Design of oral insulin delivery systems

Revolutionizing type 1 diabetes management: Exploring oral insulin and adjunctive treatments

Type 1 diabetes (T1D) is a chronic autoimmune condition that affects millions of people worldwide. Insulin pumps or injections are the standard treatment options for this condition. This article provides a comprehensive overview of the several type 1 diabetes treatment options, focusing on oral insulin. The article is divided into parts that include immune-focused treatments, antigen vaccination, cell-directed interventions, cytokine-directed interventions, and non-immunomodulatory adjuvant therapy. Under the section on non-immunomodulatory adjunctive treatment, the benefits and drawbacks of medications such as metformin, amylin, sodium-glucose cotransporter inhibitors, glucagon-like peptide-1 receptor agonists (GLP-1 Ras), and verapamil are discussed. The article also discusses the advantages of oral insulin, including increased patient compliance and more dependable and regular blood sugar control. However, several variables, including the enzymatic and physical barriers of the digestive system, impair the administration of insulin via the mouth. Researchers have looked at a few ways to get over these challenges, such as changing the structure of the insulin molecule, improving absorption with the use of absorption enhancers or nanoparticles, and taking oral insulin together with other medications. Even with great advancements in the use of these treatment strategies, T1D still needs improvement in the therapeutic difficulties. Future studies in these areas should focus on creating tailored immunological treatments, looking into combination medications, and refining oral insulin formulations in an attempt to better control Type 1 Diabetes. The ultimate objective is to create accurate, customized strategies that will enhance glycemic management and the quality of life for individuals with the condition.

Tabletized Nanomedicine: From the Current Scenario to Developing Future Medicine

The limitations of conventional therapeutic treatments prevailed in the development of nanotechnology-based medical formulations, termed nanomedicine. Nanomedicine is an advanced medicine that often consists of therapeutic agent(s) embedded in biodegradable or biocompatible nanomaterial-based formulations. Among nanomedicine approaches, tablet (oral) nanomedicine is still under development. In tabletized nanomedicine, the dynamic interplay between nanoformulations and the intricate milieu of the gastrointestinal tract simulates a pivotal role, particularly accentuating the influence exerted upon the luminal, mucosal, and epithelial cells. In this work, we document the perspectives and opportunities of nanoformulations toward the development of tabletized nanomedicine. This review also unveils the notion of integrating nanomedicine within a tablet formulation, which facilitates the controlled release of drugs, biomolecules, and agent(s) from the formulation to achieve a better therapeutic response. Finally, an attempt was made to explore current trends in nanomedicine technology such as bacteriophage, probiotic, and oligonucleotide tabletized nanomedicine and the combination of nanomedicine with imaging agents, i.e., nanotheranostics.

Recent Advances in Drug Delivery Systems Targeting Insulin Signalling for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by the accumulation of neurofibrillary tangles and amyloid-β plaques. Recent research has unveiled the pivotal role of insulin signaling dysfunction in the pathogenesis of AD. Insulin, once thought to be unrelated to brain function, has emerged as a crucial factor in neuronal survival, synaptic plasticity, and cognitive processes. Insulin and the downstream insulin signaling molecules are found mainly in the hippocampus and cortex. Some molecules responsible for dysfunction in insulin signaling are GSK-3β, Akt, PI3K, and IRS. Irregularities in insulin signaling or insulin resistance may arise from changes in the phosphorylation levels of key molecules, which can be influenced by both stimulation and inactivity. This, in turn, is believed to be a crucial factor contributing to the development of AD, which is characterized by oxidative stress, neuroinflammation, and other pathological hallmarks. Furthermore, this route is known to be indirectly influenced by Nrf2, NF-κB, and the caspases. This mini-review delves into the intricate relationship between insulin signaling and AD, exploring how disruptions in this pathway contribute to disease progression. Moreover, we examine recent advances in drug delivery systems designed to target insulin signaling for AD treatment. From oral insulin delivery to innovative nanoparticle approaches and intranasal administration, these strategies hold promise in mitigating the impact of insulin resistance on AD. This review consolidates current knowledge to shed light on the potential of these interventions as targeted therapeutic options for AD.

