Permeation Of Insulin Research Articles

In-vitro and in-vivo cytotoxicity and efficacy evaluation of novel glycyl-glycine and alanyl-alanine conjugates of chitosan and trimethyl chitosan nano-particles as carriers for oral insulin delivery

PurposeThe aim of this research work was to explore the possibility of providing multifunctional oral insulin delivery system by conjugating several types of dipeptides on chitosan and trimethyl chitosan to be used as drug carriers. MethodConjugates of Glycyl-glycine and alanyl-alanine of chitosan and trimethyl chitosan (on primary alcohol group of polymer located on carbon 6) were synthesized and nanoparticles containing insulin were prepared for oral delivery. Preparation conditions of nanoparticles were optimized and their performance to enhance the permeability of insulin as well as cytotoxicity of nanoparticles in Caco-2 cell line was evaluated. To evaluate the efficacy of orally administered nanoparticles, nanoparticles with the most permeability enhancing ability were studied in male Wistar rats as animal model by measuring insulin and glucose Serum levels. ResultStructural study of all the conjugates by infrared spectroscopy and nuclear magnetic resonance confirmed the successful formation of the conjugates with the desirable substitution degree. By optimizing preparation conditions, nanoparticles with expected size (157.3–197.7 nm), Zeta potential (24.35–34.37 mV), polydispersity index (0.365–0.512), entrapment efficiency (70.60–86.52%) and loading capacity (30.92–56.81%), proper morphology and desirable release pattern were obtained. Glycyl-glycine and alanyl-alanine conjugate nanoparticles of trimethyl chitosan showed 2.5–3.3 folds more effective insulin permeability in Caco-2 cell line than their chitosan counterparts. In animal model, oral administration of glycyl-glycine and alanyl-alanine conjugate nanoparticles of trimethyl chitosan demonstrated reasonable increase in Serum insulin level with relative bioavailability of 17.19% and 15.46% for glycyl-glycine and alanyl-alanine conjugate nanoparticles, respectively, and reduction in Serum glucose level compared with trimethyl chitosan nanoparticles (p < 0.05). ConclusionIt seems that glycyl-glycine and alanyl-alanine conjugate nanoparticles of trimethyl chitosan have met the aim of this research work and have been able to orally deliver insulin with more than one mechanism in animal model. Hence, they are promising candidates for further research studies.

Central nervous insulin administration before nocturnal sleep decreases breakfast intake in healthy young and elderly subjects

Peripheral insulin acts on the brain to regulate metabolic functions, in particular decreasing food intake and body weight. This concept has been supported by studies in humans relying on the intranasal route of administration, a method that permits the direct permeation of insulin into the CNS without substantial absorption into the blood stream. We investigated if intranasal insulin administration before nocturnal sleep, a period of reduced metabolic activity and largely absent external stimulation, affects food intake and energy turnover on the subsequent morning. Healthy participants who were either young (16 men and 16 women; mean age ± SEM, 23.68 ± 0.40 years, mean BMI ± SEM, 22.83 ± 0.33 kg/m2) or elderly (10 men, 9 women; 70.79 ± 0.81 years, 25.27 ± 0.60 kg/m2) were intranasally administered intranasal insulin (160 IU) or placebo before a night of regular sleep that was polysomnographically recorded. Blood was repeatedly sampled for the determination of circulating glucose, insulin, leptin and total ghrelin. In the morning, energy expenditure was assessed via indirect calorimetry and subjects were offered a large standardized breakfast buffet from which they could eat ad libitum. Insulin compared to placebo reduced breakfast size by around 110 kcal (1054.43 ± 50.91 vs. 1162.36 ± 64.69 kcal, p = 0.0095), in particular decreasing carbohydrate intake (502.70 ± 25.97 vs. 589.82 ± 35.03 kcal, p = 0.0080). This effect was not dependent on sex or age (all p > 0.11). Sleep architecture, blood glucose and hormonal parameters as well as energy expenditure were not or only marginally affected. Results show that intranasal insulin administered to healthy young and elderly humans before sleep exerts a delayed inhibitory effect on energy intake that is not compensated for by changes in energy expenditure. While the exact underlying mechanisms cannot be derived from our data, findings indicate a long-lasting catabolic effect of central nervous insulin delivery that extends across sleep and might be of particular relevance for potential therapeutic applications.

