Tissue engineering is a rapidly growing field which aims to produce models for skin, heart, bone and eventually whole organs. In a first approach the creation of tissue models for pharmacological research is envisioned, with a view to substantially reducing animal trials. Recent progress in biofabrication has enabled the manufacturing of 3D tissue models through layer by layer deposition of cell-laden hydrogel onto scaffolds acting as cell culture support structures (Moroni et al., 2018).
Similarly, paper-based cell culture supports have been used for tissue engineering (Chen et al., 2015; Juvonen et al., 2013; Ng et al., 2017; Park et al., 2014) due to their capacity to wick liquids by capillarity, their porous matrix enabling the transport of nutrients and oxygen (Chen et al., 2015; Deka et al., 2020), as well as the availability of cell migration paths along the fibers (Mosadegh et al., 2014; Mosadegh et al., 2015; Ng et al., 2017; Wang et al., 2015). Moreover, paper scaffolds are foldable, mechanically flexible, easy to sterilize (Lantigua et al., 2017) and can be produced in large quantities at low cost (Juvonen et al., 2013) compared to materials such as polymers, glass and metals (Juvonen et al., 2013; Lantigua et al., 2017). Different cellulosic materials have been used for paper based scaffolds (Lantigua et al., 2017), for example, print paper from wood pulp has been used by Wang et al. to support beating cardiac tissue (Wang et al., 2015), cotton fibers have been employed to support cells from tissues such as cardiomyocytes, human breast cancer and other human cells (Ng et al., 2017) and lyocell has been used as a scaffold for cartilage tissue engineering (Müller et al., 2006). Recently, cellulose based paper has been used as a support in biofabrication (Ng et al., 2017) such as bioprinting (Derda et al., 2011; Lantigua et al., 2017; Mosadegh et al., 2014; Ng et al., 2017; Wang et al., 2015).
A desired feature of cell culture scaffolds is the availability of alignment cues, both to guide and promote cell maturation (Parrag et al., 2012; Wanjare et al., 2017). Alignment cues for neuronal cell cultures have been achieved by several techniques such as electrospinning (Rayatpisheh et al., 2014; Tseng et al., 2013; Whited & Rylander, 2014) or casting hydrogels onto molds containing nanometer sized grooves (Tsai et al., 2017). Similarly, anisotropic alignment structures for cardiac cell cultures act as guides for directional muscle fiber growth and differentiation, resulting in directional and higher overall contraction forces (Kharaziha et al., 2013; Radisic et al., 2004; Wanjare et al., 2017). Cellulose fibers with a specific diameter might also function as alignment cues. Cell culture paper scaffolds with such intrinsic alignment cues would not require post fabrication steps and could thus easily mass be produced. However, almost all paper sheets made at lab, pilot and industrial scale have a mandatory fiber alignment given by the machine direction (MD) and the cross direction (CD) related forces involved in the elaboration process (Belle & Odermatt, 2016; Kröling et al., 2014). To achieve cellulose cell culture scaffolds with oriented fibers and tailored fiber diameters, current fabrication procedures need to be adapted.
Successful cell differentiation and maturation often depend on the mechanical characteristics of the supporting cell scaffold (Moroni et al., 2018). By introducing crease patterns, the directional elongation potential and cross lateral stability of paper scaffolds can be adapted to match the desired tissue properties. Origami techniques have been used to introduce tailored mechanical properties in cellulose scaffolds for engineered tissue (Li et al., 2020), drug delivery and catheters (Ahmed et al., 2020). Additional benefits of using origami techniques are the low material costs, scalability, versatility and the possibility to fold planar origami substrates into complex volumetric structures such as heart ventricles (Ahmed et al., 2020). Cellulose scaffold manufacturing techniques able to introduce origami crease pattern in a cost-effective manner would therefore be desirable.
This work aims to realize current cellulose based cell culture scaffolds suitable for a wide range of tissues. It focuses on the cost-effective manufacturing of biocompatible and cell culture resistant cellulose scaffolds with fiber dimensions enabling aligned cell growth, fiber alignment for directionally tailored mechanical properties as well as in-process formation of origami crease patterns. This research is part of a larger project whose objective is the combination of cellulose scaffolds with layers of cardiac and vascular forming cells, enabling the engineering of cardiac tissue for miniaturized heart models and cardiac patches for regenerative surgery.