An overview of oral insulin delivery strategies (OIDS)

Despite tremendous efforts, the world continues its fight against the common chronic disease-diabetes. Diabetes is caused by elevated glucose levels in the blood, which can lead to several complications like glaucoma, cataract, kidney failure, diabetic ketoacidosis, heart attack, and stroke. According to recent statistics, China, India, and the US rank at the top three positions with regards to the number of patients affected by diabetes. Ever since its discovery, insulin is one of the major therapeutic molecules that is used to control the disease in the diabetic population, worldwide. The most common route of insulin administration has been the subcutaneous route. However, the limitations associated with this route have motivated global efforts to explore alternative strategies to deliver insulin, including pulmonary, transdermal, nasal, rectal, buccal, and oral routes. Oral insulin delivery is the most convenient and patient-centered route. However, the oral route is also associated with numerous drawbacks that present significant challenges to the scientific fraternity. The human physiological system acts as a formidable barrier to insulin, limiting its bioavailability. The present review covers the major barriers against oral insulin delivery and explains formulation strategies that have been adopted to overcome these barriers. The review focuses on oral insulin delivery strategies (OIDS) for increasing the bioavailability of oral insulin, including nanoparticles, microparticles, nano-in-microparticles, hydrogels, tablets, capsules, intestinal patches, and use of ionic liquids. It also highlights some of the notable recent advancements and clinical trials in oral insulin delivery. This formulation based OIDS may significantly improve patient compliance in the treatment of diabetes.

Application of chitosan/alginate nanoparticle in oral drug delivery systems: prospects and challenges

Oral drug delivery systems (ODDSs) have various advantages of simple operation and few side effects. ODDSs are highly desirable for colon-targeted therapy (e.g. ulcerative colitis and colorectal cancer), as they improve therapeutic efficiency and reduce systemic toxicity. Chitosan/alginate nanoparticles (CANPs) show strong electrostatic interaction between the carboxyl group of alginates and the amino group of chitosan which leads to shrinkage and gel formation at low pH, thereby protecting the drugs from the gastrointestinal tract (GIT) and aggressive gastric environment. Meanwhile, CANPs as biocompatible polymer, show intestinal mucosal adhesion, which could extend the retention time of drugs on inflammatory sites. Recently, CANPs have attracted increasing interest as colon-targeted oral drug delivery system for intestinal diseases. The purpose of this review is to summarize the application and treatment of CANPs in intestinal diseases and insulin delivery. And then provide a future perspective of the potential and development direction of CANPs as colon-targeted ODDSs.

Polymeric nano-vesicles via intermolecular action to load and orally deliver insulin with enhanced hypoglycemic effect

Insulin (INS) was loaded into PEOP nano-vesicles via intermolecular actions and delivered orally through lymphatic transport with promising hypoglycemic effect.

Oral Drug Delivery Technologies-A Decade of Developments

Advanced drug delivery technologies, in general, enable drug reformulation and administration routes, together contributing to life-cycle management and allowing the innovator to maintain the product monopoly. Over the years, there has been a steady shift from mere life-cycle management to drug repurposing-applying delivery technologies to tackle solubility and permeability issues in early stages or safety and efficacy issues in the late stages of drug discovery processes. While the drug and the disease in question primarily drive the choice of route of administration, the oral route, for its compliance and safety attributes, is the most preferred route, particularly when it comes to chronic conditions, including pain, which is not considered a disease but a symptom of a primary cause. Therefore, the attempt of this review is to take a stock of the advances in oral delivery technologies that are applicable for injectable to oral transformation, improve risk-benefit profiles of existing orals, and apply them in the early discovery program to minimize the drug attrition rates.

Recent advances of polysaccharide-based nanoparticles for oral insulin delivery

Diabetes mellitus is a highly prevalent metabolic and chronic disease affecting millions of people in the world. The most common route of insulin therapy is the subcutaneous injection due to its low bioavailability and enzymatic degradation. The search for effective and high patient compliance insulin delivery systems has been a major challenge over many decades. The polysaccharide-based nanoparticles as delivery vehicles for insulin oral administration have recently attracted substantial interests. The present review highlights the recent advances on the development of nanoparticles prepared from polysaccharides, including chitosan, alginate, dextran and glucan, for oral delivery of insulin, overcoming multiple barriers in gastrointestinal tract. The aims of this review are first to summarize the strategies that have been applied in the past 5 years to fabricate polysaccharide-based nanoparticles for insulin oral delivery, and then to provide in-depth understanding on the mechanisms by which such nanoparticles protect insulin against degradation in the digestive tract and provide sustained release to enhance mucus permeation and transepithelial transport of insulin administered via oral route.

