Nasal Absorption Of Insulin Research Articles

Effect of Glyceryl Monocaprylate–Modified Chitosan on the Intranasal Absorption of Insulin in Rats

Nasal administration of insulin showed the attractive potential to improve the compliance of diabetic patients and alleviate mild cognitive impairment of Alzheimer's patients. However, the nasal absorption of insulin was not ideal, limiting its therapeutic effect in clinic. This study was to explore the potential of glyceryl monocaprylate–modified chitosan (CS-GMC) on the intranasal absorption of insulin via in vivo pharmacodynamic experiment in conscious rats. It was demonstrated that the absorption-enhancing effect of CS-GMC depended on the existing state of insulin in the formulation, substitution degree of GMC on chitosan and concentration of CS-GMC. Better insulin absorption was achieved when insulin existed in molecular form compared with that in polyelectrolyte complexes. CS-GMC with substitution degree 12% (CS-GMC 12%) was a preferred absorption enhancer, and its absorption enhancing effect increased linearly with the increment of its concentration in the range investigated. Compared with chitosan of the same concentration, CS-GMC12% showed remarkably enhanced and prolonged therapeutic effect up to at least 5 h under the concentration of 0.6% (w/v). CS-GMC12% showed almost no ciliotoxicity to the nasal cilia up to concentration 1.0% (w/v). In conclusion, CS-GMC was a promising absorption enhancer to improve the intranasal absorption of insulin.

Current Therapeutic Strategy in the Nasal Delivery of Insulin: Recent Advances and Future Directions.

Insulin (INS) has been used in the treatment of diabetes mellitus. Due to its large molecular weight and short half-life, it has been usually administered subcutaneously accompanied with side effects such as the possibility of hypoglycemia episodes, weight gain and inadequate post-meal glucose control. In order to overcome these limitations, alternative delivery routes of insulin are expected to provide better safety and compliance for the patient. Non-invasive insulin delivery system represents one of the most challenging goals for pharmaceutical industry. Nasal insulin delivery has been extensively studied as an alternative to subcutaneous injection for the treatment of diabetes. The pharmacokinetic profile of nasal insulin is similar to that obtained by intravenous injection. This review discusses the most recent developments in nasal insulin administration technology. Firstly, the structure and physiology of the nasal cavity are introduced. Then, the advantages and disadvantages of nasal administration are discussed. Next, the methods of enhancing nasal insulin absorption and the dosage forms for insulin nasal administration are described. Furthermore, new therapeutic indications of nasal insulin administration were also investigated. Finally, the future development and respective technology of nasal insulin administration are prospected.

Nasal Absorption of Macromolecules from Powder Formulations and Effects of Sodium Carboxymethyl Cellulose on Their Absorption.

The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules.

One-month subchronic toxicity study of cell-penetrating peptides for insulin nasal delivery in rats

Recently, cell-penetrating peptides (CPPs) based vehicles have been developed for the delivery of different payloads in animals. Our studies have shown that nasal absorption of insulin and other therapeutic peptides and proteins can be improved significantly by co-administration of the CPP penetratin. Successful development of suitable CPP-based delivery systems, however, will depend not only on the efficiency of CPPs to transport therapeutic agents across the biological barriers of the nasal cavity, but also on the risk of adverse effects such as toxicity and undesired immunogenicity, especially in chronic therapy. In this study, we investigated the bioavailability (BA) of insulin and the adverse effects on the nasal mucosa in rats following a long-term dosing regimen of l-penetratin and the novel penetratin analogue “PenetraMax.” Following nasal delivery, a significantly higher BA for insulin (almost 100% relative to subcutaneous (s.c.) injections) was observed for PenetraMax in comparison with the parent penetratin peptide after chronic administrations in rats. Importantly, there was negligible biomarker leakage in nasal lavage fluid and the integrity of the nasal epithelium remained unaffected when PenetraMax was used in long-term multiple administrations. In addition, no significant difference in the release of inflammatory and immunogenicity mediators in plasma was observed after nasal administration of PenetraMax with or without insulin solution. In conclusion, PenetraMax, a novel CPP candidate, can open a new avenue in clinical trials for noninvasive nasal insulin delivery.

