J. Vincent Edwards

Cotton Fiber Chemistry and Technology

Cotton fiber chemistry and technology , Cotton fiber chemistry and technology , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Modified cotton gauze dressings that selectively absorb neutrophil elastase activity in solution

Dressings for chronic human wounds have been aimed at protection, removal of exudate, and improved appearance. However since the time of ancient Greece wound care and dressing strategies have primarily relied on empiricism. Recent studies have shown that chronic wounds contain high levels of tissue and cytokine destroying proteases including collagenase and neutrophil elastase. Therefore we sought to develop an effective wound dressing that could absorb elastase through affinity sequestration. Cotton gauze was modified by oxidation, phosphorylation, and sulfonation to enhance elastase affinity by ionic or active site uptake. Type VII absorbent cotton gauze was oxidized to dialdehyde cotton which was subsequently converted in part to the bisulfite addition product. Gauze preparations were also phosphorylated and carboxymethylated. Modified cotton gauzes were compared with untreated gauze for reduction of elastase activity in buffered saline. Solutions of elastase that were soaked in oxidized, sulfonated, and phosphorylated cotton gauze showed reduced elastase activity. The initial velocities (vo) and turnover rates of elastase showed significant decreases compared with solutions taken from untreated gauze. The reduction in enzyme activity with dialdehyde cotton gauze was confirmed in solution by determining elastase inhibition with dialdehyde starch. The dialdehyde cotton gauze also decreased elastase activity in human wound fluid in a dose response relation based on weight of gauze per volume of wound fluid. Absorbency, pH, air permeability and strength properties of the modified gauze were also compared with untreated cotton gauze. This report shows the effect of reducing elastase activity in solution with cotton containing aldehydic or negatively charged cellulose fibers that may be applicable to treatment modalities in chronic wounds.

Modified Fibers with Medical and Specialty Applications

The research and development of chronic wound dressings, which possess a mechanismbased mode of action, has entered a new level of understanding in recent years based on improved definition of the biochemical events associated with pathogenesis of the chronic wound. Recently, the molecular modes of action have been investigated for skin substitutes, interactive biomaterials, and some traditional material designs as balancing the biochemical events of inflammation in the chronic wound to improve healing. The interactive wound dressings have activities including up-regulation of growth factors and cytokines and down-regulation of destructive proteolysis. Carbohydrate-based wound dressings have received increased attention for their molecular interactive properties with chronic and burn wounds. Traditionally, the use of carbohydrate-based wound dressings including cotton, xerogels, charcoal cloth, alginates, chitosan, and hydrogels have afforded properties such as absorbency, ease of application and removal, bacterial protection, fluid balance, occlusion, and elasticity. Recent efforts in our lab have been underway to design carbohydrate dressings that are interactive cotton dressings as an approach to regulating destructive proteolysis in the non-healing wound. Elastase is a serine protease that has been associated with a variety of inflammatory diseases and has been implicated as a destructive protease that impedes wound healing. The presence of elevated levels of elastase in non-healing wounds has been associated with the degradation of important growth factors and fibronectin necessary for wound healing. Focus will be given to the design, preparation, and assessment of a type of cotton-based interactive wound dressing designed to intervene in the pathophysiology of the chronic wound through protease sequestration.

Inhibition of elastase by a synthetic cotton-bound serine protease inhibitor: in vitro kinetics and inhibitor release

A cotton‐bound serine protease inhibitor of elastase (fiber‐inhibitor) has been formulated for in vitro evaluation in chronic wound fluid. As a model to understand the properties of the inhibitor in wound dressings, the kinetic profile and in vitro release of the fiber‐inhibitor formulation have been examined. The elastase inhibitor N‐Methoxysuccinyl‐Ala‐Ala‐Pro‐Val‐chloromethylketone was modified onto cotton cellulose fibers and assayed as a colloidal system. Amino acid analysis and reversed phase high performance liquid chromatography were compared as semiquantitative methods to assess elastase inhibitor release from the cotton fibers. The kinetics of inhibition was assessed on treated fibers of synthetic dressings such that a colloidal suspension of the fiber‐inhibitor and elastase was employed as an assay. A dose–response relationship was observed in the kinetics of substrate hydrolysis catalyzed by three elastases: porcine pancreatic elastase, which was employed to model this approach; human leukocyte elastase; and elastase in human chronic wound fluid. Both freely dissolved and fiber‐bound inhibitors were studied. The initial rates of substrate hydrolysis were inversely linear with freely dissolved inhibitor dose. The apparent first order rate constants, kobs, for the elastase‐inhibitor complex were calculated from the kinetic profiles. The kobs for inhibitor bound enzyme varied as a function of inhibitor vs. enzyme concentration and based on the order of mixing of substrate, inhibitor and enzyme in the assay. Enzyme inhibition by the fiber‐inhibitor was measured as inhibitor concentration at 50% inhibition (I50). I50 values measured from the colloidal assay with fiber‐released inhibitor were within the same range to those for freely dissolved inhibitor. Inhibition of elastase activity in chronic wound fluid was observed with 1–5 mg of fiber‐inhibitor formulation. This approach constitutes an in vitro assessment of synthetic serine protease inhibitors on fibers and may be employed to evaluate structure vs. function of elastase inhibition in the modified fibers of wound dressing composites.

