Dissolving polymer microneedle patches for influenza vaccination

BioMEMS in drug delivery

The drive to design micro-scale medical devices which can be reliably and uniformly mass produced has prompted many researchers to adapt processing technologies from the semiconductor industry. By operating at a much smaller length scale, the resulting biologically-oriented microelectromechanical systems (BioMEMS) provide many opportunities for improved drug delivery: Low-dose vaccinations and painless transdermal drug delivery are possible through precisely engineered microneedles which pierce the skin's barrier layer without reaching the nerves. Low-power, low-volume BioMEMS pumps and reservoirs can be implanted where conventional pumping systems cannot. Drug formulations with geometrically complex, extremely uniform micro- and nano-particles are formed through micromolding or with microfluidic devices. This review describes these BioMEMS technologies and discusses their current state of implementation. As these technologies continue to develop and capitalize on their simpler integration with other MEMS-based systems such as computer controls and telemetry, BioMEMS' impact on the field of drug delivery will continue to increase.

Engineering synthetic vaccines using cues from natural immunity

Vaccines aim to protect against or treat diseases through manipulation of the immune response, promoting either immunity or tolerance. In the former case, vaccines generate antibodies and T cells poised to protect against future pathogen encounter or attack diseased cells such as tumours; in the latter case, which is far less developed, vaccines block pathogenic autoreactive T cells and autoantibodies that target self tissue. Enormous challenges remain, however, as a consequence of our incomplete understanding of human immunity. A rapidly growing field of research is the design of vaccines based on synthetic materials to target organs, tissues, cells or intracellular compartments; to co-deliver immunomodulatory signals that control the quality of the immune response; or to act directly as immune regulators. There exists great potential for well-defined materials to further our understanding of immunity. Here we describe recent advances in the design of synthetic materials to direct immune responses, highlighting successes and challenges in prophylactic, therapeutic and tolerance-inducing vaccines.

Dissolving polymer microneedle patches for rapid and efficient transdermal delivery of insulin to diabetic rats

This study presents a dissolving microneedle patch, composed of starch and gelatin, for the rapid and efficient transdermal delivery of insulin. The microneedles completely dissolve after insertion into the skin for 5 min, quickly releasing their encapsulated payload into the skin. A histological examination shows that the microneedles have sufficient mechanical strength to be inserted in vitro into porcine skin to a depth of approximately 200 μm and in vivo into rat skin to 200-250 μm depth. This penetration depth does not induce notable skin irritation or pain sensation. To evaluate the feasibility of using these dissolving microneedles for diabetes treatment insulin-loaded microneedles were administered to diabetic rats using a homemade applicator. Pharmacodynamic and pharmacokinetic results show a similar hypoglycemic effect in rats receiving insulin-loaded microneedles and a subcutaneous injection of insulin. The relative pharmacological availability and relative bioavailability of insulin were both approximately 92%, demonstrating that insulin retains its pharmacological activity after encapsulation and release from the microneedles. Storage stability analysis confirms that more than 90% of the insulin remained in the microneedles even after storage at 25 or 37°C for 1 month. These results confirm that the proposed starch/gelatin microneedles enable stable encapsulation of bioactive molecules and have great potential for transdermal delivery of protein drugs in a relatively painless, rapid, and convenient manner.

Rapidly-dissolvable microneedle patches via a highly scalable and reproducible soft lithography approach

Microneedle devices for transdermal drug delivery have recently become an attractive method to overcome the diffusion-limiting epidermis and effectively transport therapeutics to the body. Here, we demonstrate the fabrication of highly reproducible and completely dissolvable polymer microneedles on flexible water-soluble substrates. These biocompatible microneedles (made by using a soft lithography process known as PRINT) showed efficacy in piercing both murine and human skin samples and delivering a fluorescent drug surrogate to the tissue.

Polyvinylpyrrolidone microneedles enable delivery of intact proteins for diagnostic and therapeutic applications

We present a method of fabricating microneedles from polyvinylpyrrolidone (PVP) that enables delivery of intact proteins (or peptides) to the dermal layers of the skin. PVP is known to self-assemble into branched hollow fibers in aqueous and alcoholic solutions; we utilized this property to develop dissolvable patches of microneedles. Proteins were dissolved in concentrated PVP solution in both alcohol and water, poured into polydimethylsiloxane templates shaped as microneedles and, upon evaporation of solvent, formed into concentric, fibrous, layered structures. This approach of making PVP microneedles overcomes problems in dosage, uniform delivery and stability of protein formulation as compared to protein-coated metallic microneedles or photopolymerized PVP microneedles. Here we characterize the PVP microneedles and measure the delivery of proteins into skin. We show that our method of fabrication preserves the protein conformation. These microneedles can serve as a broadly useful platform for delivering protein antigens and therapeutic proteins to the skin, for example for allergen skin testing or immunotherapy.