On employing a translationally controlled tumor protein-derived protein transduction domain analog for transmucosal delivery of drugs

Protein transduction domains (PTDs) are recognized as promising vehicles for the delivery of macromolecular drugs. We have previously shown that a region in the N-terminus (residues 1–10) of translationally controlled tumor protein (TCTP) contains a PTD (TCTP-PTD), MIIYRDLISH, which can serve as a vehicle for the delivery of macromolecules into the cells and tissues. In the current study, we evaluated the potential and safety of TCTP-PTD and its three mutant analogs as nasal absorption enhancers for delivery of drugs. We conducted this evaluation employing insulin as test drug. We examined the degree to which insulin was absorbed in nasal mucosa and also if any mucosal damage occurs following such nasal delivery of insulin using TCTP-PTDs as a vehicle. The systemic delivery of insulin was assessed by measuring the changes in blood glucose levels after nasal coadministration insulin and four PTDs. Of the three TCTP-PTD analogs examined, one, TCTP-PTD analog (MIIFRALISHKK) significantly enhanced the nasal absorption of insulin in both normal and streptozotocin-induced diabetic mice. The relative pharmacological bioavailability of insulin nasally coadministered with the TCTP-PTD analog was 21.3% relative to the subcutaneous route. Molecular association between insulin and the TCTP-PTD analog was observed by fluorescence resonance energy transfer measurements. The binding between the TCTP-PTD analog and insulin may enable the penetration of insulin through the nasal mucosa. Histological examination of mice nasal mucosa 7days after repeated nasal administration showed no evidence of toxicity at the site of nasal administration. In this study using insulin as a test system we demonstrate that the TCTP-PTD analog offers a promising approach for nasal peptides and protein-drugs delivery.

Basic Studies on the Nasal Delivery of Insulin

Nasal absorption of insulin was discussed to develop a delivery system that targets the systemic circulation or central nervous system. Formation of insulin dimer and hexamer affects not only the diffusivity but also the membrane permeability of insulin via aqueous channels. The Renkin function was used to evaluate penetration pathways of hydrophilic compounds containing insulin through aqueous channels, and pore size and occupancy of the pathways were obtained as the membrane parameters on the basis of the function. Cationic polymers applied on the mucosal membranes as penetration enhancers increased the number of pathways for the hydrophilic compounds in the tight junctions, which suggested that these compounds could be sufficient as additives for the nasal delivery of insulin. However, excess interaction of the cationic enhancers with anionic insulin suppressed insulin permeation, and protection of insulin against degradation in the permeation process was required to improve the nasal absorption. PEGylation of insulin could be a possible way to improve the nasal delivery of insulin. In addition, combination of PEGylated insulin and modified cyclodextrin, which form pseudorotaxanes, can be applicable for further modification of pharmacokinetic and pharmacodynamic properties of insulin. Such well-designed complex systems may be required for specific delivery of insulin to the central nervous system.

Performance of cell-penetrating peptide-linked polymers physically mixed with poorly membrane-permeable molecules on cell membranes

We are investigating a new class of penetration enhancers that enable poorly membrane-permeable molecules physically mixed with them to effectively penetrate cell membranes without their concomitant cellular uptake. Since we previously revealed that poly(N-vinylacetamide-co-acrylic acid) modified with d-octaarginine, which is a typical cell-penetrating peptide, significantly enhanced the nasal absorption of insulin, we examined the performance of the polymers on cell membranes. When Caco-2 cells were incubated with 5(6)-carboxyfluorescein (CF) for 30min, approximately 0.1% of applied CF was internalized into the cells. This poor membrane permeability was dramatically enhanced by d-octaarginine-linked polymers; a 25-fold increase in the cellular uptake of CF was observed when the polymer concentration was adjusted to 0.2mg/mL. None of the individual components, for example, d-octaarginine, had any influence on CF uptake, demonstrating that only d-octaarginine anchored chemically to the polymeric platform enhanced the membrane permeation of CF. The polymer-induced CF uptake was consistently high even when the incubation time was extended to 120min. Confocal laser scanning microphotographs of cells incubated with d-octaarginine-linked polymers bearing rhodamine red demonstrated that the cell outline was stained with red fluorescence. The polymer-induced CF uptake was significantly suppressed by 5-(N-ethyl-N-isopropyl)amiloride, which is an inhibitor of macropinocytosis. Results indicated that d-octaarginine-linked polymers remained on the cell membrane and poorly membrane-permeable CF was continuously internalized into cells mainly via macropinocytosis repeated for the individual peptidyl branches in the polymer backbone.

