Oral Insulin Delivery Research Articles

Surface charge triggered intestinal epithelial tight junction opening based on chitosan nanoparticles for insulin oral delivery

Surface charge triggered intestinal epithelial tight junction opening based on chitosan nanoparticles for insulin oral delivery

Design and development of a biocompatible montmorillonite PLGA nanocomposites to evaluate in vitro oral delivery of insulin

We are introducing design, development and preliminary feasibility study of nanocomposites (made of Food and drug administration approved layered montmorillonite (Mt) and biodegradable polymer Poly lactic-co-glycolic acid (PLGA)), as a vehicle for oral administration of insulin. A systematic study on the variation of Mt-PLGA ratio was focused to reduce particles to the submicron size range while maintaining insulin's bioactivity. The synthesized Insulin-Mt-PLGA nanocomposites were successfully characterized with various techniques and compared with the Insulin-PLGA nanoparticles for their drug content, physico-chemical properties, in-vitro insulin release profile and cytotoxicity. High encapsulation efficiency, desirable particle size, prolonged gastric residence time, extended release of insulin in simulated gastrointestinal fluid and biocompatibility indicated the effectiveness of presence of Mt in the synthesized Mt-PLGA nanocomposites for the oral delivery of insulin. Thus, on the basis of our preliminary research findings, it could be concluded that the developed biocompatible Insulin-Mt-PLGA nanocomposites with double functionality of low pH stability and mucoadhesivity may offers promise to overcome the difficulties associated with the oral drug delivery of insulin.

Bacillus-produced surfactin for intranasal delivery of insulin in diabetic mice

Previous studies have shown that Bacillus-produced surfactin (SFN) can be used for oral delivery of insulin (INS). To improve the bioavailability of INS, we determined the effects of SFN on intranasal delivery of INS in diabetic mice. Combinations of SFN and INS at different doses were used for intranasal administration of diabetic mice. The plasma levels of glucose and INS were determined at various time intervals after intranasal administration, and then, the hypoglycemic effects and relative bioavailability of INS were calculated. Glucose tolerance test was performed to determine the effects of intranasal delivery of INS plus SFN on the control of glucose levels. Diabetic mice were also intranasally administered with the INS and SFN combo for 7 days to determine the short-term stability of this formulation for controlling blood glucose levels. A combination of 20 IU/kg INS and 1.6 mg/kg SFN achieved the best hypoglycemic effects for intranasal administration, with a maximal hypoglycemic rate of 29.59% and a maximal blood INS concentration of 45.47 μIU/ml 2 h after administration. As a result, a relatively increased bioavailability of 8.55% was achieved. Glucose tolerance test showed that intranasal delivery of INS plus SFN could effectively control the blood glucose levels after the influx of glucose. Furthermore, intranasal INS plus SFN could be used for controlling blood glucose daily for a short term. Histological evaluation showed no changes in the morphology of the nasal mucosa after exposure to SFN plus INS. SFN is potentially useful for intranasal delivery of INS to control blood glucose levels.

A cell-penetrating peptide mediated chitosan nanocarriers for improving intestinal insulin delivery

To overcome barriers for oral delivery of insulin, the chitosan(CS)-based nanocarriers with a novel cell penetrating peptide (SAR6EW) have been prepared and evaluated in this study. Characterization measurements showed that SAR6EW/CS/insulin-NPs displayed global particles with smooth surfaces and an average diameter about 150nm. The entrapment efficiency and loading rates of insulin were 75.36% and 7.58%, respectively. Insulin could be released constantly from SAR6EW/CS/insulin-NPs in vitro. Furthermore, SAR6EW/CS/insulin-NPs could facilitate the uptake of insulin and induce a significantly higher internalization of insulin via adding clathrin and caveolae mediated endocytosis. In addition, in vivo hypoglycemic studies showed that orally administrated SAR6EW/CS/insulin-NPs produced a better hypoglycemic effect as compared with CS/insulin-NPs in diabetic rats. Meanwhile, no significant cytotoxicity of the nanoparticles was observed. In conclusion, SAR6EW-mediated chitosan nanocarriers showed sufficient effectiveness for oral delivery of insulin. This delivery system is also promising for the delivery of other protein drugs by oral administration.

Biomimetic insulin-imprinted polymer nanoparticles as a potential oral drug delivery system.

