Bioerosion rates

Laurencin and coworkers213 have used a different approach to control the rate of bioerosion of polymers with amino acid ester side groups. They used hydrophobic 4-methylphenoxy cosubstituents ( 50%) to slow the rate of hydrolysis, and these polymers were employed to study the rate of release of inulin. Similar polymers are also being developed by the same investigators as tissue engineering substrates for bone regeneration.214"218... 

To verify that the in vitro and in vivo release rates were comparable, Ogawa and co-workers injected the microspheres into rats (Sprague-Daw-ley) and measured the amount of peptide remaining at the injection site over time (Ogawa et al, 1988c). The in vivo release was then compared to the release in vitro, which was performed by incubation of the microspheres in 33 mM phosphate buffer, pH 7.0, 0.05% Tween 80. As shown in Fig. 6, the in vivo and in vitro release were similar up to 21 days. However, the in vivo release decreased after 21 days, and 20% of the peptide remained after 35 days. Since significant bioerosion of the PLGA had occurred by 28 days, it... 

Epifluorescence spectroscopy, which follows biotic changes in the surface of plastic films, shows" that even a mild heat treatment, such as compression moulding, changes the polymer surface making it favourable to colonisation by microorganisms." " This technique can also be used to monitor the rate of complete colonisation of the polymer surface. This process, in the case of preaged polyethylene is followed rapidly by the bioerosion of the surface of the polymer. " ... 

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