Islet encapsulated implantable composite hollow fiber membrane based device: A bioartificial pancreas

Islets from xeno-sources and islet like clusters derived from autologus stem cells have emerged as alternatives to cadaveric pancreas used for treatment of type 1 diabetes. However, the immuno-isolation of these islets from the host immune system suffers from the issue of biocompatibility and hypoxia. To overcome the issues of immunobarrier biocompatibility, we developed a Polysulfone (Psf)/TPGS composite hollow fiber membrane (HFM) using a hollow fiber spinning pilot plant specially developed for this purpose. Important structural variables such as fiber material, dope composition, dimensions, surface characteristics etc., were precisely engineered and tuned for bioartificial pancreas application. The HFMs were characterized for their morphology, molecular diffusion, selectivity and protein absorption. The optimized Polysulfone(Psf)/TPGS composite HFMs, which contained TPGS, exhibited uniformed structure with low insulin adsorption and high permeability of insulin. The HFM was further studied for the encapsulation and in-vitro growth with porcine and differentiated islets isolated from human umbilical cord Wharton's jelly.To prove their efficacy under in-vivo conditions, the Polysulfone(Psf)/TPGS composite HFMs were encapsulated with either of these isolated cells (porcine islets or islet like cell clusters derived from mesenchymal stem cells isolated from human umbilical cord Wharton's jelly) and they were transplanted in experimental STZ induced diabetic mice. The results showed restoration of normoglycemia for 30days, indicating their ability to respond efficiently to high glucose without immune-rejection. Thus, these results indicate that Polysulfone (Psf)/TPGS composite HFMs can be used as an implantable, immune-competent bioartificial pancreas as a therapy for type 1 diabetes.

Transdermal Protein Delivery Using Choline and Geranate (CAGE) Deep Eutectic Solvent.

Transdermal delivery of peptides and other biological macromolecules is limited due to skin's inherent low permeability. Here, the authors report the use of a deep eutectic solvent, choline and geranate (CAGE), to enhance topical delivery of proteins such as bovine serum albumin (BSA, molecular weight: ≈66 kDa), ovalbumin (OVA, molecular weight: ≈45 kDa) and insulin (INS, molecular weight: 5.8 kDa). CAGE enhances permeation of BSA, OVA, and insulin into porcine skin ex vivo, penetrating deep into the epidermis and dermis. Studies using tritium-labeled BSA and fluorescein isothiocyanate labeled insulin show significantly enhanced delivery of proteins into and across porcine skin, penetrating the skin in a time-dependent manner. Fourier transform IR spectra of porcine stratum corneum (SC) samples before and after incubation in CAGE show a reduction in peak area attributed to SC lipid content, suggesting lipid extraction from the SC. Circular dichroism confirms that CAGE does not affect insulin's secondary conformation. In vivo studies in rats show that topical application of 10 U insulin dispersed in CAGE (25 U kg-1 insulin dose) leads to a highly significant 40% drop in blood glucose levels in 4 h that is relatively sustained for 12 h. Taken together, these studies demonstrate that CAGE is a promising vehicle for transdermal delivery of therapeutic proteins; specifically, as a noninvasive delivery alternative to injectable insulin for the treatment of diabetes.

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.

Central Nervous Insulin Administration before Nocturnal Sleep Decreases Breakfast Intake in Healthy Young and Elderly Subjects.

Peripheral insulin acts on the brain to regulate metabolic functions, in particular decreasing food intake and body weight. This concept has been supported by studies in humans relying on the intranasal route of administration, a method that permits the direct permeation of insulin into the CNS without substantial absorption into the blood stream. We investigated if intranasal insulin administration before nocturnal sleep, a period of reduced metabolic activity and largely absent external stimulation, affects food intake and energy turnover on the subsequent morning. Healthy participants who were either young (16 men and 16 women; mean age ± SEM, 23.68 ± 0.40 years, mean BMI ± SEM, 22.83 ± 0.33 kg/m2) or elderly (10 men, 9 women; 70.79 ± 0.81 years, 25.27 ± 0.60 kg/m2) were intranasally administered intranasal insulin (160 IU) or placebo before a night of regular sleep that was polysomnographically recorded. Blood was repeatedly sampled for the determination of circulating glucose, insulin, leptin and total ghrelin. In the morning, energy expenditure was assessed via indirect calorimetry and subjects were offered a large standardized breakfast buffet from which they could eat ad libitum. Insulin compared to placebo reduced breakfast size by around 110 kcal (1,054.43 ± 50.91 vs. 1,162.36 ± 64.69 kcal, p = 0.0095), in particular decreasing carbohydrate intake (502.70 ± 25.97 vs. 589.82 ± 35.03 kcal, p = 0.0080). This effect was not dependent on sex or age (all p > 0.11). Sleep architecture, blood glucose and hormonal parameters as well as energy expenditure were not or only marginally affected. Results show that intranasal insulin administered to healthy young and elderly humans before sleep exerts a delayed inhibitory effect on energy intake that is not compensated for by changes in energy expenditure. While the exact underlying mechanisms cannot be derived from our data, findings indicate a long-lasting catabolic effect of central nervous insulin delivery that extends across sleep and might be of particular relevance for potential therapeutic applications.

