Bioactive surfaces from seaweed-derived alginates for the cultivation of human stem cells

Abstract

Nowadays, modern approaches in tissue engineering include the combination of therapeutic relevant cells with high quality, biocompatible biomaterials. The resulting cellularized scaffolds are of great interest for several pharmaceutical applications such as drug screening/discovery, disease modeling, and toxicity testing. In addition, the introduction of human-induced pluripotent stem cells (hiPSCs) further increased the importance and the potential of tissue engineering not only for the pharmaceutical industry, but also for future therapeutic applications. Artificial microenvironments of hiPSCs comprise combinations of adhesive proteins and are particularly influenced by mechanical properties of the growth surface. The increasing focus on mechanical properties and the ability to adjust them propose alginate hydrogels as suitable candidates for engineered scaffolds. Ultra-pure alginates, however, are bioinert and require modifications for bioactivation. In this study, we present two modifications of alginate hydrogels based on direct covalent coupling of collagen I and coupling of a special linker molecule with subsequent Matrigel coating. We were able to demonstrate the successful adhesion and proliferation of hiPSCs on these linkermodified alginates. The developed modifications are particularly applicable for planar as well as spherical hydrogel surfaces. In this context, a scalable adherent suspension culture on alginate microcarriers could be established. Our data further indicate that larger alginate microcarriers modified with collagen I is less susceptible for agglomeration compared to small microcarriers. The obtained results indicate these modifications as suitable for both adhesion and cultivation of human stem cells such as human mesenchymal stem cells or hiPSCs.

Tyramine‐conjugated alginate hydrogels as a platform for bioactive scaffolds

“…Alginate‐based hydrogels represent promising biomaterials due to their biocompatibility and adjustable mechanical and porous characteristics . As native alginate inhibits cell adhesion, functionalization strategies are needed to address cell–matrix contacts.…”

“…To meet the requirements of the complex, native cell environment soft and porous materials with adjustable mechanical properties are needed. Here, alginate as a widely applied biomaterial in tissue engineering represents a promising cell microenvironment, as this biocompatible polymer is able to form hydrogels with adaptable mechanical characteristics and porosities . However, native alginate inhibits cell adhesion due to its repelling anionic surface and lacking cell interaction sites .…”

Poly(amidoamine)-alginate hydrogels: directing the behavior of mesenchymal stem cells with charged hydrogel surfaces

“…The surface modification was carried out in a two-step process. First, the alginate’s carboxylic groups were activated by aqueous carbodiimide chemistry resulting in the conjugation of N-hydroxysuccinimide (NHS) as described previously [ 20 ]. Subsequently, obtained alginate-NHS ester (ANHS) were coupled with PAMAM dendrimers constituted of an ethylenediamine core as generation 3.0 (PAMAM G 3.0, Sigma-Aldrich, Taufkirchen, Germany) in various quantities (1.6, 3.2, 32, 324 and 3245 nmol PAMAM/cm 2 surface area) for 24 h at RT.…”

“…On that account, we prepared specific surface charges adjusted by the conjugation of charged poly(amidoamine) (PAMAM) to alginate-based hydrogels. Alginate as a polysaccharide extracted from the cell wall of marine seaweed is one of the most applied biomaterials in biomedical sciences [ 17 – 20 ]. With its biocompatibility, its ability to form a hydrogel under mild conditions as well as adjustable mechanical and porous characteristics, alginate asserts itself as a widely applied biomaterial in tissue engineering [ 19 – 21 ] and drug delivery [ 22 ].…”

“…Since the alginate surface is negatively charged, protein adsorption was found to be low resulting in an inhibition of cell adhesion favorable for immunoisolations [ 23 ]. To address cell-matrix contacts, functional groups of the alginate structure can be modified in a versatile manner [ 20 , 24 ]. In this study, we used highly positively charged PAMAM dendrimers, which are mainly applied as vehicles in drug delivery [ 25 ] and gene delivery [ 26 ].…”