JP2009530440A - Oxidized microbial cellulose and uses thereof - Google Patents

Abstract

This application describes bioabsorbable biocellulose suitable for medical and surgical applications. In particular, the present invention describes periodate oxidized microbial cellulose that can be produced to have any mechanical and degradation profile depending on the desired use of the oxidized cellulose.

Description

This application claims the benefit of US Provisional Application No. 60 / 781,328, filed March 13, 2006, the entire contents of which are hereby incorporated by reference.

The present invention relates to oxidized polysaccharide materials suitable for medical and surgical applications. The present invention specifically describes periodate oxidized microbial cellulose made to have specific mechanical and degradation profiles, depending on the desired oxidized cellulose application.

  The invention also provides bioabsorbability of periodate oxidized microbial cellulose in human tissue substitutes, closure reinforcement, suture reinforcement, tissue regeneration induction, musculoskeletal applications, active agent delivery, and tissue engineering scaffolds ( bioresorbable) for use as a matrix.

BACKGROUND OF THE INVENTION Oxidized cellulose is a hemostatic agent (eg, SURGICEL ™, Ethicon, Somerville, NJ and Oxycell ™, Becton-Dickinson, Morris Plains, NJ) and a barrier to prevent post-surgical adhesions. It has long been manufactured as a material (eg INTERCEED ™, Ethicon, Somerville, NJ) for medical use. An important feature of oxidized cellulose is that it can be absorbed when implanted in the body. On the other hand, in the case of non-oxidized cellulose, it cannot be absorbed. The proposed mechanism of resorption of oxidized cellulose is that the polymer is hydrolyzed into smaller oligosaccharides, which are further metabolized and eliminated from the body. Complete absorption of such materials can be achieved substantially between 2 weeks and 3 months after implantation.

  Most commercially available oxidized celluloses are plant derived or synthetically regenerated from which the resulting medical device is made. The material is first processed to the desired physical shape and woven or knitted as a fabric prior to exposure to the oxidizing agent. The only oxidant currently used to make oxidized cellulose medical products is considered dinitrogen tetroxide. The use of other oxidizing agents has also been proposed, but no commercially available oxidized cellulose medical devices made by techniques other than the nitrous oxide oxidation process have been reported to date. Thus, the majority of clinical data on oxidized cellulose includes the form of non-microbial cellulose oxidized by nitrous oxide.

  Other oxidation procedures have been developed to produce bioabsorbable cellulose, but these processes do not mention the use of microbial-derived cellulose. For example, Kumar (US Pat. No. 6,800,733) discloses sodium metaperiodate as an oxidizing agent for regenerated cellulose. Furthermore, Singh discloses the use of sodium metaperiodate for the oxidation of cellulose, but only describes non-microbial derived powdered cellulose.

  Even when Kumar and Singh are combined, it is not clear that the use of microbial cellulose as a starting material for cellulose oxidized with periodate leads to a mechanically functional material. In fact, Kumar specifically denies the use of microbial-derived cellulose because microbial cellulose is not plastic and microbial cellulose loses higher order structure in the solvent dissolution step. Also, it is not clear from Singh that microbial cellulose is suitable because of the crystal and layered structure of microbial cellulose. In fact, the present inventors have unexpectedly been able to oxidize microbial cellulose and maintain mechanical strength when producing biodegradable materials.

  Furthermore, neither Kumar nor Singh mentions the use of supporting electrolytes during the periodate oxidation process or the use of different drying techniques to give different mechanical and degradation properties to oxidized cellulose. . Similarly, Jaschinski et al. (US Pat. No. 6,663,555) described a process in conjunction with TEMPO to produce a material in which oxidation occurs at all three alcohol sites of the anhydroglucose repeat unit. The polysaccharide oxidation process with iodate is described. Jaschinski et al., However, do not describe microbial cellulose as a suitable polysaccharide material and do not rely on the specific oxidative properties of periodate in combination with a supporting electrolyte.

