Advances in peptide-based drug delivery systems

Drug delivery systems (DDSs) are designed to deliver drugs to their specific targets to minimize their toxic effects and improve their susceptibility to clearance during targeted transport. Peptides have high affinity, low immunogenicity, simple amino acid composition, and adjustable molecular size; therefore, most peptides can be coupled to drugs via linkers to form peptide-drug conjugates (PDCs) and act as active pro-drugs. PDCs are widely thought to be promising DDSs, given their ability to improve drug bio-compatibility and physiological stability. Peptide-based DDSs are often used to deliver therapeutic substances such as anti-cancer drugs and nucleic acid-based drugs, which not only slow the degradation rate of drugs in vivo but also ensure the drug concentration at the targeted site and prolong the half-life of drugs in vivo. This article provides an profile of the advancements and future development in functional peptide-based DDSs both domestically and internationally in recent years, in the expectation of achieving targeted drug delivery incorporating functional peptides and taking full advantage of synergistic effects.

Glutathione Programmed Mitochondria Targeted Delivery of Lonidamine for Effective Against Triple Negative Breast Cancer

Introduction

Mitochondria are a significant target of lonidamine (LND). However, its limited solubility and inability to specifically target mitochondria, LND can lead to hepatic toxicity and has shown only modest anticancer activity. The objective of this study is to establish a glutathione programmed mitochondria targeted delivery of LND for the effective treatment of triple negative breast cancer (TNBC).

Methods

In this study, LND was encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) wrapped with mitochondria-targeting short-chain triphenylphosphonium-tocopherol polyethylene glycol succinate (TPP-TPGS, TPS) and tumor-targeting long-chain 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine-S-S-polyethylene glycol-R6RGD (DSPE-S-S-PEG₂₀₀₀-R6RGD, DSSR), which were designated as LND-PLGA/TPS/DSSR NPs. The release behavior was evaluated, and cellular uptake, in vitro and in vivo antitumor activity of nanoparticles were investigated. The mechanism, including apoptosis of tumor cells and mitochondrial damage and respiratory rate detection, was also further investigated.

Results

LND-PLGA/TPS/DSSR NPs were successfully prepared, and characterization revealed that they are globular particles with smooth surfaces and an average diameter of about 250 nm. Long-chain DSSR in LND-PLGA/TPS/DSSR NPs prevented positively charged LND-PLGA/TPS NPs from being cleared by the reticuloendothelial system. Furthermore, LND release rate from NPs at pH 8.0 was significantly higher than that at pH 7.4 and 5.5, which demonstrated specific LND release in mitochondria and prevented LND leakage in cytoplasm and lysosome. NPs could locate in mitochondria, and the released LND triggered apoptosis of tumor cells by damaging mitochondria and releasing apoptosis-related proteins. In addition, in TNBC mice model, programmed mitochondria targeted NPs improved efficacy and reduced LND toxicity.

Conclusion

LND-PLGA/TPS/DSSR NPs may be a useful system and provide an effective approach for the treatment of TNBC.

Stimulus-responsive peptide hydrogels: a safe and least invasive administration approach for tumor treatment

Tumours, with increasing mortality around the world, have bothered human beings for decades. Enhancing the targeting of antitumor drugs to tumour tissues is the key to enhancing their antitumor effects. The tumour microenvironment is characterised by a relatively low pH, overexpression of certain enzymes, redox imbalance, etc. Therefore, smart drug delivery systems that respond to the tumour microenvironment have been proposed to selectively release antitumor drugs. Among them, peptide hydrogels as a local drug delivery system have received much attention due to advantages such as high biocompatibility, degradability and high water-absorbing capacity. The combination of peptide segments with different physiological functions allows for tumour targeting, self-aggregation, responsiveness, etc. Morphological and microstructural changes in peptide hydrogels can occur when utilising the inherent pathological microenvironment of tumours to trigger drug release, which endows such systems with limited adverse effects and improved therapeutic efficiency. Herein, this review outlined the driving forces, impact factors, and sequence design in peptide hydrogels. We also discussed the triggers to induce the transformation of peptide-based hydrogels in the tumour microenvironment and described the advancements of peptide-based hydrogels for local drug delivery in tumour treatment. Finally, we gave a brief perspective on the prospects and challenges in this field.

