Bottlebrush Polymer-Conjugated Melittin Exhibits Enhanced Antitumor Activity and Better Safety Profile

Arginine N-glycosylation of melittin enhances its bacteriostatic activity and antiproliferative therapeutic index

Melittin is a natural antimicrobial peptide isolated from bee venom, and the non-specific cytotoxicity and hemolytic activity severely limit its clinical application. Glycosylation of proteins is very common in physiological and biochemical processes and can modulate the interaction of proteins with their target. In this study, eight glycosyl groups were used to modify the arginine of melittin at sites 22 and/or 24, and single and double arginine N-glycosylated peptides were designed and synthesized. Among the acquired 24 glycopeptides, MLT-1c, MLT-3c, MLT-1f, MLT-3f, MLT-1g, and MLT-3h were found to possess higher helicity, while MLT-3c, MLT-3f and MLT-3h showed dramatically reduced hemolytic activity, especially MLT-3c, whose HC50 value is 199.3 μM. MLT-1a, MLT-3a and MLT-2c exhibited improved inhibitory activity against Puzza streptococcus, and the MIC was 4 μg mL-1. MLT-1e and MLT-2g have the strongest tolerance to trypsase, and MLT-3c has the highest therapeutic index. In general, rhamnosyl-modified melittin MLT-3c could be a potent agent for antibacterial and antitumor therapy with high stability and low hemolytic side effects.

Versatile and Controlled Synthesis of Degradable, Water-Soluble Bottlebrush Polymers with Poly(disulfide) Backbones Derived from α-Lipoic Acid

Bottlebrush (BB) polymers, with their densely grafted side chains and unique architecture, are highly advantageous for drug delivery due to their high functional group density for drug conjugation, unimolecular nature, and enhanced biodistribution properties. These attributes enable extended blood circulation half-life, improved tumor tissue penetration, and high tumoral drug accumulation. However, the typically nondegradable, all-carbon backbones of most BB polymers limit their suitability for applications requiring controlled clearance and biodegradability. To address this, we developed degradable BB polymers with poly(disulfide) backbones synthesized via reversible addition-fragmentation chain transfer (RAFT) copolymerization of α-lipoic acid (LA), a renewable and readily available compound, with acrylate-based inimers. These copolymers feature degradable backbones and initiating sites for subsequent BB synthesis. Using an atom transfer radical polymerization (ATRP) grafting-from methodology, we synthesized BB polymers with relatively low dispersities (Đ = 1.30-1.53), high backbone degrees of polymerization (DPbb), and high molar masses (Mn,MALS = 650-2700 kg/mol). The easily cleavable disulfide bonds enabled backbone degradation under mild reducing conditions. Beyond hydrophilic BB with tri(ethylene glycol) methyl ether acrylate (TEGA) side chains, we synthesized BB with cationic, anionic, and zwitterionic side chains, demonstrating broad monomer compatibility. This scalable approach produces water-soluble, degradable BB polymers with tunable architectures and predictable molecular weights. By addressing the need for degradability in BB polymers, this work advances their potential for drug delivery, offering enhanced functionality, biocompatibility, and sustainability.

Tuning mucoadhesion and mucopenetration in self-assembled poly(lactic acid)-block-poly(oligoethylene glycol methacrylate) block copolymer nanoparticles by controlling side-chain lengths

The capacity to tune the degree of mucoadhesion and mucopenetration of nanoparticles is essential to improving drug bioavailability, transport, and efficacy at mucosal interfaces. Herein, self-assembled nanoparticles (NPs) fabricated from amphiphilic block copolymers of poly(lactic acid) (PLA) and poly(oligo(ethylene glycol) methacrylate) (POEGMA) with various side chain lengths (PLA-POEGMAn) are reported to facilitate tunable mucosal interactions. PLA-POEGMAn nanoparticles with long PEG side chain lengths (n = 20, or 40) demonstrated mucoadhesive properties based on rheological synergism, calorimetric tracking of mucin-nanoparticle interactions, and the formation of larger NP-mucin hybrid structures; in contrast, NPs fabricated from block copolymers with shorter PEG side chains (n = 2/8-9 or n = 8,9) showed poor mucoadhesion but penetrated through the mucin layer with significantly higher permeation rates (>80%). All NP formulations showed good cytocompatibility (viability > 70%) with human corneal epithelial cells in vitro and no detectable acute in vivo ocular irritation in Sprague-Dawley rats. Coupled with the capacity of the synthetic route to easily incorporate different brush lengths and/or different functional groups into the hydrophilic block, we anticipate this approach may offer a solution in applications in which balancing mucoadhesion and mucopenetration is critical for enabling effective drug delivery.