Kim et al. Also describe the periodate oxidation of plant cellulose obtained from seaweed. The oxidation process consists of oxidizing cellulose microfibers for a desired reaction time at a ratio of 10.7 mol NaIO ₄ to 1 mol glucopyranoside. Again, there is no mention of using a supporting electrolyte in the oxidation process or specific drying techniques. Kim concludes that choosing the right starting material to control the oxidation process is very important and proves that not all cellulose reacts similarly when oxidized with periodate. is doing.

  Ring et al. (US Pat. Nos. 4,588,400, 3,655,4 and 4,788,146) disclose the use of microbial cellulose for topical medical applications. However, it does not describe the oxidation of such films to produce bioabsorbable oxidized microbial cellulose for use as an implantable medical device or tissue engineering matrix. Hutchens et al. (US Patent Application No. 20040096509) describes microbial cellulose, but does not disclose a bioabsorbable version of cellulose.

  There is a need in the art for oxidized microbial cellulose that can have a certain mechanical and degradation profile suitable for many medical and surgical applications. In fact, the use of biological cellulose rather than regenerated oxidized amorphous cellulose allows the production of oxidized cellulose films that can maintain a high degree of layered structure and crystallinity. The nonwoven layered structure of microbial cellulose allows the material to maintain mechanical strength and at the same time be bioabsorbable.

Kumar, U.S. Patent No. 6800753 Jaschinski et al., US Pat. No. 6,663,555 Ring et al., US Pat. No. 4,588,400 Ring et al., US Pat. No. 4,655,758 Ring et al., US Pat. No. 4,788,146 Hutchens et al., US Patent Application No. 20040096509

SUMMARY OF THE INVENTION An object of the present invention is to provide a new bioabsorbable type of microbial cellulose that can be used in a variety of medical and surgical applications. Further objectives are the desired physical and scientific for use as a resorbable matrix in human tissue substitutes, closure reinforcement, suture reinforcement, tissue regeneration guidance, musculoskeletal applications, active agent delivery, and tissue engineering scaffolds. To provide a resorbable microbial cellulose having specific characteristics. Microbial cellulose is oxidized, but the desired degree of oxidation is oxidant concentration, oxidant solution volume, oxidant / cellulose ratio, supporting electrolyte concentration, presoaked in supporting electrolyte solution, reaction temperature, reaction period, etc. This is achieved by changing the elements or combinations thereof.

The present invention also provides a method of producing oxidized microbial cellulose that can be specifically produced to have specific mechanical and degradation properties, depending on the cellulose application. The method includes (i) producing microbial cellulose, and (ii) oxidizing the microbial cellulose with a solution of periodate, such as sodium metaperiodate. The oxidation process may be performed with or without a supporting electrolyte, and drying of the oxidized microbial cellulose may be accomplished by drying techniques such as air drying, oven drying, supercritical CO ₂ drying, or solvent dehydration, or combinations thereof. It can be carried out. The method optionally also includes a presoak process with or without a supporting electrolyte prior to oxidation.

  Yet another object is to provide a novel method or manufacturing process for the preparation of the aforementioned materials that provides the desired properties for each particular product application.

  Also, a method for producing a bioabsorbable medical material, the method comprising (i) a step of producing microbial cellulose, and (ii) a step of oxidizing microbial cellulose with a solution of sodium metaperiodate Describe. In one embodiment, the bioabsorbable medical material is a suture, hemostatic agent, wound covering, implantable tissue substitute, tissue engineering matrix, or anti-adhesion device. The medical material is, for example, musculoskeletal tissue, nerve tissue such as dura mater, cardiovascular tissue, abdominal tissue repair and / or regeneration, bladder neck fixation, gastric formation, hernia repair, gastrointestinal closure, tissue regeneration for dental use It can be used for guidance or fillers for plastic or reconstructive surgery.

