Tetanus Toxoid Loaded Nanoparticles from Sulfobutylated Poly(Vinyl Alcohol)-Graft-Poly(Lactide-co-Glycolide): Evaluation of Antibody Response After Oral and Nasal Application in Mice

Purpose. Aim of the study was the evaluation of the potential of novel tetanus toxoid (TT) loaded nanoparticles (NP) for electing an immune response in mice against TT. Methods. Six week-old female Balb/c mice were immunized by oral (p.o.), nasal (i.n.) and intraperitoneal (i.p.) application of TT NP loaded by adsorption. As polymer a novel polyester, sulfobutylated poly(vinyl alcohol)-graft-poly(lactide-co-glycolide), SB(43)-PVAL-g-PLGA was used. Blood samples were collected 4 and 6 weeks after immunization and assayed for serum IgG- as well as IgA antibody titers by ELISA. NP formulations varying in size and loading were compared to alum adsorbates as well as to TT solutions. Results. Both, p.o. and i.n. administration of TT associated NP increased serum titers up to 3 × 10³ (IgG) and 2 × 10³ (IgA). While small NP induced significantly higher titers then larger ones after oral administration, intermediate NP induced antibodies after nasal application. Of the mucosal routes investigated, i.n. seems to be more promising compared to p.o. immunization. Conclusions. Antigen loaded NP prepared from surface modified polyesters combined with CT show considerable potential as a vaccine delivery system for mucosal immunization. The results warrant further experiments to explore in more detail the potential use of NP as mucosal vaccine delivery system.     

A Heterogeneously Structured Composite Based on Poly(lactic-co-glycolic acid) Microspheres and Poly(vinyl alcohol) Hydrogel Nanoparticles for Long-Term Protein Drug Delivery

Purpose. To prepare a heterogeneously structured composite based on poly (lactic-co-glycolic acid) (PLGA) microspheres and poly(vinyl alcohol) (PVA) hydrogel nanoparticles for long-term protein drug delivery. Methods. A heterogeneously structured composite in the form of PLGA microspheres containing PVA nanoparticles was prepared and named as PLGA-PVA composite microspheres. A model protein drug, bovine serum albumin (BSA), was encapsulated in the PVA nanoparticles first. The BSA-containing PVA nanoparticles was then loaded in the PLGA microspheres by using a phase separation method. The protein-containing PLGA-PVA composite microspheres were characterized with regard to morphology, size and size distribution, BSA loading efficiency, in vitroBSA release, and BSA stability. Results. The protein-containing PLGA-PVA composite microspheres possessed spherical shape and nonporous surface. The PLGA-PVA composite microspheres had normal or Gaussian size distribution. The particle size ranged from 71.5 m to 282.7 m. The average diameter of the composite microspheres was 180 m. The PLGA-PVA composite microspheres could release the protein (BSA) for two months. The protein stability study showed that BSA was protected during the composite microsphere preparation and stabilized inside the PLGA-PVA composite microspheres. Conclusions. The protein-containing PLGA-PVA composite may be suitable for long-term protein drug delivery.     

Study of the Influence of Several Stabilizing Agents on the Entrapment and In Vitro Release of pBC 264 from Poly(Lactide-Co-Glycolide) Microspheres Prepared by a W/O/W Solvent Evaporation Method

Pharmaceutical Research -     

Effect of Polymeric Network Structure on Drug Release from Cross-Linked Poly(Vinyl Alcohol) Micromatrices

Three types of poly(vinyl alcohol) were cross-linked by glutaraldehyde to form water-swellable materials possessing a three-dimensional, molecular network. Proxyphylline and theophylline were incorporated into the polymer networks during the cross-linking reaction. The firm hydrogels formed were dried and reduced to a particle size of 400–630 µm. The molecular structure of the gels was characterized by equilibrium swelling measurements which allowed the determination of the average distance between two cross-links and, hence, the macromolecular mesh size. The sulfate and glutaraldehyde residues contained in the purified and nonpurified cross-linked polymers were analyzed, and methods for their elimination and inactivation were developed. Drug release from the highly cross-linked gels could be controlled over more than 12 hr, as the diffusion process in these very dense macromolecular networks is rather slow. The extent of branching and entanglement of the polymeric chains appeared to have an important effect. In addition, the release rate was influenced greatly by the amount and, to a lesser extent, by the type of drug in the network.     

