Relative Pharmacological Bioavailability Research Articles

A nano-delivery system based on preventing degradation and promoting absorption to improve the oral bioavailability of insulin

Oral insulin delivery can improve patient compliance and simulate the portal-peripheral insulin concentration gradient produced by endogenous insulin, so oral insulin delivery has a broad prospect. However, some characteristics of the gastrointestinal tract, lead to low oral bioavailability. Therefore, a “ternary mutual-assist” nano-delivery system based on poly(lactide-co-glycolide) (PLGA) as the backbone combined with ionic liquids (IL) and vitamin B12-chitosan (VB12-CS) was constructed in this study, the protein protection performance of IL improves the room temperature stability of the loaded insulin during nanocarrier preparation, transportation and storage to a certain extent, and the protein protection function of IL combined with the slow degradation property of PLGA and the pH-responsive function of VB12-CS to prevent the degradation of insulin in the gastrointestinal tract. In addition, the mucosal adhesion function of VB12-CS, VB12 receptor- and clathrin-mediated transcellular transport involving VB12-CS and IL, and paracellular transport mediated by IL and CS can be combined to improve the intestinal epithelial transport efficiency of insulin, thus, the nanocarrier has stronger preventing degradation and promoting absorption effects. Pharmacodynamic studies showed that after oral administration of VB12-CS-PLGA@IL@INS NPs to diabetic mice, the blood glucose level decreased to about 13 mmol/L, below the critical point of 16.7 mmol/L, and the blood glucose reached a normal level, which was 0.4 times of the blood glucose value before administration, its relative pharmacological bioavailability was 31.8 %, higher than the general nanocarriers (10–20 %) and more beneficial to the clinical transformation of oral insulin.

Assessment of Exenatide loaded Biotinylated Trimethylated Chitosan/HP- 55 Nanoparticles.

Exenatide(EXE) is an anti-hyperglycemic agent approved for treating type 2 diabetes by the Food and Drug Administration(FDA). However, twice-daily injection of exenatide is inconvenient for most of the patients. In this study, biotinylated trimethylated chitosan(Bio-TMC) based nanoparticles were proposed to promote oral absorption of exenatide. Realizing the oral administration of exenatide is very important to alleviate patient suffering and improve patient compliance. Bio-TMC was synthesized, and the chemical structure was characterized by Fourier transform infrared (FT-IR) spectroscopy and 1H NMR spectroscopy. Nanoparticles were prepared through polyelectrolyte interaction in the presence of sodium Tripolyphosphate (TPP) and hydroxypropyl methylcellulose phthalate (HP-55). Formulations were physically and chemically characterized. In vitro release was investigated in different pH media. In vivo antidiabetic activities of biotin modified and non-biotin modified chitosan were evaluated in db/db mice. EXE-loaded Bio-TMC/HP-55 nanoparticles were spherical in shape with a mean diameter of 156.2 nm and zeta potential of +11.3 mV. The drug loading efficiency and loading content were 52.38% and 2.08%, respectively. In vitro release revealed that EXE-loaded Bio-TMC/HP-55 nanoparticles were released faster in pH 1.2 than pH 6.8 (63.71% VS 50.12%), indicating that nanoparticles have enteric characteristics. Antidiabetic activity study revealed that after oral administration to diabetic mice, the relative pharmacological bioavailability (FPharm%) of the biotin modified nanoparticles was found to be 1.27-fold higher compared to the unmodified ones, and the hypoglycemic effect was also found to be better. Bio-TMC/HP-55 nanoparticles are feasible as oral drug carriers of exenatide and have the potential to be extended to other drugs that are not readily oral, such as monoclonal antibodies, vaccines, genes, etc. These would be beneficial to the pharmaceutical industry. Further research will focus on the biodistribution of Bio-TMC/HP-55 nanoparticles after oral administration.

Optimization of phytic acid-crosslinked chitosan microspheres for oral insulin delivery using response surface methodology.