Targeting the Skin: The Study of a Bottlebrush Polymer-Antisense Oligonucleotide Conjugate in a Psoriasis Mouse Model

The investigation of gene regulation therapeutics for the treatment of skin-related diseases is rarely explored in part due to inefficient systemic delivery. In this study, a bottlebrush polymer-antisense oligonucleotide (ASO) conjugate, termed pacDNA, designed to target IL-17 receptor A (IL-17RA), which is involved in psoriasis pathogenesis is presented. Systemic administration of pacDNA led to its accumulation in epidermis, dermis, and hypodermis of mouse skin, reduced IL-17RA gene expression in skin, and significantly reversed the development of imiquimod (IMQ)-induced psoriasis in a mouse model. These findings highlight the potential of the pacDNA as a promising nanoconstruct for systemic oligonucleotide delivery to the skin and for treating psoriasis and other skin-related disorders through systemic administration.

The therapeutic potential of bee venom-derived Apamin and Melittin conjugates in cancer treatment: A systematic review

The therapeutic potential of bee venom-derived peptides, particularly apamin and melittin, in cancer treatment has garnered significant attention as a promising avenue for advancing oncology. This systematic review examines preclinical studies highlighting the emerging role of these peptides in enhancing cancer therapies. Melittin and apamin, when conjugated with other therapeutic agents or formulated into novel delivery systems, have demonstrated improved efficacy in targeting tumor cells. Key findings indicate that melittin-based conjugates, such as polyethylene glycol (PEG)ylated versions, show potential in enhancing therapeutic outcomes and minimizing toxicity across various cancer models. Similarly, apamin-conjugated formulations have improved the efficacy of established anti-cancer drugs, contributing to enhanced targeting and reduced systemic toxicity. These developments underscore a growing interest in leveraging bee venom-derived peptides as adjuncts in cancer therapy. The integration of these peptides into treatment regimens offers a promising strategy to address current limitations in cancer treatment, such as drug resistance and off-target effects. However, comprehensive validation through clinical trials is essential to confirm their safety and effectiveness in human patients. This review highlights the global emergence of bee venom-derived peptides in cancer treatment, advocating for continued research and development to fully realize their therapeutic potential.

Melittin and phospholipase A2: Promising anti-cancer candidates from bee venom

As the research on cancer-related treatment deepens, integrating traditional therapies with emerging interventions reveals new therapeutic possibilities. Melittin and phospholipase A2, the primary anti-cancer components of bee venom, are currently gaining increasing attention. This article reviews the various formulations of melittin in cancer therapy and its potential applications in clinical treatments. The reviewed formulations include melittin analogs, hydrogels, adenoviruses, fusion toxins, fusion peptides/proteins, conjugates, liposomes, and nanoparticles. The article also explored the collaborative therapeutic effects of melittin with natural products, synthetic drugs, radiotherapy, and gene expression regulatory strategies. Phospholipase A2 plays a key role in bee venom anti-cancer strategy due to its unique biological activity. Using an extensive literature review and the latest scientific results, this paper explores the current state and challenges of this field, with the aim to provide new perspectives that guide future research and potential clinical applications. This will further promote the application of bee venom in cancer therapy.

