Novel non-invasive methods of insulin delivery

Non-Invasive Delivery of Insulin for Breaching Hindrances against Diabetes

Insulin is recognized as a crucial weapon in managing diabetes. Subcutaneous (s.c.) injections are the traditional approach for insulin administration, which usually have many limitations. Numerous alternative (non-invasive) slants through different routes have been explored by the researchers for making needle-free delivery of insulin for attaining its augmented absorption as well as bioavailability. The current review delineating numerous pros and cons of several novel approaches of non-invasive insulin delivery by overcoming many of their hurdles. Primary information on the topic was gathered by searching scholarly articles from PubMed added with extraction of data from auxiliary manuscripts. Many approaches (discussed in the article) are meant for the delivery of a safe, effective, stable, and patient friendly administration of insulin via buccal, oral, inhalational, transdermal, intranasal, ocular, vaginal and rectal routes. Few of them have proven their clinical efficacy for maintaining the glycemic levels, whereas others are under the investigational pipe line. The developed products are comprising of many advanced micro/nano composite technologies and few of them might be entering into the market in near future, thereby garnishing the hopes of millions of diabetics who are under the network of s.c. insulin injections.

Oral insulin delivery: Barriers, strategies, and formulation approaches: A comprehensive review

Diabetes Mellitus is characterized by a hyperglycemic condition which can either be caused by the destruction of the beta cells or by the resistance developed against insulin in the cells. Insulin is a peptide hormone that regulates the metabolism of carbohydrates, proteins, and fats. Type 1 Diabetes Mellitus needs the use of Insulin for efficient management. However invasive methods of administration may lead to reduced adherence by the patients. Hence there is a need for a non-invasive method of administration. Oral Insulin has several merits over the conventional method including patient compliance, and reduced cost, and it also mimics endogenous insulin and hence reaches the liver by the portal vein at a higher concentration and thereby showing improved efficiency. However oral Insulin must pass through several barriers in the gastrointestinal tract. Some strategies that could be utilized to bypass these barriers include the use of permeation enhancers, absorption enhancers, use of suitable polymers, use of suitable carriers, and other agents. Several formulation types have been explored for the oral delivery of Insulin like hydrogels, capsules, tablets, and patches which have been described briefly by the article. A lot of attempts have been made for developing oral insulin delivery however none of them have been commercialized due to numerous shortcomings. Currently, there are several formulations from the companies that are still in the clinical phase, the success or failure of some is yet to be seen in the future.

A Review of Non-Invasive Drug Delivery through Respiratory Routes

With rapid and non-invasive characteristics, the respiratory route of administration has drawn significant attention compared with the limitations of conventional routes. Respiratory delivery can bypass the physiological barrier to achieve local and systemic disease treatment. A scientometric analysis and review were used to analyze how respiratory delivery can contribute to local and systemic therapy. The literature data obtained from the Web of Science Core Collection database showed an increasing worldwide tendency toward respiratory delivery from 1998 to 2020. Keywords analysis suggested that nasal and pulmonary drug delivery are the leading research topics in respiratory delivery. Based on the results of scientometric analysis, the research hotspots mainly included therapy for central nervous systems (CNS) disorders (Parkinson’s disease, Alzheimer’s disease, depression, glioblastoma, and epilepsy), tracheal and bronchial or lung diseases (chronic obstructive pulmonary disease, asthma, acute lung injury or respiratory distress syndrome, lung cancer, and idiopathic pulmonary fibrosis), and systemic diseases (diabetes and COVID-19). The study of advanced preparations contained nano drug delivery systems of the respiratory route, drug delivery barriers investigation (blood-brain barrier, BBB), and chitosan-based biomaterials for respiratory delivery. These results provided researchers with future research directions related to respiratory delivery.

The modern pharmacological approach to diabetes: innovative methods of monitoring and insulin treatment

INTRODUCTION

Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorders characterised by a high blood sugar level over a prolonged period of time. In order to maintain this blood glucose value in normal parameters, a careful monitoring of it and insulin administration are necessary.