Although oral administration is favorable mode of insulin delivery, it is the most challenging route, owing to poor oral bioavailability. In this study, a chitosan (CS)-based insulin delivery system was developed by ionic crosslinking with phytic acid (PA). CS-PA microspheres were optimized with different crosslinking conditions of CS and PA using response surface methodology to retain insulin during preparation and gastric digestion. Furthermore, the in vitro release profile, morphological structure, cytotoxicity, and intestinal permeability of the optimized microspheres, and its hypoglycemic effect in diabetic rats were evaluated. Under optimal conditions, the entrapment efficiency was 97.1%, and 67.0% of insulin was retained in the microspheres after 2h of gastric digestion followed by a sustained-release in intestinal fluid. Insulin was primarily distributed in the microsphere core with a monodisperse diameter of 663.3μm. The microspheres increased the permeability of insulin across Caco-2/HT-29 monolayers by 1.6 times with negligible cytotoxicity. The microspheres had a relative pharmacological bioavailability of 10.6% and significantly reduced blood glucose levels with a long-lasting hypoglycemic effect after oral administration in diabetic rats. This study demonstrated that an optimized formulation of a simple ionic crosslinking system using CS and PA could facilitate efficient oral delivery of insulin.

Cell-penetrating peptide enhanced insulin buccal absorption.

Non-injectable delivery of peptides and proteins is not feasible due to the limitations of large molecular mass, high hydrophilic properties, and gastrointestinal degradation. Therefore, proposing a new method to solve this problem is a burning issue. The objective of this study was to propose a novel protein delivery strategy to overcome the poor efficacy and irritation of buccal insulin delivery. In this study, we applied a conjugate of cell-penetrating peptides (LMWP) and insulin (INS-PEG-LMWP) for buccal delivery. INS-PEG-LMWP was prepared using insulin solution and mixture as references. The transport behaviour, in vivo bioactivity, hypoglycaemic effect, and safety of INS-PEG-LMWP were systematically characterised. An in vitro study demonstrated that the uptake and transportation of INS-PEG-LMWP across buccal mucosal multilayers significantly increased. By comparing the effects of different endocytic inhibitors on INS-PEG-LMWP uptake, the conjugate might be delivered via an energy independent, electrostatically adsorbed pathway. INS-PEG-LMWP's relative pharmacological bioavailability was high and its relative bioavailability was up to 26.86%, demonstrating no visible mucosal irritation. Cell-penetrating peptides are likely to become a reliable and safe tool for overcoming insulin's low permeability through the epithelial multilayers, the major barrier to buccal delivery.

β-cyclodextrin- soy soluble polysaccharide based core-shell bionanocomposites hydrogel for vitamin E swelling controlled delivery

Hydrogel nanocomposites (HGNCs), with a hydrophobic inner hollows structure and a hydrophilic exterior, is often used to encapsulate the broadest range of guest molecules. Herein, we established a three-dimensional, nanocomposites, superabsorbent, malleable, and bioadhesive HGNCs via chemical crosslinker poly (ethylene glycol) diglycidyl ether (PEGDGE) to enhance the controlled release and bioavailability of Vitamin E (VE). β-cyclodextrin (β-CD) are integrated as multi-core units in the soy soluble polysaccharide (SSPS) polymer network in which the β-CD cavities act as carriers for (VE) by host-guest interaction. We have examined the detailed structures and morphology by FTIR, DSC, XRD, SEM, TEM, AFM, and CLSM. Overall, increasing the β-CD than SSPS in the reaction mixture (from 10 to 25%) led to enhance the crosslinking degree, improve the elastic behavior (G′>G″), increase the particle size (from 114.2 to 202.9 nm), and the hardness. Besides, decreasing the adhesiveness, pore size, and swelling. Our (HGNCs) did not rupture under compression up to 90% strain with (1.8 MPa) strength. The nanocomposites (1:1) exhibited less nanosized after pectinase and α-amylase hydrolysis (75 and 124 nm, respectively). Also, the (HGNCs) exhibited outstanding swelling-adsorption and sustained release (over 230 h) towards VE in vitro. It showed high encapsulation efficiency and loading capacity (79.10 and 16.04%, respectively). Additionally, the oral administration of VE-loaded HGNCs in rats resulted in a sustained increase of plasma VE levels over 12 h post-administration. The relative pharmacological bioavailability of VE was larger for VE-loaded HGNCs (reached to 7.5-fold increase) compared to free VE suspension. Keywords: Nanohydrogel; β-cyclodextrin; Soy soluble polysaccharide; Vitamin E; swelling; control release.

