Biomedical Engineering Reference
In-Depth Information
line phosphatase activity in comparison to unmodified materials [126, 127].
Covalent immobilization of collagen I onto the surface of P3HB-8%3HV
films after ozone treatment and methacrylic acid grafting also enhanced
bone cell growth, as tested with mouse osteoblastic and rat osteosarcoma
cells [128].
Chondrocytes derived from rabbit articular cartilage were seeded on P3HB
films [129] and porous scaffolds [48, 89, 130, 131]. Cells attached to P3HB
films secreted both collagen II and collagen X, which are major cartilage-
specific ECM proteins, indicating maturational differentiation of chondro-
cytes into cartilage [129]. However, collagen II expression was low on P3HB
in comparison to PLLA scaffolds [131]. Enhanced cell adhesion and growth,
as well as more collagen II synthesis, could be obtained after addition of
P3HB-3HH to the P3HB matrices (see Sect. 5.2) [48, 89, 90, 129-131]. In an-
other study, P3HB-9%3HV porous matrices incubated with ovine chondro-
cytes showed lower cell densities in comparison with collagen sponges [132].
However, electrospun P3HB-5%3HV nanofibrous mats promoted chondro-
cyte attachment when compared with polymer films [133].
Other cell types tested included mammalian or human epithelial cells,
which showed little or no cell adhesion on P3HB fiber-based “wool”. However,
surface treatment with acidic or alkaline solutions promoted cell proliferation
on these fibers [134, 135].
Cells of the human respiratory mucosa (fibroblasts and epithelial cells)
have been incubated with P3HB films as a potential replacement matrix of
respiratory mucosa after surgical resections. However, while PLLA and col-
lagen supported cell growth, P3HB showed cell growth only after surface
modification by intense ammonia plasma treatment. No differentiation of ep-
ithelial cells with beating cilia could be found on all materials during the
6-week study [136].
The attachment rate of human retinal pigment epithelium cells was higher
on P3HB-8%3HV films modified by oxygen plasma than on unmodified
films due to increasing hydrophilicity and decreasing surface roughness. The
cells were grown to confluency as an organized monolayer suggesting P3HB-
8%3HV as a potential temporary substrate for subretinal transplantation to
replace diseased or damaged retinal pigment epithelium [137].
An excellent biocompatibility of P3HB was found in cell culture stud-
ies with Langerhans cells [138]. The biocompatibility of plasma-modified
P3HB [139] and P3HB-9%3HV [140] was assessed by analysis of insulin se-
cretion of Langerhans cells cultured on the polymer films. The following
order of insulin secretion was found during the first 2 days of cell incuba-
tion: oxygen
>
allylamine
>
allylalcohol
>
nontreated
>
argon
>
water plasma
treatment [140].
Cell culture experiments using mouse liver cells (endothelial cells and hep-
atocytes) grown on P3HB and P3HB-3HV films (15%, 28%3HV)suggested
lack of cytotoxicity of the highly purified materials tested [102]. The adhesion
