Synthesis of hyaluronic acid-ethylenediamine derivative (HA-EDA). 3 g of tetrabutylammonium salt of hyaluronic acid (HA-TBA) prepared by hyaluronic acid solution neutralization using tetrabutylammonium hydroxide solution, were dissolved in 270 ml of anhydrous dimethylsulfoxide (weight- average molecular weight of hyaluronic acid 270 kDa).
The suitable amount of bis(4-nithrophenyl) carbonate (4-NPBC) chosen in a way to obtain ratios moles of 4-NPBC/moles of HA-TBA respectively equal to 0.75,
0.5 and 0.25 were dissolved in 30 ml of anhydrous dimethylsulfoxide; this solution was added drop by drop to the HA-TBA solution at 40 °C under stirring. After 4 h,
3 ml of ethylendiamine (EDA) were added drop by drop and the solution was left at
40 °C for other 3 h. Then the work-up of the reaction was accomplished by first precipitating the hyaluronic acid derivative into acetone then washing in the same solvent until a product without reaction intermediates has been obtained.
The obtained solid, formed by HA-TBA-EDA copolymer, was finely pounded. The sodium salt of the ethylendiamino derivative of HA, the derivative HA-EDA, has been obtained fluxing the solution in dimethylsulfoxide of HA-TBA-EDA through a column loaded with DOWEX 50 Wx8 resin activated in its sodium form. The product was recovered exchanging the DMSO solution against water using a dialysis procedure and then freeze-drying the aqueous solution.
Synthesis of hyaluronic acid-ethylenediamine derivative (HA-EDA). 3 g of tetrabutylammonium salt of hyaluronic acid (HA-TBA) prepared by hyaluronic acid solution neutralization using tetrabutylammonium hydroxide solution, were dissolved in 270 ml of anhydrous dimethylsulfoxide (weight- average molecular weight of hyaluronic acid 270 kDa).The suitable amount of bis(4-nithrophenyl) carbonate (4-NPBC) chosen in a way to obtain ratios moles of 4-NPBC/moles of HA-TBA respectively equal to 0.75,0.5 and 0.25 were dissolved in 30 ml of anhydrous dimethylsulfoxide; this solution was added drop by drop to the HA-TBA solution at 40 °C under stirring. After 4 h,3 ml of ethylendiamine (EDA) were added drop by drop and the solution was left at40 °C for other 3 h. Then the work-up of the reaction was accomplished by first precipitating the hyaluronic acid derivative into acetone then washing in the same solvent until a product without reaction intermediates has been obtained.The obtained solid, formed by HA-TBA-EDA copolymer, was finely pounded. The sodium salt of the ethylendiamino derivative of HA, the derivative HA-EDA, has been obtained fluxing the solution in dimethylsulfoxide of HA-TBA-EDA through a column loaded with DOWEX 50 Wx8 resin activated in its sodium form. The product was recovered exchanging the DMSO solution against water using a dialysis procedure and then freeze-drying the aqueous solution.
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