the hydro-gel matrix is reabsorbed by the body within 96 hours and eliminated in an intact form by the kidneys. The hydrogel matrix is replaced by fibrin and inflammatory cells. Fibroblasts are recruited into the area by 14 days and begin to replace the fibrin bed with a collagen matrix. The collagen encapsulates and localizes the silicone, and animal studies have not shown any evidence of foreign body migration. Deposition of collagen progresses, replacing the organic component of the material in a ratio slightly greater than 1:1. Connective tissue cells develop and replace about 30% of the matrix with host collagen fibrils. At 382 days, fibrosis was complete and each individual particle appeared to be encased in its own fibrous capsule. This material has the distinct disadvantage of using silicone, which may be of concern when evaluating long-term safety.
U.S. Pat. No. 5,641,502 discloses a material comprising (i) a polymer derived from hydroxyacids, tactones, carbonates, etheresters, anhydrides, orthoesters, and copolymers, terpolymers and/or blends thereof and blended with (ii) at least one surface active agent which is from 2% to 55% by weight block copolymer of polyoxyethylene and polyoxypropylene. Additionally, a leaching agent from 1% to 70% by weight may be included in the blend to provide a porous microstructure.
U.S. Pat. No. 6,281,195 discloses a poloxamer hydrogel matrix for the delivery of osteogenic proteins. In particular, poloxamer 407 (PLURONIC® F127) is used in the form of a hydrogel. But hydrogels have disadvantages if used as the matrix instead of the present composition.
Therefore, it is an objective of the invention to provide a compound with superior properties for medical and surgical applications. Handling properties, biocompatibility, lubricity, non-toxicity, and tackiness are characteristics which are of particular interest. Further advantages of the invention are described.
The invention relates to a random alkylene oxide copolymer (random AOC) that can be advantageously used in medicine, surgery, and various other therapeutic applications. This compound is a random copolymer comprised of ethylene oxide and one or more other alkylene oxide(s), wherein the random copolymer has (i) molecular mass from 1 kg/mol to 1000 kg/mol (the average mass of the distribution of copolymers) and (ii) mass ratio of the ethylene oxide to the other alkylene oxide is from 5:95 to 95:5. Compositions may contain at least random AOC, and optionally one or more therapeutic products.
The random AOC can be biocompatible and substantially non-toxic to living tissue. Under physiological conditions, it can be substantially stable such that it is not metabolized and is readily eliminated from the body in unmodified form. The random AOC can be water soluble, but it may also be formulated to contain no water (i.e., substantially anhydrous except for minor amounts of absorbed water). Water may be added prior to use or absorbed in the body. But it is preferred to formulate the compound as a flowable liquid (with less than 5% or 1% water) before use in the body or further formulation. Generally, it is not considered a hydrogel, especially before use in the body or further formulation.
Choice of the other alkylene oxide(s), molecular mass, mass ratio, and procedures during manufacture can affect the compound's properties: e.g., hardness, adhesiveness, cohesiveness, ductility, malleability, and hardness. For example, “working” the compound or composition may stabilize these properties by homogenizing its internal structure. Handling characteristics may be similar when compared between ambient temperature (e.g., 20° C. to 25° C.) and body temperature (e.g., 37° C. or 40° C.).
Such products may be administered to the body (e.g., applied topically to the skin or other exposed tissue, depot or suppository, implanted or placed therein, ingested, injected). Biocompatibility and non-toxicity are desirable properties for such applications.
A matrix product is provided in some embodiments which is comprised of: (i) solid or porous particles suspended in (ii) a random AOC compound or a composition thereof. This matrix material may be adhered to hard tissues (e.g., tooth, bone, cartilage) and other body tissues with minimal adverse reaction by the tissue (i.e., biocompatible). The matrix may be eliminated with time to leave behind a framework of the particles, and tissue may grow within the framework. Other polymers may also be formulated with the random AOC.