DETAILED DESCRIPTION OF THE INVENTION Unless otherwise stated, “one (a, an)” and “the” refer to at least one.

  “Bioresorbed”, “bioresorbable”, “bioresorption” and their altered expressions are either excluded or applied naturally after topical application or internalization in mammals. Represents a substance to be decomposed.

Oxidized microbial cellulose In one embodiment, the present invention comprises oxidized microbial cellulose. In one embodiment, the microbial cellulose can be obtained from Acetobacter, Rhizobium, Agrobacterium, Pseudomonas, or Sphaerotilus. However, the microbial cellulose is preferably obtained from Acetobacter xylinum. The method for obtaining microbial cellulose can be carried out by methods well known in the art. See, for example, US Pat. No. 6,659,518, which is incorporated herein by reference in its entirety.

  In other embodiments, a supporting electrolyte is added prior to and / or during the oxidation process to produce an oxidized material that is intended to be bioabsorbed while retaining its original mechanical properties. In addition, a final drying step is utilized to provide additional means to control both the mechanical and degradation properties of the oxidized biocellulose. The final degree of oxidation of the microbial cellulose can be tailored to the specific product application, but preferably the degree of oxidation is at the desired degradation rate, including rates ranging from 1 day to over 1 year. Sufficient to allow the cellulose to be bioabsorbed. In other words, oxidized microbial cellulose is about 1, 2, 3, 4, or 5 days, or about 1, 2, or 3 weeks, or about 1, 2, 3, 4, 5, 6, 7, 8, 9 , 10 or 11 months, or about 1 or 2 years.

  The oxidized microbial cellulose or the mixture containing oxidized microbial cellulose of the present invention can be used in various forms such as pads, thin films, strips, sutures, films, fluids, suspensions, putty, pastes and gels. Preferred oxidized microbial cellulose forms are multi-layered cross-section thin films or pads, or putty / paste consistency for filling or filling defects. Other forms are possible depending on the requirements of the biomaterial.

  Oxidized microbial cellulose of the present invention comprises a wound dressing or bioabsorbable matrix for human tissue substitutes, wound closure reinforcement, suture reinforcement, tissue regeneration guidance, musculoskeletal applications, active agent delivery, and tissue engineering scaffolds. Useful in a variety of medical applications, including In particular, the oxidized microbial cellulose of the present invention includes, among others, bioabsorbable hemostatic agents for controlling bleeding, wound dressings, implantable adhesion barriers or anti-adhesive devices for use in surgery, urology and aesthetic applications. Alternative to collagen, for implantable surgery, bioactive agents or carriers for drugs to form implantable drug delivery systems or sustained delivery systems, physiologically acceptable Gels formed with the resulting solution, gels or solutions for eye drops and eye drops applications, gels or fluids for skin augmentation and other cosmetic applications, bone fillers, fitted sheaths, repair skeletal defects Surgical augmentation devices such as implants or other bone applications, tissue substitutes, bladder neck suspension sling, lower back Various types of prostheses, such as knee can be used as a mounting sheath, the scaffold ligament or tendon for neoplasia or breast augmentation or breast reconstruction tool, to articulate.

  It is believed that the oxidized microbial cellulose described here maintains the growth and proliferation of both epidermal and dermal cells, which leads to the formation of biologically active intact skin. It is also considered to support the growth of cartilage-derived chondrocytes for the generation of cartilage tissue and to prevent adhesion of platelets and smooth muscles for use as vascular grafts. In addition, it supports the growth of nerve-derived Schwann cells that deliver growth factors used for nerve regeneration, supports the growth of corneal epithelial cells, and may support adhesion and permeation for nutrient and fluid transport. . It can also be used to support the formation of an artificial cornea and the proliferation of mesenchymal cells that lead to various tissue structures depending on the transplanted region.

