Mesoporous silica nanoparticles as antigen carriers and adjuvants for vaccine delivery

Physicochemical and immunological assessment of engineered pure protein particles with different redox states

The development of subunit antigen delivery formulations has become an important research endeavor, especially in cases where a whole cell vaccine approach has significant biosafety issues. Particle-based systems have shown particular efficacy due to their inherent immunogenicity. In some cases, fabrication techniques can lead to changes in the redox states of encapsulated protein antigens. By employing a uniform, well-characterized, single-protein system, it is possible to elucidate how the molecular details of particle-based protein antigens affect their induced immune responses. Using mesoporous silica-templated, amide bond-stabilized ovalbumin particles, three types of particles were fabricated from native, reduced, and oxidized ovalbumin, resulting in particles with different physicochemical properties and immunogenicity. Phagocytosis, transcription factor activation, and cytokine secretion by a mouse macrophage cell line did not reveal significant differences between the three types of particles. Oxidation of the ovalbumin, however, was shown to inhibit the intracellular degradation of the particles compared with native and reduced ovalbumin particles. Slow intracellular degradation of the oxidized particles was correlated with inefficient antigen presentation and insignificant levels of T cell priming and antibody production in vivo. In contrast, particles fabricated from native and reduced ovalbumin were rapidly degraded after internalization by macrophages in vitro and resulted in significant T cell and B cell immune responses in vivo. Taken together, the current study demonstrates how the redox state of a protein antigen significantly impacts the immunogenicity of the particulate vaccine formulations.

One-step synthesized immunostimulatory oligonucleotides-functionalized quantum dots for simultaneous enhanced immunogenicity and cell imaging

Unmethylated cytosine-phosphate-guanine (CpG) dinucleotides, normally occur in natural bacterial and viral genomes, show strong immunostimulatory activities to invading pathogens and have found widespread applications in both basic research and clinical trials. For the first time, we design a simple one-step synthesis of CpG-functionalized quantum dots (QDs), combining fascinating features of enhanced immunogenicity and cell imaging. The induction of QDs can greatly increase CpG uptake ability by TLR9-positive cells and elevate CpG stability against nuclease degradation. What is more, the outstanding optical properties also suggest that the CpG-QDs can serve as promising optical probes for the evaluation of the cellular uptake efficiency of the CpG motifs. To our best knowledge, this is the first report to use a facile one-pot synthesis strategy that allows the CpG-functionalized QDs to be prepared, which are able to serve as both the potent platform for immunotherapy and the fluorescent probes for intracellular imaging.

Polymer nanotechnology based approaches in mucosal vaccine delivery: challenges and opportunities

Mucosal sites serve as the main portal for the entry of pathogens and thus immunization through mucosal routes can greatly improve the immunity. Researchers are continuously exploring the vaccination strategies to engender protective mucosal immune responses. Unearthing of mucosal adjuvants, that are safe and effective, is enhancing the magnitude and quality of the protective immune response. Use of nanotechnology based polymeric nanocarrier systems which encapsulate vaccine components for protection of sensitive payload, incorporate mucosal adjuvants to maximize the immune responses and target the mucosal immune system is a key strategy to improve the effectiveness of mucosal vaccines. These advances promise to accelerate the development and testing of new mucosal vaccines against many human diseases. This review focuses on the need for the development of nanocarrier based mucosal vaccines with emphases on the polymeric nanoparticles, their clinical status and future perspectives. This review focuses on the need and new insights for the development of nanoarchitecture governed mucosal vaccination with emphases on the various polymeric nanoparticles, their clinical status and future perspectives.

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.

Advances in Anticancer Protein Delivery Using Micro-/ Nanoparticles

Proteins exhibiting anticancer activities, especially those capable of discriminately killing cancer cells, have attracted increasing interest in developing protein-based anticancer therapeutics. This progress report surveys recent advances in delivering anticancer proteins directly to tumor tissue for inducing apoptosis/necrosis or indirectly to antigen presenting cells for provoking immune responses. Protein delivery carriers such as inorganic particles, lipid particles, polymeric particles, DNA/protein based biomacromolecular particles as well as cell based carriers are reviewed with comments on their advantages and limitations. Future challenges and opportunities are also discussed.

The practicality of mesoporous silica nanoparticles as drug delivery devices and progress toward this goal

Mesoporous silica nanoparticles (MSNs) have been proposed as drug delivery devices for approximately 15 years. The history of in vitro studies has been promising, demonstrating that MSNs have the capability for stimulus-responsive controlled release, good cellular uptake, cell specific targeting, and the ability to carry a variety of cargoes from hydrophobic drug molecules to imaging agents. However, the translation of the in vitro findings to in vivo conditions has been slow. Herein, we review the current state-of-the-art in the use of MSN for systemic drug delivery in vivo and provide critical insight into the future of MSNs as systemic drug delivery devices and directions that should be undertaken to improve their practicality.