Further objectives are to provide compounds, compositions, and other products for use in medical and surgical applications. They may be inserted into a body cavity or tissue, placed adjacent to mucosa as a suppository, or administered orally, parenterally, or topically. They can be used as carriers or excipients for bioactive agents, adhesives/cohesives, detergents, lubricants, and particulate matrices. In addition to hemostasis and tissue augmentation, a bioactive agent may be delivered or a bioimplant may be manufactured.
In another embodiment, a random AOC may be used as an excipient for other surgical and medical applications. The excipient may take advantage of any one of the beneficial properties described herein to deliver a therapeutic (e.g., bioactive agent or device) in the body of a human or animal. For example, the excipient may act as a lubricant to assist the passage or placement of the therapeutic in the body or a part thereof. Such pharmaceutical compositions may also include a vehicle (e.g., water, physiological saline, buffered solution). Processes for using and making the excipient and composition are also provided.
Further aspects of the invention will be apparent to a person skilled in the art from the following detailed description and claims, and generalizations thereto.
Compounds and compositions of the present invention may be utilized for a wide variety of medical and surgical applications. The discovery that a family of random AOC compounds can be used in therapy was surprising and unexpected. Such uses are described in more detail below.
Random AOC may be applied as a carrier to a device (e.g., polyethylene implant or metal instrument) to improve its handling and to alter the surface characteristics of the device. Another embodiment is a random AOC matrix and a porous or solid filler for use in surgery. The matrix can also act as a flowable, anhydrous, biocompatible, non-toxic, and/or adhesive system with characteristics desirable for safe and effective delivery of bioactive agents (e.g., malleable at room temperature and readily eliminated from the body). In growth of tissue may be promoted with a porous network left behind by resorbed matrix. Cosmetic and reconstructive surgery may use random AOC for augmentation, adhering body parts and/or surgical device/instrument, temporarily attaching tissue until permanent adhesives are activated, and/or for lubrication.
Poly(alkylene oxide)s (PAO) which are also known as polyoxyalkylenes (POA) are made by the polymerization of alkylene oxides (e.g., ethylene oxide, propylene oxide, butylene oxide). A homopolymer is formed only from one type of alkylene oxide while a copolymer is formed from two or more different alkylene oxides, known as alkylene oxide copolymers (AOC). Examples of the former are poly(ethylene oxide) (PEO), which is a polymer of ethylene oxide (EO), and poly(propylene oxide) (PPO), which is a polymer of propylene oxide (PO). Poly(ethylene oxide) is also commonly known as polyethylene glycol (PEG) or polyoxyethylene (POE). Molecular weight of such polymers is generally characterized as the average of a distribution of lengths (or repeat units). PEO is amphiphilic, extremely hydrophilic, water soluble, biocompatible, and non-toxic and is produced commercially in a wide range of molecular weights (200 g/mol to 10 million g/mol). Low-molecular weight forms of PEO below 600 g/mol (i.e., oligomeric forms with less than 14 EO monomer units on average) are low-viscosity liquids at room temperature; PEO is a solid at 25° C. above 600 g/mol. PPO differs from PEO in that it is hydrophobic, generally insoluble in water except at low molecular weights (less than about 1 kg/mol), and is liquid at 25° C. even at high molecular weights (e.g., 6 kg/mol).
In addition to the standard linear forms, branched or star forms of poly(alkylene oxide)s are produced by initiating the polymerization reaction with a polyfunctional initiator with multiple hydroxyl-, amino-, or thiol-groups each of which can serve as a starting point for polymer chain growth. For example, the use of glycerol (three hydroxyl groups) as an initiator results in a three-armed branched polymer, while pentaerythritol results in a four-armed polymer. PEO molecules of this type are available commercially (e.g., the Sunbrightm series, NOF Corporation, Japan) with anywhere from three to more than one hundred arms. Conventionally, polymers of this type with 3 to 10 arms are termed “branched” while those with more than 10 arms are termed “star” polymers. “Comb” copolymers are similar to branched and star forms, but the initiator for comb copolymers is a polyfunctional polymer with multiple hydroxyl-, amino-, or thiol-groups spaced along the initiator backbone, each of which can serve as a staring point for polymer chain growth. “Graft” copolymers are made by the addition of pendant polymer chains along a polymer backbone that possesses unsaturated C═C bonds or pendant functional groups (e.g., hydroxyl) from which pendant chains can be added by using a reactive monofunctional polymer chain.
