Biofluid-Triggered Burst Release from an Adaptive Covalently Assembled Dipeptide Nanocontainer for Emergency Treatment

Microballoons: Osmotically-inflated elastomer shells for ultrafast release of encapsulants and mechanical energy

HYPOTHESIS

Microcapsules with osmotically-inflated elastic shells exhibit an ultrafast release of encapsulants while mechanically stimulating the microenvironments, akin to popping balloons.

EXPERIMENTS

To prepare elastic shells with uniform thickness and size, monodisperse water-in-oil-in-water (W/O/W) double-emulsion drops are produced in a capillary microfluidic device. The polydimethylsiloxane (PDMS)-containing oil phase is thermally cured to create the elastic shell. The elastic shells are inflated by pumping water into the lumen in hypotonic conditions. The inflated microcapsules produced undergo mechanical compression, and their release properties are studied.

FINDINGS

By controlling the osmotic pressure difference, Microballoons are inflated into a diameter of 200 μm - 316 μm and shell thickness of 7.8 μm - 0.7 µm, respectively. The inflated shell pops due to mechanical failure when subjected to mechanical stress above a certain threshold, resembling a balloon. During popping, the stretched shell rapidly retracts to the original uninflated state, resulting in an ultrafast release of encapsulants from the lumen within a millisecond. This process converts elastic potential energy stored in the shell into mechanical energy with substantial power. The microballoons mechanically stimulate the local environment, leading to the direct and rapid release of encapsulants. This has the potential to improve absorption efficiency.

Light-triggered AND logic tetrapeptide dynamic covalent assembly

We demonstrate light-triggered dynamic covalent assembly of a linear short tetrapeptide containing two terminal cysteine residues in an AND logic manner. A photobase generator is introduced to accomplish light-mediated pH regulation to increase the reduction potential of thiols in the tetrapeptide, which activates its oxidative polymerization through disulfide bonds. Interestingly, it is elucidated that under light irradiation, mere co-existence of photobase generator and the oxidizing agent permits the polymerization performance of this tetrapeptide. Hence, a light-triggered AND logic dynamic covalent assembly of a tetrapeptide is achieved. Further, upon redox response, the reversible aggregation and disaggregation can be transformed for numerous times due to the dynamic covalent feature of disulfide bond. As a comparison, no assembly occurs for a short peptide containing one terminal cysteine residue under the same stimuli condition. This work offers a new approach to remotely control programmable molecular assembly of short linear peptides based on dynamic covalent bond, holding great potential in wide bioapplications.

Hemoadhican, a Tissue Adhesion Hemostatic Material Independent of Blood Coagulation

Uncontrolled hemorrhage is a leading cause of death, emphasizing the need for novel hemostatic agents. Here, a novel hemostatic polysaccharide hemoadhican (HD) is screened out by analyzing the rheological properties of screened material mixed blood sludges, which is prepared by mixing polysaccharide granules and whole blood to mimic the coagulation in vitro. HD is produced by a bacterial isolate Paenibacillus sp.1229, and the repeating units of HD are →)-α-L-Rhap-(1→3)-β-D-Glcp-(1→4)[4,6-ethylidene-α-D-Galp-(1→4)-α-D-Glcp-(1→3)]-α-D-Manp-(1→. Compared to chitosan and celox, HD achieves more effective hemostasis in animal models with mouse and rat femoral arteries, rat carotid arteries, and rabbit femoral arteries. Especially, HD maintains an excellent hemostatic capability in animals with heparin-induced hemorrhage diathesis. In vitro experiments show HD granules can quickly absorb a small amount of blood component to create a hemophobic blood sludge resistant to high pressure. The blood sludge firmly adheres to damaged tissue and efficiently repels blood. In vitro experiments show that HD does not actively trigger blood coagulation cascade and is independent of blood conditions including heparin treatment. In addition, HD moisturizes wounds and accelerates wound healing, exhibiting excellent biodegradability, and hemocompatibility. The results indicate that HD is a promising hemostatic material for treating traumatic hemorrhages and uncontrollable surgical bleeding.