AREAS COVERED

Thus, to facilitate this procedure, new blood glucose monitoring systems have been studied. The smart lens, the nano tattoo, non-invasive sensors based on reverse ionthophoresis and glucose oxidase - based continuous blood glucose monitoring systems, are the methods described in this study. Of course, not only is blood glucose monitoring important, but also the lifestyle of a drug or the way a drug is administered, especially in the cae of insulin. How insulin is administered is also a topic that we address in this article. In an attempt to promote compliance with the administration, we have discussed about new forms of administering insulin such as: oral, intranasal, administration on the oral mucosa and last but not least, transdermal administration.

EXPERT OPINION

Further, the attention of specialists should be directed to devices based on sensors, with a role in the interruption of insulin administration, in case of detection of hypoglycemia or the additional dose of insulin, if hyperglycemia is detected.

Strategies for the delivery of antidiabetic drugs via intranasal route

Diabetes is a metabolic disorder defined by higher blood glucose levels in the body generally controlled by antidiabetic agents (oral) and insulin (subcutaneous). To avoid the limitations of the conventional routes such as lower bioavailability and pain at the site of injection in case of parenteral route modified delivery systems are proposed like transdermal, pulmonary and inhalation delivery and among the other delivery systems nasal drug delivery system that shows the advantages such as reduced frequency of dose, higher patient compliance, safety, ease of administration, prolonged residence time, improved absorption of drug in the body, higher bioavailability and stability. This review article discusses the strategies adopted for the delivery of antidiabetic drugs by the intranasal delivery system. The insulin and glucagon-like peptides on experimentation show results of improved therapeutic levels and patient compliance. The drugs are transported by the paracellular route and absorbed through the epithelial tight junctions successfully by utilising different strategies. The limitations of the nasal delivery such as irritation or burning on administration, degradation by the enzymes, mucociliary clearance, lesser volume of the nasal cavity and permeation through the nasal mucosa. To overcome the challenges different strategies for the nasal administration are studied such as polymers, particulate delivery systems, complexation with peptides and smart delivery using glucose-responsive systems. A vast scope of intranasal preparations exists for antidiabetic drugs in the future for the management of diabetes and more clinical studies are the requirement for the societal impact to battle against diabetes.

Role of lipid nanocarriers for enhancing oral absorption and bioavailability of insulin and GLP-1 receptor agonists

Growing demand for insulin and glucagon-like peptide-1 receptor agonists (GLP-1 RA) is observed, considering the progressive nature of diabetes and the potential therapeutic role of peptides in its treatment. However, chronic parenteral administration is responsible for pain and rashes at the site of injection. Oral delivery of insulin and GLP-1 RA promises better patient compliance owing to their ease of administration and reduction in chances of peripheral hypoglycaemia and weight gain. The review article discusses the potential of lipid carriers in combination with different strategies such as absorption enhancers, PEGylation, lipidisation, etc. The lipid nanocarriers improve the membrane permeability and oral bioavailability of high molecular weight peptides. Additionally, the clinical status of different nanocarriers for anti-diabetic peptides is discussed. Previous research on nanocarriers showed significant hypoglycaemic activity and safety in animal studies; however, extrapolation of the same in human subjects is not validated. With the rising global burden of diabetes, the lipid nanocarriers show the potential to revolutionise treatment with oral delivery of insulin and GLP-1 RA.

Report on biopharmaceutical profile of recent biotherapeutics and insilco docking studies on target bindings of known aptamer biotherapeutics

Accumulated Toxicity, disease recurrence and drug resistivity problems have been observed due to the synthetic and semisynthetic therapeutic practices, which alternatively led to focus on Bio-therapeutics production than xenobiotics. Quick plasma clearance and high potency are the reasons for trending research with huge pharma market of numerous Bio-therapeutics than ever before. Researchers proved that most of the nano and micro Bio-therapeutics have multiple beneficial therapeutic effects. We have analyzed the past, and present scenario of some notable clinically approved Bio-therapeutics to identify the future formulation needs with advanced techniques. Protein-related drugs are the foremost Bio-therapeutics such as antibodies, enzymes, and short, fragmented polypeptides show aggregation properties during storage, naked peptide moieties are resisted by the polar cell membrane, and also the antidrug antibodies were reported. Even though Nucleic acid nano-bodies are excellent target binders than proteins, they had only a few minutes of half-life. Maintaining homogeneousness upon storage of Bio-therapeutics is still a significant challenge in industrial-scale formulation. Notably, plant systems are identified as most useful cost-effective hosts to produce human enzymes than animal systems without any possible viral loads. Irrespective of numerous advancements in routes of administration and additives, subcutaneous is still a golden one to achieve better dynamics. Additionally, the interactions and effective bonds made by each class of well-known aptamer biotherapeutics which are considered as future drugs were studied.

