Pharmaceutical and immunological evaluation of mucoadhesive nanoparticles based delivery system(s) administered intranasally

Nanoparticle formulation for the development of a dog nanovaccine against Cystic Echinococcosis

Cystic Echinococcosis is a cosmopolitan zoonosis closely linked to poverty and ignorance. It affects both cattle and humans, causing significant losses to both human and animal health. To date, there is no effective way to combat this. Our proposal focused on the formulation of poly (lactic-co-glycolic acid (PLGA) and Eudragit-RSPO polymeric nanoparticles, which are suitable to encapsulate an antigen for oral administration in dogs. This antigen, named EgFABP1, belonging to the family of fatty acid-binding proteins, was isolated from the larval form of the parasite Echinococcus granulosus. Several reports point to proteins from this family from parasitic flatworms as candidates for a successful vaccine, considering the restricted lipid metabolism of these organisms. The encapsulation of the antigen yielded an efficiency higher than 50 %, and the nanoparticles showed the expected size range. In addition, antigen integrity was conserved and the formulation was resistant to artificial gastric and intestinal fluid effects.

Regeneration of olfactory neuroepithelium in 3-methylindole-induced anosmic rats treated with intranasal chitosan

Olfactory dysfunction significantly impairs the life quality of patients but without effective treatments to date. The previous report has demonstrated that chitosan mediates the differentiation of olfactory receptor neurons (ORNs) through insulin-like growth factors and insulin-like growth factor binding protein-2 axis in an in vitro model. However, whether chitosan can further treat olfactory dysfunction in vivo remains unexplored. This study aims to evaluate the therapeutic effect of chitosan on a 3-methylindole-induced anosmic rat model. Intraperitoneal injection of 3-methylindole is performed to induce anosmia in rats. Experimental results demonstrate that the food-finding duration after chitosan treatment gradually decrease to around 80 s, and both the olfactory neuroepithelium (ON) thickness and mature ORNs (expressing olfactory marker protein) are significantly restored. Furthermore, proliferating cells (expressing bromodeoxyuridine) are mainly co-expressed with immature ORNs (expressing βIII tubulin) below the intermediate layer of the ON in the chitosan-treated group on day 28 following 3-methylindole treatment. Conversely, proliferating cells are scattered over the ON, and co-localized with immature ORNs and sustentacular cells (expressing keratin 18) in the sham group, and even immature ORNs go into apoptosis (expressing DNA fragmentation and cleaved caspase-3), possibly causing incomplete regeneration. Consequently, chitosan regenerates the ON by regulating olfactory neural homeostasis and reducing ORN apoptosis, and serves as a potential therapeutic intervention for olfactory dysfunction in the future.

The Application of Mucoadhesive Chitosan Nanoparticles in Nasal Drug Delivery

Mucosal delivery of antigens can induce both humoral and cellular immune responses. Particularly, the nasal cavity is a strongly inductive site for mucosal immunity among several administration routes, as it is generally the first point of contact for inhaled antigens. However, the delivery of antigens to the nasal cavity has some disadvantages such as rapid clearance and disposition of inhaled materials. For these reasons, remarkable efforts have been made to develop antigen delivery systems which suit the nasal route. The use of nanoparticles as delivery vehicles enables protection of the antigen from degradation and sustains the release of the loaded antigen, eventually resulting in improved vaccine and/or drug efficacy. Chitosan, which exhibits low toxicity, biodegradability, good cost performance, and strong mucoadhesive properties, is a useful material for nanoparticles. The present review provides an overview of the mucosal immune response induced by nanoparticles, recent advances in the use of nanoparticles, and nasal delivery systems with chitosan nanoparticles.

Intranasal delivery of interferon-β-loaded nanoparticles induces control of neuroinflammation in a preclinical model of multiple sclerosis: A promising simple, effective, non-invasive, and low-cost therapy

Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system (CNS). Interferon (IFN)-β constitutes one of the first-line therapies to treat MS, but has limited efficacy due to the injectable systemic administration, short half-life, and limited CNS access. To address these limitations, we developed IFN-β-loaded chitosan/sulfobutylether-β-cyclodextrin nanoparticles (IFN-β-NPs) for delivery of IFN-β into the CNS via the intranasal (i.n.) route. The nanoparticles (NPs) (≈200 nm, polydispersity ≈0.1, and zeta potential ≈20 mV) were prepared by mixing two aqueous solutions and associated human or murine IFN-β with high efficiency (90%). Functional in vitro assays showed that IFN-β-NPs were safe and that IFN-β was steadily released while retaining biological activity. Biodistribution analysis showed an early and high fluorescence in the brain after nasal administration of fluorescent probe-loaded NPs. Remarkably, mice developing experimental autoimmune encephalomyelitis (EAE), an experimental model of MS, exhibited a significant improvement of clinical symptoms in response to intranasal IFN-β-NPs (inIFN-β-NPs), whereas a similar dose of intranasal or systemic free IFN-β had no effect. Importantly, inIFN-β-NPs treatment was equally effective despite a reduction of 78% in the total amount of weekly administered IFN-β. Spinal cords obtained from inIFN-β-NPs-treated EAE mice showed fewer inflammatory foci and demyelination, lower expression of antigen-presenting and costimulatory proteins on CD11b⁺ cells, and lower astrocyte and microglia activation than control mice. Therefore, IFN-β treatment at tested doses was effective in promoting clinical recovery and control of neuroinflammation in EAE only when associated with NPs. Overall, inIFN-β-NPs represent a potential, effective, non-invasive, and low-cost therapy for MS.

Use of PELC/CpG Adjuvant for Intranasal Immunization with Recombinant Hemagglutinin to Develop H7N9 Mucosal Vaccine

Human infections with H7N9 avian influenza A virus can result in severe diseases with high mortality. Developing an effective vaccine is urgently needed to prevent its pandemic potential. Vaccine delivery routes via mucosal surfaces are known to elicit mucosal immune responses such as secretory IgA antibodies in mucosal fluids, thus providing first-line protection at infection sites. PEG-b-PLACL (PELC) is a squalene-based oil-in-water emulsion adjuvant system that can enhance antigen penetration and uptake in nasal mucosal layers with enhanced mucin interactions. In this study, intranasal immunizations with recombinant H7 (rH7) proteins with a PELC/CpG adjuvant, as compared to the use of poly (I:C) or bacterial flagellin adjuvant, elicited higher titers of H7-specific IgG, IgA, hemagglutination inhibition, and neutralizing antibodies in sera, and increased numbers of H7-specific IgG- and IgA-antibody secreting cells in the spleen. Both PELC/CpG and poly (I:C) adjuvants at a dose as low as 5 μg HA provided an 80% survival rate against live virus challenges, but a lower degree of PELC/CpG-induced Th17 responses was observed. Therefore, the mucosal delivery of rH7 proteins formulated in a PELC/CpG adjuvant can be used for H7N9 mucosal vaccine development.

Regulation of chitosan-mediated differentiation of human olfactory receptor neurons by insulin-like growth factor binding protein-2

Olfaction is normally taken for granted in our lives, not only assisting us to escape from dangers, but also increasing our quality of life. Although olfactory neuroepithelium (ON) can reconstitute its olfactory receptor neurons (ORNs) after injury, no adequate treatment for olfactory loss has yet emerged. The present study investigates the role of glycosaminoglycans (GAGs) in modulating olfactory neuronal homeostasis and elucidates the regulatory mechanism. This work isolates and cultures human olfactory neuroepithelial cells (HONCs) with various GAGs for 7 days, and find that chitosan promotes ORN maturation, expressing olfactory marker protein (OMP) and its functional components. Growth factor protein array, ELISA and western blot analysis reveal that insulin-like growth factor binding protein 2 (IGFBP2) shows a higher level in chitosan-treated HONCs than in controls. Biological activity of insulin-like growth factor-1 (IGF-1), IGF-2 and IGF-1 receptor (IGF1R) is further investigated. Experimental results indicate that IGF-1 and IGF-2 enhance the growth of immature ORNs, expressing βIII tubulin, but decrease mature ORNs. Instead, down-regulation of phosphorylated IGF1R lifts the OMP expression, and lowers the βIII tubulin expression, by incubation with the phosphorylated inhibitor of IGF1R, OSI-906. Finally, the effect of chitosan on ORN maturity is antagonized by concurrently adding IGFBP2 protease, matrix metallopeptidase-1. Overall, our data demonstrate that chitosan promotes ORN differentiation by raising the level of IGFBP2 to sequestrate the IGFs-IGF1R signaling. STATEMENT OF SIGNIFICANCE: Olfactory dysfunction serves as a crucial alarm in neurodegenerative diseases, and one of its causes is lacking of sufficient mature olfactory receptor neurons to detect odorants in the air. However, the clinical treatment for olfactory dysfunction is still controversial. Chitosan is the natural linear polysaccharide and exists in rat olfactory neuroepithelium. Previously, chitosan has been demonstrated to mediate the differentiation of olfactory receptor neurons in an in vitro rat model, but the mechanism is unknown. The study aims to evaluate the role and mechanism of chitosan in an in vitro human olfactory neurons model. Overall, these results reveal that chitosan is a potential agent for treating olfactory disorder by the maintenance of olfactory neural homeostasis. This is the first report to demonstrate that chitosan promotes differentiation of olfactory receptor neurons through increasing IGFBP2 to sequestrate the IGFs-IGF1R.

