Polypeptide-based drug delivery systems for programmed release

Catalase-positive Staphylococcus epidermidis based cryo-millineedle platform facilitates the photo-immunotherapy against colorectal cancer via hypoxia improvement

The synergistic anti-tumor impact of phototherapy and a cascading immune response are profoundly limited by hypoxia and a weakened immune response. Intravenous and intratumoral injection of therapeutic drugs also cause pain, rapid drug clearance and low utilization rates. Here, a novel cryo-millineedle platform for intratumoral delivery of a phototherapy system, S.epi@IR820, is developed in this work, combining the properties of Staphylococcus epidermidis (S. epidermidis) and IR820 for photo-immunotherapy of colorectal cancer. In this cryo-millineedle platform, S. epidermidis enhances the near-infrared absorption and light stability of IR820 and catalyzes the decomposition of H2O2 into O2 via an endogenous catalase to relieve tumor hypoxia, improve phototherapy and enhance immunogenic cell death (ICD). More interestingly, the native immunogenicity of S. epidermidis and ICD elicited by phototherapy achieved a potent anti-tumor immune response. To the best of our knowledge, this is the first study to utilize native S. epidermidis to relieve hypoxia and facilitate phototherapy. Both in vitro and in vivo experiments showed that the millineedle based phototherapy system can efficiently catalyse the decomposition of H2O2 into O2, facilitate phototherapeutic killing of CT26 tumor cells by S.epi@IR820 and enhance ICD, thus successfully activated the immune response and achieved the photo-immunotherapy against colorectal cancer. In conclusion, this study provides a novel strategy for enhanced anti-tumor efficiency of photo-immunotherapy, and develops an effective method for orthotopic administration of tumors.

PEGylation Can Effectively Strike a Balance in siRNA Delivery Performances of Guanidinylated Linear Synthetic Polypeptides with Potential Use for Transcriptional Gene Silencing

The prevailing design philosophy for polymeric vectors delivering siRNA is rooted in the post-transcriptional gene silencing (PTGS) mechanism. Yet, the transcriptional gene silencing (TGS) mechanism offers a potentially more durable silencing effect, which necessitates efficient siRNA delivery into the nucleus. However, it remains a challenge for the polymeric vectors to efficiently deliver siRNA into the nucleus. We have explored guanidinylated cyclic synthetic polypeptides (GCSPs) to enhance the nuclear delivery of siRNA, but an increased cytotoxicity and difficulty in producing the GCSPs on a large scale limit their utility. Herein, we simply prepare PEGylated guanidinylated linear synthetic polypeptides (PGLSPs) exhibiting improved membrane penetration, direct siRNA transport to the nucleus, reduced toxicity, high cellular uptake, and mitigation of protein corona formation. The PEGylation can effectively balance the vector's nuclear delivery capacity with other critical aspects of performances for siRNA delivery. Therefore, the PGLSPs hold promise as TGS-based delivery vectors, offering potential for future therapeutic applications.

Challenges and opportunities of poly(amino acid) nanomedicines in cancer therapy

Poly(amino acid) nanomedicines hold significant promise for cancer therapy. However, their clinical translation has not matched the extensive efforts of scientists or the burgeoning body of research. The therapeutic outcomes with most nanomedicines often fall short of the promising results observed in animal experiments. This review explores the challenges faced in cancer therapy using poly(amino acid) nanomedicines, particularly addressing the controversies surrounding the enhanced permeability and retention effect and the lack of methods for controlled and reproducible mass production of poly(amino acid) nanomedicines. Furthermore, this review examines the opportunities emerging in this field due to the rapid advancements in artificial intelligence.

Design of Auto-Adaptive Drug Delivery System for Effective Delivery of Peptide Drugs to Overcoming Mucus and Epithelial Barriers

Oral administration of peptide represents a promising delivery route, however, it is hindered by the harsh gastrointestinal environment, leading to low in vivo absorption. In this study, auto-adaptive protein corona-AT 1002-cationic liposomes (Pc-AT-CLs) are constructed with the characteristic of hydrophilic and electrically neutral surface properties for the encapsulation of liraglutide. BSA protein corona is used to coat AT-CLs reducing the adherence of mucus, and may fall off after penetrating the mucus layer. Transmucus transport experiment demonstrated that the mucus penetration amount of Pc-AT-CLs are 1.45 times that of AT-CLs. After penetrating the mucus layer, AT-CLs complete transmembrane transport by the dual action of AT and cationic surface properties. Transmembrane transport experiment demonstrated that the apparent permeability coefficient (Papp) of AT-CLs is 2.03 times that of CLs. In vivo tests demonstrated that Pc-AT-CLs exhibited a significant hypoglycemic effect and enhanced the relative bioavailability comparing to free liraglutide. Pc-AT-CLs protect liraglutide from degradation, facilitate its absorption, and ultimately improve its oral bioavailability.