In this study, we investigate molecularly imprinted polymers (MIPs), which form a three-dimensional image of the region at and around the active binding sites of pharmaceutically active insulin or are analogous to b cells bound to insulin. This approach was employed to create a welldefined structure within the nanospace cavities that make up functional monomers by cross-linking. The obtained MIPs exhibited a high adsorption capacity for the target insulin, which showed a significantly higher release of insulin in solution at pH 7.4 than at pH 1.2. In vivo studies on diabetic Wistar rats showed that the fast onset within 2 h is similar to subcutaneous injection with a maximum at 4 h, giving an engaged function responsible for the duration of glucose reduction for up to 24 h. These MIPs, prepared as nanosized material, may open a new horizon for oral insulin delivery.

Selenium nanoparticles as versatile carriers for oral delivery of insulin: Insight into the synergic antidiabetic effect and mechanism

Oral insulin delivery has been plagued by limited bioavailability. This work reports selenium nanoparticles (SeNPs) for oral insulin delivery to overcome the absorption barrier. Insulin-loaded SeNPs (INS-SeNPs) were fabricated by ionic cross-linking/in situ reduction and characterized by particle size and drug entrapment. The resultant INS-SeNPs were 120nm around in particle size with high drug loading. INS-SeNPs exhibited controllable insulin release and outstanding stability in the digestive fluids. INS-SeNPs caused a significant hypoglycemic effect in both normal and diabetic rats. The pharmacological bioavailability was up to 9.15% relative to subcutaneous insulin. Likewise, the blood insulin evidently increased in terms of INS-SeNPs. Ex vivo intestinal imaging and cell experiments showed the excellent performance of INS-SeNPs in intestinal permeability. INS-SeNPs could alleviate oxidative stress, improve pancreatic islet function, and promote glucose utilization. Our study provides proof of concept for using SeNPs to orally deliver insulin, jointly potentiating the antidiabetic effect.

Preparation of polyurethane–alginate/chitosan core shell nanoparticles for the purpose of oral insulin delivery

Waste polyethylene terephthalate (PET) is depolymerized through glycolysis and the glycolyzed product, bis (2-hydroxyethylene) terephthalate (BHET) is utilized in the synthesis of polyurethane as diol. Polyurethane (PU) is incorporated in a core- shell nanoparticle formulation along with alginate (ALG) and chitosan (CS) to develop an efficient oral insulin delivery vehicle. Fourier transform infrared (FT-IR) spectrums of the polyurethane-alginate/chitosan (PU-ALG/CS) nanoparticles confirm the presence of all elements distinctly. Nanoparticles of average particle size 90–110nm are clearly visible from the images of scanning electron microscope (SEM) and transmission electron microscope (TEM). Unique characteristics of insulin loaded PU-ALG/CS nanoparticles are noticed in both in vitro and in vivo studies. More than 90% insulin encapsulation efficiency, sustained swelling, controlled insulin release from mucoadhesive nanoparticle formulation are the major causes of long term hypoglycaemic effects in diabetic mice and improved insulin bioavailability (10.36%). PU-ALG/CS nanoparticles are also found to be safe, according to the acute toxicity studies.

Controlled swelling and in vitro release of insulin from konkoli grafted polymethylacrylaminde hydrogel

The extended study of konkoli grafted polymethylacrylaminde (KG-g-poly (MAAm) hydrogel synthesized in our earlier work from methacrylamide (MAAm) grafted and N,N-methylenebisacrylamide (N,N-MBAAm) crosslinked Konkoli ( Maesopsis eminni ) galactomannan (KG), is necessary to establish its potential application as an oral insulin delivery system. In this study, the kg-g-poly (MAAm) Hydrogel swelling in typical pH media show an initial rapid swelling before stabilizing. The hydrogel attains its parabolic peak swelling in distill water (pH = 7). Swelling rises from a lower pH medium (pH = 2.2), and in a medium with a slight pH above this (pH = 7.4), swelling starts dropping. Comparing the media for the insulin release studies, the cumulative release drops to its parabolic trough in the distill water medium (pH = 7). A higher cumulative release was recorded at a lower pH (pH = 2.2), and the highest cumulative release was recorded at a higher pH (pH = 7.4). The kinetics and mechanisms of these processes were presented while using the descriptive statistic of regression to fit the results from the processes to a power law. The release of insulin from kg-g-poly (MAAm) Hydrogel was also shown to increase with increase in glucose concentration in the media with an initial rapid release in all solutions, while in a typical intestinal pH media range, higher release at all concentrations was recorded at pH = 6.8.