Exploring protein stabilized multiple emulsion with permeation enhancer for oral delivery of insulin

In present study, we have developed W/O/W microemulsion (ME) containing piperine (PiP) as a permeation enhancer and albumin (Alb) serving as a stabilizer for oral delivery of insulin (INS). The resultant formulation, ME(INS)-PiP-Alb exhibited droplet size of 3.35 ± 0.25 μm along with polydispersity index (PDI) of 0.30 ± 0.10. The formulation process employed for developing ME(INS)-PiP-Alb showed no effect on INS's chemical and conformational stability. Further, ME(INS)-PiP-Alb was able to maintain desired attributes (size & PDI) along with INS stability in simulated gastrointestinal fluids. Also, ME(INS)-PiP-Alb rendered higher protection to INS in presence of pepsin and trypsin than ME(INS)-PiP. In qualitative Caco-2 cell uptake, INS loaded ME's showed higher uptake in comparison to free INS. Whereas, in permeability studies ME(INS)-PiP-Alb showed ~4 and ~1.5-fold enhanced permeation than free INS and ME(INS) without PiP groups respectively. Also, in ex vivo intestinal permeation studies similar fold increment in permeation were observed. Interestingly, the pharmacodynamic studies revealed ~3.2-fold higher hypoglycemic effect in animals treated with ME(INS)-PiP-Alb in comparison to ME(INS)-PiP. Similarly, the pharmacokinetic studies also revealed ~1.6 fold higher AUC for ME(INS)-PiP-Alb than ME(INS)-PiP. Thus, in vivo results suggested that Alb as a stabilizer can assist in improving the hypoglycemic effect of the developed ME with PiP. Hence, this strategy can also be extrapolated for delivering other bio-macromolecules orally.

Drug Delivery Systems for Diabetes Treatment

BACKGROUND

Insulin is essential for the treatment of Type 1 diabetes mellitus (T1DM) and is necessary in numerous cases of Type 2 diabetes mellitus (T2DM). Prolonged administration of anti-diabetic therapy is necessary for the maintenance of the normal glucose levels and thereby preventing vascular complications. A better understanding of the disease per se and the technological progress contribute to the development of new approaches with the aim to achieve better glycemic control.

OBJECTIVE

Current therapies for DM are faced with some challenges. The purpose of this review is to analyze in detail the current trends for insulin delivery systems for diabetes treatment.

RESULTS

Contemporary ways have been proposed for the management of both types of diabetes by adequate application of drug via subcutaneous, buccal, oral, ocular, nasal, rectal and pulmonary ways. Development of improved oral administration of insulin is beneficial regarding mimicking physiological pathway of insulin and minimizing the discomfort of the patient. Various nanoparticle carriers for oral and other ways of insulin delivery are currently being developed. Engineered specific properties of nanoparticles (NP): controlling toxicity of NP, stability and drug release, can allow delivery of higher concentration of the drug to the desired location.

CONCLUSIONS

The successful development of any drug delivery system relies on solving three important issues: toxicity of nanoparticles, stability of nanoparticles, and desired drug release rate at targeted sites. The main goals of future investigations are to improve the existing therapies by pharmacokinetic modifications, development of a fully automatized system to mimic insulin delivery by the pancreas and reduce invasiveness during admission.

Electrospun nanofibers for the delivery of active drugs through nasal, oral and vaginal mucosa: Current status and future perspectives

Transmucosal surfaces bypass many limitations associated with conventional drug delivery (oral and parenteral routes), such as poor absorption rate, enzymatic activity, acidic environment and first-pass metabolism occurring inside the liver. However, these surfaces have several disadvantages such as poor retention time, narrow absorption window and continuous washout of the drug by the surrounding fluids. Electrospun nanofibers with their unique surface properties and encapsulation efficiency may act as novel drug carriers to overcome the challenges associated with conventional drug delivery routes, so as to achieve desired therapeutic responses. This review article provides detailed information regarding the challenges faced in the mucosal delivery of drugs, and the use of nanofiber systems as an alternative to deliver drugs to the systemic circulation, as well as local drug administration. The physiological and anatomical features of different types of mucosal surfaces and current challenges are systematically discussed. We also address future considerations in the area of transmucosal delivery of some important drugs.

