Delivery of myo ‐Inositol Hexakisphosphate to the Cell Nucleus with a Proline‐Based Cell‐Penetrating Peptide

Proline Analogues

Within the canonical repertoire of the amino acid involved in protein biogenesis, proline plays a unique role as an amino acid presenting a modified backbone rather than a side-chain. Chemical structures that mimic proline but introduce changes into its specific molecular features are defined as proline analogues. This review article summarizes the existing chemical, physicochemical, and biochemical knowledge about this peculiar family of structures. We group proline analogues from the following compounds: substituted prolines, unsaturated and fused structures, ring size homologues, heterocyclic, e.g., pseudoproline, and bridged proline-resembling structures. We overview (1) the occurrence of proline analogues in nature and their chemical synthesis, (2) physicochemical properties including ring conformation and cis/trans amide isomerization, (3) use in commercial drugs such as nirmatrelvir recently approved against COVID-19, (4) peptide and protein synthesis involving proline analogues, (5) specific opportunities created in peptide engineering, and (6) cases of protein engineering with the analogues. The review aims to provide a summary to anyone interested in using proline analogues in systems ranging from specific biochemical setups to complex biological systems.

Innovative peptide architectures: advancements in foldamers and stapled peptides for drug discovery

INTRODUCTION

Peptide foldamers play a critical role in pharmaceutical research and biomedical applications. This review highlights recent (post-2020) advancements in novel foldamers, synthetic techniques, and their applications in pharmaceutical research.

AREAS COVERED

The authors summarize the structures and applications of peptide foldamers such as α, β, γ-peptides, hydrocarbon-stapled peptides, urea-type foldamers, sulfonic-γ-amino acid foldamers, aromatic foldamers, and peptoids, which tackle the challenges of traditional peptide drugs. Regarding antimicrobial use, foldamers have shown progress in their potential against drug-resistant bacteria. In drug development, peptide foldamers have been used as drug delivery systems (DDS) and protein-protein interaction (PPI) inhibitors.

EXPERT OPINION

These structures exhibit resistance to enzymatic degradation, are promising for therapeutic delivery, and disrupt crucial PPIs associated with diseases such as cancer with specificity, versatility, and stability, which are useful therapeutic properties. However, the complexity and cost of their synthesis, along with the necessity for thorough safety and efficacy assessments, necessitate extensive research and cross-sector collaboration. Advances in synthesis methods, computational modeling, and targeted delivery systems are essential for fully realizing the therapeutic potential of foldamers and integrating them into mainstream medical treatments.

Boronic Acid-Linked Cell-Penetrating Peptide for Protein Delivery

Studying functional protein delivery into live cells is important, ranging from fundamental research to therapeutics. Cell-penetrating peptides (CPPs) are known to deliver proteins with applauded efficacy and have gained importance for applications in protein therapeutics and exploration of versatile cellular mechanisms. The primary aim of the work is to design a CPP as a tool and delivery vehicle for macromolecules, including proteins. In this work, boronic acid-linked cyclic deca arginine (cR10) is reported as an efficient CPP that exhibited 3-fold higher delivery of chemically synthesized ubiquitin (Ub) than pristine cR10-linked Ub, examined with live U2OS cells. As a futuristic plan, an artificial intelligence machine learning-based rationale has been designed and proposed.

Drug delivery using biocompatible covalent organic frameworks (COFs) towards a therapeutic approach

Covalent organic frameworks (COFs) are constructed exclusively with lightweight organic scaffolds, which can have a 2D or 3D architecture. The ease of synthesis, robust skeleton and tunable properties of COFs make them superior candidates among their counterparts for a wide range of uses including biomedical applications. In the biomedical field, drug delivery or photodynamic-photothermal (PDT-PTT) therapy can be individually considered a potential parameter to be investigated. Therefore, this comprehensive review is focused on drug delivery using COFs, highlighting the encapsulation and decapsulation of drugs by COF scaffolds and their delivery in biological media including live cells. Versatile COF scaffolds together with the delivery of several drug molecules are considered. We attempted to incorporate the status of drug encapsulation and decapsulation considering a wide range of recent publications.

Catalytic templated length-controlled oligomerization

Templated synthesis is an intriguing strategy for the length-controlled synthesis of oligomers. Traditionally, such reactions require stoichiometric amounts of the template with respect to the product. Recently we reported catalytic macrocyclic templates that promote oligomerization of a small molecule substrate with a remarkable degree of length control. Herein we present our efforts toward creating linear templates for catalytic length-controlled oligomer synthesis.

"Intercellular Mass Transport" Mimic Enables ASO Entry Completely into the Cell Nucleus for Enhanced Ischemia Therapy

Currently, the development of a new therapeutic technology is focused on antisense oligonucleotides (ASOs), where ASOs are used to complementarily pair with DNA, messenger RNA, or long noncoding RNA (lncRNA) to regulate the cell behavior by inhibiting the target gene expression. However, the targeted regulation toward nuclear genes still faces great challenges in ASO delivery for clinical applications, i.e., two essential criteria (high nuclear entry and delivery vehicle safety/simplification) generally compromise each other and are not simultaneously satisfactory. Herein, for the first time, inspired by "intercellular-mass-transport", we report an important discovery that the cell membrane of endothelial cells (ECs) serving as the biointerface enables ASOs to rapidly and completely enter the EC nucleus. Thereby, we innovatively fabricate a nanosystem only by sequential self-assembly of natural/off-the-shelf biomaterials to well overcome the above-mentioned contradiction. The efficacy is strikingly superior to that of the previous delivery vehicles. Furthermore, our technology is applied to successfully silence lncRNA MEG3 in the EC nucleus, significantly augmenting EC morphogenesis. More importantly, this nanosystem is applicable for in vivo intramuscular injection to enhance the therapeutic outcome in a critical limb ischemia mouse model. This work brings a new hope for the technological innovation of ASO nuclear delivery and opens a new avenue to explore natural/off-the-shelf materials for cargo delivery into subcellular compartments.