Poly(phenylalanine) and poly(3,4-dihydroxy-L-phenylalanine): Promising biomedical materials for building stimuli-responsive nanocarriers

Cancer is a serious threat to human health because of its high annual mortality rate. It has attracted significant attention in healthcare, and identifying effective strategies for the treatment and relief of cancer pain requires urgency. Drug delivery systems (DDSs) offer the advantages of excellent efficacy, low cost, and low toxicity for targeting drugs to tumor sites. In recent decades, copolymer carriers based on poly(phenylalanine) (PPhe) and poly(3,4-dihydroxy-L-phenylalanine) (PDopa) have been extensively investigated owing to their good biocompatibility, biodegradability, and controllable stimulus responsiveness, which have resulted in DDSs with loading and targeted delivery capabilities. In this review, we introduce the synthesis of PPhe and PDopa, highlighting the latest proposed synthetic routes and comparing the differences in drug delivery between PPhe and PDopa. Subsequently, we summarize the various applications of PPhe and PDopa in nanoscale-targeted DDSs, providing a comprehensive analysis of the drug release behavior based on different stimulus-responsive carriers using these two materials. In the end, we discuss the challenges and prospects of polypeptide-based DDSs in the field of cancer therapy, aiming to promote their further development to meet the growing demands for treatment.

Nanotechnology-empowered combination therapy for rheumatoid arthritis: principles, strategies, and challenges

Rheumatoid arthritis (RA) is an autoimmune disease with multifactorial etiology and intricate pathogenesis. In RA, repeated monotherapy is frequently associated with inadequate efficacy, drug resistance, and severe side effects. Therefore, a shift has occurred in clinical practice toward combination therapy. However, conventional combination therapy encounters several hindrances, including low selectivity to arthritic joints, short half-lives, and varying pharmacokinetics among coupled drugs. Emerging nanotechnology offers an incomparable opportunity for developing advanced combination therapy against RA. First, it allows for co-delivering multiple drugs with augmented physicochemical properties, targeted delivery capabilities, and controlled release profiles. Second, it enables therapeutic nanomaterials development, thereby expanding combination regimens to include multifunctional nanomedicines. Lastly, it facilitates the construction of all-in-one nanoplatforms assembled with multiple modalities, such as phototherapy, sonodynamic therapy, and imaging. Thus, nanotechnology offers a promising solution to the current bottleneck in both RA treatment and diagnosis. This review summarizes the rationale, advantages, and recent advances in nano-empowered combination therapy for RA. It also discusses safety considerations, drug-drug interactions, and the potential for clinical translation. Additionally, it provides design tips and an outlook on future developments in nano-empowered combination therapy. The objective of this review is to achieve a comprehensive understanding of the mechanisms underlying combination therapy for RA and unlock the maximum potential of nanotechnology, thereby facilitating the smooth transition of research findings from the laboratory to clinical practice.

Bioactive poly(amino acid)s for multi-modal cancer therapy

The interplay between the tumor cells and their microenvironments is as inseparable as the relationship between "seeds" and "soil." The tumor microenvironments (TMEs) exacerbate malignancy by enriching malignant cell subclones, generating extracellular matrices, and recruiting immunosuppressive cells, thereby diminishing the efficacy of clinical therapies. Modulating TMEs has emerged as a promising strategy to enhance cancer therapy. However, the existing drugs used in clinical settings do not target the TMEs specifically, underscoring the urgent need for advanced strategies. Bioactive materials present unique opportunities for modulating TMEs. Poly(amino acid)s with precisely controllable structures and properties offer exceptional characteristics, such as diverse structural units, excellent biosafety, ease of modification, sensitive biological responsiveness, and unique secondary structures. These attributes hold significant potential for the modulation of TMEs and clinical applications further. Consequently, developing bioactive poly(amino acid)s capable of modulating the TMEs by elucidating structure-activity relationships and mechanisms is a promising approach for innovative clinical oncology therapy. This review summarizes the recent progress of our research team in developing bioactive poly(amino acid)s for multi-modal tumor therapy. First, a brief overview of poly(amino acid) synthesis and their advantages as nanocarriers is provided. Subsequently, the pioneering research of our research group on synthesizing the biologically responsive, dynamically allosteric, and immunologically effective poly(amino acid)s are highlighted. These poly(amino acid)s are designed to enhance tumor therapy by modulating the intracellular, extracellular matrix, and stromal cell microenvironments. Finally, the future development of poly(amino acid)s is discussed. This review will guide and inspire the construction of bioactive poly(amino acid)s with promising clinical applications in cancer therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Peptide-Based Structures.