Switching the Mode of Drug Release from a Reaction-Coupled Low-Molecular-Weight Gelator System by Altering Its Reaction Pathway

Low-molecular-weight hydrogels are attractive scaffolds for drug delivery applications because of their modular and facile preparation starting from inexpensive molecular components. The molecular design of the hydrogelator results in a commitment to a particular release strategy, where either noncovalent or covalent bonding of the drug molecule dictates its rate and mechanism. Herein, we demonstrate an alternative approach using a reaction-coupled gelator to tune drug release in a facile and user-defined manner by altering the reaction pathway of the low-molecular-weight gelator (LMWG) and drug components through an acylhydrazone-bond-forming reaction. We show that an off-the-shelf drug with a reactive handle, doxorubicin, can be covalently bound to the gelator through its ketone moiety when the addition of the aldehyde component is delayed from 0 to 24 h, or noncovalently bound with its addition at 0 h. We also examine the use of an l-histidine methyl ester catalyst to prepare the drug-loaded hydrogels under physiological conditions. Fitting of the drug release profiles with the Korsmeyer-Peppas model corroborates a switch in the mode of release consistent with the reaction pathway taken: increased covalent ligation drives a transition from a Fickian to a semi-Fickian mode in the second stage of release with a decreased rate. Sustained release of doxorubicin from the reaction-coupled hydrogel is further confirmed in an MTT toxicity assay with MCF-7 breast cancer cells. We demonstrate the modularity and ease of the reaction-coupled approach to prepare drug-loaded self-assembled hydrogels in situ with tunable mechanics and drug release profiles that may find eventual applications in macroscale drug delivery.

Nanofibrillar peptide hydrogels for self-delivery of lonidamine and synergistic photodynamic therapy

The use of lonidamine (LND) in photodynamic therapy (PDT) provides a viable approach to develop low-dose PDT modules with high efficacy, for LND potentiates cytotoxicity of photosensitizers through dysregulation of mitochondrial function. Yet, the efficacy of LND is restricted by its low accumulation in cancer cells, especially in the mitochondrial compartments. To address the problem, we design an LND-derived self-assembling peptide molecule (LND-K) that dually targets integrin receptors and mitochondria of cancer cells. The targeted cellular delivery of LND-K gives higher efficacy in ablation of mitochondrial function in melanoma cells A375, as compared to free LND or the control molecule that lacks mitochondria-targeting moieties. To integrate LND-K in a typical PDT module, we develop a nanofibrillar hydrogel system through co-assembly of LND-K and TPPS₄, an anionic photosensitizer that forms tight electrostatic interactions with cationic residues of LND-K. Notably, hydrogel formulation of LND-K/TPPS₄ facilitates slow release of TPPS₄ over 14 days in vitro, and displays a longer retention time than aqueous solution of TPPS₄in vivo. By integrating a mitochondria-targeted molecule (LND-K) in a typical PDT module, we achieve synergistic killing of A375 cells with dual drugs, where LND-K not only serves as a chemotherapeutic drug, but also potentiates the cytotoxicities of TPPS₄ toward A375 cells in vitro and in vivo. The peptide-based drug self-delivery system promises the development of efficacious combination treatments against cancer, that integrate cell sensitization with existing anticancer modules (e.g., chemotherapy and PDT) for enhanced therapeutic efficacy. STATEMENT OF SIGNIFICANCE: This study reports the design and synthesis of a lonidamine (LND)-derived self-assembling peptide (LND-K) that dually targets integrin receptors and mitochondria of cancer cells. Under the precision guidance of a mitochondria-targeting sequence, LND-K-containing nanofibers target mitochondria and ablate mitochondrial functions. On one hand, the targeted delivery of LND-K reduces cell viabilities through a chemotherapy route; on the other hand, LND-K sensitizes cancer cells for subsequent PDT treatment with enhanced efficacy, which is mediated by induction of ROS, loss of mitochondrial membrane potential, and decrease of cellular ATP level. We believe that the design of mitochondria-targeted drug delivery systems with a self-assembling molecule provides a new approach to potentiate cytotoxicity of photosensitizers in a low-dose PDT module.

