Effects of experimental increase in insulin-like growth factor 1 on feather growth rate, moult intensity and feather quality in a passerine bird.

Moulting is a crucial, yet often overlooked life-history stage in many animals, when they renew their integumental structures. This life-history stage is an energetically demanding somatic growth event that has particular importance in birds because feathers play a crucial role in flight, insulation and communication. Somatic growth processes are regulated by the evolutionarily conserved peptide hormone insulin-like growth factor 1 (IGF-1). However, the role of IGF-1 in feather growth remains unknown. In this study, we captured 41 juvenile free-living bearded reedlings (Panurus biarmicus) that had started their first complete moult and brought them into captivity. Then, we manipulated their circulating IGF-1 levels using poly-(lactic-co-glycolid acid) microparticles (microspheres) that provide a sustained release of IGF-1. The treatment increased IGF-1 levels but did not affect the feather growth rate. However, 2 weeks after the treatment, birds in the increased IGF-1 group were moulting more feathers simultaneously than the controls and were at a more advanced stage of moult. Birds with experimentally increased IGF-1 levels had better quality feathers (measured by a lower number of fault bars) than the controls. These results suggest that an increase in IGF-1 does not speed up feather growth, but may alter moult intensity by initiating the renewal of several feathers simultaneously. This may shorten the overall moulting time but may imply costs in terms of IGF-1-induced oxidative stress.

Photosensitizer and Light Pave the Way for Cytosolic Targeting and Generation of Cytosolic CD8 T Cells Using PLGA Vaccine Particles.

The generation of CTLs is crucial in the immunological fight against cancer and many infectious diseases. To achieve this, vaccine Ags need to be targeted to the cytosol of dendritic cells, which can activate CD8 T cells via MHC class I (MHCI). Therefore, such targeting has become one of the major objectives of vaccine research. In this study, we aimed to bypass the unwanted and default MHC class II Ag presentation and trigger MHCI presentation by using a photosensitizer that, upon light activation, would facilitate cytosolic targeting of codelivered Ag. Poly(lactide-co-glycolide) microparticles ∼1 µm size were loaded with OVA and the photosensitizer tetraphenyl chlorine disulphonate (TPCS2a) and administered intradermally in mice, which were illuminated 1 d later for activation of the photosensitizer. Immunization in the presence of TPCS2a significantly increased activation of CD8 T cells compared with immunization without TPCS2a and as measured by CD8 T cell proliferation, production of proinflammatory IFN-γ, TNF-α, and IL-2, and prevention of tumor growth. Cytotoxicity was demonstrated by granzyme B production in vitro and by in vivo killing of CFSE-labeled targets. CD4-dependent Ab responses were abrogated in mice immunized with TPCS2a-containing particles, suggesting that photosensitization facilitated a shift from default MHC class II toward MHCI Ag presentation. Hence, vaccine particles with Ag and photosensitizers proved an effective vehicle or adjuvant for stimulation of CTLs, and they may find potential application in therapeutic cancer vaccination and in prophylactic and therapeutic vaccination against intracellular infections.

Cytosolic Delivery of Liposomal Vaccines by Means of the Concomitant Photosensitization of Phagosomes.