Interrogation on the Cellular Nano-Interface and Biosafety of Repeated Nano-Electroporation by Nanostraw System

Cell perforation is a critical step for intracellular drug delivery and real-time biosensing of intracellular signals. In recent years, the nanostraws system has been developed to achieve intracellular drug delivery with minimal invasiveness to the cells. Repeated cell perforation via nano-system could allow delivery of multiple drugs into cells for cell editing, but the biosafety is rarely explored. In this work, a nanostraw-mediated nano-electroporation system was developed, which allowed repeated perforation of the same set of cells in a minimally invasive manner, while the biosafety aspect of this system was investigated. Highly controllable fabrication of Al₂O₃ nanostraw arrays based on a porous polyethylene terephthalate (PET) membrane was integrated with a microfluidic device to construct the nanostraw-electroporation system. The pulse conditions and intervals of nano-electroporation were systematically optimized to achieve efficient cells perforation and maintain the viability of the cells. The cells proliferation, the early apoptosis activities after nanostraw-electroporation and the changes of gene functions and gene pathways of cells after repeated nano-electroporation were comprehensively analyzed. These results revealed that the repeated nanostraw-electroporation did not induce obvious negative effects on the cells. This work demonstrates the feasibility of repeated nano-electroporation on cells and provides a promising strategy for future biomedical applications.

Combination of epigenetic regulation with gene therapy-mediated immune checkpoint blockade induces anti-tumour effects and immune response in vivo

Immunotherapy has become a powerful cancer treatment, but only a small fraction of patients have achieved durable benefits due to the immune escape mechanism. In this study, epigenetic regulation is combined with gene therapy-mediated immune checkpoint blockade to relieve this immune escape mechanism. PPD (i.e., mPEG-b-PLG/PEI-RT3/DNA) is developed to mediate plasmid-encoding shPD-L1 delivery by introducing multiple interactions (i.e., electrostatic, hydrogen bonding, and hydrophobic interactions) and polyproline II (PPII)-helix conformation, which downregulates PD-L1 expression on tumour cells to relieve the immunosuppression of T cells. Zebularine (abbreviated as Zeb), a DNA methyltransferase inhibitor (DNMTi), is used for the epigenetic regulation of the tumour immune microenvironment, thus inducing DC maturation and MHC I molecule expression to enhance antigen presentation. PPD plus Zeb combination therapy initiates a systemic anti-tumour immune response and effectively prevents tumour relapse and metastasis by generating durable immune memory. This strategy provides a scheme for tumour treatment and the inhibition of relapse and metastasis.

A self-sustained nanoplatform reverses TRAIL-resistance of pancreatic cancer through coactivating of exogenous and endogenous apoptotic pathway

Since the 5-year survival rate of pancreatic cancer is only 10.0%, new therapies are urgently needed. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis specifically on tumor cells, nevertheless its clinical application was seriously restricted by resistance and short in vivo half-life. Herein, a novel multifunctional R6ST protein equipped with cell penetrating peptides R6, intrinsic apoptosis inducing tetrapeptide AVPI and soluble TRAIL was designed and constructed. Then, it was recruited to prepare self-sustained nanoplatform (SSN) to reverse TRAIL-resistance of pancreatic cancer through simultaneously promoting extrinsic and intrinsic apoptotic pathway, as well to elongate circulation time. Once administrated, high tumor accumulation and cellular uptake of SSN were achieved through prolonged circulation time, targeting ability of soluble TRAIL to death receptors and positive-charged R6, and further enhanced through reversed upregulation of death receptors on TRAIL-resistant tumor cells by the cumulated artesunate released in cytoplasm as a positive feedback loop. Furthermore, this loop simultaneously promoted extrinsic apoptosis of TRAIL fragment via the upregulated death receptors on TRAIL-resistant pancreatic cancer cells and intrinsic apoptosis of AVPI tetrapeptide via the efficient accumulation and uptake of R6ST on SSN. Hence, SSN exhibited synergistic antitumor effect and provided a new strategy for TRAIL-resistant pancreatic cancer therapy.

Mimicking Biological Recognition: Lessons in Binding Hydrophilic Guests in Water

Selective molecular recognition of hydrophilic guests in water plays a fundamental role in a vast number of biological processes, but synthetic mimicry of biomolecular recognition in water still proves challenging both in terms of achieving comparable affinities and selectivities. This Review highlights strategies that have been developed in the field of supramolecular chemistry to selectively and non-covalently bind three classes of biologically relevant molecules: nucleotides, carbohydrates, and amino acids. As several groups have systematically modified receptors for a specific guest, an evolutionary perspective is also provided in some cases. Trends in the most effective binding forces for each class are described, providing insight into selectivity and potential directions for future work.