Using porphyrins as albumin-binding molecules to enhance antitumor efficacies and reduce systemic toxicities of antimicrobial peptides

Versatile Peptide-Based Nanosystems for Photodynamic Therapy

Photodynamic therapy (PDT) has become an important therapeutic strategy because it is highly controllable, effective, and does not cause drug resistance. Moreover, precise delivery of photosensitizers to tumor lesions can greatly reduce the amount of drug administered and optimize therapeutic outcomes. As alternatives to protein antibodies, peptides have been applied as useful targeting ligands for targeted biomedical imaging, drug delivery and PDT. In addition, other functionalities of peptides such as stimuli responsiveness, self-assembly, and therapeutic activity can be integrated with photosensitizers to yield versatile peptide-based nanosystems for PDT. In this article, we start with a brief introduction to PDT and peptide-based nanosystems, followed by more detailed descriptions about the structure, property, and architecture of peptides as background information. Finally, the most recent advances in peptide-based nanosystems for PDT are emphasized and summarized according to the functionalities of peptide in the system to reveal the design and development principle in different therapeutic circumstances. We hope this review could provide useful insights and valuable reference for the development of peptide-based nanosystems for PDT.

Self-Penetrating Oligonucleotide Derivatives: Features of Self-Assembly and Interactions with Serum and Intracellular Proteins

Lipophilic oligonucleotide derivatives are a potent approach to the intracellular delivery of nucleic acids. The binding of these derivatives to serum albumin is a determinant of their fate in the body, as its structure contains several sites of high affinity for hydrophobic compounds. This study focuses on the features of self-association and non-covalent interactions with human serum albumin of novel self-penetrating oligonucleotide derivatives. The study revealed that the introduction of a triazinyl phosphoramidate modification bearing two dodecyl groups at the 3' end region of the oligonucleotide sequence has a negligible effect on its affinity for the complementary sequence. Dynamic light scattering verified that the amphiphilic oligonucleotides under study can self-assemble into micelle-like particles ranging from 8 to 15 nm in size. The oligonucleotides with dodecyl groups form stable complexes with human serum albumin with a dissociation constant of approximately 10-6 M. The oligonucleotide micelles are simultaneously destroyed upon binding to albumin. Using an electrophoretic mobility shift assay and affinity modification, we examined the ability of DNA duplexes containing triazinyl phosphoramidate oligonucleotides to interact with Ku antigen and PARP1, as well as the mutual influence of PARP1 and albumin or Ku antigen and albumin upon interaction with DNA duplexes. These findings, together with the capability of dodecyl-containing derivatives to effectively penetrate different cells, such as HEK293 and T98G, indicate that the oligonucleotides under study can be considered as a platform for the development of therapeutic preparations with a target effect.

Exploring the mechanism of photosensitizer conjugation on membrane perturbation of antimicrobial peptide: A multiscale molecular simulation study

Antimicrobial peptides (AMPs) exert their biological functions by perturbation with cellular membrane. Conjugation of AMPs with photosensitizer (PS) is a promising strategy for enhancing the efficacy and reducing systemic toxicity of AMPs. However, it is still elusive how the conjugated PS impacts the perturbation of AMPs on cell membrane from molecular level. Here, we addressed this issue by a multiscale computational strategy on pyropheophorbide-a (PPA) conjugated K6L9 (PPA-K6L9), a PS-AMP conjugate developed by us previously. Our atomistic molecular dynamics (MD) simulations revealed that the porphyrin moiety of PPA enhanced the stability of the conjugate in a lipid bilayer membrane model. Moreover, such moiety also maintained the amphipathic structure of K6L9, which is crucial for membrane pore formation. Coarse-grained MD simulations further showed that the conjugates aggregated in membrane environment and formed more stable toroidal pores with respect to K6L9 alone, suggesting the conjugation of PPA may enhance the membrane-disruption activity of K6L9. Consistent with this, our cellular experiments confirmed that PPA-K6L9 was more toxic to 4 T1 tumor cells than K6L9. This study provides insights into the mechanism by which PS-AMP conjugates disrupt cellular membranes and could aid in the design of more potent AMP conjugates.

