Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering.
Distribution of water in three classes of biomedically relevant and degradable polymers was investigated using small-angle neutron scattering. In semicrystalline polymers, such as poly(lactic acid) and poly(glycolic acid), water was found to diffuse preferentially into the non-crystalline regions. In amorphous polymers, such as poly(d,l-lactic acid) and poly(lactic-co-glycolic acid), the scattering after 7 days of incubation was attributed to water in microvoids that form following the hydrolytic degradation of the polymer. In amorphous copolymers containing hydrophobic segments (desaminotyrosyl-tyrosine ethyl ester) and hydrophilic blocks (poly(ethylene glycol) (PEG)), a sequence of distinct regimes of hydration were observed: homogeneous distribution (∼10Å length scales) at <13 wt.% PEG (∼1 water per EG), clusters of hydrated domains (∼50Å radius) separated at 24 wt.% PEG (1-2 water per EG), uniformly distributed hydrated domains at 41 wt.% PEG (∼4 water per EG) and phase inversion at >50 wt.% PEG (>6 water per EG). Increasing the PEG content increased the number of these domains with only a small decrease in distance between the domains. These discrete domains appeared to coalesce to form submicron droplets at ∼60°C, above the melting temperature of crystalline PEG. The significance of such observations on the evolution of micrometer-size channels that form during hydrolytic erosion is discussed.
Rutgers University, New Jersey Center for Biomaterials, Piscataway, NJ 08854, USA.
A
A
Luk
N S
NS
Murthy
W
W
Wang
R
R
Rojas
J
J
Kohn
D001672:Biocompatible Materials / Q000737:chemistry*; D001704:Biopolymers / Q000737:chemistry; D005898:Glass / Q000737:chemistry; D007455:Iodine / Q000737:chemistry; D019344:Lactic Acid / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D033363:Neutron Diffraction / Q000379:methods*; D010316:Particle Size; D011091:Polyesters; D011100:Polyglycolic Acid / Q000737:chemistry; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry; D053838:Scattering, Small Angle; D013997:Time Factors; D044366:Transition Temperature; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry; D014867:Water / Q000737:chemistry*
D001672:Biocompatible Materials; D001704:Biopolymers; D011091:Polyesters; D011108:Polymers; C505373:poly(desaminotyrosyl-tyrosine-ethyl ester carbonate); D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D014443:Tyrosine; C033616:poly(lactide); D007455:Iodine