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An enzymatic formation of supramolecular hydrogels based on self-assembled nanofibers of a derivative of β-amino acid, which exhibit excellent in vivo biostability, is discussed. Tripeptide derivative that consists of two β-amino acids and one α-amino acid residue was used to evaluate whether it undergoes enzymatic hydrogelation in vitro and in vivo. It was assumed that α-amino acid residue make the precursor susceptible to the enzyme, while the depeptide segment of β-amino acid would confer excellent stability of the resulted hydrogelator in a biological environment. In vivo experiments suggested that the hydrogels formed by β-amino acid derivatives had a longer lifetime than that of hydrogels formed by α-amino acid derivatives. The high bioavailability and biostability of supramolecular hydrogels comprising β-amino acid derivatives makes these hydrogels promising candidates for biomedical applications when long-term stability is required.

A simple supramolecular hydrogel based on D-glucosamine, a naturally occurring aminosaccharide, promises new biomaterials for applications such as wound healing.

This paper reports the rational design and synthesis of a beta-lactam conjugate. Treating the conjugate with beta-lactamase cleaves the scissile -lactam amide bond, releases a hydrogelator, and results in enzymatic formation of a supramolecular hydrogel. The process involves the use of a bacterial enzyme-the one causes antibiotic inactivation and accounts for resistance to beta-lactams in many clinical important pathogens-to catalyze the formation of the hydrogel. It offers an opportunity to investigate the kinetics of these types of enzymatic reactions, screen inhibitors of the enzyme, and provides a new candidate to generate hydrogels for biomedical applications.

Here we report a new class of molecular hydrogelators based on the conjugates of dipeptide and (naphthalen-2-yloxy)acetic acid. They form hydrogels efficiently the lowest concentration for them to gel water is 0.07 wt\%. Two hydrogelators show the ability to form helical nanofibers within the hydrogels, and the chirality of the hydrogelators apparently dictates the handedness of the nanofibers-D-peptide and L-peptide afford left-handed and right-handed self-assembled nanofibers in the hydrogels, respectively. Moreover, MTT assay of the viability of cells indicates that these molecular hydrogelators are biocompatible.

(Figure Presented) Control from within: Supramolecular hydrogelation to form nanostructures intracellularly (see picture) has been developed as a new methodology to control the fate of cells. Enzyme-regulated self-assembly of small molecules inside cells could lead to a new paradigm for managing cellular processes, understanding cellular functions, and developing new therapeutics through supramolecular chemistry. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

This highlight summarizes recent advances in the enzymatic formation of supramolecular hydrogels, a new method for the creation of biofunctional soft matter. Using phosphatase, thermolysin, beta-lactamase, and phosphatase/kinase as examples, we illustrate the design and application of enzyme catalyzed or regulated formation of supramolecular hydrogels. This approach provides a new strategy to detect the presence of enzymes, screen enzyme inhibitors, assist biomineralization, assay the types of bacteria, and aid the development of smart drug delivery systems. The strategy of using enzymes to control the self-assembly of small molecules described in this highlight will lead to the further development of new materials for biomedical applications and improve understanding of molecular self-assembly in water.

This communication reports the use of Congo red to stain the nanofibers of self- assembled small molecules for assaying intracellular supramolecular hydrogels, which provides a convenient method to explore molecular self- assembly inside cells.

We report the evaluation of cytotoxicity of a new type of engineered nanomaterials, FePt@CoS2 yolk-shell nanocrystals, synthesized by the mechanism of the Kirkendall effect when FePt nanoparticles serve as the seeds. The cytotoxicity of FePt@CoS2 yolk-shell nanocrystals, evaluated by MTT assay, shows a much lower IC50 (35.5 +/- 4.7 ng of Pt/mL for HeLa cell) than that of cisplatin (230 ng of Pt/mL). In the control experiment, cysteine-modified FePt nanoparticles exhibit IC50 at 12.0 +/- 0.9 mu g of Pt/mL. Transmission electron microscopy confirms the cellular uptake of FePt@CoS2 nanocrystals, and the magnetic properties analysis (SQUID) proves the release of FePt nanoparticles from the yolk-shell nanostructures after cellular uptake. These results are significant because almost none of the platinum-based complexes produced for clinical trials in the past 3 decades have shown higher activity than that of the parent drug, cisplatin. The exceptionally high toxicity of FePt@CoS2 yolk-shell nanocrystals (about 7 times higher than that of cisplatin in terms of Pt) may lead to a new design of an anticancer nanomedicine.

This paper reports the synthesis and photodynamic therapy (PDT) effect of a porphyrin derivative containing tyrosine phosphate, which promises a new, useful approach to develop PDT agents.