RGD-modified lipid disks as drug carriers for tumor targeted drug delivery

Targeted counteracting of overactive macrophages by melittin stable-loaded solid lipid nanoparticles alleviates cytokine storm and acute inflammatory injury

The continuous activation of macrophages play a critical role in the pathogenesis of cytokine storm (CS). Considering that CS results from the participation of multiple cytokines, the therapeutic effect of a single cytokine or its receptor-targeted blockade therapy remains uncertain. Melittin, which can systematically suppress the overexpression of proinflammatory mediators via inhibiting the mitogen-activated protein kinase and nuclear factor kappa-B pathways in activated macrophages, shows great potential in alleviating CS and acute inflammatory injury (AII). However, its clinical application is limited by its hemolytic activity, non-specific cytotoxicity and lack of targeting. In this study, a folic acid-modified and melittin stable-loaded solid lipid nanoparticle (Fa-MpG@LNP) with a core-shell structure was developed for CS control via targeted inhibition of the overproduction of proinflammatory mediators in activated macrophages with specific expression of folate receptor-β. The resultant Fa-MpG@LNP showed ideal physicochemical properties and stability, low hemolytic activity and non-specific cytotoxicity, and it can specifically bind to lipopolysaccharide (LPS)-stimulated macrophages and effectively reduce the elevated levels of proinflammatory mediators. After intravenous administration, the Fa-MpG@LNP accumulated at inflamed tissue and significantly downregulate the overproduction of proinflammatory cytokines in tissue-infiltrated macrophages, resulting in a significant decrease of cytokine concentration in inflamed tissue and serum in LPS-induced acute pneumonia mice, and finally alleviate AII with undetectable toxic side effects. These results indicate the clinical application potential of Fa-MpG@LNP in alleviating CS and its related symptoms.

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.

Immunomodulatory activities and biomedical applications of melittin and its recent advances

Melittin (MLT), a peptide containing 26 amino acids, is a key constituent of bee venom. It comprises ∼40%-60% of the venom's dry weight and is the main pricing index for bee venom, being the causative factor of pain. The unique properties of MLT extracted from bee venom have made it a very valuable active ingredient in the pharmaceutical industry as this cationic and amphipathic peptide has propitious effects on human health in diverse biological processes. It has the ability to strongly impact the membranes of cells and display hemolytic activity with anticancer characteristics. However, the clinical application of MLT has been limited by its severe hemolytic activity, which poses a challenge for therapeutic use. By employing more efficient mechanisms, such as modifying the MLT sequence, genetic engineering, and nano-delivery systems, it is anticipated that the limitations posed by MLT can be overcome, thereby enabling its wider application in therapeutic contexts. This review has outlined recent advancements in MLT's nano-delivery systems and genetically engineered cells expressing MLT and provided an overview of where the MLTMLT's platforms are and where they will go in the future with the challenges ahead. The focus is on exploring how these approaches can overcome the limitations associated with MLT's hemolytic activity and improve its selectivity and efficacy in targeting cancer cells. These advancements hold promise for the creation of innovative and enhanced therapeutic approaches based on MLT for the treatment of cancer.

Dual centrifugation as a novel and efficient method for the preparation of lipodisks

Polyethylene glycol (PEG)-stabilized lipodisks have emerged as innovatiive, promising nanocarriers for several classes of drugs. Prior research underscores the important role of lipid composition and preparation method in determining the lipodisk size, uniformity, and drug loading capacity. In this study, we investigate dual centrifugation (DC) as a novel technique for the production of PEG-stabilized lipodisks. Moreover, we explore the potential use of DC for the encapsulation of two model drugs, curcumin and doxorubicin, within the disks. Our results show that by a considerate choice of experimental conditions, DC can be used as a fast and straightforward means to produce small and homogenous lipodisks with a hydrodynamic diameter of 20-30 nm. Noteworthy, the technique works well for the production of both cholesterol-free and cholesterol-containing disks and does not require pre-mixing of the lipids in organic solvent. Furthermore, our investigations confirm the efficacy of DC in formulating curcumin and doxorubicin within these lipodisks. For doxorubicin, careful control and optimization of the experimental conditions resulted in formulations displaying an encouraging encapsulation efficiency of 84 % and a favourable drug-to-lipid ratio of 0.13 in the disks.

New N-Terminal Fatty-Acid-Modified Melittin Analogs with Potent Biological Activity

Melittin, a natural antimicrobial peptide, has broad-spectrum antimicrobial activity. This has resulted in it gaining increasing attention as a potential antibiotic alternative; however, its practical use has been limited by its weak antimicrobial activity, high hemolytic activity, and low proteolytic stability. In this study, N-terminal fatty acid conjugation was used to develop new melittin-derived lipopeptides (MDLs) to improve the characteristics of melittin. Our results showed that compared with native melittin, the antimicrobial activity of MDLs was increased by 2 to 16 times, and the stability of these MDLs against trypsin and pepsin degradation was increased by 50 to 80%. However, the hemolytic activity of the MDLs decreased when the length of the carbon chain of fatty acids exceeded 10. Among the MDLs, the newly designed analog Mel-C8 showed optimal antimicrobial activity and protease stability. The antimicrobial mechanism studied revealed that the MDLs showed a rapid bactericidal effect by interacting with lipopolysaccharide (LPS) or lipoteichoic acid (LTA) and penetrating the bacterial cell membrane. In conclusion, we designed and synthesized a new class of MDLs with potent antimicrobial activity, high proteolytic stability, and low hemolytic activity through N-terminal fatty acid conjugation.

