Recent Advances of Cell-Penetrating Peptides and Their Application as Vectors for Delivery of Peptide and Protein-Based Cargo Molecules

A peptide conjugate enables systemic injection of the morpholino inducer and more durable induction of T3H38 ribozyme-controlled AAV transgene in mice

Genetic switches that allow for precise control over transgene expression timing or levels may improve the safety and expand the use of adeno-associated viral (AAV) vector-based gene therapy technologies. We previously engineered an efficient RNA switch system that comprises a novel self-cleaving ribozyme (T3H38) and an octaguanidine dendrimer-conjugated morpholino oligonucleotide (v-M8) complementary to the ribozyme. This switch system can be used to efficiently regulate AAV-delivered transgenes with an up to 200-fold regulatory range in mice. However, this switch system has a relatively short induction half-life and only works well when v-M8 was locally but not systemically administered, representing two key limitations of the system. To address these issues, here, we tested replacing the octa-guanidine dendrimer in the v-M8 morpholino oligo with a cell-penetrating peptide (CPP). Two CPP-conjugated morpholino oligos (B-M8 and B-MSP-M8) were synthesized and compared with v-M8 for the induction of T3H38-regulated AAV-luciferase in mice. One of the CPP-conjugated oligos (B-MSP-M8) not only showed significantly improved induction half-life over that of v-M8, but also enabled efficient induction of AAV transgene expression when the oligo was systemically administered. This study improves in vivo performance and broadens the utility of the T3H38 ribozyme-based RNA switch system in gene therapy applications.

Surface modified proteins and peptides for targeted drug delivery

Surface modification of proteins and peptides has emerged as a promising strategy to enhance their therapeutic efficacy and target specificity. This chapter delves into the various techniques employed to modify the surface properties of these biomolecules, including chemical conjugation, site-specific mutagenesis, and peptide synthesis. The focus is on strategies that improve drug delivery to specific target sites, such as tumor cells or inflamed tissues. By modifying surface properties, it is possible to enhance drug stability, reduce immunogenicity, and prolong circulation time. This chapter explores the latest advancements in this field and discusses the potential applications of surface-modified proteins and peptides in the development of novel therapeutic agents.

DNA Dendron Tagging as a Universal Way to Deliver Proteins to Cells

The use of proteins as intracellular probes and therapeutic tools is often limited by poor intracellular delivery. One approach to enabling intracellular protein delivery is to transform proteins into spherical nucleic acid (proSNA) nanoconstructs, with surfaces chemically modified with a dense shell of radially oriented DNA that can engage with cell-surface receptors that facilitate endocytosis. However, proteins often have a limited number of available reactive surface residues for DNA conjugation such that the extent of DNA loading and cellular uptake is restricted. Indeed, DNA surface density and sequence have been correlated with scavenger-receptor engagement, the first step of cellular internalization. Here, we report how branched DNA dendrons with dibenzocyclooctyne groups and proteins genetically engineered to include the noncanonical amino acid azido-phenylalanine for click chemistry can be used to synthesize hybrid DNA dendron-protein architectures that exhibit outstanding cellular internalization properties, without the need for extensive surface modification. In a head-to-head comparison, protein-DNA dendron structures (where DNA is concentrated in a local area) are taken up by cells more rapidly and to a greater extent than proSNAs (where the DNA is evenly distributed). Also, protein-G-rich dendron structures show enhanced uptake compared to protein-T-rich dendron structures, highlighting the importance of oligonucleotide sequence on nanoconjugate uptake. Finally, a generalizable method for chemically tagging proteins with dendrons that does not require mutagenesis is described. When a range of proteins, spanning 42 to 464 kDa, were modified through surface lysines with this method, a significant increase in their cellular uptake (up to 17-fold) compared to proteins that are not coupled to a DNA dendron was observed.

Synthesis and Characterization of Transferrin and Cell-Penetrating Peptide-Functionalized Liposomal Nanoparticles to Deliver Plasmid ApoE2 In Vitro and In Vivo in Mice

