Chitosan solutions

However, it is not mandatory to prepare an emulsion in fact. Pan et al. [99] reported the identification of the formation conditions of the chitosan-tripolyphosphate nanoparticles, in terms of concentrations of chitosan and tripolyphosphate. They simply used a chitosan solution at pH 4 (4 ml, con-... 

When the films were treated in either an oxygen plasma environment or under UV/ozone irradiation, the rates of oxidation were faster for the plasma process. Irradiation of chitosan solution showed that UV/ozone induces depolymerization. In both plasma and UV/ozone reactions, the main active component for surface modification was UV irradiation at a wavelength below 360 nm [231]. 

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. 

The zeolites-chitosan composites were prepared by adding a known amount of zeolite (X, Y, or mordenite) into a 3 % chitosan solution in 1 % aqueous acetic acid. The zeolite powder was dispersed in the chitosan solution and stirred at room temperature during 1-2 hours. The gelling procedures were later carried out like as in the absence of zeolites. 

Ilium et al. [49] evaluated chitosan solutions as delivery platforms for nasal administration of insulin to rats and sheep. They reported a concentration-dependent absorption-enhancing effect with minimal histological changes of the nasal mucosa in all concentrations applied. 

Let us consider now the case of a specific ionic polysaccharide. The unique properties of complexes of the cationic chitosan with non-ionic sorbitan esters provides an interesting example. Grant and co-workers (2006) have established that mixtures of chitosan and surfactant form emulsion-like solutions and/or creams, where the surfactant component is present as droplets or micelle-like particles and the chitosan solution acts as the system s continuous phase. It was established that the length and the degree of saturation of the surfactant hydrocarbon chain have a significant impact on the development of the chitosan-surfactant complexes. Moreover, an optimal distance between the chitosan s protonated amine groups is required for effective interactions to occur between the polysaccharide and the sorbitan esters. 

This method used the physicochemical properties of polymers like chitosan, which is insoluble in alkaline pH medium and therefore precipitates/coa-cervates when it comes in contact with alkaline solution. Particles are produced by blowing chitosan solution into an alkali solution like NaOH using a compressed air nozzle to form coacervate droplets (Agnihotri et al. 2004). 

Immobilized HRP on an hybrid formed by colloidal carbon microspheres dispersed in a chitosan solution The immobilized HRP was used in the elaboration of a H202 sensor. The biosensor showed a fine linear correlation with H202 concentration and fast response to H202 at —0.15 V [49]... 

Fig. 13. Mean particle size (in nanometers SD,n = 4) of chitosan/TPP nanoparticles as affected by PEO initial concentration in the chitosan solution and PEO molecular weight (reproduced from Calvo et al. 1997, with permission of Wiley) [14]...

Since the concentrations of insulin to be administered in the sheep model would have been large, the insulin-loaded chitosan nanoparticles were not investigated in that model. However, the pharmacodynamics and pharmacokinetics of various insulin-chitosan preparations were compared with postloaded insulin-chitosan nanoparticles. It was found that chitosan solution and chitosan powder formulations were far better, with the chitosan powder formulation showing a bioavailability of 17% as against 1.3 and 3.6% for the chitosan nanoparticles and chitosan solution [72], The effects of the concentration and osmolarity of chitosan and the presence of absorption enhancers in the chitosan solution on the permeation of insulin across the rabbit nasal mucosa in vitro and in vivo were investigated, and the same... 

FIGURE 9 Effect of (a) concentrations, (b) osmolarity, and (c) medium of chitosan solution on mean serum glucose concentrations after nasal administration of lOIU/kg insulin to rats. Bars represent the standard deviation (SD) of five experiment. (Reproduced from ref. 73 with permission of Elsevier.)... 

FIGURE 18 Morphine plasma concentration in human volunteers after intravenous administration of morphine and after nasal administration of morphine as chitosan solution and powder formulations Mor Chi Sol, morphine solution containing chitosan Mor Chi PWD, morphine-chitosan powder IN, intranasal. (Reproduced from ref. 105 with permission of the American Society for Pharmacology and Experimental Therapeutics.)... 

The nasal absorption of insulin after administration in chitosan powder was the most effective formulation for nasal delivery of insulin in sheep compared to chitosan nanoparticles and chitosan solution [11], Similarly, chitosan powder formulations have been shown to enable an efficient nasal absorption of goserelin in a sheep model where bioavailabilities of 20-40% were obtained depending on the nature of the formulation [9],... 

Chitin and chitosan can be assayed by first-derivative UV/Vis method using phosphoric acid (85%) as solvent. The chitin and chitosan solution is heated to 60 °C for 40 min to enhance solubilization and then incubated in diluted solutions at 60 °C for 2 h, and the first-derivative absorption is measured at 203 nm (Fig. 2.31). The developed method was reported to be useful for the determination of DA in the whole range (20-90%). Similar wavelength selection was made in a previous study where a wavelength of 202 nm was used, when acetic acid was used as a solvent. 

Fig. 6 Concentration-time profile after nasal administration of 50 lU of insulin in a chitosan solution formulation to human volunteers (n = 8). Open square, nasal chitosan solution closed circle, subcutaneous. (Reprinted from Ref. " with permission from Wolters Kluwer Health, Adis International.)...

Aspden, T.J. Mason, J.D. Jones, N.S. Lowe, J. Skaugrud, O. Ilium, L. Chitosan as a nasal delivery system the effect of chitosan solutions on in vitro and in vivo mucociliary transport rates in human turbinates and volunteers. J. Pharm. Sci. 1997, 86 (4), 509-513. 

Recently, Du et al. reported an AChE electrochemical sensor based on enzyme-induced growth of gold nanoparticles (AuNPs) without the addition of any gold nano-seeds [17], They have successfully used [Fe (CN)6]3 74 as a probe to indicate the process of electron transfer across the interface and also analyze the enzyme inhibitor quantitatively. Initially, cleaned gold electrode was coated with 0.5 % (w/v) chitosan solution and AChE was later immobilized onto this chitosan modified gold electrode. CV results show that, AuNPs presence increases the peak current and decreases the peak separation. This confirms the presence of AuNPs on the chitosan modified electrode surface. However, the peak current of... 

Duan B et al (2004) Electrospinning of chitosan solutions in acetic acid with poly(ethylene oxide). J Biomater Sci Polym Hd 15(6) 797-811... 

Aspden, T., L. Blum and O. Skaugrud. 1997a. The effect of chronic nasal application of chitosan solutions on cilia beat frequency in guinea pigs. Ini. J. Pharm. 153 137-146. 

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