Design of Virus-Mimicking Polyelectrolyte Complexes for Enhanced Oral Insulin Delivery

The viscous and elastic mucus layer is still an undesirable barrier for oral insulin delivery. To solve the problem, virus-mimicking nanosized polyelectrolyte complex (PEC) was designed and their capacity in enhancing peroral insulin absorption in combination with bifunctional material sodium dodecyl sulfate (SDS) coating was investigated. Inspired by nature, virus-mimicking chitosan (CS)-modified L-Phe derivatives were synthesized to simulate the components of viral envelopes and then PECs between CS-g-N-Phe copolymers and insulin were prepared to achieve both structure and composition simulation of virus envelope. Based on the results from both in vitro and in vivo studies, it was concluded that in vitro mucodiffusion and in vivo hypoglycemic effect were dependent on L-Phe graft ratio, with CS-g-N-Phe20.2%/insulin PECs presenting 2.0- to 2.2-fold higher relative pharmacological bioavailability than nonmodified CS/insulin PECs. Thereafter, SDS solution was applied as outer layer coating on the surface of virus-mimicking PECs. The coated PECs showed improved enzymatic stability, enhanced transport across mucus layer as well as intestinal epithelium in an SDS concentration–dependent manner, with 0.6% SDS coating presenting the best effect, with further enhanced relative pharmacological bioavailability in healthy rats and prolonged therapeutic effect up to 9 h.

Enhanced hypoglycemic effect of biotin-modified liposomes loading insulin: effect of formulation variables, intracellular trafficking, and cytotoxicity.

Peroral protein/peptide delivery has been one of the most challenging, but encouraging topics in pharmaceutics. This article was intended to explore the potential of biotin-modified liposomes (BLPs) as oral insulin delivery carriers. By incorporating biotin-DSPE into the lipid bilayer, we prepared BLPs using reverse evaporation/sonication method. We investigated hypoglycemic effects in normal rats after oral administration of BLPs, and the possible absorption mechanism by a series of in vitro tests. The relative pharmacological bioavailability of BLPs was up to 11.04% that was as much as 5.28 folds of conventional liposomes (CLPs). The results showed that the enhanced oral absorption of insulin mainly attributed to biotin ligand-mediated endocytosis. The results provided proof of BLPs as effective carriers for oral 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.

Nanoemulsions coated with alginate/chitosan as oral insulin delivery systems: preparation, characterization, and hypoglycemic effect in rats

This study aimed to prepare nanoemulsions coated with alginate/chitosan for oral insulin delivery. Uncoated nanoemulsions were prepared by homogenization of a water in oil in water (w/o/w) multiple emulsion that was composed of Labrafac® CC, phospholipid, Span™ 80 and Cremorphor® EL. Coating of the nanoemulsions was achieved based on polyelectrolyte cross-linking, with sequential addition of calcium chloride and chitosan to the bulk nanoemulsion dispersion that contained alginate. The particle size of the coated nanoemulsions was about 488 nm and the insulin entrapment ratio was 47.3%. Circular dichroism spectroscopy proved conformational stability of insulin against the preparative stress. In vitro leakage study indicated well-preserved integrity of the nanoemulsions in simulated gastric juices. Hypoglycemic effects were observed in both normal and diabetic rats. The relative pharmacological bioavailability of the coated nanoemulsion with 25 and 50 IU/kg insulin were 8.42% and 5.72% in normal rats and 8.19% and 7.84% in diabetic rats, respectively. Moreover, there were significantly prolonged hypoglycemic effects after oral administration of the coated nanoemulsions compared with subcutaneous (sc) insulin. In conclusion, the nanoemulsion coated with alginate/chitosan was a potential delivery system for oral delivery of polypeptides and proteins.