A lipidic delivery system of a triple vaccine adjuvant enhances mucosal immunity following nasal administration in mice

We previously developed an highly efficacious combination adjuvant comprised of innate defense regulator (IDR)-1002 peptide, poly(I:C) and polyphosphazene (TriAdj). Here we aimed to design and test the in vivo efficacy of a mucoadhesive nasal formulation of this adjuvant. To determine the physical properties of the formulation, the effect of addition of each individual component was characterised by gel electrophoresis and fluorescence quenching using rhodamine-poly(I:C). Cationic liposomes comprised of didodecyl dimethylammonium bromide (DDAB), dioleoyl phosphatidylethanolamine (DOPE) (50:50 or 75:25 mol:mol) and DDAB, L-α-phosphatidylcholine (egg PC) and DOPE (40:50:10 mol:mol:mol) were prepared by the thin-film extrusion method. The liposomes and TriAdj were combined by simple mixing. The formed complex (L-TriAdj) was characterized by dynamic light scattering, zeta potential, and mucin interactions. We found that IDR-1002 peptide, polyphosphazene and poly(I:C) self-assembled in solution forming an anionic complex. Exposure of RAW267.4 mouse macrophage cells to TriAdj alone vs. L-TriAdj indicated that DDAB/DOPE (50:50) and DDAB/EPC/cholesterol (40:50:10) complexation reduced TriAdj toxicity. Next, TriAdj-containing cationic liposomes were prepared at several molar ratios to determine optimal size, stability and desired positive charge. Transmission electron microscopy showed rearrangement of lipid structures on binding of liposomes to TriAdj and to mucin. Stable particles (<200 nm over 24 h) showed mucin binding of DDAB/DOPE + TriAdj was greater than DDAB/EPC/DOPE + TriAdj. To verify in vivo efficacy, mice were administered the DDAB/DOPE + TriAdj complex intranasally with ovalbumin as the antigen, and the immunogenic response was measured by ELISA (serum IgG1, IgG2a, IgA) and ELISpot assays (splenocyte IL-5, IFN-γ). Mice administered adjuvant showed a significantly greater immune response with L-TriAdj than TriAdj alone, with a dose-response proportionate to the triple adjuvant content, and an overall balanced Th1/Th2 immune response representing both systemic and mucosal immunity.

Characterization of immunogenicity of avian influenza antigens encapsulated in PLGA nanoparticles following mucosal and subcutaneous delivery in chickens

Mucosal vaccine delivery systems have paramount importance for the induction of mucosal antibody responses. Two studies were conducted to evaluate immunogenicity of inactivated AIV antigens encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). In the first study, seven groups of specific pathogen free (SPF) layer-type chickens were immunized subcutaneously at 7-days of age with different vaccine formulations followed by booster vaccinations two weeks later. Immune responses were profiled by measuring antibody (Ab) responses in sera and lachrymal secretions of vaccinated chickens. The results indicated that inactivated AIV and CpG ODN co-encapsulated in PLGA NPs (2x NanoAI+CpG) produced higher amounts of hemagglutination inhibiting antibodies compared to a group vaccinated with non-adjuvanted AIV encapsulated in PLGA NPs (NanoAI). The tested adjuvanted NPs-based vaccine (2x NanoAI+CpG) resulted in higher IgG responses in the sera and lachrymal secretions at weeks 3, 4 and 5 post-vaccination when immunized subcutaneously. The incorporation of CpG ODN led to an increase in Ab-mediated responses and was found useful to be included both in the prime and booster vaccinations. In the second study, the ability of chitosan and mannan coated PLGA NPs that encapsulated AIV and CpG ODN was evaluated for inducing antibody responses when delivered via nasal and ocular routes in one-week-old SPF layer-type chickens. These PLGA NPs-based and surface modified formulations induced robust AIV-specific antibody responses in sera and lachrymal secretions. Chitosan coated PLGA NPs resulted in the production of large quantities of lachrymal IgA and IgG compared to mannan coated NPs, which also induced detectable amounts of IgA in addition to the induction of IgG in lachrymal secretions. In both mucosal and subcutaneous vaccination approaches, although NPs delivery enhanced Ab-mediated immunity, one booster vaccination was required to generate significant amount of Abs. These results highlight the potential of NPs-based AIV antigens for promoting the induction of both systemic and mucosal immune responses against respiratory pathogens.

