In vitro degradation of thin poly(DL-lactic-co-glycolic acid) films

Abstract

This study was designed to investigate the in vitro degradation of thin poly(DL-lactic-co-glycolic acid) (PLGA) films for applications in retinal pigment epithelium transplantation and guided tissue regeneration. PLGA films of copolymer ratios of 75:25 and 50:50 were manufactured with thickness levels of 10 microm (thin) and 100 microm (thick). Degradation of the films occurred during sample processing, and thin films with a higher surface area to volume ratio degraded faster. Sample weight loss, molecular weight loss, dimensional, and morphological changes were analyzed over a 10-week period of degradation in 0.2 M of phosphate-buffered saline (PBS), pH 7.4, at 37 degrees C. All PLGA films degraded by heterogeneous bulk degradation. Sample weights remained relatively constant for the first several weeks and then decreased dramatically. The molecular weights of PLGA films decreased immediately upon placement in PBS and continued to decrease throughout the time course. PLGA 50:50 films degraded faster than 75:25 films due to their higher content of hydrophilic glycolic units. The results also demonstrated that thick films degrade faster than corresponding thin films with the same composition. This was attributed to the greater extent of the autocatalytic effect, which further was confirmed by heterogeneous gel permeation chromatograms. These studies suggest that the degradation rate of thin films can be engineered by varying film thicknesses.

Modelling the degradation and elastic properties of poly(lactic-co-glycolic acid) films and regular open-cell tissue engineering scaffolds

“…In Figure 10B, the homogenous, heterogeneous, and transition regimes predicted in the current study are compared to experimental observations of homogenous and heterogeneous diffusion in different sized samples (Chen et al, 1997;Grizzi et al, 1995;Lu et al, 1999;Park, 1995;Shirazi et al, 2014;Spenlehauer et al, 1989;Vey et al, 2008). Grizzi et al (1995) has proposed a range of 200-300 μm as a critical thickness above which the poly(D,L-lactic acid) polymers (plate, film, microsphere)(which have a similar chemical structure and degradation behaviour to PLGA) undergo heterogeneous degradation.…”

“…Grizzi et al (1995) has proposed a range of 200-300 μm as a critical thickness above which the poly(D,L-lactic acid) polymers (plate, film, microsphere)(which have a similar chemical structure and degradation behaviour to PLGA) undergo heterogeneous degradation. The heterogeneous degradation of PLGA films with thicknesses of 300 μm, 250 μm, and 5-100 μm has been shown by Vey et al (2008), Shirazi et al (2014), and Lu et al (1999), respectively. Spenlehauer et al (1989) has showed that PLGA microspheres less than 200 μm in diameter undergo a homogeneous degradation.…”

“…Computed predictions correlate strongly with published experimentally observed trends of degradation for the PLGA devices with different sizes. Some authors have studied the degradation rates for PLGA devices 200 μm to as small as 0.53 μm in size (Dunne et al, 2000;Grayson et al, 2005;Grizzi et al, 1995;Lu et al, 1999;Witt and Kissel, 2001). In these studies, it has been observed frequently that the degradation time is significantly shorter in the thicker samples due to the autocatalytic effect of the degradation products.…”

“…Diffusion of the degradation products may occur more slowly in a large-sized sample due to the greater diffusion length (Dunne et al, 2000;Grayson et al, 2005;Grizzi et al, 1995;Lu et al, 1999;Witt and Kissel, 2001). This leads to accumulation of degradation products inside the polymer matrix, which are able to catalyse hydrolysis of the other ester bonds and consequently accelerates the degradation process.…”

Impact of PEG and PEG- b -PAGE modified PLGA on nanoparticle formation, protein loading and release

“…The lack of influence of the different Mn of PLGA or the lactic:glycolic acid ratio on protein release within a particular polymer group could be due to the degradation behavior of the polymers. Systematic studies of the degradation of the well-known PLGA with different lactic:glycolic acid ratios over 70 days or longer, show a faster degradation for a PLGA lactic:glycolic acid ratio of 50:50 and slower degradation for PLGA with a lactic:glycolic acid ratio of 75:25 (Lu et al, 2000(Lu et al, , 1999. However, the difference in release between these PLGAs is typically visible only after 10 to 20 days and is almost negligible for the first days.…”