Recent Avenues in Novel Patient-Friendly Techniques for the Treatment of Diabetes

Background:

Diabetes is one of the most common chronic metabolic disorders which affect the quality of human life worldwide. As per the WHO report, between 1980 to 2014, the number of diabetes patients increases from 108 million to 422 million, with a global prevalence rate of 8.5% per year. Diabetes is the prime reason behind various other diseases like kidney failure, stroke, heart disorders, glaucoma, etc. It is recognized as the seventh leading cause of death throughout the world. The available therapies are painful (insulin injections) and inconvenient due to higher dosing frequency. Thus, to find out a promising and convenient treatment, extensive investigations are carried out globally by combining novel carrier system (like microparticle, microneedle, nanocarrier, microbeads etc.) and delivery devices (insulin pump, stimuli-responsive device, inhalation system, bioadhesive patch, insulin pen etc.) for more precise diagnosis and painless or less invasive treatment of disease.

Objective:

The review article is made with an objective to compile information about various upcoming and existing modern technologies developed to provide greater patient compliance and reduce the undesirable side effect of the drug. These devices evade the necessity of daily insulin injection and offer a rapid onset of action, which sustained for a prolonged duration of time to achieve a better therapeutic effect.

Conclusion:

Despite numerous advantages, various commercialized approaches, like Afrezza (inhalation insulin) have been a failure in recent years. Such results call for more potential work to develop a promising system. The novel approaches range from the delivery of non-insulin blood glucose lowering agents to insulin-based therapy with minimal invasion are highly desirable.

Scalable production of core-shell nanoparticles by flash nanocomplexation to enhance mucosal transport for oral delivery of insulin

Scalable manufacturing continues to present a major barrier for clinical translation of nanotherapeutics. Methods available for fabricating protein-encapsulating nanoparticles in a scalable fashion are scarce. Protein delivery often requires multiple functionalities to be incorporated into the same vehicle. Specifically for nanoparticle-mediated oral delivery of protein therapeutics, protection in GI tract, site-specific release, facilitating transmucosal permeation, and enhancing epithelial transport are a few desirable features to be engineered into a nanoparticle system. Here we devised a sequential flash nanocomplexation (FNC) technique for the scalable production of a core-shell structured nanoparticle system by combining materials choice and particle size and structure to fulfill these functions, therefore enhancing the delivery efficiency of insulin. This method is highly effective in controlling the size, generating core-shell structure with high encapsulation efficiency (97%) and payload capacity (67%) using insulin/l-penetratin complex nanoparticles as a core coated with hyaluronic acid (HA). Both the in vitro and in vivo models confirmed that the HA coating on these core-shell nanoparticles enhanced the permeation of nanoparticles through the intestinal mucus layer and improved trans-epithelial absorption of insulin nanoparticles; and the enhancement effect was most prominent using HA with the highest average molecular weight. The insulin-loaded nanoparticles were then encapsulated into enteric microcapsules (MCs) in an FNC process to provide additional protection against the acidic environment in the stomach while allowing rapid release of insulin nanoparticles when they reach small intestine. The optimized multifunctional MCs delivered an effective glucose reduction in a Type I diabetes rat model following a single oral administration, yielding a relative bioavailability of 11% in comparison with subcutaneous injection of free-form insulin. This FNC technique is highly effective in controlling particle size and structure to improve delivery properties and function. It can be easily extended to oral delivery for other protein therapeutics.

Controlling insulin release from reverse hexagonal (HII) liquid crystalline mesophase by enzymatic lipolysis

In the present study we aimed to control insulin release from the reverse hexagonal (H_II) mesophase using Thermomyces lanuginosa lipase (TLL) in the environment (outer TLL) or within the H_II cylinders (inner TLL). Two insulin-loaded systems differing by the presence (or absence) of phosphatidylcholine (PC) were examined. In general, incorporation of PC into the H_II interface (without TLL) increased insulin release, as a more cooperative system was formed. Addition of TLL to the systems' environments resulted in lipolysis of the H_II structure. In the absence of PC, the lipolysis was more dominant and led to a significant increase in insulin release (50% after 8h). However, the presence of PC stabilized the interface, hindering the lipolysis, and therefore no impact on the release profile was detected during the first 8h. Entrapment of TLL within the H_II cylinders (with and without PC) drastically increased insulin release in both systems up to 100%. In the presence of PC insulin released faster and the structure was more stable. Consequently, the presence of lipases (inner or outer) both enhanced the destruction of the carrier, and provided sustained release of the entrapped insulin.