In vivo delivery of bovine viral diahorrea virus, E2 protein using hollow mesoporous silica nanoparticles

Our work focuses on the application of mesoporous silica nanoparticles as a combined delivery vehicle and adjuvant for vaccine applications. Here we present results using the viral protein, E2, from bovine viral diarrhoea virus (BVDV). BVDV infection occurs in the target species of cattle and sheep herds worldwide and is therefore of economic importance. E2 is a major immunogenic determinant of BVDV and is an ideal candidate for the development of a subunit based nanovaccine using mesoporous silica nanoparticles. Hollow type mesoporous silica nanoparticles with surface amino functionalisation (termed HMSA) were characterised and assessed for adsorption and desorption of E2. A codon-optimised version of the E2 protein (termed Opti-E2) was produced in Escherichia coli. HMSA (120 nm) had an adsorption capacity of 80 μg Opti-E2 per mg HMSA and once bound E2 did not dissociate from the HMSA. Immunisation studies in mice with a 20 μg dose of E2 adsorbed to 250 μg HMSA was compared to immunisation with Opti-E2 (50 μg) together with the traditional adjuvant Quillaja saponaria Molina tree saponins (QuilA, 10 μg). The humoral responses with the Opti-E2/HMSA nanovaccine although slightly lower than those obtained for the Opti-E2 + QuilA group demonstrated that HMSA particles are an effective adjuvant that stimulated E2-specific antibody responses. Importantly the cell-mediated immune responses were consistently high in all mice immunised with Opti-E2/HMSA nanovaccine formulation. Therefore we have shown the Opti-E2/HMSA nanoformulation acts as an excellent adjuvant that gives both T-helper 1 and T-helper 2 mediated responses in a small animal model. This study has provided proof-of-concept towards the development of an E2 subunit nanoparticle based vaccine.

Evaluation of synergistic effect of biodegradable polymeric nanoparticles and aluminum based adjuvant for improving vaccine efficacy

Aluminum based adjuvants have been used widely to induce long lasting protective immunity through vaccination. But reported incidences of toxicity and side effects of aluminum have raised concerns regarding their safety in childhood vaccines. The present study demonstrates the synergistic effect of admixture of polylactic acid-polyethylene glycol (PLA-PEG) based biodegradable nanoparticles (NPs) and aluminum phosphate as a potential adjuvant system using tetanus toxoid (TT) as a model antigen. The immunological activity of the admixture formulation was maintained up to 180 days of storage at 5 °C±3 °C. Percent adsorption/encapsulation of tetanus toxoid increased to nearly 90% in admixture formulation as compared to 55% in conventional vaccine. Admixture preparation (PLA-PEG-Al 0.2 mg-TT and PLA-Al 0.2 mg-TT) showed 80% and 50% survival respectively, even at 180 days as compared to 30% survival observed in the conventional tetanus vaccine. The present study established the feasibility to formulate a dosage form with improved efficacy and reduced aluminum concentration for vaccination.

Facile synthesis of mesoporous silica and titania supraparticles by a meniscus templating route on a superhydrophobic surface and their application to adsorbents

Mesoporous silica and titania supraparticles with controllable pore size, particle size, and macroscopic morphology were readily synthesized by a novel synthetic pathway using meniscus templating on a superhydrophobic surface, which is much simpler than well-known emulsion systems. Moreover, we first report that despite the very large radius of droplet curvature on a millimeter scale, supraparticles kept the round cap morphology due to addition of sucrose as a shape preserver as well as a pore-forming agent. In addition, mesoporous silica and titania supraparticles provided good adsorption performance for Acid Blue 25 and Cr(VI), and were easily separated from the solution by using a scoop net after adsorption tests.

Noncovalent functionalization of mesoporous silica nanoparticles with amphiphilic peptides

The surface of mesoporous silica nanoparticles (MSNs) has been modified for enhancing their cellular uptake, cell targeting, bioimaging, and controlled drug release. For this purpose, covalent anchorage on the silica surface was predominantly exploited with a wide range of bioactive molecules. Here, we describe a facile self-assembly method to prepare a hybrid peptide silica system composed of octyl-modified mesoporous silica nanoparticles (MSNs) and peptide amphiphiles (PAs). The hydrophobic organosilane surface of mesoporous silica was coated with amphiphilic peptide molecules. The peptide functionalized particles exhibited good cyto-compatibility with vascular smooth muscle and vascular endothelial cells. The peptide coating also improved the cellular uptake of particles up to 6.3 fold, which is promising for the development of highly efficient MSN based theranostic agents.