Long-term protective immunity from an influenza virus-like particle vaccine administered with a microneedle patch

Skin vaccination with influenza virus-like particles (VLPs) using microneedles has been shown to induce protection similar to or better than that induced by intramuscular immunization. In this study, we examined the long-term protective efficacy of influenza (H1N1 A/PR/8/34) VLPs after skin vaccination using microneedle patches coated with the vaccine. Microneedle vaccination of mice in the skin induced 100% protection against lethal challenge infection with influenza A/PR/8/34 virus 14 months after a single vaccine dose. Influenza virus-specific total IgG response and hemagglutination inhibition (HAI) titers were maintained at high levels for over 1 year after microneedle vaccination. Microneedle vaccination also induced substantial levels of lung IgG and IgA antibody responses, and antibody-secreting plasma cells from spleen and bone marrow, as well as conferring effective control of lung viral loads, resulting in complete protection 14 months after vaccination. These strong and long-lasting immune responses were enabled in part by stabilization of the vaccine by formulation with trehalose during microneedle patch fabrication. Administration of the stabilized vaccine using microneedles was especially effective at enabling strong recall responses measured 4 days after lethal virus challenge, including increased HAI and antibody-secreting cells in the spleen and reduced viral titer and inflammatory response in the lung. The results in this study indicate that skin vaccination with VLP vaccine using a microneedle patch provides long-term protection against influenza in mice.

Therapeutic opportunities for manipulating T(Reg) cells in autoimmunity and cancer

Forkhead box P3 (FOXP3)-expressing regulatory T (T(Reg)) cells have a pivotal role in the regulation of immune responses and in the maintenance of immunological self-tolerance. These cells have emerged as attractive targets for strategies that allow the steering of immune responses in desired directions - arming the immune system to destroy infected cells and cancer cells or downregulating it to limit tissue destruction in autoimmunity. Efforts to understand the generation, activation and function of T(Reg) cells should permit the development of therapeutics for reprogramming the immune system. In this Review, we discuss insights into the generation of T(Reg) cells, their involvement in disease and the molecular basis of the dominant tolerance exerted by FOXP3(+) T(Reg) cells that could permit their safe and specific manipulation in humans.

Skin-resident antigen-presenting cells: instruction manual for vaccine development

The induction of antigen-specific effector T cells is driven by proper antigen presentation and co-stimulation by dendritic cells (DCs). For this reason strategies have been developed to instruct DCs for the induction of CD4⁺ and CD8⁺ T cell responses. Since DCs are localized, amongst other locations, in peripheral tissues such as the skin, new vaccines are aiming at targeting antigens to DCs in situ. Optimal skin-DC targeting in combination with adequate adjuvant delivery facilitates DC maturation and migration to draining lymph nodes and enhances antigen cross-presentation and T cell priming. In this review we describe what DC subsets populate the human skin, as well as current vaccination strategies based on targeting strategies and alternative administration for the induction of robust long-lived anti-cancer effector T cells.

Novel engineered systems for oral, mucosal and transdermal drug delivery

Technological advances in drug discovery have resulted in increasing number of molecules including proteins and peptides as drug candidates. However, how to deliver drugs with satisfactory therapeutic effect, minimal side effects and increased patient compliance is a question posted before researchers, especially for those drugs with poor solubility, large molecular weight or instability. Microfabrication technology, polymer science and bioconjugate chemistry combine to address these problems and generate a number of novel engineered drug delivery systems. Injection routes usually have poor patient compliance due to their invasive nature and potential safety concerns over needle reuse. The alternative non-invasive routes, such as oral, mucosal (pulmonary, nasal, ocular, buccal, rectal, vaginal), and transdermal drug delivery have thus attracted many attentions. Here, we review the applications of the novel engineered systems for oral, mucosal and transdermal drug delivery.

Production of dissolvable microneedles using an atomised spray process: effect of microneedle composition on skin penetration

Dissolvable microneedles offer an attractive delivery system for transdermal drug and vaccine delivery. They are most commonly formed by filling a microneedle mold with liquid formulation using vacuum or centrifugation to overcome the constraints of surface tension and solution viscosity. Here, we demonstrate a novel microneedle fabrication method employing an atomised spray technique that minimises the effects of the liquid surface tension and viscosity when filling molds. This spray method was successfully used to fabricate dissolvable microneedles (DMN) from a wide range of sugars (trehalose, fructose and raffinose) and polymeric materials (polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, hydroxypropylmethylcellulose and sodium alginate). Fabrication by spraying produced microneedles with amorphous content using single sugar compositions. These microneedles displayed sharp tips and had complete fidelity to the master silicon template. Using a method to quantify the consistency of DMN penetration into different skin layers, we demonstrate that the material of construction significantly influenced the extent of skin penetration. We demonstrate that this spraying method can be adapted to produce novel laminate-layered as well as horizontally-layered DMN arrays. To our knowledge, this is the first report documenting the use of an atomising spray, at ambient, mild processing conditions, to create dissolvable microneedle arrays that can possess novel, laminate layering.

Sodium alginate microneedle arrays mediate the transdermal delivery of bovine serum albumin

Background

The “poke and release” strategy for the delivery of macromolecules using polymeric microneedle (MN) is of great importance because it eliminates microneedle reuse, the risks of biohazardous sharps and cross contamination, and it requires no special disposal mechanism. The main objective of this study was the determination of the stability and delivery of bovine serum albumin (BSA) that was transported across human skin via sodium alginate (SA) microneedle arrays (MNs) and SA needle free patches using two different analytical methods.

Methodology and Findings

The capability of two analytical methods, the bicinchoninic acid (BCA) assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), to precisely detect and quantify BSA within different types of polymeric MNs was assessed. The ex vivo protein release of BSA across dermatomed human abdominal skin from 10 w/w SA MNs was compared to that from needle-free patches using Franz diffusion cells. The developed applicator was mechanically characterized using a Texture Analyzer. The patch mold and its components were fabricated using a rapid prototyping machine.

