Preparation of comb‐type grafted hydrogels composed of polyacrylamide and chitosan and their use for DNA adsorption

Abstract

Comb-type grafted hydrogels composed of polyacrylamide (PAAm) and chitosan (CT) were prepared and used for DNA adsorption. Instead of direct grafting of the acrylamide monomer onto the CT chain, semitelechelic PAAm with carboxylic acid end groups (PAAm-COOH) was synthesized by free-radical polymerization with mercaptoacetic acid as the chain-transfer agent, and it was grafted onto CT with amino groups. The synthesis of telechelic PAAm-COOH and the formation of comb-type grafted hydrogels were confirmed by attenuated total reflectance/Fourier transform infrared spectroscopy and scanning electron microscopy measurements. The prepared comb-type grafted hydrogels were used as sorbents in DNA adsorption experiments conducted at þ4 C in a tris(hydroxymethyl)aminomethane/ ethylenediaminetetraacetic acid solution of pH 7.4. DNA adsorption capacities as high as 2.0 Â 10 3 lg of DNA/g of dry gel could be achieved by the comb-type hydrogels with higher PAAm contents. This value was approximately 6 times higher than that of CT alone. In addition, the comb-type hydrogels showed a high adsorption/desorption rate depending on the PAAm content in the hydrogel. As a result, these comb-type hydrogels carrying higher amounts of DNA may be considered good candidates for achieving higher removal rates for anti-DNA antibodies and for effective gene therapy systems.

DNA adsorption on poly(N,N‐dimethylacrylamide)‐grafted chitosan hydrogels

“…The adsorption capacity of polyethyleneimide attached poly( p ‐chloromethylstyrene) beads was found to be 2900 μg DNA/g polymer 26. Moreover, the adsorption value obtained in this study was reasonably higher relative to our previously reported adsorption capacities of PAAm‐ g ‐CT hydrogels (2000 μg DNA/g dry gel) 14. This may be attributed to both the diminish of free amino groups of CT after the crosslinking by GDA and the higher −N(CH 3 ) 2 content of the PDMAAm‐ g ‐CT hydrogels.…”

“…On the other hand, the equilibrium DNA adsorption capacity of the ungrafted CT hydrogel was very low (473 μg DNA/g dry gel). The introduction of PDMAAm into the CT gel structure resulted in an appreciable increase in the equilibrium DNA adsorption capacity in comparison with the DNA adsorption capacity of similar more hydrophilic hydrogels, such as PAAm‐ g ‐CT 14. The high adsorption capacity for the PDMAAm‐ g ‐CT hydrogels may be attributed to the increase of the number of grafting chains with −N(CH 3 ) 2 on the hydrogels.…”

“…In our previous study, we prepared poly(acrylamide) grafted chitosan [PAAm‐ g ‐CT] hydrogels and used for DNA adsorption 14. The results of this and other studies indicated that higher anti‐DNA antibody adsorption capacity could be obtained with polymeric supports carrying higher amounts of adsorbed DNA on their surfaces 14–17. Moreover, it was also shown that more quantitative and stable adsorption of DNA could be achieved by hydrophobic interactions between the polymeric support and DNA molecules 14–19…”

“…In our previous study, we prepared poly(acrylamide) grafted chitosan [PAAm‐ g ‐CT] hydrogels and used for DNA adsorption 14. The results of this and other studies indicated that higher anti‐DNA antibody adsorption capacity could be obtained with polymeric supports carrying higher amounts of adsorbed DNA on their surfaces 14–17.…”

Preparation and characterization of metal‐chelated poly(HEMA‐MAH) monolithic cryogels and their use for DNA adsorption

“…Different polymeric adsorbents have been suggested as supports for immobilization of DNA 11–18. In order to treat some autoimmune diseases, such as systemic lupus erythematosus (SLE), DNA‐affinity adsorbents have been used for removal of anti‐double‐stranded DNA antibodies from the sera of patients suffering from SLE 19–22.…”