From oncolytic peptides to oncolytic polymers: A new paradigm for oncotherapy

Traditional cancer therapy methods, especially those directed against specific intracellular targets or signaling pathways, are not powerful enough to overcome tumor heterogeneity and therapeutic resistance. Oncolytic peptides that can induce membrane lysis-mediated cancer cell death and subsequent anticancer immune responses, has provided a new paradigm for cancer therapy. However, the clinical application of oncolytic peptides is always limited by some factors such as unsatisfactory bio-distribution, poor stability, and off-target toxicity. To overcome these limitations, oncolytic polymers stand out as prospective therapeutic materials owing to their high stability, chemical versatility, and scalable production capacity, which has the potential to drive a revolution in cancer treatment. This review provides an overview of the mechanism and structure-activity relationship of oncolytic peptides. Then the oncolytic peptides-mediated combination therapy and the nano-delivery strategies for oncolytic peptides are summarized. Emphatically, the current research progress of oncolytic polymers has been highlighted. Lastly, the challenges and prospects in the development of oncolytic polymers are discussed.

Metal-Phenolic Network-Facilitated "Foe-to-Friend" Conversion of Melittin for Cancer Immunotherapy with Boosted Abscopal Effect

As a naturally occurring cytolytic peptide, melittin (Mel) has strong cytolytic activity and is a potent therapeutic peptide for cancer therapy. However, the serious hemolytic activity of Mel largely impedes its clinical applications. In this work, based on the strong interactions between proteins/peptides and polyphenols, we develop a tannic acid-Fe³⁺ metal-phenolic network (MPN)-based strategy that can convert Mel from foe to friend via shielding its positive charges and reducing its hemolytic activity. Besides, an immune adjuvant resiquimod (R848) is also introduced for immunostimulation, affording the final Mel- and R848-coloaded nanodrug. The Mel-caused membrane disruption can induce immunogenic cell death for immunostimulation, R848 can act as an immune adjuvant to further facilitate the immunostimulatory effect, and the tannic acid-Fe³⁺ MPN-mediated Fenton reaction can produce reactive oxygen species for cancer treatment. Further experiments reveal that the nanodrug can effectively cause immunogenic cell death of tumor cells and arouse robust intratumoral and systemic antitumor immunostimulation. In the bilateral tumor-bearing mouse models, the nanodrug considerably destroys the primary tumor and also boosts the abscopal effect to ablate the distant tumor. Collectively, the MPN-facilitated "foe-to-friend" strategy may promote the practical applications of Mel and foster the development of cancer immunotherapeutics.

Micro and nanotechnologies: The little formulations that could

The first publication of micro- and nanotechnology in medicine was in 1798 with the use of the Cowpox virus by Edward Jenner as an attenuated vaccine against Smallpox. Since then, there has been an explosion of micro- and nanotechnologies for medical applications. The breadth of these micro- and nanotechnologies is discussed in this piece, presenting the date of their first report and their latest progression (e.g., clinical trials, FDA approval). This includes successes such as the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines from Pfizer, Moderna, and Janssen (Johnson & Johnson) as well as the most popular nanoparticle therapy, liposomal Doxil. However, the enormity of the success of these platforms has not been without challenges. For example, we discuss why the production of Doxil was halted for several years, and the bankruptcy of BIND therapeutics, which relied on a nanoparticle drug carrier. Overall, the field of micro- and nanotechnology has advanced beyond these challenges and continues advancing new and novel platforms that have transformed therapies, vaccines, and imaging. In this review, a wide range of biomedical micro- and nanotechnology is discussed to serve as a primer to the field and provide an accessible summary of clinically relevant micro- and nanotechnology platforms.

Synthetic polymer material modified by d-peptide and its targeted application in the treatment of non-small cell lung cancer

Liposomes functionalized with targeted material offer a breakthrough compared with passive drug delivery. Here, we designed a polymer material, VAP-PEG₃₃₅₀-DSPE (VAP-PEG-DSPE), modified with a d-peptide VAP ligand that combines tumor-homing VAP with GRP78 receptor, a cancer marker on the membranes of many cancer cells. This paper establishes a docetaxel-loaded lipid nanodisk modified with multifunctional material to evaluate its anti-NSCLC efficacy in vivo. Additionally, the present study verified that VAP-conjugated nanodisks adapt to the developed tumor vasculature of the lung cancer microenvironment, making it a promising nanocarrier for NSCLC-targeting therapy. Moreover, in vitro and in vivo experiments demonstrated the targeting ability of VAP-DISK/DTX to tumor cells. Lung slices of mice also demonstrated the safety of VAP-DISK/DTX. The encapsulation efficiency of docetaxel-disks (VAP-DISK/DTX) was as high as 92.46±4.48%. Encapsulating anti-cancer drugs in lipid nanoparticles is thus an effective mechanism to change the pharmacokinetic and pharmacodynamic characteristics of drugs.

Nanodiscs: a versatile nanocarrier platform for cancer diagnosis and treatment

Cancer therapy is a significant challenge due to insufficient drug delivery to the cancer cells and non-selective killing of healthy cells by most chemotherapy agents. Nano-formulations have shown great promise for targeted drug delivery with improved efficiency. The shape and size of nanocarriers significantly affect their transport inside the body and internalization into the cancer cells. Non-spherical nanoparticles have shown prolonged blood circulation half-lives and higher cellular internalization frequency than spherical ones. Nanodiscs are desirable nano-formulations that demonstrate enhanced anisotropic character and versatile functionalization potential. Here, we review the recent development of theranostic nanodiscs for cancer mitigation ranging from traditional lipid nanodiscs encased by membrane scaffold proteins to newer nanodiscs where either the membrane scaffold proteins or the lipid bilayers themselves are replaced with their synthetic analogues. We first discuss early cancer detection enabled by nanodiscs. We then explain different strategies that have been explored to carry a wide range of payloads for chemotherapy, cancer gene therapy, and cancer vaccines. Finally, we discuss recent progress on organic-inorganic hybrid nanodiscs and polymer nanodiscs that have the potential to overcome the inherent instability problem of lipid nanodiscs.