Polypeptide- and Protein-Based Conjugate Nanoparticles via Aqueous Ring-Opening Polymerization-Induced Self-Assembly (ROPISA)

Protein-polymer conjugates and polymeric nanomaterials hold great promise in many applications including biomaterials, medicine, or nanoelectronics. In this work, the first polymerization-induced self-assembly (PISA) approach performed in aqueous medium enabling protein-polymer conjugates and nanoparticles entirely composed of amino acids is presented by using ring-opening polymerization (ROP). It is indeed shown that aqueous ring-opening polymerization-induced self-assembly (ROPISA) can be used with protein or peptidic macroinitiators without prior chemical modification and afford the simple preparation of nanomaterials with protein-like property, for example, to implement biomimetic thermoresponsivity in drug delivery.

Synthetic Polypeptide Bioadhesive Based on Cation-π Interaction and Secondary Structure

Bioadhesives have garnered widespread attention in the biomedical field, for wound healing and tissue sealing. However, challenges exist due to the inferior performance of bioadhesives, including weak adhesion, poor biocompatibility, or lack of biodegradability. In this work, we demonstrate the fabrication of hydrogel adhesive based on polypeptides composed of lysine and glutamic acid. The cation-π interaction between the ammonium cations and phenyl groups endows the hydrogel with strong cohesion, and the hydrophobicity of the phenyl group significantly enhances the interaction between polypeptides and the substrate interface, leading to excellent adhesive performance. The equivalent molar ratio of ammonium cations and the phenyl group is beneficial for the enhancement of adhesiveness. Furthermore, we discover that the polypeptides with an α-helix exhibit better adhesiveness than the polypeptides with a β-sheet because the α-helical structure can increase the exposure of the side group on the polypeptide surface, which further strengthens the interaction between polypeptides and the substrate. Besides, this synthetic polypeptide adhesive can seal the tissue quickly and remain intact in water. This adhesive holds significant promise for application in wound healing and tissue sealing, and this study provides insight into the development of more peptide-based adhesives.

Facile Synthesis of High Molecular Weight Poly(ethylene glycol)-b-poly(amino acid)s by Relay Polymerization

Poly(amino acid)s (PAAs) are one kind of favorable biopolymer that can be used as a drug or gene carrier. However, conventional ring-opening polymerization of PAAs is slow and needs a strict anhydrous environment with an anhydrous reagent as well as the product without enough high molecular weight (Mn), which limits the expanding of PAAs' application. Herein, we took BLG-NCA as the monomer to quickly synthesize one kind of high Mn amphiphilic copolymer, poly(ethylene glycol)-b-poly(γ-benzyl-l-glutamic acid) (PEG-PBLG), by relay polymerization with a simple one-pot method within 3 h in mild conditions (open air, moisture insensitive). In the polymerization process, ring-opening polymerization-induced self-assembly in sodium bicarbonate aqueous solution first occurred to obtain low Mn PEG-PBLG seeds without purification. Then γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA) dichloromethane solution was added into PEG-PBLG seeds directly and stirred vigorously to form am emulsion; during this process, the amphiphilic PEG-PBLG seeds will anchor on the interface of DCM and water to ensure the concentration of α-helix rigid PBLG in DCM to maintain the following relay polymerization. Then, high Mn PEG-PBLG was obtained in mild conditions in one pot. We found that the α-helix rigid structure was essential for relay polymerization by studying the synthetic speed of amphiphilic copolymer with different secondary structures. MOE simulation results showed that PBLG and BLG-NCA tended to form a double hydrogen bond, which was beneficial to relay polymerization because of higher local concentrations that can produce more double hydrogen bonds. Our strategy can quickly obtain high Mn PEG-PBLG (224.9 KDa) within 3 h from PEG-NH2 and BLG-NCA in one pot and did not need an extra initiator. After deprotection, the poly(ethylene glycol)-b-poly(l-glutamate acid) (PEG-PGA) with high Mn as a second product can be used as an excellent antitumor drug carrier. The high Mn PEG-PGA can achieve an encapsulation rate of 86.7% and a drug loading rate of 47.3%, which is twice that of the low Mn PEG-PGA. As a result, the synthesis of PEG-PBLG by relay polymerization simplified the process of PEG-PAA polymerization and increased the Mn. In addition, this method opened a way to obtain other kinds of high Mn PEG-PBLG values in the future.

