Chitosan-based delivery systems for mucosal vaccines

Introduction: Mucosal vaccine development faces several challenges and opportunities. Critical issues for effective mucosal vaccination include the antigen-retention period that enables interaction with the lymphatic system, choice of adjuvant that is nontoxic and induces the required immune response and possibly an ability to mimic mucosal pathogens. Chitosan-based delivery systems are reviewed here as they address these issues and hence represent the most promising candidates for the delivery of mucosal vaccines. Areas covered: A comprehensive literature search was conducted, to locate relevant studies published within the last 5 years. Mucosal delivery via nasal and oral routes is evaluated with respect to chitosan type, dosage forms, co-adjuvanting with novel adjuvants and modulation of the immune system. Expert opinion: It is concluded that chitosan derivatives offer advantageous opportunities such as nanoparticle and surface charge manipulation that facilitate vaccine targeting. Nevertheless, these technologies represent a longer-term goal. By contrast, chitosan (unmodified form) with or without a co-adjuvant has significant toxicology and human data to support safe mucosal administration, and thus has the potential for earlier product introduction into the market.     

Immunoadjuvant potential of cross-linked dextran microspheres mixed with chitosan nanospheres encapsulated with tetanus toxoid

Context: Nasal mucosa is a desirable route for mucosal vaccine delivery. Mucosal co-administration of chitosan nanoparticles with absorption enhancers such as cross-linked dextran microspheres (CDM, Sephadex^®) is a promising antigen delivery system.

Objective: In the current study, the chitosan nanospheres loaded with tetanus toxoid (CHT:TT NPs) was prepared and characterized. The immune responses against tetanus toxoid after nasal administration of CHT:TT NPs alone or mixed with CDM were also determined.

Materials and methods: Chitosan nanospheres were prepared by ionic gelation method. Particle size, releasing profile and antigen stability were evaluated by dynamic light scattering, diffusion chamber and SDS-PAGE methods, respectively. Rabbits were nasally immunized with different formulations loaded with 40 Lf TT. After three times immunizations with 2 weeks intervals, sera IgG titres and nasal lavage sIgA titres were determined.

Results: Mean size of CHT NPs and CHT:TT NPs were 205?±?42?nm and 432?±?85?nm, respectively. The release profile showed that 42.4?±?10.5% of TT was released after 30?min and reached to a steady state after 1.5?h. Stability of encapsulated TT in nanospheres was confirmed by SDS-PAGE. The antibody titres showed that CHT:TT NPs-induced antibody titres were higher than TT solution. CHT NPs mixed with CDM induced the systemic IgG and nasal lavage sIgA titres higher than intranasal administration of TT solution (p?Discussion and conclusion: As the results indicated, these CHT:TT NPs when co-administered with CDM were able to induce more immune responses and have the potential to be used in mucosal immunization.     

Recent advances in mucosal delivery of vaccines: role of mucoadhesive/biodegradable polymeric carriers

Importance of the field: The mucosal delivery of vaccines provides the basis for induction of humoral, cellular and mucosal immune responses against infectious diseases. The delivery of antigens to and through mucosal barriers always remains challenging due to adverse physiological conditions (pH and enzymes) and biological barriers created by tight epithelial junctions restricting transportation of macromolecules. Mucoadhesive and biodegradable polymers offer numerous advantages in therapeutic delivery of proteins/antigens particularly through the mucosal route by protecting antigens from degradation, increasing concentration of antigen in the vicinity of mucosal tissue for better absorption, extending their residence time in the body and/or targeting them to sites of antigen uptake. Furthermore, antigen can be delivered more effectively to the antigen presenting cells by anchoring the ligand having affinity on the surface of carrier for the receptors present on the mucosal epithelial cells.

Areas covered in this review: The present review covers various polymeric carriers, which allow the possibility of modification and manipulation of their properties, thereby, enhancing the effectiveness of mucosal vaccines. This article reviews the recent literature and patents in the field of vaccine delivery using mucoadhesive polymeric carriers.

What the reader will gain: The reader will gain insights into various natural polymers, synthetic polymers and ligand derived polymeric carrier systems studied to enhance mucosal immunization.

Take home message: Biodegradable polymeric carriers represent a promising approach for mucosal delivery of vaccine.     

