Performance of cell-penetrating peptide-linked polymers physically mixed with poorly membrane-permeable molecules on cell membranes

Validation of the Absorption-Enhancing Ability of Oligoarginines Grafted onto a Backbone of Hyaluronic Acid through Animal Studies from Rodents to Primates

The purpose of our research is to develop functional additives that enhance mucosal absorption of biologics, such as peptide/protein and antibody drugs, to provide their non-to-poor invasive dosage forms self-managed by patients. Our previous in vivo and in vitro studies demonstrated that the intranasal absorption of biologics in mice was significantly improved when coadministered with oligoarginines anchored chemically to hyaluronic acid via a glycine spacer, presumably through syndecan-4-mediated macropinocytosis under activation by oligoarginines. The present mouse experiments first revealed that diglycine-L-tetraarginine-linked hyaluronic acid significantly enhanced the intranasal absorption of sulpiride, which is a poor-absorptive organic compound with a low molecular weight. However, similar enhancement was not observed for levofloxacin, which has a similarly low molecular weight but is a well-absorptive organic compound, probably because its absorption was mostly dominated by passive diffusion. The subsequent monkey experiments revealed that there was no species difference in the absorption-enhancing ability of diglycine-L-tetraarginine-linked hyaluronic acid for not only organic compounds but also biologics. This was presumably because the expression levels of endocytosis-associated membrane proteins on the nasal mucosa in monkeys were almost equivalent to those in mice, and poorly membrane-permeable/membrane-impermeable drugs were mainly absorbed via syndecan-4-mediated macropinocytosis, regardless of animal species. Drug concentrations in the brain assessed in mice and monkeys and those in the cerebral spinal fluids (CSFs) assessed in monkeys indicated that drugs would be delivered from the systemic circulation to the central nervous system by crossing the blood-brain and the blood-CSF barriers under coadministration with the hyaluronic acid derivative. In line with our original hypothesis, this new set of data supported that our oligoarginine-linked hyaluronic acid would locally perform on the mucosal surface and enhance the membrane permeation of drugs under its colocalization.

The Improved Antigen Uptake and Presentation of Dendritic Cells Using Cell-Penetrating D-octaarginine-Linked PNVA-co-AA as a Novel Dendritic Cell-Based Vaccine

Cancer immunotherapy using antigen-pulsed dendritic cells can induce strong cellular immune responses by priming cytotoxic T lymphocytes. In this study, we pulsed tumor cell lysates with VP-R8, a cell-penetrating D-octaarginine-linked co-polymer of N-vinylacetamide and acrylic acid (PNVA-co-AA), into the DC2.4 murine dendritic cell line to improve antigen uptake and then determined the anti-tumor effect in tumor-bearing mice. DC2.4 cells were pulsed with the cell lysate of EL4, a murine lymphoma cell line, and VP-R8 to generate the DC2.4 vaccine. For the in vivo study, DC2.4 cells pulsed with EL4 lysate and VP-R8 were subcutaneously injected into the inguinal lymph node to investigate the anti-tumor effect against EL4 and EL4-specific T cell immune responses. VP-R8 significantly improved antigen uptake into DC2.4 compared to conventional keyhole limpet hemocyanin (p < 0.05). The expression of MHC class I, MHC class II, and CD86 in DC2.4 cells significantly increased after pulsing tumor lysates with VP-R8 compared to other treatments (p < 0.05). The intra-lymph node injection of DC2.4 pulsed with both VP-R8 and EL4 lysate significantly decreased tumor growth compared to DC2.4 pulsed with KLH and lysates (p < 0.05) and induced tumor-infiltrating CD8T cells. The DC2.4 vaccine also remarkably increased the population of IFN-gamma-producing T cells and CTL activity against EL4 cells. In conclusion, we demonstrated that VP-R8 markedly enhances the efficiency of dendritic cell-based vaccines in priming robust anti-tumor immunity, suggesting its potential as a beneficial additive for dendritic cell-based immunotherapy.