Biodegradable Solid Lipid Nanoparticle Flocculates for Pulmonary Delivery of Insulin

The aim of our study was to prepare and characterize biodegradable insulin-loaded solid lipid nanoparticles (Ins-SLNs) flocculates for the pulmonary delivery of Ins. The cationic Ins-SLNs and anionic Ins-SLNs were prepared by W/O/W emulsion technique, respectively. Then anionic Ins-SLNs were self-assembled into flocculates via electrostatic interactions with the oppositely surface charged cationic Ins-SLNs followed by lyophilized into dry powders. The maximal entrapment efficiency of cationic Ins-SLNs and anionic Ins-SLNs were 56.32 +/- 1.01% and 66.02 +/- 1.58%, respectively. Freeze-drying the Ins-SLNs flocculates yielded dry powders with desirable aerodynamic diameter of 2.04 +/- 0.17 microm and low bulk density of 0.06146 +/- 0.0045 g/cm3, suitable for inhalation. In addition, the flocculates showed high aerosolization efficiency (emitted fraction of 92.54 +/- 0.77% and respirable fraction of 66.89 +/- 3.02%). The in vivo study showed that Ins-SLNs flocculates could prolong hypoglycemic effect and a relative pharmacological bioavailability of 35.62 +/- 1.34% could be achieved after intratracheal instillation to diabetic rats at the dose of 8 IU/kg dosage. Therefore, the biodegradable SLN flocculates fabricated via charge interaction may provide a useful strategy to fabricate dry powder for pulmonary administration of protein therapeutics or antigens.

Experiment on the feasibility of using modified gelatin nanoparticles as insulin pulmonary administration system for diabetes therapy

Polymeric nanoparticles are widely used as targeted carriers for biomacromolecules. In this paper, modified gelatin nanoparticles were prepared and their feasibility as insulin pulmonary administration system was investigated. D: ,L: -glyceraldehyde and poloxamer 188 were used for gelatin nanoparticle preparation. Novel water-in-water emulsion technique was used to prepare insulin-loaded nanoparticles. Morphological examination of insulin-loaded nanoparticles was carried out using scanning electron microscopy (SEM). Intratracheal instillation of insulin-loaded nanoparticles was performed to evaluate animal hypoglycemic effect. With fluorescence labeling of insulin, alveolar deposition and absorption of insulin-loaded nanoparticles were investigated. Histological changes in the lung were also observed to evaluate the safety. From the micromorphology observation, insulin-loaded nanoparticles under gelatin-poloxamer 188 ratio at 1:1 showed smooth and uniform surface, with average particle size 250 nm and Zeta potential -21.1 mV. From animal experiment, insulin-loaded nanoparticles under gelatin-poloxamer 188 ratio at 1:1 promoted insulin pulmonary absorption effectively and showed good relative pharmacological bioavailability. Proved by alveolar deposition result, FITC-insulin-loaded nanoparticle group was characterized by an acute and rapid hypoglycemic effect. In addition, nanoparticles could guarantee the safety of lung by reducing insulin deposition in lung. A transient weak inflammatory response was observed at 1 day after administration. With good physical characterization, high bioavailability, fast and stable hypoglycemic effect, insulin-loaded nanoparticles might be developed as a novel insulin pulmonary system for diabetes therapy.