Future Structure and Properties of Mechanism-Based Wound Dressings

The research and development of chronic wound dressings, which possess a mechanism-based mode of action, has entered a new level of understanding in recent years based on improved definition of the biochemical events associated with pathogenesis of the chronic wound. Recently, the molecular modes of action have been investigated for skin substitutes, interactive biomaterials, and some traditional material designs as balancing the biochemical events of inflammation in the chronic wound to improve healing. The interactive wound dressings have activities including up-regulation of growth factors and cytokines and down-regulation of destructive proteolysis. Carbohydrate-based wound dressings have received increased attention for their molecular interactive properties with chronic and burn wounds. Traditionally, the use of carbohydrate-based wound dressings including cotton, xerogels, charcoal cloth, alginates, chitosan, and hydrogels have afforded properties such as absorbency, ease of application and removal, bacterial protection, fluid balance, occlusion, and elasticity. Recent efforts in our lab have been underway to design carbohydrate dressings that are interactive cotton dressings as an approach to regulating destructive proteolysis in the non-healing wound. Elastase is a serine protease that has been associated with a variety of inflammatory diseases and has been implicated as a destructive protease that impedes wound healing. The presence of elevated levels of elastase in non-healing wounds has been associated with the degradation of important growth factors and fibronectin necessary for wound healing. Focus will be given to the design, preparation, and assessment of a type of cotton-based interactive wound dressing designed to intervene in the pathophysiology of the chronic wound through protease sequestration.

Kinetic and structural analysis of fluorescent peptides on cotton cellulose nanocrystals as elastase sensors

Human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) are serine proteases with destructive proteolytic activity. Because of this activity, there is considerable interest in elastase sensors. Herein we report the synthesis, characterization, and kinetic profiles of tri- and tetrapeptide substrates of elastase as glycine-esterified fluorescent analogs of cotton cellulose nanocrystals (CCN). The degree of substitution of peptide incorporated in CCN was 3-4 peptides per 100 anhydroglucose units. Glycine and peptide-cellulose-nanocrystals revealed crystallinity indices of 79 and 76%, respectively, and a crystallite size of 58.5 Å. A crystallite model of the peptide-cellulose conjugate is shown. The tripeptide conjugate of CCN demonstrated five-fold greater efficiency in HNE than the tripeptide in solution judged by its kcat/Km of 33,515. The sensor limits of detection at 2mg of the tri- and tetrapeptide CCN conjugates over a 10 min reaction time course were 0.03 U/mL PPE and 0.05 U/mL HNE, respectively.

Performance of Bioactive Molecules on Cotton and Other Textiles

Four types of biologically active molecules were examined for their structure/activity relationships as applied to textile functionalization. Bio-molecules including enzymes, peptides, carbohydrates, and lipids have been found to retain their activity when linked to cotton fabrics. Wound dressing protection against the protease destruction caused by human neutrophil elastase was examined with cellulose conjugates and formulations of peptides, carbohydrates, and lipids attached with various chemistries to cotton dressings. These serve as a model for protective textiles at the surface of the skin. Additional biological activities that were explored included antibacterial and haemostatic fabrics related to wound healing, and neurotoxin neutralization related to decontamination. Lysozyme was found to have robust antibacterial activity when conjugated to cotton. Peptide conjugates of cellulose have been explored as enzyme substrates, antimicrobial agents, and cell adhesion promoters on textiles for wound healing. Carbohydrates ranging from low molecular weight monosaccharides to high molecular weight polysaccharides have both molecular and functional activity when crosslinked or grafted onto cotton with numerous textile performance properties. Textile bound lipids have been explored for a variety of applications including antibacterial, hygienic function, and enzyme inhibition. A lipid: albumin complex that serves as a carrier transfer agent involved in enzyme inhibition is given as an example.