All poly(alkylene oxide)s contain, in addition to multiple alkylene oxide-derived repeat units, a single residue corresponding to the molecule used to initiate the polymer synthesis. For linear polymers, this may be an alkylene glycol corresponding to the alkylene oxide used for the synthesis (e.g., ethylene glycol and ethylene oxide, respectively) and thus the initiator-derived residue will be indistinguishable from the other repeat units in the polymer chain. But small molecules other than alkylene glycols are often used as initiators, examples include methanol or N-butanol (for linear polymers) and trimethylol propane, glycerol, or pentaerythritol (for branched polymers). The mass of initiator relative to the mass of the final polymer chain is generally very small and can usually be neglected. Thus, the term poly(alkylene oxide) is used here in its customary sense, and includes both poly(alkylene oxide)s initiated with an alkylene glycol molecule and poly(alkylene oxide)s initiated with another small molecule.
Random AOC preferably has a molecular mass from about 1 kg/mol to about 1000 kg/mol (i.e., average molecular mass of a distribution of polymers). It may have a molecular mass of at least about 5 kg/mol, about 10 kg/mol, or about 20 kg/mol; the molecular mass may also be not more than about 25 kg/mol, about 50 kg/mol, or about 200 kg/mol. The mass ratio of ethylene oxide to the other alkylene oxide(s) preferably is from about 5:95 to about 95:5. It may have a mass ratio of at least about 10:90, about 25:75, or about 40:60; the mass ratio may also be not more than about 60:40, about 75:25, or about 90:10. The compounds may be described by intermediate ranges using the aforementioned upper and lower limits.
In a particular embodiment, the molecular mass may be from about 15 kg/mol to about 30 kg/mol. Preferably, the molecular mass is at least about 20 kg/mol and/or not more than about 25 kg/mol and the mass ratio of ethylene oxide to propylene oxide is substantially equimolar. Random EO/PO copolymers have a certain combination of properties which distinguish them from EO and PO homopolymers and EO/PO block copolymers, and which make them uniquely useful as excipients for certain pharmaceutical applications. The most important of these is that they combine two of the desirable properties of PEO and PPO - i.e., they are liquids at room temperature and above over a wide range of molecular weights, but are water soluble. In contrast, except at low molecular weights (less than 1 kg/mol), PPO is not water soluble and PEO is a solid. Also, unlike most block copolymers, random EO/PO copolymers do not self-associate to form structured domains or a crystalline structure (hence their liquid nature), and they are therefore useful as solvents or softeners for a wide range of other polymers and copolymers.
Like all other PAOs, they are soluble in selected organic solvents, able to solubilize many organic and inorganic substances including hydrophobic drugs that are insoluble or poorly soluble in water, and are substantially non-toxic.
Water-soluble PAO have low toxicity when applied to the skin or taken orally. There is some evidence that small PEG molecules (600 g/mol or less) may be metabolized in vivo to produce oxalate, which is toxic. But larger PAO are known to be effectively inert and non-metabolizable in vivo, and are excreted in substantially unmodified form. This provides a further advantage of the higher molecular weight random PAO liquids vs. liquid PEG.