The preparation and application of pulmonary surfactant nanoparticles as absorption enhancers in insulin dry powder delivery

Aim: To study the preparation and application of pulmonary surfactant (PS) nanoparticles as absorption enhancers in insulin dry powder delivery. PS is a complex mixture of mainly phospholipids and proteins. The composition leads to a unique spreading effect of the surfactants as well as spontaneous nanoparticles formation, which may be favorable characteristics of pulmonary drug delivery systems. Method: In this article, insulin has been a model drug, as an important drug in lowering blood glucose and as a classic protein drug. PS was extracted from pig lungs and was observed as nanoparticles morphology in water by transmission electron microscopy after preparation. Inhalation dry powders were formulated by PS nanoparticles, insulin, and other excipients. In addition, blood glucose level of rats was determined when the insulin dry powder of PS group and control group was delivered by inhalation route. Result: Compared with control group, scanning electron microscopy showed that the dry powders of PS group possess similar particle size and smoother surface. The spray-dried powders re-suspended possessed similar nanoparticle appearance compared with the original PS suspension. Animal studies showed that blood glucose level was effectively reduced when the insulin dry powder of PS group was delivered by inhalation route. Compared with subcutaneous injection group (4 U/kg), the relative pharmacological bioavailability of the insulin dry powders of control group (14 U/kg) and PS group (14 U/kg) was 19.97% and 32.57%, respectively. Conclusion: PS nanoparticles, as absorption enhancers used in dry powder inhalation, could evidently enhance the effect of insulin in lowering blood glucose.

Biopharmaceutical characterisation of insulin and recombinant human growth hormone loaded lipid submicron particles produced by supercritical gas micro-atomisation

Homogeneous dispersions of insulin and recombinant human growth hormone (rh-GH) in tristearin/phosphatidylcholine/PEG mixtures (1.3:1.3:0.25:0.15 w/w ratio) were processed by supercritical carbon dioxide gas micro-atomisation to produce protein-loaded lipid particles. The process yielded spherical particles, with a 197 ± 94 nm mean diameter, and the insulin and rh-GH recovery in the final product was 57 ± 8% and 48 ± 5%, respectively. In vitro, the proteins were slowly released for about 70–80 h according to a diffusive mechanism. In vivo, the insulin and glucose profiles in plasma obtained by subcutaneous administration of a dose of particles containing 2 μg insulin to diabetic mice overlapped that obtained with 2 μg of insulin in solution. Administration of a dose of particles containing 5 μg insulin resulted in faster and longer glycaemia reduction. Oral administration of 20 and 50 μg insulin equivalent particles produced a significant hypoglycaemic effect. The glucose levels decreased since 2 h after administration, reaching about 50% and 70% glucose reduction in 1–2 h with the lower and higher dose, respectively. As compared to subcutaneous administration, the relative pharmacological bioavailability obtained with 20 and 50 μg equivalent insulin particles was 7.7% and 6.7%, respectively. Daily subcutaneous administration of 40 μg of rh-GH-loaded particles to hypophysectomised rats induced similar body weight increase as 40 μg rh-GH in solution. The daily oral administration of 400 μg rh-GH equivalent particles elicited a slight body weight increase, which corresponded to a relative pharmacological bioavailability of 3.4% compared to subcutaneous administration.

Solid Lipid Nanoparticles as Insulin Inhalation Carriers for Enhanced Pulmonary Delivery

Growing attentions have been paid to the pulmonary route for systemic delivery of peptide and protein drugs, such as insulin. Advantages of this non-injective route include rapid drug deposition in the target organ, fewer systemic side effects and avoiding first pass metabolism. However, sustained release formulations for pulmonary delivery have not been fully exploited till now. In our study, a novel dry powder inhalation (DPI) system of insulin loaded solid lipid nanoparticles (Ins-SLNs) was investigated for prolonged drug release, improved stability and effective inhalation. Firstly, the drug was incorporated into the lipid carriers for a maximum entrapment efficiency as high as 69.47 +/- 3.27% (n = 3). Secondly, DPI formulation was prepared by spray freeze drying of Ins-SLNs suspension, with optimized lyoprotectant and technique parameters in this procedure. The properties of DPI particles were characterized for their pulmonary delivery potency. Thirdly, the in vivo study of intratracheal instillation of Ins-SLNs to diabetic rats showed prolonged hypoglycemic effect and a relative pharmacological bioavailability of 44.40% could be achieved in the group of 8 IU/kg dosage. These results indicated that SLNs have shown increasing potential as an efficient and non-toxic lipophilic colloidal drug carrier for enhanced pulmonary delivery of insulin.

