Carboxymethyl chitosan

In general these derivatives are safe, their chemical functions being the glycine moiety the same holds for AT,0-carboxymethyl chitosan, as demonstrated for instance by studies intended to assess the efficacy of W,0-carboxymethyl chitosan to limit adhesion formation in a rabbit abdominal surgery model. The inability of fibroblasts to adhere to N,0-carboxymethyl chitosan-coated surfaces suggests that it may act as a biophysical barrier [135]. 

Microspheres were prepared from carboxymethyl chitosan and alginate by emulsion phase separation. The encapsulated bovine serum albumin was... 

Co-administration of ofloxacin and chitosan in eyedrops increased the bioavailabUity of the antibiotic [290]. Trimethyl chitosan was more effective because of its solubility (plain chitosan precipitates at the pH of the tear fluid). On the other hand, N-carboxymethyl chitosan did not enhance the corneal permeability nevertheless it mediated zero-order ofloxacin absorption, leading to a time-constant effective antibiotic concentration [291]. Also W,0-carboxymethyl chitosan is suitable as an excipient in ophthalmic formulations to improve the retention and the bioavailability of drugs such as pilocarpine, timolol maleate, neomycin sulfate, and ephedrine. Most of the drugs are sensitive to pH, and the composition should have an acidic pH, to enhance stability of the drug. The delivery should be made through an anion exchange resin that adjusts the pH at around 7 [292]. Chitosan solutions do not lend themselves to thermal sterilization. A chitosan suspension, however. 

Cancer-risk-diet relationship, 262 Canonical correlation analysis, 104 Capsaicin, 15-16 N-(Carboxymethyl)chitosan, preservation of meat flavor, 73 Carrageenan, fat replacement in ground beef, 73-75 Carry-over, description, 57 Carry-through, description, 57 Carvone, headspace analysis, 24,25/ L-Carvone, chemicals resulting in anosmias, 211... 

For other polysaccharides such as chitosan a high antimicrobial activity has been described - mainly against Escherichia coli and Staphylococcus aureus [153,154]. This activity of chitosan is the basis for the development of materials for wound healing, e.g., in combination with N,0-(carboxymethyl)chitosan and collagen [155]. 

A usual approach to increase chitosan s solubility at neutral pH values is the substitution of the primary amine. Whereas N-substitution with alkyl groups (i.e. -CH3 groups) can increase the aqueous solubility without affecting its cationic character, substitution with moieties bearing carboxyl groups can yield polymers with polyampholytic properties (Muzzarelli et al. 1982). Mono-carboxymethylated chitosan (MCC) was synthesized and further... 

Muzzarelli, R.A.A., Tanfani, F., Emmanueli, S. and Mariotti, S. (1982) V-(carboxymethyli-dene)-chitosans and V-(carboxymethyl)-chitosans novel chelating polyampholytes obtained from chitosan glyoxylate. Carbohydr. Res. 107 199-214. 

Thanou, M., Nihot, M.T., Jansen, M., Verhoef, J.C. and Junginger, H.E. (2001d) Mono— A-carboxymethyl chitosan (MCC), a polyampholytic chitosan derivative, enhances the intestinal absorption of low molecular weight heparin across intestinal epithelia in vitro and in vivo. J. Pharm. Sci. 90 38-46. 

Various chitosan derivatives of enhanced solubility, mucoadhesive, and permeation properties were developed. V-Trimethyl chitosan chloride (TMC) is a quater-nized derivative of chitosan with superior aqueous solubility over a broader pH range and penetration-enhancing properties under physiological conditions [78]. Carboxymethylated chitosan (CMChi) is a polyampholytic polymer able to form viscoelastic gels in aqueous environments. CMChi appears to be less potent compared with the quaternized derivative. Neither TMC nor CMChi have been found to provoke damage of the cell membrane, and therefore, they should not alter the viability of nasal epithelial cells [79],... 

A comparative study of chitin obtained from lobsters, starch, and carboxymethyl chitosan as disintegrating agents was conducted. The influence of the method in the preparation of tablets on the disintegrating activity of both polymers was evaluated. Chitin proved to have good characteristics as a disintegrating agent independently... 