Preparation, characterization and in vivo evaluation of alginate-coated chitosan and trimethylchitosan nanoparticles loaded with PR8 influenza virus for nasal immunization

For efficient mucosal vaccine delivery, nanoparticulate antigens are better taken by microfold cells in the nasal associated lymphoid tissue and also dendritic cells. Nanoparticles based on polymers such as chitosan (CHT) and its water soluble derivative, trimethylchitosan (TMC), could be successfully used as carrier/adjuvant for this purpose. Sodium alginate, a negatively charged biopolymer, could modify the immunostimulatory properties of CHT and TMC NPs and increase their stability. Sodium alginate (ALG)-coated chitosan (CHT) and trimethylchitosan (TMC) nanoparticles (NPs) loaded with inactivated PR8 influenza virus were successfully prepared by direct coating of the virus with CHT or TMC polymers to evaluate their immunoadjuvant potential after nasal immunization. After nasal immunizations in BALB/c mice, PR8-CHT formulation elicited higher IgG2a and IgG1 antibody titers compared with PR8-TMC. ALG coating of this formulation (PR8-CHT-ALG) significantly decreased the antibody titers and a less immune response was induced than PR8-TMC-ALG formulation. PR8-TMC-ALG formulation showed significantly higher IgG2a/IgG1 ratio, as criteria for Th1-type immune response, compared with PR8-CHT-ALG and PR8 virus alone. Altogether, the PR8-TMC-ALG formulation could be considered as an efficient intranasal antigen delivery system for nasal vaccines.

EDIII-DENV3 nanospheres drive immature dendritic cells into a mature phenotype in an in vitro model

Domain III of E protein of dengue virus (DENV) is a target for vaccine development. Unfortunately, this protein based platform has low general immunogenicity. To circumvent this problem, the use of an adjuvant-nanoparticle delivery system to facilitate immunogenicity of soluble DENV-EDIII protein was investigated. One of the key features of this delivery system is its ability to simultaneously deliver antigens and exert adjuvanticity on specialized immune cells. In this study, N-trimethyl chitosan (TMC) nanoparticles (NPs) were generated to be used as adjuvant and carrier for soluble E-domain III of dengue virus serotype 3 (sEDIII-D3). Using ionotropic gelation, purified sEDIII-D3 was encapsulated into TMC NPs to form EDIII-D3 TMC NPs. After optimization, EDIII-D3 TMC particles exhibited a loading efficiency of 81% and a loading capacity of 41%. The immunogenicity of EDIII-D3 TMC NPs was tested using monocyte-derived dendritic cells (MoDCs). It was found that EDIII-D3 TMC NPs were well taken up by MoDCs. In addition, EDIII-D3 TMC NP treated MoDCs significantly upregulated maturation markers (CD80, CD83, CD86 and HLA-DR) and induced secretion of various cytokines and chemokines (IFN-α, IL-1β, IL-6, IL-2, IL-12p70, IFN-γ, IL-4, IL-10, IL-8, MCP-1, macrophage inflammatory protein-1β, granulocyte-colony stimulating factor, granulocyte-macrophage colony-stimulating factor and IL-7). These results indicate that EDIII-D3 TMC NPs are potent immunogens, at least in vitro, with the ability to induce maturation of DCs and highlight the potential use of TMC NPs for enhancing immunogenicity of a non-replicating dengue vaccine.

Nasal vaccination with poly(β-amino ester)-poly(d,l-lactide-co-glycolide) hybrid nanoparticles

Mucosal vaccination stimulates both mucosal and systemic immunity. However, mucosal applications of vaccine antigens in their free form generally result in poor systemic immune responses and need adjuvantation. In this study, bovine serum albumin loaded, new hybridised poly(β-amino ester)-poly(d,l-lactide-co-glycolide) nanoparticles were prepared by double emulsion-solvent evaporation method, characterised and evaluated in vivo as nasal vaccine carriers. Cationic spherical particles with a mean size of 240nm, good physical stability and high encapsulation efficiency were obtained. Protein structure was not affected throughout preparation and minimal toxicity was shown in Calu-3 and A549 cells. Nasal vaccination with these nanoparticles revealed markedly higher humoral immune responses compared with free antigen following intranasal and subcutaneous immunisation. Mucosal immune response was also stimulated and cytokine titres indicated that Th1 and Th2 pathways were successfully activated. This study shows that the formulated hybrid nanoparticles can be a promising carrier for nasal immunisation of poor antigenic proteins.

