Brian D. Condon

Segal crystallinity index revisited by the simulation of X-ray diffraction patterns of cotton cellulose Iβ and cellulose II

The Segal method estimates the amorphous fraction of cellulose Iβ materials simply based on intensity at 18° 2θ in an X-ray diffraction pattern and was extended to cellulose II using 16° 2θ intensity. To address the dependency of Segal amorphous intensity on crystal size, cellulose polymorph, and the degree of polymorphic conversion, we simulated the diffraction patterns of cotton celluloses (Iβ and II) and compared the simulated amorphous fractions with the Segal values. The diffraction patterns of control and mercerized cottons, respectively, were simulated with perfect crystals of cellulose Iβ (1.54° FWHM) and cellulose II (2.30° FWHM) as well as 10% and 35% amorphous celluloses. Their Segal amorphous fractions were 15% and 31%, respectively. The higher Segal amorphous fraction for control cotton was attributed to the peak overlap. Although the amorphous fraction was set in the simulation, the peak overlap induced by the increase of FWHM further enhanced the Segal amorphous intensity of cellulose Iβ. For cellulose II, the effect of peak overlap was smaller; however the lower reflection of the amorphous cellulose scattering in its Segal amorphous location resulted in smaller Segal amorphous fractions. Despite this underestimation, the relatively good agreement of the Segal method with the simulation for mercerized cotton was attributed to the incomplete conversion to cellulose II. The (1-10) and (110) peaks of cellulose Iβ remained near the Segal amorphous location of cellulose II for blends of control and mercerized cotton fibers.

Peptide conjugated cellulose nanocrystals with sensitive human neutrophil elastase sensor activity

In chronic wounds, elevated human neutrophil elastase (HNE) is a destructive protease that has been proposed as a biomarker. Numerous wound dressing designs have been introduced in an effort to lower HNE levels. The clinical detection of HNE as a point of care biomarker or an in situ colorimetric adjuvant to chronic wound dressings presents potential advantages in the management of chronic wounds. A colorimetric approach to the detection of HNE using peptide conjugated cotton cellulose nanocrystals (CCN) is reported here. For this purpose a HNE tripeptide substrate, n-Succinyl-Alanine–Alanine-Valine-para-nitroanilide (Suc-Ala–Ala-Val-pNA), was covalently attached to glycine esterified CCN and compared with a similar tetrapeptide analog for colorimetric HNE sensor activity. Visible HNE activity was significantly higher on CCN tripeptide conjugates when compared with similar analogs synthesized on paper. Upon enzymatic release of para-nitroaniline (pNA) from the Glycine-CCN conjugate of succinyl-Ala–Ala-Val-pNA, amplification of the colorimetric response from pNA with reactive dyes enhanced visible absorption of the chromogen. Two color amplifying dyes that react with pNA were compared for their ability to enhance the visual sensor response to HNE activity. The colorimetric detection of HNE with CCN tripeptide conjugates was sensitive at HNE levels previously reported in chronic wound fluid (0.05xa0U/mL HNE). The HNE sensor and the chromogen amplifying dyes were interfaced with 50 and 10xa0kD dialysis cellulose membranes (DCM) to model filtration of HNE and chromogen (pNA) from a model wound dressing surface before and after sensor reactivity. The detection sensitivity to HNE activity was assessed with the CCN-tripeptide conjugate interfaced at the DCM surface distal and proximal to a dressing surface. The HNE sensor interfaced proximal to the dressing surface was most efficient with 10xa0kD membrane filtration of pNA and subsequent reaction with amplifying dyes. When interfaced with the 10xa0kD cellulose membrane, elastase sensor activity remained sensitive to 0.05xa0U/mL HNE. The nanocellulose surface properties, performance and design issues of the biosensor approach are discussed.