Oral insulin delivery: existing barriers and current counter-strategies

Objectives

The chronic and progressive nature of diabetes is usually associated with micro- and macrovascular complications where failure of pancreatic β-cell function and a general condition of hyperglycaemia is created. One possible factor is failure of the patient to comply with and adhere to the prescribed insulin due to the inconvenient administration route. This review summarizes the rationale for oral insulin administration, existing barriers and some counter-strategies trialled.

Key findings

Oral insulin mimics the physiology of endogenous insulin secreted by pancreas. Following the intestinal absorption of oral insulin, it reaches the liver at high concentration via the portal vein. Oral insulin on the other hand has the potential to protect pancreatic β-cells from autoimmune destruction. Structural modification, targeting a particular tissue/receptor, and the use of innovative pharmaceutical formulations such as nanoparticles represent strategies introduced to improve oral insulin bioavailability. They showed promising results in overcoming the hurdles facing oral insulin delivery, although delivery is far from ideal.

Summary

The use of advanced pharmaceutical technologies and further research in particulate carrier system delivery predominantly nanoparticle utilization would offer useful tools in delivering insulin via the oral route which in turn would potentially improve diabetic patient compliance to insulin and the overall management of diabetes.

Functional nanocarrier for drug and gene delivery via local administration in mucosal tissues

Local administration has many advantages for treating diseases. However, the surface mucus layer becomes a major obstacle that easily traps and fast removes local administrated drugs and genes in mucosal tissues. Fortunately, the rapidly developing nanocarriers with special physical and chemical properties may help to refine the treatment of mucosal tissues via delivering drugs and genes to the target tissue, and prolong the drug action time. Therefore, this review focuses on the strategies to apply different nanocarriers for drug-delivery in mucosal tissues, including mucoadhesive and mucus-penetrating types. Delivering drugs and genes to anatomical sites with high mucus turnover becomes more feasible and effective, and maintains sufficient local drug concentration to improve treatment efficacy.

Chitosan nanofibers for transbuccal insulin delivery

In this work, they aimed at producing chitosan based nanofiber mats capable of delivering insulin via the buccal mucosa. Chitosan was electrospun into nanofibers using poly(ethylene oxide) (PEO) as a carrier molecule in various feed ratios. The mechanical properties and degradation kinetics of the fibers were measured. Insulin release rates were determined in vitro using an ELISA assay. The bioactivity of released insulin was measured in terms of Akt activation in pre-adipocytes. Insulin permeation across the buccal mucosa was measured in an ex-vivo porcine transbuccal model. Fiber morphology, mechanical properties, and in vitro stability were dependent on PEO feed ratio. Lower PEO content blends produced smaller diameter fibers with significantly faster insulin release kinetics. Insulin showed no reduction in bioactivity due to electrospinning. Buccal permeation of insulin facilitated by high chitosan content blends was significantly higher than that of free insulin. Taken together, the work demonstrates that chitosan-based nanofibers have the potential to serve as a transbuccal insulin delivery vehicle. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1252-1259, 2017.

Insulin delivery methods: Past, present and future

Many patients with advanced type 2 diabetes mellitus (T2DM) and all patients with T1DM require insulin to keep blood glucose levels in the target range. The most common route of insulin administration is subcutaneous insulin injections. There are many ways to deliver insulin subcutaneously such as vials and syringes, insulin pens, and insulin pumps. Though subcutaneous insulin delivery is the standard route of insulin administration, it is associated with injection pain, needle phobia, lipodystrophy, noncompliance and peripheral hyperinsulinemia. Therefore, the need exists for delivering insulin in a minimally invasive or noninvasive and in most physiological way. Inhaled insulin was the first approved noninvasive and alternative way to deliver insulin, but it has been withdrawn from the market. Technologies are being explored to make the noninvasive delivery of insulin possible. Some of the routes of insulin administration that are under investigation are oral, buccal, nasal, peritoneal and transdermal. This review article focuses on the past, present and future of various insulin delivery techniques. This article has focused on different possible routes of insulin administration with its advantages and limitation and possible scope for the new drug development.