Application of graphene oxide in tumor targeting and tumor therapy

Graphene oxide (GO), as a kind of two-dimensional sp2 carbon nanomaterials, has attracted great attention in many fields in the past decade. Due to its unique physical and chemical properties, GO is showing great promise in the field of biomedicine. For GO, all the atoms on its surface are exposed to the surface with ultra-high specific surface area, and a variety of groups on the surface, such as carboxyl, hydroxyl and epoxy groups, can effectively bind/load various biomolecules. Due to the availability of these groups, GO also possesses excellent hydrophilicity and biocompatibility for the modification of the desired biocompatible molecules or polymers on the surface of GO. The nano-network structure and hydrophobicity of GO enable it to load a large number of hydrophobic drugs containing benzene rings and it has been widely used as a multi-functional nano-carrier for chemotherapeutic drug or gene delivery. This review article will give an in-depth overview of the synthesis methods of GO, the advantages and disadvantages of GO used in nano-drug delivery system, the research progress of GO as a stimulus-responsive nano-drug carrier, and the application of these intelligent systems in cancer treatment.

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

Biocompatible Polymer-Modified Nanoplatform for Ferroptosis-Enhanced Combination Cancer Therapy

Ferroptosis is a novel type of iron-dependent non-apoptotic pathway that regulates cell death and shows unique mechanisms including causing lipid peroxide accumulation, sensitizing drug-resistant cancers, priming immunity by immunogenic cell death, and cooperatively acting with other anticancer modalities for eradicating aggressive malignancies and tumor relapse. Recently, there has been a great deal of effort to design and develop anticancer biocompatible polymeric nanoplatforms including polypeptide and PEGylated ones to achieve effective ferroptosis therapy (FT) and synergistic combination therapies including chemotherapy (CT), photodynamic therapy (PDT), sonodynamic therapy (SDT), photothermal therapy (PTT), gas therapy (GT) including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2 S), and immunotherapy (IT). To be noted, the combo therapies such as FT-CT, FT-PTT, FT-GT, and FT-IT are attracting much efforts to fight against intractable and metastatic tumors as they can generate synergistic antitumor effects and immunogenic cell death (ICD) effects or modulate immunosuppressive tumor microenvironments to initiate strong antitumor immunity and memory effects. The polymeric Fenton nano-agents with good biosafety and high anticancer efficacy will provide a guarantee for their applications. In this review, various biocompatible polymer-modified nanoplatforms designed for FT and combo treatments are summarized for anticancer therapies and discussed for potential clinical transitions.

Paclitaxel prodrug-encapsulated polypeptide micelles with redox/pH dual responsiveness for cancer chemotherapy

Polypeptides are a highly promising carrier for delivering hydrophobic drugs, due to their excellent biocompatibility, non-toxicity, and non-immunogenicity. Herein, a redox and pH dual-responsive poly(ethylene glycol)-SS-b-polypeptide micelles encapsulated with disulfide bridged paclitaxel-pentadecanoic acid prodrug was developed for cancer chemotherapy. First of all, disulfide bridged paclitaxel-pentadecanoic acid prodrug (PTX-SS-COOH) and poly(ethylene glycol)-SS-b-polylysine-b-polyphenylalanine (mPEG-SS-b-PLys-b-PPhe, ESLP) were synthesized and confirmed via NMR, MS, FT-IR or GPC. After that, PTX-SS-COOH (PSH) embedded mPEG-SS-b-PLys-b-PPhe (ESLP/PSH) micelles were prepared by mixing method based on electrostatic interactions and hydrophobic forces. For comparison, mPEG-b-PLys-b-PPhe (ELP) was mixed with PTX-SS-COOH to generate another kind of micelles (ELP/PSH). The characterization of ESLP/PSH micelles through dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed a spherical structure with a diameter of approximately 170 nm. It is noteworthy that ESLP/PSH micelles displayed a high drug-loading rate of 22.84%, and excellent stability, which can be attributed to the specific interactions between the prodrug and copolymer. Drug release analysis demonstrated that the micelles exhibited a substantial release of PTX in the presence of GSH at pH 5.0, indicating a pH and redox dual responsiveness. In vivo pharmacokinetic study revealed the ESLP/PSH micelles had increased bioavailability and an extended circulation time. Ultimately, antitumor efficacy and systemic toxicity evaluation in 4 T1 tumor-bearing mice confirmed that ESLP/PSH micelles achieved the highest level of tumor growth inhibition (ca. 83%) and the lowest systemic toxicity in comparison with ELP/PSH micelles and commercialized Taxol®. Taken together, the dual responsive micelles represent a promising PTX formulation with potential clinical application in cancer chemotherapy.

