Purpose. To study the interaction occurring between ketoprofen (KET) and poly(lactic-co-glycolic acid) (PLGA, 50:50) leading to polymer plasticization and to assess its physical state within the polymer matrix. Methods. PLGA films containing different amounts of KET were prepared by solvent casting and characterized by scanning electron microscopy, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Results. DSC evidenced that KET acted as a plasticizer in a similar biphasic way to both end-capped and uncapped PLGAs. At KET contents of 20-35%, depending on the investigated polymer, the Tg was around 23°C. Higher KET contents did not further lower the Tg and the excess of drug was found to crystallize into the polymeric matrix. Experimental Tgs deviated negatively from the predicted probably because of hydrogen bonding. The FTIR spectra of PLGA films, loaded with different amounts of KET, showed a shift to higher wavenumbers for the peaks at 1697 and 1655 cm-1 confirming the presence of KET-PLGA interactions, probably ascribable to hydrogen bonds. The hydrogen bonding was hypothesized between the KET carboxylic group and the PLGA carbonyl groups along the polymer backbone. Conclusion. KET-PLGA hydrogen bonding is probably responsible for the observed plasticizing effect. KET, behaving as a lubricant, may disrupt polymer chain-chain hydrogen bonding removing further barriers to bond rotation thus increasing chain mobility.
Plasticizing Effect of Ketoprofen on Plolylactide-co-Glicolide.
BLASI, PAOLO;SCHOUBBEN, Aurelie Marie Madeleine;GIOVAGNOLI, Stefano;RICCI, Maurizio;ROSSI, Carlo
2006
Abstract
Purpose. To study the interaction occurring between ketoprofen (KET) and poly(lactic-co-glycolic acid) (PLGA, 50:50) leading to polymer plasticization and to assess its physical state within the polymer matrix. Methods. PLGA films containing different amounts of KET were prepared by solvent casting and characterized by scanning electron microscopy, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Results. DSC evidenced that KET acted as a plasticizer in a similar biphasic way to both end-capped and uncapped PLGAs. At KET contents of 20-35%, depending on the investigated polymer, the Tg was around 23°C. Higher KET contents did not further lower the Tg and the excess of drug was found to crystallize into the polymeric matrix. Experimental Tgs deviated negatively from the predicted probably because of hydrogen bonding. The FTIR spectra of PLGA films, loaded with different amounts of KET, showed a shift to higher wavenumbers for the peaks at 1697 and 1655 cm-1 confirming the presence of KET-PLGA interactions, probably ascribable to hydrogen bonds. The hydrogen bonding was hypothesized between the KET carboxylic group and the PLGA carbonyl groups along the polymer backbone. Conclusion. KET-PLGA hydrogen bonding is probably responsible for the observed plasticizing effect. KET, behaving as a lubricant, may disrupt polymer chain-chain hydrogen bonding removing further barriers to bond rotation thus increasing chain mobility.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