Mucoadhesive oral films: The potential for unmet needs

Oral drug delivery is the most common route of drug administration. Nevertheless, there are some important limitations that reinforce the need for developing new drug delivery systems. Mucoadhesive oral films (MOF) are promising dosage forms that adhere to the oral mucosa and deliver the drug through it, which present several advantages. These include: bypassing the hepatic first pass effect, fast onset of action, ease of transportation and handling. The use of such dosage form is beneficial for drugs that have poor oral bioavailability and also for drugs that need to be rapidly absorbed. In spite of the known benefits, the number of marketed MOF is still quite small. This review explores the products under development and corresponding clinical trials in respect to their status, therapeutic indication, companies involved and technologies. In this way, it was possible to identify the preferred therapeutic indications, new research and market trends as well as future prospects of MOF. Moreover, it is reasonable to expect an increase in the number of products on the market due to their great potential to satisfy unmet medical needs.

Photoresponsive nanoparticles for drug delivery

Externally triggerable drug delivery systems provide a strategy for the delivery of therapeutic agents preferentially to a target site, presenting the ability to enhance therapeutic efficacy while reducing side effects. Light is a versatile and easily tuned external stimulus that can provide spatiotemporal control. Here we will review the use of nanoparticles in which light triggers drug release or induces particle binding to tissues (phototargeting).

Devices for dry powder drug delivery to the lung

Dry powder inhalers (DPIs) are an important and increasingly investigated method of modern therapy for a growing number of respiratory diseases. DPIs are a promising option for certain patient populations, and may help to overcome several limitations that are associated with other types of inhalation delivery systems (e.g., accuracy and reproducibility of the dose delivered, compliance and adherence issues, or environmental aspects). Today, more than 20 different dry powder inhalers are on the market to deliver active pharmaceutical ingredients (APIs) for local and/or systemic therapy. Depending on the mechanism of deagglomeration, aerosolization, dose metering accuracy, and the interpatient variability, dry powder inhalers demonstrate varying performance levels. During development, manufacturers focus on improving aspects characteristic of their specific DPI devices, depending on the intended type of application and any particular requirements associated with it. With the wide variety of applications related to specific APIs, there exists a range of different devices with distinct features. In addition to the routinely used multi-use DPIs, several single-use disposable devices are under development or already approved. The recent introduction of disposable devices will expand the range of possible applications for use by including agents such as vaccines, analgesics, or even rescue medications. This review article discusses the performance and advantages of recently approved dry powder inhalers as well as disposable single-use inhalers that are currently under development.

pH-sensitive poly(lactide-co-glycolide) nanoparticle composite microcapsules for oral delivery of insulin

This study proposes a new concept of pH-sensitive poly(lactide-co-glycolide) (PLGA) nanoparticle composite microcapsules for oral delivery of insulin. Firstly, insulin–sodium oleate complex was prepared by the hydrophobic ion pairing method and then encapsulated into PLGA nanoparticles by the emulsion solvent diffusion method. In order to reduce the burst release of insulin from PLGA nanoparticles and deliver insulin to specific gastrointestinal regions, hence to enhance bioavailability of insulin, the PLGA nanoparticles were further encapsulated into Eudragit^® FS 30D to prepare PLGA nanoparticle composite microcapsules by organic spray-drying method. The preparation was evaluated in vitro and in vivo, and the absorption mechanism was discussed. The in vitro drug release studies revealed that the drug release was pH dependent, and the in vivo results demonstrated that the formulation of PLGA nanoparticle composite microcapsules was an effective candidate for oral insulin delivery.