Alzheimer's disease (AD) is a prevalent neurodegenerative condition characterized by the aggregation of amyloid-β plaques and neurofibrillary tangles in the brain, leading to synaptic dysfunction and neuronal degeneration. Recently, new treatment approaches involving drugs such as donanemab and lecanemab have been introduced for AD. However, these drug regimens have been associated with adverse effects, leading to the exploration of gene therapy as a potential treatment option. The apolipoprotein E (ApoE) isoforms (ApoE2, ApoE3, and ApoE4) play pivotal roles in AD pathology, with ApoE2 known for its protective effects against AD, making it a promising candidate for gene therapy interventions. However, delivering therapeutics across the blood-brain barrier (BBB) remains a crucial challenge in treating neurological disorders. Liposomes, lipid-based vesicles, are effective nanocarriers due to their ability to shield therapeutics from degradation, though they often lack specificity for brain delivery. To address this issue, liposomes were functionalized with cell-penetrating peptides such as penetratin (Pen), cingulin (Cgn), and a targeting ligand transferrin (Tf). This modification strategy aimed to enhance the delivery of therapeutic ApoE2 plasmids across the BBB to neurons, thereby increasing the level of ApoE2 protein expression. Experimental findings demonstrated that dual-functionalized liposomes (CgnTf and PenTf) exhibited higher cellular uptake, biodistribution, and transfection efficiency than single-functionalized (Pen, Cgn, or Tf) and nonfunctionalized liposomes. In vitro studies using primary neuronal cells, bEnd.3 cells, and primary astrocytes consistently supported these findings. Following a single dose treatment via tail vein administration in C57BL6/J mice, in vivo biodistribution results showed significantly higher biodistribution levels in the brain (∼12% ID/gram of tissue) for dual-functionalized liposomes. Notably, treatment with dual-functionalized liposomes resulted in a 2-fold increase in ApoE2 expression levels compared to baseline levels. These findings highlight the potential of dual-functionalized liposomes as an efficacious delivery system for ApoE2 gene therapy in AD, highlighting a promising strategy to address the disease's underlying mechanisms.

Remodeling of tumour microenvironment: strategies to overcome therapeutic resistance and innovate immunoengineering in triple-negative breast cancer

Triple-negative breast cancer (TNBC) stands as the most complex and daunting subtype of breast cancer affecting women globally. Regrettably, treatment options for TNBC remain limited due to its clinical complexity. However, immunotherapy has emerged as a promising avenue, showing success in developing effective therapies for advanced cases and improving patient outcomes. Improving TNBC treatments involves reducing side effects, minimizing systemic toxicity, and enhancing efficacy. Unlike traditional cancer immunotherapy, engineered nonmaterial's can precisely target TNBC, facilitating immune cell access, improving antigen presentation, and triggering lasting immune responses. Nanocarriers with enhanced sensitivity and specificity, specific cellular absorption, and low toxicity are gaining attention. Nanotechnology-driven immunoengineering strategies focus on targeted delivery systems using multifunctional molecules for precise tracking, diagnosis, and therapy in TNBC. This study delves into TNBC's tumour microenvironment (TME) remodeling, therapeutic resistance, and immunoengineering strategies using nanotechnology.

Identifying Cell-Penetrating Peptides for Effectively Delivering Antimicrobial Molecules into Streptococcus suis

Cell-penetrating peptides (CPPs) are promising carriers to effectively transport antisense oligonucleotides (ASOs), including peptide nucleic acids (PNAs), into bacterial cells to combat multidrug-resistant bacterial infections, demonstrating significant therapeutic potential. Streptococcus suis, a Gram-positive bacterium, is a major bacterial pathogen in pigs and an emerging zoonotic pathogen. In this study, through the combination of super-resolution structured illumination microscopy (SR-SIM), flow cytometry analysis, and toxicity analysis assays, we investigated the suitability of four CPPs for delivering PNAs into S. suis cells: HIV-1 TAT efficiently penetrated S. suis cells with low toxicity against S. suis; (RXR)4XB had high penetration efficiency with inherent toxicity against S. suis; (KFF)3K showed lower penetration efficiency than HIV-1 TAT and (RXR)4XB; K8 failed to penetrate S. suis cells. HIV-1 TAT-conjugated PNA specific for the essential gyrase A subunit gene (TAT-anti-gyrA PNA) effectively inhibited the growth of S. suis. TAT-anti-gyrA PNA exhibited a significant bactericidal effect on serotypes 2, 4, 5, 7, and 9 strains of S. suis, which are known to cause human infections. Our study demonstrates the potential of CPP-ASO conjugates as new antimicrobial compounds for combating S. suis infections. Furthermore, our findings demonstrate that applying SR-SIM and flow cytometry analysis provides a convenient, intuitive, and cost-effective approach to identifying suitable CPPs for delivering cargo molecules into bacterial cells.

A Snake Venom Peptide and Its Derivatives Prevent Aβ42 Aggregation and Eliminate Toxic Aβ42 Aggregates In Vitro

Over a century has passed since Alois Alzheimer first described Alzheimer's disease (AD), and since then, researchers have made significant strides in understanding its pathology. One key feature of AD is the presence of amyloid-β (Aβ) peptides, which form amyloid plaques, and therefore, it is a primary target for treatment studies. Naturally occurring peptides have garnered attention for their potential pharmacological benefits, particularly in the central nervous system. In this study, nine peptide derivatives of Crotamine, a polypeptide from Crotalus durissus terrificus Rattlesnake venom, as well as one d-enantiomer, were evaluated for their ability to modulate Aβ42 aggregation through various assays such as ThT, QIAD, SPR, and sFIDA. All tested peptides were able to decrease Aβ42 aggregation and eliminate Aβ42 aggregates. Additionally, all of the peptides showed an affinity for Aβ42. This study is the first to describe the potential of crotamine derivative peptides against Aβ42 aggregation and to identify a promising d-peptide that could be used as an effective pharmacological tool against AD in the future.

