Page 598 - Read Online

Saxena et al. Mini-invasive Surg 2020;4:62 I http://dx.doi.org/10.20517/2574-1225.2020.68 Page 7 of 15

enhanced from 34.7% ± 2.7% to 43.9% ± 2.8%. Moreover, the designed model showed realistic simulation
with > 99% accuracy, when small myofiber strain in the nearby solidified hydrogel was kept at 13 mm
away from the implant. These findings clearly showed that solidified alginate-based materials may mimic
the mid-wall structure of the left ventricles, and can be used for various cardiac applications. Both of the
latter studies showed the effective interaction of cardiac cells with alginate. Alginate hydrogels possess the
required stiffness as well as the mechanical properties in comparison to cardiac cells, demonstrating them
as one of the most suitable candidates for use in the treatment of MI.

In addition, there are various other properties that also make alginate a suitable candidate for use in
the treatment of MI. Its non-toxicity to blood cells has been a keen objective for researchers. Various
[42]
studies have been done on the blood cell toxicity of alginates. In this direction, Qi et al. studied alginate
oligosaccharide for CTE and demonstrated its effect on the human platelet aggregation. A concentration-
dependent inhibition of human platelet aggregation, clot retraction and spreading was obtained for the
alginate oligosaccharide in the concentration range of 0.1-1.0 mg/mL. Similarly, ATP release was found
to be concentration-dependent and was induced by thrombin and collagen formation. Bleeding time was
found to be 534 ± 62 s in vehicle control and 581 ± 60 s in mice with alginate pretreatment. These findings
demonstrated the blood compatibility of the alginate and its plausible applications in the treatment of MI.
In addition, the blends of alginate with various materials have also been explored to obtain the desired
[24]
biocompatibility for the biomaterial-based treatment of MI. In this regard, Curley et al. designed an
injectable alginate/ECM hydrogel for the acellular treatment of MI. The storage modulus, compressive
modulus and dynamic modulus for high G block alginate/ECM hybrid hydrogel at day 1 were found to be 1.6,
29 and 14 kPa, respectively. The excellent cell proliferation (> 85%) with metabolically active cells (> 100%)
as compared to the control was obtained, proving the hybrid alginate-ECM system to be a suitable
candidate for non-invasive treatment of MI. All these studies showed that alginate-based materials have
excellent biological properties for CTE.

PEG-BASED HYDROGELS FOR PCI
PEG has been utilized for various biomedical applications because of their highly tunable size and
orientations. PEG is a polyether compound based on its molecular weight. It is also known as polyethylene
oxide or polyoxyethylene. PEG is considered a water-soluble, low immunogenic and biocompatible
polymer. PEGylation expands the orientation as well as the size of the conjugated compounds, which
consequently results in resistance to enzymatic digestion, making it suitable for various biomedical
[43]
applications, including the treatment of MI . PEG has various properties that makes it an ideal candidate
to be used as hydrogel material in PCI. Additionally, its different solvent-based orientations provide a
tunability for various applications. For example, in hexadecane, it carries a well described freely jointed
chain structure, whereas in water, a deformation in the supra-structure within the polymer has been
[44]
observed, resulting in entropic to enthalpic elasticity . This restricts its water-based applicability in terms
of mechanical properties and biocompatibility.

Various approaches have been examined to use PEG for PCI in the treatment of MI on the basis of its
solvent-selective elasticity as well as water solubility. Recently, Boyacioglu et al. studied the shape
[45]
memory behavior of PEG plasticized Polylactic acid (PLA)/thermoplastic polyurethane (TPU) blends. The
shape memory behavior was investigated as a function of PLA/TPU ratio, plasticizer molecular weight
and programming conditions. The plasticization efficiency was found to decrease with increase in molecular
weight of PEG. It was claimed that with an increase in TPU content, the recovery ratio between 40-55 °C
was also increased. However, at 60 °C for 20/80 PLA/TPU blends, the maximum total recovery (> 80%)
was obtained because of the strong elasticity of TPU. The shape memory values were found to be dependent
on PEG molecular weight in a reverse order, and the blend was able to manage 245 kPa of stress, indicating
its applicability for PCI in the treatment of MI.