António Sousa Ribeiro

Design for optimization of nanoparticles integrating biomaterials for orally dosed insulin.

Design of nanoparticles integrating biomaterials that govern the functional behavior of orally dosed insulin is focused on improving insulin stability and absorption by facilitating its uptake and translocation throughout the intestinal membrane, while providing protection from acidic and enzymatic degradation in the gastrointestinal tract. The purpose of the study was to optimize a nanoparticle formulation by investigating the relationship between design factors and experimental data by response surface methodology. Designed nanoparticles consisting of calcium crosslinked alginate, dextran sulfate, poloxamer 188 and chitosan followed by an outermost coating of albumin are described as multilayer complex retaining insulin within the nanoparticle. A 3-factor 3-level Box-Behnken design was used to optimize nanoparticle formulation. The screened independent variables were the concentration of calcium chloride, chitosan and albumin, and the dependent variables were particle size, polydispersity index, zeta potential, entrapment efficiency and insulin release in enzyme-free simulated digestive fluids. Experimental responses of a total of 15 formulations resulted in mean nanoparticle diameters ranging from 394 to 588 nm, with polydispersity index from 0.77 to 1.10, zeta potential values ranging from -36.6 to -44.5 mV, and entrapment efficiency of insulin was over 85%. Insulin release from nanoparticles in enzyme-free digestive fluids was prevented during 120 min in gastric conditions, and over 80% of insulin was released after 180 min in simulated intestinal fluid. Based on the experimental responses and the criteria of desirability defined by constraints, solutions of 0.20% calcium chloride, 0.04% chitosan and 0.47% albumin constitute the optimum formulation of nanoparticles for orally dosed insulin.

Dual chitosan/albumin-coated alginate/dextran sulfate nanoparticles for enhanced oral delivery of insulin

The potential of nanoparticles (NPs) to overcome the barriers for oral delivery of protein drugs have led to the development of platforms capable of improving their bioavailability. However, despite the progresses in drug delivery technologies, the success of oral delivery of insulin remains elusive and the disclosure of insulin mechanisms of absorption remains to be clarified. To overcome multiple barriers faced by oral insulin and to enhance the insulin permeability across the intestinal epithelium, here insulin-loaded alginate/dextran sulfate (ADS)-NPs were formulated and dual-coated with chitosan (CS) and albumin (ALB). The nanosystem was characterized by its pH-sensitivity and mucoadhesivity, which enabled to prevent 70% of in vitro insulin release in simulated gastric conditions and allowed a sustained insulin release following the passage to simulated intestinal conditions. The pH and time-dependent morphology of the NPs was correlated to the release and permeation profile of insulin. Dual CS/ALB coating of the ADS-NPs demonstrated augmented intestinal interactions with the intestinal cells in comparison to the uncoated-NPs, resulting in a higher permeability of insulin across Caco-2/HT29-MTX/Raji B cell monolayers. The permeability of the insulin-loaded ALB-NPs was reduced after the temperature was decreased and after co-incubation with chlorpromazine, suggesting an active insulin transport by clathrin-mediated endocytosis. Moreover, the permeability inhibition with the pre-treatment with sodium chlorate suggested that the interaction between glycocalix and the NPs was critical for insulin permeation. Overall, the developed nanosystem has clinical potential for the oral delivery of insulin and therapy of type 1 diabetes mellitus.

Administração oral de peptídeos e proteínas: II. Aplicação de métodos de microencapsulação

Choosing an appropriate microencapsulation method to improve the oral bioavailability of peptide drugs depends on the drug physico-chemical properties, operation conditions and selected polymers. Microencapsulation techniques and its application in peptide and protein oral delivery are reviewed. Natural polymers and techniques involving no harsh conditions such as extreme pH, high temperature and solvents use are the most important when encapsulating peptide drugs.

Why most oral insulin formulations do not reach clinical trials.

Oral insulin able to induce an efficient antihyperglycemic effect either to replace or complement diabetes mellitus therapy is the major goal of health providers, governments and diabetic patients. Oral therapy is associated not only with the desire to exclude needles from the daily routine of diabetic patient but also with the physiological provision of insulin they would get. Despite numerous efforts over the past few decades to develop insulin delivery systems, there is still no commercially available oral insulin. The reasons why the formulations developed to administer insulin orally fail to reach clinical trials are critically discussed in this review. The principal features of nanoformulations used so far are also addressed as well as the undergoing clinical trials.

Administração oral de peptídios e proteínas: I. Estratégias gerais para aumento da biodisponibilidade oral

There are hundreds of peptides and proteins clinically relevant. The difficulties associated with their oral administration have been responsible for the major efforts in developing ways to improve oral bioavailability. Both these subjects are described in this review. The potentiality of microencapsulation presents this technique as a privileged approach for the oral delivery of peptide and protein drugs.