Homologous-targeting biomimetic nanoparticles co-loaded with melittin and a photosensitizer for the combination therapy of triple negative breast cancer

Melittin (Mel) is considered a promising candidate drug for the treatment of triple negative breast cancer (TNBC) due to its various antitumor effects. However, its clinical application is hampered by notable limitations, including hemolytic activity, rapid clearance, and a lack of tumor selectivity. Here, we designed novel biomimetic nanoparticles based on homologous tumor cell membranes and poly(lactic-co-glycolic acid) (PLGA)/poly(beta-aminoester) (PBAE), denoted MDM@TPP, which efficiently coloaded the cytolytic peptide Mel and the photosensitizer mTHPC. Both in vitro and in vivo, the MDM@TPP nanoparticles effectively mitigated the acute toxicity of melittin and exhibited strong TNBC targeting ability due to the homologous targeting effect of the tumor cell membrane. Under laser irradiation, the MDM@TPP nanoparticles showed excellent photodynamic performance and thus accelerated the release of Mel by disrupting cell membrane integrity. Moreover, Mel combined with photodynamic therapy (PDT) can synergistically kill tumor cells and induce significant immunogenic cell death, thereby stimulating the maturation of dendritic cells (DCs). In 4T1 tumor-bearing mice, MDM@TPP nanoparticles effectively inhibited the growth and metastasis of primary tumors and finally prevented tumor recurrence by improving the immune response.

Site-Specific Conjugation of Bottlebrush Polymers to Therapeutic Protein via Bioorthogonal Chemistry

Achieving efficient and site-specific conjugation of therapeutic protein to polymer is crucial to augment their applicability in the realms of biomedicine by improving their stability and enzymatic activity. In this study, we exploited tetrazine bioorthogonal chemistry to achieve the site-specific conjugation of bottlebrush polymers to urate oxidase (UOX), a therapeutic protein for gout treatment. An azido-functionalized zwitterionic bottlebrush polymer (N3-ZBP) using a "grafting-from" strategy involving RAFT and ATRP methods was synthesized, and a trans-cyclooctene (TCO) moiety was introduced at the polymer end through the strain-promoted azide-alkyne click (SPAAC) reaction. The subsequent coupling between TCO-incorporated bottlebrush polymer and tetrazine-labeled UOX using a fast and safe bioorthogonal reaction, inverse electron demand Diels-Alder (IEDDA), led to the formation of UOX-ZBP conjugates with a 52% yield. Importantly, the enzymatic activity of UOX remained unaffected following polymer conjugation, suggesting a minimal change in the folded structure of UOX. Moreover, UOX-ZBP conjugates exhibited enhanced proteolytic resistance and reduced antibody binding, compared to UOX-wild type. Overall, the present findings reveal an efficient and straightforward route for synthesizing protein-bottlebrush polymer conjugates without compromising the enzymatic activity while substantially reducing proteolytic degradation and antibody binding.

Enabling safer, more potent oligonucleotide therapeutics with bottlebrush polymer conjugates

Oligonucleotide therapeutics have the unique ability to address traditionally undruggable targets through various target engagement pathways. However, despite advances in chemically modified oligonucleotides and carrier-assisted delivery systems such as lipid nanoparticles and protein/peptide conjugates, the development of oligonucleotide drugs is still plagued with lackluster potency, narrow therapeutic window, poor delivery to non-liver target sites, and/or high potential for toxicity and unwanted immune system activation. In this perspective, we discuss an unconventional delivery solution based upon bottlebrush polymers, which overcomes many key challenges in oligonucleotide drug development. We address the molecular basis of the polymer's ability to enhance tissue bioavailability and drug potency, reduce side effects, and suppress anti-carrier immunity. Furthermore, we discuss the potential of the technology in advancing oligonucleotide-based therapies for non-liver targets.

Inhalable Bottlebrush Polymer Bioconjugates as Vectors for Efficient Pulmonary Delivery of Oligonucleotides

Antisense oligonucleotides hold therapeutic promise for various lung disorders, but their efficacy is limited by suboptimal delivery. To address this challenge, we explored the use of inhaled bottlebrush polymer-DNA conjugates, named pacDNA, as a delivery strategy. Inhaled pacDNA exhibits superior mucus penetration, achieving a uniform and sustained lung distribution in mice. Targeting the 5' splice site of an aberrant enhanced green fluorescence protein (EGFP) pre-mRNA in EGFP-654 mice, inhaled pacDNA more efficiently corrects splicing than a B-peptide conjugate and restores EGFP expression in the lung. Additionally, in an orthotopic NCI-H358 non-small-cell lung tumor mouse model, inhaled pacDNA targeting wild-type KRAS mRNA effectively suppresses KRAS expression and inhibits lung tumor growth, requiring a substantially lower dosage compared to intravenously injected pacDNA. These findings demonstrate the potential of bottlebrush polymer-DNA conjugates as a promising agent for enhanced oligonucleotide therapy in the lung and advancing the treatment landscape for lung disorders.