Preparation of poly(lactic-co-glycolic acid) and chitosan composite nanocarriers via electrostatic self assembly for oral delivery of insulin

To improve insulin bioavailability and overcome multiple barriers for oral delivery of insulin, the composite nanocarriers (PLGA/FA-CS) prepared from poly(lactide-co-glycoside) (PLGA) and folic acid modified chitosan (FA-CS) were fabricated via electrostatic self-assembly method. The resultant composite nanocarriers exhibited low cytotoxicity against HT-29 cells and excellent stability against protein solution. The chemical stability of loaded insulin against digestive enzyme were established in presence of simulated gastric fluid (SGF) containing pepsin and simulated intestinal fluid (SIF) containing pancreatin, respectively. The uptake behavior of HT-29 cells was evaluated by confocal laser scanning microscope. After oral administration to the diabetic rats, an effective hypoglycemic effect was obtained compared with subcutaneous injection of insulin. This work suggests that the as-prepared composite nanocarriers may be a promising drug delivery system for oral administration of insulin and other biomacromolecules.

Scalable fabrication of size-controlled chitosan nanoparticles for oral delivery of insulin.

Controlled delivery of protein would find diverse therapeutic applications. Formulation of protein nanoparticles by polyelectrolyte complexation between the protein and a natural polymer such as chitosan (CS) is a popular approach. However, the current method of batch-mode mixing faces significant challenges in scaling up while maintaining size control, high uniformity, and high encapsulation efficiency. Here we report a new method, termed flash nanocomplexation (FNC), to fabricate insulin nanoparticles by infusing aqueous solutions of CS, tripolyphosphate (TPP), and insulin under rapid mixing condition (Re>1600) in a multi-inlet vortex mixer. In comparison with the bulk-mixing method, the optimized FNC process produces CS/TPP/insulin nanoparticles with a smaller size (down to 45nm) and narrower size distribution, higher encapsulation efficiency (up to 90%), and pH-dependent nanoparticle dissolution and insulin release. The CS/TPP/insulin nanoparticles can be lyophilized and reconstituted without loss of activity, and produced at a throughput of 5.1gh-1 when a flow rate of 50mLmin-1 is used. Evaluated in a Type I diabetes rat model, the smaller nanoparticles (45nm and 115nm) control the blood glucose level through oral administration more effectively than the larger particles (240nm). This efficient, reproducible and continuous FNC technique is amenable to scale-up in order to address the critical barrier of manufacturing for the translation of protein nanoparticles.

Design of Insulin-Loaded Nanoparticles Enabled by Multistep Control of Nanoprecipitation and Zinc Chelation.

Nanoparticle (NP) carriers provide new opportunities for controlled delivery of drugs, and have potential to address challenges such as effective oral delivery of insulin. However, due to the difficulty of efficiently loading insulin and other proteins inside polymeric NPs, their use has been mostly restricted to the encapsulation of small molecules. To better understand the processes involved in encapsulation of proteins in NPs, we study how buffer conditions, ionic chelation, and preparation methods influence insulin loading in poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-PEG) NPs. We report that, although insulin is weakly bound and easily released from the NPs in the presence of buffer ions, insulin loading can be increased by over 10-fold with the use of chelating zinc ions and by the optimization of the pH during nanoprecipitation. We further provide ways of changing synthesis parameters to control NP size while maintaining high insulin loading. These results provide a simple method to enhance insulin loading of PLGA-PEG NPs and provide insights that may extend to other protein drug delivery systems that are subject to limited loading.

Intestinal micropatches for oral insulin delivery

Diabetes mellitus has become a major public health issue that has almost reached epidemic proportions worldwide. Injectable insulin has been typically utilized for the management of this chronic disease. However, lack of patient compliance with injectable formulations has spurred the development of oral insulin formulations, which although appealing, face several delivery challenges. We have developed novel mucoadhesive intestinal patches, several hundred micrometers in dimension (micropatches) that address the challenges of oral insulin delivery. The micropatches adhere to the intestinal mucosa, release their drug load rapidly within 30 min and are effective in lowering blood glucose levels in vivo. When insulin-loaded micropatches were administered with a permeation enhancer and protease inhibitor, a peak efficacy of 34% drop in blood glucose levels was observed within 3 h. Efficacy further improved to 41% when micropatches were administered in multiple doses. Here, we describe the design of micropatches as an oral insulin formulation and report their in vivo efficacy.

