Improvement of pulmonary absorption of insulin and other water-soluble compounds by polyamines in rats

Versatile Oral Insulin Delivery Nanosystems: From Materials to Nanostructures

Diabetes is a chronic metabolic disease characterized by lack of insulin in the body leading to failure of blood glucose regulation. Diabetes patients usually need frequent insulin injections to maintain normal blood glucose levels, which is a painful administration manner. Long-term drug injection brings great physical and psychological burden to diabetic patients. In order to improve the adaptability of patients to use insulin and reduce the pain caused by injection, the development of oral insulin formulations is currently a hot and difficult topic in the field of medicine and pharmacy. Thus, oral insulin delivery is a promising and convenient administration method to relieve the patients. However, insulin as a peptide drug is prone to be degraded by digestive enzymes. In addition, insulin has strong hydrophilicity and large molecular weight and extremely low oral bioavailability. To solve these problems in clinical practice, the oral insulin delivery nanosystems were designed and constructed by rational combination of various nanomaterials and nanotechnology. Such oral nanosystems have the advantages of strong adaptability, small size, convenient processing, long-lasting pharmaceutical activity, and drug controlled-release, so it can effectively improve the oral bioavailability and efficacy of insulin. This review summarizes the basic principles and recent progress in oral delivery nanosystems for insulin, including physiological absorption barrier of oral insulin and the development of materials to nanostructures for oral insulin delivery nanosystems.

Spermine with Sodium Taurocholate Enhances Pulmonary Absorption of Macromolecules in Rats

The improvement effect of the combined use of spermine (SPM), a polyamine, with sodium taurocholate (STC) on the pulmonary drug absorption was investigated utilizing poorly absorbable drugs with various molecular sizes in rats. The pulmonary absorption of rebamipide, a low molecular but poorly absorbable drug after oral administration, was significantly improved by the combined use of SPM with STC (SPM-STC formulation), while poly- L-lysine did not show a significant change in rebamipide absorption from the lungs. Furthermore, the safety of the SPM-STC formulation for the lungs was assessed in rats by the histopathological study and any local toxicity was not observed while poly-L-lysine, a typical chemical causing the toxicity for the epithelial cells, provided several histopathological changes. In addition, the SPM-STC formulation significantly improved the pulmonary absorption of fluorescein isothiocyanate dextran 4 (FD-4, Mw ca 4000) and interferon-α (IFN-α, Mw ca 25,000) as well. Our present results clearly indicated that the SPM-STC formulation significantly improved the pulmonary absorption of poorly absorbable small and large molecular drugs without any harmful effects on the lungs. Therefore, the SPM-STC formulation would be a useful one for the pulmonary absorption of drugs, specifically macromolecular ones, which are very difficult to be absorbed after oral administration.

DSPE-PEG polymers for improving pulmonary absorption of poorly absorbed macromolecules in rats and relative mechanism

OBJECTIVE

This study aims to investigate the potential of DSPE-PEG polymers (DSPE-PEG-OH and DSPE-PEG-SH) on improving absorption of poorly absorbable macromolecules via intrapulmonary administration and underlying mechanism.

METHODS

In situ pulmonary absorption experiments were performed to investigate the absorption of model compounds after intrapulmonary administration to rats. The local membrane damage induced by these DSPE-PEG polymers were evaluated based on morphological observation of lung tissues and measurement of biological toxic markers in bronchoalveolar lavage fluid (BALF) postintrapulmonary delivery of DSPE-PEG polymers to rats. The underlying enhancement mechanism of these polymers was explored by investigating their effects on the pulmonary membrane fluidity and gene expression of tight junction associated proteins with fluorescence polarization and western blotting, respectively.

RESULTS

Intrapulmonary delivery of these DSPE-PEG polymers significantly enhanced absorptions of poorly absorbed model drugs and did not induce serious damage to the pulmonary membranes of rats. Mechanistic studies demonstrated unaffected pulmonary membrane fluidity and up-regulated expression levels of tight junction-associated proteins by DSPE-PEG polymers, thus indicating that paracellular pathways might be included in the underlying mechanisms by which DSPE-PEG polymers exerted their enhancing actions on drug absorption.

