Fibers ultra-fine cellulose

Son, W.K., Youk, J.H., Lee, T.S. and Park, W.H. 2004a. Preparation of antimicrobial ultra-fine cellulose acetate fibers with silver nanoparticles. Macromol. Ravid Commun. 25 1632-1637. 

Two examples from the second approach are presented here. Both add covalently bonded polymeric chains to ultra-fine cellulose fiber surfaces. One tethers enzyme from the surface by amphiphilic linear PEG spacers that carry reactive end groups to form covalent bonds with enzyme proteins. The other adds polyelectrolyte PAA grafts that are sufficiently polar to attract enzymes via secondary forces. Both surface polymer chains are compatible with aqueous and organic media. 

Poly(acrylic acid) (PAA) was grafted onto the ultra-fine cellulose fiber surfaces via ceric ion initiation (Scheme 5). The carboxylic acid concentration could be controlled by varying monomer AA and/or ceric ion concentrations, and was determined by NaOH-HCl titration using phenophthlein as the indicator. Unless otherwise indicated, fibers with 3.6 mmol of COOH per g cellulose (lAA]/[Ce(IV)]-30) were used for enzyme adsorption and assay. The PAA activated cellulose fibers were immersed in 1.0 mg/ml lipase solution (pH 7.0) at room temperature for 24 hrs. The lipase adsorbed cellulose fibers were rinsed by pH 7 buffer and deionized water to remove loose lipase, then dried under vacuum at room temperature for 12 hrs. 

PEG-diacylchloride (COCl-PEG-COCl) was attached to ultra-fine cellulose fiber surfaces via ester bond formation between the COCl of the PEG-diacylchloride and the OH on the cellulose (Scheme 6). The quantities of COCl or COOH could be optimized by varying the COCl/OH molar ratio and PEG chain length. Based on the quantification of COOH by the silver o-nitrophenolate method (27), the PEG attached cellulose fibers contained up to 1.0 mmol of COOH per g of cellulose unless specified otherwise. Lipase was covalently bound with the PEG-attached cellulose fibers in pH 4 buffer in the presence of a carbodiimide (EDC) coupling agent and incubated for 7 hrs. Lipase bound fibers were then rinsed in buffers of increasing pH of 4, 7, and 10, then dried under vacuum at ambient temperature for 12 hrs. 

Two proaches have been reported to immobilize enzyme on ultra-fine cellulose fibers, i.e., adsorption and covalent binding. Both approaches improved the protein binding ability of fiber surfaces by adding chemical functionalities via covalently bonded polymeric chains to ultra-fine cellulose fiber surfaces. Adsorption of enzyme proteins on fiber surfaces was accomplished by ceric ion-initiated graft polymerization of electrolyte acrylic acid monomer and the subsequent enzyme adsorption via secondary forces. 

Son, W. K., J. H. Youk, T. S. Lee, and W. H. Park (2004a). Electrospinning of ultra-fine cellulose acetate fibers studies of a new solvent system and deacetylation of ultrafine cellulose acetate fibers. Journal of Polymer Science Part B Polymer... 

Wang, Y. H. and Y. L. Hsieh (2004). Enzyme immobilization to ultra-fine cellulose fibers via amphiphilic polyethylene glycol spacers. Journal of Polymer Science Part A Polymer Chemistry 42(17) 4289-4299. 

Microbial cellulose derived from Acetobacter xylinum by fermentation process has been established to be a remarkably versatile biomaterial and can be used in wide variety of applied scientific endeavours, especially for medical devices. Due to its ultra-fine network architecture, high degree of crystallinity, hydrophilicity and moldability, microbial cellulose is a natural candidate for numerous medical and tissue-engineered apphcations. The use of direct nanomechanical measurement determined that these fibers are very strong, and when used in combination with other biocompatible materials, produce nanocomposites particularly suitable for use in human and veterinary... 

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