Medical dry glass transition temperatures in the presence of

Medical
an Biomedical relevance

PU foam
materials have the biocompatibility and biodegrability that promote their
utility both in vivo and in vitro. PU foams have been reported that used in
nerve agent hydrolyzing enzyme, bone tissue engineering, absorption of
biological fluids, biocatalytic air filtering, injectable delivery systems, and
several other applications 36. Rodriguez et al 43 used polyurethane-based
shape memory polymer (SMP) foams in a porcine aneurysm model to determine
biocompatibility, localized thrombogenicity, and their ability to serve as a
stable filler material within an aneurysm. The results showed clotting was
initiated within the SMP foam at time 0, partial healing was observed at 30

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days, and
almost complete healing had occurred at 90 days in vivo, with minimal
inflammatory response. SMPs have
been shown to actuate below their dry glass transition temperatures in the
presence of moisture due to plasticization. This behavior has been proposed as
a self-actuating mechanism of SMPs in water/physiological media. Singhal et al.44 designed low-density SMPU foam for
biomaterial application. Nakhoda et al 45
developed a new class of polyurethane (PU)
biocomposites reinforced with green biocellulose nanofibers (BC) for
application in the field of tissue engineering and regenerative medicine.
SEM images results confirmed the formation of
the targeted interconnected porous structure with pore size in the range of 125–355mm and final porosity between 57–75 %. This porous structure allows for the
penetration of cells and helps with the bulk degradation of the scaffold for
potential applications in regenerative medicine.

Kaur et
al. 46 prepared hydrogel impregnated antimicrobial
polyurethane foam for absorption of radionuclide contaminated blood and
biological fluids using polyacrylamide (PAM) and
polyacrylamide-co-sodiumpolyacrylate (PAM-co-NaPA). The result showed PAM-impregnated-PUF of 910, 605, and
172% absorption

in water,
saline, and blood, respectively, whereas PAM-co-NaPA-impregnated-PUF absorption
of 1545, 1395, and 269% in water, saline, and blood, respectively in 24 h.

NaPA-impregnated-PUF
displayed 97% absorption of Tc99 and PUF sheets showed only 1%
absorption of Tc99 from whole blood. Therefore,
PAM-co-NaPA-impregnated-PUF sheets have strong potential to be used as matrices
for carrying the injured patients, from field conditions to hospitals expose to
nuclear, biological, and chemical environment.

Guelcher
et al 47 developed a polyurethane
foams scaffolds which can supported attachment of viable (>95%) MG-63 cells
under dynamic seeding conditions. The author considered this type PU will be
available as a consequence of the favorable biological and physical properties
of injectable polyurethane foam.

Cross-linked 3D biodegradable polyurethane
foams have been synthesized from biocompatible reactants as bone graft
substitutes by Gorna and Gogolewski 48. This porous
biodegradable PU foam scaffolds combined with the patient’s own bone marrow
could be such bone substitutes. The foams absorbed water and degrade in vitro
under controlled conditions. The polyurethane scaffolds obtained were used as
cancellous bone graft substitutes for soft tissue defects and treatment of
articular cartilage defects. The author optimised solvent-nonsolvent mixture to
have elastomeric biodegradable polyurethanes with an enhanced affinity toward
cells and tissues. 49 The PU foam scaffold had
regular interconnected pores, high water permeability, and a pore-to-volume
ratio of 90%, and can be additionally promoted by loading calcium phosphate
salts, then to make them become promising candidates for bone graft substitutes.
The author also studied the possibility of this biodegradable polyurethane
cancellous bone graft substitutes using in the treatment of iliac crest defects
50.

Guelcher 51 summarized tissue-engineered scaffolds the methods
of synthesis of biodegradable PURs, including thermally induced phase
separation, salt leaching, wet spinning, electrospinning, and carbon dioxide
foaming, and the application of these materials as scaffolds for regenerative
medicine. These materials have been reported to support the ingrowth of cells
and tissue in vitro and in vivo, and undergo controlled degradation to
noncytotoxic decomposition products.

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