Computer-Aided Design of Lasso-like Self-Assembling Anticancer Peptides with Multiple Functions for Targeted Self-Delivery and Cancer Treatments.

Anticancer peptides are promising drug candidates for cancer treatment, but the short circulation time and low delivery efficiency limit their clinical applications. Herein, we designed several lasso-like self-assembling anticancer peptides (LASAPs) integrated with multiple functions by a computer-aided approach. Among these LASAPs, LASAP1 (CRGDKGPDCGKAFRRFLGALFKALSHLL, 1-9 disulfide bond) was determined to be superior to the others because it can self-assemble into homogeneous nanoparticles and exhibits improved stability in serum. Thus, LASAP1 was chosen for proving the design idea. LASAP1 can self-assemble into nanoparticles displaying iRGD on the surface because of its amphiphilic structure and accumulate to the tumor site after injection because of the EPR effect and iRGD targeting to αVß3 integrin. The nanoparticles could disassemble in the acidic microenvironment of the solid tumor, and cleaved by the overexpressed hK2, which was secreted by prostate tumor cells, to release the effector peptide PTP-7b (FLGALFKALSHLL), which was further activated by the acidic pH. Therefore, LASAP1 could target the orthotopic prostate tumor in the model mice after intraperitoneal injection and specifically inhibit tumor growth, with low systematic toxicity. Combining the multiple targeting functions, LASAP1 represents a promising design of self-delivery of peptide drugs for targeted cancer treatments.

Ethylene-Carbonate-Free Electrolytes for Rechargeable Li-Ion Pouch Cells at Sub-Freezing Temperatures.

Sub-freezing temperature presents a significant challenge to the survival of current Li-ion batteries (LIBs) as it leads to low capacity retention and poor cell rechargeability. The electrolyte in commercial LIBs relies too heavily on ethylene carbonate (EC) to produce a stable solid electrolyte interphase (SEI) on graphite (Gr) anodes, but its high melting point (36.4 °C) severely restricts ion transport below 0 °C, causing energy loss and Li plating. Here, a class of EC-free electrolytes that exhibits remarkable low-temperature performance without compromising cell lifespan is reported. It is found that at sub-zero temperatures, EC forms highly resistive SEI that seriously impedes electrode kinetics, whereas EC-free electrolytes create a highly stable, low-impedance SEI through anion decomposition, which boosts capacity retention and eliminates Li plating during charging. Pouch-type LiCoO2 (LCO)|Gr cells with EC-free electrolytes sustain 900 cycles at 25 °C with 1 C charge/discharge, and LiNi0.85 Co0.10 Al0.05 O2 (NCA)|Gr cells last 300 cycles at -15 °C with 0.3 C charge, both among the best-performing in the literature under comparable conditions. Even at -50 °C, the NCA|Gr cell with EC-free electrolytes still delivers 76% of its room-temperature capacity, outperforming EC-based electrolytes.

Gag Protein Oriented Supramolecular Nets as Potential HIV Traps.

For HIV/AIDS treatment, the cocktail therapy which uses a combination of anti-retroviral drugs remains the most widely accepted practice. However, the potential drug toxicity, patient tolerability, and emerging drug resistance have limited its long-term efficiency. Here, we design a HIV Gag protein-targeting redox supramolecular assembly (ROSA) system for potential HIV inhibition. An assembling precursor was constructed through conjugation of an oxidation-activatable fluorogenic compound BQA with a selected tetrapeptide GGFF. Since BQA shares a similar structure with the known Gag inhibitor, the precursor could bind to HIV Gag protein with moderate affinity. Moreover, after oxidation, the corresponding nanofibers could bind to Gag protein and trap HIV to realize virus control, thus providing a potential anti-HIV strategy.

Hydrogen sulfide induced supramolecular self-assembly in living cells.

Here we developed a critical gasotransmitter (H2S) mediated reduction to induce supramolecular self-assembly in multiple living cell lines. Specifically, the reduction converted an azido group to an amine which allowed the formation of intramolecular hydrogen bonds. The hydrogen bonds planarized the assembling molecules and promoted the supramolecular self-assembly.

Self-assembly nanostructure controlled sustained release, activity and stability of peptide drugs.

Peptides are considered as a new generation of drugs due to their high structural and functional diversity. However, the development of peptide drugs is always limited by their poor stability and short circulation time. Carriers are applied for peptide drug delivery, but there may be problems like poor loading efficiency and undesired xenobiotic toxicity. Peptide self-assembly is an effective approach to improve the stability and control the release of peptide drugs. In this study, two self-assembling anticancer peptides are designed by appending a pair of glutamic acid and asparagine to either the N-terminus or the C-terminus of a lytic peptide. This simple, yet rational sequence modification was made to change the amphiphilic pattern and secondary structural content of the parent peptide, thereby modulating its self-assembly process. It was found that the N-terminus modified peptide favors the formation of nanofibrils and the peptide with C-terminal modification formed micelles. Although both nanostructures showed prolonged action profiles and improved serum stability compared to the parent peptide, the morphology of the nanostructures is highly critical to manipulate the release profile of the free peptide from the assembly and regulate their bioactivity. We believe the self-assembly approach demonstrated in this study can be applied to a variety of therapeutic peptide drugs to improve their stability and therapeutic activity for the development of carrier-free drug delivery system.