NOVEL FORMULATION STRATEGIES FOR INSULIN DELIVERY

Insulin is a hormone made by the pancreas that allows your body to use sugar (glucose) from carbohydrates in the food that you eat for energy or to store glucose for future use. Successful oral insulin delivery involves overcoming the enzymatic and physical barriers. Several companies across the globe are developing oral insulin based on different technology platforms. Insulin has been encapsulated in nanoparticles by mucoadhesive polymers such as chitosan, poly (lacticco-glycolic acid) (PLGA), and alginate which prevent enzymatic degradation and allow absorption across the epithelial layer in Peyer’s patches. Keywords : Novel Formulation Strategies, Insulin, hyperglycemia, Nanosphere-based oral insulin delivery

Surfactin variants for intra-intestinal delivery of insulin

Surfactin is a Bacillus-produced natural lipopeptide, which can overcome the epithelial cell barriers for orally delivering insulin, but its ability to promote uptake of insulin by the intestine need to be further improved for a higher oral bioavailability. Here, we designed and synthesized several surfactin variants to improve its ability for oral delivery of insulin. Firstly, we replaced Glu with Gln in surfactin for decreasing its negative charges, but found this replacement weakened its ability to orally delivery insulin. We further chemically synthesized surfactin variant by replacing its fatty acid chain (C15) with a shortened one (C14), and found this replacement did not influence its ability to orally deliver insulin. Lastly, we replaced its amino acids (Leu) with more hydrophobic ones (Ile), and found the replacement could significantly improve its ability to deliver insulin, with a maximal blood glucose decrease to 27.33% of the initial level and an insulin bioavailability of 18.25%. We also replaced its amino acids of Leu with Val, and Val with Ile, and found this replacement could also significantly improve its ability to deliver insulin with a maximal blood glucose decrease to 18.36% of the initial level and a high insulin bioavailability of 26.32% in diabetic mice. Further analysis by CD, we found the surfactin variants with more hydrophobic amino acid residuals significantly induced insulin from rigid (α-helix) to flexible structure (β-sheet and random coil), that is favorable for insulin to permeate across the intestine epithelial membrane. Collectively, surfactin variants with more hydrophobicity are very potential for delivery of insulin in the everyday control of blood glucose.

Development of poly(hydroxyethyl methacrylate) nanogel for effective oral insulin delivery

Because of uncomfortable, painful and even deleterious effects of daily injection of insulin, extensive efforts are being made worldwide for developing noninvasive drug delivery systems, especially via the oral route. In this study, we synthesized hydroxyethyl methacrylate (HEMA) nanogel via emulsion polymerization method. The morphology and stability of the nanogel were characterized by scanning electronic microscope and dynamic light scattering. In vivo results showed the soft HEMA nanogel had longer half-live in the body circulation and exhibited almost negligible uptake by the macrophage cells as compared with blank cells. For the FITC-dextran tracking for intestinal penetration, the results indicated that the FITC-dextran in the soft nanogel penetrated faster from the inner side of the abdominal segment, which explained why the soft HEMA nanogel could promote intestinal absorption of encapsulated insulin. In vivo delivery of insulin encapsulated in the soft HEMA nanogel sustained blood glucose control for 12 h, and the overall bioavailability of administrated insulin was much higher than free insulin. Our results showed that the insulin-loaded HEMA nanogel was able to efficiently control blood glucose as a delivery system, suggesting the HEMA nanogel using emulsion polymerization could be an alternative carrier for oral insulin delivery.

Potential of single cationic amino acid molecule “Arginine” for stimulating oral absorption of insulin

We have reported that cell-penetrating peptides, such as oligoarginine, act as powerful absorption enhancers for the development of oral insulin delivery systems. However, the minimal essential sequence of oligoarginine that stimulates intestinal insulin absorption remains unclear. Therefore, the present study was conducted to clarify this minimum sequence of oligoarginine and to examine the effect of single cationic amino acid arginine on the intestinal and oral absorption of insulin. The results demonstrated that a remarkable enhancement of intestinal insulin absorption was observed after coadministration of insulin with l-arginine. The efficacy of d-forms of oligoarginine/arginine tended to decrease with a decreasing number of amino acid residues, whereas the effect of l-arginine was the strongest of any of the l-forms of oligoarginine/arginine. Interestingly, the effect of l-arginine was stronger than that of d-arginine at various concentrations, and the effect of other cationic amino acids such as lysine and histidine was relatively lower than that of arginine. In addition, no leakage of lactate dehydrogenase from the intestinal epithelium and no change in the transepithelial electrical resistance of a Caco-2 cell monolayer were detected after administration of l-arginine as the single amino acid, which suggests that there were no undesirable effects of arginine on the integrity of cell membranes and paracellular tight junctions. Oral administration study in mice demonstrated that the stronger hypoglycemic effects were observed after coadministration of insulin with l-arginine. In this study, we found that arginine is a key cationic amino acid for delivering insulin across intestinal epithelial barriers and hopefully accelerating the clinical development of oral insulin delivery systems.

