Biodegradable microparticles for the mucosal delivery of antibacterial and dietary antigens

PLGA Particles in Immunotherapy

Poly(lactic-co-glycolic acid) (PLGA) particles are a widely used and extensively studied drug delivery system. The favorable properties of PLGA such as good bioavailability, controlled release, and an excellent safety profile due to the biodegradable polymer backbone qualified PLGA particles for approval by the authorities for the application as a drug delivery platform in humas. In recent years, immunotherapy has been established as a potent treatment option for a variety of diseases. However, immunomodulating drugs rely on targeted delivery to specific immune cell subsets and are often rapidly eliminated from the system. Loading of PLGA particles with drugs for immunotherapy can protect the therapeutic compounds from premature degradation, direct the drug delivery to specific tissues or cells, and ensure sustained and controlled drug release. These properties present PLGA particles as an ideal platform for immunotherapy. Here, we review recent advances of particulate PLGA delivery systems in the application for immunotherapy in the fields of allergy, autoimmunity, infectious diseases, and cancer.

Plant-derived protein bodies as delivery vehicles for recombinant proteins into mammalian cells

The encapsulation of biopharmaceuticals into micro- or nanoparticles is a strategy frequently used to prevent degradation or to achieve the slow release of therapeutics and vaccines. Protein bodies (PBs), which occur naturally as storage organelles in seeds, can be used as such carrier vehicles. The fusion of the N-terminal sequence of the maize storage protein, γ-zein, to other proteins is sufficient to induce the formation of PBs, which can be used to bioencapsulate recombinant proteins directly in the plant production host. In addition, the immunostimulatory effects of zein have been reported, which are advantageous for vaccine delivery. However, little is known about the interaction between zein PBs and mammalian cells. To better understand this interaction, fluorescent PBs, resulting from the fusion of the N-terminal portion of zein to a green fluorescent protein, was produced in Nicotiana benthamiana leaves, recovered by a filtration-based downstream procedure, and used to investigate their internalization efficiency into mammalian cells. We show that fluorescent PBs were efficiently internalized into intestinal epithelial cells and antigen-presenting cells (APCs) at a higher rate than polystyrene beads of comparable size. Furthermore, we observed that PBs stimulated cytokine secretion by epithelial cells, a characteristic that may confer vaccine adjuvant activities through the recruitment of APCs. Taken together, these results support the use of zein fusion proteins in developing novel approaches for drug delivery based on controlled protein packaging into plant PBs.

Poly(lactic-co-glycolic) acid nanoparticles improve oral bioavailability of hypocrellin A in rat

The release of HA from PLGA/HA NPs was carried by dissolving PLGA/HA NPs in artificial gastric (pH 1.5), intestinal (pH 6.8) and blood (pH 7.4) media.

Lipid coated mesoporous silica nanoparticles as an oral delivery system for targeting and treatment of intravacuolar Salmonella infections

Lipid coated mesoporous silica nanoparticle (L-MSN) were synthesized for oral delivery and targeting of ciprofloxacin for intracellular elimination ofSalmonellapathogen.

Rational design for multifunctional non-liposomal lipid-based nanocarriers for cancer management: theory to practice

Nanomedicines have gained more and more attention in cancer therapy thanks to their ability to enhance the tumour accumulation and the intracellular uptake of drugs while reducing their inactivation and toxicity. In parallel, nanocarriers have been successfully employed as diagnostic tools increasing imaging resolution holding great promises both in preclinical research and in clinical settings. Lipid-based nanocarriers are a class of biocompatible and biodegradable vehicles that provide advanced delivery of therapeutic and imaging agents, improving pharmacokinetic profile and safety. One of most promising engineering challenges is the design of innovative and versatile multifunctional targeted nanotechnologies for cancer treatment and diagnosis. This review aims to highlight rational approaches to design multifunctional non liposomal lipid-based nanocarriers providing an update of literature in this field.