Development of resistant corn starch for use as an oral colon-specific nanoparticulate drug carrier

Starch is constituted of amylose and amylopectin. Debranching of amylopectin converts it into amylose thereby producing resistant starch which is known to be less digestible by the amylase. This study designed resistant starch using acid hydrolysis and heat-moisture treatment methods with native corn starch as the starting material. Both native and processed starches were subjected to Fourier transform infrared spectroscopy, X-ray diffractometry, differential scanning calorimetry and molecular weight analysis. They were nanospray-dried into nanoparticles with 5-fluorouracil as the drug of interest for colon cancer treatment. These nanoparticles were subjected to size, zeta potential, morphology, drug content and in vitro drug release analysis. Heat-moisture treatment of native corn starch enabled the formation of resistant starch through amylopectin debranching and molecular weight reduction thereby enhancing hydrogen bonding between the starch molecules at the amorphous phase and gelatinization capacity. The nanoparticles prepared from resistant starch demonstrated similar drug release as those of native starch in spite of the resistant starch had a lower molecular weight. The resistant starch is envisaged to be resistant to the digestive action of amylase in intestinal tract without the formed nanoparticles exhibiting excessively fast drug release in comparison to native starch. With reduced branching, it represents an ideal precursor for targeting ligand conjugation in design of oral colon-specific nanoparticulate drug carrier.

Can natural polymers assist in delivering insulin orally?

Diabetes mellitus is one of the most grave and lethal non communicable diseases. Insulin is normally used to medicate diabetes. Due to bioavailability issues, the most regular route of administration is through injection, which may pose compliance problems to treatment. The oral administration thus appears as a suitable alternative, but with several important problems. Low stability of insulin in the gastrointestinal tract and low intestinal permeation are some of the issues. Encapsulation of insulin into polymer-based particles emerges as a plausible strategy. Different encapsulation approaches and polymers have been used in this regard. Polymers with different characteristics from natural or synthetic origin have been assessed to attain this goal, with natural polymers being preferable. Natural polymers studied so far include chitosan, alginate, carrageenan, starch, pectin, casein, tragacanth, dextran, carrageenan, gelatine and cyclodextrin. While some promising knowledge and results have been gained, a polymeric-based particle system to deliver insulin orally has not been introduced onto the market yet. In this review, effectiveness of different natural polymer materials developed so far along with fabrication techniques are evaluated.

Stimuli-Responsive Delivery of Therapeutics for Diabetes Treatment

Diabetic therapeutics, including insulin and glucagon-like peptide 1 (GLP-1), are essential for diabetic patients to regulate blood glucose levels. However, conventional treatments that are based on subcutaneous injections are often associated with poor glucose control and a lack of patient compliance. In this review, we focus on the different stimuli-responsive systems to deliver therapeutics for diabetes treatment to improve patient comfort and prevent complications. Specifically, the pH-responsive systems for oral drug delivery are introduced first. Then, the closed-loop glucose-responsive systems are summarized based on different glucose-responsive moieties, including glucose oxidase (GOx), glucose binding protein (GBP), and phenylboronic acid (PBA). Finally, the on-demand delivery systems activated by external remote triggers are also discussed. We conclude by discussing advantages and limitations of current strategies, as well as future opportunities and challenges in this area.

Synthesis and characterization of insulin/zirconium phosphate@TiO2 hybrid composites for enhanced oral insulin delivery applications