Spray-freeze-dried dry powder inhalation of insulin-loaded liposomes for enhanced pulmonary delivery

Nowadays, growing attention has been paid to the pulmonary region as a target for the delivery of peptide and protein drugs, especially macromolecules with systemic effect like insulin, since the pulmonary route exhibits numerous benefits to be an alternative for repeated injection. Furthermore, encapsulation of insulin into liposomal carriers is an attractive way to increase drug retention time and control the drug release in the lung; however, its long-term stability during storage in the reservoir and the process of aerosolization might be suspected when practically applied. Thus, the aim of this study was to design and characterize dry powder inhalation of insulin-loaded liposomes prepared by novel spray-freeze-drying method for enhanced pulmonary delivery. Process variables such as compressed air pressure, pump speed, and concentration were optimized for parameters such as mean particle diameter, moisture content, and fine particle fraction of the produced powders. Influence of different kinds and amounts of lyoprotectants was also evaluated for the best preservation of the drug entrapped in the liposome bilayers after the dehydration–rehydration cycle. The in vivo study of intratracheal instillation of insulin-loaded liposomes to diabetic rats showed successful hypoglycemic effect with low blood glucose level and long-lasting period and a relative pharmacological bioavailability as high as 38.38% in the group of 8 IU/kg dosage.

Niosomes with Sorbitan Monoester as a Carrier for Vaginal Delivery of Insulin: Studies in Rats

To prepare and investigate the potential of the niosomes vaginal delivery system for systemic treatment of insulin is the goal of this study. Two kinds of vesicles with Span 40 and Span 60 were prepared by lipid phase evaporation methods with sonication. The niosomal entrapment efficiency was determined by column chromatography. The particle size and morphology of the vesicles also were evaluated. The results showed optimized niosomes prepared in this study had niosomal entrapment efficiency 26.68 ± 1.41% for Span 40 and 28.82 ± 1.35% for Span 60, respectively. The particle sizes of Span 40 niosomes and Span 60 niosomes were 242.5 ± 20.5 nm and 259.7 ± 33.8 nm, respectively. There were no significant differences in appearance between the two types of vesicles. The hypoglycemic effects, and insulin concentrations after vaginal administration of insulin vesicles to rats were investigated. Compared with subcutaneous administration of insulin solution, the relative pharmacological bioavailability and the relative bioavailability of vaginal administration of insulin vesicles were determined. Compared with subcutaneous administration of insulin solution, the relative pharmacological bioavailability and the relative bioavailability of insulin-Span 60 vesicles group were 8.43% and 9.61%, and insulin-Span 40 niosomes were 9.11% and 10.03% (p > 0.05). Span 60 and Span 40 niosomes were both higher than blank Span 40, Span 60 vesicles, and free insulin physical mixture groups (p < 0.05). The results indicates insulin-Span 60, Span 40 niosomes had an enhancing effect on vaginal delivery of insulin. Although the factors controlling the process for penetration of a portion of vaginally administrated niosomes into bloodstream from vaginal tract is still not fully understood, our results demonstrated that after encapsulation in niosomes of definite type, insulin became an active and efficiently therapeutic agent when administrated vaginally and might be a good carrier for vaginal delivery of protein drugs.

Oral Delivery of Mono-PEGylated sCT (Lys18) in Rats: Regional Difference in Stability and Hypocalcemic Effect

