Stimuli-Responsive Conformational Transformation of Peptides for Tunable Cytotoxicity

Host-Guest Adduct as a Stimuli-Responsive Prodrug: Enzyme-Triggered Self-Assembly Process of a Short Peptide Within Mitochondria to Induce Cell Apoptosis

To address the issue of nonspecific biodistribution of a chemotherapeutic drug, stable [2]pseudorotaxane complexes (PK@CAOPP and PR@CAOPP) are used to demonstrate a proof of concept. Cationic -PPh3 + moiety in CAOPP allows specific localization of the PK@CAOPP/ PR@CAOPP in the mitochondrial membrane (MM). Electrostatic interaction between the cationic LysinePK or ArgininePR moiety and the negatively charged phosphoesterCAOPP functionality in CAOPP favours strong adduct formation. The ALP-induced hydrolytic cleavage of the phosphoester moiety in cancer cells triggers dephosphorylation and releases PK/ PR moiety from PK@CAOPP/PR@CAOPP. PK or PR, derived from the Phe-Phe dipeptide, formed fibril-like molecular aggregates in the MM to induce dysfunction, depolarization, ROS generation and apoptotic MCF7 cell death. Such phenomena were not observed in ALP-negative HEK293 normal cells. These propositions were confirmed through control studies using NBDK and PE, other guest molecules. Smaller size and inclusion of the short peptides (PK or PR) within the hydrophobic interior of CAOPP, were attributed to their stability in blood serum. Thus, we have demonstrated the use of supramolecular adducts as a potential therapeutic option for treating cancer cells without affecting healthy cells. The efficacy was also established with an in-vivo MCF7 tumour xenograft model using Balb/c nude mice.

Targeting mitochondria in Cancer therapy: Machine learning analysis of hyaluronic acid-based drug delivery systems

BACKGROUND

Mitochondrial alterations play a crucial role in the development and progression of cancer. Dysfunctional mitochondria contribute to the acquisition of key hallmarks of cancer, including sustained proliferative signaling, evasion of growth suppressors, and resistance to cell death. Consequently, targeting mitochondrial dysfunction has emerged as a promising therapeutic strategy. Hyaluronic acid (HA), a naturally occurring glycosaminoglycan, has garnered significant attention due to its multifaceted roles in cancer biology.

METHODS

We employed a Systematic Literature Review (SLR) approach to examine a collection of 90 scientific publications using a text mining technique leveraging the Latent Dirichlet Allocation (LDA) algorithm.

RESULTS

The result of this activity, performed through the MySLR digital platform, allowed us to identify a set of two distinct topics representing the research domain. Specifically, Topic 1 comprised 41 papers, while Topic 2 comprised 49 papers.

CONCLUSIONS

The computational analysis highlighted that the integration of HA into drug delivery systems represents a promising approach to enhance the effectiveness and safety of cancer therapies. The discussed clinical trials provided compelling evidence of the potential of HA-based treatments in targeting cancer cells while minimizing adverse effects on healthy tissues.

Folic Acid-Functionalized β-Cyclodextrin for Delivery of Organelle-Targeted Peptide Chemotherapeutics in Cancer

Recent emphasis on the design of drug delivery systems typically involves the effective transport of a pharmaceutical substance to the disease site with the desired therapeutic efficacy and minimal cytotoxicity. Organelle-targeted peptides have become an integral part of designing an important class of prodrug/prodrug assemblies for new supramolecular therapeutics owing to their favorable biocompatibility, synthetic ease, tunability of their aggregation behavior, and desired functionalization for site-specificity. However, it is still limited due to the low selectivity. We designed a folic acid-functionalized β-cyclodextrin (FA-CD) as a delivery platform for specific and selective delivery of organelle-targeted (such as microtubule, lysosome, and mitochondria) peptide chemotherapeutics to the folate receptor (FR) overexpressing cancer cell lines. Low toxicity was found for the FA-CD and organelle-targeted peptide inclusion complex in FR-negative normal cells, but superior inhibition of tumor growth with no in vivo toxicity was found for the inclusion complex in the xenograft tumor model.

Harnessing a bis-electrophilic boronic acid lynchpin for azaborolo thiazolidine (ABT) grafting in cyclic peptides

Chemical modifications of native peptides have significantly advanced modern drug discovery in recent decades. On this front, the installation of multitasking molecular grafts onto macrocyclic peptides offers numerous opportunities in biomedical applications. Here, we showcase a new class of borono-cyclic peptides featuring an azaborolo thiazolidine (ABT) graft, which can be readily assembled utilizing a bis-electrophilic boronic acid lynchpin while harnessing the inherent reactivity difference (>103 M-1 s-1) between the N-terminal cysteine and backbone cysteine for rapid and highly regioselective macrocyclization (∼1 h) under physiological conditions. The ABT-crosslinked peptides are fairly stable in endogenous environments, but can provide the linear diazaborine peptides via treatment with α-nucleophiles. This efficient peptide crosslinking protocol was further extended for regioselective bicyclizations and engineering of α-helical structures. Finally, ABT-grafted peptides were exploited in biorthogonal conjugation, leading to highly effective intracellular delivery of an apoptotic peptide (KLA) in cancer cells. The mechanism of action by which ABT-grafted KLA peptide induces apoptosis was also explored.