Polypeptide-based polyelectrolyte complexes overcoming the biological barriers of oral insulin delivery

Abstract In this study, a novel oral insulin delivery system was prepared by combining two different artificial polypeptides with insulin. Negatively charged poly( l -glutamate- co - N -3- l -glutamylsulfanilic acid) (PLGS), cationic alpha helical peptide poly- l -lysine (PLL), and insulin formed polyelectrolyte complexes (PCs) were characterized. The property of the PCs was examined by an in vitro study. A significantly higher amount of the loaded FITC insulin was released in the intestinal condition, suggesting the controlled release of the PCs to protect insulin in the acidic stomach condition while releasing it in the small intestine. The in vitro cellular uptake study with Caco-2 cells also revealed the improved penetration of the loaded FITC labeled insulin. By virtue of the cell penetration enhancing ability of PLL, the permeation of insulin in the small intestine was notably augmented. Furthermore, the feasibility of the PCs was confirmed through an in vivo hypoglycemic effect study. The PCs showed an improved hypoglycemic effect suggesting the success of the delivery and penetration of the loaded insulin. The blood glucose level was lowered to 80% of its initial value after the oral administration of the PCs, and the hypoglycemia lasted for more than 14 h. The long lasting hypoglycemic effect of the PCs can reduce the number of administrations, and it will contribute to improving the quality of patients’ lives. The PCs provided reasonable results as a competitive candidate for oral insulin delivery. The introduction of the PCs will promote the oral delivery of charged proteins or drugs.

Progress and challenges of the bioartificial pancreas.

Pancreatic islet transplantation has been validated as a treatment for type 1 diabetes since it maintains consistent and sustained type 1 diabetes reversal. However, one of the major challenges in pancreatic islet transplantation is the body’s natural immune response to the implanted islets. Immunosuppressive drug treatment is the most popular immunomodulatory approach for islet graft survival. However, administration of immunosuppressive drugs gives rise to negative side effects, and long-term effects are not clearly understood. A bioartificial pancreas is a therapeutic approach to enable pancreatic islet transplantation without or with minimal immune suppression. The bioartificial pancreas encapsulates the pancreatic islets in a semi-permeable environment which protects islets from the body’s immune responses, while allowing the permeation of insulin, oxygen, nutrients, and waste. Many groups have developed various types of the bioartificial pancreas and tested their efficacy in animal models. However, the clinical application of the bioartificial pancreas still requires further investigation. In this review, we discuss several types of bioartificial pancreases and address their advantages and limitations. We also discuss recent advances in bioartificial pancreas applications with microfluidic or micropatterning technology.

In vivo skin penetration of macromolecules in irritant contact dermatitis

Recently, a selective preferential accumulation of polymeric nanoparticles (in the size range around 100nm) has been observed in the follicular system of dermatitis skin. The present investigation aimed at clearly investigating the effect of irritant contact dermatitis on the barrier permeability for colloidal systems below this size range, namely quantum dots and hydrophilic macromolecules. Irritant dermatitis was induced in mice and the penetrability of quantum dots (5nm) and hydrophilic dextran molecules has been tracked in both healthy and inflamed skin using confocal laser scanning microscopy. The selective accumulation of the quantum dots was clearly observed in inflamed skin while hydrophilic dextran behaved similarly in both healthy and inflamed skin. The therapeutic potential for the transdermal delivery of peptide drugs through inflamed skin has been also tested in rats. Results revealed that the transdermal permeation of insulin and calcitonin was not significantly enhanced in dermatitis compared to healthy skin. On the other side, permeation through stripped skin was significantly higher. However, the effect was limited and shorter compared to the SC injection where tmin was 0.5h and 2h with a 70% and 46% reduction in blood glucose levels for the stripped skin and the SC injection respectively. Similarly, tmin was 4h and 8h with area under the curve of 161±65% and 350±97% for the stripped skin and the SC injection respectively. In conclusion, the changes in skin permeability accompanied with skin inflammation did not affect its permeability to peptide drugs. Our findings also underline that experiments with the tape stripped skin model as a surrogate for inflamed skin can risk misleading conclusions due to significant difference of skin permeability between the tape stripped skin and inflamed skin.