Synthesis and characterization of thiolated carboxymethyl chitosan-graft-cyclodextrin nanoparticles as a drug delivery vehicle for albendazole

A new strategy for the synthesis of thiolated carboxymethyl chitosan-g-cyclodextrin nanoparticles by an ionic-gelation method is presented. The synthetic approach was based on the utilization of 1,6-hexamethylene diisocyanate during cyclodextrin grafting onto carboxymethyl chitosan. The use of the 1,6-hexamethylene diisocyanate resulted in reactions between cyclodextrin and active sites at the C6-position of chitosan, and preserved amino groups of chitosan for subsequent reactions with thioglycolic acid, as the thiolating agent, and tripolyphosphate, as the gelling counterion. Various methods such as scanning electron microscopy, rheology and in vitro release studies were employed to exhibit significant features of the nanoparticles for mucosal albendazole delivery applications. It was found that the thiolated carboxymethyl chitosan-g-cyclodextrin nanoparticles prepared using an aqueous solution containing 1 wt% of tripolyphosphate and having 115.65 (μmol/g polymer) of grafted thiol groups show both the highest mucoadhesive properties and the highest albendazole entrapment efficiency. The latter was confirmed theoretically by calculating the enthalpy of mixing of albendazole in the above thiolated chitosan polymer.

Formulation design considerations for oral vaccines

Whilst oral vaccination is a potentially preferred route in terms of patient adherence and mass vaccination, the ability to formulate effective oral vaccines remains a challenge. The primary barrier to oral vaccination is effective delivery of the vaccine through the GI tract owing to the many obstacles it presents, including low pH, enzyme degradation and bile-salt solubilization, which can result in breakdown/deactivation of a vaccine. For effective immune responses after oral administration, particulates need to be taken up by the M cells however, these are few in number. To enhance M-cell uptake, particle characteristics can be optimized with particle size, surface charge, targeting groups and bioadhesive properties all being considerations. Yet improved uptake may not translate into enhanced immune responses and formulating particulates with inherent adjuvant properties can offer advantages. Within this article, we establish the options available for consideration when building effective oral particulate vaccines.

Veterinary vaccines: alternatives to antibiotics?

The prevention of infectious diseases of animals by vaccination has been routinely practiced for decades and has proved to be one of the most cost-effective methods of disease control. However, since the pioneering work of Pasteur in the 1880s, the composition of veterinary vaccines has changed very little from a conceptual perspective and this has, in turn, limited their application in areas such as the control of chronic infectious diseases. New technologies in the areas of vaccine formulation and delivery as well as our increased knowledge of disease pathogenesis and the host responses associated with protection from disease offer promising alternatives for vaccine formulation as well as targets for the prevention of bacterial disease. These new vaccines have the potential to lessen our reliance on antibiotics for disease control, but will only reach their full potential when used in combination with other intervention strategies.

Past, present, and future technologies for oral delivery of therapeutic proteins

Biological drugs are usually complex proteins and cannot be orally delivered due to problems related to degradation in the acidic and protease-rich environment of the gastrointestinal (GI) tract. The high molecular weight of these drugs often results in poor absorption into the periphery when administered orally. The most common route of administration for these therapeutic proteins is injection. Most of these proteins have short serum half-lives and need to be administered frequently or in high doses to be effective. So, difficulties in the administration of protein-based drugs provides the motivation for developing drug delivery systems (DDSs) capable of maintaining therapeutic drug levels without side effects as well as traversing the deleterious mucosal environment. Employing a polymer as an entrapment matrix is a common feature among the different types of systems currently being pursued for protein delivery. Protein release from these matrices can occur through various mechanisms, such as diffusion through or erosion of the polymer matrix, and sometimes a combination of both. Encapsulation of proteins in liposomes has also been a widely investigated technology for protein delivery. All of these systems have merit and our worthy of pursuit.

