Biodegradable polymer/hydroxyapatite (HA) composites have potential application as bone graft substitutes. Thin films of polymer/HA composites were produced, and the initial attachment of primary human osteoblasts (HOBs) was assessed to investigate the biocompatibility of the materials. Poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLA) were used as matrix materials for two types of HA particles, 50-microm sintered and submicron nonsintered. Using ESEM, cell morphology on the surfaces of samples was investigated after 90 min, 4 h, and 24 h of cell culture. Cell activity and viability were assessed after 24 h of cell culture using Alamar blue and DNA assays. Surface morphology of the polymer/HA composites and HA exposure were investigated using ESEM and EDXA, respectively. ESEM enabled investigation of both cell and material surface morphology in the hydrated condition. Combined with EDXA it permitted chemical and visual examination of the composite. Differences in HA exposure were observed on the different composite surfaces that affected the morphology of attached cells. In the first 4 h of cell culture, the cells were spread to a higher degree on exposed HA regions of the composites and on PLA than they were on PCL. After 24 h the cells were spread equally on all the samples. The cell activity after 24 h was significantly higher on the polymer/HA composites than on the polymer films. There was no significant difference in the activity of the cells on the various composite materials. However, cells on PCL showed higher activity compared to those on PLA. A polymer surface exhibiting "point exposure" of HA appeared to provide a novel and favorable substrate for primary cell attachment. The cell morphology and activity results indicate a favorable cell/material interaction and suggest that PLA and PCL and their composites with HA may be candidate materials for the reconstruction of bony tissue. Further investigations regarding long-term biomaterial/cell interactions and the effects of acidic degradation products from the biodegradable polymers are required to confirm their utility.
Copolymers of polylactide and poly(ethylene glycol)
(PLA−PEG), which self-disperse in water to form
spherical nonionic micelles, have been investigated as a novel
biodegradable drug delivery system. These
copolymers are defined by the molecular weight ratios of their
polylactide to poly(ethylene glycol) components
(1.5:2 PLA−PEG and 2:5 PLA−PEG) and gave two peaks when purified by
gel permeation chromatography
(GPC). The first peak consisted of spherical micelles with a
diameter of 15.6 nm for 1.5:2 PLA−PEG, and
18.9 nm for 2:5 PLA−PEG micelles after analysis by dynamic light
scattering (DLS) and by transmission
electron microscopy (TEM). The second peak was a PLA-depleted
species resulting from the synthesis and
did not form micelles. Testosterone and sudan black B (SBB), which
have different hydrophobicities, were
used as “model drugs” to evaluate the drug loading ability of the
micelles. Ultracentrifugation sedimentation
velocity studies confirmed that solubilization of the model drugs had
occurred by micellar incorporation.
Higher drug loading was obtained for the 1.5:2 PLA−PEG micelles
(63.9% (w/w) of SBB, 0.74% (w/w) of
testosterone) than for the 2:5 PLA−PEG micelles (59.0% (w/w) of SBB,
0.34% (w/w) of testosterone). The
amount of testosterone solubilized was therefore significantly lower
than SBB for both copolymers. Stability
testing in the presence of salt suggested that the micelles had
sterically stabilized surfaces. In vivo
studies
in the rat, using a radioactive marker, showed that PLA−PEG micelles
demonstrated extended circulation
times in the blood during the period of study (3 h). The 1.5:2
PLA−PEG showed increased blood levels
and lower uptake of the micelles by the liver compared to the 2:5
PLA−PEG micelles. This is thought
to be due to differences in the packing density of the copolymer
molecules on the micelle surface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.