One of the greatest pharmaceutical challenges in vaccinology is the delivery of antigens to the cytosol of antigen-presenting cells (APCs) in order to allow for the stimulation of major histocompatibility complex (MHC) class I-restricted CD8(+) T-cell responses, which may act on intracellular infections or cancer. Recently, we described a novel method for cytotoxic T-lymphocyte (CTL) vaccination by combining antigens with a photosensitizer and light for cytosolic antigen delivery. The goal of the current project was to test this immunization method with particle-based formulations. Liposomes were prepared from dipalmitoylphosphatidylcholine and cholesterol, and the antigen ovalbumin (OVA) or the photosensitizer tetraphenyl chlorine disulfonate (TPCS2a) was separately encapsulated. C57BL/6 mice were immunized intradermally with OVA liposomes or a combination of OVA and TPCS2a liposomes, and light was applied the next day for activation of the photosensitizer resulting in cytosolic release of antigen from phagosomes. Immune responses were tested both after a prime only regime and after a prime-boost scheme with a repeat immunization 2 weeks post priming. Antigen-specific CD8(+) T-cell responses and antibody responses were analyzed ex vivo by flow cytometry and ELISA methods. The physicochemical stability of liposomes upon storage and light exposure was analyzed in vitro. Immunization with both TPCS2a- and OVA-containing liposomes greatly improved CD8(+) T-cell responses as compared to immunization without TPCS2a and as measured by proliferation in vivo and cytokine secretion ex vivo. In contrast, OVA-specific antibody responses (IgG1 and IgG2c) were reduced after immunization with TPCS2a-containing liposomes. The liposomal formulation protected the photosensitizer from light-induced inactivation during storage. In conclusion, the photosensitizer TPCS2a was successfully formulated in liposomes and enabled a shift from MHC class II to MHC class I antigen processing and presentation for stimulation of strong CD8(+) T-cell responses. Therefore, photosensitive particulate vaccines may have the potential to add to current vaccine practice a new method of vaccination that, as opposed to current vaccines, can stimulate strong CD8(+) T-cell responses.

Simultaneous quantification of polymeric and surface active stabilizers of nanosuspensions by using near-infrared spectroscopy.

Nanosuspension technology is an attractive approach for the formulation and solubility enhancement of poorly water-soluble drug compounds. The technology requires adequate excipients for stabilizing the suspensions during nanogrinding and storage. This study aimed at establishing a near-infrared (NIR) method for assaying simultaneously the two nanoparticle stabilizers, sodium dodecyl sulphate (SDS) and hydroxypropylcellulose (HPC), in miconazole nanosuspensions. Second derivative of NIR signals was used to establish calibration curves in concentration ranges of interest of SDS (0.03-0.3%) and HPC (0.75-7.5%). The suitability and applicability of the NIR method was verified by evaluating the linearity, accuracy, precision, and specificity of the obtained data. The method was then used to quantify indirectly the amount of SDS and HPC adsorbed onto miconazole nanoparticles. Within the concentration range of interest, SDS adsorption increased up to 122 µg/m(2) (4.2 × 10(-7) mol/m(2)) with increasing SDS concentration, and HPC adsorption was in the range of 800-1000 µg/m(2) (21-27 × 10(-7) mol/m(2)) for nanosuspensions containing nominally 5% HPC and 12.5% or 20% miconazole. Interestingly, some of the adsorbed HPC was displaced upon increase of SDS concentration and adsorption. The data were also confirmed by surface tension measurements of aqueous solutions of SDS and HPC and nanosuspension supernatants. The availability of a fast and nondestructive method for quantifying simultaneously the adsorption of two stabilizers onto nanoground particles may not only speed up nanosuspension development, but also provide insight into the mechanisms of nanoparticle stabilization regarding competitive adsorption and electrostatic versus steric stabilization.

Tumor eradication by immunotherapy with biodegradable PLGA microspheres--an alternative to incomplete Freund's adjuvant.

In experimental tumor immunotherapy, incomplete Freund's adjuvant (IFA) has been considered as the "gold standard" for T-cell vaccination in mice and humans in spite of its considerable adverse effects. Recently, we succeeded in eliciting strong CTL responses in mice after vaccination with biodegradable poly(D,L-lactide-co-glycolide) (PLGA) microspheres (MS). In our study, we compared the immune response to IFA and PLGA-MS containing ovalbumin (OVA) and CpG-oligodeoxynucleotide (MS-OVA/CpG) or we used a mixture of MS-OVA/CpG and MS-polyI:C. A single vaccination with MS-OVA/CpG elicited long-lasting titers of IgG1 and IgG2a, but only low IgE titers, and also the T-cell response was biased toward Th(1) differentiation. Antigen presentation to CD4(+) and CD8(+) cells and activation of a cytotoxic T-cell response in mice vaccinated with PLGA-MS and IFA lasted for over 3 weeks. Preconditioning of the injection site with TNF-α and heterologous prime-boost regimen further enhanced the cytotoxic response. PLGA-MS were as efficient or superior to IFA in eradication of preexisting tumors and suppression of lung metastases. Taken together, PLGA-MS are well-defined, biodegradable and clinically compatible antigen carrier systems that compare favorably with IFA in their efficacy of tumor immunotherapy in mouse models and hence deserve to be tested for their effectiveness against human malignant diseases.

