Surface-functionalized, pH-responsive poly(lactic-co-glycolic acid)-based microparticles for intranasal vaccine delivery: Effect of surface modification with chitosan and mannan

Amplified Targeted Drug Delivery Independent of Target Number through Alternative Administration of Two Matched Nanoparticles

Targeting nanoparticles (NPs) based on the specific binding of ligands with molecular targets provides a promising tool for tissue-selective drug delivery. However, the number of molecular targets on the cell surface is limited, hindering the number of NPs that can bind and, thus, limiting the therapeutic outcome. Although several strategies have been developed to enhance drug delivery, such as enhancing drug loading and circulation time or increasing the enhanced permeability and retention effect of nanocarriers, none have resolved this issue. Herein, we designed a simple method for amplified and targeted drug delivery using two matched NPs. One NP was aptamer-functionalized to specifically bind to target cells, while the other was aptamer-complementary DNA-functionalized to specifically bind to aptamer-NPs. Alternate administration of the two matched NPs enables their continuous accumulation in the disease site despite their limited molecular targets. As a proof of concept, the method was tested in a breast cancer model and significantly enhanced chemotherapy of tumor cells in vitro and in vivo. The potential applications of this method in a brain injury model were also demonstrated. Overall, the study describes a method for amplified targeted drug delivery independent of the target number.

Nanomaterials in tumor immunotherapy: new strategies and challenges

Tumor immunotherapy exerts its anti-tumor effects by stimulating and enhancing immune responses of the body. It has become another important modality of anti-tumor therapy with significant clinical efficacy and advantages compared to chemotherapy, radiotherapy and targeted therapy. Although various kinds of tumor immunotherapeutic drugs have emerged, the challenges faced in the delivery of these drugs, such as poor tumor permeability and low tumor cell uptake rate, had prevented their widespread application. Recently, nanomaterials had emerged as a means for treatment of different diseases due to their targeting properties, biocompatibility and functionalities. Moreover, nanomaterials possess various characteristics that overcome the defects of traditional tumor immunotherapy, such as large drug loading capacity, precise tumor targeting and easy modification, thus leading to their wide application in tumor immunotherapy. There are two main classes of novel nanoparticles mentioned in this review: organic (polymeric nanomaterials, liposomes and lipid nanoparticles) and inorganic (non-metallic nanomaterials and metallic nanomaterials). Besides, the fabrication method for nanoparticles, Nanoemulsions, was also introduced. In summary, this review article mainly discussed the research progress of tumor immunotherapy based on nanomaterials in the past few years and offers a theoretical basis for exploring novel tumor immunotherapy strategies in the future.

Bridging nanoplatform and vaccine delivery, a landscape of strategy to enhance nasal immunity

Vaccination is an urgently needed and effective option to address epidemic, cancers, allergies, and other diseases. Nasal administration of vaccines offers many benefits over needle-based injection including high compliance and less risk of infection. Inactivated or attenuated vaccines as convention vaccine present potential risks of pathogenic virulence reversal, the focus of nasal vaccine development has shifted to the use of next-generation (subunit and nucleic acid) vaccines. However, subunit and nucleic acid vaccine intranasally have numerous challenges in development and utilization due to mucociliary clearance, mucosal epithelial tight junction, and enzyme/pH degradation. Nanoplatforms as ideal delivery systems, with the ability to enhance the retention, penetration, and uptake of nasal mucosa, shows great potential in improving immunogenic efficacy of nasal vaccine. This review provides an overview of delivery strategies for overcoming nasal barrier, including mucosal adhesion, mucus penetration, targeting of antigen presenting cells (APCs), enhancement of paracellular transportation. We discuss methods of enhancing antigen immunogenicity by nanoplatforms as immune-modulators or multi-antigen co-delivery. Meanwhile, we describe the application status and development prospect of nanoplatforms for nasal vaccine administration. Development of nanoplatforms for vaccine delivery via nasal route will facilitate large-scale and faster global vaccination, helping to address the threat of epidemics.