Isoleucine/leucine residues at "a" and "d" positions of a heptad repeat sequence are crucial for the cytolytic activity of a short anticancer lytic peptide.

Many lytic peptides contain a heptad sequence with leucine or isoleucine residues at "a" and "d" positions. However, their roles in the peptide-induced cytolytic process remain unclear. We have recently reported an anticancer lytic peptide ZXR-2 (FKIGGFIKKLWRSLLA), which contains a shortened zipper-like sequence with Ile/Leu at "a" and "d" positions. To understand the roles of these Ile/Leu residues, a series of analogs were constructed by sequentially replacing the Ile or Leu residue with alanine (Ala). Significant reduction of the cytolytic activity was observed when the Ile (3rd and 7th) and Leu (10th and 14th) residues at the "a" and "d" positions were substituted, while the replacement of the separate Leu (15th) residue had less effect. Based on the quenching of the intrinsic fluorescence of the peptides and their induced surface pressure changes of lipid monolayer, it was conjectured that the peptide ZXR-2 might insert into cell membranes from the C-terminal and to a depth of the W11 position. Accordingly, I3, I7, and L10 residues which mainly exposed in aqueous solution were more responsible for the peptide self-association on cell membranes, while L14, together with L15, might help peptide insert and anchor to cell membranes. These results are significant to elucidate the crucial roles of such Ile/Leu residues at "a" and "d" positions in peptide-peptide and peptide-membrane interactions to exert the membrane disruption activity of lytic peptides. With further understanding about the structure-activity relationship of lytic peptides, it would be helpful for designing novel anticancer lytic peptides.

From a pro-apoptotic peptide to a lytic peptide: One single residue mutation.

Further discovery and design of new anticancer peptides are important for the development of anticancer therapeutics, and study on the detailed acting mechanism and structure-function relationship of peptides is critical for anticancer peptide design and application. In this study, a novel anticancer peptide ZXR-1 (FKIGGFIKKLWRSKLA) derived from a known anticancer peptide mauriporin was developed, and a mutant ZXR-2 (FKIGGFIKKLWRSLLA) with only one residue difference at the 14th position (Lys→Leu) was also engineered. Replacement of the lysine with leucine made ZXR-2 more potent than ZXR-1 in general. Even with only one residue mutation, the two peptides displayed distinct anticancer modes of action. ZXR-1 could translocate into cells, target on the mitochondria and induce cell apoptosis, while ZXR-2 directly targeted on the cell membranes and caused membrane lysis. The variance in their acting mechanisms might be due to the different amphipathicity and positive charge distribution. In addition, the two Ile-Leu pairs (3-10 and 7-14) in ZXR-2 might also play a role in improving its cytotoxicity. Further study on the structure-function relationship of the two peptides may be beneficial for the design of novel anticancer peptides and peptide based therapeutics.

Hydrophobicity-induced prestaining for protein detection in polyacrylamide gel electrophoresis.

An AIE fluorescent surfactant has been first used to prestain protein by ultrastrong hydrophobic interaction between fluorescent surfactants and proteins, distinguishing from the most widely used poststaining strategies by employing AIE molecules with weak hydrophobic characteristics. A mixture of proteins with variable molecular weights has been detected.

Role of peptide self-assembly in antimicrobial peptides.

Antimicrobial peptides (AMPs) are considered as potential antibiotic substitutes because of their potent activities. Previous studies mainly focused on the effects of peptide charges and secondary structures, but the self-assembly of AMPs was neglected. As more and more researchers notice the roles of peptide self-assembly in AMPs, it has been considered as another important property. In this review, we will discuss the influences of peptide self-assembly on the activity and mode of action, and some specific features it introduces to the AMPs, such as particular responsiveness, improved cell selectivity and stability and sustained release. In addition, some methods to design self-assembling AMPs are primarily discussed. With further understanding about the self-assembling regularity, design of particular self-assembling AMPs will be very helpful for their applications, especially in the fields of drug delivery and biomedical engineering.

Self-assembly of pH and calcium dual-responsive peptide-amphiphilic hydrogel.

Peptide-based hydrogels have gained much interest for biomedical applications as a result of their biocompatibility. Herein, we reported a synthetic pH-sensitive and calcium-responsive peptide-amphiphilic hydrogel. The sequences of the peptide amphiphiles were derived from the repeat-in-toxin (RTX) motif. At a certain peptide-amphiphile concentration, self-assembly was accompanied by the formation of a rigid, viscoelastic hydrogel at low pH or the presence of calcium ions. Circular dichroism spectra showed that the peptide amphiphiles adopted beta-sheet structure. Meanwhile, as revealed by transmission electron microscopy, the peptide-amphiphile self-assembly was accompanied by the formation of long interconnected nanofibrillar superstructure. Material properties of the resulting peptide-amphiphile hydrogel were characterized using oscillatory sheer rheology, and the storage modulus (G') was found to be one order of magnitude higher than the loss modulus (G"), indicating a moderately rigid viscoelastic material. Furthermore, with systematical residue substitution, it was found that the aspartic acid within the repeat-in-toxin sequence of peptide amphiphiles was responsible for the pH and calcium selectivity. The environmental responsiveness, secondary structure, morphology, and mechanical nature of the peptide-amphiphile hydrogel make it a possible material candidate for biomedical and engineering application.