Immunostimulatory effect of tetanus toxoid loaded chitosan nanoparticles following microneedles assisted immunization

Chitosan: An overview of biological activities, derivatives, properties, and current advancements in biomedical applications

The second and most often utilized natural polymer is chitosan (CS), a naturally existing amino polysaccharide that is produced by deacetylating chitin. Numerous applications have been the subject of in-depth investigation due to its non-hazardous, biologically compatible, and biodegradable qualities. Chitosan's characteristics, such as mucoadhesion, improved permeability, controlled release of drugs, in situ gelation process, and antibacterial activity, depend on its amino (-NH2) and hydroxyl groups (-OH). This study examines the latest findings in chitosan research, including its characteristics, derivatives, preliminary research, toxic effects, pharmaceutical kinetics and chitosan nanoparticles (CS-NPs) based for non-parenteral delivery of drugs. Chitosan and its derivatives have a wide range of physical and chemical properties that make them highly promising for use in the medicinal and pharmaceutical industries. The characteristics and biological activities of chitosan and its derivative-based nanomaterials for the delivery of drugs, therapeutic gene transfer, delivery of vaccine, engineering tissues, evaluations, and other applications in medicine are highlighted in detail in the current review. Together with the techniques for binding medications to nanoparticles, the application of the nanoparticles was also dictated by their physical properties that were classified and specified. The most recent research investigations on delivery of drugs chitosan nanoparticle-based medication delivery methods applied topically, through the skin, and through the eyes were considered.

Flexible microneedles incorporating gold nanorods and tacrolimus for effective synergistic photothermal-chemotherapy of rheumatoid arthritis

Transdermal drug delivery systems for rheumatoid arthritis (RA) have garnered substantial attention due to their great potential to overcome limitations observed in conventional oral or injection strategies, including limited selectivity and adverse effects on extra-articular tissues. Microneedles (MNs) appear to be highly desirable carriers for transdermal drug delivery of RA. However, microneedles typically are unable to keep up with the flexibility of joints, which decreases the effectiveness of administration. In this study, we developed a flexible microneedles (FMNs) delivery system. And gelatin was employed for the fabrication of flexible backings for microneedles owing to its excellent ductility and biocompatibility. We achieved synergisticphotothermal-chemotherapy of RA by incorporating the chemical drug Tacrolimus (TAC) and the photothermal agent gold nanorods (AuNRs) into dissolving microneedles. Results showed a high mechanical strength of the proposed FMNs. In the animal model of adjuvant-induced arthritis (AA), it is indicated that the prepared FMNs inhibited the expression of related inflammatory cytokines such as IL-1ß and TNF-α while enhancing bone repair and other related factors. Thus, the combination therapy of FMNs-mediated hyperthermia and chemotherapy can serve as a novel and synergistic treatment option for RA.

Recent developments in natural biopolymer based drug delivery systems

Targeted delivery of drug molecules to diseased sites is a great challenge in pharmaceutical and biomedical sciences. Fabrication of drug delivery systems (DDS) to target and/or diagnose sick cells is an effective means to achieve good therapeutic results along with a minimal toxicological impact on healthy cells. Biopolymers are becoming an important class of materials owing to their biodegradability, good compatibility, non-toxicity, non-immunogenicity, and long blood circulation time and high drug loading ratio for both macros as well as micro-sized drug molecules. This review summarizes the recent trends in biopolymer-based DDS, forecasting their broad future clinical applications. Cellulose chitosan, starch, silk fibroins, collagen, albumin, gelatin, alginate, agar, proteins and peptides have shown potential applications in DDS. A range of synthetic techniques have been reported to design the DDS and are discussed in the current study which is being successfully employed in ocular, dental, transdermal and intranasal delivery systems. Different formulations of DDS are also overviewed in this review article along with synthesis techniques employed for designing the DDS. The possibility of these biopolymer applications points to a new route for creating unique DDS with enhanced therapeutic qualities for scaling up creative formulations up to the clinical level.