Systemic delivery of insulin via the nasal route using a new microemulsion system: In vitro and in vivo studies

The main purpose of this study was to investigate the nasal absorption of insulin from a new microemulsion spray preparation in rabbits. The bioavailability of insulin lispro via the nasal route using a W/O microemulsion was found to reach 21.5% relative to subcutaneous administration, whereas the use of an inverse microemulsion as well as a plain solution yielded less than 1% bioavailability. The profile of plasma glucose levels obtained after nasal spray application of the microemulsion (1 IU/kg lispro) was similar to the subcutaneous profile of 0.5 IU/kg at the first 90 min after application and resulted in a 30–40% drop in glucose levels. The microemulsion system was characterized by DLS, TEM, viscosity measurements, and by construction of pseudo-ternary phase diagram. The average droplet size of an insulin-unloaded and insulin-loaded microemulsions containing 20% aqueous phase (surfactants-to-oil ratio = 87:13) was 2 nm and 2.26 nm in diameter, respectively. In addition, the effect of the microemulsion on FITC-labeled insulin permeation was examined across the porcine nasal mucosa in vitro. The permeability coefficient of FITC-insulin via the microemulsion was 0.210 ± 0.048 cm/h with a lag time of 10.9 ± 6.5 min, whereas the permeability coefficient from a plain solution was 0.082 ± 0.043 cm/h with a lag time of 36.3 ± 10.1 min. In view of the absorption differences of insulin between 20%, 50% water-containing microemulsions and an aqueous solution obtained in vitro and in vivo, it has been concluded that the acceleration in the intramucosal transport process is the result of encapsulating insulin within the nano-droplet clusters of a W/O microemulsion, while the microemulsion ingredients seems to have no direct role.

Nasal and rectal delivery of insulin with chitosan and N-trimethyl chitosan chloride

The aim of this study was to evaluate the ability of TMC, with different degrees of quaternization, to increase insulin absorption in vivo following nasal and rectal administration in rats. Two batches of TMC with different degrees of quaternization (TMC-L, 12.3% quaternized and TMC-H, 61.2% quaternized) and chitosan hydrochloride were administered intranasally (0.25 and 0.5% w/v) and rectally (0.5% w/v) with insulin (4 IU/kg body weight), at a pH of 4.40 and 7.40, in rats. Blood samples were taken over a period of 2 h for measurement of blood glucose levels and plasma insulin levels. Local toxicity evaluation was done by histological examination of the nasal and rectal epithelia. At pH 4.40 all these polymers were able to increase nasal and rectal insulin absorption, compared to the control groups. However, at a pH of 7.40, only TMC-H was able to increase the nasal and rectal absorption of insulin. These results relate to the insolubility of chitosan hydrochloride at neutral pH values, while the charge density of TMC-L is still too low for any significant interaction at pH 7.40. Histological evaluation of the nasal and rectal eptihelia shows no changes in the morphology of the cells after exposure to these polymers. Only slight congestion of the nasal submucosa was observed and all these polymers led to a mild increase in mucus secretion at pH 4.40. Highly quaternized TMC proves to be a potent absorption enhancer in vivo, especially at neutral pH values where chitosan salts are ineffective.

Effects of polyamidoamine (PAMAM) dendrimers on the nasal absorption of poorly absorbable drugs in rats

The absorption enhancing effects of polyamidoamine (PAMAM) dendrimers with various concentrations and generations on the nasal absorption of fluorescein isothiocyanate-labeled dextran with an average molecular weight of 4400 (FD4) were initially studied in rats. PAMAM dendrimers with different generations improved the nasal absorption of FD4 and the absorption enhancing effects of PAMAM dendrimers were generation dependent. The rank order of absorption enhancement effects of PAMAM dendrimers was G3 > G2 > G1 > G0. The absorption enhancing effects of PAMAM dendrimers were shown to be concentration dependent for the same generation of PAMAM dendrimers. The nasal membrane toxicity of these PAMAM dendrimers was evaluated by measuring the release of protein and lactate dehydrogenase (LDH) in nasal cavity lavage fluid. PAMAM dendrimers with higher generations and concentrations caused some membrane damage to the nasal tissues, but it was much less than the damage caused by sodium deoxycholate as a positive control. Based on the consideration between the efficacy and safety of PAMAM dendrimers, 1% (w/v) G3 dendrimer with high effectiveness and low toxicity was considered to be a best absorption enhancer for improving the nasal absorption of FD4. 1% (w/v) G3 dendrimer also improved the nasal absorption of macromolecular compounds and drugs including FD10, FD70, insulin and calcitonin. Finally, we measured the zeta potentials of drug solutions with or without PAMAM dendrimers to elucidate their absorption enhancing mechanisms. The zeta potentials of model drug solutions changed to positive by the addition of 1% (w/v) G3 dendrimer. This changing might trigger the absorption enhancing effects of PAMAM dendrimers on the nasal absorption of FDs, insulin and calcitonin, as the first step of mechanisms. In conclusion, 1% (w/v) G3 dendrimer is a promising absorption enhancer for improving the nasal absorption of FDs, insulin and calcitonin without any membrane damage to the nasal tissues.

