d-Polyarginine Lipopeptides as Intestinal Permeation Enhancers

Sequence optimization of lipid-modified amphiphilic tetrapeptides as anticancer drug carriers

In this study, 19 tetrapeptides, each consisting of four amino acid residues, were designed and modified with oleic acid to serve as amphiphilic dispersants for anticancer drug delivery. The lipid-modified peptides (Ole-pep) were evaluated for their ability to disperse paclitaxel (Ptx), a poorly water-soluble anticancer drug. The water dispersibility of Ptx was significantly increased when peptides with two or more positively or negatively charged functional groups were used as dispersants. One specific Ole-pep demonstrated a critical micelle concentration of 0.0682 × 10-3 mol/dm3, confirming its excellent amphiphilic properties and capacity to encapsulate Ptx. Cytotoxicity studies in HeLa cells, a cell line derived from human cervical cancer cells, confirmed that the complexes with Ptx were highly cytotoxic regardless of the peptide used. Additionally, the results suggested that certain peptides, particularly those with a high number of Lys residues, exhibited cytotoxicity on their own.

Modular Design of Lipopeptide-Based Organ-Specific Targeting (POST) Lipid Nanoparticles for Highly Efficient RNA Delivery

Lipid nanoparticles (LNPs) with highly efficient and specific extrahepatic targeting abilities are promising in gene delivery, and the lipopeptides (LPs) with excellent designability and functionality are expected to empower the construction of functional LNPs. This study aims to develop highly efficient ionizable components that accurately match different targeting lipid systems through the modular design of LPs. Based on this, a lipopeptide-based organ-specific targeting (POST) LNP screening strategy is constructed, in which lysine-histidine-based lipopeptides (KH-LPs) are designed as highly efficient ionizable components. The optimal KH-LP LNP screened in vitro shows excellent siRNA/mRNA transfecting ability in various hard-to-transfect cell lines. Compared to the classic LNPs, the POST LNPs screened in vivo achieve even higher (or at least comparable) efficiency and specificity in delivering mRNA and siRNA to the lung, liver, and spleen, respectively. The structure-activity relationship (SAR) proves that the modular regulation of LP structures can accurately provide the optimal ionizable components for different targeting lipid systems, demonstrating the potential of this strategy in developing efficient and selective targeting systems, which is expected to open up more possibilities for gene therapy.

Neo-Glycolipid Oximes as Intestinal Permeation Enhancers for Peptide Hormone PYY3-36

Herein, we describe the design and synthesis of 16 neo-glycolipids that are potential permeation enhancers for oral drug delivery of peptide therapeutics. These amphiphilic neo-glycolipids are composed of fatty acids and various carbohydrates (d-glucose, lactose, cellobiose, maltose) via an oxime linker. The ability of the synthesized neo-glycolipids to enhance permeation of fluorescein-labelled dextran (4 kDa) or 3H-mannitol across intestinal epithelium was investigated in vitro using monolayers of human epithelial Caco-2 cells. Their effects were compared with (pre-)clinically known enhancers as reference compounds; sodium salts of octanoic, decanoic, and dodecanoic acid, and sodium salcaprozate (SNAC). Most neo-glycolipids increased the permeation of the model compounds, proving that neo-glycolipids, which possess vastly different properties from the reference compounds, e. g., in terms of clogD and polar surface area, are effective permeation enhancers. The neo-glycolipid based on decanoic acid and glucose was more potent than related compounds based on disaccharides. Significant differences in solubility and cellular compatibility were found for neo-glyolipids based on different carbohydrates. Finally, neo-glycolipids were evaluated as permeation enhancers for the peptide hormone PYY3-36. Glucose- and maltose-derived neo-glycolipids based on decanoic and dodecanoic acid showed promising enhancements in PYY3-36 permeation in vitro while maintaining good cellular compatibility, relevant for oral delivery of obesity treatments.

Exploring the potential of human intestinal organoids: Applications, challenges, and future directions

The complex and dynamic environment of the gastrointestinal tract shapes one of the fastest renewing tissues in the human body, the intestinal epithelium. Considering the lack of human preclinical studies, reliable models that mimic the intestinal environment are increasingly explored. Patient-derived intestinal organoids are powerful tools that recapitulate in vitro many pathophysiological features of the human intestine. In this review, the possible applications of human intestinal organoids in different research fields are highlighted. From physiologically relevant to intestinal disease modeling, regenerative medicine, and toxicology studies, the potential of intestinal organoids will be here presented and discussed. Despite the remarkable opportunities offered, limitations related to ethical concerns, tissue collection, reproducibility, and methodologies may hinder the full exploitation of this cell-based model into high throughput studies and clinical practice. Currently, distinct approaches can be used to overcome the numerous challenges found along the way and to allow the full implementation of this ground-breaking technology.