Melittin-Based Nano-Delivery Systems for Cancer Therapy

Melittin (MEL) is a 26-amino acid polypeptide with a variety of pharmacological and toxicological effects, which include strong surface activity on cell lipid membranes, hemolytic activity, and potential anti-tumor properties. However, the clinical application of melittin is restricted due to its severe hemolytic activity. Different nanocarrier systems have been developed to achieve stable loading, side effects shielding, and tumor-targeted delivery, such as liposomes, cationic polymers, lipodisks, etc. In addition, MEL can be modified on nano drugs as a non-selective cytolytic peptide to enhance cellular uptake and endosomal/lysosomal escape. In this review, we discuss recent advances in MEL’s nano-delivery systems and MEL-modified nano drug carriers for cancer therapy.

Stable Loading and Delivery of Melittin with Lipid-Coated Polymeric Nanoparticles for Effective Tumor Therapy with Negligible Systemic Toxicity

Melittin is a potential anticancer candidate with remarkable antitumor activity and ability to overcome tumor drug resistance. However, the clinical applications of melittin are largely restricted by its severe hemolytic activity and nonspecific cytotoxicity after systemic administration. Here, a biocompatible and stable melittin-loaded lipid-coated polymeric nanoparticle (MpG@LPN) formulation that contains a melittin/poly-γ-glutamic acid nanoparticle inner core, a lipid membrane middle layer, and a polyethylene glycol (PEG) and PEG-targeting molecule outer shell was designed. The formulations were prepared by applying a self-assembly procedure based on intermolecular interactions, including electrostatic attraction and hydrophobic effect. The core-shell MpG@LPN presented high efficiency for melittin encapsulation and high stability in physiological conditions. Hemolysis and cell proliferation assays showed that the PEG-modified MpG@LPN had almost no hemolytic activity and nonspecific cytotoxicity even at high concentrations. The modification of targeting molecules on the MpG@LPNs allowed for the selective binding with target tumor cells and cytolytic activity via apoptosis induction. In vivo experiments revealed that MpG@LPNs can remarkably inhibit the growth of tumors without the occurrence of hemolysis and tissue toxicity. Results suggested that the developed MpG@LPN with a core-shell structure can effectively address the main obstacles of melittin in clinical applications and has great potential in cancer treatment.

A Systematic Approach for Liposome and Lipodisk Preclinical Formulation Development by Microfluidic Technology

Lipid nanoparticles have transformed the drug delivery field enhancing the therapeutic drug performance of small molecules and biologics with several approved drug products. However, in industry, these more complex drug delivery systems such as liposomes require more material and time to develop. Here, we report a liposome and lipodisk decision tree with model compounds of diverse physicochemical properties to understand how to resourcefully optimize encapsulation efficiency (EE) for these lipid-based drug delivery systems. We have identified trends with physicochemical properties such as Log P, where higher Log P compounds such as curcumin were able to efficiently load into the lipid bilayer resulting in high EE with altering the drug/lipid (D/L) ratio. Moderate Log P compounds such as cyclosporine A and dexamethasone had significantly higher encapsulation in lipodisks, which contain higher amounts of PEG lipid compared to liposomes. The EE of negative Log P compounds, like acyclovir, remained low regardless of altering the D/L ratio and PEG concentrations. In this study, microfluidic techniques were employed to fabricate liposomes and lipodisks formulations allowing for a reproducible strategy for formulation development. Both liposome and lipodisk of curcumin demonstrated enhanced in vivo performance compared with a conventional formulation in the rat pharmacokinetic study. This combination of approaches with multiple model compounds and lipid-based drug delivery systems provides a systematic guidance to effective strategies to generate higher EE with minimal drug waste and expedite the process for preclinical development when applied to industry compounds.

Delivery Strategies for Melittin-Based Cancer Therapy

Melittin (MLT) has been studied preclinically as an anticancer agent based on its broad lytic effects in multiple tumor types. However, unsatisfactory tissue distribution, hemolysis, rapid metabolism, and limited specificity are critical obstacles that limit the translation of MLT. Emerging drug delivery strategies hold promise for targeting, controlled drug release, reduced side effects, and ultimately improved treatment efficiency. In this review, we discuss recent advances in the use of diverse carriers to deliver MLT, with an emphasis on the design and mechanisms of action. We further outline the opportunities for MLT-based cancer immunotherapy.

Tumor acidic microenvironment-induced drug release of RGD peptide nanoparticles for cellular uptake and cancer therapy

Spatial accuracy is crucial in drug delivery, especially to increase the efficacy and reduce the side effects of antitumor drugs. In this study, we developed a simple and broadly applicable strategy in which a target peptide ligand was introduced to construct a pH-responsive drug-loading system to achieve targeted delivery and drug release in lesions. In addition to reaching the tumor tissue through passive targeting modalities such as the enhanced permeability and retention (EPR) effect, active targeting nanoparticles used RGD motifs coupled to nanocarriers to specifically bind certain integrins, such as ανβ3, which is expressed on the surface of tumor cells, to achieve active tumor cell targeting. Self-assembling peptides have significant advantages in their structural design. The amphiphilic peptide LKR could form a spherical and self-assembled nanoparticle, which encapsulated the fat-soluble antitumor drug doxorubicin (Dox) in neutral medium. The Dox-encapsulating peptide nanoparticles swelled and burst, rapidly releasing Dox in an acidic microenvironment. Flow cytometry and fluorescence detection showed that the self-assembled LKR nanoparticles enhanced the drug accumulation in tumor cells compared with normal mammalian cells. The Dox-encapsulating peptide nanoparticles exhibited desirable antitumor effects in vivo. In summary, the acidic microenvironment of tumors was used to induce drug release from a targeted peptide drug-loading system to enhance cellular uptake and therapeutic effects in situ, providing a promising therapeutic approach for the treatment of major diseases such as hepatoma.

