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allied
academies
Materials-Metals 2017
Page 55
November 16-17, 2017 Paris, France
13
th
Annual Conference on
Materials Science, Metal and Manufacturing
Journal of Materials Science and Nanotechnology
Volume 1 Issue 2
Applicability of polyisobutylene-based
polyurethane structures in biomedical disciplines:
some calcification and protein adsorption studies
Nur Cicek Kekec
1
, Nihan Nugay
1
, Kalman Toth
2
, Turgut Nugay
1
and
Joseph P Kennedy
2
1
Bogazici University, Turkey
2
The University of Akron, USA
I
nrecent years, polyurethane structures arepaving theway for
elastomer usage in biology, humanmedicine and biomedical
application areas. Polyurethanes having a combination of high
oxidative and hydrolytic stability and excellent mechanical
properties are focused due to enhancing the usage of PUs
especially for implantable medical device application such
as cardiac-assist. Currently, unique polyurethanes consisting
of polyisobutylenes as soft segments and conventional hard
segments, named as PIB-basedPUs, are developedwithprecise
NCO/OH stoichiometry (~1.05) for obtaining PIB-based
PUs with enhanced properties (i.e., tensile stress increased
from ~11 to ~26 MPa and elongation from ~350 to ~500%).
Static and dynamic mechanical properties were optimized
by examining stress-strain graphs, self-organization and
crystallinity (XRD) traces, rheological (DMA,creep) profiles
and thermal (TGA,DSC) responses. Annealing procedure
was applied for PIB-based PUs. Annealed PIB-based PU
shows ~26 MPa tensile strength, ~500% elongation, and ~77
Microshore hardness with excellent hydrolytic and oxidative
stability. The surface characters of them were examined with
AFM and contact angle measurements. Annealed PIB-based
PU exhibits the higher segregation of individual segments and
surface hydrophobicity thus annealing significantly enhances
hydrolytic and oxidative stability by shielding carbamate
bonds by inert PIB chains. According to improved surface
and microstructure characters, greatly efforts are focused
on analyzing protein adsorption and calcification profiles.
In biomedical applications especially for cardiological
implantations, protein adsorption inclination on polymeric
heart valves is undesirable hence protein adsorption from
blood serum is followed by platelet adhesion and subsequent
thrombus formation.The protein adsorption character of PIB-
based PU examines by applying Bradford assay in fibrinogen
and bovin serum albumin solutions. Like protein adsorption,
calcium deposition on heart valves is very harmful because
vascular calcification have been proposed activation of
osteogenic mechanism in the vascular wall, loss of inhibitory
factors, enhance bone turnover and irregularities in mineral
metabolism. The calcium deposition on films is characterized
by incubating samples in simulated body fluid solution
and examining SEM images and XPS profiles. PIB-based
PUs are significantly more resistant to hydrolytic-oxidative
degradation, protein adsorption and calcium deposition than
ElastEonTM E2A, a commercially available PDMS-based PU,
widely used for biomedical applications.
nurcicekkekec@gmail.comMater Sci Nanotechnol 2017, 1:2