Multiple Roles of Chitosan in Mucosal Drug Delivery: An Updated Review

Chitosan (CS) is a linear polysaccharide obtained by the deacetylation of chitin, which, after cellulose, is the second biopolymer most abundant in nature, being the primary component of the exoskeleton of crustaceans and insects. Since joining the pharmaceutical field, in the early 1990s, CS attracted great interest, which has constantly increased over the years, due to its several beneficial and favorable features, including large availability, biocompatibility, biodegradability, non-toxicity, simplicity of chemical modifications, mucoadhesion and permeation enhancer power, joined to its capability of forming films, hydrogels and micro- and nanoparticles. Moreover, its cationic character, which renders it unique among biodegradable polymers, is responsible for the ability of CS to strongly interact with different types of molecules and for its intrinsic antimicrobial, anti-inflammatory and hemostatic activities. However, its pH-dependent solubility and susceptibility to ions presence may represent serious drawbacks and require suitable strategies to be overcome. Presently, CS and its derivatives are widely investigated for a great variety of pharmaceutical applications, particularly in drug delivery. Among the alternative routes to overcome the problems related to the classic oral drug administration, the mucosal route is becoming the favorite non-invasive delivery pathway. This review aims to provide an updated overview of the applications of CS and its derivatives in novel formulations intended for different methods of mucosal drug delivery.

Targeting of sialoadhesin-expressing macrophages through antibody-conjugated (polyethylene glycol) poly(lactic-co-glycolic acid) nanoparticles

This research aims to evaluate different-sized nanoparticles consisting of (polyethylene glycol) (PEG) poly(lactic-co-glycolic acid) (PLGA), loaded with fluorescein isothiocyanate for nanoparticle uptake and intracellular fate in sialoadhesin-expressing macrophages, while being functionalized with anti-sialoadhesin antibody. Sialoadhesin is a macrophage-restricted receptor, expressed on certain populations of resident tissue macrophages, yet is also upregulated in some inflammatory conditions. The nanocarriers were characterized for nanoparticle size (84-319 nm), zeta potential, encapsulation efficiency, and in vitro dye release. Small (86 nm) antibody-functionalized PEG PLGA nanoparticles showed persisting benefit from sialoadhesin-targeting after 24 h compared to the control groups. For small (105 nm) PLGA nanoparticles, uptake rate was higher for antibody-conjugated nanoparticles, though the total amount of uptake was not enhanced after 24 h. For both plain and functionalized small-sized (PEG) PLGA nanoparticles, no co-localization between nanoparticles and (early/late) endosomes nor lysosomes could be observed after 1-, 4-, or 24-h incubation time. In conclusion, decorating (PEG) PLGA nanocarriers with anti-sialoadhesin antibodies positively impacts macrophage targeting, though it was found to be formulation-specific.

Engineered Nanoparticulate Vaccines to Combat Recurring and Pandemic Influenza Threats

Reoccurring seasonal flu epidemics and occasional pandemics are among the most severe threats to public health. Current seasonal influenza vaccines provide limited protection against drifted circulating strains and no protection against influenza pandemics. Next-generation influenza vaccines, designated as universal influenza vaccines, should be safe, affordable, and elicit long-lasting cross-protective influenza immunity. Nanotechnology plays a critical role in the development of such novel vaccines. Engineered nanoparticles can incorporate multiple advantageous properties into the same nanoparticulate platforms to improve vaccine potency and breadth. These immunological properties include virus-like biomimicry, high antigen-load, controlled antigen release, targeted delivery, and induction of innate signaling pathways. Many nanoparticle influenza vaccines have shown promising results in generating potent and broadly protective immune responses. This review will summarize the necessity and characteristics of next-generation influenza vaccines and the immunological correlates of broad influenza immunity and focus on how cutting-edge nanoparticle technology contributes to such vaccine development. The review will give new insights into the rational design of nanoparticle universal vaccines to combat influenza epidemics and pandemics.

