Lipopeptides as tools in catalysis, supramolecular, materials and medicinal chemistry

Blue Laser Triggered Hemostatic Peptide Hydrogel for Gastrointestinal Bleeding Treatment

In an emergency, nonvariceal upper gastrointestinal bleeding (NVUGIB), endoscopic hemostasis is considered the gold standard intervention. However, current endoscopic hemostasis is very challenging to manage bleeding in large-diameter or deep lesions highly prone to rebleeding risk. Herein, a novel hemostatic peptide hydrogel (HPH) is reported, consisting of a self-assembly peptide sequence CFLIVIGSIIVPGDGVPGDG (PFV) and gelatin methacryloyl (GelMA), which can be triggered by blue laser endoscopy (BLE) for nonvariceal upper gastrointestinal bleeding treatment without recurring bleeding concerns. Upon contact with GelMA solution, PFV immediately fibrillates into β-sheet nanofiber and solvent-induced self-assembly to form HPH gel. HPH nanofiber networks induced ultrafast coagulation by enveloping blood cells and activating platelets and coagulation factors even to the blood with coagulopathy. Besides its remarkable hemostatic performance in artery and liver injury models, HPH achieves instant bleeding management in porcine NVUGIB models within 60 s by preventing the rebleeding risk. This work demonstrates an extraordinary hemostatic agent for NVUGIB intervention by BLE for the first time, broadening potential application scenarios, including patients with coagulopathy and promising clinical prospects.

Unearthing naturally-occurring cyclic antibacterial peptides and their structural optimization strategies

Natural products with antibacterial activity are highly desired globally to combat against multidrug-resistant (MDR) bacteria. Antibacterial peptide (ABP), especially cyclic ABP (CABP), is one of the abundant classes. Most of them were isolated from microbes, demonstrating excellent bactericidal effects. With the improved proteolytic stability, CABPs are normally considered to have better druggability than linear peptides. However, most clinically-used CABP-based antibiotics, such as colistin, also face the challenges of drug resistance soon after they reached the market, urgently requiring the development of next-generation succedaneums. We present here a detail review on the novel naturally-occurring CABPs discovered in the past decade and some of them are under clinical trials, exhibiting anticipated application potential. According to their chemical structures, they were broadly classified into five groups, including (i) lactam/lactone-based CABPs, (ii) cyclic lipopeptides, (iii) glycopeptides, (iv) cyclic sulfur-rich peptides and (v) multiple-modified CABPs. Their chemical structures, antibacterial spectrums and proposed mechanisms are discussed. Moreover, engineered analogs of these novel CABPs are also summarized to preliminarily analyze their structure-activity relationship. This review aims to provide a global perspective on research and development of novel CABPs to highlight the effectiveness of derivatives design in identifying promising antibacterial agents. Further research efforts in this area are believed to play important roles in fighting against the multidrug-resistance crisis.

A Fluorous Peptide Amphiphile with Potent Antimicrobial Activity for the Treatment of MRSA-induced Sepsis and Chronic Wound Infection

The rising prevalence of global antibiotic resistance evokes the urgent need for novel antimicrobial candidates. Cationic lipopeptides have attracted much attention due to their strong antimicrobial activity, broad-spectrum and low resistance tendency. Herein, a library of fluoro-lipopeptide amphiphiles was synthesized by tagging a series of cationic oligopeptides with a fluoroalkyl tail via a disulfide spacer. Among the lipopeptide candidates, R6F bearing six arginine moieties and a fluorous tag shows the highest antibacterial activity, and it exhibits an interesting fluorine effect as compared to the non-fluorinated lipopeptides. The high antibacterial activity of R6F is attributed to its excellent bacterial membrane permeability, which further disrupts the respiratory chain redox stress and cell wall biosynthesis of the bacteria. By co-assembling with lipid nanoparticles, R6F showed high therapeutic efficacy and minimal adverse effects in the treatment of MRSA-induced sepsis and chronic wound infection. This work provides a novel strategy to design highly potent antibacterial peptide amphiphiles for the treatment of drug-resistant bacterial infections.

Redox-Regulated In Situ Seed-Induced Assembly of Peptides

Morphology-transformational self-assembly of peptides allows for manipulation of the performance of nanostructures and thereby advancing the development of biomaterials. Acceleration of the morphological transformation process under a biological microenvironment is important to efficiently implement the tailored functions in living systems. Herein, we report redox-regulated in situ seed-induced assembly of peptides via design of two co-assembled bola-amphiphiles serving as a redox-resistant seed and a redox-responsive assembly monomer, respectively. Both of the peptides are able to independently assemble into nanoribbons, while the seed monomer exhibits stronger assembling propensity. The redox-responsive monomer undergoes morphological transformation from well-defined nanoribbons to nanoparticles. Kinetics studies validate the role of the assembled inert monomer as the seeds in accelerating the assembly of the redox-responsive monomer. Alternative addition of oxidants and reductants into the co-assembled monomers promotes the redox-regulated assembly of the peptides facilitated by the in situ-formed seeds. The reduction-induced assembly of the peptide could also be accelerated by in situ-formed seeds in cancer cells with a high level of reductants. Our findings demonstrate that through precisely manipulating the assembling propensity of co-assembled monomers, the in situ seed-induced assembly of peptides could be achieved. Combining the rapid assembly kinetics of the seed-induced assembly with the common presence of redox agents in a biological microenvironment, this strategy potentially offers a new method for developing biomedical materials in living systems.

Ordered planar plating/stripping enables deep cycling zinc metal batteries

Metal anodes are emerging as culminating solutions for the development of energy-dense batteries in either aprotic, aqueous, or solid battery configurations. However, unlike traditional intercalation electrodes, the low utilization of "hostless" metal anodes due to the intrinsically disordered plating/stripping impedes their practical applications. Herein, we report ordered planar plating/stripping in a bulk zinc (Zn) anode to achieve an extremely high depth of discharge exceeding 90% with negligible thickness fluctuation and long-term stable cycling. The Zn can be plated/stripped with (0001)Zn preferential orientation throughout the consecutive charge/discharge process, assisted by a self-assembled supramolecular bilayer at the Zn anode-electrolyte interface. Through real-time tracking of the Zn atoms migration, we reveal that the ordered planar plating/stripping is driven by the construction of in-plane Zn─N bindings and the gradient energy landscape at the reaction fronts. The breakthrough results provide alternative insights into the ordered plating/stripping of metal anodes toward rechargeable energy-dense batteries.

In situ peptide assemblies for bacterial infection imaging and treatment

Bacterial infections, especially antibiotic-resistant ones, remain a major threat to human health. Advances in nanotechnology have led to the development of numerous antimicrobial nanomaterials. Among them, in situ peptide assemblies, formed by biomarker-triggered self-assembly of peptide-based building blocks, have received increasing attention due to their unique merits of good spatiotemporal controllability and excellent disease accumulation and retention. In recent years, a variety of "turn on" imaging probes and activatable antibacterial agents based on in situ peptide assemblies have been developed, providing promising alternatives for the treatment and diagnosis of bacterial infections. In this review, we introduce representative design strategies for in situ peptide assemblies and highlight the bacterial infection imaging and treatment applications of these supramolecular materials. Besides, current challenges in this field are proposed.