Enzymatic Synthesis of Peptide Nanofibers for Self-Delivery of Indomethacin and Tyroservatide in Cancer Therapy

Non-steroidal anti-inflammatory drugs (NSAIDs) have drawn considerable attention in the field of cancer treatment, yet these drugs display limited potency and selectivity against cancer cells. To address these problems, we designed a peptide-based self-delivery system [Indomethacin-Phe-Phe-Tyr (H₂PO₃)-Ser-Val, IDM-FFpYSV] that combines an NSAID molecule (indomethacin, or IDM) and a segment of anticancer tripeptide (tyroservatide, or YSV). IDM-FFpYSV is capable of self-assembling in an aqueous solution to afford nanofibrillar hydrogels under the catalysis of alkaline phosphatases (ALPs), which are overexpressed on the plasma membrane of cancer cells. The IDM-FFpYSV + ALP hydrogel displays a continuous release profile of peptide drugs, whereas a solution mixture of pure drugs (IDM-OH + pYSV + ALP) shows burst release of drug moieties. The treatment of IDM-FFpYSV selectively inhibits the proliferation of HeLa cells in vitro, with precise regulations of intracellular targeting proteins (COX-2 and AC-H3). The enhanced potency and selectivity of IDM-FFpYSV are found to be attributed to enhanced cellular uptake of peptide drugs, which involves a caveolae-mediated endocytosis pathway. Furthermore, intravenous administration of the IDM-FFpYSV formulation significantly inhibits the tumor growth in a HeLa-xenografted mouse model, whereas treatment of solution mixtures of pure drugs (IDM-OH + pYSV) fails to do so. Taken together, the study provides a viable strategy to augment anticancer efficacies of self-delivery system through molecular integration of multiple anticancer elements with an enzyme-instructed self-assembly process.

RNA-Seq Technology Reveals the Mechanism of SDT Combined With Novel Nanobubbles Against HCC

Sonodynamic therapy is widely used in the treatment and research of hepatocellular carcinoma. A novel targeted nanobubble complex mediated with Hematoporphyrin monomethyl ether and Lonidamine was structured as a sensitizer, characterized the properties, and studied the therapeutic effect on hepatocellular carcinoma. The complexes can promote the apoptosis of hepatocellular carcinoma cells and work better in combination with sonodynamic therapy. The differential expression of multiple types of RNA in hepatocellular carcinoma with sonodynamic therapy can be identified accurately with high-throughput RNA sequencing. The differential expressions of mRNA, lncRNA, and circRNA were analyzed by RNA-Seq. The enrichment analyses (Gene Ontology and KEGG) prompted the meaningful genes and pathways in the process of sonodynamic therapy in hepatocellular carcinoma cells. HMME-LND@C3F8-NBs conjugated with ultrasound is confirmed efficiently for inhibiting the development of hepatocellular carcinoma cells, and it is a combination of multiple genes and mechanisms.

From structure to application: Progress and opportunities in peptide materials development

For over 20 years, peptide materials in their hydrogel or soluble fibril form have been used for biomedical applications such as drug delivery, cell culture, vaccines, and tissue regeneration. To facilitate the translation of these materials, key areas of research still need to be addressed. Their structural characterization lags compared to amyloid proteins. Many of the structural features designed to guide materials formation are primarily being characterized by their observation in atomic resolution structures of amyloid assemblies. Herein, these motifs are examined in relation to peptide designs identifying common interactions that drive assembly and provide structural specificity. Current efforts to design complex structures, as reviewed here, highlight the need to extend the structural revolution of amyloid proteins to peptide assemblies to validate design principles. With respect to clinical applications, the fundamental interactions and responses of proteins, cells, and the immune system to peptide materials are still not well understood. Only a few trends are just now emerging for peptide materials interactions with biological systems. Understanding how peptide material properties influence these interactions will enable the translation of materials towards current and emerging applications.