Dual drug loaded polypeptide delivery systems for cancer therapy

The present study was aimed to prepare and examine in vitro novel dual-drug loaded delivery systems. Biodegradable nanoparticles based on poly(L-glutamic acid-co-D-phenylalanine) were used as nanocarriers for encapsulation of two drugs from the paclitaxel, irinotecan, and doxorubicin series. The developed delivery systems were characterised with hydrodynamic diameters less than 300 nm (PDI < 0.3). High encapsulation efficiencies (≥75%) were achieved for all single- and dual-drug formulations. The release studies showed faster release at acidic pH, with the release rate decreasing over time. The release patterns of the co-encapsulated forms of substances differed from those of the separately encapsulated drugs, suggesting differences in drug-polymer interactions. The joint action of encapsulated drugs was analysed using the colon cancer cells, both for the dual-drug delivery sytems and a mixture of single-drug formulations. The encapsulated forms of the drug combinations demonstrated comparable efficacy to the free forms, with the encapsulation enhancing solubility of the hydrophobic drug paclitaxel.

Rational design and engineering of polypeptide/protein vesicles for advanced biological applications

Synthetic vesicles have gained considerable popularity in recent years for numerous biological and medical applications. Among the various types of synthetic vesicles, the utilization of polypeptides and/or proteins as fundamental constituents has garnered significant interest for vesicle construction owing to the unique bio-functionalities inherent in rationally designed amino acid sequences. Especially the incorporation of functional proteins onto the vesicle surface facilitates a wide range of advanced biological applications that are not easily attainable with traditional building blocks, such as lipids and polymers. The main goal of this review is to provide a comprehensive overview of the latest advancements in polypeptide/protein vesicles. Moreover, this review encompasses the rational design and engineering strategies employed in the creation of polypeptide/protein vesicles, including the synthesis of building blocks, the modulation of their self-assembly, as well as their diverse applications. Furthermore, this work includes an in-depth discussion of the key challenges and opportunities associated with polypeptide/protein vesicles, providing valuable insights for future research. By offering an up-to-date review of this burgeoning field of polypeptide/protein vesicle research, this review will shed light on the potential applications of these biomaterials.

Secondary Structure in Overcoming Photosensitizers' Aggregation: α-Helical Polypeptides for Enhanced Photodynamic Therapy

Aggregation caused quenching (ACQ) effect can severely inhibit the application of hydrophobic photosensitizers (PSs) bearing planar and rigid structures. Most of the reported cases utilized random-coiled polymers for the in vivo delivery of PSs, which would inevitably aggravate ACQ effect due to the flexible chains. In this work, the role of polymers' secondary structures (especially α-helical conformation) in overcoming the PSs' aggregation is systemically investigated based on the design of α-helical polypeptides bearing tetraphenylporphyrin (TPP) side chains. Atomistic molecular dynamics simulation, fluorescence quantum yield, and reactive oxygen species (ROS) generation yield are evaluated to demonstrate that α-helical polypeptide backbones can significantly boost both fluorescence quantum yield and ROS by suppressing the π-π stacking interaction between TPP units. The enhanced in vitro and in vivo phototoxicity for helical polypeptides also reveal functions of secondary structures in inhibiting ACQ and improving the membrane activity. Successful in vivo photodynamic therapy (PDT) results in mice bearing H22 tumors showed great potentials for further clinical applications.

Functional hydrogels for the repair and regeneration of tissue defects

Tissue defects can be accompanied by functional impairments that affect the health and quality of life of patients. Hydrogels are three-dimensional (3D) hydrophilic polymer networks that can be used as bionic functional tissues to fill or repair damaged tissue as a promising therapeutic strategy in the field of tissue engineering and regenerative medicine. This paper summarises and discusses four outstanding advantages of hydrogels and their applications and advances in the repair and regeneration of tissue defects. First, hydrogels have physicochemical properties similar to the extracellular matrix of natural tissues, providing a good microenvironment for cell proliferation, migration and differentiation. Second, hydrogels have excellent shape adaptation and tissue adhesion properties, allowing them to be applied to a wide range of irregularly shaped tissue defects and to adhere well to the defect for sustained and efficient repair function. Third, the hydrogel is an intelligent delivery system capable of releasing therapeutic agents on demand. Hydrogels are capable of delivering therapeutic reagents and releasing therapeutic substances with temporal and spatial precision depending on the site and state of the defect. Fourth, hydrogels are self-healing and can maintain their integrity when damaged. We then describe the application and research progress of functional hydrogels in the repair and regeneration of defects in bone, cartilage, skin, muscle and nerve tissues. Finally, we discuss the challenges faced by hydrogels in the field of tissue regeneration and provide an outlook on their future trends.