PLGA-particle vaccine carrying TLR3/RIG-I ligand Riboxxim synergizes with immune checkpoint blockade for effective anti-cancer immunotherapy.

With emerging supremacy, cancer immunotherapy has evolved as a promising therapeutic modality compared to conventional antitumor therapies. Cancer immunotherapy composed of biodegradable poly(lactic-co-glycolic acid) (PLGA) particles containing antigens and toll-like receptor ligands induces vigorous antitumor immune responses in vivo. Here, we demonstrate the supreme adjuvant effect of the recently developed and pharmaceutically defined double-stranded (ds)RNA adjuvant Riboxxim especially when incorporated into PLGA particles. Encapsulation of Riboxxim together with antigens potently activates murine and human dendritic cells, and elevated tumor-specific CD8+ T cell responses are superior to those obtained using classical dsRNA analogues. This PLGA particle vaccine affords primary tumor growth retardation, prevention of metastases, and prolonged survival in preclinical tumor models. Its advantageous therapeutic potency was further enhanced by immune checkpoint blockade that resulted in reinvigoration of cytotoxic T lymphocyte responses and tumor ablation. Thus, combining immune checkpoint blockade with immunotherapy based on Riboxxim-bearing PLGA particles strongly increases its efficacy.

Photochemical internalization (PCI)-mediated activation of CD8 T cells involves antigen uptake and CCR7-mediated transport by migratory dendritic cells to draining lymph nodes.

Antigen cross-presentation to cytotoxic CD8+ T cells is crucial for the induction of anti-tumor and anti-viral immune responses. Recently, co-encapsulation of photosensitizers and antigens into microspheres and subsequent photochemical internalization (PCI) of antigens in antigen presenting cells has emerged as a promising new strategy for inducing antigen-specific CD8+ T cell responses in vitro and in vivo. However, the exact cellular mechanisms have hardly been investigated in vivo, i.e., which cell types take up antigen-loaded microspheres at the site of injection, or in which secondary lymphoid organ does T cell priming occur? We used spray-dried poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with ovalbumin and the photosensitizer tetraphenyl chlorine disulfonate (TPCS2a) to investigate these processes in vivo. Intravital microscopy and flow cytometric analysis of the murine ear skin revealed that dendritic cells (DCs) take up PLGA microspheres in peripheral tissues. Illumination then caused photoactivation of TPCS2a and induced local tissue inflammation that enhanced CCR7-dependent migration of microsphere-containing DCs to tissue-draining lymph nodes (LNs), i.e., the site of CD8+ T cell priming. The results contribute to a better understanding of the functional mechanism of PCI-mediated vaccination and highlight the importance of an active transport of vaccine microspheres by antigen presenting cells to draining LNs.

Schwann cell delivery of neurotrophic factors for peripheral nerve regeneration.

Current treatments of injured peripheral nerves often fail to mediate satisfactory functional recovery. For axonal regeneration, neurotrophic factors (NTFs) play a crucial role. Multiple NTFs and other growth-promoting factors are secreted, amongst others, by Schwann cells (SCs), which also provide cellular guidance for regenerating axons. Therefore, delivery of NTFs and transplantation of autologous or genetically modified SCs with therapeutic protein expression have been proposed. This article reviews polymer-based and cellular approaches for NTF delivery, with a focus on SCs and strategies to modulate SC gene expression. Polymer-based NTF delivery has mostly resided on nerve conduits (NC). While NC have generally provided prolonged NTF release, their therapeutic effect has remained significantly below that achieved with autologous nerve grafts. Several studies demonstrated enhanced nerve regeneration using NC seeded with SCs. The SCs have sometimes been modified genetically using non-viral or viral vectors. Whereas non-viral vectors produced poor transgene delivery, adenoviral vectors mediated high transgene transduction efficiency of SCs. Further improvements of safety and transgene expression of adenoviral vector may lead to rapid translation of pre-clinical research to clinical trials.

