Biocompatible groups

Colak and co-workers [56] investigated the hydrophilic adjustments of an amphiphilic polynorbornene, poly 3, via the incorporation of hydrophilic, biocompatible groups, and determined the effects on haemolytic and antibacterial activity. It was shown that increasing the hydrophilicity reduced the antibacterial properties, which could... 

Applications. Polymers with small alkyl substituents, particularly (13), are ideal candidates for elastomer formulation because of quite low temperature flexibiUty, hydrolytic and chemical stabiUty, and high temperature stabiUty. The abiUty to readily incorporate other substituents (ia addition to methyl), particularly vinyl groups, should provide for conventional cure sites. In light of the biocompatibiUty of polysdoxanes and P—O- and P—N-substituted polyphosphazenes, poly(alkyl/arylphosphazenes) are also likely to be biocompatible polymers. Therefore, biomedical appHcations can also be envisaged for (3). A third potential appHcation is ia the area of soHd-state batteries. The first steps toward ionic conductivity have been observed with polymers (13) and (15) using lithium and silver salts (78). 

Skeletal Biocompatibility. Two Substituent Groups Attached to the Same Phosphazene Skeleton. Hydrolytical Instability 0 II — NH- CH2— C- OC2H5 Glycine or Lower Alkyl Aminoacid Esters Hydrolytically Unstable Polymers. Bioerodible Materials. Drug Delivery Systems. Tissue Engineering... 

Hybrid organosilicon-organophosphazene polymers have also been synthesized (15-18) (structure ) (the organosilicon groups were introduced via the chemistry shown in Scheme 11). These are elastomers with surface contact angles in the region of 106°. Although no biocompatibility tests have been conducted on these polymers, the molecular structure and material properties would be expected to be similar to or an improvement over those of polysiloxane (silicone) polymers. 

After 7 days, the acute inflammatory response at the implantation site was evaluated. Bisphenol A resulted in a moderate level of irritation at the implantation site and was clearly the least biocompatible test substance. Tyrosine derivatives containing the benzyloxycar-bonyl group caused a slight inflammatory response, while all other tyrosine derivatives produced no abnormal tissue response at all. These observations indicate that tyrosine dipeptide derivatives, even if fully protected, are more biocompatible than BPA, a synthetic diphenol. ... 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

This chapter is concerned with the recent research concerning the design of biocompatible ion sensors, especially the results of our research group. 

In an attempt to identify new, biocompatible diphenols for the synthesis of polyiminocarbonates and polycarbonates, we considered derivatives of tyrosine dipeptide as potential monomers. Our experimental rationale was based on the assumption that a diphenol derived from natural amino acids may be less toxic than many of the industrial diphenols. After protection of the amino and carboxylic acid groups, we expected the dipeptide to be chemically equivalent to conventional diphenols. In preliminary studies (14) this hypothesis was confirmed by the successful preparation of poly(Z-Tyr-Tyr-Et iminocarbonate) from the protected tyrosine dipeptide Z-Tyr-Tyr-Et (Figure 3). Unfortunately, poly (Z-Tyr-Tyr-Et iminocarbonate) was an insoluble, nonprocessible material for which no practical applications could be identified. This result illustrated the difficulty of balancing the requirement for biocompatibility with the need to obtain a material with suitable "engineering" properties. 

In order to identify tyrosine derivatives that would lead to polymers that are processible, mechanically strong, and also biocompatible, we initiated a detailed investigation of the structure-property relationships in polyiminocarbonates and polycarbonates. Since the amino and carboxylic acid groups of tyrosine dipeptide (the N and C termini) provide convenient attachment points, selected pendent chains can be used to modify the overall properties of the polymers. This is an important structural feature of tyrosine dipcptide derived polymers. 

Both types are hydrophobic materials that, depending on the side group arrangements, can exist as elastomers or as microcrystalline fiber- or film-forming materials. Preliminary studies have suggested that these two classes of polyphosphazenes are inert and biocompatible in subcutaneous tissue implantation experiments. 

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