Delivery Of Therapeutic Peptides Research Articles

Multi-site esterification: a tunable, reversible strategy to tailor therapeutic peptides for delivery.

Peptides are naturally potent and selective therapeutics with massive potential; however, low cell membrane permeability limits their clinical implementation, particularly for hydrophilic, anionic peptides with intracellular targets. To overcome this limitation, esterification of anionic carboxylic acids on therapeutic peptides can simultaneously increase hydrophobicity and net charge to facilitate cell internalization, whereafter installed esters can be cleaved hydrolytically to restore activity. To date, however, most esterified therapeutics contain either a single esterification site or multiple esters randomly incorporated on multiple sites. This investigation provides molecular engineering insight into how the number and position of esters installed onto the therapeutic peptide α carboxyl terminus 11 (αCT11, RPRPDDLEI) with 4 esterification sites affect hydrophobicity and the hydrolysis process that reverts the peptide to its original form. After installing methyl esters onto αCT11 using Fischer esterification, we isolated 5 distinct products and used 2D nuclear magnetic resonance spectroscopy, reverse-phase high performance liquid chromatography, and mass spectrometry to determine which residues were esterified in each and the resulting increase in hydrophobicity. We found esterifying the C-terminal isoleucine to impart the largest increase in hydrophobicity. Monitoring ester hydrolysis showed the C-terminal isoleucine ester to be the most hydrolytically stable, followed by the glutamic acid, whereas esters on aspartic acids hydrolyze rapidly. LC-MS revealed the formation of transient intramolecular aspartimides prior to hydrolysis to carboxylic acids. In vitro proof-of-concept experiments showed esterifying αCT11 to increase cell migration into a scratch, highlighting the potential of multi-site esterification as a tunable, reversible strategy to enable the delivery of therapeutic peptides.

Oral delivery of therapeutic peptides by milk-derived extracellular vesicles

Oral delivery of therapeutic peptides by milk-derived extracellular vesicles

Nanotechnology Enabled Advances in Oral Delivery of Therapeutic Peptides: Mechanistic Insights for Translation to Clinic

Abstract: Peptides represent a rapidly expanding class of novel treatments with distinct pharmacokinetic properties when compared to macromolecular proteins or small-molecule medications. Peptides are polymers with a molecular mass of less than 10 kDa. Protein-protein interactions have been the primary goal of oral delivery of peptide drugs for the last two decades. Recent trends suggest the possibility of mechanistically targeting challenging binding interfaces with the right binding affinity and specificity for molecules like peptides that bring conformational flexibility. Over 80 peptide medications have received regulatory approval to treat a range of conditions, from human immunodeficiency infection caused by viruses to fatal diseases like cancer. This review covers the need for peptide delivery via the oral route and offers insights to overcome the challenges. For successful translation to the clinic, oral delivery of therapeutic peptides coupled with nano formulation strategies has gained increased attention in recent years. The role of permeation boosters, and digestive enzyme inhibitors to overcome major hurdles such as degradation in the gastrointestinal tract and low intestinal permeability are presented here. Alteration of physicochemical characteristics of peptide molecules, the addition of functional excipients to specifically designed drug delivery systems, nanoformulation approaches, amongst other recent methodologies, to increase the oral bioavailability of peptide medications, are also presented herein. Numerous peptide candidates, both approved and under clinical trials, are included in this review.

Inhibition of the Naja naja venom toxicity by polymeric nanoparticles loaded with Leucas aspera methanolic extract.

