Taurine Boosts Cellular Uptake of Small D-Peptides for Enzyme-Instructed Intracellular Molecular Self-Assembly

Cyclic dipeptide based cell-penetrating peptidomimetics for effective DNA delivery

A cyclic dipeptide as an unnatural amino acid employed in the preparation of novel cell penetrating peptidomimetics and their effective DNA delivery is demonstrated.

AIE fluorophore with enhanced cellular uptake for tracking esterase-activated release of taurine and ROS scavenging

Fluorophores with aggregation-induced emission (AIE) characteristics are attractive and versatile tools for both chemical sensing and biological imaging. Herein, we designed and synthesized a fluorescent light-up system CTPE-Tau with enhanced cellular uptake ability. The system possesses several advantages, such as a large Stokes shift, low cytotoxicity, and good photostability. Also, it has been successfully utilized to track esterase-activated release of taurine and to scavenge intracellular ROS, and shows great potential for trackable visualized therapy.

Dual aggregation-induced emission for enhanced fluorescence sensing of furin activity in vitro and in living cells

A dual aggregation-induced emission probe was designed for effectively sensing furin activity in vitro and in living cells.

Integrating Enzymatic Self-Assembly and Mitochondria Targeting for Selectively Killing Cancer Cells without Acquired Drug Resistance

Targeting organelles by modulating the redox potential of mitochondria is a promising approach to kill cancer cells that minimizes acquired drug resistance. However, it lacks selectivity because mitochondria perform essential functions for (almost) all cells. We show that enzyme-instructed self-assembly (EISA), a bioinspired molecular process, selectively generates the assemblies of redox modulators (e.g., triphenyl phosphinium (TPP)) in the pericellular space of cancer cells for uptake, which allows selectively targeting the mitochondria of cancer cells. The attachment of TPP to a pair of enantiomeric, phosphorylated tetrapeptides produces the precursors (L-1P or D-1P) that form oligomers. Upon dephosphorylation catalyzed by ectophosphatases (e.g., alkaline phosphatase (ALP)) overexpressed on cancer cells (e.g., Saos2), the oligomers self-assemble to form nanoscale assemblies only on the surface of the cancer cells. The cancer cells thus uptake these assemblies of TPP via endocytosis, mainly via a caveolae/raft-dependent pathway. Inside the cells, the assemblies of TPP-peptide conjugates escape from the lysosome, induce dysfunction of mitochondria to release cytochrome c, and result in cell death, while the controls (i.e., omitting TPP motif, inhibiting ALP, or removing phosphate trigger) hardly kill the Saos2 cells. Most importantly, the repeated stimulation of the cancers by the precursors, unexpectedly, sensitizes the cancer cells to the precursors. As the first example of the integration of subcellular targeting with cell targeting, this study validates the spatial control of the assemblies of nonspecific cytotoxic agents by EISA as a promising molecular process for selectively killing cancer cells without inducing acquired drug resistance.

Ligand-Receptor Interaction Modulates the Energy Landscape of Enzyme-Instructed Self-Assembly of Small Molecules

The concurrence of enzymatic reaction and ligand-receptor interactions is common for proteins, but rare for small molecules and has yet to be explored. Here we show that ligand-receptor interaction modulates the morphology of molecular assemblies formed by enzyme-instructed assembly of small molecules. While the absence of ligand-receptor interaction allows enzymatic dephosphorylation of a precursor to generate the hydrogelator that self-assembles to form long nanofibers, the presence of the ligand-receptor interaction biases the pathway to form precipitous aggregates containing short nanofibers. While the hydrogelators self-assemble to form nanofibers or nanoribbons that are unable to bind with the ligand (i.e., vancomycin), the addition of surfactant breaks up the assemblies to restore the ligand-receptor interaction. In addition, an excess amount of the ligands can disrupt the nanofibers and result in the precipitates. As the first example of the use of ligand-receptor interaction to modulate the kinetics of enzymatic self-assembly, this work not only provides a solution to evaluate the interaction between aggregates and target molecules but also offers new insight for understanding the emergent behavior of sophisticated molecular systems having multiple and parallel processes.

Design and Synthesis of Nanofibers of Self-assembled de novo Glycoconjugates towards Mucosal Lining Restoration and Anti-Inflammatory Drug Delivery

The medical practice for IBD is solely based on anti-inflammatory drugs, but the outcome is far from ideal. Our long-term research goal is to seek a better clinical outcome by combining the anti-inflammatory therapy with physical mucus layer restoration. As the first step towards that objective, we choose to develop self-assembled hydrogels of de novo glycoconjugates that consist of anti-inflammatory drugs and glycopeptides. By covalently linking peptides (e.g., nap-phe-phe-lys), saccharides (e.g., glucosamine), and an anti-inflammatory drug (i.e., olsalazine), we have demonstrated that the obtained molecules self-assemble in water to form hydrogels composed of 3D networks of the nanofibers under acidic conditions. We also confirmed that the resulting glycoconjugates are cell compatible. However, the preliminary assessment of the efficacy of the hydrogels on the murine model is inconclusive, which warrants further investigation and molecular engineering.