Doxorubicin-loaded PLGA nanoparticles by nanoprecipitation: preparation, characterization and in vitro evaluation

AIMS

The lack of specificity of chemotherapeutic agents to cancer tissue commonly leads to dose-limiting side effects and poor therapeutic results. Drug delivery systems promise to improve the deficiencies of chemotherapeutic treatment by modifying the biodistribution and pharmacokinetics of the drug in vivo. Here, we report the preparation, characterization and in vitro evaluation of a carrier for the chemotherapeutic drug doxorubicin based on acid-capped poly(lactic-co-glycolic acid) nanoparticles.

METHODS

Doxorubicin-loaded nanoparticles were prepared by nanoprecipitation with bovine serum albumin as the stabilizer. Nanoparticles were characterized and their interaction with MDA-MB-231 breast cancer cells was examined with confocal microscopy and a toxicological assay.

RESULTS

Spherical particles with an average diameter of 230 nm, a zeta-potential of -45 mV and a maximum drug loading of 5 wt% were prepared. Doxorubicin was found to be quickly released at endolysosomal pH of 4.0 but was released at a slower rate at pH 7.4. Nanoparticles were found to deliver the drug into cells quickly and in higher quantity than when presented in solution and were found to result in a therapeutic efficacy comparable to the free drug.

DISCUSSION

Nanoprecipitation was found to be a promising method for the preparation of nanoparticles with relatively high doxorubicin loading. The pH-dependent release behavior is discussed to possibly be a result of accelerated degradation of the polymer and decreasing ionic interaction between the drug and the polymer at acidic pH. Additional studies are needed to determine why increased nuclear localization of the drug when delivered in the form of nanoparticles did not result in increased therapeutic efficacy in vitro.

CONCLUSION

Nanoparticles formulated by nanoprecipitation of acid-ended poly(lactic-co-glycolic acid) were found to be able to control the release of doxorubicin in a pH-dependent manner and to effectively deliver high payloads of the drug in an active form to MDA-MB-231 breast cancer cells.

Nanoparticles as potential oral delivery systems of proteins and vaccines: a mechanistic approach

Peptides and proteins remain poorly bioavailable upon oral administration. One of the most promising strategies to improve their oral delivery relies on their association with colloidal carriers, e.g. polymeric nanoparticles, stable in gastrointestinal tract, protective for encapsulated substances and able to modulate physicochemical characteristics, drug release and biological behavior. The mechanisms of transport of these nanoparticles across intestinal mucosa are reviewed. In particular, the influence of size and surface properties on their non-specific uptake or their targeted uptake by enterocytes and/or M cells is discussed. Enhancement of their uptake by appropriate cells, i.e. M cells by (i) modeling surface properties to optimize access to and transport by M cells (ii) identifying surface markers specific to human M cell allowing targeting to M cells and nanoparticles transcytosis is illustrated. Encouraging results upon in vivo testing are reported but low bioavailability and lack of control on absorbed dose slow down products development. Vaccines are certainly the most promising applications for orally delivered nanoparticles.

Nanotechnology: intelligent design to treat complex disease

The purpose of this expert review is to discuss the impact of nanotechnology in the treatment of the major health threats including cancer, infections, metabolic diseases, autoimmune diseases, and inflammations. Indeed, during the past 30 years, the explosive growth of nanotechnology has burst into challenging innovations in pharmacology, the main input being the ability to perform temporal and spatial site-specific delivery. This has led to some marketed compounds through the last decade. Although the introduction of nanotechnology obviously permitted to step over numerous milestones toward the development of the "magic bullet" proposed a century ago by the immunologist Paul Ehrlich, there are, however, unresolved delivery problems to be still addressed. These scientific and technological locks are discussed along this review together with an analysis of the current situation concerning the industrial development.

Biodegradable PLGA Particles for Improved Systemic and Mucosal Treatment of Type I Allergy

Although allergen immunotherapy is basically a story of success, it still needs improvement. The goal of this study was to optimize parenteral and oral allergen formulations through using the biocompatible polymer of lactic and glycolic acid (PLGA). Subcutaneous application of birch pollen allergen Bet v 1 encapsulated in nanoparticles biased the immune response toward Th1 in allergic mice and did not elicit granuloma formation in mice and in human volunteers. When oral immunotherapy of mice was tried with birch pollen-filled PLGA microparticles, mucosal targeting was indispensable for achieving any immune response, and targeting of M-cells was necessary for modulating an ongoing allergic response toward Th1. The authors suggest that biocompatible PLGA nano- or microparticles can be useful tools for upgrading therapy of type I allergy.