Combined Photosensitization and Vaccination Enable CD8 T-Cell Immunity and Tumor Suppression Independent of CD4 T-Cell Help.

Cytotoxic T lymphocytes (CTLs) are key players in fighting cancer, and their induction is a major focus in the design of therapeutic vaccines. Yet, therapeutic vaccine efficacy is limited, in part due to the suboptimal vaccine processing by antigen-presenting cells (APCs). Such processing typically takes place via the MHC class II pathway for CD4 T-cell activation and MHC class I pathway for activation of CD8 CTLs. We show that a combination of skin photochemical treatment and immunization, so-called photochemical internalization (PCI) facilitated CTL activation due to the photochemical adjuvant effect induced by photosensitizer, oxygen, and light. Mice were immunized intradermally with antigen and photosensitizer, followed by controlled light exposure. PCI-treated mice showed strong activation of CD8 T cells, with improved IFN-γ production and cytotoxicity, as compared to mice immunized without parallel PCI treatment. Surprisingly, the CD8 T-cell effector functions were not impaired in MHC class II- or CD4 T-cell-deficient mice. Moreover, PCI-based vaccination caused tumor regression independent of MHC class II or CD4 T cells presence in melanoma bearing mice. Together, the data demonstrate that PCI can act as a powerful adjuvant in cancer vaccines, even in hosts with impaired T-helper functions.

In vitro cell compatibility and antibacterial activity of microencapsulated doxycycline designed for improved localized therapy of septic arthritis.

OBJECTIVES: For the treatment of septic arthritis in large animals, the local application of antibiotics as a slow release system may be an appropriate means to reach high local bioactivity and low systemic side effects and drug residues. In this study, doxycycline microspheres were developed and tested in vitro for their drug-release properties, suitability for intra-articular application and antimicrobial activity. METHODS: The development of a slow release system was achieved by microencapsulation of the drug into poly(lactide-co-glycolide) microspheres by a novel ultrasonic atomization method. Drug elution was evaluated from microspheres dispersed in elution medium at pre-defined time points by HPLC. Joint-tissue compatibility was tested on cultured bovine synoviocytes by evaluating the expression of pro-inflammatory cytokine mRNA and the production of nitric oxide (NO). Finally, the antimicrobial activity of the released antibiotic was assessed with gram-negative and gram-positive bacteria exposed to release medium sampled at days 1, 7 and 12 after microsphere suspension. RESULTS: An adequate size of the microspheres, sufficient stabilization of doxycycline in aqueous environment and drug release (25 mg microspheres in 4 mL medium) above MIC for bacteria usually isolated in bovine and equine joints were obtained over 15 days. Although the cytokine mRNA expression reflected the excellent tissue compatibility, the results with NO yielded contradictory results. Antimicrobial tests of the release medium proved to match perfectly the activity of non-encapsulated, free doxycycline as reported in the literature. CONCLUSIONS: The newly developed doxycycline delivery system achieved the target specifications and is ready for in vivo testing.

Controlled nerve growth factor release from multi-ply alginate/chitosan-based nerve conduits.