Snakebite is a neglected tropical disease that affects millions of people worldwide. Developing effective treatments can make a significant contribution to global health efforts and public health initiatives. To reduce mortality due to snakebite, there is an immediate need to explore novel and effective treatment methodologies. In that context, nanoparticle-based drug delivery is gaining a lot of attention. Hydrophilic nanoparticles are suitable for the delivery of therapeutic peptides, proteins, and antigens. The present investigation is aimed at evaluating the anti-ophidian potential of the methanolic extract of the ethno-medicinal herb Leucas aspera (Willd.) loaded within chitosan nanoparticles (CNP-LA), against the Indian cobra (Naja naja) venom enzymes. For this purpose, nanoparticles were prepared using the ionic gelation method to enhance the efficacy of the extract. The physicochemical and structural features of nanoparticles were investigated using dynamic light scattering (DLS), Fourier-transform Infrared (FTIR), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD) techniques. It was found that CNP-LA has an average size of 260nm with a polydispersity index of 0.132 (PDI) and zeta potential of 34.7 mV, with an encapsulation efficiency of 92.46%. The in vitro release study was performed at pH 5.0 and 7.4. Furthermore, in vitro studies indicated that CNP-LA inhibited the phospholipase A2, hemolytic, and caseinolytic activities of Naja naja venom with the percentage inhibition of 92.5%, 83.9%, and 94.5%, respectively. This is the first report on the application of herbal methanolic extract loaded within chitosan nanoparticles for neutralizing snake venom enzymes with increased efficiency.

Cold Exposure and Oral Delivery of GLP-1R Agonists by an Engineered Probiotic Yeast Strain Have Antiobesity Effects in Mice.

Advanced microbiome therapeutics (AMTs) holds promise in utilizing engineered microbes such as bacteria or yeasts for innovative therapeutic applications, including the in situ delivery of therapeutic peptides. Glucagon-like peptide-1 receptor agonists, such as Exendin-4, have emerged as potential treatments for type 2 diabetes and obesity. However, current administration methods face challenges with patient adherence and low oral bioavailability. To address these limitations, researchers are exploring improved oral delivery methods for Exendin-4, including utilizing AMTs. This study engineered the probiotic yeast Saccharomyces boulardii to produce Exendin-4 (Sb-Exe4) in the gastrointestinal tract of male C57BL/6 mice to combat diet-induced obesity. The biological efficiency of Exendin-4 secreted by S. boulardii was analyzed ex vivo on isolated pancreatic islets, demonstrating induced insulin secretion. The in vivo characterization of Sb-Exe4 revealed that when combined with cold exposure (8 °C), the Sb-Exe4 yeast strain successfully suppressed appetite by 25% and promoted a 4-fold higher weight loss. This proof of concept highlights the potential of AMTs to genetically modify S. boulardii for delivering active therapeutic peptides in a precise and targeted manner. Although challenges in efficacy and regulatory approval persist, AMTs may provide a transformative platform for personalized medicine. Further research in AMTs, particularly focusing on probiotic yeasts such as S. boulardii, holds great potential for novel therapeutic possibilities and enhancing treatment outcomes in diverse metabolic disorders.

αB-Crystallin Peptide Fused with Elastin-like Polypeptide: Intracellular Activity in Retinal Pigment Epithelial Cells Challenged with Oxidative Stress.

Oxidative stress-induced retinal degeneration is among the main contributing factors of serious ocular pathologies that can lead to irreversible blindness. αB-crystallin (cry) is an abundant component of the visual pathway in the vitreous humor, which modulates protein and cellular homeostasis. Within this protein exists a 20 amino acid fragment (mini-cry) with both chaperone and antiapoptotic activity. This study fuses this mini-cry peptide to two temperature-sensitive elastin-like polypeptides (ELP) with the goal of prolonging its activity in the retina. The biophysical properties and chaperone activity of cry-ELPs were confirmed by mass spectrometry, cloud-point determination, and dynamic light scattering 'DLS'. For the first time, this work compares a simpler ELP architecture, cry-V96, with a previously reported ELP diblock copolymer, cry-SI. Their relative mechanisms of cellular uptake and antiapoptotic potential were tested using retinal pigment epithelial cells (ARPE-19). Oxidative stress was induced with H2O2 and comparative internalization of both cry-ELPs was made using 2D and 3D culture models. We also explored the role of lysosomal membrane permeabilization by confocal microscopy. The results indicated successful ELP fusion, cellular association with both 2D and 3D cultures, which were enhanced by oxidative stress. Both constructs suppressed apoptotic signaling (cleaved caspase-3); however, cry-V96 exhibited greater lysosomal escape. ELP architecture is a critical factor to optimize delivery of therapeutic peptides, such as the anti-apoptotic mini-cry peptide; furthermore, the protection of mini-cry via ELPs is enhanced by lysosomal membrane permeabilization.

