Active biomaterials/scaffolds for stem cell-based soft tissue engineering (in a nutshell )

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1 Active biomaterials/scaffolds for stem cell-based soft tissue engineering (in a nutshell ) Emanuele Giordano Responsabile Lab ICM BioEngLab DEI CIRI SdV-TS Università di Bologna emanuele.giordano@unibo.it

2 Organ regeneration He bound devious Prometheus with inescapable harsh bonds, fastened through the middle of a column, and he inflicted on him a long-winged eagle, which ate his immortal Parti Biologiche liver, Standard but it grew as much in all at night as the long-winged bird would eat all day. Θεογονία (Theogonía); Hesiod (8 th 7t h century BC) describing the origins and genealogies of the Greek gods.

3 The promise of stem cell research

4 The promise of stem cell research May we obtain complex SCs differentiation by growing them in 2D polypropylene culture plates, even in presence of appropriate biochemical cues? A rhetorical question is a figure of speech in the form of a question that is asked to make a point rather than to elicit an answer

5 Substrate stiffness directs stem cell differentiation

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7 Mechano-sensitive pathways convert biophysical cues into biochemical signals that commit the cell to a specific lineage

8 Engineering stem cell microenvironment will benefit their proliferation and differentiation into cells of interest for biomedical and clinical applications A variety of materials have been developed to match the diverse elasticity of tissues in vivo. Softer Harder

9 Engineering stem cell microenvironment will benefit their proliferation and differentiation into cells of interest for biomedical and clinical applications A variety of materials have been developed to match the diverse elasticity of tissues in vivo. Artificial biopolymers presently used in tissue engineering are extremely stiff. As an example, polylactic acid (PLA), which is FDA-approved for implant into humans, has a bulk elasticity of E ~ 1 GPa. Thus engineering of soft tissue replacements needs to explore biopolymers softer than those presently available.

10 How to engineering biopolymers softer than those presently available? A material-based approach Introduction of etheroatoms along the polymeric chain of aliphatic polyesters allows to modulate the ability to crystallize of the resulting polymers, and, above all, to enhance their flexibility and surface hydrophilicity. Gualandi C. et al., Soft Matter, 2012, 8, Gigli M. et al., Green Chem., 2012, 14, Gigli M. et al., React. Funct. Polym., 2012, 72, Gigli M. et al., React. Funct. Polym., 2013, 73, Gigli M. et al., Polym. Degrad. Stab., 2013, 98, Gigli M. et al., Ind. Eng. Chem. Res., 2013, 52,

11 How to engineering biopolymers softer than those presently available? A material-based approach Multiblock co-polymerization of aliphatic polyesters, where different block lengths allows to modulate the ability to crystallize of the resulting polymers, and, above all, to enhance their flexibility and surface hydrophilicity. Block length controls the polymer crystallinity, the thermal and mechanical properties, the wettability and the degradation rate. The copolymers display different stiffnesses, mainly depending on the crystallinity degree and macromolecular chain flexibility, a tunable range of degradation rates, and different surface hydrophilicity.

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13 Biocompatibility assays: - showed the absence of potentially cytotoxic products released into the culture medium by the investigated samples.

14 Biocompatibility assays: - demonstrated that substrates support a physical environment where cells can adhere and proliferate.

15 Biocompatibility assays: - demonstrated that substrates offer aphysical environment where cells can receive definite biophysical cues.

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17 Native extracellular matrix (ECM) presents various geometrically defined physical boundaries, such as fibers that support cells and regulate their function.

18 How to engineering biopolymers closer to native extracellular matrix than those presently available? A micro/nano fabrication-based approach Emerging micro- and/or nano-scale engineering technologies offer unprecedented opportunities for the creation of cell microenvironment in vitro that recapitulates some crucial cues in vivo, such as: - surface topography, - dynamic mechanical microenvironment, - spatiotemporal chemical gradients, - 3D environment. Here summarized three examples of strategies that have been used to these aims.

19 How to engineering biopolymers closer to native extracellular matrix than those presently available? A micro/nano fabrication-based approach Emerging micro- and/or nano-scale engineering technologies offer unprecedented opportunities for the creation of cell microenvironment in vitro that recapitulates some crucial cues in vivo, such as: - surface topography, - dynamic mechanical microenvironment, - spatiotemporal chemical gradients, - 3D environment.

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24 How to engineering biopolymers closer to native extracellular matrix than those presently available? A micro/nano fabrication-based approach Emerging micro- and/or nano-scale engineering technologies offer unprecedented opportunities for the creation of cell microenvironment in vitro that recapitulates some crucial cues in vivo, such as: - surface topography, - dynamic mechanical microenvironment, - spatiotemporal chemical gradients, - 3D environment.

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29 How to engineering biopolymers closer to native extracellular matrix than those presently available? A micro/nano fabrication-based approach Emerging micro- and/or nano-scale engineering technologies offer unprecedented opportunities for the creation of cell microenvironment in vitro that recapitulates some crucial cues in vivo, such as: - surface topography, - dynamic mechanical microenvironment, - spatiotemporal chemical gradients, - 3D environment.

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32 How to engineering biopolymers closer to native extracellular matrix than those presently available? A micro/nano fabrication-based approach Emerging micro- and/or nano-scale engineering technologies offer unprecedented opportunities for the creation of cell microenvironment in vitro that recapitulates some crucial cues in vivo, such as: - surface topography, - dynamic mechanical microenvironment, - spatiotemporal chemical gradients, - 3D environment.

33 Native extracellular matrix (ECM) presents various geometrically defined physical boundaries, such as fibers that support cells and regulate their function.

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36 Mechanical forces play significant developmental roles in native and engineered tissues.

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42 Mandatory specifications for tissue engineering templates The material should be capable of recapitulating the architecture of the niche of the target cells. Since the cell niche is changeable over time, the material should be capable of adapting to the constantly changing microenvironment. The material should have elastic properties, particularly stiffness, which favor mechanical signaling to the target cells, to optimize differentiation, proliferation, and gene expression. The material should have optimal surface or interfacial energy characteristics to facilitate cell adhesion and function. The material should be capable of orchestrating molecular signaling to the target cells, either by directing endogenous molecules or delivering exogenous molecules. The material should be of a physical form that provides the appropriate shape and size to the regenerated tissue. The material should be capable of forming into an architecture that optimizes cell, nutrient, gas, and biomolecule transport, either ex vivo or in vivo or both, and facilitates blood vessel and nerve 45/46 development.

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46 Giovanna Della Porta

47 Marco Govoni

48 Active biomaterials/scaffolds for stem cell-based soft tissue engineering (in a nutshell ) Emanuele Giordano Lab ICM BioEngLab DEI CIRI SdV-TS Università di Bologna emanuele.giordano@unibo.it