In this work, a series of composites of insulin (Ins)/zirconium phosphate (ZrP) were synthesized by intercalation method, then, these composites were coated with TiO₂ by sol-gel method to prepare Ins/ZrP@TiO₂ hybrid composites and the drug release of the composites was investigated by using UV-Vis spectroscopy. Ins/ZrP (10, 30, 60 wt%) composites were prepared by intercalation of insulin into the ZrP layers in water. Then Ins/ZrP composites were coated with different amounts of TiO₂ (30, 50, 100 wt %) by using titanium tetra n-butoxide, as precursor. Formation of intercalated Ins/ZrP and Ins/ZrP@TiO₂ hybrid composites was characterized by FT-IR, FE-SEM, BET and XRD analysis. Zeta potential of the optimized Ins/ZrP@TiO₂ hybrid composite was determined -27.2 mV. Cytotoxic effects of the optimized Ins/ZrP@TiO₂ hybrid composite against HeLa and Hek293T cell lines were evaluated using MTT assay and the results showed that designed drug delivery system was not toxic in biological environment. Compared to the Ins/ZrP composites, incorporation of TiO₂ coating enhanced the drug entrapment considerably, and reduced the drug release. The Ins/ZrP composites without TiO₂ coating released the whole drug after 30 min in pH 7.4 (phosphate buffer solution) while the TiO₂-coated composites released the entrapped drug after 20 h. In addition to increasing the shelf life of hormone, this nanoencapsulation and nanocoating method can convert the insulin utilization from injection to oral and present a painless and more comfortable treatment for diabetics.

Sodium dodecyl sulfate/β-cyclodextrin vesicles embedded in chitosan gel for insulin delivery with pH-selective release

In an answer to the challenge of enzymatic instability and low oral bioavailability of proteins/peptides, a new type of drug-delivery vesicle has been developed. The preparation, based on sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD) embedded in chitosan gel, was used to successfully deliver the model drug-insulin. The self-assembled SDS/β-CD vesicles were prepared and characterized by particle size, zeta potential, appearance, microscopic morphology and entrapment efficiency. In addition, both the interaction of insulin with vesicles and the stability of insulin loaded in vesicles in the presence of pepsin were investigated. The vesicles were crosslinked into thermo-sensitive chitosan/β-glycerol phosphate solution for an in-situ gel to enhance the dilution stability. The in vitro release characteristics of insulin from gels in media at different pH values were investigated. The insulin loaded vesicles–chitosan hydrogel (IVG) improved the dilution stability of the vesicles and provided pH-selective sustained release compared with insulin solution–chitosan hydrogel (ISG). In vitro, IVG exhibited slow release in acidic solution and relatively quick release in neutral solutions to provide drug efficacy. In simulated digestive fluid, IVG showed better sustained release and insulin protection properties compared with ISG. Thus IVG might improve the stability of insulin during its transport in vivo and contribute to the bioavailability and therapeutic effect of 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.

A bacterial protease inhibitor protects antigens delivered in oral vaccines from digestion while triggering specific mucosal immune responses

We report here that a bacterial protease inhibitor from Brucella spp. called U-Omp19 behaves as an ideal constituent for a vaccine formulation against infectious diseases. When co-administered orally with an antigen (Ag), U-Omp19: i) can bypass the harsh environment of the gastrointestinal tract by inhibiting stomach and intestine proteases and consequently increases the half-life of the co-administered Ag at immune inductive sites: Peyer's patches and mesenteric lymph nodes while ii) it induces the recruitment and activation of antigen presenting cells (APCs) and increases the amount of intracellular Ag inside APCs. Therefore, mucosal as well as systemic Ag-specific immune responses, antibodies, Th1, Th17 and CD8(+) T cells are enhanced when U-Omp19 is co-administered with the Ag orally. Finally, this bacterial protease inhibitor in an oral vaccine formulation confers mucosal protection and reduces parasite loads after oral challenge with virulent Toxoplasma gondii.

Application of polymeric nanoparticles and micelles in insulin oral delivery

Diabetes mellitus is an endocrine disease in which the pancreas does not produce sufficient insulin or the body cannot effectively use the insulin it produces. Insulin therapy has been the best choice for the clinical management of diabetes mellitus. The current insulin therapy is via subcutaneous injection, which often fails to mimic the glucose homeostasis that occurs in normal individuals. This provokes numerous attempts to develop a safe and effective noninvasive route for insulin delivery. Oral delivery is the most convenient administration route. However, insulin cannot be well absorbed orally because of its rapid enzymatic degradation in the gastrointestinal tract. Therefore, nanoparticulate carriers such as polymeric nanoparticles and micelles are employed for the oral delivery of insulin. These nanocarriers protect insulin from degradation and facilitate insulin uptake via a transcellular and/or paracellular pathway. This review article focuses on the application of nanoparticles and micelles in insulin oral delivery. The recent advances in this topic are also reviewed.

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.

