Multiscale analysis of water uptake and erosion in biodegradable polyarylates

Abstract

The role of hydration in degradation and erosion of materials, especially biomaterials used in scaffolds and implants, was investigated by studying the distribution of water at length scales from 0.1 nm to 0.1 mm using Raman spectroscopy, small-angle neutron scattering (SANS), Raman confocal imaging, and scanning electron microscopy (SEM). The measurements were demonstrated using L-tyrosine derived polyarylates. Bound- and free- water were characterized using their respective signatures in the Raman spectra. In the presence of deuterium oxide (D2O), H-D exchange occurred at the amide carbonyl but was not detected at the ester carbonyl. Water appeared to be present in the polymer even in regions where there was little evidence for N-H to N-D exchange. SANS showed that water is not uniformly dispersed in the polymer matrix. The distribution of water can be described as mass fractals in polymers with low water content (~5 wt%), and surface fractals in polymers with larger water content (15 to 60 wt%). These fluctuations in the density of water distribution are presumed to be the precursors of the ~ 20 μm water pockets seen by Raman confocal imaging, and also give rise to 10–50 μm porous network seen in SEM. The surfaces of these polymers appeared to resist erosion while the core of the films continued to erode to form a porous structure. This could be due to differences in either the density of the polymer or the solvent environment in the bulk vs. the surface, or a combination of these two factors. There was no correlation between the rate of degradation and the amount of water uptake in these polymers, and this suggests that it is the bound-water and not the total amount of water that contributes to hydrolytic degradation.

In vitro study on the deterioration of polypropylene hernia repair meshes

“…Following incubation, the samples were removed from water, wiped free of surface moisture and weighed. WU was calculated using the following formula: where M 0 represents the original dry weight of the sample and M f —the weight of the sample after being kept in water. Five replicates were performed for each of the mesh samples.…”

“…Following incubation, the samples were removed from water, wiped free of surface moisture and weighed. WU was calculated using the following formula 23 :…”

Developing a Suitable Model for Water Uptake for Biodegradable Polymers Using Small Training Sets

“…Water uptake was obtained for the selected polymers from the L-tyrosine-derived polyarylates combinatorial library ( Table 1 ) using 3 H-labeled water, as described previously [ 45 ]. Briefly, films 1 cm in diameter were incubated in 3 H-radiolabeled water (0.2 μ Ci/mL) at 37°C.…”

Advances in Biomedical Raman Microscopy

“…22 Studies of dental materials showed chemical differences in ceramic properties, 23 and the role of hydration was studied in the degradation of other implants and scaffold materials. 24 The progress described above was accomplished through development of better and more efficient instrumentation, such as those noted in a recent review. 25 Recent advances in instrumentation suggest continued growth in the use of Raman microscopy.…”

“…Raman microscopy was able to discriminate between cholesterol esters, cholesterol, and triglycerides in atherosclerotic plaques in rabbits . Studies of dental materials showed chemical differences in ceramic properties, and the role of hydration was studied in the degradation of other implants and scaffold materials …”