Evaluation of mucoadhesive PLGA microparticles for nasal immunization

Nanoplatform Based Intranasal Vaccines: Current Progress and Clinical Challenges

Multiple vaccine platforms have been employed to develop the nasal SARS-CoV-2 vaccines in preclinical studies, and the dominating pipelines are viral vectored as protein-based vaccines. Among them, several viral vectored-based vaccines have entered clinical development. Nevertheless, some unsatisfactory results were reported in these clinical studies. In the face of such urgent situations, it is imperative to rapidly develop the next-generation intranasal COVID-19 vaccine utilizing other technologies. Nanobased intranasal vaccines have emerged as an approach against respiratory infectious diseases. Harnessing the power of nanotechnology, these vaccines offer a noninvasive yet potent defense against pathogens, including the threat of COVID-19. The improvements made in vaccine mucosal delivery technologies based on nanoparticles, such as lipid nanoparticles, polymeric nanoparticles, inorganic nanoparticles etc., not only provide stability and controlled release but also enhance mucosal adhesion, effectively overcoming the limitations of conventional vaccines. Hence, in this review, we overview the evaluation of intranasal vaccine and highlight the current barriers. Next, the modern delivery systems based on nanoplatforms are summarized. The challenges in clinical application of nanoplatform based intranasal vaccine are finally discussed.

Chitosan non-particulate vaccine delivery systems

Chitosan is an extensively used polymer for drug delivery applications in particulate and non-particulate carriers. Chitosan-based particulate, nano-, and microparticle, carriers have been the most extensively studied for the delivery of therapeutics and vaccines. However, chitosan has also been used in vaccine applications for its adjuvant properties in various hydrogels or as a carrier coating material. The focus of this review will be on the usage of chitosan as a vaccine adjuvant based on its intrinsic immunogenicity; the various forms of chitosan-based non-particulate delivery systems such as thermosensitive hydrogels, microneedles, and conjugates; and the advantages of its role as a coating material for vaccine carriers.

Diagnostic potential of SORT1 gene in coronary artery disease

BACKGROUND

Genome-wide association studies identify SORT1 gene associated with risk of coronary artery disease (CAD). Sortilin protein enhances LDL absorption, form cell development, and atherosclerosis in macrophages.

AIM

We therefore explored SORT1 expression in CAD patients and its gene expression's predictive usefulness for the severity of the disease.

METHODOLOGY

This is a case control study and Quantitative real-time PCR; Sandwich ELISA and western blotting were used to determine the expression of SORT1 gene at the mRNA and protein level in two hundred healthy controls and two hundred patients with various CAD syndromes.

RESULTS

CAD patients exhibit higher SORT1 gene expression in CAD patients, a higher concentration of sortilin in their plasma, and distinct expression patterns in various CAD syndromes. The study reveals a positive correlation between gene expression and the severity of coronary artery stenosis, the number of diseased vessels, and the presence of diabetes. ROC curve analysis of SORT1 gene expression both at mRNA and protein level showed strong discrimination between significant CAD and control subjects.

CONCLUSION

Therefore, elevated SORT1 gene expression in various CAD syndromes may be a potential biomarker for the disease.

Hyaluronate decorated polyethylene glycol linked poly(lactide-co-glycolide) nanoparticles encapsulating MUC-1 peptide augmented mucosal immune response in Balb/c mice through inhalation route

BACKGROUND AND OBJECTIVES

NSCLC (Non-Small Cell Lung Cancer) clutches highest mortality rate in man and women globally. The present study was conducted to target MUC-1 peptide (M-1) into antigen presenting cells by cargo the peptide into hyaluronic acid decorated polyethylene glycol linked poly (D, l-lactide-co-glycolide) nanoparticles (M-1-PL-co-GA-PEG-sHA-NPs) for generating mucosal immunity through inhalation (i.h.) route.

METHODOLOGY AND RESULTS

The mean particle size and surface charge of M-1-PL-co-GA-PEG-sHA-NPs was measured to be 136.2 ± 18.38-nm and - 28.34 ± 6.77-mV, respectively, prepared by non-aggregated emulsion-diffusion evaporation method. The 28.42% percentage release of M-1 peptide from M-1-PL-co-GA-PEG-NPs was observed to be at 2 h and 95.29% at 8 h while the percentage release of M-1 peptide from M-1-PL-co-GA-PEG-sHA-NPs was observed to be 26.02% at 4 h and 97.95% at 24 h that proved the prolonged release of antigen. M-1-PL-co-GA-PEG-sHA-NPs demonstrated higher (P < 0.05) cellular uptake of 86.2% in RAW 264.7 cells in comparison to 27.6% of M-1-PL-co-GA-PEG-NPs. In addition, M-1-PL-co-GA-PEG-sHA-NPs induced remarkably (P < 0.05) elevated release of 80.6-pg/ml of TNF-α in comparison to 5-pg/ml by culture medium and 57.9-pg/ml of TNF-α by M-1-PL-co-GA-PEG-NPs. Similarly, M-1-PL-co-GA-PEG-sHA-NPs persuade remarkably (P < 0.05) elevated release of 225-pg/ml of IL-1β in comparison to 47-pg/ml by culture medium and 161.9-pg/ml of IL-1β by M-1-PL-co-GA-PEG-NPs. M-1-PL-co-GA-PEG-sHA-NPs might have been endocytosed through receptor mediated pathway owing to presence of sHA. Mice immunized through i.h. route with M-1-PL-co-GA-PEG-sHA-NPs induced strong (P < 0.05) IgA antibody titre as compared to M-1-PL-co-GA-PEG-NPs and M-1 peptide in dose-dosage regimen.