A review of biodegradable polymeric systems for oral insulin delivery

Currently, repeated routine subcutaneous injections of insulin are the standard treatment for insulin-dependent diabetic patients. However, patients' poor compliance for injections often fails to achieve the stable concentration of blood glucose. As a protein drug, the oral bioavailability of insulin is low due to many physiological reasons. Several carriers, such as macromolecules and liposomes have been used to deliver drugs in vivo. In this review article, the gastrointestinal barriers of oral insulin administration are described. Strategies for increasing the bioavailability of oral insulin, such absorption enhancers, enzyme inhibitors, enteric coatings are also introduced. The potential absorption mechanisms of insulin-loaded nanoparticles across the intestinal epithelium, including intestinal lymphatic route, transcellular route and paracellular route are discussed in this review. Natural polymers, such as chitosan and its derivates, alginate derivatives, γ-PGA-based materials and starch-based nanoparticles have been exploited for oral insulin delivery; synthetic polymers, such as PLGA, PLA, PCL and PEA have also been developed for oral administration of insulin. This review focuses on recent advances in using biodegradable natural and synthetic polymers for oral insulin delivery along with their future prospects.

Preclinical Pharmacokinetic Studies of the Tritium Labelled D-Enantiomeric Peptide D3 Developed for the Treatment of Alzheimer´s Disease

Targeting toxic amyloid beta (Aβ) oligomers is currently a very attractive drug development strategy for treatment of Alzheimer´s disease. Using mirror-image phage display against Aβ1-42, we have previously identified the fully D-enantiomeric peptide D3, which is able to eliminate Aβ oligomers and has proven therapeutic potential in transgenic Alzheimer´s disease animal models. However, there is little information on the pharmacokinetic behaviour of D-enantiomeric peptides in general. Therefore, we conducted experiments with the tritium labelled D-peptide D3 (³H-D3) in mice with different administration routes to study its distribution in liver, kidney, brain, plasma and gastrointestinal tract, as well as its bioavailability by i.p. and p.o. administration. In addition, we investigated the metabolic stability in liver microsomes, mouse plasma, brain, liver and kidney homogenates, and estimated the plasma protein binding. Based on its high stability and long biological half-life, our pharmacokinetic results support the therapeutic potential of D-peptides in general, with D3 being a new promising drug candidate for Alzheimer´s disease treatment.

Assessment of the drug loading, in vitro and in vivo release behavior of novel pH-sensitive hydrogel

CONTEXT

As a glucocorticoid drug, dexamethasone has good therapeutic effects for ulcerative colitis. pH-sensitive hydrogels could make conventional changes of volume in response with different pH values. Meanwhile, they could load drugs depending on its internal three-dimensional network structure.

OBJECTIVE

Appropriate methods were used to improve the drug-loading capacity of hydrogel and exploring the colon-targeting character of dexamethasone hydrogel.

MATERIALS AND METHODS

Different solvents (ethanol and 1,2-propanediol) were employed to dissolve dexamethasone as well as hydrogel monomer materials (poly(ethylene glycol) methyl ether (MPEG)-poly(lactide acid)-acryloyl chloride macromonomer, itaconic acid (IA) and MPEG-methacrylate), then mixing them together to prepare hydrogel through the heat-initiated free radical polymerization method. Differential scanning calorimetry and X-ray diffraction methods were used to verify whether dexamethasone was loaded into hydrogels. In vitro drug release behavior and in vivo pharmacokinetic study were also investigated in detail.

RESULTS

Dexamethasone was successfully loaded into hydrogel, and its loading capacity was improved (5 mg/g). Both the in vitro release study and the in vivo pharmacokinetic study showed the good colon-targeting character of the pH-sensitive P(LE-IA-MEG) hydrogel (T max = 1.0 h, C max = 2.16 µg/ml of dexamethasone; T max = 3.9 h, C max = 0.43 µg/ml of dexamethasone hydrogel).

DISCUSSION

Dexamethasone could be targeted to the colon site by P(LE-IA-MEG) hydrogel, thereby improving its therapeutic effect and reduce its side effects.

CONCLUSION

P(LE-IA-MEG) hydrogel might have great potential application in colon-targeted drug delivery systems.