Actively cross-linking hemostatic sealant enables rapid hemostasis and wound closure

A rapid hemostatic sealant can save a patient's life from shock and death due to severe trauma or excessive bleeding from the wound site during surgery. However, an ideal hemostatic sealant needs to meet the standards of safety, efficacy, usability, cost, and approvability and overcome new challenges. Here, we devised a combinatorial hemostatic sealant of PEG succinimidyl glutarate-based cross-linking branched polymers (CBPs) and the active hemostatic peptide (AHP). After ex vivo optimization, the best hemostatic combination was called an active cross-linking hemostatic sealant (ACHS). Interestingly, ACHS formed cross-links with serum proteins, blood cells, and tissue and interconnected coating on blood cells, which might induce hemostasis and tissue adhesion based on SEM images. Moreover, ACHS showed the highest coagulation efficacy, formation, and agglomeration of thrombi within 12 s, and in vitro biocompatibility. Mouse model experiments represented rapid hemostasis within 1 min, wound closure of the liver incision, and less bleeding than the commercialized sealant with tissue biocompatibility. ACHS has the advantages of rapid hemostasis, mild sealant, and easy supply by chemical synthesis without inhibition by anticoagulants, which might minimize bacterial infection by immediate wound closure. Therefore, ACHS could become a new-type hemostatic sealant to match surgical needs for internal bleeding.

Proteolytic Resistance Determines Albumin Nanoparticle Drug Delivery Properties and Increases Cathepsin B, D, and G Expression

Proteolytic activity is pivotal in maintaining cell homeostasis and function. In pathological conditions such as cancer, it covers a key role in tumor cell viability, spreading to distant organs, and response to the treatment. Endosomes represent one of the major sites of cellular proteolytic activity and very often represent the final destination of internalized nanoformulations. However, little information about nanoparticle impact on the biology of these organelles is available even though they represent the major location of drug release. In this work, we generated albumin nanoparticles with a different resistance to proteolysis by finely tuning the amount of cross-linker used to stabilize the carriers. After careful characterization of the particles and measurement of their degradation in proteolytic conditions, we determined a relationship between their sensitivity to proteases and their drug delivery properties. These phenomena were characterized by an overall increase in the expression of cathepsin proteases regardless of the different sensitivity of the particles to proteolytic degradation.

Liquid-liquid phase separation of immiscible polymers at double emulsion interfaces for configurable microcapsules

Liquid-liquid phase separation at complex interfaces is a common phenomenon in biological systems and is also a fundamental basis to create synthetic materials in multicomponent mixtures. Understanding the liquid-liquid phase separation in well-defined macromolecular systems is anticipated to shed light on similar behaviors in cross-disciplinary areas. Here we study a series of immiscible polymers and reveal a generic phase diagram of liquid-liquid phase separation at double emulsion interfaces, which depicts the equilibrium structures by interfacial tension and polymer fraction. We further reveal that the interfacial tensions in various systems fall on a linear relationship with spreading coefficients. Based on this theoretical guideline, the liquid-liquid phase separation can be modulated by a low fraction of amphiphilic block copolymers, leading the double emulsion droplets configurable between compartments and anisotropic shapes. The solidified anisotropic microcapsules could provide unique orientation-sensitive optical properties and thermomechanical responses. The theoretical analysis and experimental protocol in this study yield a generalizable strategy to prepare multiphase double emulsions with controlled structures and desired properties.

Cancer-Responsive Multifunctional Nanoplatform Based on Peptide Self-Assembly for Highly Efficient Combined Cancer Therapy by Alleviating Hypoxia and Improving the Immunosuppressive Microenvironment