In Vivo Anchoring Bis-Pyrene Probe for Molecular Imaging of Early Gastric Cancer by Endoscopic Techniques

With the development of blue laser endoscopy (BLE) technique, it's often used to diagnose early gastric cancer (EGC) by the morphological changes of blood vessels through BLE. However, EGC is still not obvious to identify, resulting in a high rate of missed diagnosis. Molecular imaging can show the changes in early tumors at molecular level, which provides a possibility for diagnosing EGC. Therefore, developing a probe that visually monitors blood vessels of EGC under BLE is particularly necessary. Herein, a bis-pyrene (BP) based nanoprobe (BP-FFVLK-(PEG)-RGD, M1 ) is designed, which can target angiogenesis and self-assemble into fibers in situ, resulting in stable and long-term retention in tumor. Moreover, M1 probe can emit yellow-green fluorescence for imaging under BLE. M1 probe is confirmed to steadily remain in tumor for up to 96 hours in mice transplanted subcutaneously. In addition, the M1 probe is able to target angiogenesis for molecular imaging of isolated human gastric cancer tissue under BLE. Finally, M1 probe i.v. injected into primary gastric cancer model rabbits successfully highlighted the tumor site under BLE, which is confirmed by pathological analysis. It's the first time to develop a probe for diagnosing EGC by visualizing angiogenesis under BLE, showing great clinical significance.

A fluorescent nano vector for early diagnosis and enhanced Interleukin-33 therapy of thoracic aortic dissection

Thoracic aortic dissection (TAD) is the most devastating complication of vascular disease. The accuracy of the clinical diagnosis and treatment of TAD at the early stage is still limited. Herein, we report a nano-delivery strategy for early diagnosis and the first case of interleukin-33 (IL-33) based therapy for the effective intervention of TAD. A targeted fluorescent nano vector (FNV) is designed to co-assemble with IL-33, which protects IL-33 and prolongs its half-life. With specific targeting ability to the thoracic aorta, FNV can diagnose TAD at its early stage through fluorescent imaging. FNV@IL-33 nanocomplex presents better therapeutic effects on mice TAD progression compared with that of IL-33 alone by reducing smooth muscle apoptosis. Administration of FNV@IL-33 two weeks before onset, the development of TAD is greatly intervened. Our study provides a novel approach for early diagnosis and effective IL-33 therapy of TAD, which opens attractive opportunities for clinical prevention of cardiovascular diseases.

Bio-Inspired Drug Delivery Systems: From Synthetic Polypeptide Vesicles to Outer Membrane Vesicles

Nanomedicine is a broad field that focuses on the development of nanocarriers to deliver specific drugs to targeted sites. A synthetic polypeptide is a kind of biomaterial composed of repeating amino acid units that are linked by peptide bonds. The multiplied amphiphilicity segment of the polypeptide could assemble to form polypeptide vesicles (PVs) under suitable conditions. Different from polypeptide vesicles, outer membrane vesicles (OMVs) are spherical buds of the outer membrane filled with periplasmic content, which commonly originate from Gram-negative bacteria. Owing to their biodegradability and excellent biocompatibility, both PVs and OMVs have been utilized as carriers in delivering drugs. In this review, we discuss the recent drug delivery research based on PVs and OMVs. These related topics are presented: (1) a brief introduction to the production methods for PVs and OMVs; (2) a thorough explanation of PV- and OMV-related applications in drug delivery including the vesicle design and biological assessment; (3) finally, we conclude with a discussion on perspectives and future challenges related to the drug delivery systems of PVs and OMVs.

A drug delivery system constructed by a fusion peptide capturing exosomes targets to titanium implants accurately resulting the enhancement of osseointegration peri-implant

BACKGROUND

Exosomes derived from bone marrow mesenchymal stem cells (BMSC-exos) have been shown triggering osteogenic differentiation and mineralization of MSCs, but exosomes administered via bolus injections are rapidly sequestered and cleared. Therefore, we considered the implant as a new organ of patient's body and expected to find a method to treat implant with BMSC-exos in vivo directly.

METHODS

A fusion peptide (PEP), as a drug delivery system (DDS) which contained a titanium-binding peptide (TBP) possessing the ability to selectively bind to the titanium surface and another peptide CP05 being able to capture exosomes expertly, is constructed to modify the titanium surface.