Particle designs for the stabilization and controlled-delivery of protein drugs by biopolymers: a case study on insulin

Natural biopolymers have attracted considerable interest for the development of delivery systems for protein drugs owing to their biocompatibility, non-toxicity, renewability and mild processing conditions. This paper offers an overview of the current status and future perspectives of particle designs using biopolymers for the stabilization and controlled-delivery of a model protein drug--insulin. We first describe the design criteria for polymeric encapsulation and subsequently classify the basic principles of particle fabrication as well as the existing particle designs for oral insulin encapsulation. The performances of these existing particle designs in terms of insulin stability and in vitro release behavior in acidic and alkaline media, as well as their in vivo performance are compared and reviewed. This review forms the basis for future works on the optimization of particle design and material formulation for the development of an improved oral delivery system for protein drugs.

Development of a novel drug delivery system: chitosan nanoparticles entrapped in alginate microparticles

A novel carrier using chitosan nanoparticles entrapped into alginate microparticles is proposed for protecting molecules of interest from degradation in the digestive tract. The effects of polymer concentration, sonication, stirring, pH, and processing conditions on the physical characteristics of the carrier were studied. FITC and RBITC were used to localise the polymers within particles using CLSM. Diffusion of amaranth red (AR) from nanoparticles was quantified during dissolution under gastric and intestinal conditions. Under optimal preparation conditions, the size distribution of nanoparticles loaded with AR was uniform (690 nm) with an encapsulation efficacy of 21.9%. Alginate microparticles (285 µm) containing a homogenous distribution of nanoparticles and polymers were obtained. At gastric pH, the carrier released less than 5% of the loaded AR and, at intestinal pH, the release was rapid and complete. The drug carriers developed shows a promising use as a vehicle suitable to protect molecules of interest after oral administration.

Oral calcium pectinate-insulin nanoparticles: influences of alginate, sodium chloride and Tween 80 on their blood glucose lowering performance

Objective

Examine the formation of pectin-insulin nanoparticles and their blood glucose lowering properties.

Methods

The calcium pectinate nanoparticles were prepared by ionotropic gelation method, with alginate, sodium chloride or Tween 80 as additive. Their in vitro physicochemical, drug release and in vivo blood glucose lowering characteristics were evaluated.

Key findings

Spherical calcium pectinate-insulin nanoparticles were characterized by size, zeta potential, insulin content and insulin association efficiency of 348.4 ± 12.9 nm, −17.9 ± 0.8 mV, 8.4 ± 1.0% and 63.8 ± 7.4%, respectively. They released less than 25% insulin following 24 h in simulated intestinal medium and exhibited delayed blood glucose lowering effect in rats. Incorporation of solubilizer sodium chloride or Tween 80 into nanoparticles did not enhance blood glucose lowering capacity owing to sodium chloride reduced matrix insulin content and Tween 80 interacted with water and had its blood glucose dilution effect negated. Combination of nanoparticles with alginate gel to allow prolonged intestinal residence and more insulin release did not enhance their blood glucose lowering capacity because of calcium alginate-cross-linked gel formation that could retard insulin release and migration into systemic circulation.

Conclusion

Physicochemical responses of additives in vivo affected blood glucose regulation property of pectin-insulin nanoparticles.

Nanoparticulate assembly of mannuronic acid- and guluronic acid-rich alginate: oral insulin carrier and glucose binder

The relationship of high and low molecular weight mannuronic acid (M)- and guluronic acid (G)-rich alginate nanoparticles as oral insulin carrier was elucidated. Nanoparticles were prepared through ionotropic gelation using Ca(2+) , and then in vitro physicochemical attributes and in vivo antidiabetic characteristics were examined. The alginate nanoparticles had insulin release retarded when the matrices had high alginate-to-insulin ratio or strong alginate-insulin interaction via OH moiety. High molecular weight M-rich alginate nanoparticles were characterized by assemblies of long polymer chains that enabled insulin encapsulation with weaker polymer-drug interaction than nanoparticles prepared from other alginate grades. They were able to encapsulate and yet release and have insulin absorbed into systemic circulation, thereby lowering rat blood glucose. High molecular weight G- and low molecular weight M-rich alginate nanoparticles showed remarkable polymer-insulin interaction. This retarded the drug release and negated its absorption. Blood glucose lowering was, however, demonstrated in vivo with insulin-free matrices of these nanoparticles because of the strong alginate-glucose binding that led to intestinal glucose retention. Alginate nanoparticles can be used as oral insulin carrier or glucose binder in the treatment of diabetes as a function of its chemical composition. High molecular weight M-rich alginate nanoparticles are a suitable vehicle for future development into oral insulin carrier.

