Wettability of supramolecular nanofibers for controlled cell adhesion and proliferation.

By employing smart self-assembly of 1,4-benyldicarbonxamide-phenylalanine (C2) derived supramolecular gelators, a simple way to construct nanofibrous environments with the controllable wettability is developed. The fast cell adhesion and proliferation on the least wettable fibers indicates an efficient control over cells, which is proved to be mainly mediated by the interaction between protein and the fibers. One typical merit superior to other materials is that cell adhesion can be regulated not only on two-dimensional (2D) substrates but also in three-dimensional (3D) microenvironments. This paves a novel way to deeply understand the influence of fiber wettability on cell behaviors in 3D environment.

Dual-specific interaction to detect DNA on gold nanoparticles.

An approach to selectively and efficiently detect single strand DNA is developed by using streptavidin coated gold nanoparticles (StAuNPs) as efficient quenchers. The central concept for the successful detection is the combination the of streptavidin-biotin interaction with specific probe-target DNA hybridization. Biotin labeled probe DNAs act as "bridges" to bring Cy5 labeled targets to the particle surface and the fluorophore dye can be rapidly and efficiently quenched by StAuPNs. By measuring the changes of photoluminescence intensity of Cy5, an efficient, selective, and reversed detection of DNA hybridization is realized. The methodology may pave a new way for simple and rapid detections of biomolecules.

Antimicrobial Activity with Enhanced Mechanical Properties in Phenylalanine-Based Chiral Coassembled Hydrogels: The Influence of Pyridine Hydrazide Derivatives.

Hydrazide derivatives are known to display a wide range of biological properties including antimicrobial activities, hence making them desirable candidates for soft biomaterials. Herein, we report chiral supramolecular coassembled hydrogels obtained from two phenylalanine gelators (L/DPF and B2L/D) and two dicarbohydrazide molecules (pyridine-2,6-dicarbohydrazide (PDH) and (2,2'-bipyridine)-5,5'-dicarbohydrazide (BDH)) that exhibited enhanced mechanical properties, chirality modulation, and antimicrobial activity. Four lines of coassembled hydrogels were obtained (i.e., L/DPF-PDH, L/DPF-BDH, B2L/D-PDH, and B2L/D-BDH) through hydrogen bonding and π-π stacking with some level of an interpenetrating network, as revealed by the structural characterization analysis. Mechanical properties were significantly improved, especially in the case of hybrid gels involving BDH, with improved average elastic modulus (G') values of 3430 and 3167 Pa for DPF-BDH and B2D-BDH (1:3, molar concentration) over 140 and 1680 Pa for DPF and B2D gelators, respectively. This was attributed to the improved π-π stacking and interpenetrating network due to the bipyridine group and its ease to form fibrous precipitates in the process of heating and cooling to room temperature. PDH, on the other hand, was able to modulate chirality in the L/DPF gelator due to its more planar and less bulky nature and showed antimicrobial activity against Pseudomonas aeruginosa (Gram-negative). Interestingly, when PDH was coassembled with the B2L/D gelator, the hybrid gels exhibited antimicrobial activity against Staphylococcus aureus (Gram-positive) and P. aeruginosa (Gram-negative) by virtue of a synergistic effect of the gelator and the azomethine group of PHD. Hence, by moving from bipyridine (BDH) to pyridine (PDH) as a core structure in the hydrazide molecules, the resulting hybrid hydrogels exhibited desirable properties of antimicrobial activity and improved mechanical attributes.

Amino Acids and Peptide-Based Supramolecular Hydrogels for Three-Dimensional Cell Culture.

Supramolecular hydrogels assembled from amino acids and peptide-derived hydrogelators have shown great potential as biomimetic three-dimensional (3D) extracellular matrices because of their merits over conventional polymeric hydrogels, such as non-covalent or physical interactions, controllable self-assembly, and biocompatibility. These merits enable hydrogels to be made not only by using external stimuli, but also under physiological conditions by rationally designing gelator structures, as well as in situ encapsulation of cells into hydrogels for 3D culture. This review will assess current progress in the preparation of amino acids and peptide-based hydrogels under various kinds of external stimuli, and in situ encapsulation of cells into the hydrogels, with a focus on understanding the associations between their structures, properties, and functions during cell culture, and the remaining challenges in this field. The amino acids and peptide-based hydrogelators with rationally designed structures have promising applications in the fields of regenerative medicine, tissue engineering, and pre-clinical evaluation.

Biotin-Avidin Based Universal Cell-Matrix Interaction for Promoting Three-Dimensional Cell Adhesion.