New strategies to improve the intranasal absorption of insulin

Recently, intranasal delivery of insulin as an alternative route of parenteral administration has been widely studied because it bears close resemblance to the 'pulsatile' pattern of endogenous insulin secretion during meal time. However, insulin is not well absorbed through nasal mucosa because of its large molecular size, hydrophilicity and low permeability through the membrane. This review describes the main barriers preventing nasal insulin absorption, and special attention is given to new approaches to improve the intranasal absorption of insulin, including the application of new safe absorption enhancers and the use of appropriate delivery systems. It seems that bioadhesive delivery systems or water-insoluble powders with absorption enhancers are the most promising methods for intranasal delivery of insulin.

Structural requirements of penetratin absorption enhancement efficiency for insulin delivery

Penetratin, a 16-residue peptide, is used widely as a highly efficient delivery carrier for a wide range of poorly permeable therapeutic cargoes. The crucial structural features of penetratin remain unclear, as demonstrated by the difficulties encountered in designing new molecules. The efficiency in enhancing nasal insulin absorption was compared between l-penetratin and 20 of its analogues in rats. We also measured lactate dehydrogenase (LDH) leakage as an indicator of cytotoxicity and scored the histopathological irritation. Substitution of a cationic residue (Arg or Lys) with Leu or addition of tetra-arginine to the C- or N-terminus of penetratin caused considerable reduction in the enhancing efficiency properties of the modified analogues. Mutual exchanging of Arg and Lys in corresponding analogues produced nearly inactive analogues, although changing Arg to Lys in the same analogue produced similar penetratin activity. In addition, activity was impaired markedly upon modification of penetratin within amphiphilic (Trp) or hydrophobic (Ile and Phe) residues. Chain size-modified analogues lacked the ability to induce nasal insulin absorption. In contrast, rearrangement of the modified analogues by C,N-half-exchange and reverse analogues produced activity similar to that of the original penetratin. The enhancing activity was inhibited almost completely upon sequence arrangement of the resulting analogues. Surprisingly, a shuffle (Arg, Lys fix) 2 analogue increased insulin absorption significantly, reaching a relative bioavailability value 1.85-times that of original penetratin. This analogue caused negligible release of LDH in nasal lavage fluid and maintained the integrity of the nasal respiratory epithelium. In conclusion, modulation of amino acid sequences by fixing the cationic residue positions can augment penetratin-enhanced nasal absorption and may lead to improvements in nasal insulin absorption.

The role of intermolecular interactions with penetratin and its analogue on the enhancement of absorption of nasal therapeutic peptides

We investigated the relationship between intermolecular binding and the ability of novel cell-penetrating peptides (CPPs) to enhance the nasal absorption of therapeutic peptides and proteins. The absorption-enhancing effect of a novel l-penetratin analogue, ‘shuffle (R,K fix) 2’ coadministered with different biotherapeutic peptides was evaluated after nasal administration in rats. Shuffle (R,K fix) 2 significantly increased the nasal absorption of insulin, glucagon-like-peptide-1 (GLP-1) and exendin-4, compared with the absorption seen with l-penetratin. Intermolecular binding was analyzed by surface plasmon resonance (SPR)-based binding assay. The binding characteristics implied that the higher the amount of CPP bound, the greater the nasal drug absorption. In addition, the calculated binding ratio between CPP and drug proved a critical aspect in enhancing the absorption of insulin and GLP-1. This difference in the enhancing effect of CPPs on nasal drug absorption is attributed to the degree of binding with the therapeutic macromolecule.