CONCLUSION

M-1-PL-co-GA-PEG-sHA-NPs nanovaccine warrants further analysis in xenograft model of NSCLC to showcase its antitumor capability.

The Role of Mucoadhesion and Mucopenetration in the Immune Response Induced by Polymer-Based Mucosal Adjuvants

Mucus is a viscoelastic gel that acts as a protective barrier for epithelial surfaces. The mucosal vehicles and adjuvants need to pass through the mucus layer to make drugs and vaccine delivery by mucosal routes possible. The mucoadhesion of polymer particle adjuvants significantly increases the contact time between vaccine formulations and the mucosa; then, the particles can penetrate the mucus layer and epithelium to reach mucosa-associated lymphoid tissues. This review presents the key findings that have aided in understanding mucoadhesion and mucopenetration while exploring the influence of physicochemical characteristics on mucus-polymer interactions. We describe polymer-based particles designed with mucoadhesive or mucopenetrating properties and discuss the impact of mucoadhesive polymers on local and systemic immune responses after mucosal immunization. In future research, more attention paid to the design and development of mucosal adjuvants could lead to more effective vaccines.

Long-term release of bioactive interferon-alpha from PLGA-chitosan microparticles: in vitro and in vivo studies

Effective cytokine treatments often require high- and multiple-dose due to the short half-life of these molecules. Here, porcine interferon-alpha (IFNα) is encapsulated in PLGA-chitosan microparticles (IFNα-MPs) to accomplish both slow drug release and drug protection from degradation. A procedure that combines emulsion and spray-drying techniques yielded almost spherical microspheres with an average diameter of 3.00 ± 1.50 μm. SEM, Microtrac, and Z-potential analyses of three IFNα-MP batches showed similar results, indicating the process is reproducible. These studies supported molecular evidence obtained in FTIR analysis, which indicated a compact structure of IFNα-MPs. Consistently, IFNα release kinetics assessed in vitro followed a zero-order behavior typical of sustained release from a polymeric matrix. This study showed that IFNα-MPs released bioactive molecules for at least 15 days, achieving IFNα protection. In addition, pigs treated with IFNα-MPs exhibited overexpression of IFNα-stimulated genes 16 days after treatment. Instead, the expression levels of these genes decreased after day 4th in pigs treated with non-encapsulated IFNα. In vitro and in vivo experiments demonstrated that the formulation improved the prophylactic and therapeutic potential of IFNα, accomplishing molecule protection and long-term release for at least two weeks. The procedure used to obtain IFNα-MPs is reproducible, scalable, and suitable for encapsulating other drugs.

Polymeric Nanoparticles for Inhaled Vaccines

Many recent studies focus on the pulmonary delivery of vaccines as it is needle-free, safe, and effective. Inhaled vaccines enhance systemic and mucosal immunization but still faces many limitations that can be resolved using polymeric nanoparticles (PNPs). This review focuses on the use of properties of PNPs, specifically chitosan and PLGA to be used in the delivery of vaccines by inhalation. It also aims to highlight that PNPs have adjuvant properties by themselves that induce cellular and humeral immunogenicity. Further, different factors influence the behavior of PNP in vivo such as size, morphology, and charge are discussed. Finally, some of the primary challenges facing PNPs are reviewed including formulation instability, reproducibility, device-related factors, patient-related factors, and industrial-level scale-up. Herein, the most important variables of PNPs that shall be defined in any PNPs to be used for pulmonary delivery are defined. Further, this study focuses on the most popular polymers used for this purpose.

Redefining the importance of polylactide-co-glycolide acid (PLGA) in drug delivery

The limitations of non-biodegradable polymers have paved the way for biodegradable polymers in the pharmaceutical and biomedical sciences over the years. Poly (lactic-co-glycolic acid) (PLGA), also known as 'Smart polymer', is one of the most successfully developed biodegradable polymers due to its favorable properties, such as biodegradability, biocompatibility, controllable drug release profile, and ability to alter surface with targeting agents for diagnosis and treatment. The release behavior of drugs from PLGA delivery devices is influenced by the physicochemical properties of PLGA. In this review, the current state of the art of PLGA, its synthesis, physicochemical properties, and degradation are discussed to enunciate the boundaries of future research in terms of its applicability with the optimized design in today's modern age. The fundamental objective of this review is to highlight the significance of PLGA as a polymer in the field of cancer, cardiovascular diseases, neurological disorders, dentistry, orthopedics, vaccine therapy, theranostics and lastly emerging epidemic diseases like COVID-19. Furthermore, the coverage of recent PLGA-based drug delivery systems including nanosystems, microsystems, scaffolds, hydrogels, etc. has been summarized. Overall, this review aims to disseminate the PLGA-driven revolution of the drug delivery arena in the pharmaceutical and biomedical industry and bridge the lacunae between material research, preclinical experimentation, and clinical reality.

Mucosal Vaccine Delivery Using Mucoadhesive Polymer Particulate Systems

Vaccination has been recently attracted as one of the most successful medical treatments of the prevalence of many infectious diseases. Mucosal vaccination has been interested in many researchers because mucosal immune responses play part in the first line of defense against pathogens. However, mucosal vaccination should find out an efficient antigen delivery system because the antigen should be protected from degradation and clearance, it should be targeted to mucosal sites, and it should stimulate mucosal and systemic immunity. Accordingly, mucoadhesive polymeric particles among the polymeric particles have gained much attention because they can protect the antigen from degradation, prolong the residence time of the antigen at the target site, and control the release of the loaded vaccine, and results in induction of mucosal and systemic immune responses. In this review, we discuss advances in the development of several kinds of mucoadhesive polymeric particles for mucosal vaccine delivery.