Conclusions/Significance

The BCA method was able to precisely detect BSA that had been loaded into SA MNs. However, the use of SDS-PAGE as the analytical method resulted in significantly different amounts of BSA recovered from differently conditioned polymeric MNs. The permeation of BSA across dermatomed human abdominal skin by SA MNs, which were composed of 100 pyramidal needles, increased by approximately 15.4 fold compared to the permeation obtained with SA needle-free patches. The ease of use of the applicator during the release studies was also demonstrated, as was its mechanical characterization.

New directions in immunotherapy

Allergen immunotherapy (AIT) is effective in reducing the clinical symptoms associated with allergic rhinitis, asthma and venom-induced anaphylaxis. Subcutaneous (SCIT) and sublingual immunotherapy (SLIT) with unmodified allergen extracts are the most widely prescribed AIT regimens. The efficacy of these 2 routes appears comparable, but the safety profile with SLIT is more favorable allowing for home administration and requiring less patient time. However, both require that the treatment is taken regularly over several years, e.g., monthly in a supervised medical setting with SCIT and daily at home with SLIT. Despite the difference in treatment settings, poor adherence has been reported with both routes. Emerging evidence suggests that AIT may be effective in other allergic conditions such as atopic dermatitis, venom sting-induced large local reactions, and food allergy. Research with oral immunotherapy (OIT) for food allergies suggest that many patients can be desensitized during treatment, but questions remain about whether this can produce long term tolerance. Further studies are needed to identify appropriate patients and treatment regimens with these conditions. Efforts to develop safer and more effective AIT for inhalant allergies have led to investigations with modified allergens and alternate routes. Intralymphatic (ILIT) has been shown to produce long-lasting clinical benefits after three injections comparable to a 3-year course of SCIT. Epicutaneous (EPIT) has demonstrated promising results for food and inhalant allergies. Vaccine modifications, such as T cell epitopes or the use of viral-like particles as an adjuvant, have been shown to provide sustained clinical benefits after a relatively short course of treatment compared to the currently available AIT treatments, SLIT and SCIT. These newer approaches may increase the utilization and adherence to AIT because the multi-year treatment requirement of currently available AIT is a likely deterrent for initiating and adhering to treatment.

Polymer multilayer tattooing for enhanced DNA vaccination

DNA vaccines have many potential benefits but have failed to generate robust immune responses in humans. Recently, methods such as in vivo electroporation have demonstrated improved performance, but an optimal strategy for safe, reproducible, and pain-free DNA vaccination remains elusive. Here we report an approach for rapid implantation of vaccine-loaded polymer films carrying DNA, immune-stimulatory RNA, and biodegradable polycations into the immune-cell-rich epidermis, using microneedles coated with releasable polyelectrolyte multilayers. Films transferred into the skin following brief microneedle application promoted local transfection and controlled the persistence of DNA and adjuvants in the skin from days to weeks, with kinetics determined by the film composition. These 'multilayer tattoo' DNA vaccines induced immune responses against a model HIV antigen comparable to electroporation in mice, enhanced memory T-cell generation, and elicited 140-fold higher gene expression in non-human primate skin than intradermal DNA injection, indicating the potential of this strategy for enhancing DNA vaccination.

Development of vertical SU-8 microtubes integrated with dissolvable tips for transdermal drug delivery

Polymer-based microneedles have drawn much attention in the transdermal drug delivery resulting from their flexibility and biocompatibility. Traditional fabrication approach deploys various kinds of molds to create sharp tips at the end of needles for the penetration purpose. This approach is usually time-consuming and expensive. In this study, we developed an innovative fabrication process to make biocompatible SU-8 microtubes integrated with biodissolvable maltose tips as novel microneedles for the transdermal drug delivery applications. These microneedles can easily penetrate the skin's outer barrier represented by the stratum corneum (SC) layer. The drug delivery device of mironeedles array with 1000 μm spacing between adjacent microneedles is proven to be able to penetrate porcine cadaver skins successfully. The maximum loading force on the individual microneedle can be as large as 7.36 ± 0.48N. After 9 min of the penetration, all the maltose tips are dissolved in the tissue. Drugs can be further delivered via these open biocompatible SU-8 microtubes in a continuous flow manner. The permeation patterns caused by the solution containing Rhodamine 110 at different depths from skin surface were characterized via a confocal microscope. It shows successful implementation of the microneedle function for fabricated devices.

