Colonic delivery of beta-lactamases does not affect amoxicillin pharmacokinetics in rats.

Pectin beads containing beta-lactamases were designed for the hydrolysis of colonic residual antibiotics responsible for the emergence of resistance. Beads were prepared by ionotropic gelation in CaCl2 and stabilized by coating with polyethylenimine (PEI) to resist disintegration in the upper GI tract. Particle characterization showed that dried beads had a diameter around 1 mm independently of the presence of PEI. Seven to ten percent (w/w) of PEI was located on bead surface forming a coating layer as observed by scanning electron microscopy. PEI improved considerably bead stability in simulated intestinal medium while affecting slightly the encapsulation efficiency of active beta-lactamases. Coated beads were able to preserve beta-lactamases from premature leakage in the upper GIT whereas, in simulated colonic medium, pectinases induced matrix degradation and reduction of beta-lactamase content especially in beads coated in a 0.8% PEI solution. Finally, the pharmacokinetics of amoxicillin in rat after oral administration was not modified by the co-administration of beads containing beta-lactamases. In conclusion, PEI-coated beads are stable in the upper GIT but remain sensitive to the action of pectinolytic enzymes allowing release of beta-lactamases in a colonic medium without modification of the absorption of a beta-lactam antibiotic when co-administered with loaded beads.

Comparative in vitro study of oesophageal adhesiveness of different commercial formulations containing alendronate.

Cases of oesophageal irritation have been reported in patients ingesting alendronate with little liquid or reclining shortly after taking the medication. Pill-induced oesophagitis principally occurs because of adherence of ingested tablets to the epithelial surface. The objective of this in vitro study was to evaluate the oesophageal bioadhesive characteristics of alendronate generics marketed in Europe, the proprietary Fosamax((R)), one negative and two positive polymer controls. A texture analyser was used for qualitative analysis and to determine the maximal detachment force and the adhesion work developed by each formulation on porcine oesophageal mucosa. Fosamax showed few or no bioadhesive characteristics, but the detachment of few tablets powder particles in some of the experiments does not preclude the potential risk of oesophageal lesions. The 10-mg generic Teva tablets had bioadhesive characteristics similar to a positive control. Other generic formulations (Alenat, Stada, Aliud, Ratiopharm showed "cleavage" rupture, leaving a large piece of the tablet mass attached to the mucosa. The bioadhesive characteristics seem to be related to the inactive ingredients: the presence of adhesive polymers such as HPC or very active disintegration agents, such as sodium croscarmellose. The demonstrated differences in adhesiveness suggest that differences in oesophageal tolerance between Fosamax tablets and generics of sodium alendronate may exist.

Design and characterisation of poly(lactide-co-glycolide) small particulate systems for the delivery of immunostimulant CpG oligonucleotide.

The aim of this study was to develop and characterize biodegradable small particles of poly(lactide-co-glycolide) (PLGA) as oral vehicle for immunostimulatory oligonucleotide (ODN-CpG). Three different polymers were used as surface stabilizing agents (SSA): polyvinyl alcohol (PVA), hydrophobically modified hydroxyethylcellulose (HMHEC), or polyethylenimine (PEI). Particle surface was characterized as well as ODN-CpG release kinetics. All particles were found to be around 1 microm. Particles of PLGA-PVA and PLGA-HMHEC were spherical in shape with a smooth surface whereas PLGA-PEI particles were porous. The presence of ODN-CpG within the particle matrix was confirmed in all particle type using scanning laser confocal microscopy. Particle surface assayed by XPS, zeta potential analysis, and evaluation of particle surface hydrophobicity suggested that a significant amount of SSA remains associated onto particle surface. Release profiles evidenced that ODN-CpG release was strongly dependent on particle surface properties. 100% of encapsulated ODN-CpG was released from PLGA-PVA and PLGA-HMHEC particles 37 days after incubation in a buffer solution, whereas only 25% were released from PLGA-PEI particles. ODN-CpG can therefore be nicely entrapped in several types of small particles displaying a prolonged and controlled release upon time. In addition, particle surface is not modified by the presence of ODN-CpG.

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.

Role of gut macrophages in mice orally contaminated with scrapie or BSE.

While there is a growing consensus on the understanding of the propagation pathways after oral infection of transmissible spongiform encephalopathy (TSE) agents and even if the central role of follicular dendritic cells is identified, little is known about the key players in the first steps of the infection and about the site of the disease development. We investigated the role of gut macrophages, which are capable of capturing aggregates of the prion protein. PLGA particles containing clodronate were designed in order to be orally administered and to target Peyer's patches for inducing gut-associated macrophages suicide in mice. Mice were subsequently infected with scrapie or BSE by the oral route. It was found that the efficacy of macrophage suppression in the Peyer's patches correlated well with an earlier appearance of PrPres in these formations and with a higher amount of PrPres at a later stage of the infection. Thus, the capture of infectious particles that have crossed the epithelial gut barrier and their elimination by macrophages seems to be a key event to restrict the amount of agent initiating the infection.

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.