Random EO/PO copolymers are non-aqueous flowable liquids and inert, but water soluble. They can be used in anhydrous formulations which are useful for when water is undesirable. Random EO/PO copolymers are miscible with other poly(alkylene oxide)s and more desirable in this regard than a liquid poloxamer. In summary, random EO/PO copolymers offer unique, novel, and unanticipated benefits when used as pharmaceutical excipients, especially in formulations for parenteral use. When appropriately selected for molecular weight, geometry, and EO:PO ratio, such random copolymers are versatile and advantageous alternatives to low molecular weight liquid PEO and PPO and some poloxamers as an excipient for drug formulations; can replace emulsifiers for preparation of formulations of some hydrophobic drugs; can solubilize certain hydrophobic drugs in the complete absence of water; are a unique excipient for plasticizing, softening, or solubilizing other materials in the absence of water or other small molecule solvents (e.g., when the presence of water or solvent is undesirable); and when used in combination as a blend, will further modify and extend the properties of polymers, making them more useful as excipients in general, and in particular as carriers for delivery of bioactive agents or as implantable carriers for particulate materials.
This combination of properties distinguishes random EO/PO copolymers from most other polymeric liquids including EO or PO homopolymers and block copolymers as follows:
1. Low molecular weight liquids (e.g., glycerol, PEG of 600 gimol or less) generally dissolve very rapidly in water, have low viscosity, readily leach out of formulations, and have a very high osmotic potential due to their low molecular weight. In contrast, random EO/PO copolymers are liquid over a larger molecular weight range, their rate of dissolution and viscosity can be selected for by choosing the EO:PO ratio and molecular weight, and their osmotic contribution will generally be low (due to the much higher molecular weight).
2. High molecular weight liquids (e.g., PPO) are not water soluble. In contrast, random EO/PO copolymers are water soluble and will be resorbed from the site of administration at a rate that can be predicted based upon the EO:PO ratio and molecular weight.
3. The random structure does not self associate, and most random EO/PO copolymers are water clear liquids above their melting point, unlike many poloxamers that are liquid at room temperature (e.g., poloxamer-124 or PLURONIC® L44), which range from turbid liquids to liquid pastes.
A preferred embodiment uses a branched or linear random alkylene oxide copolymer with a molecular weight of about 22,000 daltons (22K random AOC). Such a compound is commercially available from BASF Corporation as PLURACOL® V-10 (V-10). According to its manufacturer, V-10 was developed specifically for use in water-glycol fire-resistant hydraulic fluids and is additionally suitable as a water-soluble, cutting and grinding fluid and in various metal working applications. Furthermore, the manufacturer discloses that complete toxicity information on V-10 has not yet been fully developed and that the normal precautions exercised when handling any chemical should be used when working with V-10: e.g., eye protection should be used and prolonged contact with the skin should be avoided. The discovery that random AOC are useful for medical and surgical applications is novel and inventive.
Random AOC are produced by several manufacturers including BASF, Dow Chemical, and Sigma/Aldrich under the trade names PLURADOT®, PLURACOL®, SYNALOX® EPB, and EMKAROX® among others. They are available in a range of EO:PO ratios and molecular weights (e.g., 1 kg/mol to 22 kg/mol) and in linear and branched geometries, and are commonly characterized by their viscosity rather than molecular weight. Dow Chemical provides a number of random AOC with molecular weights in the range of 1,500 to 4,900 including those with the following codes: EP530, EP 1730, EP 435, EP 1660, 15-200,112-2, UCON 50-HB-5100, and UCON 50-HB-660. Sigma/Aldrich provides a number of random AOC with molecular weights in the range of 2,500 to 12,000 including those with the following codes: 43,819-7, 43,820-0, 43,818-9,40,918-9. Medical applications for PAO have been focused on block AOC. In contrast, the use of random AOC has almost exclusively been restricted to non-medical applications, and their potential for providing medical benefits has been largely overlooked.
Implants used in humans and animals may be manufactured by sintering solid particles such as polyethylene, methylmethacrylate, or titanium; or they are adapted from naturally substances such as coral in the case of porous coralline hydroxyapatite. Polyethylene, a biologically inert material, has numerous applications in surgery; it is a straight-chain hydrocarbon made by polymerizing ethylene. Hydroxyapatite and tricalcium phosphate are similar in composition to the major mineral component of bone and may be resorbed or remodeled, depending on their formulation. Methacrylate- and silicone-containing particles are not preferred.
