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Shape-memory surfaces for cell mechanobiology

View Article: PubMed Central - PubMed

ABSTRACT

Shape-memory polymers (SMPs) are a new class of smart materials, which have the capability to change from a temporary shape ‘A’ to a memorized permanent shape ‘B’ upon application of an external stimulus. In recent years, SMPs have attracted much attention from basic and fundamental research to industrial and practical applications due to the cheap and efficient alternative to well-known metallic shape-memory alloys. Since the shape-memory effect in SMPs is not related to a specific material property of single polymers, the control of nanoarchitecture of polymer networks is particularly important for the smart functions of SMPs. Such nanoarchitectonic approaches have enabled us to further create shape-memory surfaces (SMSs) with tunable surface topography at nano scale. The present review aims to bring together the exciting design of SMSs and the ever-expanding range of their uses as tools to control cell functions. The goal for these endeavors is to mimic the surrounding mechanical cues of extracellular environments which have been considered as critical parameters in cell fate determination. The untapped potential of SMSs makes them one of the most exciting interfaces of materials science and cell mechanobiology.

No MeSH data available.


Schematic representation of the mechanism of shape-memory effects for thermally induced shape-memory polymers (SMPs) based on a crystal-amorphous transition in a semicrystalline-based polymer network.
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Figure 1: Schematic representation of the mechanism of shape-memory effects for thermally induced shape-memory polymers (SMPs) based on a crystal-amorphous transition in a semicrystalline-based polymer network.

Mentions: Figure 1 shows the schematic images of thermally induced crystal/amorphous transition in SMPs. While the origin of the shape-memory effect in SMAs is the solid-phase transition between the austenite phase at higher temperature and the martensite phase at lower temperature, that in SMPs relies on the phase transformation of switching domains or segments, such as glass–rubber and/or crystal–amorphous transitions [30]. The most noteworthy and extensively researched group of SMPs is thermally induced SMPs. They are thermoplastic elastomers or thermosets that are programmed by mechanically deforming the shape of a polymer at a temperature that exceeds its glass transition temperature (Tg) or melting temperature (Tm). This deformed shape (or ‘temporary’ shape) can be fixed when the material is cooled below the Tg or Tm. If the polymer chains are chemically or physically cross-linked, the material returns to its original shape (or ‘permanent’ shape) by heating it above the Tg or Tm. During this process, an increase in entropy serves as the driving force for the material to recover its initial shape. Therefore, shape-memory effects of thermally induced SMPs can be precisely controlled by tailoring the nano-architectures of polymer networks such as crystallinity or crosslinking density. Such nano-architectonic approaches have enabled us to develop SMPs with a thermal switch at a biologically relevant temperature [31–34]. Moreover, recent studies have shown the successful memorization of ordered patterns with feature sizes on the submicron scale to create SMSs (figure 2) [35–37]. The SMSs can offer an elegant approach to fabricating cell culture substrates with dynamically tunable topographies for investigating cell mechanobiology. The area of cell mechanobiology has recently been the subject of active research because the cell–extracellular matrix (ECM) interactions are considered to be important extrinsic factors that regulate cell fate. The manipulation of topographical cues, therefore, has a strong potential as a strategy for stem cell engineering and regenerative medicine by mimicking changing physiological conditions during would healing, organogenesis, and cancer metastasis. In this review, different types of SMPs (especially thermally induced SMPs) are discussed on the basis of nanoarchitectures of polymer networks. In addition, recent progresses of SMPs in biotechnology and biomedicine are reviewed. Especially, this review focuses on the developments of SMSs with dynamically switchable topography to control cell–substrate interactions and to direct cell fate.


Shape-memory surfaces for cell mechanobiology
Schematic representation of the mechanism of shape-memory effects for thermally induced shape-memory polymers (SMPs) based on a crystal-amorphous transition in a semicrystalline-based polymer network.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036502&req=5

Figure 1: Schematic representation of the mechanism of shape-memory effects for thermally induced shape-memory polymers (SMPs) based on a crystal-amorphous transition in a semicrystalline-based polymer network.
Mentions: Figure 1 shows the schematic images of thermally induced crystal/amorphous transition in SMPs. While the origin of the shape-memory effect in SMAs is the solid-phase transition between the austenite phase at higher temperature and the martensite phase at lower temperature, that in SMPs relies on the phase transformation of switching domains or segments, such as glass–rubber and/or crystal–amorphous transitions [30]. The most noteworthy and extensively researched group of SMPs is thermally induced SMPs. They are thermoplastic elastomers or thermosets that are programmed by mechanically deforming the shape of a polymer at a temperature that exceeds its glass transition temperature (Tg) or melting temperature (Tm). This deformed shape (or ‘temporary’ shape) can be fixed when the material is cooled below the Tg or Tm. If the polymer chains are chemically or physically cross-linked, the material returns to its original shape (or ‘permanent’ shape) by heating it above the Tg or Tm. During this process, an increase in entropy serves as the driving force for the material to recover its initial shape. Therefore, shape-memory effects of thermally induced SMPs can be precisely controlled by tailoring the nano-architectures of polymer networks such as crystallinity or crosslinking density. Such nano-architectonic approaches have enabled us to develop SMPs with a thermal switch at a biologically relevant temperature [31–34]. Moreover, recent studies have shown the successful memorization of ordered patterns with feature sizes on the submicron scale to create SMSs (figure 2) [35–37]. The SMSs can offer an elegant approach to fabricating cell culture substrates with dynamically tunable topographies for investigating cell mechanobiology. The area of cell mechanobiology has recently been the subject of active research because the cell–extracellular matrix (ECM) interactions are considered to be important extrinsic factors that regulate cell fate. The manipulation of topographical cues, therefore, has a strong potential as a strategy for stem cell engineering and regenerative medicine by mimicking changing physiological conditions during would healing, organogenesis, and cancer metastasis. In this review, different types of SMPs (especially thermally induced SMPs) are discussed on the basis of nanoarchitectures of polymer networks. In addition, recent progresses of SMPs in biotechnology and biomedicine are reviewed. Especially, this review focuses on the developments of SMSs with dynamically switchable topography to control cell–substrate interactions and to direct cell fate.

View Article: PubMed Central - PubMed

ABSTRACT

Shape-memory polymers (SMPs) are a new class of smart materials, which have the capability to change from a temporary shape ‘A’ to a memorized permanent shape ‘B’ upon application of an external stimulus. In recent years, SMPs have attracted much attention from basic and fundamental research to industrial and practical applications due to the cheap and efficient alternative to well-known metallic shape-memory alloys. Since the shape-memory effect in SMPs is not related to a specific material property of single polymers, the control of nanoarchitecture of polymer networks is particularly important for the smart functions of SMPs. Such nanoarchitectonic approaches have enabled us to further create shape-memory surfaces (SMSs) with tunable surface topography at nano scale. The present review aims to bring together the exciting design of SMSs and the ever-expanding range of their uses as tools to control cell functions. The goal for these endeavors is to mimic the surrounding mechanical cues of extracellular environments which have been considered as critical parameters in cell fate determination. The untapped potential of SMSs makes them one of the most exciting interfaces of materials science and cell mechanobiology.

No MeSH data available.