Mucosal delivery of vaccines in domestic animals

Mucosal vaccination is proving to be one of the greatest challenges in modern vaccine development. Although highly beneficial for achieving protective immunity, the induction of mucosal immunity, especially in the gastro-intestinal tract, still remains a difficult task. As a result, only very few mucosal vaccines are commercially available for domestic animals. Here, we critically review various strategies for mucosal delivery of vaccines in domestic animals. This includes live bacterial and viral vectors, particulate delivery-systems such as polymers, alginate, polyphosphazenes, immune stimulating complex and liposomes, and receptor mediated-targeting strategies to the mucosal tissues. The most commonly used routes of immunization, strategies for delivering the antigen to the mucosal surfaces, and future prospects in the development of mucosal vaccines are discussed.

Particle uptake by Peyer's patches: a pathway for drug and vaccine delivery

Particle uptake by Peyer's patches offers the possibility of tailoring vaccines that can be delivered orally. However, particle uptake by the follicle-associated epithelium in the gastrointestinal tract depends on several different factors that are the physicochemical properties of the particles, the physiopathological state of the animal, the analytical method used to evaluate the uptake and finally the experimental model. These parameters do not allow a clear idea about the optimal conditions to target the Peyer's patches. The goal of this review is to clarify the role of each factor in this uptake.

Ex Vivo Strength Comparison of Bioabsorbable Tendon Plates and Bioabsorbable Suture in a 3-Loop Pulley Pattern for Repair of Transected Flexor Tendons from Horse Cadavers

OBJECTIVE

To test the failure strength and energy of 2 bioabsorbable implants applied to transected deep digital flexor tendons (DDFT) from adult horses.

STUDY DESIGN

Ex vivo biomechanical experiment.

SAMPLE POPULATION

Twelve pairs of deep digital flexor tendons harvested from the forelimbs of fresh equine cadavers.

METHODS

Poly-L-lactic acid tendon plates were custom manufactured for application to the cylindrical surface of an adult equine deep digital flexor tendon. Twelve pairs of DDFTs were transected 2 cm distal to the insertion of the distal check ligament of the deep digital flexor tendon. One tendon of each pair was randomly selected for repair with a biodegradable plate or a 3-loop pulley method. Size 2 polydioxanone suture was used in both repairs. Repairs were tested in tension to failure, with peak force (PF) and total energy (TE) at repair failure recorded in Newtons (N) and Joules (J), respectively. A paired t-test was used for statistical evaluation with a significant level set at P< or = .05.

RESULTS

Mean+/-SD PF for failure of plated tendons (1507.08+/-184.34 N) was significantly greater than for sutured tendons (460.86+/-60.93 N). TE was also significantly greater for failure of plated tendons versus sutured tendons.

CONCLUSIONS

Plate fixation of transected cadaver DDFTs appear to have superior immediate failure strength than 3-loop pulley repairs.

CLINICAL RELEVANCE

Whereas in vivo testing is required, a bioabsorbable tendon plate may provide initial increased strength to support tendon healing and decrease external coaptation requirements.

Immune responses after local administration of IgY loaded-PLGA microspheres in gut-associated lymphoid tissue in pigs

Oral vaccination of large animals using PLGA MS (poly(D,L-lactide-co-glycolide)microspheres) appeared to be more challenging than immunization of mice. The purpose of this study was to deliver to GALT an immunogenic model protein (IgY), free or encapsulated by spray-drying in PLGA MS, and to evaluate systemic immune response in SPF Large White pigs. Pigs were surgically processed for local administration of IgY in three sets of experiments. In two sets of experiments, administration was locally performed in temporary ligatured intestinal segments, in jejunal Peyer's patches and in mesenteric lymph nodes. In the third experiment, pigs received IgY via an intestinal cannula. Total IgY-specific antibodies were detected in the sera of pigs after a single local immunization, but not in the sera of cannulated pigs. The study of IgG1 and IgG2 isotypes indicated that PLGA MS are able to elicit a combined serum IgG2/G1 response with a predominance of IgG1 response when locally administered. PLGA MS can be a potential oral delivery system for antigen but our results underlined the difficulty to immunize large animals like pigs. Transposition of data between small and large animals appears to be complex and suggests that physiological features need to be considered to increase intestinal availability of oral encapsulated vaccines.