A Bioresponsive Genetically Encoded Antimicrobial Crystal for the Oral Treatment of Helicobacter Pylori Infection.

Helicobacter pylori (H. pylori) causes infection in the stomach and is a major factor for gastric carcinogenesis. The application of antimicrobial peptides (AMPs) as an alternative treatment to traditional antibiotics is limited by their facile degradation in the stomach, their poor penetration of the gastric mucosa, and the cost of peptide production. Here, the design and characterization of a genetically encoded H. pylori-responsive microbicidal protein crystal Cry3Aa-MIIA-AMP-P17 is described. This designed crystal exhibits preferential binding to H. pylori, and when activated, promotes the targeted release of the AMP at the H. pylori infection site. Significantly, when the activated Cry3Aa-MIIA-AMP-P17 crystals are orally delivered to infected mice, the Cry3Aa crystal framework protects its cargo AMP against degradation, resulting in enhanced in vivo efficacy against H. pylori infection. Notably, in contrast to antibiotics, treatment with the activated crystals results in minimal perturbation of the mouse gut microbiota. These results demonstrate that engineered Cry3Aa crystals can serve as an effective platform for the oral delivery of therapeutic peptides to treat gastrointestinal diseases.

Recent Progress in the Oral Delivery of Therapeutic Peptides and Proteins: Overview of Pharmaceutical Strategies to Overcome Absorption Hurdles.

Proteins and peptides have secured a place as excellent therapeutic moieties on account of their high selectivity and efficacy. However due to oral absorption limitations, current formulations are mostly delivered parenterally. Oral delivery of peptides and proteins (PPs) can be considered the need of the hour due to the immense benefits of this route. This review aims to critically examine and summarize the innovations and mechanisms involved in oral delivery of peptide and protein drugs. Comprehensive literature search was undertaken, spanning the early development to the current state of the art, using online search tools (PubMed, Google Scholar, ScienceDirect and Scopus). Research in oral delivery of proteins and peptides has a rich history and the development of biologics has encouraged additional research effort in recent decades. Enzyme hydrolysis and inadequate permeation into intestinal mucosa are the major causes that result in limited oral absorption of biologics. Pharmaceutical and technological strategies including use of absorption enhancers, enzyme inhibition, chemical modification (PEGylation, pro-drug approach, peptidomimetics, glycosylation), particulate delivery (polymeric nanoparticles, liposomes, micelles, microspheres), site-specific delivery in the gastrointestinal tract (GIT), membrane transporters, novel approaches (self-nanoemulsifying drug delivery systems, Eligen technology, Peptelligence, self-assembling bubble carrier approach, luminal unfolding microneedle injector, microneedles) and lymphatic targeting, are discussed. Limitations of these strategies and possible innovations for improving oral bioavailability of protein and peptide drugs are discussed. This review underlines the application of oral route for peptide and protein delivery, which can direct the formulation scientist for better exploitation of this route.

Recent Advances in Formulations for Long-Acting Delivery of Therapeutic Peptides.

Recent preclinical and clinical studies have focused on the active area of therapeutic peptides due to their high potency, selectivity, and specificity in treating a broad range of diseases. However, therapeutic peptides suffer from multiple disadvantages, such as limited oral bioavailability, short half-life, rapid clearance from the body, and susceptibility to physiological conditions (e.g., acidic pH and enzymolysis). Therefore, high peptide dosages and dose frequencies are required for effective patient treatment. Recent innovations in pharmaceutical formulations have substantially improved therapeutic peptide administration by providing the following advantages: long-acting delivery, precise dose administration, retention of biological activity, and improvement of patient compliance. This review discusses therapeutic peptides and challenges in their delivery and explores recent peptide delivery formulations, including micro/nanoparticles (based on lipids, polymers, porous silicon, silica, and stimuli-responsive materials), (stimuli-responsive) hydrogels, particle/hydrogel composites, and (natural or synthetic) scaffolds. This review further covers the applications of these formulations for prolonged delivery and sustained release of therapeutic peptides and their impact on peptide bioactivity, loading efficiency, and (in vitro/in vivo) release parameters.