  In addition, the oxidized microbial cellulose of the present invention can be used in combination with other materials such as polymers, collagen, proteins, peptides, cells, other forms of cellulose and biologically active agents to provide efficacy for specific applications. Can be enhanced. For example, the oxidized microbial cellulose described herein may be resorbable and non-resorbable bios comprising tricalcium phosphate, dicalcium phosphate, hydroxyapatite, and collagen, polylactic acid, polyglycolic acid, polyε-caprolactone, etc. It can be mixed with various biomaterials such as polymers to form a mixture. Moisturizers and other materials such as polyols such as glycerin and polyethylene glycol may be incorporated to adjust the physical and drying characteristics of oxidized microbial cellulose. In addition, microbial cellulose and mixtures include bone morphogenetic protein (BMP), platelet derived growth factor (PDGF), transforming growth factor (TGF), growth differentiation factor (GDF), insulin-like growth factor (IGF), epidermal growth factor (EGF). ), Demineralized bone matrix (DBM), active agents such as factor VIII can also be added. Similarly, differentiated and undifferentiated viable cells can be mixed with biogenic oxidized cellulose for the growth of bone, cartilage, skin, blood vessels, organs and the like.

A method of producing oxidized microbial cellulose comprising: (i) a step of recovering a microbial raw cellulose thin film from bacteria such as Acetobacter xylinum; and (ii) sodium periodate and, optionally, an alkali metal A method comprising oxidizing a microbial cellulose with a solution containing a salt such as a transition metal or a salt from a polymer electrolyte is described. Preferably the salt is NaCl. Salt contributes to more uniform oxidation. In one aspect, the method further comprises a dehydration step. As described below, the dehydration step can be air dried, solvent dried (eg, with a water miscible solvent such as methanol, ethanol, propanol, isopropanol, acetone, tetrahydrofuran, butanol, 2-butanol, glycerol or mixtures thereof), followed by It may be air drying, oven drying, or supercritical CO ₂ drying.

  As described herein, microbial cellulose can be obtained by inoculating bacteria such as A. xylinum in a sterilized culture medium. The inoculated medium is then used to fill the bioreactor tray to a certain capacity, eg 50, 110, 220, 330, 360 and 440 g. These are then cultured for about 4 days (50 g sample) to 21 days (440 g sample) until the desired cellulose content is reached.

  After cellulose recovery, the microbial cellulose film is chemically treated to remove most non-cellulosic material, including making the cellulose non-pyrogenic. All processing / molding takes place after the cellulose has grown. Depending on the final desired properties, the material can be shaped before or after oxidation. The pad can be cleaned with, for example, sodium hydroxide to destroy the pyrogen, but other cleaning methods are also known. The pad can also be bleached with a solution such as hydrogen peroxide and water, usually in the range of 0.25% to about 3% hydrogen peroxide.

  The thin film is then soaked in an aqueous solution, optionally with a supporting electrolyte, for about 30 minutes to about 24 hours, and then treated with an oxidant soaking solution, preferably sodium metaperiodate, optionally including the supporting electrolyte. . The electrolyte solution may be a 0.001-1 M salt solution, preferably a 0.1-0.5 M NaCl solution.

  The oxidant concentration and reaction volume are selected to provide the desired periodate / cellulose ratio to produce the desired level of oxidation of oxidized microbial cellulose. Excess oxidant is then removed and the material is made into a final form by final processing, addition of the desired active agent, packaging, and sterilization.

  Depending on the desired physical and chemical properties of the microbial cellulose, the oxidant concentration, reaction temperature, periodate / cellulose ratio and duration of reaction can be varied to produce different levels of oxidation. For example, the molar concentration of the oxidizing agent is in the range of 0.005 to 0.5 M, the temperature is about 5 to 50 ° C. (ie ± 5 ° C. at 5 to 50 ° C.), and the ratio of periodate to cellulose is 0.1 to 10 Good. Preferably, the microbial cellulose may be oxidized for at least 30 minutes, or 1, 6, 12 or 24 hours, at least 1 day or at least 2 days or longer. Thus, variable oxidation also affects the degradation rate of the material, allowing higher resorption rates at high oxidation levels.