Secretory expression and surface display of a new and biologically active single-chain insulin (SCI-59) analog by lactic acid bacteria.

Insulin plays an important role in drug therapies for diabetes mellitus and as the main route of insulin delivery, subcutaneous injection may cause local discomfort, hypoglycemia, hyperinsulinemia, and patient non-compliance. Therefore, oral delivery of insulin is more preferred. However, there is a low bioavailability due to insulin degradation by proteolytic enzymes and severe pH conditions along the gastrointestinal tract. In order to use the food-grade bacteria lactic acid bacteria (LAB) as oral delivery vehicles, a new and bioactive single-chain insulin (SCI-59) analog, containing the insulin B- and A-chains connected by an eight-residue linker (RSRGLPFR), was secretory expressed in Lactococcus lactis NZ3900 without using an antibiotic resistance gene and displayed onto the surface of various non-viable bacteria (NVBs) without genetic modification. Both the free SCI-59 and SCI-59 displayed on the surface of NVBs are biologically active as assayed by their ability to stimulate Akt signaling in differentiated 3T3-L1 adipocytes. Modification of the pH of the medium by NaOH addition at early time during induction can enhance the bioactivity of SCI-59. The C-terminal fused anchoring domain, three LysM repeats, does not affect the formation of disulfide bonds and/or the folding of SCI-59, and SCI-59 could be exposed properly and fully when SCI-59-3LysM bound to the surface of NVBs. Compared to the free form SCI-59, SCI-59 displayed on the surface of NVBs is more stable in simulate gastric juice. It may open new prospects for possible oral treatments of diabetes using live LAB secreting or NVBs carrying bioactive SCI analogs.

Formation and stability of W/O microemulsion formed by food grade ingredients and its oral delivery of insulin in mice

Water in oil (W/O) microemulsions are potential vehicles to deliver insulin orally. In this study, we characterized the formation and stability of W/O microemulsions formed by food grade ingredients, including different intrinsic components (oil source, surfactant, and cosurfactant). Stable microemulsions were formed with Span80-Tween80 (S80T80) (HLB=6) or PEG-7 hydrogenated castor oil (PEG-7) (HLB=5) as surfactants and isopropyl myristate as the oil phase under mild processing conditions. The W/O microemulsions showed good thermodynamic stability in the temperature range 20–40°C. S80T80 microemulsions were stable to the addition of NaCl. Peak glucose response to glucose tolerance test was dramatically decreased by the insulin loaded W/O microemulsions when administered to mice, and was further decreased to 1/3 of the control when sodium taurocholate or trypsin inhibitor was incorporated into the aqueous phase. This study shows that insulin in a W/O microemulsion remains bioactive during processing and digestion, and is bioavailable to the host animal.

Oral Insulin: Current Status, Challenges, and Future Perspectives.

Oral delivery of insulin is one of the most promising and anticipated areas in the treatment of diabetes, primarily because it may significantly improve the quality of life of diabetics who receive insulin regularly. Several problems have been reported regarding the subcutaneous delivery of insulin, ranging from cardiovascular complications to weight gain. One of the approaches to overcoming these issues is to administer insulin through the oral route. However, there are several challenges in developing an oral route for insulin delivery; insulin has extremely poor bioavailability and a low diffusion rate through the mucus layer. A wide range of oral insulin delivery techniques have recently been researched, ranging from nanoparticles to liposomes, self-emulsifying systems, and hydrogels. These techniques have shown promising potential in the oral delivery of insulin. This review considers the current literature on the advances and challenges in the development of oral insulin.

Poly (PEGDMA-MAA) copolymeric micro and nanoparticles for oral insulin delivery : A molecular mechanistic revisit

Poly(ethylene glycol) dimethacrylate (PEGDMA) and methacrylic acid (MAA) based micro and nanoparticles were prepared for oral insulin delivery. The reactional profiles of MAA, PEGDMA and PEGDMA-MAA were elucidated using molecular mechanics energy relationships (MMER) in vacuum and in a solvated system by exploring the spatial disposition of different concentrations of polymers with respect to each other. Furthermore, the incorporation of insulin within the polymeric matrix was modeled using connolly molecular surfaces. The computational results corroborated with the experimental and analytical data. The ability to effectively control blood glucose level coupled with the non toxic behavior of the nanoparticles renders them a potential candidate for insulin delivery.