Chitosan-Alginate Blended Nanoparticles as Carriers for the Transmucosal Delivery of Macromolecules

Nanoparticles intended for use in the transmucosal delivery of macromolecules were prepared by the ionic gelation of chitosan (CS) hydrochloride with pentasodium tripolyphosphate (TPP) and concomitant complexation with sodium alginate (ALG). The incorporation of a small proportion of ALG of increasing molecular weight (M(w); from 4 to 74 kDa) into the nanoparticles led to a monotonic increase in colloidal size from ∼260 to ∼525 nm. This increase in size was regarded as a consequence of the formation of gradually more expanded structures. Insulin, taken as a model peptide, was associated to CS-TPP-ALG nanoparticles with efficiencies in the range of ∼41 to ∼52%, irrespective of the M(w) of the ALG incorporated in the formulation. These CS-TPP-ALG nanoparticles exhibited a capacity to enhance the systemic absorption of insulin after nasal administration to conscious rabbits. Interestingly, it was observed that the duration of the hypoglycaemic response was affected by the ALG's M(w). Briefly, this work describes a new nanoparticulate composition of potential value for increasing nasal insulin absorption.

Influence of heat treatment on spray-dried mixtures of Amioca ® starch and Carbopol ® 974P used as carriers for nasal drug delivery

A mucoadhesive spray-dried starch/poly(acrylic acid) powder underwent different heat treatments in order to induce cross-linking between the functional groups of starch (Amioca ®) and poly(acrylic acid) (Carbopol ® 974P). After heat treatment the water-absorbing capacity, viscosity and elasticity of the mucoadhesive powder increased. NMR analysis in combination with FT-IR indicated that heat treatment induced a low degree of cross-linking between the polymers. Nasal administration of Amioca ®/Carbopol ® 974P powders without heat treatment resulted in an absolute bioavailability in rabbits of 8.2 ± 3.0% for insulin. Due to the difference in water-absorbing capacity (which opened the tight junctions of the nasal mucosa), elasticity and plasticity (which reduced mucociliairy clearance and prolonged residence time) heat treatment at 120 °C improved the bioavailability: 26.4 ± 21.9, 36.5 ± 11.0 and 19.3 ± 17.3% after heat treatment during 30 min, 1 h and 4 h, respectively. Heat treatment at 60 °C was less efficient. This study demonstrated that the nasal insulin absorption improved via heat treatment of the Amioca ®/Carbopol ® 974P powder (prior to the addition of insulin). The bioavailability-enhancing effect of a 1 h heat treatment at 120 °C was confirmed using the same polymer matrix in combination with different drugs (salmon calcitonin, human growth hormone and metoprolol tartrate).

Effect of cell-penetrating peptides on the nasal absorption of insulin

The goal of this study was to evaluate whether cell-penetrating peptides (CPPs) affect the nasal absorption of insulin. L- or D-forms of penetratin, or the L- or D-forms of octaarginine (L- or D-R8), was used as first time for nasal insulin delivery. Furthermore, the concentration of lactate dehydrogenase (LDH) in nasal lavage fluid was determined and a histopathological study of nasal respiratory epithelium was conducted. CPPs dramatically increased nasal insulin absorption, and it was more pronounced for L- and D-penetratin than L- or D-R8. L-penetratin was the most effective promoter of insulin absorption compared with others CPPs. A dose-dependent relationship of L-penetratin and insulin bioavailability was statically significant. The pharmacological availability and bioavailability of nasally administered insulin was up to 76.7% and 50.7% relative to the subcutaneous route, respectively. In contrast, increasing the D-penetratin concentration decreased the efficiency of nasal insulin absorption. There was no significant difference in the release of LDH in nasal lavage fluid and the integrity of nasal respiratory epithelium when L-penetratin was present. In conclusion, these data demonstrate that L-penetratin markedly increased the permeability of insulin across the nasal membrane without causing detectable damage to the integrity of cells in the nasal respiratory mucosa.

The addition of calcium ions to starch/Carbopol ® mixtures enhances the nasal bioavailability of insulin

To evaluate the influence of calcium poly(acrylates) on the nasal absorption of insulin in rabbits, starch/poly(acrylic acid) (ratio 25/75) (SD 25/75) was neutralised with NaOH and/or Ca(OH) 2. After neutralisation, a mixture of sodium and/or calcium carboxylate was formed depending on the Ca(OH) 2 concentration in the formulation. IR spectroscopy confirmed that most of the calcium molecules in the formulation interacted with acid groups of the acrylic acid polymer. Addition of Ca(OH) 2 to aqueous dispersions containing starch/poly(acrylic acid) yielded powders with an enhanced absorption of insulin after nasal delivery to rabbits in comparison with the equivalent powder without Ca(OH) 2. A mixture of SD 25/75 and Ca(OH) 2 at a ratio of 90/10 neutralised to pH 7.4 with NaOH induced the highest absorption of insulin, obtaining a bioavailability of ±29% (vs. 19% for an equivalent formulation without Ca(OH) 2). This increase in nasal delivery was possibly due to a higher elasticity after dispersing this formulation in nasal fluid and to a higher water absorbing capacity. Furthermore, after nasal delivery of (SD 25/75)/Ca(OH) 2 90/10, a decrease in t max was observed, possibly due to a progressive dissociation of Ca 2+-ions after hydration of the powder resulting in the closing of the tight junctions.