Effect of different intestinal conditions on the intermolecular interaction between insulin and cell-penetrating peptide penetratin and on its contribution to stimulation of permeation through intestinal epithelium

Our recent studies have shown that the coadministration of cell-penetrating peptides (CPPs) is a potential strategy for oral delivery of peptide- and protein-based biopharmaceuticals. The intermolecular interaction between drug and CPP is an essential factor in the effective delivery of these drugs, but the characteristics of the interaction under the conditions of the intestinal lumen remain unknown. In this study, therefore, we examined the characteristics of binding of the amphipathic CPP penetratin to insulin and the efficiency of its enhancement of epithelial insulin transport at different pH and in simulated intestinal fluids (SIFs). The binding between insulin and penetratin was pH dependent and particularly decreased at pH 5.0. In addition, we clarified that the sodium taurocholate (NaTC) present in two types of SIF (fasted-state SIF [FaSSIF] and fed-state SIF [FeSSIF]) affected binding efficiency. However, the permeation of insulin through a Caco-2 cell monolayer was significantly facilitated by coincubation with l- or d-penetratin at various pH values. Moreover, the permeation-stimulating effect of l-penetratin was observed in FaSSIF containing NaTC and lecithin, but not in 3mM NaTC solution, suggesting that the presence of lecithin was the key factor in maintaining the ability of penetratin to enhance the intestinal absorption of biopharmaceuticals. This report describes the essential considerations for in vivo use and clinical application of a CPP-based oral delivery strategy.

Potentiation of insulin-mediated glucose lowering without elevated hypoglycemia risk by a small molecule insulin receptor modulator

Insulin resistance is the key feature of type 2 diabetes and is manifested as attenuated insulin receptor (IR) signaling in response to same levels of insulin binding. Several small molecule IR activators have been identified and reported to exhibit insulin sensitization properties. One of these molecules, TLK19781 (Cmpd1), was investigated to examine its IR sensitizing action in vivo. Our data demonstrate that Cmpd1, at doses that produced minimal efficacy in the absence of insulin, potentiated insulin action during an OGTT in non-diabetic mice and enhanced insulin-mediated glucose lowering in diabetic mice. Interestingly, different from insulin alone, Cmpd1 combined with insulin showed enhanced efficacy and duration of action without increased hypoglycemia. To explore the mechanism underlying the apparent glucose dependent efficacy, tissue insulin signaling was compared in healthy and diabetic mice. Cmpd1 enhanced insulin’s effects on IR phosphorylation in both healthy and diabetic mice. In contrast, the compound potentiated insulin’s effects on Akt phosphorylation in diabetic but not in non-diabetic mice. These differential effects on signaling corresponding to glucose levels could be part of the mechanism for reduced hypoglycemia risk. The in vivo efficacy of Cmpd1 is specific and dependent on IR expression. Results from these studies support the idea of targeting IR for insulin sensitization, which carries low hypoglycemia risk by standalone treatment and could improve the effectiveness of insulin therapies.

How to overcome the limitations of current insulin administration with new non-invasive delivery systems

Non-invasive insulin delivery systems have potential to overcome the most pressing problem regarding effective treatment of diabetic patients: therapy compliance. To overcome this disadvantage, non-invasive routes such as oral, buccal, pulmonary, nasal and transdermal have been proposed. These new routes of insulin administration may help to suppress hypoglycemia episodes and aid to control weight gain and post-meal glucose. Despite all efforts the invasive route remains preferential, since studies on insulin administration by non-invasive routes conducted to date have not demonstrated clinical efficacy and safety, including some products introduced in the market. Therefore, the aim of this review is to make an update of the current state of administration of insulin by non-invasive routes as alternatives to the conventional invasive route.

Competitive binding-accelerated insulin release from a polypeptide nanogel for potential therapy of diabetes

A novel core cross-linked glycopolypeptide nanogel was prepared for glucose-triggered insulin delivery.

Surface functional modification of self-assembled insulin nanospheres for improving intestinal absorption

In this work we fabricated therapeutic protein drugs such as insulin as free-carrier delivery system to improve their oral absorption efficiency. The formulation involved self-assembly of insulin into nanospheres (INS) by a novel thermal induced phase separation method. In consideration of harsh environment in gastrointestinal tract, surface functional modification of INS with ɛ-poly-L-lysine (EPL) was employed to form a core-shell structure (INS@EPL) and protect them from too fast dissociation before their arriving at target uptake sites. Both INS and INS@EPL were characterized as uniformly spherical particles with mean diameter size of 150-300 nm. The process of transient thermal treatment did not change their biological potency retention significantly. In vitro dissolution studies showed that shell cross-linked of INS with EPL improved the release profiles of insulin from the self-assembled nanospheres at intestinal pH. Confocal microscopy visualization and transport experiments proved the enhanced paracellular permeability of INS@EPL in Caco-2 cells. Compared to that of INS, enteral administration of INS@EPL at 20 IU/kg resulted in more significant hypoglycemic effects in diabetic rats up to 12 h. Accordingly, the results indicated that surface functional modification of self-assembled insulin nanospheres with shell cross-linked polycationic peptide could be a promising candidate for oral therapeutic protein delivery.