Placement of implants into one or more bone defects is a common surgical procedure. Implant materials that allow for bone to grow into the pores are considered to be osteoconductive. Implants that have a bioactive component that induce bone formation, such as implants made from a bone removed from a different location, are considered to be osteoinductive. In the event that it is desirable that native bone eventually replaces the implant, material that can be remodeled by the body may be preferable. In certain clinical situations, such as a defect in the adult human cranium, the bone is not expected to grow, and a non-resorbable formulation is preferable. Studies have shown that in the craniofacial skeleton, a number of commonly used solid implants cause bone resorption adjacent to the site of implantation. Porous implants may not have the same effect.
The majority of porous implants that allow for tissue in growth are grossly solid structures with a microporous structure. To be clinically useful, they often need to be sculpted by the surgeon into their desired form. The microporous structure of the implant can cause the implant to adhere to tissue, much like a piece of Velcro, making the implant placement difficult. Debris deposition into the pores is another undesirable drawback to the use of porous implants. To decrease the risk of bacterial infection, the implant may be soaked in an antibiotic solution prior to use.
An implant whose pores are filled with a biocompatible excipient would be an improvement over the implants in current clinical use. Temporarily filling those pores until such time as in growth of tissue occurs would eliminate the accumulation of debris within the implant and could decrease the incidence of bacterial infection. Temporarily filling the pores using an appropriate excipient would also improve its handling characteristics to make the implant more lubricious and less damaging to tissue, thus allowing the implant to slide along tissue planes during surgical placement. The appropriate excipient could then also become adherent in the presence of body fluids and lessen the incidence of malpositioning that can occur after implant placement. The biocompatible excipient could also serve as a carrier for therapeutic products. For example, chemical compounds could be released over time as the excipient is resorbed.
The compound may be biocompatible and substantially non-toxic, have a stable shelf life, be relatively economic, and have superior handling characteristics. A carrier should allow the implant to be lubricious to glide along tissue planes, but it should also enable the implant to become adherent to surrounding structures when its final position is attained. Cohesion may be used to temporarily hold tissue together until more permanent attachments may be made. An anhydrous formulation would increase stability for the long term and reduce the risk of contamination.
In a number of clinical applications, it is advantageous to construct a porous structure by placing an aggregate of solid particles or granules that become fixed in into their desired location by the in growth of soft tissue into the spaces between the particles. Allograft bone is a substitute source for solid particles. It is readily available and precludes the surgical complications and patient morbidity associated with autologous bone as noted above. Allograft bone may be considered a collagen fiber reinforced hydroxyapatite matrix containing active bone morphogenic proteins (BMP) and can be provided in a sterile form. The mineral component may be removed from bone to form a demineralized bone matrix (DBM). Such DBM is naturally both osteoinductive and osteoconductive. Once surgically implanted, DBM is fully incorporated in the patient's tissue and it has been used in bone surgery to fill osseous defects. DBM is usually available in a lyophilized or freeze-dried and sterile form to provide for extended shelf life. The DBM in this form is usually very coarse and dry, and is difficult to manipulate by the surgeon. It is known that DBM can be supplied in a matrix of low molecular weight solvents, but these are know to be toxic to the surrounding tissue, and they form a runny composition. DBM is usually available in a lyophilized or freeze-dried and sterile form to provide for extended shelf life. The bone in this form is usually very coarse and dry, and is difficult to manipulate by the surgeon. It is known that DBM can be supplied in a matrix of low molecular weight solvents, but these are know to be toxic to the surrounding tissue, and they form a runny composition.
Inorganic materials can also provide a matrix for new bone to grow at the surgical site. These inorganic materials include hydroxyapatite obtained from sea coral or derived synthetically. Either form may be mixed with the patient's blood and/or bone marrow. Hydroxyapatite granules may be used as bone inlays or onlays. The granules can be mixed with microfibrillar collagen and blood from the patient.