The advantage of complex coacervates is that high payloads can be obtained. Chitosan/alginate coacervates have been reported to encapsulate up to 87% shark liver oil, which is rich in omega-3 fatty acids (Peniche et al. 2004). Microspheres of carboxymethyl chitosan/alginate hardened with calcium chloride have been used for encapsulation of up to 80% bovine serum albumin (Zhang et al. 2004). 

Figure 3 is the result of pulse radiolysis experiment about the reaction of hydrated electron with polymer chains(0 or 30 mM carboxymethyl chitosan solution with 0.3 M terf-butanol under Ar saturation), and shows the decay of the absorbance as a function of time. This absorbance was measured at wavelength 720 nm, which is the absorption peak of hydrated electron. As seen in Figure 3, the absorbance increases immediately after the irradiation, and attenuates afterwards. This means that hydrated electron is generated immediately after irradiation and diminishes gradually by some reactions of hydrated electron. Compared the absorbance decay of polymer solution with the decay of solution without polymer, the decay of polymer solution is faster than without polymer, so it is obvious that hydrated electron reacts with polymer chains. The decay curve can be fitted by pseudo first-order decay. The pseudo first-order decay is shown by equation (8). From estimating the slope of the pseudo first-order decay rate of the absorbance at 720 nm against polymer concentration, the rate constant of the reaction of hydrated electron with polymer chains can be calculated Figure 4). The rate constants of the reaction of hydrated electron with CM-chitin and CM-chitosan was determined as l.lxlO7 and MxlO M V1]. These values are almost the same with the value of carboxymethyl cellulose(2< ).

Figure 5 shows time profile of absorabance at 472 nm by pulse radiolysis (0 or 30mM carboxymethyl chitosan solution with 2 mM KSCN under N20 saturation). As seen in Figure 5, the absorbance without polymer is obviously lower than a polymer solution. So, it was confirmed that OH radical reacts with polymer chains. Figure 6 shows the relation between the change of the... 

Cuero, R.G., Osuji, G., and Washington, A. 1991. ZV-Carboxymethyl chitosan inhibition of aflatoxin production Role of zinc. Biotechnol. Lett. 13, 441-444. 

Another approach to improve the properties of chitosan hydrogels is via the preparation of polymer composites. Porous hydrogels of N-carboxymethyl chitosan/polyvinyl alcohol were prepared by Lee et al. [99]. Hydroxypropyl chitosan was combined with sodium alginate for the formation of biodegradable hydrogels [100]. Chitosan-hyaluronic acid composite was prepared by Tan et al. [101]. 

Chitosan derivatives have also been studied for possible utilization in wound dressings. For example, three kinds of chitosan derivative (oligochitosan, N,0-carboxymethyl-chitosan, and Al-carboxymethyl-chitosan) are used to form sheets and pastes, all of which exhibit appropriate cytocompatibility to the fibroblasts isolated from normal human dermis and hypertrophic scars [179]. 

Tavakol M et al (2009) Sulfasalazine release from alginate-N, O-carboxymethyl chitosan gel beads coated by chitosan. Carbohydr Polym 77 326-330... 

Chen XG, Wang Z, Liu WS, Park HJ. The effect of carboxymethyl-chitosan on proliferation and collagen secretion of normal and keloid skin fibroblasts. Biomaterials 2002 23 4609-4614. 

Kim KW, Thomas RL, Lee C, Park HJ. Antimicrobial activity of native chitosan, degraded chitosan, and O-carboxymethylated chitosan. J Food Prot 2003 66 1495-1498. 

Zonghua, L., Yanpeng, J., and Ziyong, Z. Calcium-carboxymethyl chitosan hydrogel beads for protein drug delivery system. J. Appl. Polym. Sci. 103 (2007) 3164-3168. 

Liu, X., Yang, F., Song, T., Zeng, A., Wang, Q., Sun, Z., and Shen, J. Effects of chitosan, 0-carboxymethyl chitosan and V-[(2-hydroxy-3-V,V-dimethylhexadecyl ammonium) propyl] chitosan chloride on lipid metabolism enzymes and low-densitylipoprotein receptor in a murine diet-induced obesity. Carbohydr. Polym. 85 (2011) 334-340. 

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