University of Groningen

The effect of wettability and stiffness on stem behavior at bioinerfaces Kühn, Philipp Till

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Publication date: 2016

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Citation for published version (APA): Kühn, P. T. (2016). The effect of wettability and stiffness on stem cell behavior at bioinerfaces. Rijksuniversiteit Groningen.

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CHAPTER ONE

GENERAL INTRODUCTION

1 GENERAL INTRODUCTION

1.1. BIOINTERFACES

Continuous improvement of quality of life is one of the essential features of modern society. With increasing average age, our society faces a growing number of health related necessary improvements of this life quality. For that reason, a vast amount of research is conducted to find new with improved performance preferably at low costs. Upon use, these biomaterials come mostly in contact with biological compounds such as and DNA but also with tissues and cells.[1] Coming in contact with a , cells will interact with it on the biomaterials surface a so-called biointerface. At a biointerface, they react to proteins, which often adsorb spontaneously to an interface. This adsorption is dependent on the biomaterials surface properties which therefore indirectly influences cell behavior. Cells interacting with an interface be it with a surface or a 3D matrix is one of the fundamental processes in the fields of regenerative medicine, tissue-engineering.[2,3] Here the physical parameters of the biomaterial at the biointerface are of great relevance. It is known, that tissue cells adsorbed on a surface react to numerous physical parameters of the biomaterial, such as wettability, stiffness, topography and chemical surface functionality. Wettability and chemical functionality influence mostly the adsorbing proteins to which the cell responds.[4–7] Due to their importance many researchers investigate the response of cells adhering to surfaces with different physical properties.[7,8] The ultimate goal, to gain control over the biological systems by controlling physical parameters, can only be achieved by systematical investigation of these responses. For pursuing such systematical investigation, it is required to precisely control the physical properties at a biointerface. Biomaterials can cause foreign body responses like inflammation, necrosis or fibrosis when implanted in the body. Precisely engineered biointerfaces could help understanding the interactions of biomaterials and the body better, leading to the development of better biomaterials. Biointerfaces in the body can be of 2D and 3D nature. Where for a conventional bone implant the implants surface represents a typical 2D biointerface, cell laden injectable hydrogels for cartilage regeneration are an example for a 3D biointerface.[9] Developing new, smart biomaterials is a continuously ongoing process.[10,11] These materials have the potential of higher control over biological processes. The clinical application is a very time consuming and complicated process. Finding ways to use and improve the performance of materials already frequently used in medical applications is therefore a more downwards translational route of investigation. In this thesis, this approach is used to develop 2D and 3D interfaces.

1.2. 2-DIMENSIONAL SUBSTRATES

Physical properties at the biointerface can influence cellular behavior such as adhesion, spreading, migration, proliferation and differentiation.[5,12–14] The proper control over physical properties and the testing of cell behavior is much easier on 2D samples. Therefore, high-throughput screening approaches for in-vitro testing of cell responses towards certain parameters have been developed. These approaches use systematical changes in material composition[15] or topography.[16] The indicated methods allow time and cost efficient testing of a certain physical parameter towards cell behavior. The downside is, that numerous single samples are prepared, which is cost- and labor-

2 CHAPTER ONE intensive. Another approach is the use of surface gradients. A surface gradient is a surface, on which one parameter changes gradually from one side to the other. This allows systematical testing of a parameter using only one surface making it more cost and time efficient than individual samples (Figure 1a).

Figure 1: Schematic illustration of a 2-D surface gradient and the advantages over single sample measuring(a). Illustration of cellular responses to a physical parameter on a surface gradient(b).

These surface gradients can be produced changing different physical properties over this surface. This distinct parameter can then be tested towards cell response using only a single sample (Figure 1b). Where changing one parameter is already a huge improvement over separate samples, a two parameter gradient can give exponentially more information. In a double gradient approach, the influence of parameter combinations can be determined, which is not possible using a single surface gradient approach. Where the influence of one physical parameter was already shown, the combinatorial effect of two or more at the same time is still relatively unexplored (Figure 2).

Figure 2: Illustration showing possible combinations of physical properties of biomaterials for in vitro testing.

