Hetero-coagulation of polymeric core-corona microspheres

Multifunctional conjugation of proteins on/into bio-nanoparticles prepared by amphiphilic poly(γ-glutamic acid)

The present study focuses on nanoparticles composed of amphiphilic poly(gamma-glutamic acid) (gamma-PGA) as potential protein carriers. Amphiphilic graft co-polymers composed of y-PGA as the hydrophilic backbone and L-phenylalanine ethylester (L-PAE) as the hydrophobic segment were synthesized by grafting L-PAE to y-PGA using water-soluble carbodiimide (WSC). Due to their amphiphilic properties, the gamma-PGA-graft-L-PAE co-polymer formed monodispersed nanoparticles in water. The particle size of the nanoparticles composed of gamma-PGA-graft-L-PAE (gamma-PGA nanoparticles) was about 200 nm and showed a highly negative zeta potential. To evaluate their potential applications as multifunctional protein carrier, we prepared protein-entrapped gamma-PGA nanoparticles by encapsulation, covalent immobilization or physical adsorption methods. For this purpose, 11 different proteins with various molecular weights and isoelectric points (pI values) were used as model proteins. The encapsulation of the protein into the nanoparticles was observed for all tested proteins. The amount of protein covalently immobilized or adsorbed onto the nanoparticles showed different tends based on the molecular weight and pI of each protein. Positively charged proteins could be adsorbed onto the negatively charged nanoparticles by electrostatic interaction. Moreover, it was found that enzyme-encapsulated nanoparticles showed higher enzymatic activity than surface-immobilized nanoparticles. These results indicated that the enzymatic activity of the enzyme-entrapped nanoparticles was significantly affected by the conjugation method, and that encapsulation was the optimal method for the conjugation of proteins and nanoparticles. It is expected that the y-PGA nanoparticle will have great potential as multifunctional carriers in pharmaceutical and biomedical applications, such as drug and vaccine delivery systems.

Development of Vaccine Adjuvants Using Polymeric Nanoparticles and Their Potential Applications for Anti-HIV Vaccine

The development of a prophylactic/therapeutic HIV-1 vaccine based on recombinant proteins is needed for the control of the worldwide AIDS epidemic. Subunit protein and peptide vaccines are generally very safe, with well-defined components. However, these antigens are often poorly immunogenic, and thus require the use of adjuvants to induce adequate immunity. Particulate adjuvants (e.g. micro/nanoparticles, emulsions, ISCOMS, liposomes, virosomes, and virus-like particles) have been widely investigated as HIV-1 vaccine delivery systems. Antigen uptake by antigen-presenting cells (APC) is enhanced by the association of the antigens with polymeric micro/nanoparticles. The adjuvant effect of micro/nanoparticles appears to largely be a consequence of their uptake into APC. More importantly, particulate antigens have been shown to be more efficient than soluble antigens for the induction of immune responses. Over the past two decades, we have studied the synthesis and clinical applications of core-corona polymeric nanospheres composed of hydrophobic polystyrene and hydrophilic macromonomers. Core-corona type polymeric nanospheres have applications in various technological and biomedical fields, because their chemical structures and particle size can be easily controlled. In this study, we focused on the development of a HIV-1 vaccine using polymeric nanoparticles. We evaluated the immunization strategies for HIV-1-capturing core-corona type polystyrene nanospheres that would efficiently induce HIV-1-specific IgA responses in female mice and the macaque genital tract. Moreover, based on this research, we attempted to develop novel biodegradable nanoparticles composed of poly (gamma-glutamic acid) (gamma-PGA) for protein-based vaccine delivery. These HIV-1-capturing nanospheres and protein-loaded gamma-PGA nanoparticles have shown unique potential as vaccine carriers.

Preparation and characterization of biodegradable nanoparticles based on poly(gamma-glutamic acid) with l-phenylalanine as a protein carrier

The objective of the present study was to prepare nanoparticles composed of poly(gamma-glutamic acid) (gamma-PGA) and l-phenylalanine ethylester (l-PAE) in order to evaluate the possibility of using these nanoparticles as protein carriers. Novel amphiphilic graft copolymers composed of gamma-PGA as the hydrophilic backbone and l-PAE as the hydrophobic segment were successfully synthesized by grafting l-PAE to gamma-PGA using water-soluble carbodiimide (WSC). Due to their amphiphilic properties, the gamma-PGA-graft-l-PAE copolymers were able to form nanoparticles. The size of the gamma-PGA nanoparticles was measured by photon correlation spectroscopy (PCS) and showed a monodispersed size distribution with a mean diameter ranging from 150 to 200 nm. The solvents selected to prepare the gamma-PGA nanoparticles by a precipitation and dialysis method affected the particle size distribution. To evaluate the feasibility of vehicles for these proteins, we prepared protein-loaded gamma-PGA nanoparticles by surface immobilization and encapsulation methods. Ovalbumin (OVA) was used as a model protein and was immobilized onto the gamma-PGA nanoparticles or encapsulated into the inner core of these nanoparticles. Moreover, these OVA-encapsulated gamma-PGA nanoparticles could be preserved by freeze-drying process. The results of cytotoxicity tests showed that the gamma-PGA and gamma-PGA nanoparticles did not cause any relevant cell damage. It is expected that biodegradable gamma-PGA nanoparticles can immobilize proteins, peptides, plasmid DNA and drugs onto their surfaces and/or into the nanoparticles. These nanoparticles are potentially useful in pharmaceutical and biomedical applications.

Controlled heterocoagulation of platelets and spheres

We report the controlled heterocoagulation of platelets and spheres, leading to the formation of colloidally stable, anisotropic hybrid particles. Anionically charged, nanosized polymer latex spherical particles were heterocoagulated on the surface of cationically charged hexagonal gibbsite platelets via the adsorption of a single layer of spheres onto both sides of the hexagonal platelets. The latex particles were annealed at a temperature above the Tg of the latex polymer, resulting in a thin polymer layer covering the gibbsite platelets. This heterocoagulation approach enabled the encapsulation of hydrophilic inorganic particles with polymer latexes and the formation of anisotropic hybrid particles.