CONCLUSIONS

These findings suggested that these DSPE-PEG polymers are potential for promoting absorptions of poorly absorbable macromolecules with no evidence of damage to the local pulmonary membranes of rats.Novelty statementIn this study, DSPE-PEG-OH and DSPE-PEG-SH polymers, two DSPE-PEG2000 conjugates with different terminal groups demonstrated significant promoting effects on the absorption of poorly absorbed macromolecular drugs after intrapulmonary delivery to rats, and did not induce serious damage to the pulmonary membranes of rats. These DSPE-PEG polymers could statistically downregulate expression levels of tight junction-associated proteins (ZO-1 and occludin), indicating the underlying mechanism by which these polymers exerted their absorption enhancing actions through pulmonary epithelial paracellular pathways. Thus, this study exhibited prospective potential of these DSPE-PEG polymers in developing into dosage forms with the aim to improve the poor bioavailability of some poorly absorbed macromolecular drugs.

Efficacy of SPM-NONOate following intrapulmonary delivery in promoting absorptions of poorly absorbed macromolecules in rats and the underling mechanism

This research aims to investigate the potential of N-[4-[1-(3-Aminopropyl)-2-hydroxy-2-nitrosohydrazino]butyl]-1,3-propanediamine (SPM-NONOate) for promoting the absorption of poorly absorbed macromolecules delivered by intrapulmonary route. Influence of SPM-NONOate on the drug absorption was characterized by using a series of fluorescein isothiocyanate-labeled dextrans (FDs) as affordable models of hydrophilic macromolecules with established tools for quantitative analysis. SPM-NONOate increased concentration-dependently within 1-10 mM the pulmonary absorptions of FDs in rats. Moreover, this promoting effect varied with the molecular weight of FDs, and the largest absorption enhancement effect was obtained for FD70. SPM-NONOate also showed promising enhancement potential on the absorption of some therapeutic peptides, where obvious hypoglycemic and hypocalcemic effects were observed after intrapulmonary delivery of insulin and calcitionin, respectively, with SPM-NONOate to rats. The safety of SPM-NONOate was confirmed based on measurement of some biological markers in bronchoalveolar lavage fluid (BALF) of rats. Additionally, mechanism underling the absorption enhancement action of SPM-NONOate was explored by combinatorial administration of FD4 and SPM-NONOate with various scavengers and generator to rat lungs. Results indicated that NO released from SPM-NONOate induced the enhancement in the drug absorption, and peroxynitrate, a NO metabolite, possibly participated in the absorption enhancing action of SPM-NONOate.

Strategies to Enhance Drug Absorption via Nasal and Pulmonary Routes

New therapeutic agents such as proteins, peptides, and nucleic acid-based agents are being developed every year, making it vital to find a non-invasive route such as nasal or pulmonary for their administration. However, a major concern for some of these newly developed therapeutic agents is their poor absorption. Therefore, absorption enhancers have been investigated to address this major administration problem. This paper describes the basic concepts of transmucosal administration of drugs, and in particular the use of the pulmonary or nasal routes for administration of drugs with poor absorption. Strategies for the exploitation of absorption enhancers for the improvement of pulmonary or nasal administration are discussed, including use of surfactants, cyclodextrins, protease inhibitors, and tight junction modulators, as well as application of carriers such as liposomes and nanoparticles.