Synthesis and Characterization of Click Nucleic Acid Conjugated Polymeric Microparticles for DNA Delivery Applications

Microparticle-mediated nucleic acid delivery is a popular strategy to achieve therapeutic outcomes via antisense gene therapy. However, current methods used to fabricate polymeric microparticles suffer from suboptimal properties such as particle polydispersity and low encapsulation efficiency. Here, a new particulate delivery system based on step-growth thiol-Michael dispersion polymerization is reported in which a low polydispersity microparticle is functionalized with a synthetic nucleic acid mimic, namely, click nucleic acids (CNA). CNA oligomers, exhibiting an average length of approximately four nucleic acid repeat units per chain for both adenine and thymine bases, were successfully conjugated to excess thiols present in the microparticles. Effective DNA loading was obtained by simple mixing, and up to 6 ± 2 pmol of complementary DNA/mg of particle was achieved, depending on the length of DNA used. In addition, DNA loading was orders of magnitude less for noncomplementary sequences and sequences containing an alternating base mismatch. The DNA release properties were evaluated, and it was found that release could be triggered by sudden changes in temperature but was unaffected over a range of pH. Finally, phagocytosis of loaded microparticles was observed by confocal microscopy and corroborated by an increase in cellular metabolic activity up to 90%. Overall, this work suggests that CNA functionalized microparticles could be a promising platform for controlled DNA delivery.

Polymeric Nanoparticle-Based Vaccine Adjuvants and Delivery Vehicles

As vaccine formulations have progressed from including live or attenuated strains of pathogenic components for enhanced safety, developing new adjuvants to more effectively generate adaptive immune responses has become necessary. In this context, polymeric nanoparticles have emerged as a promising platform with multiple advantages, including the dual capability of adjuvant and delivery vehicle, administration via multiple routes, induction of rapid and long-lived immunity, greater shelf-life at elevated temperatures, and enhanced patient compliance. This comprehensive review describes advances in nanoparticle-based vaccines (i.e., nanovaccines) with a particular focus on polymeric particles as adjuvants and delivery vehicles. Examples of the nanovaccine approach in respiratory infections, biodefense, and cancer are discussed.

An overview of gastrointestinal mucus rheology under different pH conditions and introduction to pH-dependent rheological interactions with PLGA and chitosan nanoparticles

This review discusses the physicochemical and mechanical properties of porcine gastrointestinal mucus from a rheological point of view. Considering mucus as a viscoelastic gel that functions as a biological barrier by limiting particles passage, lubricating the gastrointestinal tract, and protecting the stomach from gastric acids. The viscoelastic and protective properties of mucus are mainly produced by its mucin network, which is stabilized through electrostatic, hydrophobic and hydrogen bonding interactions. Otherwise, mucus rheology is determined by its polyanionic nature at physiological pH. At neutral pH, mucus presents a viscous behavior produced by chains crosslinking. While, at acidic pH, mucus exhibits an elastic behavior related with the extended conformation that produces mucus gelation at the stomach. Additionally, rheology studies the degree of adhesion between a polymer-mucus mixture through rheological synergism, and how it varies at different pH conditions. Finally, mucoadhesion phenomenon is exemplified with chitosan (cationic) and poly (lactic-co-glycolic) acid (anionic) polymers.

Rational application of nanoadjuvant for mucosal vaccine delivery system

The surface of the mucosa is the biggest path through which pathogens enter the human body. We need an understanding of mucosal immune systems to use vaccines that generate protective mucosal and systemic immunity to regulate the outbreak of various infectious diseases. The better impact of the mucosal vaccine over traditional injectable vaccines are that not only do they induce efficient immune reactions to the mucosa but they are also comfortable in physical aspect & psychological aspect. The material of the vaccine includes pathogens antigens and adjuvants, which enable vaccination to be effective. Vaccines are classified into different criteria, including the used vaccine material and method of administration. Vaccines have traditionally been injected through a needle. However, as most of the pathogens first infect the mucosal surfaces, and growing interest is expressed in establishing protective immunity from the mucosa, which is accomplished through mucosal paths through vaccinosis. To improve the existing vaccines further, innovative strategies derived from interdisciplinary scientific research will need to develop new vaccine production, storage, and delivery systems. A distinctive & vast research and development platform has been set up for the growth of the next generation of mucosal vaccinations. The latest science and technological advancement in the areas of molecular biology, bio and chemical engineering, genome and system biology has provided accumulated understanding of the inborn and acquired multi-dimensional immune system. This review summarizes recent developments in the use of mucosal vaccines and their associated nanoadjuvants for the control of infectious diseases.

