Marlene Lopes

Intestinal absorption of insulin nanoparticles: Contribution of M cells

UNLABELLED Nanodelivery systems have been extensively studied as a strategy for the effective treatment of type 1 diabetes in animal models. Nanoparticle formulations have been shown to contribute to increased intestinal absorption of insulin according to established pathways. It is important to determine whether intestinal absorption of the hormone, specifically occurs through a privileged pathway that is favored because of particular properties of the nanoparticles. Confocal fluorescence microscopy has revealed that nanoparticles-based oral insulin delivery in intestinal tissues causes their accumulation in Peyers patches. To quantify the preponderance of M cells involved in the overall absorption of insulin in the intestine, in vitro and in vivo results of insulin-loaded nanoparticles were analyzed and criticized based on the utilized method and whether it has translational impact for the treatment of diabetes in humans. The degree of insulin nanoparticles uptake will be interpreted for its effectiveness in the prevention/treatment of other pathologies. FROM THE CLINICAL EDITOR This study investigates nano-formulation based insulin delivery through the oral route, with particular attention to their accumulation in Peyer patches and the role of M-cells in their absorption. While oral delivery of insulin would be an important step from the standpoint of convenience, accurate dosing and issues of potential toxicity need to be considered before clinical translation of this method.

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.

Probing insulin bioactivity in oral nanoparticles produced by ultrasonication-assisted emulsification/internal gelation

Alginate–dextran sulfate-based particles obtained by emulsification/internal gelation technology can be considered suitable carriers for oral insulin delivery. A rational study focused on the emulsification and particle recovery steps was developed in order to reduce particles to the nanosize range while keeping insulin bioactivity. There was a decrease in size when ultrasonication was used during emulsification, which was more pronounced when a cosurfactant was added. Ultrasonication add-on after particle recovery decreased aggregation and led to a narrower nanoscale particle-size distribution. Insulin encapsulation efficiency was 99.3%±0.5%, attributed to the strong pH-stabilizing electrostatic effect between insulin and nanoparticle matrix polymers. Interactions between these polymers and insulin were predicted using molecular modeling studies through quantum mechanics calculations that allowed for prediction of the interaction model. In vitro release studies indicated well-preserved integrity of nanoparticles in simulated gastric fluid. Circular dichroism spectroscopy proved conformational stability of insulin and Fourier transform infrared spectroscopy technique showed rearrangements of insulin structure during processing. Moreover, in vivo biological activity in diabetic rats revealed no statistical difference when compared to nonencapsulated insulin, demonstrating retention of insulin activity. Our results demonstrate that alginate–dextran sulfate-based nanoparticles efficiently stabilize the loaded protein structure, presenting good physical properties for oral delivery of insulin.

Intestinal uptake of insulin nanoparticles: facts or myths?

The oral route is the most suitable and physiological delivery route. Oral insulin delivery would minimize the health hazard implied in repeated injection, surpass complications arising from the need for sterile techniques associated with parenteral formulations and provide better glucose homeostasis. However, it is limited by various physiological barriers and still remains a scientific challenge. The desire to deliver insulin by the oral route in a conveniently and effectively way has led to the intense investigation of new delivery systems. Nanodelivery systems have been proposed to enhance the bioavailability of insulin after oral administration. This review article describes the gastrointestinal barriers to oral insulin delivery, including chemical, enzymatic and absorption barriers. The potential transport mechanisms of insulin delivered by nanoparticles across the intestinal epithelium are also addressed. Finally, how nanoparticles characteristics affect insulin pharmacological activity and bioavailability is discussed.

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.

Preparation methods and applications behind alginate-based particles

ABSTRACT Introduction: Alginate-based particles have emerged as one of the most extensively searched drug delivery platforms due to their inherent properties, including good biocompatibility and biodegradability. Moreover, the low price, easy availability, natural origin, versatility and sol-gel transition properties, make alginate an ideal candidate to produce particles with different applications. Several techniques have been developed and optimized to prepare microparticles and nanoparticles in order to achieve more rational, coherent, efficient and cost-effective procedures. Alginate represents a suitable choice concerning delivery systems’ safety, and therefore alginate-based particles have shown to be useful in the field of drug delivery with a special focus on biological encapsulants. Area covered: This review will provide an overview of alginate-based delivery systems, covering the innovative preparation methods of the last decade, the advantages and disadvantages of the most used methods, their wide diversity of applications and safety concerns. Expert opinion: The progression of nanotechnology over the last decades has stimulated the refinement of former microencapsulation methods and the exploration of new approaches towards the submicron scale with increased attention being focused on the safety of nanoparticles and product performance. Therefore, the design and optimization of the preparation methods of alginate-based microparticles and nanoparticles as well as their nontoxicity, biocompatibility and biodegradability to reach the desired application have been widely explored.

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.

Development of a Doxazosin and Finasteride Transdermal System for Combination Therapy of Benign Prostatic Hyperplasia

The treatment of benign prostatic hyperplasia can be accomplished by the use of different drugs including, doxazosin, an α-1 adrenergic antagonist, and finasteride (FIN), a 5-α reductase inhibitor. Traditionally, treatments using these drugs have been administered as either a mono or combination therapy by the oral route. A transdermal delivery system optimized for doxazosin and FIN combination therapy would provide increased patient adherence and facilitate dose adjustment. Doxazosin base (DB) was prepared from doxazosin mesylate and characterized together with FIN, by X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR). The permeation enhancers, azone and lauric acid, and the gelling agents, hydroxypropyl cellulose (HPC) and Poloxamer 407 (P407), were evaluated to determine their ability to promote in vitro permeation of drugs through the pig ear epidermis. Successful preparation of DB was confirmed by evaluating the XRD, DSC, and NMR patterns and in vitro studies revealed that 3% (w/w) azone was the best permeation enhancer. When P407 gel was compared with HPC gel, it showed reduced lag time and promoted higher permeation of both drugs. This may be because of the interactions of the former with the stratum corneum, which disorganizes the lipid structure and consequently promotes higher drug permeation.