Oxidized Cellulose - an overview (2023)

Oxidized Cellulose

Oxidized regenerated cellulose is branded as Surgicel Fibrillar and Surgicel Nu-Knit (both produced by Ethicon, Inc., Somerville, New Jersey). The material offers handling characteristics superior to those of gelatin foam, and the knitted fabric can be trimmed to fit any size. It does not stick to instruments and can easily be held firmly against bleeding tissue until hemostasis is achieved. Surgicel Fibrillar resembles cotton in consistency and remains pliable when laid into a wound. These products should not be moistened before use because greater hemostatic effect is exerted when they are applied dry.

Oxidized cellulose products result in a decreased local pH. There are theoretical advantages to this effect, including antimicrobial effects and hemostatic effects. Disadvantages of acidity include inactivation of other topical agents, such as thrombin (which should not be used together with cellulose) and potential increases in inflammation resulting in delayed wound healing.¹¹⁰

The observed discoloration of cellulose products following blood contact are attributable to low pH resulting in RBC lysis and hematin generation. Only the minimal necessary amount of product should be applied, with any excess agent removed after hemostasis is achieved.

Conclusions

CNF extracted from raw jute using the one step nitro-oxidation method were found to be highly effective material for remediation of lead(II) ions from contaminated water. The maximum lead removal capacity of CNF, calculated using the Langmuir model, was found to be higher than the materials reported in the literature so far. The adsorption mechanism at low (≤1000ppm) lead(II) ion concentration is mainly due to electrostatic interactions between lead(II) ions and CNF, while that at high (≥1000ppm) lead(II) ion concentration is dominated by the growth of lead nanocrystals on CNF surface. Now, it is clear that CNF can be used either in the form of coagulants, adsorbents, or flocculants in both dispersion and membrane formats to removal toxic metal ions form drinking water.

Oxidized Cellulose (Surgicel)

Oxidized cellulose consists of absorbable fibers prepared from cellulose. Woven strips or sheets of cellulose can be cut and held with firm pressure on the wound bed. Oxidized cellulose provides a meshwork for coagulation and causes local vasoconstriction. This preparation is moderately priced, easy to handle, and mildly bactericidal.

Foreign-body reaction is possible if excessive amounts of cellulose are left in a wound. Cellulose should not be used under grafts or flaps because it separates the graft from the blood supply. Some experts believe that the removal of oxidized cellulose after obtaining hemostasis frequently produces rebleeding.

Drug Class:

Cellulose hemostatic

Non–Fibrin-Based Surgical Hemostats

In contrast to the fibrin-based agents, other hemostatic agents such as thrombin-soaked oxidized cellulose particles (Floseal [Baxter, Glendale, CA]; Surgiflo [Johnson & Johnson, New Brunswick, NJ]) have no adhesive capability but are excellent hemostatic agents in the presence of active bleeding from parenchymal surfaces such as a partial nephrectomy bed, a liver or spleen laceration, or an oozing adrenal bed. These agents are composed of human-derived thrombin and bovine- or porcine-derived gelatin matrix. The gelatin granules swell 10% to 20% to produce a tamponade effect, whereas the high concentration of thrombin promotes conversion of fibrinogen to fibrin, as well as activating platelets and several coagulation factors. This agent is also prepared by the scrub assistant; it takes 2 minutes to prepare and is usable for 2 hours. It is applied through a tube applicator with a syringe. It is most effective when pressure is applied after its delivery; this can be done either with an instrument (e.g., 10-mm gauze-tipped dissector) or with a bolster.

The Avitene microfibrillar collagen hemostat (Davol, Cranston, RI) is an active collagen hemostat that accelerates clot formation by enhancing platelet aggregation and the release of fibrin. Similar to Floseal, it has no tissue sealing capability but is useful for counteracting parenchymal bleeding. EndoAvitene is available for use in endoscopic procedures. EndoAvitene comes prepared in a preloaded endoscopic delivery system developed to easily pass through standard trocars and cannulae. It is available in 5- and 10-mm diameters.

Cellulose

The most common cellulose-based hemostatic agent is regenerated oxidized cellulose that initiates clotting via contact activation. Oxidized cellulose has been shown to be poorly absorbed and may cause healing complications postoperatively.