Dual-responsive bioconjugates bearing a bifunctional adaptor for robust cytosolic peptide delivery.

Peptide drugs have been successfully used for the treatment of various diseases. However, it is still challenging to develop therapeutic peptides working on intracellular targets due to their poor membrane permeability. Here, we proposed a type of dual-responsive bioconjugates bearing a heterobifunctional adaptor containing both aldehyde and catechol moieties for efficient cytosolic peptide delivery. Hydrazine-terminated cargo peptides were tagged to a boronated dendrimer with the help of the adaptor via dynamic acylhydrazone and catechol‑boronate linkages. The bioconjugates efficiently delivered peptides with distinct physicochemical properties into various cells, and could release the cargo peptides triggered by intracellular reactive oxygen species and endolysosomal acidity, restoring the biofunctions of delivered peptides. In addition, the designed complexes efficiently delivered a pro-apoptotic peptide into osteosarcoma cancer cells and successfully inhibited the tumor growth both in vitro and in vivo. This study provides a universal and efficient platform for cytosolic therapeutic peptide delivery to intracellular targets for treating various diseases.

Virus-like silica nanoparticles enhance macromolecule permeation in vivo.

Nanoparticle based permeation enhancers have the potential to improve the oral delivery of biologics. Recently, solid silica nanoparticles were discovered to improve the intestinal permeability of peptides and proteins via transient opening of the gut epithelium. In this study, we have developed small-sized (∼60 nm) virus-like silica nanoparticles (VSNP) as a reversible and next generation non-toxic permeation enhancer for oral delivery of biologics. Our results show that the anionic VSNP showed a better permeation-enhancing effect than the same sized spherical Stöber silica nanoparticles (∼60 nm) by enhancing the apparent insulin permeability by 1.3-fold in the Caco-2 monolayer model and by 1.2-fold in the Caco-2/MTX-HT-29 co-culture model. In vivo experiments in healthy mice demonstrated that anionic VSNP significantly enhanced the permeation of fluorescently labelled 4 kDa dextran after oral administration compared to Stöber nanoparticles and positively charged VSNP. The results indicated that the nanoscale surface roughness is an important consideration when designing nanoparticle-based permeation enhancers. Overall, our study shows for the first time that small-sized (∼60 nm) VSNP with nanoscale surface roughness can be used as a non-toxic permeation enhancer for oral delivery of therapeutic peptides and proteins.

A comparison of electrosprayed vs vortexed glycosaminoglycan-peptide nanoparticle platform for protection and improved delivery of therapeutic peptides

Therapeutic peptides capable of reducing inflammation via inhibition of the MAP kinase 2 pathway have the potential to reduce inflammation in atopic dermatitis by suppressing secretion of inflammatory cytokines by resident keratinocytes. One of the biggest hurdles to the use of therapeutic peptides, however, is their rapid degradation by intrinsic proteases and peptidases found in serum. Here we introduce a new nanoparticle technology that enhances and extends the bioactivity of a MAP KAP kinase 2 inhibitor peptide (MK2i) via electrostatic complexation with Dermatan sulfate (DS), a glycosaminoglycan, and explore their properties under various conditions. DS-MK2i nanoparticles can be made using electrospray ionization or sonication and vortexing with no stabilizing polymers or crosslinking. Average particle diameter, polydispersity index, and zeta potential were measured over a pH range of 2.5–11.5, in increments of 0.5, in water and at physiological ionic strength. Both particle types were shown to be shelf stable, robust, and behave differently in response to pH. They are also significantly more effective at suppressing cytokine secretion in inflamed, human keratinocytes than peptide alone in the presence of serum, providing a facile method of protecting peptides for therapeutic delivery in conditions such as atopic dermatitis, and abrogating the need for serum-starvation in in vitro testing.