Folate Modified Long Circulating Nano-Emulsion as a Promising Approach for Improving the Efficiency of Chemotherapy Drugs in Cancer Treatment

PURPOSE

In order to improve the therapeutic efficiency of the chemotherapeutic drug paclitaxel in tumors, a folate-based Paclitaxel nanoemulsion (FNEs) was developed for tumor targeted treatment.

METHODS

In this study, we designed a folate-targeted nanoemulsion (folate/PEG-DSPE/nanoemulsion, FNEs) based on the traditional nanoemulsion using the principle of long-circulation targeting receptor mediated. The nanoemulsion (folate/PEG-DSPE/nanoemulsion, FNEs) was fabricated using high-pressure homogenization with a microfluidizer.

RESULTS

The nanoemulsion (folate/PEG-DSPE/nanoemulsion, FNEs) can improve the delivery efficiency of nanocarriers at the tumor site by virtue of the high expression of folate receptors on the tumor surface. Malvern Nanoseries device and transmission electron microscopy (TEM) analyses showed that the nanoemulsions were spherical with an average diameter of 140 nm. The nanoemulsions can effectively carry paclitaxel (PTX) with an encapsulation rate of about 95%. And in vitro experiments have shown that it can efficiently increase the uptake of PTX in 4 T1 breast cancer cells and FNEs had a targeting capability hundredfold higher than that of PTX-loaded nanoemulsions (PTX-NEs) without folate. In vivo experiments have shown that the pharmacokinetic parameters of FNEs were better than those of other PTX groups and FNEs can significantly enhance circulation time in the body of the subcutaneously implanted 4 T1 breast cancer in mice, increase the accumulation of chemotherapy drugs at tumor sites and effectively inhibit tumor growth with lower system toxicity.

CONCLUSIONS

This study can effectively improve the therapeutic efficiency of chemotherapy drugs for tumors, and provide an useful reference for solving the problem of low efficacy of chemotherapy drugs in clinical treatment of tumors. Graphical Abstract Schematic representation of Folic acid/PEG-DSPE/nano-emulsion (FNEs) specifically target tumor cells and enhanced anti-tumor effects.

Lysine-embedded cellulose-based nanosystem for efficient dual-delivery of chemotherapeutics in combination cancer therapy

Combination therapy by two or multiple drugs with different mechanisms of action is a promising strategy in cancer treatment. In this regard, a wide range of chemotherapeutics has used simultaneously to achieve the synergistic effect and overcome the adverse side effects of single-drug therapy. Herein, we developed a biocompatible nanoparticle-based system composed of nanocrystalline cellulose (NCC) and amino acid l-lysine for efficient co-delivery of model chemotherapeutic methotrexate (MTX) and polyphenol compound curcumin (CUR) to the MCF-7 and MDA-MB-231 cells. The drugs could release in a sustained and acidic-facilitate manner. In vitro cytotoxicity results represented the superior anti-tumor efficacy of the dual-drug-loaded nanocarriers. Possible inhibition of cell growth and induction of apoptosis in the cells treated with different formulations of CUR and MTX were explored by cell cycle analysis and DAPI staining. Overall, the engineered nanosystem can be used as suitable candidates to achieve efficient multi-drug delivery for combination cancer therapy.

Factors Influencing the Immunogenicity and Immunotoxicity of Cyclic RGD Peptide-Modified Nanodrug Delivery Systems

c(RGDyK)-modified liposomes have been shown to be immunogenic and potentially trigger acute systemic anaphylaxis upon repeated intravenous injection in both BALB/c nude mice and ICR mice. However, questions concerning the potential influence of mouse strains, immunization routes, drug carrier properties, and changes in c(RGDyK) itself on the immunogenicity and resultant immunotoxicity (anaphylaxis) of cyclic RGD peptide-modified nanodrug delivery systems remain unanswered. Here, these potential impact factors were investigated, aiming to better understand the immunological properties of cyclic RGD peptide-based nanodrug delivery systems and seek for solutions for this immunogenicity-associated issue. It was revealed that anaphylaxis caused by intravenous c(RGDyK)-modified drug delivery systems might be avoided by altering the preimmunization route (i.e., subcutaneous injection), introducing positively charged lipids into the liposomes and by using micelles or red blood cell membrane (RBC)-based drug delivery systems as the carrier. Different murine models showed different incidences of anaphylaxis following intravenous c(RGDyK)-liposome stimulation: anaphylaxis was not observed in both SD rats and BALB/c mice and was less frequent in C57BL/6 mice than that in ICR mice. In addition, enlarging the peptide ring of c(RGDyK) by introducing amino sequence serine-glycine-serine reduced the incidence of anaphylaxis post the repeated intravenous c(RGDyKSGS)-liposome stimulation. However, immunogenicity of cyclic RGD-modified drug carriers could not be reversed, although some reduction in IgG antibody production was observed when ICR mice were intravenously stimulated with c(RGDyK)-modified micelles, RBC membrane-based drug delivery systems and c(RGDyKSGS)-liposomes instead of c(RGDyK)-liposomes. This study provides a valuable reference for future application of cyclic RGD peptide-modified drug delivery systems.