Microarray patches enable the development of skin-targeted vaccines against COVID-19

The COVID-19 pandemic is a serious threat to global health and the global economy. The ongoing race to develop a safe and efficacious vaccine to prevent infection by SARS-CoV-2, the causative agent for COVID-19, highlights the importance of vaccination to combat infectious pathogens. The highly accessible cutaneous microenvironment is an ideal target for vaccination since the skin harbors a high density of antigen-presenting cells and immune accessory cells with broad innate immune functions. Microarray patches (MAPs) are an attractive intracutaneous biocargo delivery system that enables safe, reproducible, and controlled administration of vaccine components (antigens, with or without adjuvants) to defined skin microenvironments. This review describes the structure of the SARS-CoV-2 virus and relevant antigenic targets for vaccination, summarizes key concepts of skin immunobiology in the context of prophylactic immunization, and presents an overview of MAP-mediated cutaneous vaccine delivery. Concluding remarks on MAP-based skin immunization are provided to contribute to the rational development of safe and effective MAP-delivered vaccines against emerging infectious diseases, including COVID-19.

Microneedle Arrays Combined with Nanomedicine Approaches for Transdermal Delivery of Therapeutics

Organic and inorganic nanoparticles (NPs) have shown promising outcomes in transdermal drug delivery. NPs can not only enhance the skin penetration of small/biomacromolecule therapeutic agents but can also impart control over drug release or target impaired tissue. Thanks to their unique optical, photothermal, and superparamagnetic features, NPs have been also utilized for the treatment of skin disorders, imaging, and biosensing applications. Despite the widespread transdermal applications of NPs, their delivery across the stratum corneum, which is the main skin barrier, has remained challenging. Microneedle array (MN) technology has recently revealed promising outcomes in the delivery of various formulations, especially NPs to deliver both hydrophilic and hydrophobic therapeutic agents. The present work reviews the advancements in the application of MNs and NPs for an effective transdermal delivery of a wide range of therapeutics in cancer chemotherapy and immunotherapy, photothermal and photodynamic therapy, peptide/protein vaccination, and the gene therapy of various diseases. In addition, this paper provides an overall insight on MNs' challenges and summarizes the recent achievements in clinical trials with future outlooks on the transdermal delivery of a wide range of nanomedicines.

Progress in microneedle array patch (MAP) for vaccine delivery

A microneedle array patch (MAP) has been developed as a new delivery system for vaccines. Preclinical and clinical trials with a vaccine MAP showed improved stability, safety, and immunological efficacy compared to conventional vaccine administration. Various vaccines can be delivered with a MAP. Currently, microneedle manufacturers can mass-produce pharmaceutical MAP and cosmetic MAP and this mass-production system can be adapted to produce a vaccine MAP. Clinical trials with a vaccine MAP have shown comparable efficacy with conventional administration, and discussions about regulations for a vaccine MAP are underway. However, there are concerns of reasonable cost, mass production, efficacy, and safety standards that meet FDA approval, as well as the need for feedback regarding the best method of administration. Currently, microneedles have been studied for the delivery of many kinds of vaccines, and preclinical and clinical studies of vaccine microneedles are in progress. For the foreseeable future, some vaccines will continue to be administered with syringes and needles while the use of a vaccine MAP continues to be improved because of the advantages of less pain, self-administration, improved stability, convenience, and safety.

STAR particles for enhanced topical drug and vaccine delivery

Drug delivery to the skin is highly constrained by the stratum corneum barrier layer¹. Here, we developed star-shaped particles, termed STAR particles, to dramatically increase skin permeability. STAR particles are millimeter-scale particles made of aluminum oxide or stainless steel with micron-scale projections designed to create microscopic pores across the stratum corneum. After gentle topical application for 10 s to porcine skin ex vivo, delivery of dermatological drugs and macromolecules, including those that cannot be given topically, was increased by 1 to 2 orders of magnitude. In mice treated with topical 5-fluorouracil, use of STAR particles increased the efficacy of the drug in suppressing the growth of subcutaneous melanoma tumors and prolonging survival. Moreover, topical delivery of tetanus toxoid vaccine to mice using STAR particles generated immune responses that were at least as strong as delivery of the vaccine by intramuscular injection, albeit at a higher dose for topical than intramuscular vaccine administration. STAR particles were well tolerated and effective at creating micropores when applied to the skin of human participants. Use of STAR particles provides a simple, low-cost and well-tolerated method for increasing drug and vaccine delivery to the skin and could widen the range of compounds that can be topically administered.