The Effect of Absorption-Enhancement and the Mechanism of the PAMAM Dendrimer on Poorly Absorbable Drugs

The polyamidoamine (PAMAM) dendrimer is a highly efficient absorption promoter. In the present study, we studied the absorption-enhancing effects and the mechanism of PAMAM dendrimers with generation 0 to generation 3 (G0–G3) and concentrations (0.1–1.0%) on the pulmonary absorption of macromolecules. The absorption-enhancing mechanisms were elucidated by microarray, western blotting analysis, and PCR. Fluorescein isothiocyanate-labeled dextrans (FDs) with various molecular weights were used as model drugs of poorly absorbable drugs. The absorption-enhancing effects of PAMAM dendrimers on the pulmonary absorption of FDs were in a generation- and concentration-dependent manner. The G3 PAMAM dendrimer with high effectiveness was considered to the best absorption enhancer for improving the pulmonary absorption of FDs. G3 PAMAM dendrimers at three different concentrations were non-toxic to Calu-3 cells. Based on the consideration between efficacy and cost, the 0.1% G3 PAMAM dendrimer was selected for subsequent studies. The results showed that treatment with a 0.1% G3 PAMAM dendrimer could increase the secretion of organic cation transporters (OCTs), OCT1, OCT2, and OCT3, which might be related to the absorption-enhancing mechanisms of the pulmonary absorption of FDs. These findings suggested that PAMAM dendrimers might be potentially safe absorption enhancers for improving absorption of FDs by increasing the secretion of OCT1, OCT2, and OCT3.

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.

Pulmonary liposomal formulations encapsulated procaterol hydrochloride by a remote loading method achieve sustained release and extended pharmacological effects

Drug inhalation provides localized drug therapy for respiratory diseases. However, the therapeutic efficacy of inhaled drugs is limited by rapid clearance from the lungs. Small hydrophilic compounds have short half-lives to systemic absorption. We developed a liposomal formulation as a sustained-release strategy for pulmonary delivery of procaterol hydrochloride (PRO), a short-acting pulmonary β2-agonist for asthma treatment. After PRO-loaded liposomes were prepared using a pH gradient (remote loading) method, 100-nm liposomes improved residence times of PRO in the lungs. PRO encapsulation efficiency and release profiles were examined by screening several liposomal formulations of lipid, cholesterol, and inner phase. Although PRO loading was not achieved using the conventional hydration method, PRO encapsulation efficiency was >60% using the pH gradient method. PRO release from liposomes was sustained for several hours depending on liposomal composition. The liposomal formulation effects on the PRO behavior in rat lungs were evaluated following pulmonary administration in vivo. Sustained PRO release was achieved using simplified egg phosphatidylcholine (EPC)/cholesterol (8/1) liposome in vitro, and greater PRO remnants were observed in rat lungs following pulmonary administration. Extended pharmacological PRO effects were observed for 120min in a histamine-induced bronchoconstriction guinea pig model. We indicated the simplified EPC/cholesterol liposome potential as a controlled-release PRO carrier for pulmonary administration.

Improvement of pulmonary absorptions of poorly absorbable drugs using Gelucire 44/14 as an absorption enhancer

Objectives

This study aims to evaluate the absorption-enhancing effects of Gelucire 44/14 on the pulmonary absorption of different poorly absorbable drugs and relative mechanism of action.

Methods

Absorption-enhancing effect of Gelucire 44/14 were examined by an in-vivo pulmonary absorption experiment in rats, and the membrane toxicity of Gelucire 44/14 was evaluated by measuring levels of protein and dehydrogenase (LDH) in the bronchoalveolar lavage fluid (BALF) and morphological observation.

Key findings

Pulmonary absorptions of fluorescein isothiocyanate-dextrans, insulin and calcitonin were enhanced by Gelucire 44/14 (0.1–2.0%, w/v) in a concentration-dependent manner, and the maximal absorption-enhancing effect was obtained when the concentration of Gelucire 44/14 increased to 2.0% (w/v). Furthermore, Gelucire 44/14 neither increase the levels of protein and LDH in BALF nor change morphology of lung compared with control group. In addition, a well correlation between the absorption-enhancing effect and surface tension of insulin solution in the presence of Gelucire 44/14 was observed, suggesting Gelucire 44/14-mediated decrease in the surface tension of the gas-liquid interface in alveolar tissue was possible one of the improving mechanisms of Gelucire 44/14.