Corrigendum: Pre-formulation and systematic evaluation of amino acid assisted permeability of insulin across in vitro buccal cell layers.

Scientific Reports 6: Article number: 32498; published online: 01 September 2016; updated: 14 October 2016

Pre-formulation and systematic evaluation of amino acid assisted permeability of insulin across in vitro buccal cell layers.

The aim of this work was to investigate alternative safe and effective permeation enhancers for buccal peptide delivery. Basic amino acids improved insulin solubility in water while 200 and 400 μg/mL lysine significantly increased insulin solubility in HBSS. Permeability data showed a significant improvement in insulin permeation especially for 10 μg/mL of lysine (p < 0.05) and 10 μg/mL histidine (p < 0.001), 100 μg/mL of glutamic acid (p < 0.05) and 200 μg/mL of glutamic acid and aspartic acid (p < 0.001) without affecting cell integrity; in contrast to sodium deoxycholate which enhanced insulin permeability but was toxic to the cells. It was hypothesized that both amino acids and insulin were ionised at buccal cavity pH and able to form stable ion pairs which penetrated the cells as one entity; while possibly triggering amino acid nutrient transporters on cell surfaces. Evidence of these transport mechanisms was seen with reduction of insulin transport at suboptimal temperatures as well as with basal-to-apical vectoral transport, and confocal imaging of transcellular insulin transport. These results obtained for insulin are the first indication of a possible amino acid mediated transport of insulin via formation of insulin-amino acid neutral complexes by the ion pairing mechanism.

ZOT-derived peptide and chitosan functionalized nanocarrier for oral delivery of protein drug.

In this study, we developed a dual ligand functionalized pluronic-based nanocarrier (NC) for oral delivery of insulin. Chitosan and zonula occludins toxin (ZOT)-derived, tight junction opening peptide were conjugated to NC to increase the permeability of loaded insulin across the small intestine through the paracellular pathway. Surface functionalized NC, either by chitosan or peptide, could modulate the tight junction (TJ) integrity in contrast to no effect of unmodified NC, as evidenced by the change in transepithelial electrical resistance (TEER) and immunostaining of Claudin-4, a tight junction marker, in Caco-2cell monolayer. On the other hand, dual ligand (chitosan and peptide) functionalized NC significantly further increased the permeation of insulin across Caco-2cell monolayer. More importantly, insulin loaded, dual ligand functionalized NC could increase the plasma insulin level and efficiently regulate the glycemic response for a prolonged period of time (∼1 day) upon oral administration to diabetic rats, whereas delivery of insulin by single ligand functionalized NCs, either by chitosan or peptide, as well as by unmodified NC and free insulin, could not induce the effective regulation of the blood glucose level. The use of fluorescence dye labeled insulin (FITC-insulin) and Cy5.5 labeled NC revealed that both insulin and dual ligand functionalized NC were adequately penetrated across the whole intestine villi in contrast to limited adsorption of insulin and NC mainly onto the epithelial surface of the intestine for single ligand functionalized NCs. These results suggest that dual conjugation of ZOT-derived peptide and chitosan is a promising approach to functionalize the surface of nanocarrier for oral delivery of protein drugs.

Thiolation and Cell‐Penetrating Peptide Surface Functionalization of Porous Silicon Nanoparticles for Oral Delivery of Insulin

During the last decades, advanced oral delivery systems to enhance the intestinal absorption of widely applicable proteins and peptides, particularly insulin, have been developed. Here, chitosan‐conjugated undecylenic acid‐modified thermally hydrocarbonized porous silicon nanoparticles (CSUn NPs) are used, which promote the mucoadhesion and cellular interactions, thus boosting the intestinal permeability of insulin. Then, to further potentiate the mucoadhesion and permeability enhancement of chitosan‐modified NPs, the surface of the NPs is further modified with either l‐cysteine (CYS‐CSUn NPs) or a cell‐penetrating peptide (CPP‐CSUn NPs). CYS‐CSUn and CPP‐CSUn NPs show 17‐ and 12‐fold increase in the apparent permeability of insulin across cellular intestinal cells, respectively, with significant enhancement in the cellular interactions. The insulin uptake mechanism pathways in intestinal cells from the developed NPs are also unraveled, which demonstrates major involvement of active transport process and electrostatic interactions, along with adsorptive and clathrin‐mediated endocytic pathways. Moreover, after oral administration in diabetic rats, CYS‐CSUn NPs show 1.86‐ and 2.03‐fold increase in the relative bioavailability of insulin, as compared to empty NPs and oral insulin solution, respectively. In conclusion, this study presents l‐cysteine modified CSUn NPs as a promising strategy with the ability to overcome the multiple barriers for oral delivery 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.