GSH-Responsive Nanoprodrug to Inhibit Glycolysis and Alleviate Immunosuppression for Cancer Therapy

Blocking energy metabolism of cancer cells and simultaneously stimulating the immune system to perform immune attack are significant for cancer treatment. However, how to potently deliver different drugs with these functions remains a challenge. Herein, we synthesized a nanoprodrug formed by a F127-coated drug dimer to inhibit glycolysis of cancer cells and alleviate the immunosuppressive microenvironment. The dimer was delicately constructed to connect lonidamine (LND) and NLG919 by a disulfide bond which can be cleaved by excess GSH to release two drugs. LND can decrease the expression of hexokinase II and destroy mitochondria to restrain glycolysis for energy supply. NLG919 can reduce the accumulation of kynurenine and the number of regulatory T cells, thus alleviating the immunosuppressive microenvironment. Notably, the consumption of GSH by disulfide bond increased the intracellular oxidative stress and triggered immunogenic cell death of cancer cells. This strategy can offer more possibilities to explore dimeric prodrugs for synergistic cancer therapy.

The Potential of Lonidamine in Combination with Chemotherapy and Physical Therapy in Cancer Treatment

Simple Summary

The unique characteristics of tumor energy metabolism (highly dependent on aerobic glycolysis, namely, the Warburg effect) make it an interesting and attractive target for drug discovery. Radio- and chemoresistance are closely associated with the Warburg effect. Lonidamine (LND), as a glycolytic inhibitor, although having low anticancer activity when used alone, exhibits selectivity to various tumors, and its adverse effects do not overlap when combined with other chemotherapeutic drugs. Therefore, LND may be very promising as a sensitizer of tumors to chemotherapeutic agents and physical therapies. This review summarizes the advance of LND in combination with chemotherapy and physical therapy over the past several decades, as well as the promising LND derivative adjudin (ADD). The underlying sensitizing mechanisms were also analyzed and discussed, which may contribute to an improved therapeutic effect in future clinical cancer treatment.

Abstract

Lonidamine (LND) has the ability to resist spermatogenesis and was first used as an anti-spermatogenic agent. Later, it was found that LND has a degree of anticancer activity. Currently, LND is known to target energy metabolism, mainly involving the inhibition of monocarboxylate transporter (MCT), mitochondrial pyruvate carrier (MPC), respiratory chain complex I/II, mitochondrial permeability transition (PT) pore, and hexokinase II (HK-II). However, phase II clinical studies showed that LND alone had a weak therapeutic effect, and the effect was short and reversible. Interestingly, LND does not have the common side effects of traditional chemotherapeutic drugs, such as alopecia and myelosuppression. In addition, LND has selective activity toward various tumors, and its toxic and side effects do not overlap when combined with other chemotherapeutic drugs. Therefore, LND is commonly used as a chemosensitizer to enhance the antitumor effects of chemotherapeutic drugs based on its disruption of energy metabolism relating to chemo- or radioresistance. In this review, we summarized the combination treatments of LND with several typical chemotherapeutic drugs and several common physical therapies, such as radiotherapy (RT), hyperthermia (HT), and photodynamic therapy (PDT), and discussed the underlying mechanisms of action. Meanwhile, the development of novel formulations of LND in recent years and the research progress of LND derivative adjudin (ADD) as an anticancer drug were also discussed.

Biomaterials based on noncovalent interactions of small molecules

Unlike conventional materials that covalent bonds connecting atoms as the major force to hold the materials together, supramolecular biomaterials rely on noncovalent intermolecular interactions to assemble. The reversibility and biocompatibility of supramolecular biomaterials render them with diverse range of functions and lead to rapid development in the past two decades. This review focuses on the noncovalent and enzymatic control of supramolecular biomaterials, with the introduction to various triggering mechanism to initiate self-assembly. Representative applications of supramolecular biomaterials are highlighted in four categories: tissue engineering, cancer therapy, drug delivery, and molecular imaging. By introducing various applications, we intend to show enzymatic control and noncovalent interactions as a powerful tool for achieving spatiotemporal control of biomaterials both invitro and in vivo for biomedicine.