pH- and thermo-responsive poly(N-isopropylacrylamide-co-acrylic acid derivative) copolymers and hydrogels with LCST dependent on pH and alkyl side groups

A series of pH- and temperature-responsive poly(N-isopropylacrylamide-co-acrylic acid derivative) (P(NIPAM-co-AAD)) copolymers and hydrogels were prepared. The lower critical solution temperatures (LCSTs) of the copolymers exhibited a dependence on both pH and the hydrophobicity of the AAD unit. The influence of pH and temperature on the equilibrium swelling ratio of the hydrogels was investigated. The hydrogels displayed a unique thermo-induced swelling-deswelling transition that can be self-regulated to occur at above or below the physiological temperature in response to the environmental pH. Scanning electron microscopic (SEM) analysis revealed porous sponge-like microstructures of the hydrogels. Insulin was loaded into the hydrogels as a model protein, and the in vitro release profiles indicated that the loaded protein could be protected within the hydrogels in an acidic environment and selectively released in neutral medium. MTT assay proved that both the copolymers and hydrogels are nontoxic. After oral administration of the insulin-loaded hydrogels to streptozotocin-induced diabetic rats at 60 IU per kg, the fasting plasma glucose level was reduced continuously to 72.1% within 6 h. The bioavailability of hydrogel-encapsulated insulin via the oral administration to healthy rabbits reached 5.24%, which is much higher than that of pure insulin solution given orally. These results showed that the smart copolymers and hydrogels may hold great promise for pH-triggered drug delivery systems.

Oral insulin delivery: how far are we?

Oral delivery of insulin may significantly improve the quality of life of diabetes patients who routinely receive insulin by the subcutaneous route. In fact, compared with this administration route, oral delivery of insulin in diabetes treatment offers many advantages: higher patient compliance, rapid hepatic insulinization, and avoidance of peripheral hyperinsulinemia and other adverse effects such as possible hypoglycemia and weight gain. However, the oral delivery of insulin remains a challenge because its oral absorption is limited. The mainbarriers faced by insulin in the gastrointestinal tract are degradation by proteolytic enzymes and lack of transport across the intestinal epithelium. Several strategies to deliver insulin orally have been proposed, but without much clinical or commercial success. Protein encapsulation into nanoparticles is regarded as a promising alternative to administer insulin orally because they have the ability to promote insulin paracellular or transcellular transport across the intestinal mucosa. In this review, different delivery systems intended to increase the oral bioavailability of insulin will be discussed, with a special focus on nanoparticulate carrier systems, as well as the efforts that pharmaceutical companies are making to bring to the market the first oral delivery system of insulin. The toxicological and safety data of delivery systems, the clinical value and progress of oral insulin delivery, and the future prospects in this research field will be also scrutinized.

Ternary interpolyelectrolyte complexes insulin-poly(methylaminophosphazene)-dextran sulfate for oral delivery of insulin

Ternary interpolyelectrolyte complexes of insulin with biodegradable synthetic cationic polymer, poly(methylaminophosphazene) hydrochloride (PMAP), and dextran sulfate (DS) were investigated by means of turbidimetry, dynamic light scattering, phase analysis, and high-sensitivity differential scanning calorimetry. Formation of ternary insoluble stoichiometric Insulin-PMAP-DS complexes was detected under conditions imitating the human gastric environment (pH 2, 0.15 M NaCl). A complete immobilization of insulin in the complexes was observed in a wide range of the reaction mixture compositions. The ternary complexes were shown to dissolve and dissociate under conditions imitating the human intestinal environment (pH 8.3, 0.15 M NaCl). The products of the complex dissociation were free insulin and soluble binary Insulin-PMAP complexes. The conformational stability of insulin in the soluble complexes of various compositions was investigated by high-sensitivity differential scanning calorimetry. The dependence of the excess denaturation free energy of insulin in these complexes on the PMAP content was obtained. The binding constants of the folded and unfolded forms of insulin to the PMAP polycation were estimated. Proteolysis of insulin involved in the insoluble ternary complexes by pepsin was investigated under physiological conditions. It was found that the complexes ensure an almost 100% protection of insulin against proteolytic degradation. The obtained results provide a perspective basis for development of oral insulin preparations.

