SCIENTIFIC REPORT

Scientific report

Scientific report

Introduction

Chitosan, a linear binary heteropolysaccharide, is composed of ß-1,4-linked glucosamine (GlcN) with various degrees of N-acetylation of GlcN residues. Chitosan occurs naturally in some microorganisms, yeast and fungi (Illum et al., 2001). Its occurrence is much less widespread than that of chitin. Chitin is a linear chain consisting of N-acetyl-D-glucosamine (2 acetamido-2-deoxy-ß-D-gluconopyranose) joined together by ß(1?4) linkage. It is a non-toxic, biocompatible and biodegradable natural polymer of high molecular weight (~500,000 kDa). It is the second most common polysaccharide occurring in nature after cellulose.

Another approach to produce chitosan is by enzymatic N-deacetylation under relatively mild conditions. The commercially available chitosan is mostly derived by alkaline N-deacetylation from chitin of crustaceans because it is easily obtainable from the shells of crabs, shrimps, lobsters and krill. extraction of chitin and removal of calcium carbonate (CaCO3) with dilute hydrochloric acid from shells of crustaceans and deproteination with dilute aqueous sodium hydroxide. The second step is deacetylation of chitin by treating it with 40-50% aqueous sodium hydroxide at 110-115 °C for several hours without oxygen. Chitosan is produced when the degree of deacetylation (DD) is greater than 50% (Steenkamp et al., 2002). However, it was also reported that chitin with a DD of 75% or above is known as chitosan (Chang, 1983, 150).

The two polymers, chitin and chitosan have similar chemical structure and are analogues of the homopolymer cellulose where the respective acetamido and amino groups replace the hydroxyl group at carbon-2 as shown in Figure 1.2.

The difference between chitin and chitosan is in the acetyl content of the polymer where they can be distinguished by their solubility.

Preparation of Chitason film

First of all prepare a 2% v/v acetic acetic acid aqueous solution having 50 ml *2/100 = 1 ml pure acetic acid and then add 50 ml with the acetic acid, this step must be in fume hood to avoid the contamination. Shake the solution well by hand. Then measure the ph of solution, for this solution ph is 2.69. In the next step prepare a 0.02 % w/v indocyanine green of amount 50 ml *0.02/100 = 0.01 g IG and put 0.01 of IG green in epn durf tube. Then mix the IG green and acetic acid solution gently several times until all the stock will be clear and then prepare 1.7 % w/v chitosan powder in the amount 50ml *1.7/100= 0.86 g chitosan. Dissolve chitosan powder 0.86 g in 50 ml water contain acetic acid (1ml) and IG GREEN (0.01g) then after adding IG green the rest of procedure must be shield from light to avoid inactivation of IG and then put the chitosan solution 2 days on magnetic stirrer to dissolve the chitosan powder.

Chitosain plating

Take the chitosan after 2 days on magnetic stirrer to dissolve the chitosain powder and then prepare six plates to drop the chitosan inside them. Use the marker to make rectangular on the plate (5*4.5 cm) to drop the chitosan in them then use the disposable syringe to take the chitosain from the bottle and ...