Skin dendritic cell targeting via microneedle arrays laden with antigen-encapsulated poly-D,L-lactide-co-glycolide nanoparticles induces efficient antitumor and antiviral immune responses

The efficacious delivery of antigens to antigen-presenting cells (APCs), in particular, to dendritic cells (DCs), and their subsequent activation remains a significant challenge in the development of effective vaccines. This study highlights the potential of dissolving microneedle (MN) arrays laden with nanoencapsulated antigen to increase vaccine immunogenicity by targeting antigen specifically to contiguous DC networks within the skin. Following in situ uptake, skin-resident DCs were able to deliver antigen-encapsulated poly-d,l-lactide-co-glycolide (PGLA) nanoparticles to cutaneous draining lymph nodes where they subsequently induced significant expansion of antigen-specific T cells. Moreover, we show that antigen-encapsulated nanoparticle vaccination via microneedles generated robust antigen-specific cellular immune responses in mice. This approach provided complete protection in vivo against both the development of antigen-expressing B16 melanoma tumors and a murine model of para-influenza, through the activation of antigen-specific cytotoxic CD8(+) T cells that resulted in efficient clearance of tumors and virus, respectively. In addition, we show promising findings that nanoencapsulation facilitates antigen retention into skin layers and provides antigen stability in microneedles. Therefore, the use of biodegradable polymeric nanoparticles for selective targeting of antigen to skin DC subsets through dissolvable MNs provides a promising technology for improved vaccination efficacy, compliance, and coverage.

Frontiers of transcutaneous vaccination systems: novel technologies and devices for vaccine delivery

Transcutaneous immunization (TCI) systems that use the skin's immune function are promising needle-free, easy-to-use, and low-invasive vaccination alternative to conventional, injectable vaccination methods. To develop effective TCI systems, it is essential to establish fundamental techniques and technologies that deliver antigenic proteins to antigen-presenting cells in the epidermis and dermis while overcoming the barrier function of the stratum corneum. In this review, we provide an outline of recent trends in the development of techniques for the delivery of antigenic proteins and of the technologies used to enhance TCI systems. We also introduce basic and clinical research involving our TCI systems that incorporate several original devices.

Enhanced transcutaneous immunization via dissolving microneedle array loaded with liposome encapsulated antigen and adjuvant

Transcutaneous immunization (TCI) with dissolving microneedle arrays (DMAs) is a promising vaccine administration method. In this work, we developed a TCI device consisting of dissolving polyvinylpyrrolidone (PVP) microneedles array, where in the tips are loaded with antigen and adjuvant encapsulated in liposomes. The microneedles could effectively be inserted into the skin and completely dissolve within 3 min. As a test-case, we selected ovalbumin (OVA) as a model antigen, CpG OND as adjuvant and cationic liposome (Lip) as a microparticulate vehicle for co-deliver antigens and adjuvant. Mice were immunized transcutaneously with DMAs containing OVA, OVA-CpG OND, OVA encapsulated in Lip, OVA-CpG OND encapsulated in Lip and conventional intramuscular injection (IM) with OVA solution, respectively. The results show that the anti-OVA IgG antibody level in the group immunized with the DMA containing OVA-CpG OND encapsulated in Lip was significantly higher than that of the other groups. Furthermore, it significantly increased the level of IgG2a (P<0.05) and achieved the shift of immune type from predominate Th2 type to a balance Th1/Th2 type. In conclusion, the DMA TCI device can effectively deliver the Lip encapsulating CpG OND-OVA into skin, enhancing the immune response and change the immune type.

Influenza subunit vaccine coated microneedle patches elicit comparable immune responses to intramuscular injection in guinea pigs

Delivery of influenza vaccine using innovative approaches such as microneedles has been researched extensively in the past decade. In this study we present concentration followed by formulation and coating of monobulks from 2008/2009 seasonal vaccine on to 3M's solid microstructured transdermal system (sMTS) by a GMP-scalable process. The hemagglutinin (HA) in monobulks was concentrated by tangential flow filtration (TFF) to achieve HA concentrations as high as 20mg/ml. The stability of the coated antigens was evaluated by the functional assay, single radial immunodiffusion (SRID). The data generated show stability of the coated antigen upon storage at 4°C and room temperature in the presence of desiccant for at least 8 weeks. Freeze-thaw stability data indicate the stability of the coated antigen in stressed conditions. The vaccine coated microstructures were evaluated in vivo in a guinea pig model, and resulted in immune titers comparable to the traditional trivalent vaccine administered intramuscularly. The data presented indicate the potential use of the technology in delivery of influenza vaccine. This paper also addresses the key issues of stability of coated antigen, reproducibility and scalability of the processes used in preparation of influenza vaccine coated microneedle patches that are important in developing a successful product.

Langerin negative dendritic cells promote potent CD8+ T-cell priming by skin delivery of live adenovirus vaccine microneedle arrays

Stabilization of virus protein structure and nucleic acid integrity is challenging yet essential to preserve the transcriptional competence of live recombinant viral vaccine vectors in the absence of a cold chain. When coupled with needle-free skin delivery, such a platform would address an unmet need in global vaccine coverage against HIV and other global pathogens. Herein, we show that a simple dissolvable microneedle array (MA) delivery system preserves the immunogenicity of vaccines encoded by live recombinant human adenovirus type 5 (rAdHu5). Specifically, dried rAdHu5 MA immunization induced CD8(+) T-cell expansion and multifunctional cytokine responses equipotent with conventional injectable routes of immunization. Intravital imaging demonstrated MA cargo distributed both in the epidermis and dermis, with acquisition by CD11c(+) dendritic cells (DCs) in the dermis. The MA immunizing properties were attributable to CD11c(+) MHCII(hi) CD8α(neg) epithelial cell adhesion molecule (EpCAM(neg)) CD11b(+) langerin (Lang; CD207)(neg) DCs, but neither Langerhans cells nor Lang(+) DCs were required for CD8(+) T-cell priming. This study demonstrates an important technical advance for viral vaccine vectors progressing to the clinic and provides insights into the mechanism of CD8(+) T-cell priming by live rAdHu5 MAs.