Immunization against HTLV-I with chitosan and tri-methylchitosan nanoparticles loaded with recombinant env23 and env13 antigens of envelope protein gp46

To prevent the spread of HTLV-I (Human T-lymphotropic virus type 1), a safe and effective vaccine is required. To increase immune responses against the peptide antigens can be potentiated with polymer-based nanoparticles, like chitosan (CHT) and trimethylchitosan (TMC), as delivery system/adjuvant. CHT and TMC nanoparticles loaded with recombinant proteins (env23 & env13) of gp46 were prepared by direct coating of antigens with positively charged polymers. The size of CHT and TMC nanoparticles (NPs) loaded with each antigen was about 400 nm. The physical stability of NPs was followed for 4 weeks. Both formulations showed to be stable for about 15 days. The immunogenicity of NPs loaded with antigens was studied after nasal and subcutaneous immunization in mice. Three immunizations (7.5 μg antigen) were performed with 2 weeks intervals. Two weeks after the last booster dose, sera IgG subtypes were measured. After subcutaneous administration, for both nanoparticulate antigens, serum IgG1 and IgGtotal levels were higher than antigen solution (P < 0.001). After nasal administration, for env23, IgG2a levels and IgG2a/IgG1 ratio was significantly higher than groups with subcutaneous administration (P < 0.001). Both nanoparticles showed good immunoadjuvant potential. Env23 antigen was a better candidate for vaccination against HTLV-I, as it induced higher cellular immune responses, compared with env13.

Mucoadhesive therapeutic compositions: a patent review (2011-2014)

INTRODUCTION

With the introduction of mucoadhesion in 1980, pharmaceutical researchers have gained interest in mucoadhesive compositions. This interest has led to the development of mucoadhesive drug delivery systems aiming (I) to target a specific tissue, (II) to overcome barriers to absorption as well as (III) to control drug release of the therapeutic compositions.

AREAS COVERED

In this review, the term mucoadhesion and a variety of targetable mucosa are described through review of the literature. Mucoadhesive drug delivery systems and mucoadhesive polymers, such as thiomers, which are reported within the patent literature or in related publications are described in detail, including their therapeutic uses.

EXPERT OPINION

Mucoadhesion is associated with benefits such as controlled, sustained release, prolonged residence time at the site of action, the ability to target specific mucosae and ease of application which leads to higher rates of patient compliance. Although many research groups are investigating in this domain, not many drug delivery systems based on mucoadhesive polymers have got from bench to market. The most promising and advanced applications seen in patent literature within the last five years seems to be for oral application.

Controlled synthesis of N,N,N-trimethyl chitosan for modulated bioadhesion and nasal membrane permeability

In an experiment to explore the bioadhesion, biocompatibility, and membrane permeation properties, the controlled synthesis of N,N,N-trimethyl chitosan (TMC) was carried out by two-step reductive methylation of chitosan (CHT). Methylation was confirmed by (1)H NMR (δ=3.1 ppm) and FTIR analysis (CH stretch at 1,485 cm(-1)). The TMC was further characterized by DSC, TGA, XRD, HR-TEM, SEM, and elemental analysis. Findings revealed improved solubility, enhanced viscosity, increased swelling index and higher molecular weight of TMC over CHT. Comparative evaluation validated increased bioadhesion potential, and improved ex vivo biocompatibility of TMC compared to CHT. Increased bioadhesion of TMC NPs over CHT NPs can be attributed to the strong electrostatic interactions between cationic amino groups with anionic sialic and sulfonic acid moieties contained in the mucin of the nasal mucus. Ex vivo biocompatibility studies suggested that the NP formulations of both biopolymers were biocompatible and could be applied safely on the nasal epithelium. Ex vivo permeation studies executed on excised cattle nasal mucosa illustrated improved permeability of TMC NPs over CHT NPs. In the author's opinion, two-step reductive methylation of CHT could be an attractive strategy to improve its solubility, bioadhesion, and permeation characteristics without affecting biocompatibility across the mucosal surfaces.