  In another preferred embodiment of the method for producing oxidized microbial cellulose, deoxidization is followed by chemical methods using polyamines such as polyethyleneamine or polyalcohols such as polyvinyl alcohol, glycerol, and ethylenediamine, or oxidized microorganisms by radiation. Crosslinks cellulose and changes the properties of oxidized cellulose.

  Since the degradation of oxidized cellulose is due to hydrolysis of the cellulose polymer, the oxidized material should be dehydrated after oxidation to minimize degradation prior to use. Thus, the dehydration process can have a significant impact on the mechanical and degradation properties of oxidized biocellulose. Indeed, depending on the final application, the dehydration process provides an additional means for controlling the mechanical and degradation properties of oxidized biocellulose.

Air drying or air drying after solvent dehydration yields a material with low mechanical strength and reduced degradation properties. As described herein, air drying refers to drying at a pressure of about 20-50 ° C. at normal atmospheric pressure. As described above, solvent dehydration involves water-miscible solvents such as methanol, ethanol, propanol, isopropanol, acetone, or mixtures thereof. Supercritical CO ₂ drying provides a biocellulose material that retains most of its original strength and provides an open porous structure that exhibits faster bioabsorption rates.

  Many other variations and details of construction, composition, and construction will be apparent to those skilled in the art, and such variations are within the scope of the present invention.

Examples Example 1 Production of Microbial Cellulose with Acetobacter xylinum This example describes the production of microbial cellulose with Acetobacter xylinum suitable for use in preparing oxidized cellulose.

  Prior to culture, A. xylinum in the growth vessel was inoculated into a sterile culture. This broth is based on a modified preparation of Schramm-Hestrin broth as described in US patent application Ser. No. 10/132171. The inoculated culture was used to fill bioreactor trays to specific volumes such as 50, 110, 220, 330, 360, and 440 g. These trays are covered with plastic sheets and vented ports are added to expose them to oxygen during growth. The trays were then incubated under static conditions at a constant temperature of 30 ° C. (4 days for 50 g to 21 days for 440 g) until optimal growth was achieved.

Example 2 Treatment of Microbial Cellulose
A. Microbial cellulose recovered from xylinum was chemically treated to remove bacterial by-products and residual culture. However, before the chemical treatment, the thin film was first pressed with an air press to remove excess culture medium.

  The pressed cellulose film was then chemically treated. This process involves dynamic soaking for about 1 hour in a tank of 2-8% caustic solution containing sodium hydroxide, heated to 75 ° C., for exothermic heat. After this chemical treatment, it was continuously rinsed with filtered water, and the caustic solution was removed from the treated thin film. After rinsing, the film was treated with 0.25% hydrogen peroxide for 1 hour at 40 ° C. to give a “whitened” appearance. After chemical treatment, the microbial cellulose film was again subjected to a dehydration press with an air press to obtain the desired cellulose content, and then subjected to various post chemical treatment procedures.

Example 3 Oxidation of Microbial Cellulose A chemically treated cellulose film was oxidized. Cellulose samples were left in 0.1 M NaIO ₄ solution at 40 ° C. for 4 or 24 hours. In order to prevent side reactions of cellulose, the incubation was carried out in a closed reaction vessel in a light shielded incubator. After oxidation, the sample was rinsed to remove residual NaIO ₄ , drilled to the desired size, packaged, and sterilized by gamma irradiation for implantation.

Example 4 Study on In Vivo Degradation of Oxidized Microbial Cellulose In vivo studies were performed to evaluate the degradation properties of oxidized cellulose produced as described in Example 3 above.

  Fifteen female Sprague-Dawley rats were implanted subcutaneously at 3 sites in the abdomen with 2 test materials per animal and 1 control. Cellulose oxidized for 4 hours and 24 hours was used as a test material, and non-oxidized cellulose was used as a control.