Targeting enteric release of therapeutic peptides by encapsulation in complex coacervated matrix microparticles by spray drying

Oral delivery of therapeutic peptides faces substantial barriers, as peptides can be susceptible to denaturation, aggregation or hydrolysis in the stomach. This study explored the possibility to target enteric release of five model peptides, semaglutide, liraglutide, GLP-1, gonadorelin acetate and oxytocin acetate, by encapsulation in a novel, industrially scalable complex coacervation by spray drying process (CoCo process). The potential of the complex coacervated (CoCo) matrix to prevent release of peptides in water, and simulated gastric fluid at pH 1.8 (SGF), while fully releasing in simulated intestinal fluid at pH 7.4 (SIF) was examined. The CoCo matrix consisting of gelatin, alginate and succinic acid was marginally effective at preventing peptide release in SGF; however, incorporating latex with the CoCo formulation substantially limited release of semaglutide, liraglutide and GLP-1. From CoCo powders formulated with 0.25:1 ethylcellulose:alginates + gelatin, 12.3 ± 0.7% of semaglutide, 24.0 ± 0.5% of liraglutide, and 41.2 ± 0.7% of GLP-1 released in SGF after 2h incubation, reductions of 201–311% over CoCo powders without ethylcellulose. Alternate latexes including methacrylic acid copolymer and polyvinyl acetate phthalate, similarly decreased peptide release in the SGF. Notably, while successful control of semaglutide, liraglutide and GLP-1 release was achieved, encapsulation in CoCo powders with or without latex failed to limit the release of gonadorelin acetate or oxytocin acetate in SGF. The physicochemical properties of the peptides including size, net charge and hydrophobicity likely play a role in the extent to which peptides remain within the microcapsules in the aqueous suspensions. All peptides fully released in SIF as the complex coacervated matrix dissolves at the higher pH. Latex in the CoCo formulation had negligible impact on peptide release in the SIF. This study demonstrates the potential for formulation strategies to target enteric release of therapeutic peptides from complex coacervated powders formed by spray drying.

Integrin‐Enriched Membrane Nanocarrier for the Specific Delivery of RGD‐modified Relaxin Analog to Inhibit Pancreatic Cancer Liver Metastasis through Reversing Hepatic Stellate Cell Activation

AbstractLiver metastasis is common in patients with pancreatic cancer (PC) and is the leading cause of death associated with PC. Liver fibrosis induced by activated hepatic stellate cells (HSCs) creates a favorable metastatic microenvironment that promotes metastasis growth. B7‐33, a therapeutic peptide (relaxin analog) that targets relaxin family peptide receptors on activated HSCs, inhibits the pSMAD2/3 signaling pathway and weakens the fibrogenic properties of activated HSCs. However, the short half‐life and highly conserved nature of the B7‐33 sequence limit its application in vivo. Here, B7‐33 is modified with the cRGD sequence, which does not affect the efficacy of B7‐33 and allows B7‐33 to assemble into vascular endothelial cell membrane‐derived vesicles by specifically interacting with integrin αvβ3. These rationally designed vesicles (B7‐33‐HNPs) are able to prolong the half‐life of B7‐33 in vivo and accumulate in the liver to reverse HSCs activation. Moreover, B7‐33‐HNPs prevent the formation and growth of liver metastases in a mouse model of metastatic PC. This study proposes a feasible strategy for building a therapeutic peptide delivery system through specific interactions, serving as a reference for preventing liver metastasis of PC through the regulation of HSCs.

Nose-to-Brain Delivery of Therapeutic Peptides as Nasal Aerosols.