Microparticles for oral delivery of vaccines

Nonreplicating antigens are poorly immunogenic when given orally, either due to their degradation in the gastrointestinal tract or because they are not efficiently taken up in the gut. Studies in laboratory animals have clearly demonstrated that microparticles can significantly improve the immunogenicity of orally administered antigens. However, the oral delivery of vaccines using microparticles has not been explored extensively in humans and large animals. In this article the progress in oral microparticle antigen delivery will be reviewed and, where possible, studies in humans and large animals will be highlighted. In addition, possible approaches that have the potential to significantly improve microparticle delivery of oral vaccines will be suggested.

Poly (lactide-co-glycolide) particles of different physicochemical properties and their uptake by peyer's patches in mice

Nano-and microparticles of poly(lactide-co-glycolide) (PLGA) were formulated using poly(vinyl alcohol) (PVA) or hydrophobically modified hydroxyethylcellulose (HMHEC) or polyethyleneimine (PEI) as stabilizers. The uptake by murine Peyer's patches (PPs) and the binding to Peyer's patches-free tissue (PPFT) of these particles was investigated using fluorescence microscopy providing qualitative information about the tissue distribution of particles. Observations of intestinal cryo-sections showed significant discrimination in the uptake by PP of nano-and microparticles. The uptake by PPs of PLGA-PVA and PLGA-HMHEC nano-and microparticles, of negative and neutral zeta potential, respectively, was comparable, whereas a smaller number was observed in the case of nano-and microparticles of PLGA-PEI, positively charged. Moreover, particle uptake by PPs appeared to be strongly size-dependent. The number of particles of mean diameter around 0.3 and 1 microm observed in PPs was much greater than that of particles of diameter average close to 3 microm. However, in all cases, particles were found in the PPFT for at least 48 h. In conclusion, regarding the tissue samples we have observed, it appeared that the uptake of particles by PPs and binding to PPFT could be influenced by the physicochemical properties of the particles but this may not have been true at all sites of the intestine and may differ between animals.

Monodisperse chitosan nanoparticles for mucosal drug delivery

Chitosan nanoparticles (CS NPs) of a controlled size (below 100 nm) and narrow size distribution were obtained through the process of ionic gelation between CS and sodium tripolyphosphate (TPP). A high degree of CS deacetylation and narrow polymer molecular weight distribution were demonstrated to be critical for the controlling particle size distribution. Properties of the CS NPs were examined at different temperatures, values of pH, and ratios of CS to TPP. The model protein, bovine serum albumin, was encapsulated into the NPs, and the in vitro release profiles were examined in physiologically relevant media at 37 degrees C.

Phosphorylcholine-carbohydrate-protein conjugates efficiently induce hapten-specific antibodies which recognize both Streptococcus pneumoniae and Neisseria meningitidis: a potential multitarget vaccine against respiratory infections

Phosphorylcholine (ChoP) is commonly expressed at the surface of pathogens of the respiratory tract, including Streptococcus pneumoniae and Neisseria meningitidis. We designed a synthetic hapten comprising ChoP and part of its native carrier structure in S. pneumoniae, i.e. N-acetyl-D-galactosamine (GalNAc). Protein conjugates of this hapten induced GalNAc-ChoP-specific antibodies which recognized ChoP on both S. pneumoniae and N. meningitidis. GalNAc-ChoP could therefore lead to the rational design of a novel multipurpose vaccine against respiratory infections.