A Serum-Stable supramolecular drug carrier for chemotherapeutics fabricated by a Peptide-Photosensitizer conjugate

Supramolecular assemblies fabricated by peptide-photosensitizer conjugates have attracted increasing attentions in recent years as drug carriers for chemotherapeutics (CTs). However, these assemblies have been known to suffer from disintegration by serum components leading to off-target drug release, and thereby impairing antitumor effects and causing systemic toxicities. To address this problem, this study reports a nano-architectural self-assembly peptide-photosensitizer carrier (NSPC) fabricated by conjugating a phthalocyanine derivative (MCPZnPc) and ε-poly-l-lysine (EPL). By engineering the core and peripheral interactions, MCPZnPC-EPL (M-E) NSPC firmly encapsulated multiple CTs, creating CT@M-E NSPCs that were highly stable against disintegration in serum. More importantly, CT@M-E NSPCs exhibited controlled release of CTs in tumor tissues. The antitumor effects of CTs were further promoted by the synergism with the reactivated photodynamic effect. Furthermore, M-E NSPC-encapsulation optimized CTs' biodistribution reducing adverse effects in vivo. This study provides a serum-stable supramolecular drug delivery system with photodynamic effect, which is applicable for a broad-range of CTs to promote antitumor effects and ameliorate adverse effects.

Conjugation as a Tool in Therapeutics: Role of Amino Acids/Peptides-Bioactive (Including Heterocycles) Hybrid Molecules in Treating Infectious Diseases

Peptide-based drugs are gaining significant momentum in the modern drug discovery, which is witnessed by the approval of new drugs by the FDA in recent years. On the other hand, small molecules-based drugs are an integral part of drug development since the past several decades. Peptide-containing drugs are placed between small molecules and the biologics. Both the peptides as well as the small molecules (mainly heterocycles) pose several drawbacks as therapeutics despite their success in curing many diseases. This gap may be bridged by utilising the so called 'conjugation chemistry', in which both the partners are linked to one another through a stable chemical bond, and the resulting conjugates are found to possess attracting benefits, thus eliminating the stigma associated with the individual partners. Over the past decades, the field of molecular hybridisation has emerged to afford us new and efficient molecular architectures that have shown high promise in medicinal chemistry. Taking advantage of this and also considering our experience in this field, we present herein a review concerning the molecules obtained by the conjugation of peptides (amino acids) to small molecules (heterocycles as well as bioactive compounds). More than 125 examples of the conjugates citing nearly 100 references published during the period 2000 to 2022 having therapeutic applications in curing infectious diseases have been covered.

Conjugates of Tetrapyrrolic Macrocycles as Potential Anticancer Target-Oriented Photosensitizers

Photodynamic therapy is a minimally invasive treatment of tumors using photosensitizers, light, and reactive oxygen species, which can destroy cellular structures. With the development of photodynamic therapy, significant efforts have been made to create new efficient photosensitizers with improved delivery to cells, stability, and selectivity against cancer tissues. Naturally occurring tetrapyrrolic macrocycles, such as porphyrins and chlorins, are very attractive as photosensitizers, and their structural modification and conjugation with other biologically active molecules are promising approaches for creating new photosensitizers specifically targeting cancer cells. The present review aims to highlight recent developments in the design, preparation, and investigation of complex conjugates of tetrapyrrolic macrocycles, which can potentially be used as sensitizers for target-oriented photodynamic therapy of cancer. In this review, we discuss the structure, photodynamic effect, and anticancer activity of the following conjugates of tetrapyrrolic macrocycles: (1) conjugates obtained by modifying peripheral substituents in porphyrins and chlorins; (2) conjugates of porphyrins and chlorins with lipids, carbohydrates, steroids, and peptides; (3) conjugates of porphyrins and chlorins with anticancer drugs and some other biologically active molecules; (4) metal-containing conjugates. The question of how the conjugate structure affects its specificity, internalization, localization, and photoinduced toxicity within cancer cells is the focus of this review.