RESULTS

Both in vitro and in vivo experiments prove PEP retains the ability to bind titanium and exosome simultaneously, and the DDS gain the ability to target exosomes to titanium implants surface following enhancing osseointegration post-implantation. Moreover, the DDS constructed by exosomes of diverse origins shows the similar combination rate and efficiency of therapy.

CONCLUSION

This drug delivery system demonstrates the concept that EXO-PEP system can offer an accurate and efficient therapy for treating implants with long-term effect.

Peptide–Polymer Conjugates: A Promising Therapeutic Solution for Drug-Resistant Bacteria

By 2050, it is estimated that 10 million people will die of drug-resistant bacterial infection caused by antibiotic abuse. Antimicrobial peptide (AMP) is widely used to prevent such circumstances, for the positively charged AMPs can kill drug-resistant bacteria by destroying negatively charged bacterial cell membrane, and has excellent antibacterial efficiency and low drug resistance. However, due to the defects in low in vivo stability, easy degradation, and certain cytotoxicity, its practical clinical application is limited. The emergence of peptide–polymer conjugates (PPC) helps AMPs overcome these shortcomings. By combining with functional polymers, the positive charge of AMPs is partially shielded, and its stability and water solubility are improved, so as to prolong the in vivo circulation time of AMPs and reduce its cytotoxicity. At the same time, the self-assembly ability of PPC enables it to assemble into different nanostructures to undertake specific antibacterial tasks. At present, PPC is mainly used in wound dressing, bone tissue repair, antibacterial coating of medical devices, nerve repair, tumor treatment, and oral health maintenance. In this study, we summarize the structure, synthesis methods, and the clinical applications of PPC, so as to present the current challenges and discuss the future prospects of antibacterial therapeutic materials.

Intelligent poly(l-histidine)-based nanovehicles for controlled drug delivery

Stimuli-responsive drug delivery systems based on polymeric nanovehicles are among the most promising treatment regimens for malignant cancers. Such intelligent systems that release payloads in response to the physiological characteristics of tumor sites have several advantages over conventional drug carriers, offering, in particular, enhanced therapeutic effects and decreased toxicity. The tumor microenvironment (TME) is acidic, suggesting the potential of pH-responsive nanovehicles for enhancing treatment specificity and efficacy. The synthetic polypeptide poly(l-histidine) (PLH) is an appropriate candidate for the preparation of pH-responsive nanovehicles because the pK_a of PLH (approximately 6.0) is close to the pH of the acidic TME. In addition, the pendent imidazole rings of PLH yield pH-dependent hydrophobic-to-hydrophilic phase transitions in the acidic TME, triggering the destabilization of nanovehicles and the subsequent release of encapsulated chemotherapeutic agents. Herein, we highlight the state-of-the-art design and construction of pH-responsive nanovehicles based on PLH and discuss the future challenges and perspectives of this fascinating biomaterial for targeted cancer treatment and "benchtop-to-clinic" translation.

Solid-Phase Peptide Synthesis Using a Four-Dimensional (Safety-Catch) Protecting Group Scheme

Peptides of importance to both academia and industry are mostly synthesized in the solid-phase mode using a two-dimensional scheme. The so-called Fmoc/tBu strategy, where the groups are removed by piperidine and TFA, respectively, is currently the method of choice for peptide synthesis. However, as the molecular diversity of cyclic and branched peptides becomes a challenging interest, a high level of orthogonal dimensionality is required, such as through triorthogonal protection schemes. Here we present a fourth category of orthogonal protecting groups that are stable under cleavage conditions, including the TFA treatment that removes the tBu-based groups. At the end of the synthetic process and upon some chemical manipulation, the groups in this fourth category were removed with TFA. This new concept of protecting groups could facilitate the synthesis and manipulation of difficult peptides.

Thermoresponsive Glycopolypeptide Containing Block Copolymers, Particle Formation, and Lectin Interaction

Amphiphilic block copolymers with a thermoresponsive poly(N-isopropylacrylamide) block and a glycopeptide block are synthesized and particle formation as well as interaction of the glyco-corona with lectins is investigated. The synthetic route comprises the preparation of block copolymers by N-carboxyanhydride polymerization and subsequent deprotection to obtain pH- and thermoresponsive poly(l-glutamic acid)-b-poly(N-isopropylacrylamide) (pGA-b-pNIPAM), which is then further modified with different amino sugars by a versatile coupling method with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholin-4-ium chloride (DMT-MM). The glycosylated pGA-b-pNIPAM block copolymers are investigated with regard to cloud point temperatures (T_cp ), particle size, and stability. The morphology of the particles is visualized using cryo-SEM. Zeta potential measurements are indicating that the saccharide moieties are located on the surface of the particles. This assumption is further substantiated by quantitative lectin interaction assays with nonaggregated and aggregated glycosylated pGA-b-pNIPAM. The interaction of the model lectin ConA with the block copolymers is independent of the degree of substitution in the nonaggregated state at room temperature. However, at 37 °C, when particles of pGA-b-pNIPAM are present, the interaction becomes stronger with increasing degree of substitution. This interaction with lectins can be used for targeting saccharide-modified particles in drug delivery.