Recent advances in melittin-based nanoparticles for antitumor treatment: from mechanisms to targeted delivery strategies

As a naturally occurring cytolytic peptide, melittin (MLT) not only exhibits a potent direct tumor cell-killing effect but also possesses various immunomodulatory functions. MLT shows minimal chances for developing resistance and has been recognized as a promising broad-spectrum antitumor drug because of this unique dual mechanism of action. However, MLT still displays obvious toxic side effects during treatment, such as nonspecific cytolytic activity, hemolytic toxicity, coagulation disorders, and allergic reactions, seriously hampering its broad clinical applications. With thorough research on antitumor mechanisms and the rapid development of nanotechnology, significant effort has been devoted to shielding against toxicity and achieving tumor-directed drug delivery to improve the therapeutic efficacy of MLT. Herein, we mainly summarize the potential antitumor mechanisms of MLT and recent progress in the targeted delivery strategies for tumor therapy, such as passive targeting, active targeting and stimulus-responsive targeting. Additionally, we also highlight the prospects and challenges of realizing the full potential of MLT in the field of tumor therapy. By exploring the antitumor molecular mechanisms and delivery strategies of MLT, this comprehensive review may inspire new ideas for tumor multimechanism synergistic therapy.

A combination of genetically engineered oncolytic virus and melittin-CpG for cancer viro-chemo-immunotherapy

BACKGROUND

Immunotherapy has emerged as an efficient therapeutic approach for cancer management. However, stimulation of host immune system against cancer cells often fails to achieve promising clinical outcomes mainly owing to the immunosuppressive characteristics of the tumor microenvironment (TME). Combination therapeutics that can trigger sustained immunogenic cell death (ICD) have provided new opportunities for cancer treatment.

METHODS

In this study, we designed and applied an ICD inducer regimen, including a genetically engineered oncolytic virus (miRNA-modified coxsackieviruses B3, miR-CVB3), a pore-forming lytic peptide (melittin, found in bee venom), and a synthetic toll-like receptor 9 ligand (CpG oligodeoxynucleotides), for breast cancer and melanoma treatment. We compared the anti-tumor efficacy of miR-CVB3 and CpG-melittin (CpGMel) alone and in combination (miR-CVB3 + CpGMel) and investigated possible mechanisms involved.

RESULTS

We demonstrated that miR-CVB3 + CpGMel had no major impact on viral growth, while enhancing the cellular uptake of CpGMel in vitro. We further showed that combination therapy led to significant increases in tumor cell death and release of damage-associated molecular patterns compared with individual treatment. In vivo studies in 4T1 tumor-bearing Balb/c mice revealed that both primary and distant tumors were significantly suppressed, and the survival rate was significantly prolonged after administration of miR-CVB3 + CpGMel compared with single treatment. This anti-tumor effect was accompanied by increased ICD and immune cell infiltration into the TME. Safety analysis showed no significant pathological abnormalities in Balb/c mice. Furthermore, the developed therapeutic regimen also demonstrated a great anti-tumor activity in B16F10 melanoma tumor-bearing C57BL/6 J mice.

CONCLUSIONS

Overall, our findings indicate that although single treatment using miR-CVB3 or CpGMel can efficiently delay tumor growth, combining oncolytic virus-based therapy can generate even stronger anti-tumor immunity, leading to a greater reduction in tumor size.