Carbohydrate-containing nanoparticles as vaccine adjuvants

Introduction: Adjuvants are essential to vaccines for immunopotentiation in the elicitation of protective immunity. However, classical and widely used aluminum-based adjuvants have limited capacity to induce cellular response. There are increasing needs for appropriate adjuvants with improved profiles for vaccine development toward emerging pathogens. Carbohydrate-containing nanoparticles (NPs) with immunomodulatory activity and particulate nanocarriers for effective antigen presentation are capable of eliciting a more balanced humoral and cellular immune response.Areas covered: We reviewed several carbohydrates with immunomodulatory properties. They include chitosan, β-glucan, mannan, and saponins, which have been used in vaccine formulations. The mode of action, the preparation methods, characterization of these carbohydrate-containing NPs and the corresponding vaccines are presented.Expert opinion: Several carbohydrate-containing NPs have entered the clinical stage or have been used in licensed vaccines for human use. Saponin-containing NPs are being evaluated in a vaccine against SARS-CoV-2, the pathogen causing the on-going worldwide pandemic. Vaccines with carbohydrate-containing NPs are in different stages of development, from preclinical studies to late-stage clinical trials. A better understanding of the mode of action for carbohydrate-containing NPs as vaccine carriers and as immunostimulators will likely contribute to the design and development of new generation vaccines against cancer and infectious diseases.

Hitchhiking on Controlled-Release Drug Delivery Systems: Opportunities and Challenges for Cancer Vaccines

Cancer vaccines represent among the most promising strategies in the battle against cancers. However, the clinical efficacy of current cancer vaccines is largely limited by the lack of optimized delivery systems to generate strong and persistent antitumor immune responses. Moreover, most cancer vaccines require multiple injections to boost the immune responses, leading to poor patient compliance. Controlled-release drug delivery systems are able to address these issues by presenting drugs in a controlled spatiotemporal manner, which allows co-delivery of multiple drugs, reduction of dosing frequency and avoidance of significant systemic toxicities. In this review, we outline the recent progress in cancer vaccines including subunit vaccines, genetic vaccines, dendritic cell-based vaccines, tumor cell-based vaccines and in situ vaccines. Furthermore, we highlight the efforts and challenges of controlled or sustained release drug delivery systems (e.g., microparticles, scaffolds, injectable gels, and microneedles) in ameliorating the safety, effectiveness and operability of cancer vaccines. Finally, we briefly discuss the correlations of vaccine release kinetics and the immune responses to enlighten the rational design of the next-generation platforms for cancer therapy.

Recent advances in the formulation of PLGA microparticles for controlled drug delivery

Polymeric microparticles (MPs) are recognized as very popular carriers to increase the bioavailability and bio-distribution of both lipophilic and hydrophilic drugs. Among different kinds of polymers, poly-(lactic-co-glycolic acid) (PLGA) is one of the most accepted materials for this purpose, because of its biodegradability (due to the presence of ester linkages that are degraded by hydrolysis in aqueous environments) and safety (PLGA is a Food and Drug Administration (FDA)-approved compound). Moreover, its biodegradability depends on the number of glycolide units present in the structure, indeed, lower glycol content results in an increased degradation time and conversely a higher monomer unit number results in a decreased time. Due to this feature, it is possible to design and fabricate MPs with a programmable and time-controlled drug release. Many approaches and procedures can be used to prepare MPs. The chosen fabrication methodology influences size, stability, entrapment efficiency, and MPs release kinetics. For example, lipophilic drugs as chemotherapeutic agents (doxorubicin), anti-inflammatory non-steroidal (indomethacin), and nutraceuticals (curcumin) were successfully encapsulated in MPs prepared by single emulsion technique, while water-soluble compounds, such as aptamer, peptides and proteins, involved the use of double emulsion systems to provide a hydrophilic compartment and prevent molecular degradation. The purpose of this review is to provide an overview about the preparation and characterization of drug-loaded PLGA MPs obtained by single, double emulsion and microfluidic techniques, and their current applications in the pharmaceutical industry.Graphic abstract.