A fast-dissolving microneedle array loaded with chitosan nanoparticles to evoke systemic immune responses in mice

Microneedle (MN) arrays offer an alternative approach to hypodermic injection via syringe needles. In this work, polyvinylpyrrolidone (PVP)-based fast dissolving MN arrays were developed in which the needle tips were loaded with chitosan nanoparticles (NPs) for coencapsulation of a model antigen, ovalbumin (OVA), and an adjuvant, CpG oligodeoxynucleotides (CpG). After insertion into the skin, these MN arrays fully dissolved within 3 min to release antigen and adjuvant co-loaded NPs rapidly in the epidermal layer. Positively charged chitosan was proven to be an excellent carrier for negatively charged OVA and CpG, which formed nanocomplexes via simple electrostatic interactions and greatly enhanced the uptake efficiency of OVA in DC2.4 dendritic cells. Vaccination studies in mice further demonstrated that chitosan NPs effectively accumulated in peripheral lymph nodes, thus inducing greatly enhanced immune responses compared to those of free OVA. The antibody dose-response curve further demonstrated that MN immunization achieved comparable levels of immune responses as compared to conventional subcutaneous injections in a more convenient and less invasive way. Overall, a PVP-based fast dissolving MN array with chitosan NPs represents a promising and robust platform system for efficient transcutaneous vaccine delivery.

Enhanced anti-colon cancer efficacy of 5-fluorouracil by epigallocatechin-3- gallate co-loaded in wheat germ agglutinin-conjugated nanoparticles

Colon adenocarcinoma is the third most common cause of cancer-related deaths worldwide owing to its aggressive nature. Here, we developed a novel oral drug delivery system (DDS) that comprised active targeted nanoparticles made from gelatin and chitosan (non-toxic polymers). The nanoparticles were fabricated using a complex coacervation method, which was accompanied by conjugation of wheat germ agglutinin (WGA) onto their surface by glutaraldehyde cross-linking. Specifically, we integrated 5-fluorouracil (5-FU), the first-line treatment agent against colon cancer, and (-)-epigallocatechin-3-gallate (EGCG), which inhibits tumor growth via anti-angiogenesis and apoptosis-inducing effects, into the nanoparticles, named WGA-EF-NP. The 5-FU and EGCG co-loaded nanoparticles showed sustained drug release, enhanced cellular uptake, and longer circulation time. WGA-EF-NP exhibited superior anti-tumor activity and pro-apoptotic efficacy compared to the drugs and nanoparticles without WGA decoration owing to better bioavailability and longer circulation time in vivo. Thus, WGA-EF-NP shows promise as a DDS for enhanced efficacy against colon cancer.

Dissolvable Microneedle-Mediated Transcutaneous Delivery of Tetanus Toxoid Elicits Effective Immune Response

Transcutaneous immunization using a microneedle device presents a promising alternative to syringe-based injection of vaccines. The aim of this study was to investigate the effective immune response elicited after application of tetanus toxoid antigen-loaded dissolvable microneedles (TT-MN) in mice model. Dissolvable microneedles were prepared using 20% w/v of polyvinyl alcohol and polyvinyl pyrrolidone polymer mixture by micromolding technique. TT-MN were prepared by addition of tetanus toxoid to polymer mixture before casting microneedles. TT-MN were characterized using texture analyzer, stereomicroscope, and scanning electron microscope. Tetanus toxoid loading was found to be 77 ± 2 μg per microneedle array. Confocal microscopic analysis showed that the microneedles penetrated to a depth of 130 μm inside mouse skin. Complete dissolution of microneedles was achieved within 1 h after insertion in skin. Immunization studies in Swiss albino mice demonstrated significantly (p < 0.001) greater IgG, IgG₁, and IgG_2a antibody titers for TT-MN and intramuscular injection groups compared with naïve control. Splenocyte proliferation assay confirmed effective re-stimulation on exposure to tetanus toxoid in microneedle treatment groups. Taken together, TT-MN can be developed as minimally invasive system for transcutaneous delivery of tetanus toxoid antigen.