Recent advances in post-polymerization modifications on polypeptides: synthesis and applications

Polypeptides, a kind of very promising biomaterial, have shown a wide range of applications due to their excellent biocompatibility, easy accessibility, and structural variability. To synthesize polypeptides with desired functions, post-polymerization modification (PPM) plays an important role in introducing novel chemical structure on their side-chains. The key of PPM strategy is to develop highly selective and efficient reactions that can couple the additional functional moieties with pre-installed side-chain functionalities on polypeptides. In this minireview, classic PPM reactions and especially their recent progresses are summarized, including different modification approaches for unsaturated alkyl group, oxygen-containing functional group, nitrogen-containing functional group, sulfur-containing functional group and other special functional group on side chains. In addition, this review also highlights the applications of structure-diversified polypeptides generated via PPM strategy in the field of biomaterial.

ROS-Responsive Selenopolypeptide Micelles: Preparation, Characterization, and Controlled Drug Release

Sulfur-containing polypeptides, capable of reactive oxygen species (ROS)-responsive structural change, are one of the most important building blocks for the construction of polypeptide-based drug delivery systems. However, the relatively low ROS sensitivity of side-chain thioethers limits the biomedical applications of these polypeptides because they usually require a high concentration of ROS beyond the pathological ROS level in the tumor microenvironment. Herein, we report the design and synthesis of a selenium-containing polypeptide, which undergoes random coil-to-extended helix and hydrophobic-to-hydrophilic transitions in the presence of 0.1% H₂O₂, a concentration that is much lower than the ROS requirement for thioether. ROS-responsive micelles were thus prepared from the amphiphilic copolymer consisting of the hydrophilic poly(ethylene glycol) (PEG) segment and hydrophobic selenopolypeptide segment and were used to encapsulate doxorubicin (DOX). The micelles could be sensitively dissociated inside tumor cells in consequence of ROS-triggered oxidation of side-chain selenoether and structural change of the micelles, thereby efficiently and selectively releasing the encapsulated DOX to kill cancer cells. This work provides an alternative design of ROS-responsive polypeptides with higher sensitivity than that of the existing sulfur-containing polypeptides, which may expand the biomedical applications of polypeptide materials.

Syntheses of Polypeptides and Their Biomedical Application for Anti-Tumor Drug Delivery

Polypeptides have attracted considerable attention in recent decades due to their inherent biodegradability and biocompatibility. This mini-review focuses on various ways to synthesize polypeptides, as well as on their biomedical applications as anti-tumor drug carriers over the past five years. Various approaches to preparing polypeptides are summarized, including solid phase peptide synthesis, recombinant DNA techniques, and the polymerization of activated amino acid monomers. More details on the polymerization of specifically activated amino acid monomers, such as amino acid N-carboxyanhydrides (NCAs), amino acid N-thiocarboxyanhydrides (NTAs), and N-phenoxycarbonyl amino acids (NPCs), are introduced. Some stimuli-responsive polypeptide-based drug delivery systems that can undergo different transitions, including stability, surface, and size transition, to realize a better anti-tumor effect, are elaborated upon. Finally, the challenges and opportunities in this field are briefly discussed.

Stimuli-responsive polypeptides for controlled drug delivery

Controlled drug delivery systems, which could release loaded therapeutics upon physicochemical changes imposed by physiological triggers in the desired zone and during the required period of time, offer numerous advantages over traditional drug carriers including enhanced therapeutic effects and reduced toxicity. A polypeptide is a biocompatible and biodegradable polymer, which can be conveniently endowed with stimuli-responsiveness by introducing natural amino acid residues with innate stimuli-responsive characteristics or introducing responsive moieties to its side chains using simple conjugating methods, rendering it an ideal biomedical material for controlled drug delivery. This feature article summarizes our recent work and other relevant studies on the development of polypeptide-based drug delivery systems that respond to single or multiple physiological stimuli (e.g., pH, redox potential, glucose, and hypoxia) for controlled drug delivery applications. The material designs, synthetic strategies, loading and controlled-release mechanisms of drugs, and biomedical applications of these stimuli-responsive polypeptides-based drug delivery systems are elaborated. Finally, the challenges and opportunities in this field are briefly discussed.