Blood glucose lowering property of water in oral insulin-fed diabetic rats

CONTEXT

In oral insulin delivery, blood glucose profiles of a subject can be a function of complicated transfer of water and insulin between gastrointestinal and blood compartments.

OBJECTIVE

This study examined the effects of orally administered water on blood glucose profiles of oral insulin-fed diabetic rats. The blood glucose, insulin and red blood cell concentration profiles of streptozotocin-induced diabetic rats were determined following administration of deionized water and insulin solution (14 IU/kg) with control receiving none. The aqueous solution samples were subjected to X-ray diffractometry (XRD), fourier transform infra-red spectroscopy (FTIR), viscometry and osmolality tests to elucidate the state of water-insulin interaction.

RESULTS AND DISCUSSION

Deionized water reduced blood glucose concentration by more than 70% via dilution of systemic circulation. The addition of insulin into deionized water negated its blood glucose lowering property instead of no influence due to insulin had not shown marked oral bioavailability. The insulin interacted with water to form solution with higher viscosity and osmolality values.

CONCLUSION

Insulin-water interaction could be one reason where water migration from the gastrointestinal lumen into systemic circulation is reduced and blood glucose lowering capacity of deionized water is negated.

New technologies for diabetes: a review of the present and the future

This review summarizes the technologies in use and in the pipeline for the management of diabetes. The review focuses on glucose meters, continuous glucose monitoring devices, insulin pumps, and getting clinicians connected to technologies. All information presented can be found in the public domain, and was obtained from journal articles, websites, product review tables in patient publications, and professional conferences. The technology concerns, ongoing development and future trends in this area are also discussed.

Administration, distribution, metabolism and elimination of polymer therapeutics

Polymer conjugation is an efficient approach to improve the delivery of drugs and biological agents, both by protecting the body from the drug (by improving biodistribution and reducing toxicity) and by protecting the drug from the body (by preventing degradation and enhancing cellular uptake). This review discusses the journey that polymer therapeutics make through the body, following the ADME (absorption, distribution, metabolism, excretion) concept. The biological factors and delivery system parameters that influence each stage of the process will be described, with examples illustrating the different solutions to the challenges of drug delivery systems in vivo.

Evaluation of an oral insulin formulation in normal and diabetic rats

Aim:

As injection is not an ideal means for insulin delivery, various attempts have been made to administer insulin orally until now. The development of an oral dosage form of insulin would help diabetic patients and make the treatment more convenient. The aim of the present study is to evaluate the effectiveness of an oral insulin formulation containing polar and non-polar ingredients.

Materials and Methods:

New excipient for oral insulin administration in normal and diabetic rats was evaluated by measuring blood glucose concentrations in two groups (10 rats each) of normal and streptozotocin-induced diabetic rats. Oral insulin was administrated and blood glucose was measured by glucometer at 0, 1, 2, 3 and 4 h post-feeding. The data was compared by Student's t test.

Results:

Oral insulin formulation significantly (P<0.05) reduced blood glucose from 100 mg/dl to 33.73 mg/dl and 451.66 mg/dl to 200.83 mg/dl at 4 h in normal and diabetic rats, respectively.

Conclusion:

The novel excipient used could protect insulin from gastric and pancreatic enzymes and reduce blood glucose concentration in both healthy and diabetic rats suggesting that oral delivery of insulin is feasible in a near future.

Oral colon delivery of insulin with the aid of functional adjuvants

Oral colon delivery is currently considered of importance not only for the treatment of local pathologies, such as primarily inflammatory bowel disease (IBD), but also as a means of accomplishing systemic therapeutic goals. Although the large bowel fails to be ideally suited for absorption processes, it may indeed offer a number of advantages over the small intestine, including a long transit time, lower levels of peptidases and higher responsiveness to permeation enhancers. Accordingly, it has been under extensive investigation as a possible strategy to improve the oral bioavailability of peptide and protein drugs. Because of a strong underlying rationale, most of these studies have focused on insulin. In the present review, the impact of key anatomical and physiological characteristics of the colon on its viability as a protein release site is discussed. Moreover, the main formulation approaches to oral colon targeting are outlined along with the design features and performance of insulin-based devices.