Novel approaches for the design, delivery and administration of vaccine technologies

It is easy to argue that vaccine development represents humankind's most important and successful endeavour, such is the impact that vaccination has had on human morbidity and mortality over the last 200 years. During this time the original method of Jenner and Pasteur, i.e. that of injecting live-attenuated or inactivated pathogens, has been developed and supplemented with a wide range of alternative approaches which are now in clinical use or under development. These next-generation technologies have been designed to produce a vaccine that has the effectiveness of the original live-attenuated and inactivated vaccines, but without the associated risks and limitations. Indeed, the method of development has undoubtedly moved away from Pasteur's three Is paradigm (isolate, inactivate, inject) towards an approach of rational design, made possible by improved knowledge of the pathogen-host interaction and the mechanisms of the immune system. These novel vaccines have explored methods for targeted delivery of antigenic material, as well as for the control of release profiles, so that dosing regimens can be matched to the time-lines of immune system stimulation and the realities of health-care delivery in dispersed populations. The methods by which vaccines are administered are also the subject of intense research in the hope that needle and syringe dosing, with all its associated issues regarding risk of injury, cross-infection and patient compliance, can be replaced. This review provides a detailed overview of new vaccine vectors as well as information pertaining to the novel delivery platforms under development.

Microneedles for vaccine delivery: challenges and future perspectives

Vaccine delivery to the skin using conventional needles is associated with needle-stick injuries and needle-phobia, which are all major obstacles to vaccination. The development of microneedles has enabled to overcome these limitations and as a result viral, DNA and bacterial vaccines have been studied for the delivery into the skin. Research has shown the superiority of microneedle vaccination over conventional needles in terms of immunogenicity, vaccine stability and dose-sparing abilities in animals and humans. Additional research on improving vaccine stability and delivering vaccines to other areas of the body besides the skin is ongoing as well. Thus, this review paper describes current advances in microneedles as a delivery system for vaccines as well as future perspectives for this research field.

Trimethyl Chitosan Nanoparticles Encapsulated Protective Antigen Protects the Mice Against Anthrax

Anthrax is an era old deadly disease against which there are only two currently available licensed vaccines named anthrax vaccine adsorbed and precipitated (AVP). Though they can provide a protective immunity, their multiple side-effects owing to their ill-defined composition and presence of toxic proteins (LF and EF) of Bacillus anthracis, the causative organism of anthrax, in the vaccine formulation makes their widespread use objectionable. Hence, an anthrax vaccine that contains well-defined and controlled components would be highly desirable. In this context, we have evaluated the potential of various vaccine formulations comprising of protective antigen (PA) encapsulated trimethyl-chitosan nanoparticles (TMC-PA) in conjunction with either CpG-C ODN 2395 (CpG) or Poly I:C. Each formulation was administered via three different routes, viz., subcutaneous (SC), intramuscular (IM), and intraperitoneal in female BALB/c mice. Irrespective of the route of immunization, CpG or Poly I:C adjuvanted TMC-PA nanoparticles induced a significantly higher humoral response (total serum IgG and its isotypes viz., IgG1, IgG2a, and IgG2b), compared to their CpG or Poly I:C PA counterparts. This clearly demonstrates the synergistic behavior of CpG and Poly I:C with TMC nanoparticles. The adjuvant potential of TMC nanoparticles could be observed in all the three routes as the TMC-PA nanoparticles by themselves induced IgG titers (1-1.5 × 10⁵) significantly higher than both CpG PA and Poly I:C PA groups (2-8 × 10⁴). The effect of formulations on T-helper (T_h) cell development was assessed by quantifying the Th1-dependant (TNF-α, IFN-γ, and IL-2), Th2-dependant (IL-4, IL-6, and IL-10), and Th17-type (IL-17A) cytokines. Adjuvanation with CpG and Poly I:C, the TMC-PA nanoparticles triggered a Th1 skewed immune response, as suggested by an increase in the levels of total IgG2a along with IFN-γ cytokine production. Interestingly, the TMC-PA group showed a Th2-biased immune response. Upon challenge with the B. anthracis Ames strain, CpG and Poly I:C adjuvanted TMC-PA nanoparticles immunized via the SC and IM routes showed the highest protective efficacy of ~83%. Altogether, the results suggest that CpG or Poly I:C adjuvanted, PA-loaded TMC nanoparticles could be used as an effective, non-toxic, second generation subunit-vaccine candidate against anthrax.