Precisely Activating cGAS-STING Pathway with a Novel Peptide-Based Nanoagonist to Potentiate Immune Checkpoint Blockade Cancer Immunotherapy

As an essential intracellular immune activation pathway, the cGAS-STING pathway has attracted broad attention in cancer treatment. However, low bioavailability, nonspecificity, and adverse effects of small molecule STING agonists severely limit their therapeutic efficacy and in vivo application. In this study, a peptide-based STING agonist is first proposed, and KLA is screened out to activate the cGAS-STING pathway by promoting mitochondrial DNA (mtDNA) leakage. To precisely activate the cGAS-STING pathway and block the PD-1/PD-L1 pathway, a multi-stimuli activatable peptide nanodrug (MAPN) is developed for the effective delivery of KLA and PD-L1 antagonist peptide (CVR). With rational design, MAPN achieved the site-specific release of KLA and CVR in response to multiple endogenous stimuli, simultaneously activating the cGAS-STING pathway and blocking PD-1/PD-L1 pathway, ultimately initiating robust and durable T cell anti-tumor immunity with a tumor growth inhibition rate of 78% and extending the median survival time of B16F10 tumor-bearing mice to 40 days. Overall, antimicrobial peptides, which can promote mtDNA leakage through damaging mitochondrial membranes, may be potential alternatives for small molecule STING agonists and giving a new insight for the design of novel STING agonists. Furthermore, MAPN presents a universal delivery platform for the effective synergy of multiple peptides.

Screening, Construction, and Preliminary Evaluation of CLDN18.2-Specific Peptides for Noninvasive Molecular Imaging

Recent global clinical trials have shown that CLDN18.2 is an ideal target for the treatment of gastric cancer and that patients with high CLDN18.2 expression can benefit from targeted therapy. Therefore, accurate and comprehensive detection of CLDN18.2 expression is important for patient screening and guidance in anti-CLDN18.2 therapy. Phage display technology was used to screen CLDN18.2-specific peptides from 100 billion libraries. 293TCLDN18.1 cells were used to exclude nonspecific binding and CLDN18.1 binding sequences, while 293TCLDN18.2 cells were used to screen CLDN18.2-specific binding peptides. The monoclonal clones obtained from phage screening were sequenced, and peptides were synthesized based on the sequencing results. Binding specificity and affinity were assessed with a fluorescein isothiocyanate (FITC)-conjugated peptide. A 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated peptide was also synthesized for 68Ga radiolabeling. The in vitro and in vivo stability, partition coefficients, in vivo molecular imaging, and biodistribution were also characterized. Overall, 54 monoclonal clones were selected after phage display screening. Subsequently, based on the cell ELISA results, CLDN18.2 preference monoclonal clones were selected for deoxyribonucleic acid (DNA) sequencing, and four 7-peptide sequences were obtained after sequence comparison; among them, a peptide named T37 was further validated in vitro and in vivo. The T37 peptide specifically recognized CLDN18.2 but not CLDN18.1 and bound strongly to CLDN18.2-positive cell membranes. The 68Ga-DOTA-T37 probe exhibits good in vitro properties and high stability as a hydrophilic probe; it has high biological safety, and positron emission tomography/computed tomography (PET/CT) studies have shown that it can specifically target CLDN18.2 protein and CLDN18.2-positive tumors in mice. 68Ga-DOTA-T37 demonstrated the superiority and feasibility of using a CLDN18.2-specific probe in PCT/CT imaging, which deserves further development and exploitation.

Strategies for Improving Peptide Stability and Delivery

Peptides play an important role in many fields, including immunology, medical diagnostics, and drug discovery, due to their high specificity and positive safety profile. However, for their delivery as active pharmaceutical ingredients, delivery vectors, or diagnostic imaging molecules, they suffer from two serious shortcomings: their poor metabolic stability and short half-life. Major research efforts are being invested to tackle those drawbacks, where structural modifications and novel delivery tactics have been developed to boost their ability to reach their targets as fully functional species. The benefit of selected technologies for enhancing the resistance of peptides against enzymatic degradation pathways and maximizing their therapeutic impact are also reviewed. Special note of cell-penetrating peptides as delivery vectors, as well as stapled modified peptides, which have demonstrated superior stability from their parent peptides, are reported.