A hydrogel dressing with tunable critical temperature and photothermal modulating melittin release for multiply antibacterial treatment

It is imperative to develop an antibiotic-free and long-term effective strategy for treating chronic wound infections due to the long-term utilization of antibiotics easily causing drug resistance. Herein, we fabricated a novel poly-N-isopropylacrylamide (PNIPAM)/polyacrylamide (PAM) coupling thermosensitive hydrogel integrating 1D lysozyme nanofiber doped with CuS nanoparticles (CuS/PP) and loading antibacterial peptide melittin (M) (CuS/PP-M) for combating chronic wound infection via photothermal modulating the release of melittin. For the CuS/PP-M hydrogel, the copolymerization of PNIPAM and PAM allows the lower critical solution temperature (LCST) higher than the body temperature, effectively hindering the spontaneous release of melittin when contacts the infected wound, while the integration of LNF/CuS nanofibers provides a stable photothermal treatment for triggering the release of melittin. As a result, the CuS/PP-M hydrogel exhibits synergistically enhanced effect on killing both Gram-positive and Gram-negative bacteria, which maintains more than 99 % bactericidal efficiency, even displays a long-term and multiply antibacterial performance by photothermal modulating melittin release. Moreover, the CuS/PP-M hydrogel presents both high antibacterial activity and excellent wound healing performance in the mouse wound model, thereby benefiting the chronic wound healing.

Recent advances in long-acting drug delivery systems for anticancer drug

The use of systemic anticancer chemotherapy is intrinsically limited by its toxicity. Whether dealing with small molecules or biopharmaceuticals, after systemic administration, small doses fail to reach effective intratumoral concentrations, while high doses with significant tumor inhibition effects may also drive the death of healthy cells, endangering the patients. Therefore, strategies based on drug delivery systems (DDSs) for avoiding the systemic toxicity have been designed. Due to their ability to protect drugs from early elimination and control drug release, DDSs can foster tumor exposure to anticancer therapeutics by extending their circulation time or steadily releasing drugs into the tumor sites. However, approval of tailored DDSs systems for clinical use is minimal as the safety and the in vivo activity still need to be ameliorated by manipulating their physicochemical characteristics. During the last few years, several strategies have been described to improve their safety, stability, and fine-tune pharmaceuticals release kinetics. Herein, we reviewed the main DDSs, namely polymeric conjugates, nano or microparticles, hydrogels, and microneedles, explored for long-acting anticancer treatments, highlighting recently proposed modifications and their potential advantages for different anticancer therapies. Additionally, important limitations of long-acting anticancer therapies and future technology directions were also covered.

Fluorination Effects on the Drug Delivery Property of Cylindrical Polymer Brushes

Fluorination has been widely applied to improving the properties of small-molecule drugs. However, relatively little is known about the effects of fluorination on the drug delivery property of nanomaterials. In this paper, we synthesized a fluoroalkane-modified cylindrical polymer brush (CPB) BCPB-F and an alkane-modified analogue BCPB-H. Doxorubicin (DOX) was used as a model drug and was loaded onto the CPBs through a pH-responsive acylhydrazone linkage. High drug loading and good water solubility were achieved. The in vitro and in vivo experiments suggested that fluorination played an important role in improving the cellular uptake, blood circulation, tissue permeability, and tumor targeting ability of CPBs. Due to these superiorities, the DOX-loaded BCPB-F exhibited excellent antitumor efficacy and eradicated the tumors of mice after five-dose treatments. The well-defined structures of the drug-free and drug-loaded CPBs guaranteed the accuracy of the results. This work demonstrates that fluorination is a promising strategy to improve the overall properties of nanomedicines.

Molecular polymer bottlebrushes in nanomedicine: therapeutic and diagnostic applications

Molecular polymer bottlebrushes are densely grafted, individual macromolecules with nanoscale proportions. The last decade has seen an increased focus on this material class, especially in nanomedicine and for biomedical applications. This Feature Article provides an overview of major developments in this area to highlight the many opportunities that these polymer architectures bring to nano-bio research. The article covers aspects of bottlebrush synthesis and summarises their use in drug and gene delivery, imaging, as theranostics and as prototype materials to correlate nanoparticle structure and composition to biological function and behaviour. Areas for future research in this area are discussed.