3 GENERAL INTRODUCTION

Since a biomaterial, or any material really, always consists of a distinct combination of parameters, the combinatorial effects of multiple physical parameters need to be investigated. Testing the influence of one parameter whilst keeping the other parameters constant grants only limited information. Studies looking at the combination of two different parameters using orthogonal double gradients have been published.[17–19] Here mostly chemical cues are incorporated rather than looking at two physical parameters. 2D biointerfaces are not only of big interest for screening of cell responses but also in terms of medical applications, where they are important as implant surfaces. Here it is obvious that the control over the properties is highly important, since it was found that these can influence cell behavior like adhesion proliferation and differentiation.[8,14,20–22] Understanding the influence of physical parameters of a 2D biointerface of implant materials could therefore directly improve the performance of implant materials with respect to e.g. minimizing the foreign body response.

1.3. 3-DIMENSIONAL MATRICES

To control the physical parameters of a biomaterial to gain control over cellular response is not only important on 2D substrates. Also in 3D networks these parameters play a crucial role and have been shown to influence cell behavior.[23,24] The natural environment of cells is 3D as cells generally are surrounded by and other cells. Controlling the physical parameters in three dimensions gives the opportunity to mimic the natural extracellular matrix. This allows to design materials with improved performance, because cells “feel” a familiar environment. In 3D, material properties are harder to control in a gradient fashion. Gradients in 3D are also used to investigate the cellular response towards a certain parameter. 3D matrices with gradually changing stiffness are already being used.[25,26] 3D gradients with a change in growth factor concentration also have been published, but have not been tested in combination with cells.[27] Besides the cell response, the physical parameters of biomaterials are also important in terms of their application. Different biomaterials can have contrasting purposes with the need of very different properties. It can be easily understood that the biomaterial for a bone replacement needs to fulfill different requirements than a facial implant. Gaining control over the physical properties of biomaterials therefore has a double function. Physical parameters not only have an influence on the stability of the material but can also be directly linked to their function. For the efficiency of cell laden hydrogels for wound dressing applications for instance, the diffusion of soluble factors through the material is of great importance. This diffusion can also be influenced by physical parameters of the material like porosity.[28,29] Therefore, controlling the physical properties of a biomaterial and consequently the biointerfaces of 2D and 3D materials is a crucial task in order to improve their performance. This can consequently greatly impact the field of and regenerative medicine.

4 CHAPTER ONE

1.4. AIM OF THIS THESIS

The general aim of this thesis is to develop new approaches to influence known materials to identify optimal physical parameters and parameter combinations at biointerfaces and how these will affect cellular behavior. It is important to carefully test the parameters of the biointerface towards cell response in a systematic way in order to yield strong conclusions from it. Therefore, the generation of systems which allow this kind of testing is the main goal of this thesis. Surface gradient testing devices, which are capable of elucidating effects of wettability, stiffness and their combination are developed and used for the 2D biointerface testing. In order for an efficient 3D testing and the possibility to change three parameters in independent directions, first attempts to manipulate stiffness in a 3D system are made. This material is further facilitated as potential wound healing material. At the end, findings and general conclusions are placed in perspective where system drawbacks are still eminent but great strides are expected to be made in the field of biointerfaces as initial findings presented in this thesis have enabled this. The idea of combining and systematically manipulating physical parameters of biomaterials to control cellular behavior will hopefully pave the road for the development of new biomaterials. Materials frequently used in the clinics are targeted together with innovative approaches. This hopefully facilitates a shorter route to actual clinical application.