  At 2, 4, and 6 weeks after transplantation, 5 animals were sacrificed for each time point and all transplants were explanted. As expected, there was some fibrous attachment of the sample to the skin, muscle and other soft tissues at 2 weeks. At 4 and 6 weeks post-transplantation, there was essentially no overall fibrous response in the surrounding tissue.

  Signs of degradation of oxidized cellulose were already apparent at 4 weeks post-transplant, as evidenced in Table 1 and FIG. Compared to the control, the decrease in size and weight of the oxidized sample that occurred during the six weeks is indicative of degradation that occurred over time. As expected, the more strongly oxidized sample (24 hours) showed a more aggressive degradation pattern than the 4 hour oxidized sample.

  When implanted in rats, the oxidized material showed good biocompatibility. Furthermore, implants engineered to degrade at different times led to the expected results.

Table 1 Weight of implants after sacrifice at 4 and 6 weeks

Example 5 Effect of periodate / cellulose ratio on the oxidation of microbial cellulose using sodium metaperiodate
NaIO ₄ solutions with various periodate concentrations ranging from 6-25 mM were prepared. The oxidation solution also contained 0.189 M NaCl. Cellulose samples (2 × 4 cm strips) were weighed and soaked in 0.189 M NaCl solution for 3 hours prior to periodate incubation. IO _4: Cellulose ratio samples were incubated in periodate solution ranging from 0.5 to 2. Incubation was carried out for 17 hours at a temperature of 30 ± 2 ° C. in a closed reaction vessel in a light-shielded incubator (to prevent cellulose side reaction). After incubation, the sample was removed from the oxidation solution and left in the extraction solution containing 35 mL water for 2-5 hours. After removing excess NaIO ₄ , the biocellulose sample was dried by one of three processes: supercritical drying (SCD), air drying (AD), or solvent exchange air drying (SD). See Examples 9 and 10 below.

  The oxidation level was determined using UV / Vis analysis of the reaction and extraction solutions by measuring the absorbance of periodate at 290 nm. The moles of periodate in the reaction solution and extraction solution were subtracted from the moles of periodate during the initial reaction. Periodate oxidation occurred at a 1: 1 ratio with glucose repeat units in cellulose. Therefore, the oxidation percentage based on the number of oxidized repeat units and the dry weight of the biocellulose sample was calculated (Figure 2).

Example 6 Effect of NaCl on Oxidation and In Vitro Degradation of Oxidized Microbial Cellulose As described in Example 5, two sets of samples were made with an IO ₄ : cellulose ratio of 0.75. One series was pre-soaked in 0.189 NaCl for 6 hours prior to oxidation in the presence of NaCl. The other series was immersed in water for 6 hours prior to oxidation in the absence of NaCl. Oxidation in the presence of NaCl resulted in higher degrees of oxidation (Table 2) and differences in degradation characteristics.

  The addition of the supporting electrolyte led to further expansion of the cellulose polymer from screening for hydrogen bonds between polymer chains. While not intending to be bound by a particular theory, it is believed that increased swelling results in increased access to more oxidation sites and allows for more uniform oxidation. After oxidation, the sample was dried by SCD process.

In order to evaluate the degradation properties of oxidized cellulose produced as described above, in vitro studies were conducted through analysis of degradation products as well as changes in mechanical strength. The sample was 37 in 25 mL buffered saline solution (pH 8 7.4 ± 0.2, NaCl 8 g, KCl 0.4 g, Na ₂ HPO ₄ 0.8 g, KH ₂ PO ₄ 0.14 g, dextrose 1.0 g in 1.0 L water). Incubated at ± 2 ° C. Analysis was performed on days 0, 1, 3 and 7. At each time point, a small aliquot was analyzed by measuring the absorbance of the carbonyl absorbance at 232 nm. For mechanical strength, measure the suture pull-out force using Prolene 5.0 sutures and a United tensile tester (SSTM 2KM model). Determined by.