Fully embeddable chitosan microneedles as a sustained release depot for intradermal vaccination

This study introduces a microneedle transdermal delivery system, composed of embeddable chitosan microneedles and a poly(L-lactide-co-D,L-lactide) (PLA) supporting array, for complete and sustained delivery of encapsulated antigens to the skin. Chitosan microneedles were mounted to the top of a strong PLA supporting array, providing mechanical strength to fully insert the microneedles into the skin. When inserted into rat skin in vivo, chitosan microneedles successfully separated from the supporting array and were left within the skin for sustained drug delivery without requiring a transdermal patch. The microneedle penetration depth was approximately 600 μm (i.e. the total length of the microneedle), which is beneficial for targeted delivery of antigens to antigen-presenting cells in the epidermis and dermis. To evaluate the utility of chitosan microneedles for intradermal vaccination, ovalbumin (OVA; MW = 44.3 kDa) was used as a model antigen. When the OVA-loaded microneedles were embedded in rat skin in vivo, histological examination showed that the microneedles gradually degraded and prolonged OVA exposure at the insertion sites for up to 14 days. Compared to traditional intramuscular immunization, rats immunized by a single microneedle dose of OVA showed a significantly higher OVA-specific antibody response which lasted for at least 6 weeks. These results suggest that embeddable chitosan microneedles are a promising depot for extended delivery of encapsulated antigens to provide sustained immune stimulation and improve immunogenicity.

Factors influencing the efficacy of two injections of a pandemic 2009 influenza A (H1N1) nonadjuvanted vaccine in systemic lupus erythematosus

OBJECTIVE

To assess the factors influencing the efficacy of 2 injections of a pandemic 2009 influenza A (H1N1) vaccine in patients with systemic lupus erythematosus (SLE).

METHODS

We conducted a single-center, observational prospective study of 111 patients who were vaccinated with a monovalent, inactivated, nonadjuvanted, split-virus vaccine during December 2009 and January 2010 and received a second dose of vaccine 3 weeks later. The antibody response was evaluated using the hemagglutination inhibition assay according to the guidelines recommended for the pandemic vaccine, consisting of 3 immunogenicity criteria (i.e., a seroprotection rate of 70%, a seroconversion rate of 40%, and a geometric mean ratio [GMR] of 2.5).

RESULTS

The 3 immunogenicity criteria were met on day 42 (seroprotection rate 80.0% [95% confidence interval (95% CI) 72.5-87.5%], seroconversion rate 71.8% [95% CI 63.4-80.2%], and GMR 10.3 [95% CI 2.9-14.2]), while only 2 criteria were met on day 21 (seroprotection rate 66.7% [95% CI 57.9-75.4%], seroconversion rate 60.4% [95% CI 51.3-69.5%], and GMR 8.5 [95% CI 3.2-12.0]). The vaccine was well tolerated. Disease activity, assessed by the Safety of Estrogens in Lupus Erythematosus National Assessment version of the SLE Disease Activity Index, the British Isles Lupus Assessment Group score, and the Systemic Lupus Activity Questionnaire, did not increase. In the multivariate analysis, vaccination failure was significantly associated with immunosuppressive treatment or a lymphocyte count of ≤ 1.0 × 10⁹/liter. The second injection significantly increased the immunogenicity in these subgroups, but not high enough to fulfill the seroprotection criterion in patients receiving immunosuppressive treatment.

CONCLUSION

Our findings indicate that the efficacy of the vaccine was impaired in patients who were receiving immunosuppressive drugs or who had lymphopenia. A second injection increased vaccine immunogenicity without reaching all efficacy criteria for a pandemic vaccine in patients receiving an immunosuppressive agent. These results open possibilities for improving anti-influenza vaccination in SLE.

Transcutaneous vaccines--current and emerging strategies

INTRODUCTION

Vaccination, which is the major fundamental prophylaxis against illness and death from infectious disease, has greatly contributed to the global improvement of human health. However, the disadvantages of conventional injection systems hamper the delivery of vaccination technologies to developing countries. The imminent practice of easy-to-use vaccination methods is expected to overcome certain issues associated with injectable vaccinations. One innovative method is the transcutaneous immunization (TCI) system.

AREAS COVERED

Two major strategies for TCI are discussed in this review. One is to promote antigen permeation of the skin barrier by patch systems or nanoparticles. The other is the delivery of antigens into the skin by electroporation and microneedles in order to physically overcome the skin barrier. Moreover, adjuvant development for TCI is discussed.

EXPERT OPINION

Many different approaches have been developed for TCI, which have the potential to be effective, easy-to-use and painless methods of vaccination. However, in practical terms, the guidelines concerning the manufacturing processes and clinical trial evaluation of the procedures have not kept pace with the development of these novel formulations. The accumulation of information regarding skin characteristics and the properties of TCI devices will help refine TCI system development guidelines and thus lead to the improvement of transcutaneous vaccination.