5 GENERAL INTRODUCTION

LITERATURE

[1] R. Ogaki, M. Alexander, P. Kingshott, Mater. Today 2010, 13, 22. [2] K. G. I. Nilsson, C.-F. Mandenius, Bio/Technology 1994, 12, 1376. [3] D. W. Hutmacher, Biomaterials 2000, 21, 2529. [4] E. S. Place, N. D. Evans, M. M. Stevens, Nat. Mater. 2009, 8, 457. [5] M. M. Stevens, J. H. George, Science 2005, 310, 1135. [6] B. J. H. Jansen, C. Gilissen, H. Roelofs, A. Schaap-Oziemlak, J. A. Veltman, R. A. P. Raymakers, J. H. Jansen, G. Kögler, C. G. Figdor, R. Torensma, G. J. Adema, Stem Cells Dev. 2010, 19, 481. [7] A. Higuchi, Q.-D. Ling, Y. Chang, S.-T. Hsu, A. Umezawa, Chem. Rev. 2013, 113, 3297. [8] D. P. Dowling, I. S. Miller, M. Ardhaoui, W. M. Gallagher, J. Biomater. Appl. 2011, 26, 327. [9] F. Chen, S. Yu, B. Liu, Y. Ni, C. Yu, Y. Su, X. Zhu, X. Yu, Y. Zhou, D. Yan, Sci. Rep. 2016, 6, 20014. [10] L. L. Hench, J. M. Polak, Science 2002, 295, 1014. [11] R. J. Narayan, Philos. Trans. A. Math. Phys. Eng. Sci. 2010, 368, 1831. [12] R. Ayala, C. Zhang, D. Yang, Y. Hwang, A. Aung, S. S. Shroff, F. T. Arce, R. Lal, G. Arya, S. Varghese, Biomaterials 2011, 32, 3700. [13] D. E. Discher, D. J. Mooney, P. W. Zandstra, Science 2009, 324, 1673. [14] D. E. Discher, P. Janmey, Y.-L. Wang, Science (80-. ). 2005, 310, 1139. [15] Y. Mei, K. Saha, S. R. Bogatyrev, J. Yang, A. L. Hook, Z. I. Kalcioglu, S.-W. Cho, M. Mitalipova, N. Pyzocha, F. Rojas, K. J. Van Vliet, M. C. Davies, M. R. Alexander, R. Langer, R. Jaenisch, D. G. Anderson, Nat. Mater. 2010, 9, 768. [16] M. Hulsman, F. Hulshof, H. Unadkat, B. Papenburg, D. Stamatialis, R. Truckenmüller, C. van Blitterswijk, J. de Boer, M. J. T. Reinders, Acta Biomater. 2015, 15, 29. [17] A. D. Rape, M. Zibinsky, N. Murthy, S. Kumar, Nat. Commun. 2015, 6, 8129. [18] L. R. Clements, P. Y. Wang, W. B. Tsai, H. Thissen, N. H. Voelcker, Lab Chip 2012, 12, 1480. [19] R. R. Bhat, M. R. Tomlinson, J. Genzer, J. Polym. Sci. Part B Polym. Phys. 2005, 43, 3384. [20] A. J. Engler, S. Sen, H. L. Sweeney, D. E. Discher, Cell 2006, 126, 677. [21] A. Higuchi, Q. D. Ling, Y. Chang, S. T. Hsu, A. Umezawa, Chem Rev 2013, 113, 3297. [22] M. A. Bucaro, Y. Vasquez, B. D. Hatton, J. Aizenberg, ACS Nano 2012, 6, 6222. [23] D. S. W. Benoit, M. P. Schwartz, A. R. Durney, K. S. Anseth, Nat. Mater. 2008, 7, 816. [24] A. Banerjee, M. Arha, S. Choudhary, R. S. Ashton, S. R. Bhatia, D. V Schaffer, R. S. Kane, Biomaterials 2009, 30, 4695. [25] R. S. Stowers, S. C. Allen, L. J. Suggs, Proc. Natl. Acad. Sci. 2015, 112, 1953. [26] H. G. Sundararaghavan, G. A. Monteiro, B. L. Firestein, D. I. Shreiber, Biotechnol. Bioeng. 2009, 102, 632. [27] S. H. Oh, T. H. Kim, J. H. Lee, Biomaterials 2011, 32, 8254. [28] G. Gainza, S. Villullas, J. L. Pedraz, R. M. Hernandez, M. Igartua, Nanomedicine , Biol. Med. 2015, 11, 1551. [29] T. Billiet, E. Gevaert, T. De Schryver, M. Cornelissen, P. Dubruel, Biomaterials 2014, 35, 49.

6 CHAPTER ONE

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