Intranasal Nanoparticulate Systems as Alternative Route of Drug Delivery

There is always a need for alternative and efficient methods of drug delivery. The nasal cavity can be considered as a non-invasive and efficient route of administration. It has been used for local, systemic, brain targeting, and vaccination delivery. Although many intranasal products are currently available on the market, the majority is used for local delivery with fewer products available for the other targets. As nanotechnology utilization in drug delivery has rapidly spread out, the nasal delivery has become attractive as a promising approach. Nanoparticulate systems facilitate drug transportation across the mucosal barrier, protect the drug from nasal enzyme degradation, enhance the delivery of vaccines to the lymphoid tissue of the nasal cavity with an adjuvant activity, and offer a way for peptide delivery into the brain and the systemic circulation, in addition to their potential for brain tumor treatment. This review article aims at discussing the potential benefit of the intranasal nanoparticulate systems, including nanosuspensions, lipid and surfactant, and polymer-based nanoparticles as regards productive intranasal delivery. The aim of this review is to focus on the topicalities of nanotechnology applications for intranasal delivery of local, systemic, brain, and vaccination purposes during the last decade, referring to the factors affecting delivery, regulatory aspects, and patient expectations. This review further identifies the benefits of applying the Quality by Design approaches (QbD) in product development. According to the reported studies on nanotechnology-based intranasal delivery, potential attention has been focused on brain targeting and vaccine delivery with promising outcomes. Despite the significant research effort in this field, nanoparticle-based products for intranasal delivery are not available. Thus, further efforts are required to promote the introduction of intranasal nanoparticulate products that can meet the requirements of regulatory affairs with high patient acceptance.

Modified chitosan-based nanoadjuvants enhance immunogenicity of protein antigens after mucosal vaccination

Nasal vaccination is considered to be an effective and convenient way of increasing immune responses both systemically and locally. Although various nanovaccine carriers have been introduced as potential immune adjuvants, further improvements are still needed before they can be taken to clinical usage. Chitosan-based nanovaccine carriers are one of the most widely studiedadjuvants, owing to the abilityof chitosan toopen tight junctions between nasal epithelial cells and enhance particle uptake as well as its inherent immune activating role. In present study, bovine serum albumin (BSA) loaded nanoparticles were prepared using novel aminated (aChi) and aminated plus thiolated chitosan (atChi) polymers, to further enhance mucoadhesiveness and adjuvanticity of the vaccine system by improving electrostatic interactions of polymers with negatively charged glycoproteins. Nanocarriers with optimum size and surface charge, high encapsulation efficiency of model antigen and good stability were developed. Negligible toxicity was observed in Calu-3 and A549 cell lines. In vivo studies, revealed high levels of systemic antibodies (IgG, IgG₁ and IgG_2a) throughout the study and presence of sIgA in vaginal washes showed that common mucosal system was successfully stimulated. Cytokine levels indicated a mixed Th1/Th2 immune response. A shift towards cellular immune responses was observed after nasal immunisation with antigen loaded nanoparticle formulations. These nanoparticles exhibit great potential for nasal application of vaccines.

How to characterize a nasal product. The state of the art of in vitro and ex vivo specific methods

Nasal delivery offers many benefits over other conventional routes of delivery (e.g. oral or intravenous administration). Benefits include, among others, a fast onset of action, non-invasiveness and direct access to the central nervous system. The nasal cavity is not only limited to local application (e.g. rhinosinusitis) but can also provide direct access to other sites in the body (e.g. the central nervous system or systemic circulation). However, both the anatomy and the physiology of the nose impose their own limitations, such as a small volume for delivery or rapid mucociliary clearance. To meet nasal-specific criteria, the formulator has to complete a plethora of tests, in vitro and ex vivo, to assess the efficacy and tolerance of a new drug-delivery system. Moreover, depending on the desired therapeutic effect, the delivery of the drug should target a specific pathway that could potentially be achieved through a modified release of this drug. Therefore, this review focuses on specific techniques that should be performed when a nasal formulation is developed. The review covers both the tests recommended by regulatory agencies (e.g. the Food and Drug Administration) and other complementary experiments frequently performed in the field.

Knockdown of Gene Expression in Macrophages by microRNA Mimic-Containing Poly (Lactic-co-glycolic Acid) Microparticles

Background: microRNA (miRNA) regulate target gene expression through translational repression and/or mRNA degradation and are involved in the regulation of inflammation. Macrophages are key inflammatory cells that are important in chronic inflammatory lung diseases such as cystic fibrosis (CF). Macrophage-expressed miRNA represent therapeutic drug targets, yet delivery of nucleic acids to macrophages has proved challenging. Methods: miRNAs were encapsulated in poly (lactic-co-glycolic acid) (PLGA)-based microparticles using double emulsion solvent evaporation and characterised for physicochemical features. Phorbol myristic acetate (PMA)-differentiated U937 macrophages were transfected with empty PLGA microparticles or those encapsulating a premiR-19b-3p or scrambled control miRNA mimic. miRNA internalisation and knockdown of a miR-19b-3p target gene, secretory leucoprotease inhibitor (SLPI), were determined by qRT-PCR. Results: Microparticle formulations were consistently found to be 2⁻3μm and all had a negative ζ potential (-5 mV to -14 mV). Encapsulation efficiency of premiR-19b-3p was 37.6 ± 13.4%. Levels of mature miR-19b-3p were higher in macrophages after delivery of premiR-19b-3p microparticles compared to empty or scrambled control miRNA-containing microparticles. Significant SLPI knockdown was achieved 72 hours post-delivery of premiR-19b-3p microparticles compared to controls. Conclusions: miRNA-encapsulating PLGA microparticles offer a new treatment paradigm for delivery to macrophages that could potentially be administered to CF lungs via inhalation.