Microfold-cell targeted surface engineered polymeric nanoparticles for oral immunization

Present work was envisaged to develop novel M-cell targeted polymeric particles that are capable of protecting the antigen from harsh gastric conditions. Ulex europaeus agglutinin (UEA-1) lectin was anchored for selective delivery of antigen to gut-associated lymphoid tissue (GALT). In the present investigation, chitosan nanoparticles were prepared by ionic gelation followed by antigen (bovine serum albumin, BSA) adsorption. Developed nanoparticles were further coated by UEA-1 lectin conjugated alginate and characterized for size, shape, zeta-potential, entrapment efficiency, and in vitro release. The immunological response of the developed system were performed in Balb/c mice and compared with aluminium hydroxide gel-based conventional vaccine. Results indicated that immunization with UEA-1 lectin conjugated alginate-coated particles induces efficient systemic as well as mucosal immune responses against BSA compared to other formulations. Aluminium-based vaccine dominated throughout the study, while failed in case of mucosal antibody. Additionally, IgG1 and IgG2a isotypes were determined to confirm the TH1/TH2 mixed immune response. The developed formulation exhibited superior systemic response along with dominating mucosal immunity. These data demonstrate the potential of UEA-alginate-coated nanoparticles as effective delivery system via oral route.     

New patents on mucosal delivery of vaccines

Background: Noninvasive mucosal immune responses have been shown to be important in controlling various infections through the mucosal route. Therefore, the appropriate induction of humoral, mucosal and cellular immune response should be elicited after immunization. Objective: The objective of this review is to give an overview of novel strategies and patents for the delivery of vaccines through the mucosal route. Method: Different strategies have been developed and patented to facilitate and enhance the mucosal immunity, including the use of lipid-based delivery systems (i.e., liposomes, virosomes, archaeosomes, chochleated, immune stimulating complexes), entrapment/encapsulation of immunogens into polymeric matrix (poly(lactide-co-glycolide), chitosan, alginates, carbopol, gelatin etc.), admixing of immunogens with mucosal adjuvants (cholera toxin or CT, enterotoxin, lipid A, tetanus toxin or lymphotactin), use of live attenuated bacterial and viral vector encoding antigen of interest and ingestible plant-based mucosal vaccines. Conclusion: Lipid- and polymer-based novel delivery systems have been widely investigated in mucosal vaccine delivery systems. Recent advancement in the molecular technology has also shown great potential of genetic immunization for the delivery of wide range of infectious molecular targets. Effective and selective delivery of vaccines through the mucosal route could provide new therapeutic conduit in the treatment of mucous-associated disease.     

Chitosan-based hydrogels for nasal drug delivery: from inserts to nanoparticles

Importance of the field: Chitosan represents a multifunctional polymer, featuring both mucoadhesive and permeation-enhancing properties and therefore is a widely studied excipient for mucosal drug delivery. As regards nasal administration, chitosans have been used for the preparation of gels, solid inserts, powders and nanoparticles in which a three-dimensional network can be recognized.

Areas covered in this review: This review provides a discussion of the different nasal dosage forms based on chitosan hydrogels. In the first section intranasal delivery is discuss as a useful tool for non-invasive administration of drugs intended for local or systemic treatments. Then chitosan-based hydrogels are described with a focus on their mucoadhesive and permeation-enhancing ability as well as their capacity of controlled drug release. Finally, a detailed discussion regarding several examples of the different nasal dosage forms is reported, including considerations on in vitro, ex vivo and in vivo studies.

What the reader will gain: Summary and discussion of recent data on the different pharmaceutical forms based on chitosan hydrogels could be of interest to researchers dealing with nasal drug delivery.

Take home message: The aim of this review is to stimulate further investigations in order to achieve the collection of harmonized data and concrete clinical perspectives.     

Chitosan-based gastroretentive floating drug delivery technology: an updated review

Introduction: Gastroretentive floating drug delivery systems have emerged as efficient approaches for enhancing the bioavailability and controlled delivery of various therapeutic agents. Significant advancements exploiting chitosan have been made worldwide, in order to investigate these systems according to patient requirements, both in terms of therapeutic efficacy as well as patient compliance. Such systems precisely control the release rate of the target drug to a specific site, which facilitates an enormous impact on health care.

Areas covered: Different novel strategies have been undertaken for the development of various gastric floating dosage forms utilizing chitosan as a promising excipient. The present paper is an earnest attempt to provide new insights on various physicochemical and biological characteristics of chitosan, along with its potential applications in a wide array of biomedical approaches. Numerous and significant research findings in the vistas of chitosan-based gastroretentive floating drug delivery technology are also discussed.