Impact of Lipid-Based Drug Delivery Systems on the Transport and Uptake of Insulin Across Caco-2 Cell Monolayers

Self-(nano)-emulsifying drug delivery systems (SNEDDSs) used to deliver peptides and proteins across biological barriers, such as the small intestinal membrane, represents an increasingly interesting field in nanomedicine. Hence, the present study was designed to evaluate the impact of SNEDDS on the transport and uptake mechanisms of insulin across the intestinal membrane. For this purpose, 3 SNEDDS were prepared, and Caco-2 cell monolayers were used to study transport and uptake. The prepared SNEDDSs were all in the range of 35-50 nm and had a negative zeta potential (between −8 and −25 mV). The entrapment of insulin on dispersion in the experimental media ranged from 40% to 78% for all SNEDDSs. Fluorescent microscopy studies indicated that fluorescein isothiocyanate–labeled insulin when administered in solution, as well as when loaded into MCT1 or MCT2 SNEDDS, localized within the intercellular space of the Caco-2 cell monolayer, indicating transport by paracellular diffusion. In contrast, the fluorescein isothiocyanate–labeled insulin in LCT SNEDDS was taken up by the cells. In conclusion, the present study demonstrated that MCT1 and MCT2 SNEDDS, but not LCT SNEDDS increased the transepithelial permeability of insulin, via the paracellular route.

A Novel Drug Delivery System for the Human Nasal Epithelium.

The epithelium of upper respiratory tissues such as the human nasal mucosa forms a continuous barrier via tight junctions (TJs). The development of a drug delivery system for use across the nasal mucosa is being reconsidered. In intranasal administration across the nasal mucosa, the paracellular pathway regulated by TJs is extremely important. It is known that the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) binds the TJ protein claudin and disrupts the tight junctional barrier without inducing a cytotoxic effect. We investigated the effects of C-CPE mutants on the function of TJs of human nasal epithelial cells (HNECs) and on the permeability of human recombinant insulin across HNECs treated with C-CPE 194 and C-CPE m19. We recently reported that C-CPE mutants 194 and m19 can regulate the permeability of insulin across HNECs via the MAPK pathway and may play a crucial role in therapy for various diseases via direct intranasal insulin administration. On the other hand, microRNAs (miRNAs) are known to regulate the expression of TJs as direct or indirect targets in genes to maintain barrier function. We investigated the effects of miRNAs on the epithelial barrier of HNECs and found that miRNA-146a plays crucial roles in the maintenance of the TJ barrier and innate immune response against invading pathogens. This chapter reviews a novel drug delivery system across the nasal mucosa from the point of view of the epithelial barrier function.

Amphiphilic Lipopeptide-Mediated Transport of Insulin and Cell Membrane Penetration Mechanism.

Arginine octamer (R8) and its derivatives were developed in this study for the enhanced mucosal permeation of insulin. R8 was substituted with different aminos, then modified with stearic acid (SA). We found that the SAR6EW-insulin complex had stronger intermolecular interactions and higher complex stability. The amphiphilic lipopeptide (SAR6EW) was significantly more efficient for the permeation of insulin than R8 and R6EW both in vitro and in vivo. Interestingly, different cellular internalization mechanisms were observed for the complexes. When the effectiveness of the complexes in delivering insulin in vivo was examined, it was found that the SAR6EW-insulin complex provided a significant and sustained (six hours) reduction in the blood glucose levels of diabetic rats. The improved absorption could be the comprehensive result of stronger intermolecular interactions, better enzymatic stability, altered internalization pathways, and increased transportation efficacy. In addition, no sign of toxicity was observed after consecutive administrations of SAR6EW. These results demonstrate that SAR6EW is a promising epithelium permeation enhancer for insulin and suggest that the chemical modification of cell-penetrating peptides is a feasible strategy to enhance their potential.

Application of Microneedle Arrays for Enhancement of Transdermal Permeation of Insulin: In Vitro Experiments, Scaling Analyses and Numerical Simulations.