Preparation of chitosan nanoparticle containing recombinant StxB antigen of EHEC and evaluation its immunogenicity in BALB/c mice

BACKGROUND AND OBJECTIVES

Escherichia coli O157:H7 is one of the most important food pathogens that produces colitis and bloody urine in humans. The Stx2B subunit is considered as one of the candidates for vaccine due to its immunogenic and adjuvant properties. Designing a mucosal vaccine using nanoparticles for protecting the antigen against degradation and controlling the release of antigen are important. The objective of the current study was to prepare nanoparticles containing the Stx2B subunit of E. coli O157:H7 and evaluation of its immunogenicity in the mouse model.

MATERIALS AND METHODS

E. coli BL21 DE3 and pET28a-stxB were used for expression of the stx2b gene. After inducing gene expression, purification of the Stx2b protein was performed. Then, chitosan nanoparticle containing recombinant Stx2B was prepared and administered to BALB/c mice. IgA and IgG titers in serum and IgA titers in feces of immunized and control mice were evaluated by the ELISA method.

RESULTS

After expression and purification of the Stx2B recombinant protein, an expected band of 13 kDa was observed on the SDS-PAGE gel and confirmed by Western Blot analysis. The size of the nanoparticle containing Stx2B was 290 nm. In the immunized mice, IgG and IgA titers were significantly increased. The immunized mice were challenged against E. coli O157:H7 Stx+ and the shedding analysis showed that colonization of bacteria in the intestinal tract decreased.

CONCLUSION

Oral administration of nanoparticles containing Stx2B as a candidate for the vaccine can induce a systemic and mucosal immune response against Stx2 toxin and can provide acceptable protection.

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.

Intranasal delivery of nanoparticle-based vaccines

Most pathogens gain access to the human body and initiate systemic infections through mucosal sites. A large number of currently marketed licensed vaccines are parenterally administered; they generate strong systemic immunity but not mucosal immunity. Nasal vaccination is an appealing strategy for the induction of mucosal-specific immunity; however, its development is mostly challenged by several factors, such as inefficient antigen uptake, its rapid mucociliary clearance, size-restricted permeation across epithelial barriers and absence of safe human mucosal adjuvants. Therefore, a safer mucosal-adjuvanting strategy or efficient mucosal delivery platform is much warranted. This review summarizes challenges and the rationale for nasal vaccine development with a special focus on the use of nanoparticles based on polymers and lipids for mucosal vaccine delivery.

Antigen-Specific Tolerization and Targeted Delivery as Therapeutic Strategies for Autoimmune Diseases

The prevalence of autoimmune disorders is increasing steadily and there is no permanent cure available. Immunomodulation through repeated exposure of antigens, known as antigen-specific immune tolerance or antigen-specific immunotherapy (ASI), is a promising approach to treat or prevent autoimmune disorders. Different optimization protocols (immunization routes, delivery systems, and approaches) are being developed to implement ASI against self-proteins. Including appropriate adjuvants, altered peptide ligand, and using multipeptides are approaches that can be used to specifically target autoimmunity. This review explores various ASI application methods, including different routes of antigen-specific sensitization, delivery systems, immunomodulators containing specific antigens, and other targeted approaches that have been successfully demonstrated to have therapeutic effects on autoimmune diseases.

Intranasal delivery of Huperzine A to the brain using lactoferrin-conjugated N-trimethylated chitosan surface-modified PLGA nanoparticles for treatment of Alzheimer's disease

Background

Safe and effective delivery of therapeutic drugs to the brain is important for successful therapy of Alzheimer’s disease (AD).

Purpose

To develop Huperzine A (HupA)-loaded, mucoadhesive and targeted polylactide-co-glycoside (PLGA) nanoparticles (NPs) with surface modification by lactoferrin (Lf)-conjugated N-trimethylated chitosan (TMC) (HupA Lf-TMC NPs) for efficient intranasal delivery of HupA to the brain for AD treatment.

Methods

HupA Lf-TMC NPs were prepared using the emulsion–solvent evaporation method and optimized using the Box–Behnken design. The particle size, zeta potential, drug entrapment efficiency, adhesion and in vitro release behavior were investigated. The cellular uptake was investigated by fluorescence microscopy and flow cytometry. MTT assay was used to evaluate the cytotoxicity of the NPs. In vivo imaging system was used to investigate brain targeting effect of NPs after intranasal administration. The biodistribution of Hup-A NPs after intranasal administration was determined by liquid chromatography–tandem mass spectrometry.

Results

Optimized HupA Lf-TMC NPs had a particle size of 153.2±13.7 nm, polydispersity index of 0.229±0.078, zeta potential of +35.6±5.2 mV, drug entrapment efficiency of 73.8%±5.7%, and sustained release in vitro over a 48 h period. Adsorption of mucin onto Lf-TMC NPs was 86.9%±1.8%, which was significantly higher than that onto PLGA NPs (32.1%±2.5%). HupA Lf-TMC NPs showed lower toxicity in the 16HBE cell line compared with HupA solution. Qualitative and quantitative cellular uptake experiments indicated that accumulation of Lf-TMC NPs was higher than nontargeted analogs in 16HBE and SH-SY5Y cells. In vivo imaging results showed that Lf-TMC NPs exhibited a higher fluorescence intensity in the brain and a longer residence time than nontargeted NPs. After intranasal administration, Lf-TMC NPs facilitated the distribution of HupA in the brain, and the values of the drug targeting index in the mouse olfactory bulb, cerebrum (with hippocampus removal), cerebellum, and hippocampus were about 2.0, 1.6, 1.9, and 1.9, respectively.