Development of chitosan-pullulan composite nanoparticles for nasal delivery of vaccines: in vivo studies

Here, we aimed at developing chitosan/pullulan composite nanoparticles and testing their potential as novel systems for the nasal delivery of diphtheria toxoid (DT). All the chitosan derivatives [N-trimethyl (TMC), chloride and glutamate] and carboxymethyl pullulan (CMP) were synthesised and antigen-loaded composites were prepared by polyion complexation of chitosan and pullulan derivatives (particle size: 239-405 nm; surface charge: +18 and +27 mV). Their immunological effects after intranasal administration to mice were compared to intramuscular route. Composite nanoparticles induced higher levels of IgG responses than particles formed with chitosan derivative and antigen. Nasally administered TMC-pullulan composites showed higher DT serum IgG titre when compared with the other composites. Co-encapsulation of CpG ODN within TMC-CMP-DT nanoparticles resulted in a balanced Th1/Th2 response. TMC/pullulan composite nanoparticles also induced highest cytokine levels compared to those of chitosan salts. These findings demonstrated that TMC-CMP-DT composite nanoparticles are promising delivery system for nasal vaccination.

Formulation, high throughput in vitro screening and in vivo functional characterization of nanoemulsion-based intranasal vaccine adjuvants

Vaccine adjuvants have been reported to induce both mucosal and systemic immunity when applied to mucosal surfaces and this dual response appears important for protection against certain pathogens. Despite the potential advantages, however, no mucosal adjuvants are currently approved for human use. Evaluating compounds as mucosal adjuvants is a slow and costly process due to the need for lengthy animal immunogenicity studies. We have constructed a library of 112 intranasal adjuvant candidate formulations consisting of oil-in-water nanoemulsions that contain various cationic and nonionic surfactants. To facilitate adjuvant development we first evaluated this library in a series of high-throughput, in vitro assays for activities associated with innate and adaptive immune activation in vivo. These in vitro assays screened for the ability of the adjuvant to bind to mucin, induce cytotoxicity, facilitate antigen uptake in epithelial and dendritic cells, and activate cellular pathways. We then sought to determine how these parameters related to adjuvant activity in vivo. While the in vitro assays alone were not enough to predict the in vivo adjuvant activity completely, several interesting relationships were found with immune responses in mice. Furthermore, by varying the physicochemical properties of the surfactant components (charge, surfactant polar head size and hydrophobicity) and the surfactant blend ratio of the formulations, the strength and type of the immune response generated (T_H1, T_H2, T_H17) could be modulated. These findings suggest the possibility of using high-throughput screens to aid in the design of custom adjuvants with unique immunological profiles to match specific mucosal vaccine applications.

Functional nanomaterials can optimize the efficacy of vaccines

Nanoscale materials can improve the efficacy of vaccines. Herein we review latest developments that use nanomaterials for vaccines. By highlighting the relationships between the nanoscale physicochemical characteristics and working mechanisms of nanomaterials, this paper shows the current status of the developments where researchers employ functional nanomaterials as vector and/or immunoregulators for vaccines. It also provides us some clues for improving the design and application of nanomaterials to optimize the efficacy of vaccines.

Strategies for improving mucosal drug delivery

Within this review we will provide a comprehensive understanding in order to improve existing strategies and to develop new systems to lower the barrier for improving mucosal drug delivery. Mucosal administration of drugs achieves a therapeutical effect as the permeation of significant amounts of a drug is permitted through the absorption membrane. The absorption membrane relies on the mucosal layer and the epithelial tissue. In order to overcome barriers, drug delivery systems have to exhibit various functions and features, such as mucoadhesive and protective activity, solubility improving, permeation and uptake enhancing, and drug release controlling properties. This review also aims to provide an insight of well-distinguished strategies to date, as well as provide a focus on the enhancement of membrane permeability. Furthermore, since the development and functions of drug delivery systems exert a high influence on the ability of drug permeation through membrane, these considerations will also be discussed in this review.

Brain pharmacokinetics of neurotoxin-loaded PLA nanoparticles modified with chitosan after intranasal administration in awake rats

CONTEXT

Neurotoxin (NT), an analgesic peptide which was separated from the venom of Naja naja atra, is endowed an exceptional specificity of action that blocks transmission of the nerve impulse by binding to the acetylcholine receptor in the membrane. However, it has limited permeability across the blood-brain barrier (BBB).

OBJECTIVE

The purpose of this study was to encapsulate NT within polylactic acid (PLA) nanoparticles (NPs) modified with chitosan (NT-PLA-cNPs) and to evaluate their brain pharmacokinetic behaviors after intranasal (i.n.) administration using a microdialysis technique in free-moving rats.