Medium-Chain Triacylglycerols (MCTs) and Their Fractions in Drug Delivery Systems : A Systematic Review

Medium-chain triacylglycerol (MCT) is a type of triacylglycerol that has six or seven to twelve carbon chains. It consists of three molecules of fatty acids attached to one molecule of glycerol. Drug delivery system (DDS) is defined as a formulation to distribute drugs into the human body. The unique properties of MCTs have garnered interest in using them as excipients in DDS. Even though there are many significant effects attributed to the use of MCTs, especially in modulating the rate of drug delivery in various DDS, they are all limited and intermittent. This warrants a detailed summary of the previous studies on the use of MCTs in various DDS. Therefore, this review focuses on presenting a systematic review of previous studies on the use of MCTs in the last six years and explores the types and effects of MCTs on DDS that employ various types of delivery routes. A systematic search through PubMed, Science Direct and Scopus was performed. Keywords like "medium-chain triglycerides", "medium-chain fatty acids", "medium-chain triglycerides and their fractions", "medium-chain fatty acids and their fractions", "MCTs", "MCFA", "in drug delivery", "in drug delivery system" and their combinations were used. The synonyms of the words were also used to extend the search. A total of 17 articles that met the inclusion criteria were identified. Findings from this review have identified the several MCTs and their fractions used in DDS that employed the oral/enteral, topical, transdermal, parenteral, and pulmonary routes of drug delivery. The review also highlights that the usage of MCTs in DDS results in a better transportation of drugs into the human body.

Topoisomeric Membrane-Active Peptides: A Review of the Last Two Decades

In recent decades, bioactive peptides have been gaining recognition in various biomedical areas, such as intracellular drug delivery (cell-penetrating peptides, CPPs) or anti-infective action (antimicrobial peptides, AMPs), closely associated to their distinct mode of interaction with biological membranes. Exploiting the interaction of membrane-active peptides with diverse targets (healthy, tumoral, bacterial or parasitic cell membranes) is opening encouraging prospects for peptides in therapeutics. However, ordinary peptides formed by L-amino acids are easily decomposed by proteases in biological fluids. One way to sidestep this limitation is to use topoisomers, namely versions of the peptide made up of D-amino acids in either canonic (enantio) or inverted (retroenantio) sequence. Rearranging peptide sequences in this fashion provides a certain degree of native structure mimicry that, in appropriate contexts, may deliver desirable biological activity while avoiding protease degradation. In this review, we will focus on recent accounts of membrane-active topoisomeric peptides with therapeutic applications as CPP drug delivery vectors, or as antimicrobial and anticancer candidates. We will also discuss the most common modes of interaction of these peptides with their membrane targets.

Barriers to the Intestinal Absorption of Four Insulin-Loaded Arginine-Rich Nanoparticles in Human and Rat

Peptide drugs and biologics provide opportunities for treatments of many diseases. However, due to their poor stability and permeability in the gastrointestinal tract, the oral bioavailability of peptide drugs is negligible. Nanoparticle formulations have been proposed to circumvent these hurdles, but systemic exposure of orally administered peptide drugs has remained elusive. In this study, we investigated the absorption mechanisms of four insulin-loaded arginine-rich nanoparticles displaying differing composition and surface characteristics, developed within the pan-European consortium TRANS-INT. The transport mechanisms and major barriers to nanoparticle permeability were investigated in freshly isolated human jejunal tissue. Cytokine release profiles and standard toxicity markers indicated that the nanoparticles were nontoxic. Three out of four nanoparticles displayed pronounced binding to the mucus layer and did not reach the epithelium. One nanoparticle composed of a mucus inert shell and cell-penetrating octarginine (ENCP), showed significant uptake by the intestinal epithelium corresponding to 28 ± 9% of the administered nanoparticle dose, as determined by super-resolution microscopy. Only a small fraction of nanoparticles taken up by epithelia went on to be transcytosed via a dynamin-dependent process. In situ studies in intact rat jejunal loops confirmed the results from human tissue regarding mucus binding, epithelial uptake, and negligible insulin bioavailability. In conclusion, while none of the four arginine-rich nanoparticles supported systemic insulin delivery, ENCP displayed a consistently high uptake along the intestinal villi. It is proposed that ENCP should be further investigated for local delivery of therapeutics to the intestinal mucosa.

NIR and glutathione trigger the surface release of methotrexate linked by Diels-Alder adducts to anisotropic gold nanoparticles

The administration and controlled release of drugs over time remains one of the greatest challenges of science today. In the nanomaterials field, anisotropic gold nanoparticles (AuNPs) with plasmon bands centered at the near-infrared region (NIR), such as gold nanorods (AuNRs) and gold nanoprisms (AuNPrs), under laser irradiation, locally increase the temperature, allowing the release of drugs. In this sense, temporally controlled drug delivery could be promoted by external stimuli using thermo-reversible chemical reactions, such as Diels-Alder cycloadditions from a diene and a dienophile fragment (compound a). In this study, an antitumor drug (methotrexate, MTX) was linked to plasmonic AuNPs by a Diels-Alder adduct (compound c), which after NIR suffers a retro-Diels-Alder reaction, producing release of the drug (compound b). We obtained two nanosystems based on AuNRs and AuNPrs. Both nanoconstructs were coated with BSA-r₈ (Bovine Serum Albumin functionalized with Arg₈, all-D octa arginine) in order to increase the colloidal stability and promote internalization of the nanosystems on HeLa and SK-BR-3 cells. In addition, the presence of BSA allows protecting the cargo from being released on the extracellular environment and promotes the photothermal release of the drug in the presence of glutathione (GSH). The nanosystems' drug release profile was evaluated after NIR irradiation in the presence and absence of glutathione (GSH), showing a considerable increase of drug release when NIR light and glutathione were combined. This work broadens the range of possibilities of using two complementary strategies for the controlled release of an antitumor drug from AuNRs and AuNPrs: the photothermal cleavage of a thermolabile adduct controlled by an external stimulus (laser irradiation), complemented with the use of the intracellular metabolite GSH.