Improving cellular uptake and cytotoxicity of chitosan-coated poly(lactic-co-glycolic acid) nanoparticles in macrophages

Aim: This research aims to identify important formulation parameters for the enhancement of nanoparticle (NP) uptake and decreasing the cytotoxicity in macrophages. Materials & methods: Fluorescent poly(lactic-co-glycolic acid) (PLGA) nanocarriers were characterized for size distributions, zeta potential and encapsulation efficiency. Incubation time, size class, PLGA derivative and chitosan derivative were assessed for uptake kinetics and cell viability. Results: The major determining factor for enhancing cellular uptake were chitosan coatings, combined with acid-terminated PLGA and small NP size. Moreover, cytotoxicity was more favorable for small, chitosan glutamate-coated, acid-terminated PLGA NPs compared with its plain chitosan-coated counterparts. Conclusion: Chitosan glutamate has been shown to be a valuable alternative coating material for acid-terminated PLGA NPs to efficiently and safely target macrophages.

Nucleic Acid-Based Approaches for Tumor Therapy

Within the last decade, the introduction of checkpoint inhibitors proposed to boost the patients' anti-tumor immune response has proven the efficacy of immunotherapeutic approaches for tumor therapy. Furthermore, especially in the context of the development of biocompatible, cell type targeting nano-carriers, nucleic acid-based drugs aimed to initiate and to enhance anti-tumor responses have come of age. This review intends to provide a comprehensive overview of the current state of the therapeutic use of nucleic acids for cancer treatment on various levels, comprising (i) mRNA and DNA-based vaccines to be expressed by antigen presenting cells evoking sustained anti-tumor T cell responses, (ii) molecular adjuvants, (iii) strategies to inhibit/reprogram tumor-induced regulatory immune cells e.g., by RNA interference (RNAi), (iv) genetically tailored T cells and natural killer cells to directly recognize tumor antigens, and (v) killing of tumor cells, and reprograming of constituents of the tumor microenvironment by gene transfer and RNAi. Aside from further improvements of individual nucleic acid-based drugs, the major perspective for successful cancer therapy will be combination treatments employing conventional regimens as well as immunotherapeutics like checkpoint inhibitors and nucleic acid-based drugs, each acting on several levels to adequately counter-act tumor immune evasion.

Rhein laden pH-responsive polymeric nanoparticles for treatment of osteoarthritis

Osteoarthritis (OA) is a condition associated with severe inflammation, cartilage destruction and degeneration of joints. Rhein (Rh) is an effective anti-inflammatory drug with proven efficacy in in-vitro and in-vivo models. pH sensitive Rh and NH₄HCO₃ laden poly (lactic-co-glycolic acid (PLGA) nanoparticles (NPs) (Rh-PLGA-NPs@NH₄) are developed for an effective treatment of OA. The Rh-PLGA-NPs@NH₄ are prepared along with Rh-PLGA-NPs as a control by double emulsion method. Rh-PLGA-NPs@NH₄ was characterized for their size, shape, morphology and encapsulation efficiency (EE). The effect of pH on release of Rh from Rh-PLGA-NPs@NH₄ was studied at different pH. Further, the cytotoxicity effect of Rh-PLGA-NPs@NH₄ on THP-1 cells were evaluated. Anti-inflammatory efficacy was evaluated on LPS stimulated THP-1 cells and the release of pro-inflammatory cytokines was evaluated and compared with control. The size of Rh-PLGA-NPs@NH₄ and Rh-PLGA-NPs was found to be 190.7 ± 1.2 nm and 134.6 ± 2.4 nm respectively with poly dispersity (PDI) 0.14 and 0.15. The zeta potential of Rh-PLGA-NPs@NH₄ was found to be -22 ± 1.12 mV. Rh-PLGA-NPs@NH₄ were uniform, smooth and spherical shape as confirmed using electron microscopy analysis. Rh-PLGA-NPs@NH₄ release the Rh more effectively in the low pH of synovial fluid environment (SFE). Rh-PLGA-NPs@NH₄ also significantly affect inflammatory cytokines TNF-α and IL-1β and reduced their release in LPS stimulated THP-1 cells. Reactive oxygen species (ROS), a mediator responsible for the cartilage collapse was also found to be reduced. Results proposes that Rh-PLGA-NPs could provide therapeutic solution to those patients who suffer from chronic joint ailments by reducing the progression of OA.