METHODS

NT-PLA-cNPs (NT labeled with fluorescein isothiocyanate) were prepared and characterized. Then, NT-PLA-cNPs were i.n. administered to rats and the fluorescence intensity in the periaqueductal gray (PAG) was monitored for up to 480 min, with NT-PLA-NPs and NT solution as control groups.

RESULTS

The NPs prepared were spherical with a homogenous size distribution. The mean particle size, zeta potential, and entrapment efficiency were 140.5 ± 5.4 nm, +33.71 ± 3.24 mV, and 83.51 ± 2.65%, respectively. The brain transport results showed that Tmax of NT-PLA-cNPs was equal with that of NT-PLA-NPs after i.n. administration (150 min). The Cmax and AUC(0-8 h) of each group followed the following order: NT-PLA-cNPs > NT-PLA-NPs. The corresponding absolute bioavailability (Fabs) of NT-PLA-cNPs was about 151% with NT-PLA-NPs as reference preparations.

CONCLUSION

These results suggest that NPs modified with chitosan have better brain targeting efficiency and are a promising approach for i.n. delivery of large hydrophilic peptides and proteins in improving the treatment of central nervous system (CNS) disorders.

Formulation and characterization of nanoemulsion intranasal adjuvants: effects of surfactant composition on mucoadhesion and immunogenicity

The development of effective intranasal vaccines is of great interest due to their potential to induce both mucosal and systemic immunity. Here we produced oil-in-water nanoemulsion (NE) formulations containing various cationic and nonionic surfactants for use as adjuvants for the intranasal delivery of vaccine antigens. NE induced immunogenicity and antigen delivery are believed to be facilitated through initial contact interactions between the NE droplet and mucosal surfaces which promote prolonged residence of the vaccine at the site of application, and thus cellular uptake. However, the details of this mechanism have yet to be fully characterized experimentally. We have studied the physicochemical properties of the NE droplet surfactant components and demonstrate that properties such as charge and polar headgroup geometry influence the association of the adjuvant with the mucus protein, mucin. Association of NE droplets with mucin in vitro was characterized by various biophysical and imaging methods including dynamic light scattering (DLS), zeta potential (ZP), and surface plasmon resonance (SPR) measurements as well as transmission electron microscopy (TEM). Emulsion surfactant compositions were varied in a systematic manner to evaluate the effects of hydrophobicity and polar group charge/size on the NE-mucin interaction. Several cationic NE formulations were found to facilitate cellular uptake of the model antigen, ovalbumin (OVA), in a nasal epithelial cell line. Furthermore, fluorescent images of tissue sections from mice intranasally immunized with the same NEs containing green fluorescent protein (GFP) antigen demonstrated that these NEs also enhanced mucosal layer penetration and cellular uptake of antigen in vivo. NE-mucin interactions observed through biophysical measurements corresponded with the ability of the NE to enhance cellular uptake. Formulations that enhanced antigen uptake in vitro and in vivo also led to the induction of a more consistent antigen specific immune response in mice immunized with NEs containing OVA, linking NE-facilitated mucosal layer penetration and cellular uptake to enhancement of the immune response. These findings suggest that biophysical measurement of the mucoadhesive properties of emulsion based vaccines constitutes an effective in vitro strategy for selecting NE candidates for further evaluation in vivo as mucosal adjuvants.

Evaluation of mucoadhesive carrier adjuvant: toward an oral anthrax vaccine

The aim of present study was to evaluate the potential of mucoadhesive alginate-coated chitosan microparticles (A-CHMp) for oral vaccine against anthrax. The zeta potential of A-CHMp was -29.7 mV, and alginate coating could prevent the burst release of antigen in simulated gastric fluid. The results indicated that A-CHMp was mucoadhesive in nature and transported it to the peyer's patch upon oral delivery. The immunization studies indicated that A-CHMp resulted in the induction of potent systemic and mucosal immune responses, whereas alum-adjuvanted rPA could induce only systemic immune response. Thus, A-CHMp represents a promising acid carrier adjuvant for oral immunization against anthrax.