Immobilization of lysozyme-cellulose amide-linked conjugates on cellulose I and II cotton nanocrystalline preparations

Lysozyme was attached through an amide linkage between some of the protein’s aspartate and glutamate residues to amino-glycine-cellulose, which was prepared by esterification of glycine to preparations of cotton nanocrystals. The nanocrystalline preparations were produced through acid hydrolysis and mechanical breakage of the cotton fibers from a scoured and bleached cotton fabric and a scoured and bleached, mercerized fabric, which was shown to produce cellulose I (NCI) and cellulose II (NCII) crystals respectively. A carbodiimide-activation coupling reaction was used to create the lysozyme-amino-glycine-cellulose conjugates using both NCI and NCII in a polar solvent and gave yields of covalently linked lysozyme at 604xa0mg/gram of cotton nanocrystal. The incorporation of lysozyme conjugated to the NCI and NCII preparations gave very high activity (1,500xa0U/mg cotton) when assessed using a fluorescence tag assay to measure antimicrobial activity against Micrococcus lysodeikticus. Scanning electron micrographs demonstrated an aggregation of nanoparticles corresponding to lysozyme bound on the surface of larger cotton nanocrystalline sheets. The approach of producing high enzyme activity on cotton nanocrystals is discussed in the context of selectively presenting robust hydrolase activity on nanocrystalline surfaces.

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.

High resistance to thermal decomposition in brown cotton is linked to tannins and sodium content

Brown cotton fibers (SA-1 and MC-BL) studied were inferior to a white cotton fiber (Sure-Grow 747) in fiber quality, i.e., a shorter length, fewer twists, and lower crystallinity, but showed superior thermal resistance in thermogravimetric, differential thermogravimetric, and microscale combustion calorimetric (MCC) analyses. Brown cotton fibers yielded 11–23xa0% smaller total heat release and 20–40xa0% greater char. Washing fibers in water and a 1xa0% NaOH solution showed that rich natural inorganic components and the condensed tannins present in brown cotton are responsible for the unusual thermal property. The loss of inorganics from white cotton during a water wash increased the thermal decomposition temperature of cellulose, resulting in no char yield. However, the stronger binding of metal ions for brown cotton as well as its dominant adsorption of sodium ions after a 1xa0% NaOH wash facilitated the low-temperature thermal-reaction route; the sodium content showed a significant negative correlation with the heat release capacity of the fiber. Condensed tannins greatly enhanced the adsorption of sodium ions to the fiber and exhibited inherent thermal stability. The limiting oxygen indices (LOI) calculated from the MCC parameters indicated the slower burning characteristic of brown cotton, and its LOI was further increased upon adsorption of sodium ions.

Effect of polyester blends in hydroentangled raw and bleached cotton nonwoven fabrics on the adsorption of alkyl-dimethyl-benzyl-ammonium chloride

The adsorption kinetics and isotherms of alkyl-dimethyl-benzyl-ammonium chloride (ADBAC), a cationic surfactant commonly employed as an antimicrobial agent, on hydroentangled nonwoven fabrics (applicable for wipes) including raw cotton, bleached cotton, and their blends with polyester (PES) were studied at room temperature. The adsorption kinetics of ADBAC on all nonwoven fabrics was best described by the pseudo-first-order kinetic model. Unlike bleached cotton/PES blends, the equilibrium adsorption capacities of ADBAC on raw cotton/PES blends were enhanced in comparison with predictions based on the binary mixing rule. The adsorption rates for raw cotton, determined by the KASRA (kinetics of adsorption study in the regions with constant adsorption acceleration) model and Elovich equation, were significantly greater than those for bleached cotton, resulting in a rapid decrease of adsorption rates when blending with PES, which has a negligible interaction with ADBAC. This distinctive adsorption property of raw cotton was attributed to its unique surface characteristics induced by the hydroentangling process: retained pectin, partial removal of waxes, and surface fibrillation, which enhance electrostatic interaction, hydrophobic interaction, and accessible surface area to ADBAC, respectively. In adsorption isotherms, raw cotton/PES blends exhibited a non-linear decrease in maximum adsorption capacity and monolayer adsorption capacity, calculated by the Langmuir and Langmuir-type equations, respectively, as a function of PES blend ratio.