Nafamostat Mesylate in Combination with the Mouse Amino-Terminal Fragment of Urokinase-Human Serum Albumin Improves the Treatment Outcome of Triple-Negative Breast Cancer Therapy

Triple-negative breast cancer (TNBC) is highly aggressive and causes a higher proportion of metastatic cases. However, therapies directed to specific molecular targets have rarely achieved clinically meaningful improvements in the outcome of TNBC therapy. A urokinase-type plasminogen activator (uPA), one of the best-validated biomarkers of breast cancer, is an extracellular proteolytic serine protease involved in many pathological and physiological processes, including tumor cell invasion and metastasis. Nafamostat mesylate (NM) is a synthetic compound that inhibits various serine proteases and has been used as a therapeutic agent for the treatment of TNBC. Nevertheless, NM has poor specificity for serine proteases and is easy be hydrolyzed; moreover, the inhibitory mechanism of TNBC therapy is unclear. In this study, we combine NM with a macromolecular drug delivery vehicle, mouse amino-terminal fragment of urokinase-human serum albumin (mATF-HSA), to form a complex (mATF-HSA:NM) using the dilution-incubation-purification method. mATF specifically targets uPAR overexpressed on the surface of TNBC cells; moreover, HSA prevents NM from being hydrolyzed by numerous serine proteases. mATF-HSA:NM showed stronger inhibitory effects on the proliferation and metastasis of TNBC in vitro and in vivo without significant cytotoxicity on normal cells and tissues. In addition, we demonstrated that NM mediates metastasis of TNBC cells through inhibition of uPA using a stable uPA knockdown cell line (MDA-MB231 shuPA). Overall, we have developed a macromolecular complex targeted to treat high uPAR-expressing tumor types, and mATF-HSA can potentially be used to load other types of drugs with tumor-targeting specificity for mouse tumor models and is a promising tool to study tumor biology in mouse tumor models.

Bioinspired porphyrin-peptide supramolecular assemblies and their applications

Inspired by the hierarchical chiral assembly of porphyrin-proteins in photosynthetic systems, the hierarchical self-assembly of porphyrin-amino acids/peptides provides a novel strategy for constructing functional materials. How to artificially simulate the assembly of porphyrins, proteins, and other cofactors in the photosynthesis system to obtain persistent strong light capture, charge separation and catalytic reactions has become an important concern in the construction of biomimetic photosynthesis systems. This paper summarizes the different assembly strategies adopted in recent years, the effects of driving forces on self-assembly, and the application of porphyrin-peptides in catalysis and biomedicine, and briefly discusses the challenges and prospects for future research.

A camptothecin-based, albumin-binding prodrug enhances efficacy and safety in vivo

The albumin-based drug delivery system is an effective drug delivery strategy for traditional chemotherapeutic drugs that can improve their antitumour efficacies and reduce systemic toxicities. The camptothecin derivative CPTS0001 has excellent antitumour activity in vitro, but it shows toxicity and side effects in vivo. In this study, we report the synthesis and biological evaluation of the β-glucuronidase-reactive albumin-binding prodrug Mal-glu-CPTS0001 based on quaternary ammonium. After intravenous administration, the compound covalently binds to plasma albumin through Michael addition, enabling it to accumulate in tumours, where tumour-associated β-glucuronidase triggers the selective release of CPTS0001. This prodrug significantly reduced the toxicity of the parent drug, and the maximum tolerated dose was increased by 2.5 times. At the same time, this prodrug enhanced the selectivity in vivo and improved the preferential accumulation of prodrug in tumours. Notably, this prodrug exhibited excellent in vivo antitumour effects in a murine breast cancer xenograft model without visible pathological toxicity.