  As a result of adding NaCl to the oxidizing solution, a material different from cellulose oxidized in the absence of NaCl was obtained. FIG. 3 demonstrates that the NaCl material has a faster decomposition rate than the material oxidized in the absence of NaCl. Table 2 also shows that the initial strength of the oxidized material in the presence of NaCl was higher than that in the absence of NaCl, but with the increase in the decomposition rate over time, a similar decrease in suture pulling force was obtained. Indicates that

TABLE 2 Oxidation and suture pull-out values of biocellulose oxidized in the presence and absence of NaCl

Example 7 Supercritical CO ₂ Treatment of Oxidized Microbial Cellulose After periodate oxidation by the method of Example 5, the sample was further treated with supercritical CO ₂ . Samples were subjected to a series of exchanges in 100% methanol for up to 48 hours. Cellulose was then wrapped in polypropylene mesh and placed in a supercritical fluid exchange system (150 SFE system, Super Critical Fluid Technologies, Inc., Newark, DE). CO ₂ operating parameters (1500-1600 psi and 40 ° C.) were achieved and held for an exchange period of 1-3 hours. After this cycle, the oxidized material was removed from the bath in dry form and weighed to determine the cellulose content. The decomposition experiment described in Example 5 was performed on the dried sample.

  FIG. 4 shows that the intensity decreased by about 18% due to the oxidation process relative to the non-oxidized control sample (6.02 ± 1.05 N). One day after disassembly, the suture pull force decreased from 4.92 N to 1.53 N and then gradually decreased to about 1 N over 6 days.

Example 8 X-ray diffraction of oxidized sample As a result of SCD treatment of oxidized biocellulose, a material that maintains a high degree of crystallinity of the original non-oxidized material was obtained. As described in the above examples, biocellulose samples were prepared to have an oxidation level of 10-28% and dried as described in this example.

  X-ray diffraction data was collected using a Rigaku Miniflex X-ray Diffractometer, which generates X-rays by irradiating a Cu target with a 35 keV electron beam. Data were collected from 5 ° to 60 ° 2θ. Data analysis was performed using JADE version 3.0 software. At 10% and 28% oxidation compared to the non-oxidized sample, no significant change in the crystal structure was seen in the diffraction chart (Figure 5). At higher oxidations, the 2θ value shows a small change in configuration and represents a shift in the lattice spacing, but the overall crystal structure is unchanged. Maintenance of the crystal structure after oxidation contributed to the oxidized biocellulose maintaining mechanical strength after the oxidation and drying process.

Example 9 Air Drying of Oxidized Microbial Cellulose After periodate oxidation by the method of Example 5, the sample was further processed using air drying. The wet sample was placed between two polypropylene meshes and placed in a 37 ° C. incubator for 18-36 hours. After the drying process, a sample was removed and weighed to determine the cellulose content. FIG. 3 shows that the mechanical strength changes dramatically with post-oxidation air drying as the strength decreases from 10 N (non-oxidizing control) to 1.35 N at t = 0. Furthermore, at t = 0, the strength is reduced by 70% compared to the oxidized SCD material.

TABLE 3 Suture pull values of oxidized microbial cellulose after various drying processes

Example 10 Solvent Dehydration of Oxidized Microbial Cellulose and Subsequent Air Drying Following periodate oxidation by the method of Example 5, the sample was further treated with a solvent dehydration step followed by air drying. Samples were subjected to a series of exchanges in 100% methanol for up to 48 hours. Instead of using SCD treatment, after solvent exchange, the sample was placed between two polypropylene meshes and left in a 37 ° C. incubator for 18-24 hours. After the drying process, a sample was removed and weighed to determine the cellulose content. As the SD sample showed a decrease from 8.4 N (non-oxidized control) to 1.3 N after oxidation, the post-oxidation mechanical strength dropped dramatically as seen in the AD sample. Both AD and CD oxidized samples show similar suture pull-out values (Table 3), suggesting that the structure of the resulting material is similar.