Conclusion

Lf-TMC NPs have good sustained-release effect, adhesion and targeting ability, and have a broad application prospect as a nasal drug delivery carrier.

Rational design and evaluation of HBsAg polymeric nanoparticles as antigen delivery carriers

The present work is focused on the development and evaluation of single dose sustained-release Hepatitis B surface antigen (HBsAg) loaded nanovaccine for Hepatitis B. The conventional treatment suffers from repeated administration and hence requires a booster dose. Therefore, polymeric nanovaccine of HBsAg was developed by double emulsion solvent evaporation technique, utilizing central composite design for formulation optimization. The effects of independent variables (like polymer amount, stabilizer concentration, aqueous/organic phase ratio and homogenizer speed) were also studied on critical quality attributes like particle size and entrapment efficiency. Nanovaccine was characterized in terms of physicochemical parameters, release, internalization and in vivo immunological evaluation in BALB/c mice after administration by different routes such as oral, sub-cutaneous, nasal and intramuscular. The designed nanovaccine demonstrated nanometric size with smooth surface, negative zeta potential, maximum entrapment, sustained release and better internalization in macrophage and MRC-5 cell line. The immune-stimulating activity of nanovaccine administered by different routes was evaluated by measuring anti-HBsAg titre like specific immunoglobulin IgG and IgA response and cytokine level (interleukin-2, interferon-Y) measurement. The results indicated that the nanovaccine administered by intramuscular route produced better humoral as well as cellular responses and potential carriers for antigen delivery at single dose administration via intramuscular route.

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.

Recent developments in nanocarrier-aided mucosal vaccination

To date, most of the licensed vaccines for mucosal delivery are based on live-attenuated viruses which carry the risk of regaining their pathogenicity. Therefore, the development of efficient nonviral vectors allowing the induction of potent humoral and cell-mediated immunity is regarded as an imperative scientific challenge as well as a commercial breakthrough for the pharma industries. For a successful translation to the clinic, such nanocarriers should protect the antigens from mucosal enzymes, facilitate antigen uptake by microfold cells and allow the copresentation of robust, safe for human use, mucosal adjuvants to antigen-presenting cells. Finally, the developed formulations should exhibit accuracy regarding the administered dose, a major drawback of mucosal vaccines in comparison with parenteral ones.

Development and evaluation of Desvenlafaxine loaded PLGA-chitosan nanoparticles for brain delivery

Depression is a debilitating psychiatric condition that remains the second most common cause of disability worldwide. Currently, depression affects more than 4 per cent of the world’s population. Most of the drugs intended for clinical management of depression augment the availability of neurotransmitters at the synapse by inhibiting their neuronal reuptake. However, the therapeutic efficacy of antidepressants is often compromised as they are unable to reach brain by the conventional routes of administration. The purpose of the present study was to reconnoiter the potential of mucoadhesive PLGA-chitosan nanoparticles for the delivery of encapsulated Desvenlafaxine to the brain by nose to brain delivery route for superior pharmacokinetic and pharmacodynamic profile of Desvenlafaxine. Desvenlafaxine loaded PLGA-chitosan nanoparticles were prepared by solvent emulsion evaporation technique and optimized for various physiochemical characteristics. The antidepressant efficacy of optimized Desvenlafaxine was evaluated in various rodent depression models together with the biochemical estimation of monoamines in their brain. Further, the levels of Desvenlafaxine in brain and blood plasma were determined at various time intervals for calculation of different pharmacokinetic parameters. The optimized Desvenlafaxine loaded PLGA-chitosan nanoparticles (∼172 nm/+35 mV) on intranasal administration significantly reduced the symptoms of depression and enhanced the level of monoamines in the brain in comparison with orally administered Desvenlafaxine. Nose to brain delivery of Desvenlafaxine PLGA-chitosan nanoparticles also enhanced the pharmacokinetic profile of Desvenlafaxine in brain together with their brain/blood ratio at different time points. Thus, intranasal mucoadhesive Desvenlafaxine PLGA-chitosan nanoparticles could be potentially used for the treatment of depression.

Nasal delivery of chitosan-coated poly(lactide-co-glycolide)-encapsulated honeybee (Apis mellifera) venom promotes Th 1-specific systemic and local intestinal immune responses in weaned pigs

Nasal delivery is a convenient and acceptable route for drug administration, and has been shown to elicit a much more potent local and systemic response compared with other drug delivery routes. We previously demonstrated that rectal administration of poly(lactide-co-glycolide)-encapsulated honeybee venom (P-HBV) could enhance systemic Th 1-specific immune responses. We therefore synthesized chitosan-coated P-HBV (CP-HBV) and then evaluated the immune-boosting efficacy of nasally administered CP-HBV on systemic and local intestinal immunity compared with non-chitosan-coated P-HBV. The nasally delivered CP-HBV effectively enhanced Th 1-specific responses, eliciting a significant increase in the CD3(+)CD4(+)CD8(-) Th cell population, lymphocyte proliferation capacity, and expression of Th 1 cytokines (IFN-γ, IL-12, and IL-2) in peripheral blood mononuclear cells. Furthermore, these immune-boosting effects persisted up to 21days post CP-HBV administration. Nasal administration of CP-HBV also led to an increase of not only the CD4(+) Th 1 and IFN-γ secreting CD4(+) Th 1 cell population but also Th 1-specific cytokines and transcription factors, including IL-12, IFN-γ, STAT4, and T-bet, in isolated mononuclear cells from the spleen and ileum.