To promote cell adhesion in three-dimensional (3D) extracellular matrix (ECM) is crucial for avoiding cell anoikis, which is one of the most important issues for fundamental cell biology. Herein, a biotin-avidin based universal cell-matrix interaction for different types of cells is developed in order to achieve the promoted adhesion in 3D ECM. For the purpose, biotinylated nanofibrous hydrogels are constructed by coassembling 1,4-benzyldicarboxamide (C2) based non-biotinylated and biotinylated supramolecular gelators. The used cells are modified by avidin (AV-cells) through biotinylating cells and then interacting with avidin. After in situ encapsulating AV-cells in the hydrogels, the adhered amount can be increased by tens of percent even with adding several percentages of the biotinylated C2 gelators in the coassembly due to the specific biotin-avidin interaction. Reverse transcription polymerase chain reaction (RT-PCR) confirms that AV-cells can proliferate without varying gene expression and denaturation. Compared with the interaction between RGD and cells, this avidin-biotin interaction should be much more universal and it is feasible to be employed to promote cell adhesion for most types of cells in 3D matrix.

Bioinspired Hierarchical Surface Structures with Tunable Wettability for Regulating Bacteria Adhesion.

To circumvent the influence from varied topographies, the systematic study of wettability regulated Gram-positive bacteria adhesion is carried out on bioinspired hierarchical structures duplicated from rose petal structures. With the process of tuning the interfacial chemical composition of the self-assembled films from supramolecular gelators, the varied wettable surfaces from superhydrophilicity to superhydrophobicity can be obtained. The investigation of Gram-positive bacteria adhesion on the hierarchical surfaces reveals that Gram-positive bacteria adhesion is crucially mediated by peptidoglycan due to its different interaction mechanisms with wettable surfaces. The study makes it possible to systematically study the influence mechanism of wettability regulated bacteria adhesion and provides a sight to make the bioinspired topographies in order to investigate wettability regulated bioadhesion.

Convenient three-dimensional cell culture in supermolecular hydrogels.

A convenient three-dimensional cell culture was developed by employing high swelling property of hybrid hydrogels coassembled from C2-phenyl-based supermolecular gelators and sodium hyaluronate. Imaging and spectroscopic analysis by scanning electron microscopy (SEM), atomic force microscopy (AFM), transform infrared (FT-IR) spectra confirm that the hybrid gelators can self-assemble into nanofibrous hydrogel. The high swelling property of dried gel ensures cell migration and proliferation inside bulk of the hydrogels, which provides a facial method to study disease models, the effect of drug dosages, and tissue culture in vitro.

RGD anchored C2-benzene based PEG-like hydrogels as scaffolds for two and three dimensional cell cultures.

Designing new types of cell scaffolds to resist protein adsorption and promote cell adhesion is becoming very important in the field of tissue engineering. Herein, by coupling ethylene glycol (EG) monomers and Arg-Gly-Asp (RGD) onto C2-benzene cores, a family of PEG-like low molecular weight gelators (LMWGs) functionalized with RGD is reported. Imaging and spectroscopic analysis by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Circular Dichroism (CD) spectroscopy confirm that the functionalized LMWGs can self-assemble into nanofibrous hydrogels. The RGD functionalized nano-scaffolds were observed to overcome non-specific protein adsorption and promote adhesion of encapsulated cells through specific RGD-integrin binding. The PEG-like gelators may offer an effective model scaffold for cell cultures that generates specific cell-scaffold interactions with minimal non-specific protein adsorption and addresses some limitations of covalent polymeric scaffolds at the same time.

Gelator-polysaccharide hybrid hydrogel for selective and controllable dye release.

In this paper, 1,4-bi(phenylalanine-diglycol)-benzene (PDB) based Low-Molecular-Weight-Gelator (LMWG) hydrogels are modified using hydrophilic polysaccharide (sodium alginate). A set of techniques including Fourier transform infrared (FT-IR) spectroscopy, (1)H Nuclear Magnetic Resonance ((1)H NMR), X-ray powder diffraction (XRD), Ultraviolet-Visible (UV-Vis), and circular dichroism (CD) had confirmed a ß-turn arrangement of PDB gelators and a semi-interpenetrating network (semi-IPN), which was formed through hydrogen bonds between LMWG fibers and polysaccharide chains. The evaluation of physicochemical properties of hydrogels indicates that gelator-polysaccharide hybrid hydrogels possess better mechanical and water retention properties than LMWG hydrogels. The release study of dyes (model drug) from both LMWG and hybrid hydrogels was carried out. Compared with PDB based hydrogels, hybrid hydrogels show a selective and controllable release property for certain dyes. The results suggest LMWG-polysaccharide hybrid gels may find potential applications as promising drug delivery vehicles for drug molecules.