A comprehensive review of advanced nasal delivery: Specially insulin and calcitonin

Peptide drugs through nasal mucous membrane, such as insulin and calcitonin have been widely used in the medical field. There are always two sides to a coin. One side, intranasal drug delivery can imitate the secretion pattern in human body, having advantages of physiological structure and convenient use. Another side, the low permeability of nasal mucosa, protease environment and clearance effect of nasal cilia hinder the intranasal absorption of peptide drugs. Researchers have taken multiple means to achieve faster therapeutic concentration, lower management dose, and fewer side effects for better nasal preparations. To improve the peptide drugs absorption, various strategies had been explored via the nasal mucosa route. In this paper, we reviewed the achievements of 18 peptide drugs in the past decade about the perspectives of the efficacy, mechanism of enhancing intranasal absorption and safety. The most studies were insulin and calcitonin. As a result, absorption enhancers, nanoparticles (NPs) and bio-adhesive system are the most widely used. Among them, chitosan (CS), cell penetrating peptides (CPPs), tight junction modulators (TJMs), soft NPs and gel/hydrogel are the most promising strategies. Moreover, two or three strategies can be combined to prepare drug vectors. In addition, spray freeze dried (SFD), self-emulsifying nano-system (SEN), and intelligent glucose reaction drug delivery system are new research directions in the future.

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.

Evaluation of a D-Octaarginine-linked polymer as a transfection tool for transient and stable transgene expression in human and murine cell lines

Poly(N-vinylacetamide-co-acrylic acid) coupled with d-octaarginine (VP-R8) promotes the cellular uptake of peptides/proteins in vitro; however, details of the transfection efficacy of VP-R8, such as the cell types possessing high gene transfer, are not known. Herein, we compared the ability of VP-R8 to induce the cellular uptake of plasmid DNA in mouse and human cell lines from different tissues and organs. A green fluorescent protein (GFP)-expression plasmid was used as model genetic material, and fluorescence as an indicator of uptake and plasmid-derived protein expression. Three mouse and three human cell lines were incubated with a mixture of plasmid and VP-R8, and fluorescence analysis were performed two days after transfection. To confirm stable transgene expression, we performed drug selection three days after transfection. A commercially available polymer-based DNA transfection reagent (PTR) was used as the transfection control and standard for comparing transgene expression efficiency. In the case of transient transgene expression, slight-to-moderate GFP expression was observed in all cell lines transfected with plasmid via VP-R8; however, transfection efficiency was lower using the PTR for gene delivery. In the case of stable transgene expression, VP-R8 promoted drug-resistance acquisition more efficiently than the PTR did. Cells that developed drug resistance after VP-R8‒mediated gene transfection expressed GFP more efficiently than cells that developed drug resistance after transfection with the PTR. Thus, VP-R8 shows potential as an in vitro or ex vivo nonviral transfection tool for generating cell lines with stable transgene expression.

Mechanism on antigen delivery under mucosal vaccination using cell-penetrating peptides immobilized at multiple points on polymeric platforms

We have developed an aggregate of D-octaarginine immobilized at multiple points on a co-polymer of N-vinylacetamide and acrylic acid. Previous studies revealed that immunoglobulin G and A were induced when mice were inoculated with influenza virus antigens under coadministration with the D-octaarginine-immobilized polymers as a mucosal vaccine adjuvant. Infection experiments demonstrated that mice vaccinated with a mixture of inactivated influenza viruses and the polymers were protected from infection with mouse-adapted infectious viruses. In the present study, we investigated the mechanism on antigen delivery under mucosal vaccination using the polymers. Two-hour retention of fluorescein-labeled ovalbumin (F-OVA) on the nasal mucosa was observed when applied with the polymers; nevertheless F-OVA was eliminated less than 10 min under polymer-free conditions. F-OVA mixed with the polymers was vigorously taken up into murine dendritic cells. Electrophoresis and dynamic light scattering analysis indicated that OVA interacted with the polymers. The uptake of F-OVA was hardly ever inhibited by the addition of an excess amount of intact OVA. The results suggested that viral antigens were accumulated on the mucosa and delivered into dendritic cells under basolateral membranes via dendrites extending to the mucosal surface and/or subsequent to their permeation through epithelial cells, when they were coadministered with D-octaarginine-immobilized polymers.