Co-delivery of antigen and dual adjuvants by aluminum hydroxide nanoparticles for enhanced immune responses

Adjuvants that contain pathogen-associated molecular patterns (PAMPs) can enhance vaccination efficacy by binding to pattern recognition receptors (PRRs), thereby stimulating immune responses. Particularly effective may be the combination of multiple PAMPs that activate different PRRs, which occurs with natural pathogens. Here we hypothesized the enhanced effects would occur in two adjuvants that stimulate different PRRs: CpG oligodeoxynucleotide (CpG-ODN), which is Toll-like receptor 9 agonist; and 5'-triphosphate, short, double-stranded RNA (3pRNA), which activates retinoic acid-inducible gene I (RIG-I). The model antigen ovalbumin (OVA) was loaded and adjuvants were surface-adsorbed to aluminum hydroxide nanoparticles (hereafter NP-3pRNA-CpG) by electrostatic interaction with an average size of 120 nm and a negative surface charge for targeting lymph nodes. These nanoparticles were efficiently internalized by antigen-presenting cells (APCs) in the lymph nodes, and the resulting APC activation and antigen cross-presentation generated strong humoral immunity and cytotoxic T lymphocyte responses and IFN-γ secretion. NP-3pRNA-CpG significantly suppressed B16-OVA tumor growth and prolonged survival of tumor-bearing mice in therapeutic and prophylactic models, illustrating the enhanced effects of CpG-ODN and 3pRNA. Our study highlights the potential of combining multiple adjuvants for effective vaccine design.

Technological Approaches for Improving Vaccination Compliance and Coverage

Vaccination has been well recognised as a critically important tool in preventing infectious disease, yet incomplete immunisation coverage remains a major obstacle to achieving disease control and eradication. As medical products for global access, vaccines need to be safe, effective and inexpensive. In line with these goals, continuous improvements of vaccine delivery strategies are necessary to achieve the full potential of immunisation. Novel technologies related to vaccine delivery and route of administration, use of advanced adjuvants and controlled antigen release (single-dose immunisation) approaches are expected to contribute to improved coverage and patient compliance. This review discusses the application of micro- and nano-technologies in the alternative routes of vaccine administration (mucosal and cutaneous vaccination), oral vaccine delivery as well as vaccine encapsulation with the aim of controlled antigen release for single-dose vaccination.

Chitin and Chitosans: Characteristics, Eco-Friendly Processes, and Applications in Cosmetic Science

Huge amounts of chitin and chitosans can be found in the biosphere as important constituents of the exoskeleton of many organisms and as waste by worldwide seafood companies. Presently, politicians, environmentalists, and industrialists encourage the use of these marine polysaccharides as a renewable source developed by alternative eco-friendly processes, especially in the production of regular cosmetics. The aim of this review is to outline the physicochemical and biological properties and the different bioextraction methods of chitin and chitosan sources, focusing on enzymatic deproteinization, bacteria fermentation, and enzymatic deacetylation methods. Thanks to their biodegradability, non-toxicity, biocompatibility, and bioactivity, the applications of these marine polymers are widely used in the contemporary manufacturing of biomedical and pharmaceutical products. In the end, advanced cosmetics based on chitin and chitosans are presented, analyzing different therapeutic aspects regarding skin, hair, nail, and oral care. The innovative formulations described can be considered excellent candidates for the prevention and treatment of several diseases associated with different body anatomical sectors.

DNA Vaccines-How Far From Clinical Use?