Particles with sizes (i.e., the largest dimension) in the range from about 35 microns to about 500 microns (or about 50 microns to about 150 microns) are desirable to minimize the possibility of particle migration by phagocytosis and to facilitate injectability. Phagocytosis occurs where smaller particles on the order of 15 microns or less become engulfed by the cells and removed by the lymphatic system from the site where the augmentation material has been introduced into the tissues, generally by injection. At the lower end, particles greater than 15 microns (typically 35 microns or above) are too large to be phagocytosed, and can be easily separated by known sizing techniques (e.g., filtration, gel exclusion, molecular sieving). For a population of substantially spherical particles, the diameter may range from about 35 microns to about 500 microns for at least the majority of the population. Thus, it is relatively simple to produce narrow or equivalent particle size ranges that are desirable for use.
Particles may comprise at least about 10% (v/v), at least about 25% (v/v), not more than about 40% (v/v), not more than about 64% (v/v), or combinations thereof. The composition may be kneaded or otherwise worked to obtain a homogeneous distribution of particles within a random AOC-containing composition. Such working is avoided, however, if a non-homogeneous distribution is desired and different compositions may even be laminated together.
Excipients are biologically inactive substances that are associated with, often in combination, drugs, devices, and other therapeutic agents to make a therapeutic product. They may be classified by the function(s) they perform as binders, disintegrants, fillers, diluents, dispersing or suspending agents, lubricants, flow enhancers, softeners, plasticizers, and coatings. Although biologically inert, they may be critical and essential components of a therapeutic product. They can be used to enhance drug stability and bioavailability or to control the location and rate of release of the drug. They also may be required to deliver a pharmaceutical formulation by a desired route, whether oral, parenteral, enteral, or topical and, if appropriate, to enhance the appearance and palatability of the product. In many therapeutic products, excipients make up the bulk of the total dosage form. The excipient can be sterilized prior to formulation by autoclaving or irradiation, or the formulation may be sterilized as part of its production. In addition, a vehicle may be included in the therapeutic product. It may be water, another aqueous solution with a buffer and/or physiological salts, non-aqueous solution, emulsion, or suspension. The device may be a filler, anchor, catheter, implant, plate, prosthesis, screw, suture, surgical instrument, or the like; it may be made from bone (e.g., chips or powder) or a derivative thereof (e.g., demineralized bone), ceramic (e.g., calcium salt especially hydroxyapatite), glass, polyethylene, or metal (e.g., stainless steel, titanium). The drug may be a bone growth factor or morphogenic protein, hormone, other protein, nucleic acid (e.g., DNA, RNA, analogs or mixtures thereof, analgesic or anesthetic, antibiotic, anti-septic, narcotic, steroidal or nonsteroidal anti-inflammatory agent, or the like.
Random AOC compounds are also well suited as carriers or excipients for delivery of bioactive agents, medical/surgical devices (e.g., implants and instruments), and other therapeutic (e.g., non-polymeric) products. Articles may be coated with carrier or chemicals may be mixed with excipient. Sterilization may be performed in an autoclave or by irradiation for use in vivo.
Bone morphogenic proteins (BMP) and TGF-beta are two examples of bioactive substances. Other differentiation factors, stem cell factors, antibiotics, antibodies, antigens, chemotherapeutics, cytokines/chemokines, enzymes and their substrates (e.g., activators, inhibitors, or reactants), receptors (especially secreted forms and mimetics thereof) or their ligands (e.g., agonists or antagonists), signaling molecules (e.g., mediators of a signal transduction pathway, agonists or antagonists thereof) may be formulated in a composition with random AOC.
As a carrier or excipient, the compound's attributes of being at least biocompatible, substantially non-toxic, simple to manufacture, substantially non-metabolizable and readily eliminated by a human or animal are important. In addition, random AOC may act to solubilize hydrophobic substances and release them into solution. An anhydrous formulation has the benefit of providing a stable excipient to those bioactive agents that are not stable in an aqueous environment. Furthermore, if water is present, the random AOC serves to bind the water to make it unavailable to interact with the bioactive agent.