The delivery kinetics of growth factors has been suggested to play an important role in the regeneration of peripheral nerves following axotomy. In this context, we designed a nerve conduit (NC) with adjustable release kinetics of nerve growth factor (NGF). A multi-ply system was designed where NC consisting of a polyelectrolyte alginate/chitosan complex was coated with layers of poly(lactide-co-glycolide) (PLGA) to control the release of embedded NGF. Prior to assessing the in vitro NGF release from NC, various release test media, with and without stabilizers for NGF, were evaluated to ensure adequate quantification of NGF by ELISA. Citrate (pH 5.0) and acetate (pH 5.5) buffered saline solutions containing 0.05% Tween 20 yielded the most reliable results for ELISA active NGF. The in vitro release experiments revealed that the best results in terms of reproducibility and release control were achieved when the NGF was embedded between two PLGA layers and the ends of the NC tightly sealed by the PLGA coatings. The release kinetics could be efficiently adjusted by accommodating NGF at different radial locations within the NC. A sustained release of bioactive NGF in the low nanogram per day range was obtained for at least 15days. In conclusion, the developed multi-ply NGF loaded NC is considered a suitable candidate for future implantation studies to gain insight into the relationship between local growth factor availability and nerve regeneration.

Kinetics of solvent extraction/evaporation process for PLGA microparticle fabrication.

Organic solvent extraction/evaporation from an o/w-dispersion has been widely used for the fabrication of PLGA microparticles. The purpose of this work was to elucidate the kinetics of the solvent extraction/evaporation process. A mathematical diffusion model was developed and applied to predict the duration of the solvent extraction. As the diffusion coefficient, D(p), plays a major role in the modeled process, a new and experimentally simple method for estimating D(p) was developed. Both the experimental method and the mathematical model were validated through PLGA microparticle fabrication experiments. For microparticles of mode diameters of 2 and 20 microm, the solvent was extracted in approximately 10 s. Sufficient hardening of the microparticles required, however, the evaporation of solvent from the extraction phase. Residual solvent in extraction phase exerted a strong effect on the morphology of the final product as demonstrated by scanning electron microscopy. Only if most solvent was removed from the aqueous extraction phase, a powdery product of individual microparticles was obtained. At residual organic solvent concentration of above 0.2% in the extraction phase, the microparticles strongly aggregated during collection on a membrane filter and final drying. The presented methods may be useful for better controlling microparticle fabrication processes by solvent extraction/evaporation.

Silk fibroin matrices for the controlled release of nerve growth factor (NGF).

Nerve conduits (NC) for peripheral nerve repair should guide the sprouting axons and physically protect the axonal cone from any damage. The NC should also degrade after completion of its function to obviate the need of subsequent explanation and should optionally be suitable for controlled drug release of embedded growth factors to enhance nerve regeneration. Silk fibroin (SF) is a biocompatible and slowly biodegradable biomaterial with excellent mechanical properties that could meet the above stated requirements. SF material (films) supported the adherence and metabolic activity of PC12 cells, and, in combination with nerve growth factor (NGF), supported neurite outgrowth during PC12 cell differentiation. NGF-loaded SF-NC were prepared from aqueous solutions of NGF and SF (20%, w/w), which were air-dried or freeze-dried (freezing at -20 or -196 degrees C) in suitable molds. NGF release from the three differently prepared SF-NC was prolonged over at least 3 weeks, but the total amount released depended on the drying procedure of the NC. The potency of released NGF was retained within all formulations. Control experiments with differently dried NGF-lactose solutions did not evidence marked protein aggregation (SEC, HPLC), loss of ELISA-reactivity or PC12 cell bioactivity. This study encourages the further exploitation of SF-NC for growth factor delivery and evaluation in peripheral nerve repair.

The preservation of phenotype and functionality of dendritic cells upon phagocytosis of polyelectrolyte-coated PLGA microparticles.