Enzymatic Noncovalent Synthesis

Enzymatic reactions and noncovalent (i.e., supramolecular) interactions are two fundamental nongenetic attributes of life. Enzymatic noncovalent synthesis (ENS) refers to a process where enzymatic reactions control intermolecular noncovalent interactions for spatial organization of higher-order molecular assemblies that exhibit emergent properties and functions. Like enzymatic covalent synthesis (ECS), in which an enzyme catalyzes the formation of covalent bonds to generate individual molecules, ENS is a unifying theme for understanding the functions, morphologies, and locations of molecular ensembles in cellular environments. This review intends to provide a summary of the works of ENS within the past decade and emphasize ENS for functions. After comparing ECS and ENS, we describe a few representative examples where nature uses ENS, as a rule of life, to create the ensembles of biomacromolecules for emergent properties/functions in a myriad of cellular processes. Then, we focus on ENS of man-made (synthetic) molecules in cell-free conditions, classified by the types of enzymes. After that, we introduce the exploration of ENS of man-made molecules in the context of cells by discussing intercellular, peri/intracellular, and subcellular ENS for cell morphogenesis, molecular imaging, cancer therapy, and other applications. Finally, we provide a perspective on the promises of ENS for developing molecular assemblies/processes for functions. This review aims to be an updated introduction for researchers who are interested in exploring noncovalent synthesis for developing molecular science and technologies to address societal needs.

Hyaluronic acid-shelled, peptide drug conjugate-cored nanomedicine for the treatment of hepatocellular carcinoma

Peptide-drug conjugate (PDC) is a promising prodrug in drug delivery systems. To fabricate nanostructures with proper molecular design which can self-assemble to spherical morphologies is very important for PDC chemotherapy. In this study, a novel PDC (PDC-DOX₂), in which two doxorubicin (DOX) molecules are conjugated onto a short peptide (KIGLFRWR) with self-assembly function, was designed and synthesized. PDC-DOX₂ with self-assembly properties forms a spherical structure under hydrophobic interaction in water. Hyaluronic acid (HA) was then coated on PDC-DOX₂ micelles to form a HA-shelled, peptide-doxorubicin conjugate-cored nanomedicine (HA@PDC-DOX₂). The amount of HA can regulate the particle size and stabilization of HA@PDC-DOX₂. In addition, HA can actively enhance the targeting effects of PDC-DOX₂ micelles since it can interact with overexpressed receptors in cancer cells. The core-shell structured HA@PDC-DOX₂ nanomedicine showed significantly enhanced potency against hepatocellular carcinoma compared to PDC-DOX₂ micelles as well as free DOX. In this work, a novel PDC which can self-assemble to spherical morphologies and a core-shell structure HA@PDC-DOX₂ nanomedicine are designed and prepared. It provides a convenient strategy for the size control of PDC assemblies and constructs effective PDC-based drug delivery systems for cancer treatment.

β-Galactosidase instructed self-assembly of supramolecular bolaamphiphiles hydrogelators

β-Galactosidase instructed supramolecular assemblies of Low Molecular Weight Gelators (LMWGs) derived from glyconucleo-bolaamphiphiles have been designed. These precursors, comprising galactose sensitive units at both polar heads, showed the formation of hydrogels upon the action of β-galactosidase.

Self-Assembled Organic Nanomaterials for Drug Delivery, Bioimaging, and Cancer Therapy

Over the past few decades, tremendous progress has been made in the development of engineering nanomaterials, which opened new horizons in the field of diagnosis and treatment of various diseases. In particular, self-assembled organic nanomaterials with intriguing features including delicate structure tailoring, facile processability, low cost, and excellent biocompatibility have shown outstanding potential in biomedical applications because of the enhanced permeability and retention (EPR) effect and multifunctional properties. In this review, we briefly introduce distinctive merits of self-assembled organic nanomaterials for biomedical applications. The main focus will be placed on summarizing recent advances in self-assembled organic nanomedicine for drug delivery, bioimaging, and cancer phototherapy, followed by highlighting a critical perspective on further development of self-assembled organic nanomaterials for future clinical translation. We believe that the above themes will appeal to researchers from different fields, including material, chemical, and biological sciences, as well as pharmaceutics.