Three-dimensional Nanofiber Network Research Articles

Self-assembled, photoluminescent peptide hydrogel as a versatile platform for enzyme-based optical biosensors

A self-assembled peptide hydrogel consisting of Fmoc-diphenylalanine has been employed as a biosensing platform through the encapsulation of enzyme bioreceptors (e.g., glucose oxidase or horseradish peroxidase) and fluorescent reporters (e.g., CdTe and CdSe quantum dots). Enzymes and quantum dots (QDs) were physically immobilized within the hydrogel matrix in situ in a single step by simply mixing aqueous solution containing QDs and enzymes with monomeric peptide (Fmoc-diphenylalanine) solution. By using atomic force microscopy and scanning transmission electron microscopy, we observed that the self-assembled peptide hydrogel had a three-dimensional network of nanofibers (with a diameter of approximately 70–90 nm) that physically hybridized with QDs and encapsulated enzyme bioreceptors with a minimal leakage. We successfully applied the peptide hydrogel to the detection of analytes such as glucose and toxic phenolic compounds by using a photoluminescence quenching of the hybridized QDs. The Michaelis–Menten constant ( K M) of the photoluminescent peptide hydrogel was found to be 3.12 mM (GOx for glucose) and 0.82 mM (HRP for hydroquinone), respectively, which were much lower than those of conventional gel materials. These results suggest that the peptide hydrogel is an alternative optical biosensing platform with practical advantages such as simple fabrication via self-assembly, efficient diffusion of target analytes, and high encapsulation efficiencies for fluorescent reporters and bioreceptors.

White biotechnology for cellulose manufacturing—The HoLiR concept

A variety of approaches are available for generation of bacteria-produced nanocellulose (BNC) in different forms. BNC production under static cultivation conditions usually results in fleeces or foils, characterized by a homogeneous, three-dimensional network of nanofibers and a uniform surface. However, under static cultivation conditions in batch vessels, the widths and the lengths of the BNC sheets cultured are determined by the dimensions of the culture vessel. In this contribution, a novel, efficient process for a (semi-)continuous cultivation of planar BNC fleeces and foils with a freely selectable length and an adjustable height is presented. By means of comprehensive investigations, the comparability of the BNC harvested to that gained from static cultivation under batch conditions is demonstrated. A first estimation of the production costs further shows that this type of processing allows for significant cost reductions compared to static cultivation of BNC in Erlenmeyer flasks.

Proliferation and differentiation of mesenchymal stem cells using self-assembled peptide amphiphile nanofibers

The objective of this study is to enhance the proliferation and differentiation of mesenchymal stem cells (MSC) in nanodimensional scaffolds. The proliferation and differentiation of MSC was investigated in a three-dimensional network of nanofibers formed by self-assembly of peptide amphiphile (PA) molecules. PA was synthesized by standard solid phase chemistry that ends with the alkylation of the NH2 terminus of the peptide. The sequence of arginine–glycine–aspartic acid was included in the peptide design as well. A three-dimensional network of nanofibers was formed by mixing MSC suspensions in media with dilute aqueous solution of PA. The attachment, proliferation and osteogenic differentiation of MSC were influenced by the self-assembled PA nanofibers as the cell scaffold and the values were significantly high compared with those in the static culture. The alkaline phosphatase activity and osteocalcin content of MSC cultured in the PA nanofibers significantly increased compared with the static culture method. It may be concluded that PA nanofibers enable MSC to positively improve the proliferation and differentiation extent.

Self-assembling peptide amphiphile nanofiber matrices for cell entrapment

We have developed a class of peptide amphiphile (PA) molecules that self-assemble into three-dimensional nanofiber networks under physiological conditions in the presence of polyvalent metal ions. The assembly can be triggered by adding PA solutions to cell culture media or other synthetic physiological fluids containing polyvalent metal ions. When the fluids contain suspended cells, PA self-assembly entraps cells in the nanofibrillar matrix, and the cells survive in culture for at least three weeks. We also show that entrapment does not arrest cell proliferation and motility. Biochemical and ultrastructural analysis by electron microscopy indicate that entrapped cells internalize the nanofibers and possibly utilize PA molecules in their metabolic pathways. These results demonstrate that PA nanofibrillar matrices have the potential to be used for cell transplantation or other tissue engineering applications.

Selective differentiation of neural progenitor cells by high-epitope density nanofibers.

Neural progenitor cells were encapsulated in vitro within a three-dimensional network of nanofibers formed by self-assembly of peptide amphiphile molecules. The self-assembly is triggered by mixing cell suspensions in media with dilute aqueous solutions of the molecules, and cells survive the growth of the nanofibers around them. These nanofibers were designed to present to cells the neurite-promoting laminin epitope IKVAV at nearly van der Waals density. Relative to laminin or soluble peptide, the artificial nanofiber scaffold induced very rapid differentiation of cells into neurons, while discouraging the development of astrocytes. This rapid selective differentiation is linked to the amplification of bioactive epitope presentation to cells by the nanofibers.