Tumor-Targeted Delivery of the p53-Activating Peptide VIP116 with PEG-Stabilized Lipodisks

Stapled peptides targeting the interaction between p53 and its negative regulators MDM2 and MDM4 have exhibited great potential as anti-cancer drugs, albeit with room for improvement in formulation and tumor specificity. Lipid bilayer disks (lipodisks) have emerged as promising drug nanocarriers and can by attachment of targeting moieties be directed selectively towards tumor cells. Tumor-targeted delivery of stapled peptides by use of lipodisks may therefore increase the uptake in the tumors and limit toxicity in healthy tissue. Here, we utilized epidermal growth factor receptor (EGFR)-targeted lipodisks to deliver p53-activating stapled peptide VIP116 to EGFR-expressing tumor cells. We demonstrate that VIP116 can be stably formulated in lipodisks (maximum peptide/lipid molar ratio 0.11). In vitro cell studies verify specific binding of EGF-decorated lipodisks to tumor cells and confirm that targeted delivery of VIP116 significantly decreases tumor cell viability.

Targeting drug delivery system for platinum(Ⅳ)-Based antitumor complexes

Classical platinum(II) anticancer agents are widely-used chemotherapeutic drugs in the clinic against a range of cancers. However, severe systemic toxicity and drug resistance have become the main obstacles which limit their application and effectiveness. Because divalent cisplatin analogues are easily destroyed in vivo, their bioavailability is low and no selective to tumor tissues. The platinum(IV) prodrugs are attractive compounds for cancer treatment because they have great advantages, e.g., higher stability in biological media, aqueous solubility and no cross-resistance with cisplatin, which may become the next generation of platinum anticancer drugs. In addition, platinum(IV) drugs could be taken orally, which could be more acceptable to cancer patients, breaking the current situation that platinum(II) drugs can only be given by injection. The coupling of platinum(IV) complexes with tumor targeting groups avoids the disadvantages such as instability in blood, irreversible binding to plasma proteins, rapid renal clearance, and non-specific distribution in normal tissues. Because of the above advantages, the combination of platinum complexes and tumor targeting groups has become the hottest field in the research and development of new platinum drugs. These approaches can be roughly categorized into two groups: active and passive targeted strategies. This review concentrates on various targeting and delivery strategies for platinum(IV) complexes to improve the efficacy and reduce the side effects of platinum-based anticancer drugs. We have made a summary of the related articles on platinum(IV) targeted delivery in recent years. We believe the results of the studies described in this review will provide new ideas and strategies for the development of platinum drugs.

Recent progress in biomedical applications of RGD-based ligand: From precise cancer theranostics to biomaterial engineering: A systematic review

Arginine-glycine-aspartic acid (RGD) peptide family is known as the most prominent ligand for extracellular domain of integrin receptors. Specific expression of these receptors in various tissue of human body and tight association of their expression profile with various pathophysiological conditions made these receptors a suitable targeting candidate for several disease diagnosis and treatment as well as regeneration of various organs. For these reasons, various forms of RGD-based integrins ligands have been greatly used in biomedical studies. Here, we summarized the last decade application progress of RGD for cancer theranostics, control of inflammation, thrombosis inhibition and critically discussed the effect of RGD peptides structure and sequence on the efficacy of gene/drug delivery systems in preclinical studies. Furthermore, we will show recent advances in application of RGD functionalized biomaterials for various tissue regenerations including cornea repair, artificial neovascularization and bone tissue regeneration. Finally, we analyzed clinically translatability of RGD peptides, considering examples of integrin ligands in clinical trials. In conclusion, prospects on using RGD peptide for precise drug delivery and biomaterial engineering are well discussed.

Co-delivery of Bee Venom Melittin and a Photosensitizer with an Organic-Inorganic Hybrid Nanocarrier for Photodynamic Therapy and Immunotherapy

Photodynamic therapy (PDT) is a clinical cancer treatment modality based on the induction of therapeutic reactive oxygen species (ROS), which can trigger immunogenic cell death (ICD). With the aim of simultaneously improving both PDT-mediated intracellular ROS production and ICD levels, we designed a serum albumin (SA)-coated boehmite ("B"; aluminum hydroxide oxide) organic-inorganic scaffold that could be loaded with chlorin e6 (Ce6), a photosensitizer, and a honey bee venom melittin (MLT) peptide, denoted Ce6/MLT@SAB. Ce6/MLT@SAB was anchored by a boehmite nanorod structure and exhibited particle size of approximately 180 nm. Ce6/MLT@SAB could significantly reduce hemolysis relative to that of free MLT, while providing MLT-enhanced PDT antitumor effects in vitro. Compared with Ce6@SAB, Ce6/MLT@SAB improved Ce6 penetration of cancer cells both in vitro and in vivo, thereby providing enhanced intracellular ROS generation with 660 nm light treatment. Following phototreatment, Ce6/MLT@SAB-treated cells displayed significantly improved levels of ICD and abilities to activate dendritic cells. In the absence of laser irradiation, multidose injection of Ce6/MLT@SAB could delay the growth of subcutaneous murine tumors by more than 60%, compared to controls. When combined with laser irradiation, a single injection and phototreatment with Ce6/MLT@SAB eradicated one-third of subcutaneous tumors in treated mice. The addition of an immune checkpoint blockade to Ce6/MLT@SAB phototreatment further augmented antitumor effects, generating increased numbers of CD4⁺ and CD8⁺ T cells in tumors with concomitant reduction of myeloid-derived suppressor cells.

Nanoscale systems for local drug delivery

Many diseases and conditions affect a relatively localized area of the body. They can be treated either by direct deposition of drug in the target area, or by giving the drug systemically. Here we review nanoparticle-based approaches to achieving both. We highlight advantages and disadvantages that nanoscale solutions have for locally administered therapies, with emphasis on the former. We discuss strategies to enable systemically delivered nanoparticles to deliver their payloads at specific locations in the body, including triggering (local and remote) and targeting.