Hypoxia, as a main feature of the tumor microenvironment, has greatly limited the efficacy of photodynamic therapy (PDT), as well as its clinical application. Here, a multifunctional composite nanoplatform, the peptide/Ce6/MnO₂ nanocomposite (RKCM), has been constructed to alleviate tumor hypoxia and increase the efficacy of PDT using rationally designed peptide fibrils to encapsulate chlorin e6 (Ce6) inside and to mineralize MnO₂ nanoparticles on the surface. As a result, RKCM significantly improved the PDT efficacy by increasing reactive oxygen species (ROS) generation, decreasing tumor cell viability, and inhibiting tumor growth and metastasis. Besides, decreased HIF-1α expression and increased immune-activated cell infiltration were also observed in RKCM/laser treatment xenograft. Mechanically, (1) Ce6 can induce singlet oxygen (¹O₂) generation under laser irradiation to give photodynamic therapy (PDT); (2) MnO₂ can react with H₂O₂ in situ to supply additional O₂ to alleviate tumor hypoxia; and (3) the released Mn²⁺ ions can induce a Fenton-like reaction to generate ^•OH for chemical dynamic therapy (CDT). Moreover, RKCM/laser treatment also presented with an abscopal effect to block the occurrence of lung metastasis by remolding the pre-metastasis immune microenvironment. With these several aspects working together, the peptide/Ce6/MnO₂ nanoplatform can achieve highly efficient tumor therapy. Such a strategy based on peptide self-assembly provides a promising way to rationally design a cancer-responsive multifunctional nanoplatform for highly efficient combined cancer therapy by alleviating hypoxia and improving the immune microenvironment.

Stimulus-Responsive Amino Acids Behind In Situ Assembled Bioactive Peptide Materials

In situ self-assembly of peptides into well-defined nanostructures represents one of versatile strategies for creation of bioactive materials within living cells with great potential in disease diagnosis and treatment. The intimate relationship between amino acid sequences and the assembling propensity of peptides has been thoroughly elucidated over the past few decades. This has inspired development of various controllable self-assembling peptide systems based on stimuli-responsive naturally occurring or non-canonical amino acids, including redox-, pH-, photo-, enzyme-responsive amino acids. This review attempts to summarize the recent progress achieved in manipulating in situ self-assembly of peptides by controllable reactions occurring to amino acids. We will highlight the systems containing non-canonical amino acids developed in our laboratory during the past few years, primarily including acid/enzyme-responsive 4-aminoproline, redox-responsive (seleno)methionine, and enzyme-responsive 2-nitroimidazolyl alanine. Utilization of the stimuli-responsive assembling systems in creation of bioactive materials will be specifically introduced to emphasize their advantages for addressing the concerns lying in disease theranostics. Eventually, we will provide the perspectives for the further development of stimulus-responsive amino acids and thereby demonstrating their great potential in development of next-generation biomaterials.

Covalently triggered self-assembly of peptide-based nanodrugs for cancer theranostics

Covalently triggered peptide self-assembly is achieved through sequential integration of spontaneous covalent reaction and noncovalent interactions, thus both enhancing the physiological stability and extending unexpected functionality of the resulting peptide-based assemblies, different from popular supramolecular peptide self-assembly merely associated with noncovalent interactions. This review summarizes the recent progress on the development of covalently triggered peptide self-assembly for cancer theranostics. Especially, we propose the fundamental design principle of covalently triggered peptide self-assembly for constructing a variety of peptide-based assemblies including nanoparticles, nanofibers, hollow nanospheres, and other nanoarchitectures. Subsequently, the discussion is anchored in an overview of representative covalently assembled peptide-based nanodrugs for the cancer theranostics. Finally, the challenges and perspectives on the clinical potential of the covalently assembled peptide-based nanodrugs are highlighted. This review will provide new insights into construction of peptide-based nanodrugs through combination of covalent reaction and noncovalent self-assembly and prompt their clinical applications in cancer diagnosis and therapeutics.

A mini-review on peptide-based self-assemblies and their biological applications

Peptide-based supramolecular self-assembly from peptide monomers into well-organized nanostructures, has attracted extensive attentions towards biomedical and biotechnological applications in recent decades. This spontaneous and reversible assembly process involving non-covalent bonding interactions can be artificially regulated. In this review, we have elaborated different strategies to modulate the peptide self-assembly through tuning the physicochemical and environmental conditions, includingpH, light, temperature, solvent, and enzyme. Detailed introduction of biological applications and future potential of the peptide-based nano-assemblies will also be given.