Conclusion

Gelucire 44/14 was a potential and safe absorption enhancer for improving the absorption of poorly absorbable drugs including insulin and calcitonin by pulmonary delivery.

Emerging micro- and nanotechnology based synthetic approaches for insulin delivery

Insulin is essential for type 1 and advanced type 2 diabetics to maintain blood glucose levels and prolong lives. The traditional administration requires frequent subcutaneous insulin injections that are associated with poor patient compliance, including pain, local tissue necrosis, infection, and nerve damage. Taking advantage of emerging micro- and nanotechnologies, numerous alternative strategies integrated with chemical approaches for insulin delivery have been investigated. This review outlines recent developments in the controlled delivery of insulin, including oral, nasal, pulmonary, transdermal, subcutaneous and closed-loop insulin delivery. Perspectives from new materials, formulations and devices at the micro- or nano-scales are specifically surveyed. Advantages and limitations of current delivery methods, as well as future opportunities and challenges are also discussed.

Formulation and in vivo evaluation of sodium alendronate spray-dried microparticles intended for lung delivery

Spray-dried powders for lung delivery of sodium alendronate (SA) were prepared from hydroalcoholic solutions. Formulations display geometric particle size below to 12 μm and spherical shape associated to a hollow structure. The addition of leucine and ammonium bicarbonate leads to porous particles with rough surfaces. The tapped density ranges from 0.016 to 0.062 g/cm(3), decreasing with the increase of the leucine concentration. For all formulations, the calculated aerodynamic diameters are lower than 5 μm. The in vitro aerodynamic evaluation shows that all powders present a high emitted fraction of 100%, a fine particle fraction ranging from 34.4% to 62.0% and an alveolar fraction ranging from to 23.7% to 42.6%. An optimized sample was evaluated regarding sodium alendronate acute pulmonary toxicity and lung bioavailability. The bronchoalveolar lavage study shows that the intratracheal administration of sodium alendronate dry powder and sodium alendronate aqueous solution do not induce significant increases of lung toxicity indicators as compared with the positive control. Moreover, the intratracheal administration of sodium alendronate dry powder results in a 6.23 ± 0.83% bioavailability, a 3.5-fold increase as compared to oral bioavailability. Finally, these results suggest that sodium alendronate pulmonary delivery could be a new and promising administration route.

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.

A mucoadhesive nanoparticulate system for the simultaneous delivery of macromolecules and permeation enhancers to the intestinal mucosa

The feasibility of combining safe permeation enhancers in a mucoadhesive particulate system for the oral delivery of peptide drugs was investigated in this study. Polyelectrolyte complex nanoparticles (NPs) were prepared by ionic interaction of spermine (SPM) with polyacrylic acid (PAA) polymer. Cytotoxicity studies in Caco-2 monolayers revealed the safety of the delivery system in the concentration range used for permeation enhancement. The cellular transport of fluorescein isothiocyanate dextran (FD4) showed higher permeation enhancing profiles of SPM-PAA NPs, as compared to SPM solution or PAA NPs prepared by ionic gelation with MgCl(2) (Mg-PAA NPs). These permeation enhancing effects were associated with a reversible decrease in TEER values, suggesting a paracellular permeation pathway by reversible opening of the tight junctions. Furthermore, confocal microscopy results revealed strong association of the NPs prepared using fluorescence labeled PAA to Caco-2 cells. The permeation enhancing properties of SPM-PAA NPs were further evaluated in vivo after oral administration to rats, using FD4 and calcitonin as models of poorly permeating drugs. Confocal microscopy images of rats' small intestine confirmed previous findings in Caco-2 cells and revealed a strong and prolonged penetration of FD4 from the mucosal to the basolateral side of the intestinal wall. In addition, the proposed NPs were efficient in improving the oral absorption of calcitonin, as evidenced by the significant and prolonged reduction of the blood calcemia in rats.