Glucose-Responsive Gel from Phenylborate Polymer and Poly (Vinyl Alcohol): Prompt Response at Physiological pH Through the Interaction of Borate with Amino Group in the Gel

Purpose. To design glucose-responsive gels based on the complexation between polymers having phenylboronic acid groups and poly (vinyl alcohol). Specifically, high-glucose sensitivity at physiological pH was achieved through the interaction of phenylborate with amino groups. Method. Terpolymers of m-acrylamidophenylboronic acid, N,N-dimethylaminopropylacrylamide (DMA-PAA), and N,N-dimethylacrylamide were prepared. DMAPAA was introduced in the terpolymer to stabilize phenylborate-polyol complex at physiological pH. The effect of amino groups on complex stabilization was estimated from viscosity as well as UV spectrum measurements. Results. A good correlation was observed between complexation rate and fraction of phenylborate as well as DMAPAA in the terpolymers. In line with this increased complexation rate. UV difference spectra measurement revealed that ionization of phenylboronic acid was facilitated in the terpolymer due to the interaction with DMAPAA. Further, sensitive change in the complexation rate was demonstrated with a variation in glucose concentration, which is in sharp contrast with the poor glucose-sensitivity of the polymer without DMAPAA. Conclusions. The introduction of an amino group into phenylborate polymers was quite effective for increasing the complexation ability and the glucose responsivity at physiological pH. These results suggest the feasibility of this complex-gel system in designing a self-regulated insulin-releasing device.     

Poly(Lactide-Co-Glycolide) Microsphere Formulations of Darbepoetin Alfa: Spray Drying Is an Alternative to Encapsulation by Spray-Freeze Drying

PURPOSE: The purpose of this work was to evaluate spray-freeze drying and spray drying processes for encapsulation of darbepoetin alfa (NESP, Aranesp). METHODS: Darbepoetin alfa was encapsulated in poly(lactide-co-glycolide) by spray-freeze drying and by spray drying. Integrity was evaluated by size-exclusion chromatography and Western blot. Physical properties and in vitro release kinetics were characterized. Pharmacokinetics and pharmacodynamics were evaluated in nude rats. RESULTS: Microspheres produced by spray drying were larger than those produced by spray-freeze drying (69 microm vs. 29 microm). Postencapsulation integrity was excellent for both processes, with < 2% dimer by size-exclusion chromatography. In vitro release profiles were similar, with low burst (< 25%) and low cumulative protein recovery at 4 weeks (< or = 30%), after which time covalent dimer (< or = 6.5%) and high molecular weight aggregates (< or = 2.3%) were recovered by denaturing extraction. After a single injection, darbepoetin alfa was detected in serum through 4 weeks for all microsphere formulations tested in vivo, although relative bioavailability was higher for spray-freeze drying (28%) compared with spray drying (21%; p = 0.08) as were yields (73-82% vs. 34-57%, respectively). For both processes hemoglobin was elevated for 7 weeks, over twice as long as unencapsulated drug. CONCLUSIONS: Spray drying, conducted at pilot scale with commercial equipment, is comparable to spray-freeze drying for encapsulation of darbepoetin alfa.     

Cyrene™ as an Alternative Sustainable Solvent for the Preparation of Poly(lactic-co-glycolic acid) Nanoparticles

Toxic and environmental harmful organic solvents are widely applied to prepare poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles (NP) in standard preparation methods. Alternative non-toxic solvents suffer from disadvantages like high viscosity and plasticizing effects. To overcome these hurdles, Cyrene? as a new sustainable, non-toxic and low viscous solvent was used to formulate PLGA NPs. A new preparation method was developed and optimized. Small sized blank NPs around 220 nm with a narrow size distribution and highly negative charge (<?23 mV) were obtained. To test the application for drug delivery, the lipophilic model drug atorvastatin was encapsulated in high drug loads with comparable physicochemical characteristics as the blank NPs, and a total drug release within 24 h. No changes of the crystallinity or plasticizing effects could be observed. Highly purified NPs were obtained with a residual Cyrene? content <2.5%. Finally, the biocompatibility of Cyrene? itself and of the NPs formed in the presence of Cyrene? was demonstrated in a hen's egg test. Conclusively, the use of Cyrene? as solvent offers a simple, fast and non-toxic procedure for preparation of PLGA NPs as drug delivery systems circumventing the downsides of standard methods.