In further embodiments, random AOC compounds and random AOC-containing compositions may be used as lubricant and/or detergent.
During surgery, lubrication of instruments or other devices is usually limited to physiological saline and the patients own fluids. Use of lubricious substances derived from human or animal sources risks an immune response and the transmission of infectious agents. There is a need for a safe, biologically inert, inexpensive substance that could be used as a surgical lubricant that can be applied when needed. Such a lubricant could decrease tissue injury and/or improve the handling characteristics of devices as they are passed through tissue. Examples of injuries caused by surgical instruments are abrasive tissue burns caused by endoscopic instruments as they are moved along narrow tissue planes. Surgical implants, such as those made from porous polyethylene, are especially difficult to pass along tissue planes, since soft tissue tends to adhere to these implants. Breast implants, especially those with a textured surface that are placed through small, remote incisions, can be very difficult to place without sufficient lubrication.
Surgical instruments require that they be cleaned prior to use in surgery. The compounds and compositions disclosed here may be used as instrument milk within a cleaning apparatus for the cleaning of surgical instruments. The random AOC may be used as a detergent.
Joints of some surgical instruments (e.g., scissors and clamps) typically need to be cleaned and the joints need lubrication. Such instruments are dipped in instrument milk prior to their use in surgery. Thus, in addition to the aforementioned use as a detergent, the random AOC may be used as a lubricant.
The effectiveness of random AOC as instrument milk may be enhanced because of its biocompatibility, flowability, non-toxicity, and water solubility.
In another embodiment of the invention, random AOC compounds and random AOC-containing compositions may be used to clean and/or lubricate implantable devices.
As described above, random AOC can be used as an excipient for drug delivery or in the manufacture of other bioactive agent-containing compositions to deliver such compounds to a subject though a variety of routes, including percutaneous, enteric, intranasal or respiratory, topical, and through mucous membranes (e.g., rectum). When ingested orally in sufficient quantity, random AOC may have biological activity of its own due to the ability to draw water into the gastrointestinal tract and act as a laxative.
There are a variety of topical formulations encompassing creams, gels, and ointments, including sun blocks and wound dressings. There is an unmet need for a lubricious component which absorbs water and is thus beneficial in treating seeping wounds and stasis ulcers. Random AOC may be packaged in a bottle or tube, applied to the wound, and then optionally covered by a occlusive or non-occlusive dressing. Alternatively, the compound may be prepackaged with the dressing under aseptic conditions.
Therefore, in some embodiments, random AOC compounds and random AOC-containing composition may be used as a laxative or wound dressing.
The following examples more particularly describe the invention but are intended for illustrative purposes only, since modifications and variations will be apparent to those skilled in the art.
The biocompatibility of a random AOC (22K random AOC) was demonstrated by assessing intracutaneous reactivity, systemic toxicity, and cytotoxicity.
The 22K random AOC was evaluated for intracutaneous reactivity to test for potential irritation and sensitization. A 0.2 ml dose of the material was injected by the intracutaneous route into five separate sites on the backs of rabbits, along with controls. Observations for erythema and edema were conducted at 24, 48, and 72 hours after injection showed no evidence of irritation. The primary irritation index characterization for the 22K random AOC was negligible.
The 22K random AOC was evaluated for systemic toxicity in accordance with the guidelines of the United States Pharmacopoeia and the International Organization for Standardization (ISO) 10993. A single 25 mvkg body weight dose of the material was injected into mice by the intravenous route. The animals were observed at timed intervals for 7 days without any evidence of systemic toxicity.
Cytotoxicity was assessed using an in vitro biocompatibility study based on ISO 10993. A solution was prepared supplemented with 5% serum and 2% antibiotics, placed over confluent monolayers of L-929 mouse fibroblast cells propagated in 5% CO2, and incubated at 37° C. in the presence of 5% CO2for 48 hours. The monolayers were examined microscopically at 48 hours and showed no evidence of a change in cell morphology, cell lysis, or cell toxicity.