Development of a Continuous Finishing Chemistry Process for Manufacture of a Phosphorylated Cotton Chronic Wound Dressing

A phosphorylated form of cotton gauze for treatment of chronic wounds was designed to improve the wound dressings capacity to remove harmful proteases from the wound and facilitate healing. Development of the fabric finishing chemistry of the wound dressing with a process suitable for textile mill production required adapting the stationary finishing chemistry of the cotton phosphorylation from a batch-type pad-dry-cure finishing treatment to a continuous pilot scale finishing process. Issues in optimizing the cotton finishing process took into consideration dressing sterilization, the effect of city water versus de-ionized water, retention of the fabric whiteness index and protease sequestration capacity of the dressing, which is the index of the dressings efficacy. Three types of sterilization approaches were assessed, including gamma ray, ethylene oxide and steam sterilization to determine the effect of sterilization on the phosphorylated cotton dressing and the subsequent efficacy of the sterilized dressing to remove proteases from the wound. Two phosphorylation reagents were compared for their ability to phosphorylate cotton in a urea-based formulation and yield an active, effective dressing, with a high whiteness index. Phosphorylation with a diammonium phosphate (DAP) : urea formulation generally gave a more effective dressing as an active protease sequestrant, and phosphorylation with sodium hexametaphosphate (SMP) : urea gave a higher whiteness index. Finishing formulations combining the two phosphorylating reagents, DAP and SMP: urea, were assessed to improve both whiteness and efficacy. However, sterilization of DAP treated cotton with ethylene oxide eradicated activity through apparent masking of the cellulose phosphate hydroxyls. Side reactions that may occur during ethylene oxide treatment were discussed as the possible origin of the phosphate hydroxyl masking. On the other hand, sterilization with gamma irradiation produced significant yellowing of the dressing. A SMP : urea (16 : 30) formulation was employed in the continuous process finishing treatment, and found to be most optimal for whiteness, efficacy and ease of sterilization, when adapted to industrial scale production of the cotton chronic wound dressing.

Electrokinetic properties of functional layers in absorbent incontinence nonwoven products

Incontinence control through the use of well designed nonwoven materials is a rapidly growing area of interest. Analysis of the streaming zeta potential, absorbance capacity and moisture content measurements of absorbent layers in incontinence materials is a useful approach to evaluation and design. Using this approach, electrokinetic properties can be used to demonstrate the role of fiber surface polarity, swelling, and water uptake in the mechanism of incontinence control. By applying electrochemical double layer analysis to functional layers of absorbent incontinence products, the polar charge differences between cover stock, the acquisition/distribution layer (ADL) and the absorbent core were characterized. The aqueous fiber polarity is characterized from pH titration plots that give zeta plateau (ζplateau) values for each absorbent layer. The ζplateau value assigns the relative hydrophilic/hydrophobic (amphiphilic) character of the cover stock and ADL. Delta zeta (Δζ) and moisture content are applied to determine the functional value of fluid acquisition due to swelling and moisture absorption. Structure/function mechanisms are proposed for urine uptake relative to volume, pH and fluid transport in the cover stock and ADL of heavy, moderate, light incontinence pads and adult incontinence underwear. Using an electrokinetic analysis as a model to describe the mechanism of urine transport in absorbent incontinence materials makes possible the distinction of absorbent material design differences based on fiber charge, swelling, and absorption capacity. The electrokinetic model approach to absorbent incontinence material analysis and design is discussed for its potential applications.

Chromatographic and Traditional Albumin Isotherms on Cellulose: A Model for Wound Protein Adsorption on Modified Cotton

Albumin is the most abundant protein found in healing wounds. Traditional and chromatographic protein isotherms of albumin binding on modified cotton fibers are useful in understanding albumin binding to cellulose wound dressings. An important consideration in the design of cellulosic wound dressings is adsorption and accumulation of proteins like albumin at the solid–liquid interface of the biological fluid and wound dressing fiber. To better understand the effect of fiber charge and molecular modifications in cellulose-containing fibers on the binding of serum albumin as observed in protease sequestrant dressings, albumin binding to modified cotton fibers was compared with traditional and chromatographic isotherms. Modified cotton including carboxymethylated, citrate-crosslinked, dialdehyde and phosphorylated cotton, which sequester elastase and collagenase, were compared for their albumin binding isotherms. Albumin isotherms on citrate-cellulose, cross-linked cotton demonstrated a two-fold increased binding affinity over untreated cotton. A comparison of albumin binding between traditional, solution isotherms and chromatographic isotherms on modified cellulose yielded similar equilibrium constants. Application of the binding affinity of albumin obtained in the in vitro protein isotherm to the in vivo wound dressing uptake of the protein is discussed. The chromatographic approach to assessment of albumin isotherms on modified cellulose offers a more rapid approach to evaluating protein binding on modified cellulose over traditional solution approaches.