Comparison of biodegradation of low-weight hydroentangled raw cotton nonwoven fabric and that of commonly used disposable nonwoven fabrics in aerobic Captina silt loam soil

The increasing use of synthetic disposable nonwoven products generates a large amount of non-biodegradable solid waste. In an effort to enhance the use of raw cotton in nonwoven wipes applications, this study compares the biodegradation of low-weight nonwoven fabrics (around 50u2009g/m2) made of mechanically pre-cleaned raw cotton, rayon, polypropylene (PP), and polylactic acid (PLA) in a Captina silt loam soil. The biodegradation rates of raw cotton and rayon fabrics were fitted to the first-order kinetics model with half-life values of 12.6 and 7.6 days, respectively. The slightly faster disintegration of cellulose structure for rayon was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectra, and distinct morphological changes in the fiber (cracks and breakage were prevalent in raw cotton, whereas the thinning and merging of fibers occurred in rayon) were observed during their biodegradation. PLA and PP nonwoven fabrics exhibited no weight loss during the burial periods studied, but showed some evidence of oxidation in ATR-FTIR spectra. The breaking and burst strengths of PLA fabric decreased by 45% and 23% of the original strengths, respectively, while neither significantly decreased in PP fabric. The results suggest that mixing raw cotton or rayon low-weight nonwoven wastes with surface soil provides an alternative disposal method, but this land application could not be recommended for PLA and PP nonwoven wastes.

The GhTT2_A07 gene is linked to the brown colour and natural flame retardancy phenotypes of Lc1 cotton ( Gossypium hirsutum L.) fibres

Highlight The brown fibre cotton Lc1 locus is linked to a 1.4Mb genomic inversion that activates GhTT2_A07. This mutation upregulates flavonoid biosynthesis and confers natural flame retardancy.

Electrokinetic analysis of hydroentangled greige cotton–synthetic fiber blends for absorbent technologies

Through nonwoven hydroentanglement of greige cotton blends with polyester and nylon, varying degrees of fiber surface polarity, swelling, and absorbance can be achieved. Electrokinetic properties of nonwoven blends made with Ultra Clean™ cotton (100% greige or virgin cotton) and polyester or nylon in 40:60 and 60:40 ratios demonstrated distinct differences in charge, swell, and per-cent moisture uptake capability. An electrochemical double layer analysis of charge based on a pH titration (pH 1.5–11 in 1u2009mM KCl) was employed to measure the relative fiber and fabric surface polarity (ζplateau), which ranged from −60 to −26 millivolts. A linear relationship of fiber swelling (Δζ) and per cent moisture content is apparent when greige cotton and synthetic fibers are blended. Water contact angles revealed that the cotton/synthetic fiber blends were hydrophobic (contact angle >80°) while retaining significant absorbency. The greige cotton/synthetic nonwoven materials, however, possess absorbent properties characterized by varying degrees of moisture uptake, fiber polarity, and swelling attributes similar to absorbent fluid transport materials present in the layers of incontinence products. Electrokinetic properties of the blended greige cotton/synthetic nonwovens are correlated to absorbent incontinence materials.

The adsorption of alkyl-dimethyl-benzyl-ammonium chloride onto cotton nonwoven hydroentangled substrates at the solid–liquid interface is minimized by additive chemistries

Quaternary ammonium compounds, commonly referred to as quats, are cationic surfactants widely used as the active biocidal ingredient for disposable disinfecting wipes. The cationic nature of quats results in a strong ionic interaction and adsorption onto wipes materials that have an anionic surface charge, such as cellulosic materials, including cotton. The degree of adsorption of quats onto cotton nonwovens is affected by pretreatment of the substrate, more specifically whether it is a greige or a scoured and bleached fabric. This study examined the effect of varying the chemical and physical properties of solutions on the adsorption of the quat alkyl-dimethyl-benzyl-ammonium chloride (ADBAC) onto greige and scoured and bleached cotton nonwoven fabrics produced by hydroentanglement. At a constant surfactant concentration, the liquor ratio, pH, temperature, and concentrations of various electrolytes in the solution were varied and the amount of ADBAC depleted from solution was determined over time. The results suggested that a more alkaline solution increased the amount of ADBAC adsorbed onto both cotton nonwoven fabrics, while a more acidic solution reduced ADBAC adsorption. Likewise, increasing the temperature and concentration of salts in the solution reduced the adsorption of ADBAC onto the cotton fabrics. The presence of nonionic surfactants or low molecular weight quats also reduced ADBAC adsorption onto cotton fabrics in a concentration-dependent manner. The results of this study will provide guidance for optimized chemical formulations compatible with disposable disinfecting cotton-based wipes, cloths, and other cotton-containing implements intended for use in cleaning and disinfecting applications.