Effect of Experimental Parameters on Alginate/Chitosan Microparticles for BCG Encapsulation

The aim of the present study was to develop novel Mycobacterium bovis bacille Calmette-Guérin (BCG)-loaded polymeric microparticles with optimized particle surface characteristics and biocompatibility, so that whole live attenuated bacteria could be further used for pre-exposure vaccination against Mycobacterium tuberculosis by the intranasal route. BCG was encapsulated in chitosan and alginate microparticles through three different polyionic complexation methods by high speed stirring. For comparison purposes, similar formulations were prepared with high shear homogenization and sonication. Additional optimization studies were conducted with polymers of different quality specifications in a wide range of pH values, and with three different cryoprotectors. Particle morphology, size distribution, encapsulation efficiency, surface charge, physicochemical properties and biocompatibility were assessed. Particles exhibited a micrometer size and a spherical morphology. Chitosan addition to BCG shifted the bacilli surface charge from negative zeta potential values to strongly positive ones. Chitosan of low molecular weight produced particle suspensions of lower size distribution and higher stability, allowing efficient BCG encapsulation and biocompatibility. Particle formulation consistency was improved when the availability of functional groups from alginate and chitosan was close to stoichiometric proportion. Thus, the herein described microparticulate system constitutes a promising strategy to deliver BCG vaccine by the intranasal route.

Immune response elicited by an intranasally delivered HBsAg low-dose adsorbed to poly-ε-caprolactone based nanoparticles

Among new strategies to increase hepatitis B virus (HBV) vaccination, especially in developing countries, the development of self-administered vaccines is considered one of the most valuable. Nasal vaccination using polymeric nanoparticles (NPs) constitutes a valid approach to this issue. In detail, poly-ε-caprolactone (PCL)/chitosan NPs present advantages as a mucosal vaccine delivery system: the high resistance of PCL against degradation in biological fluids and the mucoadhesive and immunostimulatory properties of chitosan. In vitro studies revealed these NPs were retained in a mucus-secreting pulmonary epithelial cell line and were capable of entering into differentiated epithelial cells. The intranasal (IN) administration of 3 different doses of HBsAg (1.5 μg, 5 μg and 10 μg) adsorbed on a fixed amount of PCL/chitosan NPs (1614 μg) generated identical titers of serum anti-HBsAg IgG and anti-HBsAg sIgA in mice nasal secretions. Besides other factors, the NP surface characteristics, particularly, zeta potential differences among the administered formulations are believed to be implicated in the outcome of the immune response generated.

Peptide/protein vaccine delivery system based on PLGA particles

Due to the excellent safety profile of poly (D,L-lactide-co-glycolide) (PLGA) particles in human, and their biodegradability, many studies have focused on the application of PLGA particles as a controlled-release vaccine delivery system. Antigenic proteins/peptides can be encapsulated into or adsorbed to the surface of PLGA particles. The gradual release of loaded antigens from PLGA particles is necessary for the induction of efficient immunity. Various factors can influence protein release rates from PLGA particles, which can be defined intrinsic features of the polymer, particle characteristics as well as protein and environmental related factors. The use of PLGA particles encapsulating antigens of different diseases such as hepatitis B, tuberculosis, chlamydia, malaria, leishmania, toxoplasma and allergy antigens will be described herein. The co-delivery of antigens and immunostimulants (IS) with PLGA particles can prevent the systemic adverse effects of immunopotentiators and activate both dendritic cells (DCs) and natural killer (NKs) cells, consequently enhancing the therapeutic efficacy of antigen-loaded PLGA particles. We will review co-delivery of different TLR ligands with antigens in various models, highlighting the specific strengths and weaknesses of the system. Strategies to enhance the immunotherapeutic effect of DC-based vaccine using PLGA particles can be designed to target DCs by functionalized PLGA particle encapsulating siRNAs of suppressive gene, and disease specific antigens. Finally, specific examples of cellular targeting where decorating the surface of PLGA particles target orally administrated vaccine to M-cells will be highlighted.

Oral administration of pH-sensitive curcumin-loaded microparticles for ulcerative colitis therapy

Oral colon-specific drug delivery is of great interest for ulcerative colitis (UC) therapy. Here, an emulsion-solvent evaporation method was used to fabricate microparticles (MPs) with pH-sensitive Eudragit S100 (ERS100) and poly(lactide-co-glycolide) (PLGA), and the MPs were loaded with curcumin (an efficient anti-inflammatory agent). The resultant spherical MPs had a desirable particle size ranging from 1.52 to 1.91 μm. Their loading efficiency could be regulated by changing the weight ratios of ERS100 and PLGA, with some MPs exhibiting loading efficiencies over 80%. It was observed that the fast release of curcumin from MPs in buffers (pH 1.2 and 6.8) could be significantly decreased by increasing the PLGA content. ERS100/PLGA MPs with a weight ratio of 1:2 (MPs-4) were able to maintain sustained release of curcumin, releasing ∼ 48% of the initial drug load at pH 7.2-7.4 during a 20 h-incubation. Most importantly, in vivo experiments revealed that orally administered MPs-4 had a superior therapeutic efficiency in alleviating colitis in a UC mouse model, compared to curcumin. Collectively, our one-step-fabricated curcumin-loaded MPs have the properties of pH-sensitivity, controlled drug release and colon targeting, and thus, may hold promise as a readily scalable drug carrier for the efficient clinical treatment of UC.

