Three-Dimensional Printing Using a Maize Protein: Zein-Based Inks in Biomedical Applications.

The use of three-dimensional (3D) printing for biomedical applications has expanded exponentially in recent years. However, the current portfolio of 3D printable inks is still limited. For instance, only few protein matrices have been explored as printing/bioprinting materials. Here, we introduce the use of zein, the primary constitutive protein in maize seeds, as a 3D printable material. Zein-based inks were prepared by dissolving commercial zein powder in ethanol with or without polyethylene glycol (PEG400) as a plasticizer. The rheological characteristics of our materials, studied during 21 days of aging/maturation, showed an increase in the apparent viscosity as a function of time in all formulations. The addition of PEG400 decreased the apparent viscosity. Inks with and without PEG400 and at different maturation times were tested for printability in a BioX bioprinter. We optimized the 3D printing parameters for each ink formulation in terms of extrusion pressure and linear printing velocity. Higher fidelity structures were obtained with inks that had maturation times of 10 to 14 days. We present different proof-of-concept experiments to demonstrate the versatility of the engineered zein inks for diverse biomedical applications. These include printing of complex and/or free-standing 3D structures, tablets for controlled drug release, and scaffolds for cell culture.

Multifunctional Biomaterials: Combining Material Modification Strategies for Engineering of Cell-Contacting Surfaces.

In the human body, cells in a tissue are exposed to signals derived from their specific extracellular matrix (ECM), such as architectural structure, mechanical properties, and chemical composition (proteins, growth factors). Research on biomaterials in tissue engineering and regenerative medicine aims to recreate such stimuli using engineered materials to induce a specific response of cells at the interface. Although traditional biomaterials design has been mostly limited to varying individual signals, increasing interest has arisen on combining several features in recent years to improve the mimicry of extracellular matrix properties. Tremendous progress in combinatorial surface modification exploiting, for example, topographical features or variations in mechanics combined with biochemical cues has enabled the identification of their key regulatory characteristics on various cell fate decisions. Gradients especially facilitated such research by enabling the investigation of combined continuous changes of different signals. Despite unravelling important synergies for cellular responses, challenges arise in terms of fabrication and characterization of multifunctional engineered materials. This review summarizes recent work on combinatorial surface modifications that aim to control biological responses. Modification and characterization methods for enhanced control over multifunctional material properties are highlighted and discussed. Thereby, this review deepens the understanding and knowledge of biomimetic combinatorial material modification, their challenges but especially their potential.

Design of a Versatile Sample Holder for Facile Culture of Cells on Electrospun Membranes or Thin Polymer Films Under Flow Conditions.

Endothelial cell culture under flow, to mimic physiological conditions within blood vessels, has gained particular attention for the formation of a homogeneous endothelium in vitro. Here, we report on the design of a setup for simultaneous culture of up to nine electrospun membranes or thin polymer films in custom-made holders under flow on an orbital shaker. The versatile design of the device allows for the use of electrospun membranes/polymer films of choice and subsequent analysis with commonly used methods such as immunofluorescence or scanning electron microscopy.

Controlling the surface structure of electrospun fibers: Effect on endothelial cells and blood coagulation.

The influence of nano- or micron-sized structures on polymer films as well as the impact of fiber diameter of electrospun membranes on endothelial cell (EC) and blood response has been studied for vascular tissue engineering applications. However, the influence of surface structures on micron-sized fibers on endothelial cells and blood interaction is currently not known. In this work, electrospun membranes with distinct fiber surface structures were designed to study their influence on the endothelial cell viability and thrombogenicity. The thermodynamically derived Hansen-solubility-parameters model accurately predicted the formation of solvent dependent fiber surface structured poly(caprolactone) membranes. The electrospun membranes composed of microfibers (MF) or structured MF were of similar fiber diameter, macroscopic roughness, wettability, and elastic modulus. In vitro evaluation with ECs demonstrated that cell proliferation and morphology were not affected by the fiber surface structure. Similarly, investigating the blood response to the fiber meshes showed comparable fibrin network formation and platelet activation on MF and structured MF. Even though the presented results provide evidence that surface structures on MF appear neither to affect EC viability nor blood coagulation, they shed light on the complexity and challenges when studying biology-material interactions. They thereby contribute to the understanding of EC and blood-material interaction on electrospun membranes.