Composite dissolving microneedles for coordinated control of antigen and adjuvant delivery kinetics in transcutaneous vaccination

Transcutaneous administration has the potential to improve therapeutics delivery, providing an approach that is safer and more convenient than traditional alternatives, while offering the opportunity for improved therapeutic efficacy through sustained/controlled drug release. To this end, we demonstrate a microneedle materials platform for rapid implantation of controlled-release polymer depots into the cutaneous tissue. Arrays of microneedles comprised of drug-loaded poly(lactide-co-glycolide) (PLGA) microparticles or solid PLGA tips were prepared with a supporting and rapidly water-soluble poly(acrylic acid) (PAA) matrix. Upon application of microneedle patches to the skin of mice, the microneedles perforated the stratum corneum and epidermis. Penetration of the outer skin layers was followed by rapid dissolution of the PAA binder on contact with the interstitial fluid of the epidermis, implanting the microparticles or solid polymer microneedles in the tissue, which were retained following patch removal. These polymer depots remained in the skin for weeks following application and sustained the release of encapsulated cargos for systemic delivery. To show the utility of this approach we demonstrated the ability of these composite microneedle arrays to deliver a subunit vaccine formulation. In comparison to traditional needle-based vaccination, microneedle delivery gave improved cellular immunity and equivalent generation of serum antibodies, suggesting the potential of this approach for vaccine delivery. However, the flexibility of this system should allow for improved therapeutic delivery in a variety of diverse contexts.

Development of vertical SU-8 microneedles for transdermal drug delivery by double drawing lithography technology

Polymer-based microneedles have drawn much attention in transdermal drug delivery resulting from their flexibility and biocompatibility. Traditional fabrication approaches are usually time-consuming and expensive. In this study, we developed a new double drawing lithography technology to make biocompatible SU-8 microneedles for transdermal drug delivery applications. These microneedles are strong enough to stand force from both vertical direction and planar direction during penetration. They can be used to penetrate into the skin easily and deliver drugs to the tissues under it. By controlling the delivery speed lower than 2 μl/min per single microneedle, the delivery rate can be as high as 71%.

Targeting the skin for microneedle delivery of influenza vaccine

Influenza infection represents a major socioeconomic burden worldwide. Skin represents a new target that has gained much attention in recent years for delivery of influenza vaccine as an alternative to the conventional intramuscular route of immunization. In this review we describe different microneedle vaccination approaches used in vivo, including metal and dissolving microneedle patches that have demonstrated promising results. Additionally we analyze the immunological basis for microneedle skin immunization and targeting of the skin's dense population of antigen presenting cells, their role, characterization, and function. Additionally we analyze the importance of inflammatory signaling in the skin after microneedle delivery.

Complexes of streptavidin-fused antigens with biotinylated antibodies targeting receptors on dendritic cell surface: a novel tool for induction of specific T-cell immune responses

The choice of tools that enable efficient targeting of exogenous antigens (Ag) for processing and presentation by professional Ag-presenting cells (APC) remains limited. This represents, indeed, a bottleneck in development of vaccines inducing specific T-cell responses. Here, we describe a novel strategy of Ag delivery into APCs. The Ag of choice is fused to the N- or C-terminus of streptavidin (SA) and tetrameric Ag-SA or SA-Ag fusion proteins are produced in E. coli and purified by 2-Iminobiotin-Agarose affinity chromatography. Alternatively, Ag-SA proteins are purified from urea extracts of E. coli inclusion bodies and refolded in vitro into functional tetramers. Complexes with biotinylated antibodies targeting cell surface receptors are formed and used to deliver the Ags of choice for processing and presentation by APCs and induction of Ag-specific CD4+ and CD8+ T-cell responses in vitro and in vivo.

[Vaccination and French community pharmacists: from innovative actions to innovative organisations?]

The situation report of vaccination in France and a methodology of vaccination suggests that some vaccines may opportunely be injected in the pharmacy where and when the relevant vaccine is dispensed. Vaccination by pharmacist could hence mean dispensation, traced administration and documented follow-up. This perspective requires the normative framework, information systems and vocational training to be somewhat adapted, and financial incentives to be aligned. The challenges are cultural and organisational. Pharmacist's optional implication along with the prescriptor would have a major interest in terms of individual protection and cost-effectiveness of public health strategies. It would allow to release and to value medical and nursing time for the benefit of patients. Thanks to gain-sharing organizations, healthcare providers could explore dynamic cooperation.

Polymer microneedles for transdermal drug delivery

A microneedle system has been developed to deliver chemical and biological agents through the stratum corneum, which is the main barrier to drug delivery. Recently, microneedles have been fabricated from various kinds of polymers, including biocompatible polymer, biodegradable polymer, and water-soluble polymer. Polymer microneedles offer the benefits of ease of fabrication, cost-effectiveness, and mass production, as well as controlled drug release using the water solubility and degradation properties of polymer. In this review, the key features of polymer microneedles are discussed, including fabrication, materials, mechanical properties, drug delivery properties, and applications. Polymer microneedles provide a promising method for transdermal drug delivery by utilizing various physical and chemical properties of polymer.

Reservoir-based drug delivery systems utilizing microtechnology

This review covers reservoir-based drug delivery systems that incorporate microtechnology, with an emphasis on oral, dermal, and implantable systems. Key features of each technology are highlighted such as working principles, fabrication methods, dimensional constraints, and performance criteria. Reservoir-based systems include a subset of microfabricated drug delivery systems and provide unique advantages. Reservoirs, whether external to the body or implanted, provide a well-controlled environment for a drug formulation, allowing increased drug stability and prolonged delivery times. Reservoir systems have the flexibility to accommodate various delivery schemes, including zero order, pulsatile, and on demand dosing, as opposed to a standard sustained release profile. Furthermore, the development of reservoir-based systems for targeted delivery for difficult to treat applications (e.g., ocular) has resulted in potential platforms for patient therapy.