An intracellular anchor regulates the distribution of bioactive molecules

Based on bioorthogonal tetrazine ligation, a pre-targeted anchor strategy was developed to regulate the intracellular distribution of bioactive molecules. This strategy could solve the issue regarding the permeability and targeting ability of bioactive molecules in the specific organelles of living cells.

Enzyme-Instructed Self-Assembly for Spatiotemporal Profiling of the Activities of Alkaline Phosphatases on Live Cells

Alkaline phosphatase (ALP), an ectoenzyme, plays important roles in biology. But there is no activity probes for imaging ALPs in live cell environment due to the diffusion and cytotoxicity of current probes. Here we report the profiling of the activities of ALPs on live cells by enzyme-instructed self-assembly (EISA) of a D-peptidic derivative that forms fluorescent, non-diffusive nanofibrils. Our study reveals the significantly higher activities of ALP on cancer cells than on stromal cells in their co-culture and shows an inherent and dynamic difference in ALP activities between drug sensitive and resistant cancer cells or between cancer cells with and without hormonal stimulation. Being complementary to genomic profiling of cells, EISA, as a reaction-diffusion controlled process, achieves high spatiotemporal resolution for profiling activities of ALPs of live cells at single cell level. The activity probes of ALP contribute to understanding the reversible phosphorylation/dephosphorylation in the extracellular domains that is an emerging frontier in biomedicine.

Enzymatic induction of supramolecular order and bioactivity

We showed in this study that enzymatic triggering is a totally different pathway for the preparation of self-assembling nanomaterials to the heating-cooling process. Because the molecules were under lower energy levels and the molecular conformation was more ordered during the enzymatic triggeration under mild conditions, nanomaterials with higher supramolecular order could be obtained through biocatalytic control. In this study, nanoparticles were obtained by an enzymatic reaction and nanofibers were observed through the heating-cooling process. We observed a distinct trough at 318 nm from the CD spectrum of a particle sample but not a fiber sample, suggesting the long range arrangement of molecules and helicity in the nanoparticles. The nanoparticles with higher supramolecular order possessed much better potency as a protein vaccine adjuvant because it accelerated the DC maturation and elicited stronger T-cells cytokine production than the nanofibers. Our study demonstrated that biocatalytic triggering is a useful method for preparing supramolecular nanomaterials with higher supramolecular order and probably better bioactivity.

Regulating the Rate of Molecular Self-Assembly for Targeting Cancer Cells

Besides tight and specific ligand-receptor interactions, the rate regulation of the formation of molecular assemblies is one of fundamental features of cells. But the latter receives little exploration for developing anticancer therapeutics. Here we show that a simple molecular design of the substrates of phosphatases-tailoring the number of phosphates on peptidic substrates-is able to regulate the rate of molecular self-assembly of the enzyme reaction product. Such a rate regulation allows selective inhibition of osteosarcoma cells over hepatocytes, which promises to target cancer cells in a specific organ. Moreover, our result reveals that the direct measurement of the rate of the self-assembly in a cell-based assay provides precise assessment of the cell targeting capability of self-assembly. This work, as the first report establishing rate regulation of a multiple-step process to inhibit cells selectively, illustrates a fundamentally new approach for controlling the fate of cells.

Self-assembled nanomaterials for photoacoustic imaging

In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

In situ enzymatic formation of supramolecular nanofibers for efficiently killing cancer cells

Precursors were more toxic to cancer cells than their corresponding gelators.

Supramolecular nanofibers of self-assembling peptides and DDP to inhibit cancer cell growth

The addition of cis-dichlorodiamineplatinum(ii) to a taxol-peptide amphiphile results in hydrogelations.

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping address fundamental questions about the mechanisms or the consequences of the self-assembly of molecules, including low molecular weight ones. Finally, we provide a perspective on supramolecular hydrogelators. We hope that this review will serve as an updated introduction and reference for researchers who are interested in exploring supramolecular hydrogelators as molecular biomaterials for addressing the societal needs at various frontiers.

Ultrasound accelerated sugar based gel for in situ construction of a Eu3+-based metallogel via energy transfer in a supramolecular scaffold

Phase control on the energy transfer process via an “off–on” approach between a 4-amino-naphthalimide derivative and Eu³⁺ ions was achieved in sugar-based organogel tissue.