Impact of the in vitro gastrointestinal passage of biopolymer-based nanoparticles on insulin absorption

Although the oral administration of insulin is recognized as the safest and most attractive, insulin oral bioavailability is usually reduced due to the susceptibility to acidic and enzymatic degradation in the gastrointestinal (GI) tract and intrinsic low intestinal permeability. Nanoencapsulation of insulin is, thus, foreseen as a promising approach to overcome most of these drawbacks. The effect of the GI environment on the aggregation of alginate/dextran sulfate-based nanometric-sized particles, uncoated or double-coated with chitosan and albumin, and its further influence on insulin release and permeability at the cellular level, was investigated in vitro. The swelling and aggregation behavior of NPs in gastric conditions was accompanied by the prevention of insulin release. In intestinal conditions, the fast dissolution of uncoated NPs was responsible for a wide size distribution and for a burst release of insulin, while the size stability provided by albumin/chitosan-coating led to sustained release. Chitosan/albumin-coated NPs were able to significantly increase the permeability of insulin across the cell-based engineered intestinal models, further enhanced by the presence of a mucus layer and M-like cells. The influence of these models on insulin permeability was compared to the curve that better adjusted to the mathematical kinetics of insulin release from these biopolymeric-NPs. Thus, a correlation between the size behavior of NPs upon passage in the GI tract and both insulin release profile and permeation across intestinal in vitro models was addressed. These results provide proof-of-concept evidence that the GI passage of NPs has a major influence on the oral absorption of macromolecules.

In vivo biodistribution of antihyperglycemic biopolymer-based nanoparticles for the treatment of type 1 and type 2 diabetes

Graphical abstract Biodistribution of insulin‐loaded alginate/dextran sulfate‐based nanoparticles dual coated with chitosan and 99mTc‐albumin after oral administration. The comparison of the oral antihyperglycemic effect between type 1 and type 2 diabetic models after the intraperitoneal glucose tolerance test revealed that the effect lasted longer in the type 1 model and that the glycemia increased to a greater extend in the type 2 model. No caption available. Abstract This study aimed to assess the biodistribution of antihyperglycemic insulin‐loaded alginate/dextran sulfate‐based nanoparticles dual coated with chitosan and technetium‐99m‐albumin (99mTc‐BSA) after oral administration. The oral administration of 50 IU/kg insulin‐loaded nanoparticles to type 1 diabetic rats showed prolonged antihyperglycemic effects up to 12 h and relative pharmacological availability of 5.04% comparing to the subcutaneous administration. The oral antihyperglycemic effect was further compared between type 1 and type 2 diabetic models by the intraperitoneal glucose tolerance test, revealing that the effect lasted longer in the type 1 diabetic model. 99mTc‐BSA revealed to be a good nanoparticles’ tracer since there was no systemic absorption and 99mTc‐BSA‐nanoparticles were capable of increasing their residence time in the intestinal epithelium of balb‐c mice when compared with 99mTc‐BSA biodistribution. Thus, this biopolymeric‐based delivery nanoparticulate system is a promising tool for the therapy of type 1 and type 2 diabetic individuals and prevention of T1D.

Satirical Discourse and Intertextuality: The Dialogic Construction of Satirical Authority in Die Fackel

The essay focuses on an analysis of the dialogic nature of Karl Krauss writing as an essential device for the construction of the identity and authority of the satirical self. Several exemples are given and discussed, drawing in particular from Shakespeare quotations and allusions in Die Fackel.The essay focuses on an analysis of the dialogic nature of Karl Krauss writing as an essential device for the construction of the identity and authority of the satirical self. Several exemples are...

Administração oral de peptídios e proteínas: III. Aplicação à insulina

A insulina e um peptideo biologicamente ativo, normalmente administrado por via subcutânea, pelos obstaculos que se colocam a sua administracao oral. O desenvolvimento de uma forma farmaceutica passivel de ser administrada oralmente tem sido razao de uma investigacao persistente, acentuada na ultima decada, conforme e descrito. As estrategias utilizadas tem sido muito variadas, a saber, a utilizacao de inibidores das enzimas proteoliticas, promotores da absorcao, modificacao quimica e formulas farmaceuticas especificas, como sistemas de particulas, emulsoes, sistemas de liberacao targeting e sistemas bioadesivos. Embora ainda nenhuma abordagem tenha sido suficientemente eficaz, os resultados sao encorajadores. A microencapsulacao e, em particular, os metodos que utilizam polimeros naturais, mostram-se promissores neste proposito, pelas caracteristicas vantajosas que apresentam.