Nasal absorption enhancement of protein drugs independent to their chemical properties in the presence of hyaluronic acid modified with tetraglycine-L-octaarginine

Our previous mouse studies demonstrated that mean bioavailability of exendin-4, which is an injectable glucagon-like peptide-1 (GLP-1) analogue whose molecular weight (Mw) and isoelectric point (pI) are ca. 4.2 kDa and 4.5, respectively, administered nasally with poly(N-vinylacetamide-co-acrylic acid) (PNVA-co-AA) bearing D-octaarginine, which is a typical cell-penetrating peptide, was 20% relative to subcutaneous administration even though it was less than 1% when exendin-4 alone was given nasally. The studies also revealed that the absorption-enhancing ability of D-octaarginine-linked PNVA-co-AA for exendin-4 was statistically equivalent to that of sodium salcaprozate (SNAC), which is an absorption enhancer formulated in tablets of semaglutide approved recently as an orally available GLP-1 analogue. From a perspective of clinical application of our technology, we have separately developed hyaluronic acid modified with L-octaarginine via a tetraglycine spacer which would be degraded in biological conditions. The present study revealed that tetraglycine-L-octaarginine-linked hyaluronic acid enhanced nasal absorption of exendin-4 in mice, as did D-octaarginine-linked PNVA-co-AA. There was no significant difference in absorption-enhancing abilities between the hyaluronic acid derivative and SNAC when octreotide (Mw: ca. 1.0 kDa, pI: 8.3) and lixisenatide (Mw: ca. 4.9 kDa, pI: 9.5) were used as a model protein drug. On the other hand, SNAC did not significantly enhance nasal absorption of somatropin (Mw: ca. 22.1 kDa, pI: 5.3) when compared with absorption enhancer-free conditions. Substitution of SNAC with tetraglycine-L-octaarginine-linked hyaluronic acid resulted in a 5-fold increase in absolute bioavailability of somatropin with statistical significance. It appeared that pI hardly ever influenced absorption-enhancing abilities of both enhancers. Results indicated that our polysaccharide derivative would be a promising absorption enhancer which delivers biologics applied on the nasal mucosa into systemic circulation and was of greater advantage than SNAC for enhancing nasal absorption of protein drugs with a larger Mw.

Optimization of the method for analyzing endocytosis of fluorescently tagged molecules: Impact of incubation in the cell culture medium and cell surface wash with glycine-hydrochloric acid buffer

To obtain the therapeutic effect of biological medicines, such as proteins and nucleic acids, these medicines must achieve their intracellular target, such as the cytoplasm, and pass through biological membrane barriers. Endocytosis is an attractive route for the intracellular delivery of such drugs, and various endocytosis inhibitors have been used as tools to study the involvement of endocytosis in the cell internalization of delivery carriers. However, the specificity of these inhibitors has been insufficiently studied, and our preliminary tests could not detect the expected effect of the well-known endocytosis inhibitors. Therefore, the present study aimed to optimize the experimental conditions to precisely analyze cellular internalization via endocytosis. We first found that incubation of model molecules, such as transferrin (Tf) and cholera toxin subunit B (CTB), in cell culture medium (DMEM) could efficiently induce their internalization to HeLa cells compared to that in transport buffer (HBSS). Moreover, we clarified that cell surface wash with glycine-hydrochloric acid buffer before confocal microscopy and flow cytometry strengthened the intracellular fluorescence of Tf, CTB, and dextran tagged with fluorescent probes possibly via the neutralization of endosomal pH. Even under the optimized condition, however, the specificity of endocytosis inhibitors was disputable. The present study suggested the importance of the optimization of the study design with endocytosis inhibitors in analyzing cellular internalization.

Innovative Mucosal Vaccine Formulations Against Influenza A Virus Infections

Despite efforts made to develop efficient preventive strategies, infections with influenza A viruses (IAV) continue to cause serious clinical and economic problems. Current licensed human vaccines are mainly inactivated whole virus particles or split-virion administered via the parenteral route. These vaccines provide incomplete protection against IAV in high-risk groups and are poorly/not effective against the constant antigenic drift/shift occurring in circulating strains. Advances in mucosal vaccinology and in the understanding of the protective anti-influenza immune mechanisms suggest that intranasal immunization is a promising strategy to fight against IAV. To date, human mucosal anti-influenza vaccines consist of live attenuated strains administered intranasally, which elicit higher local humoral and cellular immune responses than conventional parenteral vaccines. However, because of inconsistent protective efficacy and safety concerns regarding the use of live viral strains, new vaccine candidates are urgently needed. To prime and induce potent and long-lived protective immune responses, mucosal vaccine formulations need to ensure the immunoavailability and the immunostimulating capacity of the vaccine antigen(s) at the mucosal surfaces, while being minimally reactogenic/toxic. The purpose of this review is to compile innovative delivery/adjuvant systems tested for intranasal administration of inactivated influenza vaccines, including micro/nanosized particulate carriers such as lipid-based particles, virus-like particles and polymers associated or not with immunopotentiatory molecules including microorganism-derived toxins, Toll-like receptor ligands and cytokines. The capacity of these vaccines to trigger specific mucosal and systemic humoral and cellular responses against IAV and their (cross)-protective potential are considered.