Expert opinion: Chitosan has been considered as a unique and efficacious agent possessing a myriad spectrum of desired characteristics. It is emphasized that recent scientific advancements in the use of this excipient as a carrier will yield new generation gastroretentive drug delivery systems, with better pharmacotherapeutic interventions. Further studies are required to unveil the hidden beneficial properties of chitosan and its derivatives, to obtain newer delivery systems which may hold tremendous prospects in the near future.     

Mucoadhesive glycol chitosan nanoparticles for intranasal delivery of hepatitis B vaccine: enhancement of mucosal and systemic immune response

In this study, for the first time, glycol chitosan (GC) nanoparticles (NPs) were prepared and evaluated to obtain systemic and mucosal immune responses against nasally administered hepatitis B surface antigen (HBsAg). Size, zeta potential and morphology of the NPs were investigated as a function of preparation method. NPs with high loading efficacy (?>?95%) and positively charged surface were obtained with an average particle size of approximately 200?nm. The structural integrity of HBsAg in NPs was evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis and further confirmed by measuring the in vitro antigenicity using an enzyme immunoassay. During in vivo studies, GC NPs showed the lowest nasal clearance rate and better mucosal uptake when compared with chitosan (CS) NPs. The immunogenicity of NPs-based delivery system(s) was assessed by measuring anti-HBsAg antibody titer in mice serum and secretions after intranasal administration. The alum-based HBsAg vaccine injected subcutaneously was used as positive control. Results indicated that alum-based HBsAg induced strong humoral but negligible mucosal immunity. However, GC NPs induced stronger immune response at both of the fronts as compared to generated by CS NPs. This study demonstrates that this newly developed system has potential for mucosal administration of vaccines.     

Advances in using chitosan-based nanoparticles for in vitro and in vivo drug and gene delivery

Importance of the field: This review aims to provide an overview of state-of-the-art chitosan-based nanosized carriers for the delivery of therapeutic agents. Chitosan nanocarriers are smart delivery systems owing to the possibility of their property alterations with various approaches, which would confer them with the possibility of spatiotemporal delivery features.

Areas covered in this review: The focus of this review is principally on those aspects that have not often been addressed in other reviews. These include the influence of physicochemical properties of chitosan on delivery mechanisms and chitosan modification with a variety of ligand moieties specific for cell surface receptors to increase recognition and uptake of nanocarriers into cells through receptor-mediated endocytosis. Multiple examples that demonstrate the advantages of chitosan-based nanocarriers over other delivery systems of therapeutic agents are highlighted. Particular emphasis is given to the alteration of material properties by functionalization or combination with other polymers for their specific applications. Finally, structural and experimental parameters influencing transfection efficiency of chitosan-based nanocarriers are presented for both in vitro and in vivo gene delivery.

What the reader will gain: The readers will acquire knowledge of parameters influencing the properties of the chitosan-based nanocarriers for delivery of therapeutic agents (genetic material or drugs) in vitro and in vivo. They will get a better idea of the strategies to be adapted to tune the characteristics of chitosan and chitosan derivatives for specific delivery applications.

Take home message: Chitosan is prone to chemical and physical modifications, and is very responsive to environmental stimuli such as temperature and pH. These features make chitosan a smart material with great potential for developing multifunctional nanocarrier systems to deliver large varieties of therapeutic agents administrated in multiple ways with reduced side effects.     

Opportunities and challenges of the pulmonary route for vaccination

Introduction: The respiratory tract is an attractive target for the delivery of vaccine antigens. Potential advantages of drug delivery by means of the pulmonary route include accessibility, non-invasiveness, ease of administration, and the possibility to reach an elaborate mucosal network of antigen-presenting cells.

Areas covered: This review discusses current pulmonary vaccination strategies and their advantages and disadvantages.

Expert opinion: To improve efficiency of vaccination and develop new strategies, a well-founded knowledge about composition and characterization of antigen-presenting cell populations throughout the respiratory tract is essential. In particular, respiratory tract dendritic cells, as key antigen-presenting cells in the lung, constitute an ideal target for vaccine delivery. Furthermore, particle size is a key factor when designing new inhalable vaccines, as size determines not only deposition in different respiratory tract compartments, but also how an antigen and its carrier will interact with lung tissue components and immune cells. An increased knowledge of different respiratory tract antigen-presenting cell populations and their interactions with other components of the immune system will enable new targeting strategies to improve the efficacy of pulmonary vaccination.     