Combined use of nanocarriers and physical methods for percutaneous penetration enhancement

Dermal and transdermal drug delivery (due to its non-invasiveness, avoidance of the first-pass metabolism, controlling the rate of drug input over a prolonged time, etc.) have gained significant acceptance. Several methods are employed to overcome the permeability barrier of the skin, improving drug penetration into/through skin. Among chemical penetration enhancement methods, nanocarriers have been extensively studied. When applied alone, nanocarriers mostly deliver drugs to skin and can be used to treat skin diseases. To achieve effective transdermal drug delivery, nanocarriers should be applied with physical methods, as they act synergistically in enhancing drug penetration. This review describes combined use of frequently used nanocarriers (liposomes, novel elastic vesicles, lipid-based and polymer-based nanoparticles and dendrimers) with the most efficient physical methods (microneedles, iontophoresis, ultrasound and electroporation) and demonstrates superiority of the combined use of nanocarriers and physical methods in drug penetration enhancement compared to their single use.

Enhancing immunogenicity of antigens through sustained intradermal delivery using chitosan microneedles with a patch-dissolvable design

Reducing the dosage required for vaccination is highly desirable, particularly in cases of epidemic emergencies. This study evaluated the potential of a chitosan microneedle (MN) system with a patch-dissolvable design for low-dose immunization. This system comprises antigen-loaded chitosan MNs and a hydrophilic polyvinyl alcohol/polyvinyl pyrrolidone supporting array patch, which provides extra strength to achieve complete MN insertion and then quickly dissolves in the skin to reduce patch-induced skin irritation. After insertion, MNs could be directly implanted in the dermal layer as an intradermal (ID) depot to allow a sustained release of the model antigen ovalbumin (OVA) for up to 28 days. We found that rats immunized with MNs containing low-dose OVA (approximately 200 μg) had persistently high antibody levels for 18 weeks, which were significantly higher than those observed after an intramuscular injection of full-dose OVA (approximately 500 μg), demonstrating at least 2.5-fold dose sparing. Moreover, OVA-encapsulated chitosan MNs had superior immunogenicity to OVA plus chitosan solution, indicating that MN-based delivery and prolonged skin exposure can further enhance chitosan's adjuvanticity. Therefore, this patch-dissolvable MN system offers a needle-free, accurate, and reliable ID delivery of antigens and has potential as a sustained ID delivery device to improve vaccine efficacy and facilitate dose sparing with existing vaccines.

STATEMENT OF SIGNIFICANCE

This study developed implantable chitosan microneedles (MNs) with a patch-dissolvable design for the sustained intradermal (ID) delivery of antigens and demonstrated their antigen dose-sparing potential. We found that rats immunized with chitosan MNs containing low-dose OVA had persistently high antibody levels for 18 weeks, which were significantly higher than those observed after an intramuscular injection of full-dose OVA, demonstrating at least 2.5-fold dose sparing. Our results indicate that chitosan MNs can not only serve as an efficient vaccine delivery system but also exert their promising adjuvant activity by forming an ID depot for prolonged antigen exposure and activating dendritic cells for promoting immune responses.

Plant extracts: initial screening, identification of bioactive compounds and effect against Candida albicans biofilms

AIM

This study screened plants from Brazilian Pantanal for Candida albicans antibiofilm activity.

MATERIAL & METHODS

Sixty extracts were obtained from ten plants using different extraction methods. Antifungal activity was assessed. Effects on biofilm inhibition and disruption and cytotoxicity were also evaluated. The most active extract was chemically characterized.

RESULTS

Buchenavia tomentosa ethanolic extract showed noticeable antifungal activity and was selected for biofilm experiments. Subinhibitory concentration of extract inhibited fungal adhesion. Maximum killing reached 90% of C. albicans cells in suspension and 65% of cells in biofilms. The active extract was noncytotoxic. Chemical characterization showed the presence of phenols. Ellagic and gallic acids showed activity on C. albicans.

CONCLUSION

B. tomentosa extract and its isolated compound, ellagic acid, presented antibiofilm activity and low toxicity.