Biodegradable microparticles (MP) represent a promising and efficient delivery system for parenteral vaccination. Recently, MP have also been explored as tool for the ex vivo antigen loading of professional antigen-presenting cells such as dendritic cells (DC) to be used as cellular vaccines. The purpose of this study was to investigate various polycationic coatings on poly(lactide-co-glycolide) (PLGA) MP, with regard to their effect on phenotypic and functional maturation of monocyte-derived DC (MoDC) that had previously been loaded with the MP in vitro. The preparation and concomitant coating of the PLGA was performed by means of a solvent extraction/evaporation method using a recently developed microextrusion-based technique. The polyelectrolytes tested for MP coating encompassed aminodextran, chitosan, poly(ethylene imine) (PEI), poly(L-lysine) and protamine. Uncoated and differently coated PLGA MP were fed to immature MoDC, which ingested efficiently the different MP types irrespective of their surface coating. The MP-loaded immature MoDC were then matured with the help of a cytokine/PGE-2 maturation cocktail. Here, the presence of the ingested MP did not affect the MoDC maturation in terms of expression of the surface markers CD80, CD83, CD86, HLA-DR and MMR, irrespective of the MP surface coating. Importantly, none of the PLGA MP types alone induced significant maturation of MoDC in the absence of the maturation cocktail. MP-loaded and subsequently matured MoDC expressed high levels of the chemokine receptor CCR7, whose functional activity was evidenced by the migration of MoDC towards CCL21, irrespective of the presence of ingested MP. Further, MP-loaded and subsequently matured MoDC also secreted comparable amounts of IL-10 and IL-12p70, irrespective of the presence of ingested MP except for PEI-coated PLGA MP, which enhanced significantly the secretion of IL-12p70 in mature MoDC. In conclusion, phenotypic and functional maturation of MoDC by means of a maturation cocktail remained unchanged irrespective of the presence of previously ingested differently coated PLGA MP. This offers interesting perspectives for using these particulate systems together with entrapped antigens for ex vivo loading of MoDC in view of cellular immunotherapy.

Hydrogel nerve conduits produced from alginate/chitosan complexes.

Nerve conduits (NCs) represent a promising alternative to conventional treatments for peripheral nerve repair. Materials for NC production should be biodegradable, possess adequate mechanical properties, and allow for exchange of nutrients. To this aim, we developed biodegradable NC made of a hydrogel that consisted of the oppositely charged polysaccharides alginate and chitosan. Swelling and permeation studies, as well as rheological measurements, served to characterize the NC. The alginate/chitosan NC showed high water uptake (84% w/w) and permitted permeation of fluorescent-labeled dextrans in a molecular weight dependent manner. The NC fulfilled the mechanical specifications without further crosslinking. The soft NC can be expected to preclude nerve compression (storage modulus of about 40 kPa), but possess sufficient mechanical strength. In combination with remarkable tear resistance, the NC affords easy surgical handling.

One-step preparation of polyelectrolyte-coated PLGA microparticles and their functionalization with model ligands.

This work aimed at the development of a novel surfactant-free, one-step process for the concomitant formation of poly(lactide-co-glycolide) (PLGA) microparticles (MP) and surface coating with the polyelectrolyte chitosan, which is suitable for subsequent covalent conjugation of bioactive ligands. The technology is based on solvent extraction from an O/W-dispersion using a static micromixer. Surface coating occurred through interaction of the negatively charged, nascent PLGA MP with the polycationic chitosan, which was dissolved in the aqueous extraction fluid. Particles of 1-10 mum in diameter were produced with excellent reproducibility. The chitosan-coated PLGA MP were spherical and showed a smooth surface without pores, as demonstrated by scanning electron microscopy (SEM). The chitosan coatings were characterized by zeta potential measurements and X-ray photoelectron spectroscopy (XPS). The functional amino groups of chitosan were used to conjugate two model ligands to the coating, i.e. fluorescamine and NHS-PEG-biotin. The presence of the conjugated ligands was revealed by confocal laser scanning microscopy (CLSM) and fluorescence activated cell sorting (FACS). Evidence for biotinylation was demonstrated through binding of fluorescently labelled streptavidin. The developed platform technology is straightforward and flexible. Future studies will focus on the design of microparticulate carriers with bioactive surfaces, e.g. as antigen delivery systems.

Continuous contact- and contamination-free ultrasonic emulsification-a useful tool for pharmaceutical development and production.