Treatment of Donor Site and Suture

After bone harvesting, the topical use of an oxidized cellulose gauze is usually sufficient to control the bleeding; rarely, it is necessary to use the monopolar or bipolar coagulator. Filling the void left at the donor site with ancillary biomaterials and/or using membranes to promote bone regeneration is optional. The access wound is closed with a two-layer suture technique. The first layer is performed with an absorbable suture wire, which stabilizes the mental muscle to the periosteum; the second layer then closes the mucosal plane. The wire goes deep at the base of the flap, anchoring into muscle, and then returns higher to allow for fixation to the periosteum, or if for some reason this is difficult, the bone itself. The bone suture technique that we advocate is performed after drilling a couple of small holes in the thickness of cortical bone at the more cranial level of the osteotomy within, through which the wires pass (Rinaldi 2001). When tightening the knot, the adhesion of the mental muscles to the bone is immediately observable (Figs. 2.46 and 2.47). Compared to the periosteal suture, bone suture offers greater resistance, allowing support for the heaviest loads needed in this area. The chin wound is constantly stimulated by speaking and varied facial expressions and thus is rarely at rest. Using this technique may prevent the frequent complication of flap dehiscence. Some authors recommend a pressure bandage on the symphysis in the immediate postoperative period to control swelling (Figs. 2.48 to 2.50).

Generation of Insulin-producing Cells from Mouse and Human Embryonic Stem Cells

The earliest efforts to direct ESC differentiation were mostly done with murine ESCs. Different groups used elaborate multi-stage protocols, which resulted in the production of cells that had some β-cell characteristics, but fell short of being true fully-developed cells. The first work with hESCs provided evidence for some insulin production, but there was little characterization of the cells.

With this protocol, cells containing insulin, glucagon, somatostatin, and pancreatic polypeptide were produced. Importantly, the insulin content of these cells was far higher than had been achieved before. However, glucose-stimulated insulin secretion (GSIS) could not be demonstrated, indicating that the insulin-containing cells were immature. Other groups have also had success in directing hESCs towards β-cells.

The next step for Novocell was to make a few changes in the differentiation protocol and transplant the pancreatic precursor cells (Stage 4) into immunocompromised mice. After these cells are placed into an in vivo transplant site, some develop into fully mature functional β-cells. They contained all of the β-cell markers that were examined including MafA by electron microscopy; they contained characteristic β-cell granules with dense cores and halos; they efficiently converted proinsulin to insulin; and they had GSIS. In addition, they could normalize the glucose levels of streptozocin (STZ) diabetes. This experiment was made possible because STZ selectively kills mouse β-cells, but not the human β-cells in a graft site. The site of the grafts did not make much difference; subcutaneous, renal subcapsule, and epididymal fat pad sites were all successful. All of the other pancreatic endocrine cell types were found, but the grafts also contained many presumably immature cells. Importantly, of the 46 grafts examined by pathologists, one contained a teratoma, and six others had teratomatous elements. This raises important concerns about the safety of transplanting precursor cells into humans with diabetes. However, at this stage of the work, no effort was made to eliminate immature cells with teratoma formation potential. Certainly it will be a high priority to find ways to obtain a population of fully-mature cells in vitro, or to obtain a population of transplantable precursor cells that are far enough developed to not form teratomas.

SMALL ANIMAL STUDIES

These results clearly show that encapsulated mouse islet allografts can be readily implanted into diabetic NOD recipients without the use of any immunosuppression and achieve > 100 days of relatively normal mouse blood glucose levels. This means that both allograft immune reactivity and autoimmune reactivity are prevented from destroying the encapsulated islets by use of the PEG coating alone.

Uses

The alginate absorbable haemostatic dressings are non-toxic and non-irritant. They have advantages over oxidized cellulose, which include selective rate of absorption, sterilization (and resterilization) by autoclaving or dry heat and compatibility with antibiotics such as penicillin. They may be used internally in neurosurgery, endaural and dental surgery to be subsequently absorbed. Externally, they may be used (e.g. for burns or sites from which skin grafts have been taken) to arrest bleeding and form a protective dressing which may be left or later removed in a manner appropriate to the type of dressing employed (see above). Protective films of calcium alginate may also be used by painting the injured surface with sodium alginate solution and then spraying it with calcium chloride solution.

Calcium alginate wool as a swab for pathological work or bacterial examination of such things as food processing equipment and tableware has the great advantage over cotton wool in that it permits release of all the organisms by disintegration and solution of the swab in, for example, Ringer's solution containing sodium hexametaphosphate.

In fabrics the calcium alginate fibres would disintegrate in alkaline solutions (laundering), but this advantage is turned to a commercial virtue by the use of the yarn as a scaffolding thread to support yarns normally too fine to survive the weaving process. The scaffold is removed by an alkaline bath to leave a lightweight fabric.