Biomimetic and stimuli-responsive cell-material interfaces are actively being developed to study and control various cell-dynamics phenomena. Since cells naturally reside in the highly dynamic and complex environment of the extracellular matrix, attempts are being made to replicate these conditions in synthetic biomaterials. Supramolecular chemistry, dealing with noncovalent interactions, has recently provided possibilities to incorporate such dynamicity and responsiveness in various types of architectures. Using a cucurbit[8]uril-based host–guest system, we have successfully established a dynamic and electrochemically responsive interface for the display of the integrin-specific ligand, Arg-Gly-Asp (RGD), to promote cell adhesion. Due to the weak nature of the noncovalent forces by which the components at the interface are held together, we expected that cell adhesion would also be weaker in comparison to traditional interfaces where ligands are usually immobilized by covalent linkages. To assess the stability and limitations of our noncovalent interfaces, we performed single-cell force spectroscopy studies using fluid force microscopy. This technique enabled us to measure rupture forces of multiple cells that were allowed to adhere for several hours on individual substrates. We found that the rupture forces of cells adhered to both the noncovalent and covalent interfaces were nearly identical for up to several hours. We have analyzed and elucidated the reasons behind this result as a combination of factors including the weak rupture force between linear Arg-Gly-Asp and integrin, high surface density of the ligand, and increase in effective concentration of the supramolecular components under spread cells. These characteristics enable the construction of highly dynamic biointerfaces without compromising cell-adhesive properties.

This study presents the effect of external electric current on the cell adhesive and mechanical properties of the C2C12 mouse myoblast cell line. Changes in cell morphology, viability, cytoskeleton, and focal adhesion structure were studied by standard staining protocols, while single-cell force spectroscopy based on the fluidic force microscopy technology provided a rapid, serial quantification and detailed analysis of cell adhesion and its dynamics. The setup allowed measurements of adhesion forces up to the N range, and total detachment distances over 40 m. Force-distance curves have been fitted with a simple elastic model including a cell detachment protocol in order to estimate the Young's modulus of the cells, as well as to reveal changes in the dynamic properties as functions of the applied current dose. While the cell spreading area decreased monotonously with increasing current doses, small current doses resulted only in differences related to cellelasticity.Current doses above 11 As/m2, however, initiated more drastic changes in cell morphology, viability, cellular structure, as well as in properties related to cell adhesion. The observed differences, eventually leading to cell death toward higher doses, might originate from both the decrease in pH and the generation of reactive oxygen species. This study presents the effect of external electric current on the cell adhesive and mechanical properties of the C2C12 mouse myoblast cell line. Changes in cell morphology, viability, cytoskeleton, and focal adhesion structure were studied by standard staining protocols, while single-cell force spectroscopy based on the fluidic force microscopy technology provided a rapid, serial quantification and detailed analysis of cell adhesion and its dynamics. The setup allowed measurements of adhesion forces up to the lN range, and total detachment distances over 40 lm. Force-distance curves have been fitted with a simple elastic model including a cell detachment protocol in order to estimate the Young's modulus of the cells, as well as to reveal changes in the dynamic properties as functions of the applied current dose. While the cell spreading area decreased monotonously with increasing current doses, small current doses resulted only in differences related to cell elasticity. Current doses above 11 As/m 2 , however, initiated more drastic changes in cell morphology, viability, cellular structure, as well as in properties related to cell adhesion. The observed differences, eventually leading to cell death toward higher doses, might originate from both the decrease in pH and the generation of reactive oxygen species.

Damage to the nervous system can be caused by several types of insults, and it always has a great effect on the life of an individual. Due to the limited availability of neural transplants, alternative approaches for neural regeneration must be developed. Stem cells have a great potential to support neuronal regeneration. Human adipose-derived stem cells (hADSCs) have gained increasing interest in the fields of regenerative medicine due to their multilineage potential and easy harvest compared to other stem cells. In this study, we present a growth factor-free method for the differentiation of hADSCs toward neuron-like cells. We investigated the effect of electric current and copper on neuronal differentiation. We analyzed the morphological changes, the mRNA and protein expression levels in the stimulated cells and showed that the combination of current and copper induces stem cell differentiation toward the neuronal lineage with elongation of the cells and the upregulation of neuron-specific genes and proteins. The induction of the neuronal differentiation of hADSCs by electric field and copper may offer a novel approach for stem cell differentiation and may be a useful tool for safe stem cell-based therapeutic applications. Abstract and key termsDamage to the nervous system can be caused by several types of insults, and it always has a great effect on the life of an individual. Due to the limited availability of neural transplants, alternative approaches for neural regeneration must be developed. Stem cells have a great potential to support neuronal regeneration.Human adipose-derived stem cells (hADSCs) have gained increasing interest in the fields of regenerative medicine due to their multilineage potential and easy harvest compared to other stem cells. In this study, we present a growth factor-free method for the differentiation of hADSCs toward neuron-like cells. We investigated the effect of electric current and copper on neuronal differentiation. We analyzed the morphological changes, the mRNA and protein expression levels in the stimulated cells and showed that the combination of current and copper induces stem cell differentiation toward the neuronal lineage with elongation of the cells and the upregulation of neuron-specific genes and proteins. The induction of the neuronal differentiation of hADSCs by electric field and copper may offer a novel approach for stem cell differentiation and may be a useful tool for safe stem cell-based therapeutic applications.

Fabrication of more complex tissue-engineered structures, resembling the tissues and organs in vivo requires combining more than one cell type within the same construct. This can be achieved by designing and fabricating complex scaffolds with asymmetric properties but controlled arrangement of cells within the scaffold could also be realized by using electric current. External electric currents are able to modify cell adhesion, orientation and migration and this can be used for influencing cell location within a scaffold. In this paper we studied the effect of an electric current on cell migration and adhesion into a three-dimensional scaffold through a conductive mesh.

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