The aim of this investigation is to study the effect of donor concentration and microneedle (MN) length on permeation of insulin and further evaluating the data using scaling analyses and numerical simulations. Histological evaluation of skin sections was carried to evaluate the skin disruption and depth of penetration by MNs. Scaling analyses were done using dimensionless parameters like concentration of drug (C t/C s), thickness (h/L) and surface area of the skin (S a/L (2)). Simulation studies were carried out using MATLAB and COMSOL software to simulate the insulin permeation using histological sections of MN-treated skin and experimental parameters like passive diffusion coefficient. A 1.6-fold increase in transdermal flux and 1.9-fold decrease in lag time values were observed with 1.5mm MN when compared with passive studies. Good correlation (R (2) > 0.99) was observed between different parameters using scaling analyses. Also, the in vitro and simulated permeations profiles were found to be similar (f 2 ≥ 50). Insulin permeation significantly increased with increase in donor concentration and MN length (p < 0.05). The developed scaling correlations and numerical simulations were found to be accurate and would help researchers to predict the permeation of insulin with new dimensions of MN in optimizing insulin delivery. Overall, it can be inferred that the application of MNs can significantly enhance insulin permeation and may be an efficient alternative for injectable insulin therapy in humans.

N-trimethyl chitosan chloride-coated PLGA nanoparticles overcoming multiple barriers to oral insulin absorption.

Although several strategies have been applied for oral insulin delivery to improve insulin bioavailability, little success has been achieved. To overcome multiple barriers to oral insulin absorption simultaneously, insulin-loaded N-trimethyl chitosan chloride (TMC)-coated polylactide-co-glycoside (PLGA) nanoparticles (Ins TMC-PLGA NPs) were formulated in our study. The Ins TMC-PLGA NPs were prepared using the double-emulsion solvent evaporation method and were characterized to determine their size (247.6 ± 7.2 nm), ζ-potential (45.2 ± 4.6 mV), insulin-loading capacity (7.8 ± 0.5%) and encapsulation efficiency (47.0 ± 2.9%). The stability and insulin release of the nanoparticles in enzyme-containing simulated gastrointestinal fluids suggested that the TMC-PLGA NPs could partially protect insulin from enzymatic degradation. Compared with unmodified PLGA NPs, the positively charged TMC-PLGA NPs could improve the mucus penetration of insulin in mucus-secreting HT29-MTX cells, the cellular uptake of insulin via clathrin- or adsorption-mediated endocytosis in Caco-2 cells and the permeation of insulin across a Caco-2 cell monolayer through tight junction opening. After oral administration in mice, the TMC-PLGA NPs moved more slowly through the gastrointestinal tract compared with unmodified PLGA NPs, indicating the mucoadhesive property of the nanoparticles after TMC coating. Additionally, in pharmacological studies in diabetic rats, orally administered Ins TMC-PLGA NPs produced a stronger hypoglycemic effect, with 2-fold higher relative pharmacological availability compared with unmodified NPs. In conclusion, oral insulin absorption is improved by TMC-PLGA NPs with the multiple absorption barriers overcome simultaneously. TMC-PLGA NPs may be a promising drug delivery system for oral administration of macromolecular therapeutics.

Biological assessment of self-assembled polymeric micelles for pulmonary administration of insulin

Pulmonary delivery of drugs for both local and systemic action has gained new attention over the last decades. In this work, different amphiphilic polymers (Soluplus®, Pluronic® F68, Pluronic® F108 and Pluronic® F127) were used to produce lyophilized formulations for inhalation of insulin. Development of stimuli-responsive, namely glucose-sensitive, formulations was also attempted with the addition of phenylboronic acid (PBA). Despite influencing the in vitro release of insulin from micelles, PBA did not confer glucose-sensitive properties to formulations. Lyophilized powders with aerodynamic diameter (<6μm) compatible with good deposition in the lungs did not present significant in vitro toxicity for respiratory cell lines. Additionally, some formulations, in particular Pluronic® F127-based formulations, enhanced the permeation of insulin through pulmonary epithelial models and underwent minimal internalization by macrophages in vitro. Overall, formulations based on polymeric micelles presenting promising characteristics were developed for the delivery of insulin by inhalation. From the Clinical EditorThe ability to deliver other systemic drugs via inhalation has received renewed interests in the clinical setting. This is especially true for drugs which usually require injections for delivery, like insulin. In this article, the authors investigated their previously developed amphiphilic polymers for inhalation of insulin in an in vitro model. The results should provide basis for future in vivo studies.