Design and applications of polymer-like peptides in biomedical nanogels

INTRODUCTION

Polymer nanogels are among the most promising nanoplatforms for use in biomedical applications. The substantial interest for these drug carriers is to enhance the transportation of bioactive substances, reduce the side effects, and achieve optimal action on the curative sites by targeting delivery and triggering the release of the drugs in a controlled and continuous mode.

AREA COVERED

The review discusses the opportunities, applications, and challenges of synthetic polypeptide nanogels in biomedicine, with an emphasis on the recent progress in cancer therapy. It is evidenced by the development of polypeptide nanogels for better controlled drug delivery and release, in complex in vivo microenvironments in biomedical applications.

EXPERT OPINION

Polypeptide nanogels can be developed by choosing the amino acids from the peptide structure that are suitable for the type of application. Using a stimulus - sensitive peptide nanogel, it is possible to obtain the appropriate transport and release of the drug, as well as to achieve desirable therapeutic effects, including safety, specificity, and efficiency. The final system represents an innovative way for local and sustained drug delivery at a specific site of the body.

Multibarrier-penetrating drug delivery systems for deep tumor therapy based on synergistic penetration strategy

Nanotherapies, valued for their high efficacy and low toxicity, frequently serve as antitumor treatments, but do not readily penetrate deep into tumor tissues and cells. Here we developed an improved tumor-penetrating peptide (TPP)-based drug delivery system. Briefly, the established TPP iNGR was modified to generate a linear NGR peptide capable of transporting nanotherapeutic drugs into tumors through a CendR pathway-dependent, neuropilin-1 receptor-mediated process. Although TPPs have been reported to reach intended tumor targets, they often fail to penetrate cell membranes to deliver tumoricidal drugs to intracellular targets. We addressed this issue by harnessing cell penetrating peptide technology to develop a liposome-based multibarrier-penetrating delivery system (mbPDS) with improved synergistic drug penetration into deep tumor tissues and cells. The system incorporated doxorubicin-loaded liposomes coated with nona-arginine (R9) CPP and cyclic iNGR (CRNGRGPDC) molecules, yielding Lip-mbPDS. Lip-mbPDS tumor-targeting, tumor cell/tissue-penetrating and antitumor capabilities were assessed using CD13-positive human fibrosarcoma-derived cell (HT1080)-based in vitro and in vivo tumor models. Lip-mbPDS evaluation included three-dimensional layer-by-layer confocal laser scanning microscopy, cell internalization/toxicity assays, three-dimensional tumor spheroid-based penetration assays and antitumor efficacy assays conducted in an animal model. Lip-mbPDS provided enhanced synergistic drug penetration of multiple biointerfaces for potentially deep tumor therapeutic outcomes.

Enabling safer, more potent oligonucleotide therapeutics with bottlebrush polymer conjugates

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

Mucosal absorption of antibody drugs enhanced by cell-penetrating peptides anchored to a platform of polysaccharides

Our previous studies demonstrated that L-octaarginine grafted onto hyaluronic acid via a tetraglycine spacer significantly enhanced intranasal absorption of protein drugs with a molecular weight (Mw) of 22 kDa or less. The present study focused on its potential as an absorption enhancer for antibody drugs with a larger Mw and the enhancement mechanism. When ranibizumab (48 kDa) alone was intranasally administered in mice, its absolute bioavailability was 0.67% on average. The mean bioavailability elevated to 6.2% under coadministration with tetraglycine-L-octaarginine-linked hyaluronic acid. A similar result was observed under substitution of ranibizumab with certolizumab pegol (91 kDa), although bioavailability itself decreased with the Mw increase, irrespective of coadministration with the hyaluronic acid derivative. Rat experiments also revealed that coadministration with the polysaccharide derivative resulted in significant enhancement of intranasal absorption of trastuzumab (148 kDa). In vitro studies using gene-knocked down cells indicated that syndecan-4-induced macropinocytosis played a crucial role on acceleration of antibody uptake into epithelial cells on the nasal mucosa, irrespective of their Mw. It appeared that neither clathrin heavy chain nor caveolin-1 involved in cellular uptake of antibodies. Tetraglycine-L-octaarginine-linked hyaluronic acid was concluded to be a promising delivery tool that possessed universal absorption-enhancing abilities independent to Mw of biologics.