Novel pH-sensitive nanospheres designed for colon-specific delivery were prepared using polymeric mixtures of poly (lactic-co-glycolic) acid (PLGA) and methacrylate copolymers. Budesonide (BSD), a topically active corticosteroid, was entrapped as a model drug. The therapeutic efficacy of the prepared nanospheres was assessed using the trinitrobenzenesulfonic acid (TNBS) colitis rat model, in comparison with conventional enteric microparticles. In addition, the colon targeting properties, systemic bioavailability, and specific uptake by the inflamed colon mucosa were evaluated using coumarin-6 (C-6) loaded nanospheres. The prepared nanospheres showed strongly pH-dependent drug release properties in acidic and neutral pH media followed by a sustained release phase at pH 7.4. Animal experiments revealed the superior therapeutic efficiency of BSD nanospheres in alleviating the conditions of TNBS-induced colitis model. The in-vivo studies using C-6-loaded nanospheres displayed higher colon levels and lower systemic availability of the fluorescent marker when compared with simple enteric coating. Moreover, quantitative analysis of the fluorescent marker and confocal laser scanning studies showed strong and specific adhesion of the nanospheres to the ulcerated and inflamed mucosal tissue of the rat colon. In conclusion, the proposed nanosphere system combined the properties of pH-sensitivity, controlled release, and particulate targeting that could be useful for colon-specific delivery in inflammatory bowel disease.

Protein therapeutics are used in the treatment of a broad variety of diseases, however, usually they are not available as peroral formulations. Oral delivery systems of proteins including insulin, glucagon like peptide, calcitonin or parathyroid hormone are highly demanded by patients suffering from chronic diseases such as diabetes or osteoporosis. The need for oral protein formulations has been recognized by researchers of various scientific disciplines and a number of patents have been filed that deal with technologies capable of facilitating oral protein delivery. Within the current review, patents based on approaches such as particulate delivery systems, multifunctional polymers, enzyme inhibitors, permeation enhancers and ligand-specific binding and uptake are discussed. In addition, the technology platforms of several innovative drug delivery companies are highlighted.

【Background】 Most of therapeutic peptide and protein drugs are administered via injection route, because they are poorly absorbed. Previously, we have investigated the role of different mucoadhesive polymers as coating materials of liposomes for enhancing oral peptide delivery. Trimethyl chitosan (TMC) is a chitosan (CS) derivative with improved permeation enhancing properties as a result of retaining its positive charge over a broad range of physiological pH values. 【Methods and results】 TMC was synthesized by reductive methylation of CS and was used for coating anionic liposomes. The efficiency of surface coating was confirmed by the inversion of surface potential and by increase in particle size. The mucoadhesive properties of TMC-coated liposomes were studied in vivo after oral administration to rats by confocal laser scanning microscopy (CLSM). The results showed comparable mucoadhesive properties of TMC-coated liposomes and CS coated liposomes. In addition, the pharmacological efficacy of calcitonin loaded liposomes was evaluated by determination of blood calcium level after oral administration. The area above blood calcium concentration-time curve (AAC) was significantly higher after oral administration of TMC-liposomes, as compared to non-coated liposomes and calcitonin solution. The obtained results showed that TMC-liposomes can contribute to the development of mucoadhesion based systems for oral peptide and protein delivery.

SUV liposomes modified with wheat germ agglutinin-carbopol (WGA-CP) polymer conjugate were prepared and characterized for oral peptide delivery. The conjugate retained the biological binding activity of WGA without any evidence of cytotoxicity. The cellular uptake of WGA-CP liposomes by Caco-2 cells was about 2-fold higher than that of non-modified or CP-modified liposomes. The uptake was dependent on the surface concentration of WGA, temperature, and incubation time, and was partially inhibited in the presence of filipin, chlorpromazine, and free WGA. Confocal microscopy confirmed the simultaneous uptake of WGA-CP conjugate and liposomes in the cytoplasm Caco-2 cells and enterocytes of rats’ small intestine after oral administration. In addition, the pharmacological efficacy of calcitonin was enhanced by more than 20 and 5 folds after oral administration of WGA-CP liposomes as compared to non modified and CP liposomes, respectively.

Abstract in Japanese

Within the current study, a delivery system based on a novel polymer-lectin conjugate (carbopol-lectin) was evaluated for the oral delivery of therapeutic peptides and proteins. It was demonstrated that covalent attachment of lectin to carbopol does neither decrease nor abolish the specific binding properties of lectin. Bioadhesion studies revealed that liposomes coated with carbopol lectin are more bioadhesive than liposomes coated with unmodified carbopol. Finally, the in vivo data suggest that carbopol-lectin conjugate coated liposomes are effective oral peptide delivery systems which are capable of increasing the pharmacological effect of orally administered calcitonin.

A novel thiomer derivative of glycol chitosan (GCS) was synthesized by coupling with thioglycolic acid (TGA) and evaluated for the pulmonary delivery of peptides. Nanoparticles (NPs) based on GCS and GCS-TGA were obtained by the ionic gelation method and demonstrated a particle size in the range of 0.23-0.33 μm with positive surface charge and high calcitonin entrapment. Fluorescent GCS-TGA NPs resulted in a 2-fold increase in mucoadhesion to lung tissue after intra-tracheal administration to rats as compared to non thiolated NPs. Evaluation of pulmonary toxicity revealed the biocompatibility of the two nanoparticulate formulations with lung tissue. The efficacy of the prepared NPs to enhance the pulmonary absorption of peptides was evaluated after pulmonary administration to rats using a liquid micro-sprayer technique. Calcitonin-loaded GCS and GCS-TGA NPs resulted in a pronounced hypocalcemic effect for at least 12 and 24 h, and a corresponding pharmacological availability of 27 and 40%, respectively. These findings suggest that both GCS and its thiomer derivative are promising and safe carriers for pulmonary peptide delivery.