Designing oral vaccines targeting intestinal dendritic cells

Introduction: Most pathogens colonize and invade the host at mucosal surfaces, such as the lung and the intestine. To combat intestinal pathogens the induction of local adaptive immune responses is required, which is mainly achieved through oral vaccination. However, most vaccines are ineffective when given orally owing to the hostile environment in the gastrointestinal tract. The encapsulation of antigens in biodegradable microparticulate delivery systems enhances their immunogenicity; however, the uptake of these delivery systems by intestinal immune cells is rather poor. Surface decoration of the particulates with targeting ligands could increase the uptake and mediate the selective targeting of the vaccine to intestinal antigen-presenting cells, including dendritic cells.

Areas covered: In this review, current knowledge on dendritic cell subsets is discussed, along with progress in the development of selective antigen targeting to these cells, in addition to focusing on data obtained in mice and, where possible, the pig, as a non-rodent animal model for humans. Moreover, the potential use and benefits of Fcγ receptor-mediated targeting of antigen delivery systems are highlighted.

Expert opinion: In conclusion, dendritic cell targeting ligands grafted on antigen carrier systems should preferably bind to a conserved endocytotic receptor, facilitating the design of a multispecies vaccine platform, which could elicit robust protective immune responses against enteric pathogens.     

Topical drug delivery using chitosan nano- and microparticles

Introduction: Topical drug delivery offers important benefits for improving the therapeutic effect and reducing systemic side effects of the administered compounds. In addition, utilization of biopolymeric material-based systems can play a key role in developing new topical dosage forms and their applications. This review describes the advances that have been made, new strategies and as well as possible challenges of particular systems of chitosan used in topical drug delivery, including challenging innovations in topical usage of these systems that can make significant impact on clinical practice.

Areas covered: The main area covered is hypothesis that particulate carriers based on chitosan and its derivatives can penetrate the topical barriers from the body. For this reason, the novel studies described emphasize the fact that chitosan-based particular systems are popular that can be tailor-made according to in vitro and in vivo characterization. Such parameters, which are known to influence their in vivo performance, can be modulated by adjusting the formulation conditions of the chitosan-based particular systems for topical application.

Expert opinion: The topical application of drugs with particulate systems comprising a natural polymer, chitosan, is one of the most popular drug delivery routes. The aim of topical use of chitosan particles is to improve the drug bioavailability by prolonging the residence time of drugs applied topically or by enhancing the passing of drugs through the epithelial cells by opening the tight junctions between epithelial cells and also to reduce the side effects of the drugs.     

Protective immune responses to meningococcal C conjugate vaccine after intranasal immunization of mice with the LTK63 mutant plus chitosan or trimethyl chitosan chloride as novel delivery platform

Chitosan and its derivative N-trimethyl chitosan chloride (TMC), given as microparticles or powder suspensions, and the non-toxic mucosal adjuvant LTK63, were evaluated for intranasal immunization with the group C meningococcal conjugated vaccine (CRM-MenC). Mice immunized intranasally with CRM-MenC formulated with chitosan or TMC and the LTK63 mutant, showed high titers of serum and mucosal antibodies specific for the MenC polysaccharide. Neither significant differences were observed between microparticle formulations and powder suspensions nor when LTK63 was pre-associated to the delivery system or not. The bactericidal activity measured in serum of mice immunized intranasally with the conjugated vaccine formulated with the delivery systems and the LT mutant was superior to the activity in serum of mice immunized sub-cutaneously. Importantly, intranasal but not parenteral immunization, induced bactericidal antibodies at the nasal level, when formulated with both delivery system and adjuvant.     

Liposomal vaccine delivery systems

Introduction: Liposomes remain at the forefront of drug and vaccine design owing to their well-documented abilities to act as delivery vehicles. Nevertheless, the concept of liposomes as delivery vehicles is not a new one, with most works focusing on their use for the delivery of genes and drugs. However, in the last 10 years a significant amount of research has focused on using liposomes as vaccine adjuvants, not only as an antigen delivery vehicle but also as a tool to increase the immunogenicity of peptide and protein antigens.