Biocompatible Polymers Modified with d-Octaarginine as an Absorption Enhancer for Nasal Peptide Delivery

Peptide and protein drugs, which are categorized as biologics, exhibit poor membrane permeability. This pharmacokinetic disadvantage has largely restricted the development of noninvasive dosage forms of biologics that deliver into systemic circulation. We have been investigating the potential use of cell-penetrating peptide-linked polymers as a novel absorption enhancer to overcome this challenge. Since our previous study revealed that biocompatible poly( N-vinylacetamide- co-acrylic acid) modified with d-octaarginine, a typical cell-penetrating peptide, enhanced in vitro permeation of biomolecules such as plasmid DNA and bovine serum albumin through cell membranes, the present study evaluated whether the polymers enhanced in vivo absorption of biologics applied on the mucosa. Mouse experiments demonstrated that d-octaarginine-linked polymers drastically enhanced nasal absorption of exendin-4, whose injection is clinically used. The mean bioavailability was 20% relative to subcutaneous administration, even though it fell short of 1% when exendin-4 alone was administered nasally. The absorption-enhancing function of the polymers was superior to that of sodium caprate and sodium N-(8-(2-hydroxybenzoyl)amino) caprylate, which have been used for humans as an absorption enhancer. In vitro experiments using several biologics with different characteristics revealed that biologics interacted with d-octaarginine-linked polymers and were taken up into cells when incubated with the polymers. The interaction and cellular uptake were enhanced as molecular weights of the biologics increased; however, their charge-dependent in vitro performance was not clearly observed. The current data suggested that biologics formulated with our polymers became an alternative to their conventional invasive parenteral formulations.

Intracellular Delivery of Molecular Cargo Using Cell-Penetrating Peptides and the Combination Strategies

Cell-penetrating peptides (CPPs) can cross cellular membranes in a non-toxic fashion, improving the intracellular delivery of various molecular cargos such as nanoparticles, small molecules and plasmid DNA. Because CPPs provide a safe, efficient, and non-invasive mode of transport for various cargos into cells, they have been developed as vectors for the delivery of genetic and biologic products in recent years. Most common CPPs are positively charged peptides. While delivering negatively charged molecules (e.g., nucleic acids) to target cells, the internalization efficiency of CPPs is reduced and inhibited because the cationic charges on the CPPs are neutralized through the covering of CPPs by cargos on the structure. Even under these circumstances, the CPPs can still be non-covalently complexed with the negatively charged molecules. To address this issue, combination strategies of CPPs with other typical carriers provide a promising and novel delivery system. This review summarizes the latest research work in using CPPs combined with molecular cargos including liposomes, polymers, cationic peptides, nanoparticles, adeno-associated virus (AAV) and calcium for the delivery of genetic products, especially for small interfering RNA (siRNA). This combination strategy remedies the reduced internalization efficiency caused by neutralization.

Potential of D-Octaarginine-Linked Polymers as an in Vitro Transfection Tool for Biomolecules

We have been investigating the potential use of cell-penetrating peptide-linked polymers as a novel penetration enhancer. Since previous in vivo studies demonstrated that poly(N-vinylacetamide-co-acrylic acid) bearing D-octaarginine, a typical cell-penetrating peptide, enhanced membrane permeation of biomolecules, its potential as an in vitro transfection tool was evaluated in this study. A plasmid DNA encoding green fluorescent protein (pGFP-C1), β-galactosidase, and bovine serum albumin (BSA) were used as model biomolecules. Anionic pGFP-C1 interacted electrostatically with cationic d-octaarginine-linked polymers. When the ratio of mass concentration of polymers to that of pGFP-C1 reached 2.5, complexes whose size and zeta potential were approximately 200 nm and 15 mV, respectively, were obtained. GFP expression was observed in cells incubated with complexes prepared under conditions in which the polymer/pDNA concentration ratio exceeded 2.5. The expression level elevated with an increase in the concentration ratio, but physicochemical properties of the complexes remained unchanged. Results suggested that free polymers contributed to pGFP-C1 internalization. Another cell study demonstrated that β-galactosidase premixed with polymers was taken up into cells in its active tetrameric form. Similar electrostatic interaction-driven complex formation was observed for BSA charged negatively in neutral solution. However, it appeared that the internalization processes of BSA differed from those of pGFP-C1. A mass concentration-dependent increase in internalized BSA was observed, irrespective of the polymer/protein concentration ratio. Due to frail interactions, polymers that were released from the complexes and subsequently immobilized on cell membranes might also contribute to membrane permeation of BSA.