Supramolecular Nanodrugs Based on Covalent Assembly of Therapeutic Peptides toward In Vitro Synergistic Anticancer Therapy

Therapeutic peptides have attracted significant attention in clinical applications due to their advantages in biological origination and good biocompatibility. However, the therapeutic performance of peptides is usually hindered by their short half-lives in blood and inferior activity. Herein, supramolecular nanodrugs of therapeutic peptides are constructed by covalent assembly of chemotherapeutic peptides through genipin cross-linking. The resulting nanodrugs have intense absorbance in the near-infrared region and high photothermal conversion efficiencies, leading to the possibility of photothermal therapy. The combination of photothermal therapy and chemotherapy using the nanodrugs shows synergistic therapeutic effects on cancer cells. Hence, covalent assembly not only maintains the chemotherapeutic activities of the peptides but also triggers supramolecular photothermal effects, demonstrating that the covalent assembly of therapeutic peptides through genipin cross-linking is an efficient approach in constructing supramolecular nanodrugs toward synergistic anticancer therapy.

Co-assembled gold nanorod@tripeptide core-shell nanospheres for aqueous Hg2+ removal

The construction of peptide and metal nanoparticles hybrid is attractive to explore their synergistic properties and applications extensively. However, it remains a challenge to fabricate a well-defined and size-controllable short peptide/Au nanoparticles hybrid. Here, we report a facile and flexible co-assembly strategy for the construction of tripeptide coated Au nanorods (AuNRs). The tripeptide (Phe-Phe-Cys, FFC) grows via covalently crosslinking to form spheres. The size of the core@shell nanospheres can be controlled by modulating the amount or size of AuNRs. Especially, the concentration of AuNRs fixes the amount of seeds, which further affect the local concentration of FFC on the surface of AuNRs seed, leading to a narrower diameter of hybrid compared to FFC spheres. Moreover, owing to their synergistic effects, this hybrid exhibits a good adsorption capacity of Hg²⁺ from aqueous solutions by electrostatic interaction and forming into Au/Hg amalgam. This strategy could be extended to the fabrication of other biomolecules and metal nanoparticle hybrids with diverse functions.

Enzyme-Triggered Morphological Transition of Peptide Nanostructures for Tumor-Targeted Drug Delivery and Enhanced Cancer Therapy

The use of smart drug carriers to realize cancer-targeted drug delivery is a promising method to improve the efficiency of chemotherapy and reduce its side effects. A surfactant-like peptide, Nap-FFGPLGLARKRK, was elaborately designed for cancer-targeted drug delivery based on an enzyme-triggered morphological transition of the self-assembled nanostructures. The peptide has three functional motifs: the aromatic motif of Nap-FF- to promote peptide self-assembly, the enzyme-cleavable segment of -GPLGLA- to introduce enzyme sensitivity, and the positively charged -RKRK- segment to balance the molecular amphiphilicity as well as to facilitate interaction with cell membranes. The peptide self-assembles into long fibrils with hydrophobic inner cores, which can encapsulate a high amount of anticancer drug doxorubicin (DOX). By having enzyme responsibility, these fibrils can be degraded into thinner ones by the cancer-overexpressed matrix metalloproteinase-7 (MMP7) at tumor sites and precipitate out to give sustained release of DOX, resulting in cancer-targeted drug delivery and selective cancer killing. In vivo antitumor experiments with mice confirm the high efficiency of such enzyme-responsive peptidic drug carriers in successfully suppressing the tumor growth and metastasis while greatly reducing the side effects. The study demonstrates the feasibility of using enzyme-sensitive peptide nanostructures for efficient and targeted drug delivery, which have great potential in biomedical cancer treatment.

Spontaneous Membrane Generation and Extension in a Dipeptide Single Crystal and Phospholipid Mixed System

Self-reproduction is one of the most important characteristics of lipid vesicles for origin of life research. Most vesicle self-reproduction systems are based on fatty acid vesicles and spontaneous phospholipid vesicle production is difficult owing to the relatively high stability of these vesicles. Now, spontaneous phospholipid vesicle generation and extension in a dipeptide/phospholipid system is demonstrated. Dissolution of the dipeptide crystal provides both the driving force and phospholipid constituents for vesicle generation and extension. This study provides a new system to enhance the understanding of vesicle self-reproduction mechanisms.