Nanovaccines : nanocarriers for antigen delivery

Vaccination has become one of the most important health interventions of our times, revolutionizing health care, and improving the quality of life and life expectancy of millions all over the world. In spite of this, vaccine research remains a vast field for innovation and improvement. Indeed, the shift towards the use of sub-unit antigens, much safer but less immunogenic, and the recognized need to facilitate the access to vaccines in the global framework is currently stimulating the search for safe and efficient adjuvants and delivery technologies. Within this context, nanocarriers have gained particular attention over the last years and appear as one of the most promising strategies for antigen delivery. A number of biomaterials and technologies can be used to design nanovaccines that fulfill the requirements of new vaccination approaches, such as single-dose and transmucosal immunization, critical for achieving a widespread coverage while reducing the overall costs in relation to traditional forms of vaccination. Here we present an overview of the current state of nanocarriers for antigen delivery, developed with the perspective of contributing to the global vaccination goal.

Moraxella catarrhalis: from interactions with the host immune system to vaccine development

Moraxella catarrhalis is a human-restricted commensal that over the last two decades has developed into an emerging respiratory tract pathogen. The bacterial species is equipped with various adhesins to facilitate its colonization. Successful evasion of the human immune system is a prerequisite for Moraxella infection. This strategy involves induction of an excessive proinflammatory response, intervention of granulocyte recruitment to the infection site, activation of selected pattern recognition receptors and cellular adhesion molecules to counteract the host bacteriolytic attack, as well as, finally, reprogramming of antigen presenting cells. Host immunomodulator molecules are also exploited by Moraxella to aid in resistance against complement killing and host bactericidal molecules. Thus, breaking the basis of Moraxella immune evasion mechanisms is fundamental for future invention of effective therapy in controlling Moraxella infection.

Recent advances in nanocarrier-based mucosal delivery of biomolecules

This review highlights the recent developments in the area of nanocarrier-based mucosal delivery of therapeutic biomolecules and antigens. Macromolecular drugs have the unique power to tackle challenging diseases but their structure, physicochemical properties, stability, pharmacodynamics, and pharmacokinetics place stringent demands on the way they are delivered into the body (e.g., inability to cross mucosal surfaces and biological membranes). Carrier-based drug delivery systems can diminish the toxicity of therapeutic biomolecules, improve their bioavailability and make possible their administration via less-invasive routes (e.g., oral, nasal, pulmonary, etc.). Thus, the development of functionalized nanocarriers and nanoparticle-based microcarriers for the delivery of macromolecular drugs is considered an important scientific challenge and at the same time a business breakthrough for the biopharmaceutical industry. In order to be translated to the clinic the nanocarriers need to be biocompatible, biodegradable, stable in biological media, non-toxic and non-immunogenic, to exhibit mucoadhesive properties, to cross mucosal barriers and to protect their sensitive payload and deliver it to its target site in a controlled manner, thus increasing significantly its bioavailability and efficacy.

Nanomaterial-mediated CNS delivery of diagnostic and therapeutic agents

Research into the diagnosis and treatment of central nervous system (CNS) diseases has been enhanced by rapid advances in nanotechnology and an expansion in the library of nanostructured carriers. This review discusses the latest applications of nanomaterials in the CNS with an emphasis on brain tumors. Novel administration routes and transport mechanisms for nanomaterial-mediated CNS delivery of diagnostic and therapeutic agents to bypass or cross the blood brain barrier (BBB) are also discussed. These include temporary disruption of the BBB, use of impregnated polymers (polymer wafers), convection-enhanced delivery (CED), and intranasal delivery. Moreover, an in vitro BBB model capable of mimicking geometrical, cellular and rheological features of the human cerebrovasculature has been developed. This is a useful tool that can be used for screening CNS nanoparticles or therapeutics prior to in vivo and clinical investigation. A discussion of this novel model is included.

Nanoparticulate adjuvants and delivery systems for allergen immunotherapy

In the last decades, significant progress in research and clinics has been made to offer possible innovative therapeutics for the management of allergic diseases. However, current allergen immunotherapy shows limitations concerning the long-term efficacy and safety due to local side effects and risk of anaphylaxis. Thus, effective and safe vaccines with reduced dose of allergen have been developed using adjuvants. Nevertheless, the use of adjuvants still has several disadvantages, which limits its use in human vaccines. In this context, several novel adjuvants for allergen immunotherapy are currently being investigated and developed. Currently, nanoparticles-based allergen-delivery systems have received much interest as potential adjuvants for allergen immunotherapy. It has been demonstrated that the incorporation of allergens into a delivery system plays an important role in the efficacy of allergy vaccines. Several nanoparticles-based delivery systems have been described, including biodegradable and nondegradable polymeric carriers. Therefore, this paper provides an overview of the current adjuvants used for allergen immunotherapy. Furthermore, nanoparticles-based allergen-delivery systems are focused as a novel and promising strategy for allergy vaccines.