Microneedles for drug and vaccine delivery

Microneedles were first conceptualized for drug delivery many decades ago, but only became the subject of significant research starting in the mid-1990's when microfabrication technology enabled their manufacture as (i) solid microneedles for skin pretreatment to increase skin permeability, (ii) microneedles coated with drug that dissolves off in the skin, (iii) polymer microneedles that encapsulate drug and fully dissolve in the skin and (iv) hollow microneedles for drug infusion into the skin. As shown in more than 350 papers now published in the field, microneedles have been used to deliver a broad range of different low molecular weight drugs, biotherapeutics and vaccines, including published human studies with a number of small-molecule and protein drugs and vaccines. Influenza vaccination using a hollow microneedle is in widespread clinical use and a number of solid microneedle products are sold for cosmetic purposes. In addition to applications in the skin, microneedles have also been adapted for delivery of bioactives into the eye and into cells. Successful application of microneedles depends on device function that facilitates microneedle insertion and possible infusion into skin, skin recovery after microneedle removal, and drug stability during manufacturing, storage and delivery, and on patient outcomes, including lack of pain, skin irritation and skin infection, in addition to drug efficacy and safety. Building off a strong technology base and multiple demonstrations of successful drug delivery, microneedles are poised to advance further into clinical practice to enable better pharmaceutical therapies, vaccination and other applications.

Self-folding polymeric containers for encapsulation and delivery of drugs

Self-folding broadly refers to self-assembly processes wherein thin films or interconnected planar templates curve, roll-up or fold into three dimensional (3D) structures such as cylindrical tubes, spirals, corrugated sheets or polyhedra. The process has been demonstrated with metallic, semiconducting and polymeric films and has been used to curve tubes with diameters as small as 2nm and fold polyhedra as small as 100nm, with a surface patterning resolution of 15nm. Self-folding methods are important for drug delivery applications since they provide a means to realize 3D, biocompatible, all-polymeric containers with well-tailored composition, size, shape, wall thickness, porosity, surface patterns and chemistry. Self-folding is also a highly parallel process, and it is possible to encapsulate or self-load therapeutic cargo during assembly. A variety of therapeutic cargos such as small molecules, peptides, proteins, bacteria, fungi and mammalian cells have been encapsulated in self-folded polymeric containers. In this review, we focus on self-folding of all-polymeric containers. We discuss the mechanistic aspects of self-folding of polymeric containers driven by differential stresses or surface tension forces, the applications of self-folding polymers in drug delivery and we outline future challenges.

Polymeric microdevices for transdermal and subcutaneous drug delivery

Low cost manufacturing of polymeric microdevices for transdermal and subcutaneous drug delivery is slated to have a major impact on next generation devices for administration of biopharmaceuticals and other emerging new formulations. These devices range in complexity from simple microneedle arrays to more complicated systems incorporating micropumps, micro-reservoirs, on-board sensors, and electronic intelligence. In this paper, we review devices currently in the market and those in the earlier stages of research and development. We also present two examples of the research in our laboratory towards using phase change liquids in polymeric structures to create disposable micropumps and the development of an elastomeric reservoir for MEMS-based transdermal drug delivery systems.

Recent trends in vaccine delivery systems: A review

Vaccines are the preparations given to patients to evoke immune responses leading to the production of antibodies (humoral) or cell-mediated responses that will combat infectious agents or noninfectious conditions such as malignancies. Alarming safety profile of live vaccines, weak immunogenicity of sub-unit vaccines and immunization, failure due to poor patient compliance to booster doses which should potentiate prime doses are few strong reasons, which necessitated the development of new generation of prophylactic and therapeutic vaccines to promote effective immunization. Attempts are being made to deliver vaccines through carriers as they control the spatial and temporal presentation of antigens to immune system thus leading to their sustained release and targeting. Hence, lower doses of weak immunogens can be effectively directed to stimulate immune responses and eliminate the need for the administration of prime and booster doses as a part of conventional vaccination regimen. This paper reviews carrier systems such as liposomes, microspheres, nanoparticles, dendrimers, micellar systems, ISCOMs, plant-derived viruses which are now being investigated and developed as vaccine delivery systems. This paper also describes various aspects of "needle-free technologies" used to administer the vaccine delivery systems through different routes into the human body.

Microneedle and mucosal delivery of influenza vaccines

In recent years with the threat of pandemic influenza and other public health needs, alternative vaccination methods other than intramuscular immunization have received great attention. The skin and mucosal surfaces are attractive sites probably because of both noninvasive access to the vaccine delivery and unique immunological responses. Intradermal vaccines using a microinjection system (BD Soluvia(TM)) and intranasal vaccines (FluMist®) are licensed. As a new vaccination method, solid microneedles have been developed using a simple device that may be suitable for self-administration. Because coated microneedle influenza vaccines are administered in the solid state, developing formulations maintaining the stability of influenza vaccines is an important issue to be considered. Marketable microneedle devices and clinical trials remain to be developed. Other alternative mucosal routes such as oral and intranasal delivery systems are also attractive for inducing cross-protective mucosal immunity, but effective non-live mucosal vaccines remain to be developed.