Central nervous system (CNS) disorders, such as psychiatric disorders, neurodegeneration, chronic pain, stroke, brain tumor, spinal cord injury, and many other CNS diseases, would hugely benefit from specific and potent peptide pharmaceuticals and their low inherent toxicity. The delivery of peptides to the brain is challenging due to their low metabolic stability, which decreases their duration of action, poor penetration of the blood-brain barrier (BBB), and their incompatibility with oral administration, typically resulting in the need for parenteral administration. These challenges limit peptides’ clinical application and explain the interest in alternative routes of peptide administration, particularly nose-to-brain (N-to-B) delivery, which allows protein and peptide drugs to reach the brain noninvasively. N-to-B delivery can be a convenient method for rapidly targeting the CNS, bypassing the BBB, and minimizing systemic exposure; the olfactory and trigeminal nerves provide a unique pathway to the brain and the external environment. This review highlights the intranasal delivery of drugs, focusing on peptide delivery, illustrating various clinical applications, nasal delivery devices, and the scope and limitations of this approach.

Identification of a Multi-Component Formulation for Intestinal Delivery of a GLP-1/Glucagon Co-agonist Peptide.

Oral delivery of therapeutic peptides has been challenging due to multiple physiological factors and physicochemical properties of peptides. We report a systematic approach to identify formulation compositions combining a permeation enhancer and a peptidase inhibitor that minimize proteolytic degradation and increase absorption of a peptide across the small intestine. An acylated glucagon-like peptide-1/glucagon co-agonist peptide (4.5kDa) was selected as a model peptide. Proteolytic stability of the peptide was investigated in rat and pig SIF. Effective PEs and multiple component formulations were identified in rats. Relative bioavailability of the peptide was determined in minipigs via intraduodenal administration (ID) of enteric capsules. The peptide degraded rapidly in the rat and pig SIF. Citric acid, SBTI, and SBTCI inhibited the enzymatic degradation. The peptide self-associated into trimers in solution, however, addition of PEs monomerized the peptide. C10 was the most effective PE among tested PEs (DPC, LC, rhamnolipid, C12-maltosides, and SNAC) to improve intestinal absorption of the peptide in the rat IJ-closed loop model. A combination of C10 and SBTI or SBTCI increased the peptide exposure 5-tenfold compared to the exposure with the PE alone in the rat IJ-cannulated model, and achieved1.06 ± 0.76% bioavailability in minipigs relative to subcutaneous via ID administration using enteric capsules. We identified SBTI and C10 as an effective peptidase inhibitor and PE for intestinal absorption of the peptide. The combination of SBTI and C10 addressed the peptide physiochemical properties and provides a formulation strategy to achieve intestinal delivery of this peptide.

A nucleus-targeting peptide antagonist towards EZH2 displays therapeutic efficacy for lung cancer

EZH2 is an overexpressed nuclear protein associated with relatively poor survival and chemoresistance in lung cancer. In this study, a nucleus-targeting peptide antagonist EIP103 capable of penetrating cell membrane and nuclear envelope was identified, and has high binding affinity towards EZH2 localized in the nucleus of lung cancer cells. To improve the stability and therapeutic efficacy of EIP103, PEG-PE micelle encapsulated EIP103 (M−EIP103) was successfully conducted. In vitro results indicated that M−EIP103 exhibited better stability, higher intracellular uptake and stronger cytotoxicity than free EIP103 in H446 and A549 cells. Mechanistic studies suggested that M−EIP103 inhibited proliferation by down-regulating the H3K27me3 expression level in cancer cells. In vivo assays further confirmed that both EIP103 and M−EIP103 significantly inhibited lung cancer progression. Notably, enhanced therapeutic efficacy of EIP103 by PEG-PE micelle encapsulation could be identified. The observed anti-tumor activity of EIP103 and M−EIP103 demonstrated a promising therapy to improve clinical treatment of lung cancers as well as other EZH2-overexpressing malignant cancers. This study also illustrates the feasibility of developing targeted delivery of therapeutic peptides to nucleus for cancer therapy.

Construction and Evaluation of Chitosan-Based Nanoparticles for Oral Administration of Exenatide in Type 2 Diabetic Rats.