Cross-reactivity of immunoglobulin A secreted on the nasal mucosa in mice nasally inoculated with inactivated H1N1 influenza A viruses in the presence of D-octaarginine-linked polymers

We evaluated cross-reactivity of immunoglobulin A (IgA) secreted on the nasal mucosa in mice that were nasally inoculated 4 times with a mixture of inactivated H1N1 influenza A viruses and poly(N-vinylacetamide-co-acrylic acid) (PNVA-co-AA) bearing d-octaarginine at 7-day intervals. Three viral strains (A/Puerto Rico/8/34, A/New Caledonia/20/99 IVR116, and A/Solomon Islands/03/2006) and D-octaarginine-linked polymers with different molecular weights were used as antigens and their carriers, respectively. Secretion of intranasal IgA was barely observed when the inactivated virus alone was administered. The polymer induced the production of intranasal IgA specific to the inoculated viruses, irrespective of the viral strain and molecular weight of the polymer. The respective antibodies cross-reacted to recombinant hemagglutinin proteins of not only the viral strain used for immunization but also other H1N1 strains, including A/Puerto Rico/8/34 strain whose hemagglutinin proteins are diverse from those of other strains. Mice with high reactivity of IgA to the inoculated viruses tended to acquire clear cross-reactivity to other viral strains. Notably, IgA induced by inactivated H1N1 A/New Caledonia/20/99 IVR116 strain with the strongest immunogenicity between 3 antigens in the presence of the polymer cross-reacted to recombinant hemagglutinin proteins of the A/Brisbane/10/2007 and A/Viet Nam/1194/2004 strains, which are categorized into H3N2 and H5N1, respectively. Our polymer is a potential candidate for an efficient antigen carrier that induces mucosal IgA having cross-reactivity to antigenically drifted variants, irrespective of the subtype of viral strains.

Blotting from PhastGel to Membranes by Ultrasound

Ultrasound based approach for enhanced protein blotting is proposed. Three minutes of ultrasound exposure (1 MHz, 2.5 W/cm(2)) was sufficient for a clear transfer of proteins from a polyacrylamide gel (PhastGel) to nitrocellulose or Nylon 66 Biotrans membrane. The proteins evaluated were prestained sodium dodecyl sulfate-polyacrylamide standards (18,500-106,000 Da) and 14C-labeled Rainbow protein molecular weight markers (14,300-200,000 Da).

Cell-penetrating peptide-linked polymers as carriers for mucosal vaccine delivery

We evaluated the potential of poly(N-vinylacetamide-co-acrylic acid) modified with d-octaarginine, which is a typical cell-penetrating peptide, as a carrier for mucosal vaccine delivery. Mice were nasally inoculated four times every seventh day with PBS containing ovalbumin with or without the d-octaarginine-linked polymer. The polymer enhanced the production of ovalbumin-specific immunoglobulin G (IgG) and secreted immunoglobulin A (IgA) in the serum and the nasal cavity, respectively. Ovalbumin internalized into nasal epithelial cells appeared to stimulate IgA production. Ovalbumin transferred to systemic circulation possibly enhanced IgG production. An equivalent dose of the cholera toxin B subunit (CTB), which was used as a positive control, was superior to the polymer in enhancing antibody production; however, dose escalation of the polymer overcame this disadvantage. A similar immunization profile was also observed when ovalbumin was replaced with influenza virus HA vaccines. The polymer induced a vaccine-specific immune response identical to that induced by CTB, irrespective of the antibody type, when its dose was 10 times that of CTB. Our cell-penetrating peptide-linked polymer is a potential candidate for antigen carriers that induce humoral immunity on the mucosal surface and in systemic circulation when nasally coadministered with antigens.