Hydrogels with reversible mechanical properties for directing cell function
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1
University of Liverpool, School of Engineering, United Kingdom
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2
University of Manchester, Manchester Institute of Biotechnology, United Kingdom
Introduction: Hydrogels with non-invasive tuneable reversible properties are an extremely attractive tool for developing materials that can control cell responses. The development of smart materials that can change the mechanical properties of an environment and change the stimuli presented to the cells at different locations within a scaffold, offer a physical means to direct cells. Here we present a photocontrollable biocompatible polymer substrate where the matrix properties can be altered between two different states, at defined locations, thus allowing the mechanical properties (i.e. stiffness) to be altered whilst maintaining the chemical composition of the substrate.
Materials and Methods: The hydrogel was coated with fibronectin (FN) (Sigma, F1141, 50 µg/mL) prior to cell culture. The process used to induce changes in stiffness did not affect the adsorbed fibronectin layer, therefore only the stiffness of the gel was changed using photo-irradiation and not the composition of the surface. Materials were cultured in direct contact with fibroblasts (ATCC, CRL-1658™) and human MSC (Lonza UK) in standardised culture conditions for up to 72 h. The cytotoxicity of the gels was determined using CyQUANT®, cell adhesion and cell migration were analysed by staining after 24, 72 h culture and visluaisation using fluorescent microscopy.
Results and Discussion: It has been experimentally evidenced that cells exhibited high viability on FN coated photo-switchable surfaces throughout the culture periods. Furthermore, after photoirradiation of a portion of the hydrogel surface, seeded cells were observed to migrate from modified surface that had a stiffness at ~2 kPa towards the non-modified area of the material surface that had a higher stiffness (i.e. ~8 kPa) within 72 h. In addition to inducing cell migration, changing the specific mechanical properties of the gels at specific locations resulted in a distinct change in cell morphology, proving that the cells responded to the induced changes in mechanical properties (Figure 1).
Figure 1. Fluorescent images of fibroblasts on hydrogels at different locations of the substrate. Cell number is reduced on the modified area (left, ~2 kPa) than on the non-modified area (right, ~8 kPa). Cells showed different shapes on different areas, rounded on the modified area (~2 kPa) and were more spread on the non-modified area (~8 kPa). Nuclei and cell membrane were stained (Vybrant® DiD and DAPI).
Conclusion: In conclusion, it has been demonstrated that hydrogels can be fabricated that can reversibly alter their mechanical properties using photo-irradiation. In vitro cell culture on these materials demonstrated that the material was not cytotoxic up to 72 h and it was possible to modulate cell behaviour through in situ light-induced stiffness changes on the gel. The stiffness range of the material could be a good basis for the investigation of neuronal stem cells (NSCs) in the study of neurological conditions such as Parkinson’s diseases and/or Alzheimer’s. The desired outcome is to efficiently target the injured human tissue in order to heal the wound or treat disease with degradable hydrogels. Furthermore, this material can be used in combination with a number of technologies such as nanoscale printing or photolithography in order to address how and to what extent cells sense biochemical and mechanical features in their environment.
Keywords:
Hydrogel,
Biocompatibility,
Cell response,
Smart material
Conference:
10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.
Presentation Type:
Poster
Topic:
Cellular migration and biomaterials
Citation:
Lee
I,
Booth
A,
Curran
JM,
Hunt
JA and
Wong
L
(2016). Hydrogels with reversible mechanical properties for directing cell function.
Front. Bioeng. Biotechnol.
Conference Abstract:
10th World Biomaterials Congress.
doi: 10.3389/conf.FBIOE.2016.01.00974
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Received:
27 Mar 2016;
Published Online:
30 Mar 2016.