Editing Synthesis of Chitosan Polymers (section)

== Chitosan PEG TAT<br>  ==

Low-molecular-weight (LMW) CS with a degree of deacetyla-<br>tion of 80% was obtained from Wako (Richmond, VA, USA). 

NHS-PEG-Malhex of HMW 5000 was obtained from Rapp Polymere (Tuebingen, Germany). 

Cysteine-terminated TAT peptide (GRKKRRQRRRGC-SH) with a MW of 1556.88 <br> 

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LMW CS was dissolved in 1% (v/v) acetic acid to yield a<br>concentration of 0.5% (w/v) CS and the pH was adjusted to<br>5 using 1 M NaOH. Either NHS-PEG-maleimide of PEG<br>with a MW of 513.50 (LMW) or 5000 (HMW) was added<br>to CS solutions in 10 M excess. The reaction proceeded<br>for 3 hours under inert conditions at room temperature.<br>Following the reaction, the pH was adjusted to 7 using 1 M<br>NaOH. The reaction was allowed to stir overnight under<br>similar conditions. Cysteine-terminated TAT was added<br>in a one to one or one to four molar ratio of PEG:TAT and<br>the reaction stirred continuously for another 4 hours under<br>similar conditions. Unreacted PEG and TAT were removed<br>from the reaction mix using a Zeba Desalting Spin gel filtra-<br>tion column with an exclusion limit of a MW of 7000. The<br>filtrate obtained consisted of CS-PEG-TAT polymer, used<br>to make nanoparticles under varying pH values.<br> 

[[Image:Chitosan PEG TAT.png|600px|Chitosan PEG TAT.png]]<br> 

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