Physicochemical and formulation developability assessment for therapeutic peptide delivery--a primer

Peptides are an important class of endogenous ligands that regulate key biological cascades. As such, peptides represent a promising therapeutic class with the potential to alleviate many severe disease states. Despite their therapeutic potential, peptides frequently pose drug delivery challenges to scientists. This review introduces the physicochemical, biophysical, biopharmaceutical, and formulation developability aspects of peptides pertinent to the drug discovery-to-development interface. It introduces the relevance of these properties with respect to the delivery modalities available for peptide pharmaceuticals, with the parenteral route being the most prevalent route of administration. This review also presents characterization strategies for oral delivery of peptides with the aim of illuminating developability issues with the drug candidate. A brief overview of other routes of administration, including inhaled, transdermal, and intranasal routes, is provided as these routes are generally preferred by patients over injectables. Finally, this review presents formulation techniques to mitigate some of the developability obstacles associated with peptide delivery. The authors emphasize opportunities for the thoughtful application of pharmaceutical science to the development of peptide drugs and to the general advancement of this promising class of pharmaceuticals.

Semi-interpenetrating network (sIPN) co-electrospun gelatin/insulin fiber formulation for transbuccal insulin delivery

PURPOSE

This work was aimed at developing a semi-interpenetrating network (sIPN) co-electrospun gelatin/insulin fiber scaffold (GIF) formulation for transbuccal insulin delivery.

METHODS

Gelatin was electrospun into fibers and converted into an sIPN following eosin Y-initiated polymerization of polyethylene glycol diacrylate (PEG-DA). The cytocompatibility, degradation rate and mechanical properties were examined in the resulting sIPNs with various ratios of PEG-DA to eosin Y to find a suitable formulation for transbuccal drug delivery. Insulin was co-electrospun with gelatin into fibers and converted into an sIPN-GIF using this suitable formulation. The in vitro release kinetics of insulin was evaluated using ELISA. The bioactivity of released insulin was analyzed in 3T3-L1 preadipocytes using Western blotting and Oil Red O staining. The transbuccal permeability of released insulin was determined using an in vitro porcine oral mucosa model.

RESULTS

The sIPN-GF formulation of GF cross-linked by PEG-DA (1% w/v) with eosin Y (5% v/v) possessed no cytotoxic effect, a moderate degradation rate with degradation half-life of 49 min, and a significant enhancement in mechanical properties. This formulation was used to fabricate sIPN-GIF. Insulin release was extended up to 4 h by sIPN-GIF. The released insulin successfully triggered intracellular AKT phosphorylation and induced adipocyte differentiation in 3T3-L1 preadipocytes. The transbuccal permeability of released insulin was determined on the order of 10(-7) cm/s.

CONCLUSIONS

Insulin can be fabricated into an sIPN-GIF formulation following co-electrospinning and cross-linking without losing bioactivity. It proved the potential of this new formulation for transbuccal insulin delivery.

Liposomal nanohybrid cerasomes for controlled insulin release

This study reported a facile fabrication of a reproducible and injectable cerasomal insulin formulation by encapsulating insulin into cerasomes via one-step construction.

Manufacturing and device options for the delivery of biotherapeutics

Biotherapeutic aerosol formulations are an intense area of interest for systemic and local drug delivery. This article provides a short overview of typical factors required specifically for biotherapeutic aerosol formulation design, the processing options open for consideration, and the issue of inhalation device selection. Focusing on spray drying, four case studies are used to highlight the relevant issues, describing investigations into: (1) the mechanical stresses occurring in bacteriophage formulations during spray-dryer atomization; (2) modeling of the spray-dryer process and droplet drying kinetics, to assist process design and predictions of formulation stability; (3) a predictive approach to the design and processing of a five-component dry powder aerosol formulation; and (4) the survival of bacteriophages after pressurized metered dose inhaler atomization.