A novel concept was developed here for the continuous, contact- and contamination-free treatment of fluid mixtures with ultrasound. It is based on exciting a steel jacket with an ultrasonic transducer, which transmitted the sound waves via pressurised water to a glass tube installed inside the jacket. Thus, no metallic particles can be emitted into the sonicated fluid, which is a common problem when a sonotrode and a fluid are in direct contact. Moreover, contamination of the fluid from the environment can be avoided, making the novel ultrasonic flow-through cell highly suitable for aseptic production of pharmaceutical preparations. As a model system, vegetable oil-in-water emulsions, fed into the cell as coarse pre-emulsions, were studied. The mean droplet diameter was decreased by two orders of magnitude yielding Sauter diameters of 0.5 microm and below with good repeatability. Increasing the residence time in the ultrasonic field and the sonication power both decreased the emulsion mean diameter. Furthermore, the ultrasonic flow-through cell was found to be well suited for the production of nanoparticles of biodegradable polymers by the emulsion-solvent extraction/ evaporation method. Here, perfectly spherical particles of a volume mean diameter of less than 0.5 microm could be prepared. In conclusion, this novel technology offers a pharmaceutically interesting platform for nanodroplet and nanoparticle production and is well suited for aseptic continuous processing.

PLGA-microencapsulation protects Salmonella typhi outer membrane proteins from acidic degradation and increases their mucosal immunogenicity.

Salmonella (S.) enterica infections are an important global health problem with more than 20 million individuals suffering from enteric fever annually and more than 200,000 lethal cases per year. Although enteric fever can be treated appropriately with antibiotics, an increasing number of antibiotic resistant Salmonella strains is detected. While two vaccines against typhoid fever are currently on the market, their availability in subtropical endemic areas is limited because these products need to be kept in uninterrupted cold chains. Hence, the development of a thermally stable vaccine that induces mucosal immune responses would greatly improve human health in endemic areas. Here, we have combined the high structural stability of Salmonella typhi outer membrane proteins (porins) with their microencapsulation into poly(lactic-co-glycolic acid) (PLGA) to generate an orally applicable vaccine. Encapsulated porins were protected from acidic degradation and exhibited enhanced immunogenicity following oral administration. In particular, the vaccine elicited strong S. typhi-specific B cell responses in Peyer's patches and mesenteric lymph nodes. In sum, PLGA microencapsulation substantially improved the efficacy of oral vaccination against S. typhi.

Formulation aspects of biodegradable polymeric microspheres for antigen delivery.

Biodegradable microspheres (MS) have proven to be very useful antigen delivery systems that are ingested by immunocompetent cells and provide prolonged antigen release and lasting immunity thanks to sustained release of the microencapsulated material. This review provides an applicable summary of different formulation routes for the purpose of producing safe, qualified and efficacious products of microencapsulated peptide and protein antigens. We have brought to attention, with case examples, not only the most common means of improving the quality of microsphere formulations, i.e., the use of stabilising additives, but also less commonly known and applied approaches, e.g., ion pairing, novel polymer systems, solid-state and other innovative microencapsulation methods.

Microencapsulation by solvent extraction/evaporation: reviewing the state of the art of microsphere preparation process technology.

The therapeutic benefit of microencapsulated drugs and vaccines brought forth the need to prepare such particles in larger quantities and in sufficient quality suitable for clinical trials and commercialisation. Very commonly, microencapsulation processes are based on the principle of so-called "solvent extraction/evaporation". While initial lab-scale experiments are frequently performed in simple beaker/stirrer setups, clinical trials and market introduction require more sophisticated technologies, allowing for economic, robust, well-controllable and aseptic production of microspheres. To this aim, various technologies have been examined for microsphere preparation, among them are static mixing, extrusion through needles, membranes and microfabricated microchannel devices, dripping using electrostatic forces and ultrasonic jet excitation. This article reviews the current state of the art in solvent extraction/evaporation-based microencapsulation technologies. Its focus is on process-related aspects, as described in the scientific and patent literature. Our findings will be outlined according to the four major substeps of microsphere preparation by solvent extraction/evaporation, namely, (i) incorporation of the bioactive compound, (ii) formation of the microdroplets, (iii) solvent removal and (iv) harvesting and drying the particles. Both, well-established and more advanced technologies will be reviewed.