Two decades ago successful transfection of antigen presenting cells (APC) in vivo was demonstrated which resulted in the induction of primary adaptive immune responses. Due to the good biocompatibility of plasmid DNA, their cost-efficient production and long shelf life, many researchers aimed to develop DNA vaccine-based immunotherapeutic strategies for treatment of infections and cancer, but also autoimmune diseases and allergies. This review aims to summarize our current knowledge on the course of action of DNA vaccines, and which factors are responsible for the poor immunogenicity in human so far. Important optimization steps that improve DNA transfection efficiency comprise the introduction of DNA-complexing nano-carriers aimed to prevent extracellular DNA degradation, enabling APC targeting, and enhanced endo/lysosomal escape of DNA. Attachment of virus-derived nuclear localization sequences facilitates nuclear entry of DNA. Improvements in DNA vaccine design include the use of APC-specific promotors for transcriptional targeting, the arrangement of multiple antigen sequences, the co-delivery of molecular adjuvants to prevent tolerance induction, and strategies to circumvent potential inhibitory effects of the vector backbone. Successful clinical use of DNA vaccines may require combined employment of all of these parameters, and combination treatment with additional drugs.

Chemical Modification of Chitosan for Efficient Vaccine Delivery

Chitosan, which exhibits good biocompatibility, safety, microbial degradation and other excellent performances, has found application in all walks of life. In the field of medicine, usage of chitosan for the delivery of vaccine is favored by a wide range of researchers. However, due to its own natural limitations, its application has been constrained to the beginning of study. In order to improve the applicability for vaccine delivery, researchers have carried out various chemical modifications of chitosan. This review summarizes a variety of modification methods and applications of chitosan and its derivatives in the field of vaccine delivery.

Co-delivery of polyinosinic:polycytidylic acid and flagellin by poly(lactic-co-glycolic acid) MPs synergistically enhances immune response elicited by intranasally delivered hepatitis B surface antigen

The aim of the present work was to investigate the synergistic effect between toll-like receptor (TLR) 3 ligand polyinosinic:polycytidylic acid (pI:C) and TLR5 ligand flagellin (FLN) on immune responses induced by nasally delivered hepatitis B virus surface antigen (HBsAg). Mannan and chitosan oligosaccharide-modified, pH-responsive poly(lactic-co-glycolic acid) (MC-PLGA) microparticles (MPs) containing HBsAg, FLN, pI:C or both ligands were prepared with a double-emulsion method. In vitro uptake experiments show that cellular uptake of MC-PLGA MPs by macrophages was through energy-dependent, receptor-mediated endocytosis mechanism. After uptake of MPs by macrophages, MC-PLGA MPs existed both in the endo-some and in the cytoplasm. FLN and pI:C in solution or MP formulation could synergize to activate macrophages and induce higher pro-inflammatory cytokines interleukin (IL)-6, IL-12, interferon-γ and anti-inflammatory cytokines IL-10 compared to single TLR ligand (P<0.05). In vivo immunogenicity studies indicated that co-delivery of FLN and pI:C within MC-PLGA MPs synergistically induced higher serum anti-HBsAg IgG levels and Th1 cytokine levels compared with MC-PLGA MPs encapsulated single TLR ligand plus MPs encapsulated HBsAg (P<0.05). These results suggest that synergic TLR3 and TLR5 stimulation might be a promising novel tool for nasally delivered HBsAg.

Synthetic Biodegradable Microparticle and Nanoparticle Vaccines against the Respiratory Syncytial Virus

Synthetic biodegradable microparticle and nanoparticle platform technology provides the opportunity to design particles varying in composition, size, shape and surface properties for application in vaccine development. The use of particle vaccine formulations allows improvement of antigen stability and immunogenicity while allowing targeted delivery and slow release. This technology has been design to develop novel vaccines against the respiratory syncytial virus (RSV), the leading cause of lower respiratory tract infection in infants. In the last decade, several nano- and micro-sized RSV vaccine candidates have been developed and tested in animal models showing promising results. This review provides an overview of recent advances in prophylactic particle vaccines for RSV and the multiple factors that can affect vaccine efficacy.