Embryonic Stem Cells-Derived Exosomes Endowed with Targeting Properties as Chemotherapeutics Delivery Vehicles for Glioblastoma Therapy

Exosomes are nanosized membrane vesicles (30-100 nm) that can easily penetrate the blood-brain barrier, safely deliver therapeutic drugs, and be modified with target ligands. Embryonic stem cells (ESCs) provide abundant exosome sources for clinical application due to their almost unlimited self-renewal. Previous studies show that exosomes secreted by ESCs (ESC-exos) have antitumor properties. However, it is not known whether ESC-exos inhibit glioblastoma (GBM) growth. In this study, the anti-GBM effect of ESC-exos is confirmed and then c(RGDyK)-modified and paclitaxel (PTX)-loaded ESC-exos, named cRGD-Exo-PTX are prepared. It is then investigated whether the engineered exosomes deliver more efficiently to GBM cells versus free drug alone and drug-loaded ESC-exos using an in vitro GBM model and in vivo subcutaneous and orthotopic xenografts model. The results show that cRGD-Exo-PTX significantly improves the curative effects of PTX in GBM via enhanced targeting. These data indicate that ESC-exos are potentially powerful therapeutic carriers for GBM and could have utility in many other diseases.

Altering the edge chemistry of bicelles with peptoids

Cell function is tied to the interactions that occur within and across the cell membrane. Therefore, understanding membrane-affiliated interactions is important to many biomedical applications. Advancing the body of knowledge about these interactions will lead to discoveries in biomarker detection and therapeutic targets for disease detection and treatment. Model membrane systems are an effective way to study membrane proteins for such discoveries, allowing for stable protein structure and maintaining native activity. Bicelles, disc-shaped lipid bilayers created by combining long- and short-chain phospholipids, are the model membrane system of focus in this study. Bicelles are accessible from both sides and have a wide size range, which makes them attractive for studying membrane interactions without affecting function. In this work, bicelles were functionalized with peptoids to alter the edge chemistry. Peptoids are suitable for this application because of the large diversity of available side chain chemistries that can be easily incorporated in a sequence-specific manner. The peptoid sequence consists of three functional regions to promote insertion into the edge of bicelles. The insertion sequence at the C-terminus contains two alkyl chains and two hydrophobic, chiral aromatic groups that anchor into the bicelle edge. The facially amphipathic helix contains chiral aromatic groups on one side that interact with the lipid tails and positively charged groups on the other side, which interact with the lipid head groups. Thiol groups are included at the N-terminus to allow for visualization of peptoid location in the bicelle. Bicelle morphology and size were assessed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Peptoid location in the bicelle was determined by attachment of gold nanoparticles, which confirmed preferential incorporation of the peptoid into the bicelle edge with 82% specificity. Additionally, the peptoid-functionalized bicelles are of similar size and morphology to non-functionalized bicelles. Results from this study show that peptoid-functionalized bicelles are a promising model membrane system with potential applications in biosensors or bioseparations.

l-Peptide functionalized dual-responsive nanoparticles for controlled paclitaxel release and enhanced apoptosis in breast cancer cells

Nanoparticles and macromolecular carriers have been widely used to increase the efficacy of chemotherapeutics, largely through passive accumulation provided by their enhanced permeability and retention effect. However, the therapeutic efficacy of nanoscale anticancer drug delivery systems is severely truncated by their low tumor-targetability and inefficient drug release at the target site. Here, the design and development of novel l-peptide functionalized dual-responsive nanoparticles (l-CS-g-PNIPAM-PTX) for active targeting and effective treatment of GRP78-overexpressing human breast cancer in vitro and in vivo are reported. l-CS-g-PNIPAM-PTX NPs have a relative high drug loading (13.5%) and excellent encapsulation efficiency (74.3%) and an average diameter of 275 nm. The release of PTX is slow at pH 7.4 and 25 °C but greatly accelerated at pH 5.0 and 37 °C. MTT assays and confocal experiments showed that the l-CS-g-PNIPAM-PTX NPs possessed high targetability and antitumor activity toward GRP78 overexpressing MDA-MB-231 human breast cancer cells. As expected, l-CS-g-PNIPAM-PTX NPs could effectively treat mice bearing MDA-MB-231 human breast tumor xenografts with little side effects, resulting in complete inhibition of tumor growth and a high survival rate over an experimental period of 60 days. These results indicate that l-peptide-functionalized acid - and thermally activated - PTX prodrug NPs have a great potential for targeted chemotherapy in breast cancer.

Amphiphilic peptides as novel nanomaterials: design, self-assembly and application

Designer self-assembling peptides are a category of emerging nanobiomaterials which have been widely investigated in the past decades. In this field, amphiphilic peptides have received special attention for their simplicity in design and versatility in application. This review focuses on recent progress in designer amphiphilic peptides, trying to give a comprehensive overview about this special type of self-assembling peptides. By exploring published studies on several typical types of amphiphilic peptides in recent years, herein we discuss in detail the basic design, self-assembling behaviors and the mechanism of amphiphilic peptides, as well as how their nanostructures are affected by the peptide characteristics or environmental parameters. The applications of these peptides as potential nanomaterials for nanomedicine and nanotechnology are also summarized.

Turning Toxicants into Safe Therapeutic Drugs: Cytolytic Peptide-Photosensitizer Assemblies for Optimized In Vivo Delivery of Melittin

Melittin (MEL) is recognized as a highly potent therapeutic peptide for treating various human diseases including cancer. However, the clinical applications of MEL are largely restricted by its severe hemolytic activity and nonspecific cytotoxicity. Here, it is found that MEL can form a stable supramolecular nanocomplex of ≈60 nm with the photosensitizer chlorin e6 (Ce6), which after hyaluronic acid (HA) coating can achieve robust, safe, and imaging-guided tumor ablation. The as-designed nanocomplex (denoted as MEL/Ce6@HA) shows largely reduced hemolysis and selective cytolytic activity toward cancer cells. Upon laser irradiation, the loaded photosensitive Ce6 can synergistically facilitate the membrane-lytic efficiency of melittin and greatly increase the tumor penetration depth of the complexes in multicellular tumor spheroids. In vivo experiments reveal that MEL/Ce6@HA can realize enhanced tumor accumulation, reduced liver deposition, and rapid body clearance, which are beneficial for highly efficient and safe chemo-photodynamic dual therapy. This work develops a unique supramolecular strategy for optimized in vivo delivery of melittin and may have implications for the development of peptide-based theranostics.