Areas covered: This paper reviews liposomal adjuvants now in vaccine development, with particular emphasis on their adjuvant mechanism and how specific physicochemical characteristics of liposomes affect the immune response. The inclusion of immunomodulators is also discussed, with prominence given to Toll-like receptor ligands.

Expert opinion: The use of liposomes as vaccine delivery systems is evolving rapidly owing to the combined increase in technological advances and understanding of the immune system. Liposomes that contain and deliver immunostimulators and antigens are now being developed to target diseases that require stimulation of both humoral and cell-mediated immune responses. The CAF liposomal system, described in detail in this review, is one liposomal model that shows such flexibility.     

Intranasal formulations: promising strategy to deliver vaccines

Introduction: The emergence of new diseases and the lack of efficient vaccines against numerous nontreatable pathogens require the development of novel vaccination strategies. To date, only a few mucosal vaccines have been approved for humans. This was in part due to i) the use of live attenuated vaccines, which are not suitable for certain groups of individuals, ii) safety concerns derived from implementation in humans of some mucosal vaccines, iii) the poor stability, absorption and immunogenicity of antigens delivered by the mucosal route and iv) the limited number of available technologies to overcome the bottlenecks associated with mucosal antigen delivery. Recent advances make feasible the development of efficacious mucosal vaccines with adequate safety profile. Thus, currently intranasal vaccines represent an attractive and valid alternative to conventional vaccines.

Areas covered: The present review is focused on the potentials and limitations of market-approved intranasal vaccines and promising candidates undergoing clinical investigations. Furthermore, emerging strategies to overcome main bottlenecks including efficient breaching of the mucosal barrier and safety concerns by implementation of new adjuvants and delivery systems are discussed.

Expert opinion: The rational design of intranasal vaccines requires an in-depth understanding of the anatomic, physicochemical and barrier properties of the nasal mucosa, as well as the molecular mechanisms governing the activation of the local innate and adaptive immune system. This would provide the critical knowledge to establish effective approaches to deliver vaccine antigens across the mucosal barrier, supporting the stimulation of a long-lasting protective response at both mucosal and systemic levels. Current developments in the area of adjuvants, nanotechnologies and mucosal immunology, together with the identification of surface receptors that can be exploited for cell targeting and manipulating their physiological properties, will become instrumental for developing a new generation of more effective intranasal vaccines.     

Tetanus Toxoids Loaded Glucomannosylated Chitosan Based Nanohoming Vaccine Adjuvant with Improved Oral Stability and Immunostimulatory Response

Purpose

The present report embarks on rational designing of stable and functionalized chitosan nanoparticles for oral mucosal immunization.

Methods

Stable glucomannosylated sCh-GM-NPs were prepared by tandem cross linking method followed by lyophilization. The in vitro stability of antigen and formulation, cellular uptake and immunostimulatory response were assessed by suitable experimental protocol.

Results

Stability testing ensured the chemical and conformation permanency of encapsulated TT as well as robustness of sCh-GM-NPs in simulated biological media. The antigen release from sCh-GM-NPs followed initial burst followed by controlled Weibull’s type of release profile. The higher intracellular uptake of sCh-GM-NPs in Raw 264.7 and Caco-2 was concentration and time dependent which mainly attributed to Clathrin and receptor mediated endocytosis via mannose and glucose receptor. The in vivo evaluation in animals revealed that sCh-GM-NPs posed significantly (p?<?0.001) higher humoral, mucosal and cellular immune response than other counterparts. More importantly, commercial TT vaccine administered through oral or intramuscular route was unable to elicit all type of immune response.

Conclusion

The sCh-GM-NPs could be considered as promising vaccine adjuvant for oral tetanus immunization. Additionally, this technology expected to benefit the design and development of stable peroral formulation for administration of protein, peptides and variety of other antigens.