Tuning of Peptide Cytotoxicity with Cell Penetrating Motif Activatable by Matrix Metalloproteinase-2

Although diverse cell penetrating motifs not only from naturally occurring proteins but also from synthetic peptides have been discovered and developed, the selectivity of cargo delivery connected to these motifs into the desired target cells is generally low. Here, we demonstrate the selective cytotoxicity tuning of an anticancer KLA peptide with a cell penetrating motif activatable by matrix metalloproteinase-2 (MMP2). The anionic masking sequence introduced at the end of the KLA peptide through an MMP2-cleavable linker is selectively cleaved by MMP2 and the cationic cell penetrating motif is activated. Upon treatment of the peptide to H1299 cells (high MMP2 level), it is selectively internalized into the cells by MMP2, which consequently induces membrane disruption and cell death. In contrast, the peptide shows negligible cytotoxicity toward A549 cancer cells with low MMP2 levels. Furthermore, the selective therapeutic efficacy of the peptide induced by MMP2 is also corroborated using in vivo study.

Spatial Distribution Control of Antimicrobial Peptides through a Novel Polymeric Carrier for Safe and Efficient Cancer Treatment

Antimicrobial peptides (AMPs) hold great potential for use in tumor treatment. However, developing AMP-based antitumor therapies is challenging due to circulatory instability, hemolytic toxicity, low selectivity, and poor cell permeability of AMPs. In this study, a polymeric carrier for AMPs (denoted as PAMP_m -co-PPBE_n /PCA) is presented that effectively enhances their anticancer efficacy while minimizing their potential side effects. By integrating multiple responsive structures at the molecular level, the carrier finely controls the spatial distribution of AMPs in different biological microenvironments, thereby effectively modulating their membranolytic ability. Upon employing KLA as the model AMP, the polymeric carrier's hemolytic toxicity during blood circulation is suppressed, its cellular internalization when reaching tumor tissues facilitated, and its membranolytic toxicity toward the mitochondria upon entering cancer cells restored and further enhanced. Animal studies indicate that this approach significantly improves the antitumor efficacy of KLA and reduces its toxicity. Considering that the loading method for most AMPs is identical to that of KLA, the polymeric carrier reported in this study may provide a feasible approach for the development of AMP-based cancer treatments.

Induced cytotoxicity of peptides by intracellular native chemical ligation

The intracellular NCL reaction of peptide with both N-terminal cysteine and C-terminal crypto-thioester with protecting groups occurs naturally in cancer cells, which endows peptide with induced cytotoxicity.

Molecular engineering of antimicrobial peptide (AMP)-polymer conjugates

As antimicrobial resistance becomes an increasing threat, bringing significant economic and health burdens, innovative antimicrobial treatments are urgently needed. While antimicrobial peptides (AMPs) are promising therapeutics, exhibiting high activity against resistant bacterial strains, limited stability and toxicity to mammalian cells has hindered clinical development. Attaching AMPs to polymers provides opportunities to present AMPs in a way that maximizes bacterial killing while enhancing compatibility with mammalian cells, stability, and solubility. Conjugation of an AMP to a linear hydrophilic polymer yields the desired improvements in stability, mammalian cell compatibility, and solubility, yet often markedly reduces bactericidal effects. Non-linear polymer architectures and supramolecular assemblies that accommodate multiple AMPs per polymer chain afford AMP-polymer conjugates that strike a superior balance of antimicrobial activity, mammalian cell compatibility, stability, and solubility. Therefore, we review the design criteria, building blocks, and synthetic strategies for engineering AMP-polymer conjugates, emphasizing the connection between molecular architecture and antimicrobial performance to inspire and enable further innovation to advance this emerging class of biomaterials.

Proapoptotic Peptide Brush Polymer Nanoparticles via Photoinitiated Polymerization-Induced Self-Assembly

Herein, we report the photoinitiated polymerization-induced self-assembly (photo-PISA) of spherical micelles consisting of proapoptotic peptide-polymer amphiphiles. The one-pot synthetic approach yielded micellar nanoparticles at high concentrations and at scale (150 mg mL-1 ) with tunable peptide loadings up to 48 wt. %. The size of the micellar nanoparticles was tuned by varying the lengths of hydrophobic and hydrophilic building blocks. Critically, the peptide-functionalized nanoparticles imbued the proapoptotic "KLA" peptides (amino acid sequence: KLAKLAKKLAKLAK) with two key properties otherwise not inherent to the sequence: 1) proteolytic resistance compared to the oligopeptide alone; 2) significantly enhanced cell uptake by multivalent display of KLA peptide brushes. The result was demonstrated improved apoptosis efficiency in HeLa cells. These results highlight the potential of photo-PISA in the large-scale synthesis of functional, proteolytically resistant peptide-polymer conjugates for intracellular delivery.

Stimulus-responsive conformational transformation of peptide with cell penetrating motif for triggered cytotoxicity

A modified KLA peptide with an intramolecular disulfide bond and a cell penetrating sequence is developed for enhanced intracellular uptake and triggered selective cytotoxicity towards cancer cells by stimulus-responsive conformational transformation.

Stimuli-responsive conformational transformation of antimicrobial peptides stapled with an azobenzene unit

The effect of the azobenzene-stapling position on the triggered transformation of the helical conformation of KLA peptides in response to UV irradiation and reductive cleavage is investigated.