Triple Stimuli-Responsive Magnetic Hollow Porous Carbon-Based Nanodrug Delivery System for Magnetic Resonance Imaging-Guided Synergistic Photothermal/Chemotherapy of Cancer

The premature leakage of anticancer drugs during blood circulation may the damage immune system, normal cells, and tissues. Constructing targeted nanocarriers with pH, glutathione, and NIR triple-responsive property can effectively avoid the leakage of anticancer drugs before they arrive at the targeted site. In this paper, magnetic hollow porous carbon nanoparticles (MHPCNs) were successfully fabricated as nanocarrier. Poly(γ-glutamic acid) was used to cap the pores of MHPCNs. The photothermal conversion property of carbon and iron oxide (Fe₃O₄) nanomaterials was utilized to perform photothermal therapy to overcome multidrug-resistance produced by chemotherapy. The biodistribution of nanoparticles was investigated by magnetic resonance imaging. Experiments in vivo confirm the efficient accumulations of nanoparticles at tumor sites. Meanwhile, tumor growth was effectively inhibited via synergistic photothermal/chemotherapy with minimal side effects.

Nanodisk-based glioma-targeted drug delivery enabled by a stable glycopeptide

Heptapeptide ATWLPPR (A7R) binds specifically to vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin-1 (NRP-1) overexpressed in glioma cells, exhibiting high potential to achieve glioma targeted drug delivery. However, in vivo application of A7R peptide remains challenging due to the poor proteolytic stability and inaccessibility of A7R to the brain. To tackle these problems, we identified a glycosylated A7R derivative to enhance in vivo stability and brain transport efficacy. Our results showed that glycosylation of peptide could efficiently improve stability in serum, traverse the blood-brain barrier (BBB) and be uptaken by glioma cells. Furthermore, a novel glioma-targeted drug delivery system was constructed successfully employing glycopeptide as the targeting moiety and nanodisk as the carrier of paclitaxel (PTX). Physicochemical characterization showed that the nanodisk presented suitable size of 50 nm and adequate loading capacity of PTX. Compared to non-glycosylated nanodisk, glycopeptide modification could significantly enhance the uptake of disks by brain capillary endothelial cells through glucose transporter 1 (GLUT1). In vivo imaging and glioma fluorescence section results also indicated that nanodisks modified with glycopeptide showed a higher accumulation in glioma. The glycopeptide-enabled PTX delivery system exhibited superior anti-glioma efficacy in intracranial glioma xenograft model. These results suggested that glycosylation of peptides provided an efficient pathway to design multifunctional and stable brain targeting ligands.

Multi-branched ionic liquid-chitosan as a smart and biocompatible nano-vehicle for combination chemotherapy with stealth and targeted properties

A possible approach for clinical cancer treatment is combination chemotherapy. To address this issue, many anticancer agents have been used simultaneously to achieve synergistic effects with the different mechanism of actions, however, their toxic side effects are still a big challenge. In this study, a smart, biocompatible, magnetic nanocarrier composed of multi-branched ionic liquid-chitosan grafted mPEG was designed and used for targeted multidrug delivery of DOX and MTX as model anticancer agents to MCF7 breast cancer cells. The results of hemolysis assay on human red blood cells and cytotoxicity studies indicated that blank nanocarrier has no significant hemolytic and cytotoxic effects in MCF7 cells as observed in the results of MTT assay, however, drugs-loaded nanocarrier could decrease the viability of MCF7 cells in a dose-dependent manner. To further simulate the interaction of nanocarrier with plasma proteins, the SDS-PAGE assay was performed after the nanocarrier was incubated with human plasma and the results indicated that a series of proteins were attached to the surface of nanocarrier leading protein-particle corona complex. This complex gives a stealth property as well as increasing cellular uptake process due to the presence of proteins acting as ligands for receptors in the surface of cancer cells that are suitable for drug delivery systems. The efficiency of dual-drug delivery was also confirmed by cellular uptake and DAPI staining. All these results persuade us, this nanocarrier is suitable for use in further animal studies in future investigations.

Enhanced Glioblastoma Targeting Ability of Carfilzomib Enabled by a DA7R-Modified Lipid Nanodisk

The robust proliferation of tumors relies on a rich neovasculature for nutrient supplies. Therefore, a basic strategy of tumor targeting therapy should include not only killing regular cancer cells but also blocking tumor neovasculature. D-peptide ^DA7R, which was previously reported to specifically bind vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin-1 (NRP-1), could achieve the goal of multitarget recognition. Accordingly, the main purposes of this work were to establish a carfilzomib-loaded lipid nanodisk modified with multifunctional peptide ^DA7R (^DA7R-ND/CFZ) and to evaluate its anti-glioblastoma efficacy in vitro and in vivo. It is testified that the ^DA7R peptide-conjugated lipid nanodisk can be specifically taken up by U87MG cells and HUVECs. Furthermore, ^DA7R-ND demonstrated a more enhanced penetration than that of the nonmodified formulation on the tumor spheroid model in vitro and more tumor region accumulation in vivo on the subcutaneous and intracranial tumor-bearing nude mice model. ^DA7R-ND was shown to co-localize with tumor neovasculature in vivo. When loaded with proteasome inhibitor carfilzomib, the ^DA7R-decorated nanodisk could remarkably suppress tumor proliferation, extend survival time of nude mice bearing an intracranial tumor, and inhibit neovasculature formation with an efficacy higher than that of the nonmodified nanodisk in vitro and in vivo. The present study verified that the heptapeptide ^DA7R-conjugated nanodisk is a promising nanocarrier for glioblastoma targeting therapy.

