Copolymer hydrogel

RA Siegel, M Falamarzian, BA Firestone, BC Moxley. pH controlled release from hydrophobic poly electrolyte copolymer hydrogels. J Controlled Release 8 179-182, 1988. 

KEY TERMS hydrophobic hydrophilic monomer cross-linking polymer copolymer hydrogel... 

We report here on copolymer hydrogels of N-isopropyl acrylamide (NIPAAm) and acrylamide (AAm) which are crosslinked with mediylene-bis-acrylamide (MBAAm) and which contain the enzyme asparaginase immobilized within the gel. 

Bioconjugate Synthesis—Stage 1. As described above, we have already demonstrated our ability to produce thermoresponsive copolymer hydrogel particles that possess groups for protein attachment. 

Brueggemeier, S. B., Wu, D., Kron, S. J., and Palecek, S. P. (2005) Protein-acrylamide copolymer hydrogels for array-based detection of tyrosine kinase activity from cell lysates. Biomacromolecules, 6, 2765-2775. 

Fig. 2. Swelling kinetics of 8 caffeine-loaded methyl mcthacrylate/jV.A -dimethylaminoethyl methacrylate copolymer hydrogels. ( ) pH 3, (A) pH 5. Siegel RA, Falamarzian M, Firestone BA, Moxley BC (1988) J Contr Rel 8 179. Reproduced with permission...

Thermal and pH sensitive heterogeneous copolymer hydrogels which contain silicone rubber domains within a temperature and pH sensitive copolymer of NIPA and acrylic acid have been synthesized by Dong et al. [60]. These materials contained macropores when swollen and collapsed much faster than homopolymers of iV-isopropylacrylamide. Biocatalyst immobilization using copolymers of NIPA and NN - dimethylaminopropylmethacrylamide have also been studied [61]. 

Podual, K., Doyle, F.J., and Peas, N.A. (2000). Preparation and dynamic response of cationic copolymer hydrogels containing glucose oxidase. Polymer, 41, 3975-3983. 

A summary of base-labile crosslinking agents is provided in Table 1. Hydrolytic stability of homopolymer and copolymer hydrogels are provided in Tables 2 and 3, respectively. 

TABLE 3. Degradation times for copolymer hydrogels crosslinked with NJ -dimethacryloyloxy)glutarylamide hydrolyzed in a hnffer solntion at pH 7.4 at 37° C. 

Siegel, R.A. Falamarzian, M. Firestone, B.A. Moxley, B.C. pH-controUed release hydrophobic/polyelectrolyte copolymer hydrogels. J. Control. Release 1988, 8, 179-182. 

Kuckling D, Richter A, Amdt K-F (2003a) Temperature and pH dependent swelling behavior of poly(A-isopropyl-acrylamide)-copolymer hydrogels and their use in flow control. Macromol Mater Eng 288 144-151... 

Increases in the levels of water swell of the PVA hydrogels were initially presumed to be possible according to the mechanism commonly followed by covalently cross-linked hydrogels, namely, the incorporation of monomer components with exceptional affinities for water (typically, charged species such as carboxylic acid functional monomers). Thus, copolymers of VTFA and maleic anhydride were prepared, which when solvolyzed in methanolic ammonium hydroxide, would be expected to give poly [(vinyl alcohol)-co-(maleic acid)] products. Film samples of such copolymer hydrogels were prepared, and surprising sensitivity of water swell to acidic comonomer content was observed (Table IV). 

Polymer composition is expressed as weight % of the vinyl acetate in the PVTFA/VOAc copolymer used to prepare the PVA (copolymer) hydrogels. 

Siegel RA, Falamarzian M, Firestone BA, Moxley BC. pH-controlled release from hydrophobic/polyelectrolyte copolymer hydrogels. J Contr Rel 1988 8 179-182. 

The release mechanism was explained by assuming that chain scission decreased the amount of effective crosslinks or entanglements present in the swollen copolymer matrix. Therefore, the resistance to the diffusion of proteins through the copolymer hydrogels was reduced. In the case of the observed zero-order release, the increasing permeability of the matrix in time may have compensated for the decline in the release rate caused by the reduced protein concentration in the matrix, to yield a constant release rate (50). 

Feil et al. have demonstrated the molecular separation of solutes of three different sizes by using a poly(NIPAAm-co-butyl methacrylate)(BMA) copolymer hydrogel membrane at several temperatures (18,19). The diffusion of urinine (MW 300) and dextran (MW 4400) was found to follow the... 

This ABA-type triblock copolymer was used as a drug release depot for continuous release of hiunan insulin and of glucagons-like peptide-1 (GLP-1). The observation of both reduced initial burst and a constant release of hmnan insulin from ReGel in vitro is due to the domain structure of the gel and to the modification of the association states of insulin by zinc. Animal studies using SD rats were performed to verify the release profile of insuhn from this ABA block copolymer hydrogel. ReGel formrdation maintained insulin release for up to 15 days, which could allow diabetic patients to reduce the number of insulin injections to two per month for basal insulin requirements (31). 

The observed release pattern from both types of microspheres lies in the distribution of the protein inside a microsphere, which is associated with the preparation method. In order to see this, FITC (fluorescein isothiocyanate)-insulin incorporated microspheres were observed under a confocal microscope, as shown in Fig. 7. For Msp A, a homogeneous distribution of fluorescence was observed while Msp B exhibited a rather heterogeneous distribution of FITC-insulin. In addition, Msp B shows significant surface fluorescence. These observations are, hence, consistent with the observed initial burst from Msp B and from the constant insulin release from Msp A over a prolonged period of time. It is reported that the constant release of insulin from triblock copolymer hydrogel may be attributed to the hydrophilic/hydrophobic domain structure of the gel. The incorporation of a significant fraction of insulin in the hydrophobic domain may have made possible... 

In recent years, many kinds of temperature-responsive PNIPAAm and its copolymer hydrogels with other acrylic monomers have been synthesized [142]. Besides being used for hydrogels, NIPAAm monomer can be grafted on to polymer substrates by electron beam, irradiation or UV-initiated graft polymerization to achieve special modification of polymer surfaces. Thus NIPAAm has been grafted on porous polymer films such as LDPE, PP, or polyamide films in order to prepare novel films for pervaporation of liquid mixtures or separation membranes [150,151]. 

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