A Versatile Human Intestinal Organoid-Derived Epithelial Monolayer Model for the Study of Enteric Pathogens

Gastrointestinal infections cause significant morbidity and mortality worldwide. The complexity of human biology and limited insights into host-specific infection mechanisms are key barriers to current therapeutic development. Here, we demonstrate that two-dimensional epithelial monolayers derived from human intestinal organoids, combined with in vivo-like bacterial culturing conditions, provide significant advancements for the study of enteropathogens. Monolayers from the terminal ileum, cecum, and ascending colon recapitulated the composition of the gastrointestinal epithelium, in which several techniques were used to detect the presence of enterocytes, mucus-producing goblet cells, and other cell types following differentiation. Importantly, the addition of receptor activator of nuclear factor kappa-B ligand (RANKL) increased the presence of M cells, critical antigen-sampling cells often exploited by enteric pathogens. For infections, bacteria were grown under in vivo-like conditions known to induce virulence. Overall, interesting patterns of tissue tropism and clinical manifestations were observed. Shigella flexneri adhered efficiently to the cecum and colon; however, invasion in the colon was best following RANKL treatment. Both Salmonella enterica serovars Typhi and Typhimurium displayed different infection patterns, with S. Typhimurium causing more destruction of the terminal ileum and S. Typhi infecting the cecum more efficiently than the ileum, particularly with regard to adherence. Finally, various pathovars of Escherichia coli validated the model by confirming only adherence was observed with these strains. This work demonstrates that the combination of human-derived tissue with targeted bacterial growth conditions enables powerful analyses of human-specific infections that could lead to important insights into pathogenesis and accelerate future vaccine development. IMPORTANCE While traditional laboratory techniques and animal models have provided valuable knowledge in discerning virulence mechanisms of enteric pathogens, the complexity of the human gastrointestinal tract has hindered our understanding of physiologically relevant, human-specific interactions; and thus, has significantly delayed successful vaccine development. The human intestinal organoid-derived epithelial monolayer (HIODEM) model closely recapitulates the diverse cell populations of the intestine, allowing for the study of human-specific infections. Differentiation conditions permit the expansion of various cell populations, including M cells that are vital to immune recognition and the establishment of infection by some bacteria. We provide details of reproducible culture methods and infection conditions for the analyses of Shigella, Salmonella, and pathogenic Escherichia coli in which tissue tropism and pathogen-specific infection patterns were detected. This system will be vital for future studies that explore infection conditions, health status, or epigenetic differences and will serve as a novel screening platform for therapeutic development.

Oligoarginine Peptide Conjugated to BSA Improves Cell Penetration of Gold Nanorods and Nanoprisms for Biomedical Applications

Gold nanoparticles (AuNPs) have been shown to be outstanding tools for drug delivery and biomedical applications, mainly owing to their colloidal stability, surface chemistry, and photothermal properties. The biocompatibility and stability of nanoparticles can be improved by capping the nanoparticles with endogenous proteins, such as albumin. Notably, protein coating of nanoparticles can interfere with and decrease their cell penetration. Therefore, in the present study, we functionalized albumin with the r₈ peptide (All-D, octaarginine) and used it for coating NIR-plasmonic anisotropic gold nanoparticles. Gold nanoprisms (AuNPrs) and gold nanorods (AuNRs) were coated with bovine serum albumin (BSA) previously functionalized using a cell penetrating peptide (CPP) with the r₈ sequence (BSA-r₈). The effect of the coated and r₈-functionalized AuNPs on HeLa cell viability was assessed by the MTS assay, showing a low effect on cell viability after BSA coating. Moreover, the internalization of the nanostructures into HeLa cells was assessed by confocal microscopy and transmission electron microscopy (TEM). As a result, both nanoconstructs showed an improved internalization level after being capped with BSA-r₈, in contrast to the BSA-functionalized control, suggesting the predominant role of CPP functionalization in cell internalization. Thus, our results validate both novel nanoconstructs as potential candidates to be coated by endogenous proteins and functionalized with a CPP to optimize cell internalization. In a further approach, coating AuNPs with CPP-functionalized BSA can broaden the possibilities for biomedical applications by combining their optical properties, biocompatibility, and cell-penetration abilities.