The in vivo elimination of a random AOC (22K random AOC) was studied in a rat model. The urinary and fecal elimination of3H-labeled 22K random AOC from adult Sprague-Dawley rats was determined. Each rat was injected subcutaneously with 10 mg of [3H]22K random AOC with a radioactivity of 50 μCi. Rats were housed individually in stainless steel metabolism cages after injection; urine and feces were collected at 24-hour time intervals over a 168-hour period. The radiolabeled22K random AOC was predominantly excreted in the rats' urine (about 60% to about 80%), with the remainder excreted in their feces. Most of the radiolabel (about 55% to about 70%) was excreted within the first 24 hours after injection.
The utility of random AOC compounds as detergents may be assessed. Their surfactant activity and ability to remove stains or contaminants from the surface of a device or instrument can be compared to other detergents used in clinical settings. Viscous compositions containing random AOC may be used in situations where the cleanser is intended to adhere to the surface in need of deep cleansing; otherwise, non-viscous compositions may be used for quick washing and rinsing. Biocompatibility of random AOC would be advantageous because of the ease with which the cleaned device or instrument re-enters use in the clinic. This is an alternative to harsh detergent cleansers.
The utility of random AOC compounds as lubricants may be assessed. Their ability to make a medical device, surgical implant, or instrument slippery can be compared to other lubricants used in clinical settings. Compositions containing random AOC of varying viscosity (e.g., oil to grease) may be used depending on the situation. The biocompatibility of random AOC and its rapid elimination would be advantageous because of the compound's safety.
A bioactive agent (e.g., carbohydrates, lipids, natural products and synthetic analogs thereof, nucleic acids, small molecules synthesized by man, proteins, antibiotics, antibodies, antigens, chemotherapeutics, imaging and contrast agents, radiotherapeutics, receptors or their ligands) may be formulated with a random AOC (22K random AOC). The circulation of the bioactive agent in the body and its elimination, the catabolism of the bioactive agent, and safety and effectiveness of therapy may be compared to aqueous solutions and compounds known to assist in the solubilization of hydrophobic molecules.
Patents, patent applications, books, and other publications cited herein are incorporated by reference in their entirety.
In stating a numerical range, it should be understood that all values within the range are also described (e.g., one to ten also includes every integer value between one and ten as well as all intermediate ranges such as two to ten, one to five, and three to eight). The term “about” may refer to the statistical uncertainty associated with a measurement or the variability in a numerical quantity which a person skilled in the art would understand does not affect operation of the invention or its patentability.
All modifications and substitutions that come within the meaning of the claims and the range of their legal equivalents are to be embraced within their scope. A claim using the transition “comprising” allows the inclusion of other elements to be within the scope of the claim; the invention is also described by such claims using the transitional phrase “consisting essentially of” (i.e., allowing the inclusion of other elements to be within the scope of the claim if they do not materially affect operation of the invention) and the transition “consisting” (i.e., allowing only the elements listed in the claim other than impurities or inconsequential activities which are ordinarily associated with the invention) instead of the “comprising” term. Any of these three transitions can be used to claim the invention.
It should be understood that an element described in this specification should not be construed as a limitation of the claimed invention unless it is explicitly recited in the claims. Thus, the granted claims are the basis for determining the scope of legal protection instead of a limitation from the specification which is read into the claims. In contradistinction, the prior art is explicitly excluded from the invention to the extent of specific embodiments that would anticipate the claimed invention or destroy novelty.
Moreover, no particular relationship between or among limitations of a claim is intended unless such relationship is explicitly recited in the claim (e.g., the arrangement of components in a product claim or order of steps in a method claim is not a limitation of the claim unless explicitly stated to be so). All possible combinations and permutations of individual elements disclosed herein are considered to be aspects of the invention. Similarly, generalizations of the invention's description are considered to be part of the invention.
From the foregoing, it would be apparent to a person of skill in this art that the invention can be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments should be considered only as illustrative, not restrictive, because the scope of the legal protection provided for the invention will be indicated by the appended claims rather than by this specification.