     

In vitro biocompatibility and release of curcumin from curcumin microcomplex-loaded chitosan scaffold

Abstract

Context: Scaffold if suitably modified could be used as a drug delivery system. Objective: To develop chitosan scaffold as a delivery system for delivering curcumin in wound-healing application. Materials and methods: Chitosan–curcumin microcomplex particles were prepared, and the effect of drug–polymer ratio (DPR) and homogenisation speed (HS) was studied using a two-level full-factorial design. Chitosan scaffold was prepared and incorporated with curcumin microcomplexes to obtain a chitosan scaffold-containing chitosan–curcumin microcomplex (CS-CCM). Antimicrobial property of the CS-CCM against Escherichia coli was studied. The cytotoxicity of CS-CCM was studied by assessing the cell viability by MTT assay. Results and discussion: DPR had a significant effect (p?≤?0.05) on the drug content. CS-CCM was able to inhibit the growth of E. coli considerably. The MTT results showed that CS-CCM is non-cytotoxic and supports cell proliferation. Conclusion: CS-CCM due to its biocompatibility and antimicrobial property could be further evaluated for potential application in wound healing.     

In vitro and ex vivo characterization of lectin-labeled Mycobacterium tuberculosis antigen-containing microspheres for enhanced oral delivery

Abstract

Purpose: Oral immunization for mucosal protection against Mycobacterium tuberculosis would be the best option for effective tuberculosis (TB) control. However, this route of vaccine delivery is limited due to the short residence time of the delivery system at the site of absorption. Cytoadhension has made it possible to optimize the targeted delivery of oral vaccine to lymphoid tissues. The purpose of this project was to evaluate the ability of human M-cell specific lectin-labeled microparticles to target the human M-cells of the Peyer’s patches.

Method: Albumin microspheres containing Mycobacterium tuberculosis cell lysate antigens were coupled with Wheat germ agglutinin and Aleuria aurantia lectins and their ability to bind to M cell models as well as their preferential distribution in the Peyer’s patches were investigated.

Results: The study demonstrated an enhanced delivery of targeted polystyrene and BSA/Lysate microspheres to M cells. It was demonstrated that alpha-l-fucose sugar residue might be the target of these lectins.

Conclusion: It can be concluded from the study that the lectin-coupled microspheres had better affinity for M-cells and showed preferential binding to the Peyer’s patches. This means that the coupling enhanced the targeted delivery of the antigens to the M cells.     

Chitosan–sodium alginate blended polyelectrolyte complexes as potential multiparticulate carrier system: colon-targeted delivery and gamma scintigraphic imaging

Objectives: The objective of this study is to develop stable, biodegradable chitosan–sodium alginate-based dual, ionic cross-linked multiparticulate system (microbeads) of tinidazole for targeted colon delivery and sustained drug release for the treatment of amoebiasis and thereby evaluating its targeting approach through in vivo gamma scintigraphic imaging technique.

Methods: The chitosan–sodium alginate-based multiparticulate system developed was producing sustained effect by virtue of its mechanical strength using double ionotropic gelation method utilizing calcium chloride and sodium sulfate as first and second cross-linkers respectively. Prepared formulations were evaluated for percent yield, drug entrapment efficiency, particle size, degree of swelling, in vitro kinetics, and in vivo targeting potentials using gamma scintigraphic imaging technique.

Results: The obtained particulates were spherical, free flowing, and had a mean particle size ranging from 1.422 mm to 1.881 mm, whereas percent yield and percent drug entrapment efficiency was found to be in between 72.61 to 82.43% and 63.25 to 79.32% respectively.

Conclusion: The prepared multiparticulate system showed better sustained release property and in vivo ability to target colon for drug delivery. Hence, the developed multiparticulate system could be a promising device to achieve greater site-specificity to colon.     

Chitosan for mucosal vaccination.

The striking advantage of mucosal vaccination is the production of local antibodies at the sites where pathogens enter the body. Because vaccines alone are not sufficiently taken up after mucosal administration, they need to be co-administered with penetration enhancers, adjuvants or encapsulated in particles. Chitosan easily forms microparticles and nanoparticles which encapsulate large amounts of antigens such as ovalbumin, diphtheria toxoid or tetanus toxoid. It has been shown that ovalbumin loaded chitosan microparticles are taken up by the Peyer's patches of the gut associated lymphoid tissue (GALT). This unique uptake demonstrates that chitosan particulate drug carrier systems are promising candidates for oral vaccination. Additionally, after co-administering chitosan with antigens in nasal vaccination studies, a strong enhancement of both mucosal and systemic immune responses is observed. This makes chitosan very suitable for nasal vaccine delivery. In conclusion, chitosan particles, powders and solutions are promising candidates for mucosal vaccine delivery. Mucosal vaccination not only reduces costs and increases patient compliance, but also complicates the invasion of pathogens through mucosal sites.