Liposomes and lipid disks traverse the BBB and BBTB as intact forms as revealed by two-step Förster resonance energy transfer imaging

The blood-brain barrier (BBB) and the blood-brain tumor barrier (BBTB) prevent drug and nano-drug delivery systems from entering the brain. However, ligand-mediated nano-drug delivery systems have significantly enhanced the therapeutic treatment of glioma. In this study we investigated the mechanism especially the integrity of liposomes and lipid disks while traversing the BBB and BBTB both in vitro and in vivo. Fluorophores (DiO, DiI and DiD) were loaded into liposomes and lipid disks to form Förster resonance energy transfer (FRET) nano-drug delivery systems. Using brain capillary endothelial cells as a BBB model, we show that liposomes and disks are present in the cytoplasm as their intact forms and traverse the BBB with a ratio of 0.68‰ and 1.67‰, respectively. Using human umbilical vein endothelial cells as BBTB model, liposomes and disks remained intact and traversed the BBTB with a ratio of 2.31‰ and 8.32‰ at 3 h. Ex vivo imaging and immunohistochemical results revealed that liposomes and disks could traverse the BBB and BBTB in vivo as intact forms. In conclusion, these observations explain in part the mechanism by which nano-drug delivery systems increase the therapeutic treatment of glioma.

Doxorubicin-triggered self-assembly of native amphiphilic peptides into spherical nanoparticles

In this study, we designed and fabricated self-assembly nanospheres, which consisted of a P45 peptide and doxorubicin (Dox). P45 is a hybrid peptide composed of an Arg-Gly-Asp motif linked to the human matrilin-1 C-terminal domain by a serine linker. The fabricated nanospheres had a uniform mulberry-like spherical shape, a diameter of 63 nm, excellent polydispersity, and high Dox drug-loading efficiency. In the presence of the RGD motif, the Dox/P45 nanospheres could specifically target A549 cells, which have high integrin α_vβ₃ expression. Confocal laser scanning microscopy and flow cytometry results showed the enhanced cellular uptake of Dox/P45, and the CCK8 assay indicated the low cytotoxicity of the nanospheres to normal human embryonic kidney 293 cells. Furthermore, the fabricated nanospheres were stable in a physiological environment, but they disassembled and exhibited a rapid Dox release in an acidic atmosphere, allowing for a specific pH-sensitive release into cytosol after cellular uptake. These results suggest that natural amphiphilic peptides can be used as carriers of nanodrugs for targeting delivery as well as controlled drug release for cancer therapy.

Self-assembled pH-responsive supramolecular hydrogel for hydrophobic drug delivery

In this study, a novel supramolecular hydrogel system, abbreviated as AGC₁₆/NTS, prepared by molecular self-assembly of cationic gemini surfactant 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylatedibromide (AGC₁₆) and anionic aromatic compound trisodium 1,3,6-naphthalenetrisulfonate (NTS), was used to encapsulate hydrophobic model drug curcumin (Cur), constructing a pH-responsive drug delivery system. Cur was effectively encapsulated into the hydrophobic domains of AGC₁₆/NTS through hydrophobic interaction, which was confirmed by ¹H NMR measurement. The effects of Cur on the mechanical strength, phase transition behaviour and morphology of AGC₁₆/NTS were characterized by rheology and cryogenic scanning electron microscopy (cryo-SEM) methods. The pH-responsive release of Cur from AGC₁₆/NTS was obtained and the release amount of Cur ascended with pH value decreasing from 7.4 to 3.0. The hydrodynamic sizes of the released Cur-aggregates determined by dynamic light scattering (DLS) were used to analyse the release process of Cur at different pH. The cell viability assay and cell imaging experiment demonstrated that Cur-loaded hydrogel has much higher cytotoxicity and better cell uptake compared to free Cur. Overall, the AGC₁₆/NTS hydrogel is a prospective material for use in encapsulation and controlled-release of hydrophobic drug molecules.

Supramolecular hydrogel, AGC₁₆/NTS, was used to encapsulate hydrophobic drug curcumin (Cur), constructing a pH-responsive drug delivery system; the uptake of released Cur by cancer cells also occurred.

EGF-targeting lipodisks for specific delivery of poorly water-soluble anticancer agents to tumour cells

We report on the construction of tumour targeting PEG-stabilized lipodisks capable of receptor mediated intracellular delivery of curcumin.

Characterizing and Controlling the Loading and Release of Cationic Amphiphilic Peptides onto and from PEG-Stabilized Lipodisks

Recent studies have identified PEG-stabilized lipid nanodisks (lipodisks) as promising carriers for cationic amphiphilic peptides with antimicrobial and anticancer activity. Using fluorimetric and nanogravimetric methods, we have in this work characterized the parameters describing and controlling the binding of three selected peptides (melittin, LL37, and magainin 2) onto lipodisks. It was found that the affinity of melittin for lipodisks is independent of the disk size and rim charge. On the other hand, the number of binding sites is strongly dependent on both parameters, with the highest loading being obtained for small disks with a negatively charged rim. An optimized composition of the lipodisks was utilized to study the loading of antimicrobial peptides magainin 2 and human LL37. It was observed that although magainin 2 can be loaded in large amounts, it is released very fast upon dilution, which limits future therapeutic applications. In contrast, LL37 can be loaded at relevant concentrations and the formulation is stable. This opens up for applications of LL37-loaded lipodisks as antibiotics and in anticancer treatments.