Overall observation of oxidized microbial cellulose explants in the 4th week. Effect of periodate: cellulose ratio on oxidation (%) of biocellulose. Formation of degradation products over 7 days of biocellulose samples oxidized with oxidizing solution with or without NaCl. A / (g cellulose) represents the absorbance at 232 nm divided by the weight (g) of cellulose obtained by weighing a dry cellulose sample. Change in suture pull force over 7 days of oxidized cellulose after SCD process. Non-oxidized (A), 10% oxidized (B), and 25% oxidized (C) biocellulose X-ray diffraction records.

Claims (21)

A method of producing bioabsorbable oxidized biocellulose, comprising: (i) producing microbial cellulose; and (ii) oxidizing the microbial cellulose with a solution of sodium metaperiodate.   2. The method for producing bioabsorbable oxidized biocellulose according to claim 1, further comprising a step of presoaking biocellulose in an aqueous solution containing an electrolyte before the oxidation treatment.   3. The method of claim 2, wherein the electrolyte is NaCl.   3. The method of claim 2, wherein the microbial cellulose is produced by Acetobacter xylinum.   Selected from the group consisting of periodate concentration, periodate solution amount, periodate / cellulose ratio, supporting electrolyte concentration, pre-soaking in supporting electrolyte solution, reaction temperature, reaction period, and combinations thereof 3. The method of claim 2, wherein the desired degree of oxidation is achieved by changing the elements.   6. The method of claim 5, wherein the molar concentration of periodate ranges from 0.005M to 1.0M.   6. The method of claim 5, wherein the ratio of periodate to cellulose is in the range of 0.05-10.   The method according to claim 5, wherein the temperature is from 5C to 50C.   6. The method of claim 5, wherein the solution is reacted for 30 minutes to 24 hours.   6. The method of claim 5, wherein the supporting electrolyte concentration is in the range of 0.001M to 1.0M.   The method of claim 1, further comprising a pre-oxidation dipping in an aqueous solution without electrolyte.   3. The method of claim 2, wherein the pre-oxidation soak comprises a salt selected from the group consisting of alkali metals, transition metals, and polyelectrolytes.   The method of claim 2, wherein the pre-oxidation soaking ranges from 30 minutes to 24 hours.   Oxidized biocellulose by a method selected from the group consisting of air drying, oven drying, manual dehydration, solvent dehydration, drying on a desiccant, drying under vacuum, freeze drying, and supercritical fluid drying. The method according to claim 2, wherein the method is dried.   15. The method of claim 14, wherein the oxidized biocellulose is solvent dehydrated with acetone, methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, tetrahydrofuran, or glycerol. The oxidation biocellulose solvent dehydrated with methanol or acetone, then is replaced with supercritical CO _2, The method of claim 14, wherein.   15. The method of claim 14, wherein the material is allowed to stand in a chamber having a temperature in the range of 20 ° C to 100 ° C. (I) A method for producing a bioabsorbable medical material comprising the steps of producing microbial cellulose, and (ii) oxidizing the microbial cellulose with a solution of sodium metaperiodate.   19. The method of claim 18, further comprising the step of presoaking biocellulose in an aqueous solution comprising an electrolyte prior to the oxidative treatment.   19. The bioabsorbable medical material of claim 18, selected from the group consisting of sutures, hemostats, wound coverings, implantable tissue substitutes, tissue engineering matrices, or anti-adhesives.   Medical material is musculoskeletal tissue, nerve tissue such as dura mater, cardiovascular tissue, abdominal tissue repair and / or regeneration, bladder neck fixation, gastroplasty, hernia repair, gastrointestinal closure, tissue regeneration induction for dental use, or 19. The method of claim 18, wherein the method is used for a plastic or reconstructive surgical filler.

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