Nasal residence of insulin containing lyophilised nasal insert formulations, using gamma scintigraphy

Bioadhesive dosage forms are a potential method for overcoming rapid mucociliary transport in the nose. A lyophilised nasal insert formulation previously investigated in sheep demonstrated prolonged absorption of nicotine hydrogen tartrate suggestive of extended nasal residence, and increased bioavailability. The current study was performed to quantify nasal residence of the formulations using gamma scintigraphy, and to investigate the absorption of a larger molecule, namely insulin. A four-way crossover study was conducted in six healthy male volunteers, comparing a conventional nasal spray solution with three lyophilised nasal insert formulations (1–3% hydroxypropylmethylcellulose (HPMC)). The conventional nasal spray deposited in the posterior nasal cavity in only one instance, with a rapid clearance half-life of 9.2 min. The nasal insert formulations did not enhance nasal absorption of insulin, however an extended nasal residence time of 4–5 h was observed for the 2% HPMC formulation. The 1% HPMC insert initially showed good spreading behaviour; however, clearance was faster than for the 2% formulation. The 3% HPMC nasal insert showed no spreading, and was usually cleared intact from the nasal cavity within 90 min. In conclusion, the 2% HPMC lyophilised insert formulation achieved extended nasal residence, demonstrating an optimum combination of rapid adhesion without over hydration.

Effects of a sperminated gelatin on the nasal absorption of insulin

The effects of a sperminated gelatin (SG), which was prepared as a candidate absorption enhancer by the addition of spermine to gelatin, on the nasal absorption of insulin, were examined in rats. The AUC of immuno-reactive insulin levels in the plasma after nasal administration of insulin were increased 5.3-fold by addition of 0.2% SG, and the plasma glucose levels fell in a manner dependent on the insulin levels. In Calu-3 cell monolayer permeation experiments, SG showed significant enhancing effects on 5(6)-carboxyfluorescein (CF), FITC-dextran (MW 4400, FD4) and insulin. Evaluation of the tight junctions in the Calu-3 cell monolayers based on the Renkin molecular sieving function suggests that the pore occupancy/length ratio of the permeation pathways for water-soluble molecules in the tight junctions increases, while the equivalent cylindrical pore radius is not changed by SG treatment. SG may transform the true tight junctions, which act as a barrier for water-soluble molecules, into pathways for CF and FD4 to increase their number. SG is a good candidate for a safe absorption enhancer to produce a slight modification of the permeability of the paracellular pathway of mucosal membranes, while retaining the sieving property of the epithelial membranes.

Isolation, characterization and study of enhancing effects on nasal absorption of insulin in rat of the total saponin from Acanthophyllum squarrosum

<b>Objective: </b> Isolation of the total saponins from Acanthophyllum squarrosum Boiss. and investigation of its surface activity, haemolytic effects on human erythrocytes, as well as enhancing potentials on intranasal insulin absorption in rat as compared to two other enhancers, i.e, Quillaja total saponin (QTS) and sodium cholate (SC).<br><b> Materials and Methods:</b> The decrease in blood glucose levels in five fasting rats following nasal administration of regular insulin solutions in the presence or absence of enhancers was determined by glucometric strips and used as an indication of insulin absorption.<br><b> Results: </b> The results showed that Acanthophyllum total saponin (ATS) decreased surface tension of water to about 50 dyne/cm and caused complete haemolysis of human RBCs at a concentration of 250 µg/ml. Following the instillation of solutions containing insulin and different absorption enhancers into the right nostril of rats, the percentage decrease in initial blood glucose was as follows: 72.46% (±2.39%) for ATS, 63.22% (±11.06%) for QTS and 60.06% (±14.93%) for SC. Percentage lowering of initial blood glucose concentrations against time showed that ATS exerts a stronger effect than the two other enhancers, although the difference was not statistically significant (P > 0.05).<br><b> Conclusion: </b> ATS has a considerable absorption enhancing effect and can possibly be used to increase insulin bioavailability via the nasal route. However, the potential toxic effects of this saponin on nasal mucosa should be further evaluated.