Oral delivery of therapeutic peptides has been a daunting challenge due to poor transport across the tight junctions and susceptibility to enzymatic degradation in the gastrointestinal tract. Numerous advancement in nanomedicine has been made for the effective delivery of protein and peptide. Owing to the superior performance of chitosan in opening intercellular tight junctions of epithelium and excellent mucoadhesive properties, chitosan-based nanocarriers have recently garnered considerable attention, which was formulated in this paper to orally deliver the GLP-1 drug (Exenatide). Against this backdrop, we used chitosan (CS) polymers to encapsulate the exenatide, sodium tripolyphosphate (TPP) as the cross-linking agent and coated the exterior with sodium alginate (ALG) to impart the stability in an acidic environment. The chitosan/alginate nanoparticles (CS-TPP-ALG) functioned as a protective exenatide carrier, realized efficient cellular uptake and controlled release, leading to a steady hypoglycemic effect and a good oral bioavailability in vivo. Trimethyl chitosan (TMC), a chitosan derivative with stronger positive electrical properties was additionally selected as a substitute for chitosan to construct the TMC-TPP-ALG nanoparticle, and its oral peptide delivery capacity was explored in terms of both characterization and pharmacodynamics studies. Overall, our study demonstrated that functional chitosan/alginate nanoparticles can protect proteins from enzymatic degradation and enhance oral absorption, which presents important research value and application prospects.

In vitro and in vivo evaluation of 3D printed sodium alginate/polyethylene glycol scaffolds for sublingual delivery of insulin: Preparation, characterization, and pharmacokinetics

Delivery of therapeutic peptides via sublingual administration is extremely desired and 3D printed scaffolds are potential candidates as carriers to enhance insulin delivery. 3D printed sublingual sodium alginate (SA)/polyethylene glycol (PEG) composite scaffolds were produced for enhancing insulin delivery by examining the chemical, morphological, mechanical, thermal, cytotoxic, and pharmacokinetic features. The tensile strength and flexibility of scaffolds increased after loading insulin due to the crystalline structure of insulin. Furthermore, insulin-loaded 9SA/3PEG scaffolds showed ultrafast wetting (<1 s), disintegration (<6 s), and also dissolution (<30 s) according to Hixson-Crowell kinetic model. The cell viability of L929 cells on 3D printed scaffolds was examined and these scaffolds could be safely applied on animals. Pharmacokinetic parameters and blood glucose level were evaluated following sublingual administration of scaffolds to type-1 diabetic rats. A single dose of scaffold presented a longer hypoglycemic effect, reducing ~60% of glycemia after 30 min and it lasted for 12 h by increasing the bioavailability of insulin. Scaffolds indicated a sustained profile for serum insulin levels, which continued to increase slightly after 3 h during the study. The polymeric scaffold with a high safety and efficacy holds a new promising delivery strategy for administering injectable insulin through the sublingual route.

Characterization of the membrane penetration-enhancing peptide S19 derived from human syncytin-1 for the intracellular delivery of TAT-fused proteins

Although cell-penetrating peptides such as the HIV-derived TAT peptide have been used as tools for the intracellular delivery of therapeutic peptides and proteins, a problem persists: the endosomal escape efficiency is low. Previously, we found that the fusogenic peptide S19, derived from the human protein syncytin-1, enhance the endosomal escape efficiency of proteins that incorporated by endocytosis via TAT. In this study, we first performed Ala-scanning mutagenesis of S19, and found that all Ile, Val, Leu and Phe with high β-sheet forming propensities in S19 are important for the intracellular uptake of S19-TAT-fused proteins. In a secondary structure analysis of the mutated S19-TAT peptides in the presence of liposomes mimicking late endosomes (LEs), the CD spectra of V3A and I4A mutants with low uptake activity showed the appearance of an α-helix structure, whereas the mutant G5A retained both the uptake activity and the β-structure. In addition, we investigated the appropriate linking position and order of the S19 and TAT peptides to a cargo protein including an apoptosis-induced peptide and found that both the previous C-terminal S19-TAT tag and the N-terminal TAT-S19 tag promote the cytoplasmic delivery of the fusion protein. These results and previous results suggest that the interaction of TAT with the LE membrane causes a structural change in S19 from a random coil to a β-strand and that the subsequent parallel β-sheet formation between two S19 peptides may promote adjacent TAT dimerization, resulting in endosomal escape from the LE membrane.