Measles vaccination using a microneedle patch

Measles vaccination programs would benefit from delivery methods that decrease cost, simplify logistics, and increase safety. Conventional subcutaneous injection is limited by the need for skilled healthcare professionals to reconstitute and administer injections, and by the need for safe needle handling and disposal to reduce the risk of disease transmission through needle re-use and needlestick injury. Microneedles are micron-scale, solid needles coated with a dry formulation of vaccine that dissolves in the skin within minutes after patch application. By avoiding the use of hypodermic needles, vaccination using a microneedle patch could be carried out by minimally trained personnel with reduced risk of blood-borne disease transmission. The goal of this study was to evaluate measles vaccination using a microneedle patch to address some of the limitations of subcutaneous injection. Viability of vaccine virus dried onto a microneedle patch was stabilized by incorporation of the sugar, trehalose, and loss of viral titer was less than 1 log10(TCID50) after storage for at least 30 days at room temperature. Microneedle patches were then used to immunize cotton rats with the Edmonston-Zagreb measles vaccine strain. Vaccination using microneedles at doses equaling the standard human dose or one-fifth the human dose generated neutralizing antibody levels equivalent to those of a subcutaneous immunization at the same dose. These results show that measles vaccine can be stabilized on microneedles and that vaccine efficiently reconstitutes in vivo to generate a neutralizing antibody response equivalent to that generated by subcutaneous injection.

New routes for allergen immunotherapy

IgE-mediated allergy is a highly prevalent disease in the industrialized world. Allergen-specific immunotherapy (SIT) should be the preferred treatment, as it has long lasting protective effects and can stop the progression of the disease. However, few allergic patients choose to undergo SIT, due to the long treatment time and potential allergic adverse events. Since the beneficial effects of SIT are mediated by antigen presenting cells inducing Th1, Treg and antibody responses, whereas the adverse events are caused by mast cells and basophils, the therapeutic window of SIT may be widened by targeting tissues rich in antigen presenting cells. Lymph nodes and the epidermis contain high density of dendritic cells and low numbers of mast cells and basophils. The epidermis has the added benefit of not being vascularised thereby reducing the chances of anaphylactic shock due to leakage of allergen. Hence, both these tissues represent highly promising routes for SIT and are the focus of discussion in this review.

Releasable layer-by-layer assembly of stabilized lipid nanocapsules on microneedles for enhanced transcutaneous vaccine delivery

Here we introduce a new approach for transcutaneous drug delivery, using microneedles coated with stabilized lipid nanocapsules, for delivery of a model vaccine formulation. Poly(lactide-co-glycolide) microneedle arrays were coated with multilayer films via layer-by-layer assembly of a biodegradable cationic poly(β-amino ester) (PBAE) and negatively charged interbilayer-cross-linked multilamellar lipid vesicles (ICMVs). To test the potential of these nanocapsule-coated microneedles for vaccine delivery, we loaded ICMVs with a protein antigen and the molecular adjuvant monophosphoryl lipid A. Following application of microneedle arrays to the skin of mice for 5 min, (PBAE/ICMV) films were rapidly transferred from microneedle surfaces into the cutaneous tissue and remained in the skin following removal of the microneedle arrays. Multilayer films implanted in the skin dispersed ICMV cargos in the treated tissue over the course of 24 h in vivo, allowing for uptake of the lipid nanocapsules by antigen presenting cells in the local tissue and triggering their activation in situ. Microneedle-mediated transcutaneous vaccination with ICMV-carrying multilayers promoted robust antigen-specific humoral immune responses with a balanced generation of multiple IgG isotypes, whereas bolus delivery of soluble or vesicle-loaded antigen via intradermal injection or transcutaneous vaccination with microneedles encapsulating soluble protein elicited weak, IgG(1)-biased humoral immune responses. These results highlight the potential of lipid nanocapsules delivered by microneedles as a promising platform for noninvasive vaccine delivery applications.

Microneedle mediated intradermal delivery of adjuvanted recombinant HIV-1 CN54gp140 effectively primes mucosal boost inoculations

Dissolving polymeric microneedle arrays formulated to contain recombinant CN54 HIVgp140 and the TLR4 agonist adjuvant MPLA were assessed for their ability to elicit antigen-specific immunity. Using this novel microneedle system we successfully primed antigen-specific responses that were further boosted by an intranasal mucosal inoculation to elicit significant antigen-specific immunity. This prime-boost modality generated similar serum and mucosal gp140-specific IgG levels to the adjuvanted and systemic subcutaneous inoculations. While the microneedle primed groups demonstrated a balanced Th1/Th2 profile, strong Th2 polarization was observed in the subcutaneous inoculation group, likely due to the high level of IL-5 secretion from cells in this group. Significantly, the animals that received a microneedle prime and intranasal boost regimen elicited a high level IgA response in both the serum and mucosa, which was greatly enhanced over the subcutaneous group. The splenocytes from this inoculation group secreted moderate levels of IL-5 and IL-10 as well as high amounts of IL-2, cytokines known to act in synergy to induce IgA. This work opens up the possibility for microneedle-based HIV vaccination strategies that, once fully developed, will greatly reduce risk for vaccinators and patients, with those in the developing world set to benefit most.