H9N2 influenza whole inactivated virus combined with polyethyleneimine strongly enhances mucosal and systemic immunity after intranasal immunization in mice

Influenza whole inactivated virus (WIV) is more immunogenic and induces protective antibody responses compared with other formulations, like split virus or subunit vaccines, after intranasal mucosal delivery. Polyethyleneimine (PEI), an organic polycation, is widely used as a reagent for gene transfection and DNA vaccine delivery. Although PEI recently has demonstrated potent mucosal adjuvant activity for viral subunit glycoprotein antigens, its immune activity with H9N2 WIV is not well demonstrated. Here, mice were immunized intranasally with H9N2 WIV combined with PEI, and the levels of local respiratory tract and systemic immune responses were measured. Compared to H9N2 WIV alone, antigen-specific IgA levels in the local nasal cavity, trachea, and lung, as well as levels of IgG and its subtypes (IgG1 and IgG2a) in the serum, were strongly enhanced with the combination. Similarly, the activation and proliferation of splenocytes were markedly increased. In addition, PEI is superior as an H9N2 WIV delivery system due to its ability to greatly increase the viral adhesion to mucosal epithelial cells and to enhance the cellular uptake and endosomal escape of antigens in dendritic cells (DCs) and further significantly activate DCs to mature. Taken together, these results provided more insights that PEI has potential as an adjuvant for H9N2 particle antigen intranasal vaccination.

Current Uses of Poly(lactic-co-glycolic acid) in the Dental Field: A Comprehensive Review

Poly(lactic-co-glycolic acid) or PLGA is a biodegradable polymer used in a wide range of medical applications. Specifically PLGA materials are also developed for the dental field in the form of scaffolds, films, membranes, microparticles, or nanoparticles. PLGA membranes have been studied with promising results, either alone or combined with other materials in bone healing procedures. PLGA scaffolds have been used to regenerate damaged tissues together with stem cell-based therapy. There is solid evidence that the development of PLGA microparticles and nanoparticles may be beneficial to a wide range of dental fields such as endodontic therapy, dental caries, dental surgery, dental implants, or periodontology. The aim of the current paper was to review the recent advances in PLGA materials and their potential uses in the dental field.

Characteristics of nasal-associated lymphoid tissue (NALT) and nasal absorption capacity in chicken

As the main mucosal immune inductive site of nasal cavity, nasal-associated lymphoid tissue (NALT) plays an important role in both antigen recognition and immune activation after intranasal immunization. However, the efficiency of intranasal vaccines is commonly restricted by the insufficient intake of antigen by the nasal mucosa, resulting from the nasal mucosal barrier and the nasal mucociliary clearance. The distribution of NALT and the characteristic of nasal cavity have already been described in humans and many laboratory rodents, while data about poultry are scarce. For this purpose, histological sections of the chicken nasal cavities were used to examine the anatomical structure and histological characteristics of nasal cavity. Besides, the absorptive capacity of chicken nasal mucosa was also studied using the materials with different particle size. Results showed that the NALT of chicken was located on the bottom of nasal septum and both sides of choanal cleft, which mainly consisted of second lymphoid follicle. A large number of lymphocytes were distributed under the mucosal epithelium of inferior nasal meatus. In addition, there were also diffuse lymphoid tissues located under the epithelium of the concha nasalis media and the walls of nasal cavity. The results of absorption experiment showed that the chicken nasal mucosa was capable to absorb trypan blue, OVA, and fluorescent latex particles. Inactivated avian influenza virus (IAIV) could be taken up by chicken nasal mucosa except for the stratified squamous epithelium sites located on the forepart of nasal cavity. The intake of IAIV by NALT was greater than that of the nasal mucosa covering on non-lymphoid tissue, which could be further enhanced after intranasal inoculation combined with sodium cholate or CpG DNA. The study on NALT and nasal absorptive capacity will be benefit for further understanding of immune mechanisms after nasal vaccination and development of nasal vaccines for poultry.

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.

Development and characterization of surface modified PLGA nanoparticles for nasal vaccine delivery: effect of mucoadhesive coating on antigen uptake and immune adjuvant activity

In this study, the efficacy of mucoadhesive polymers, i.e., chitosan and glycol chitosan as a mucoadhesive coating material in nasal vaccine delivery was investigated. The Hepatitis B surface Antigen (HBsAg) encapsulated PLGA, chitosan coated PLGA (C-PLGA), and Glycol chitosan coated PLGA (GC-PLGA) nanoparticles (NPs) were prepared. The formulations were characterized for particle size, shape, surface charge, and entrapment efficiency. The mucoadhesive ability of coated and non-coated NPs was determined using in vitro mucoadhesion and nasal clearance test. In addition, the systemic uptake and bio-distribution were also evaluated to understand the fate of NPs following nasal delivery. The immuno-adjuvant ability of various formulations was compared by measuring specific antibody titer in serum and secretory. The results indicated that PLGA NPs exhibit negative surface charge, whereas C-PLGA and GC-PLGA NPs exhibited positive surface charge. The GC-PLGA NPs demonstrated lower clearance and better local and systemic uptake compared to chitosan coated and uncoated PLGA NPs. In vivo immunogenicity studies indicated that GC-PLGA NPs could induce significantly higher systemic and mucosal immune response compared to PLGA and C-PLGA NPs. In conclusion, GC-PLGA NPs could be a promising carrier adjuvant for the nasal vaccine delivery for inducing a potent immune response at mucosal surface(s) and systemic circulation.