In the in vitro experiment using a luminal, mucosal, and fecal fluid/extract from jejunum and colon of a rat, Lys18-residue modified mono-PEG2k-sCT (Lys18-PEG2K-sCT) exhibited a longer half-life than salmon calcitonin (sCT) in a colonic fluid and its extract. A physical adsorption study showed that Lys18-PEG2K-sCT had lower adsorption in the feces than sCT over an 8-hr period. An absorption study of the sCT and Lys18-PEG2K-sCT from the jejunum and colon using an in situ closed-loop technique in anesthetized rats showed a dose-dependent reduction in the plasma Ca2 + level but to a certain limit. Furthermore, the hypocalcemic response by intracolonic administration was significantly higher than the intrajejunal one, demonstrating that the colon had better absorption. In particular, Lys18-PEG2K-sCT (5 µg/rats) produced the most pronounced hypocalcemia after the intracolonic administration, which resulted in a sustained reduction in the serum calcium level over an 8-hr period, with a maximum reduction (% maxd) of 38% after 4 hr. The overall reduction in the serum calcium levels, which was expressed as the net change in the AUC relative to the control over an 8-hr period, was 25.51 ± 3.38 for Lys18-PEG2K-sCT. The relative pharmacological bioavailability of the intracolonically administered Lys18-PEG2K-sCT was 2.1-fold higher than sCT and the absolute pharmacological bioavailability was 73.59% of IV-injected sCT in an 8-hr period. Overall, this study highlights the feasibility of the oral delivery of Lys18-PEG2K-sCT in achieving a sustained calcium-lowering effect.

Nasal insulin delivery in the chitosan solution: in vitro and in vivo studies

The effects of chitosan concentrations, osmolarity, medium and absorption enhancers in the chitosan solution on nasal insulin delivery were studied in vitro and in vivo. The penetration of insulin through the mucosa of rabbit nasal septum was investigated by measuring the transmucosal flux in vitro, while the nasal absorption of insulin in vivo was assessed by the efficiency in lowering the blood glucose levels in normal rats. It was demonstrated that increasing concentrations of chitosan up to 1.5% (w/v) caused an increase in the permeability of insulin across the nasal mucosa. Insulin given intranasally in hypo- or hyperosmotic formulation showed a higher hypoglycemic effect than insulin delivered in isoosmotic formulation. Insulin formulation in chitosan solution prepared with deionized water brought to a higher relative pharmacological bioavailability (Fr) value than that prepared with 50 mM pH 7.4 phosphate buffer. A formulation containing both 1% chitosan and 0.1% ethylenediaminetetraacetic acid (EDTA), 5% polysorbate 80 (Tween 80) or 1.2% β-cyclodextrin (β-CD) did not lead to a higher Fr than insulin formulated with 1% chitosan alone. The formulation containing both 5% hydroxypropyl-β-cyclodextrin (HP-β-CD) and 1% chitosan was more effective at reducing blood glucose levels than the formulation containing 5% HP-β-CD or 1% chitosan alone. The studies indicated that chitosan concentrations, osmolarity, medium and absorption enhancers in chitosan solution have significant effect on the insulin nasal delivery. The results of in vitro experiments were in good agreement with that of in vivo studies.

Revisión de la enfermedad por embolismo de cristales de colesterol

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 7 days 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.

Bioadhesive polysaccharide in protein delivery system: chitosan nanoparticles improve the intestinal absorption of insulin in vivo

There are many ongoing investigations to improve the oral bioavailability of peptide and protein formulations. Bioadhesive polysaccharide chitosan nanoparticles (CS-NPs) would seem to further enhance intestinal absorption of them. In this study, Insulin-loaded CS-NPs were prepared by ionotropic gelation of CS with tripolyphosphate anions. Its particle size distribution and zeta potential were determined by photon correction spectroscopy and laser Dopper anemometry. The ability of CS-NPs to enhance intestinal absorption of insulin and increase the relative pharmacological bioavailability of insulin was investigated by monitoring the plasma glucose level of alloxan-induced diabetic rats after oral administration of various doses of insulin-loaded CS-NPs. CS-NPs had a particle size in the range of 250–400 nm and its polydispersity index was smaller than 0.1, positively charged, stable. Insulin association was found up to 80% and its in vitro release showed a great initial burst with a pH-sensitivity property. CS-NPs enhanced the intestinal absorption of insulin to a greater extent than the aqueous solution of CS in vivo. Above all, after administration of 21 I.U./kg insulin in the CS-NPs, the hypoglycemia was prolonged over 15 h and the average pharmacological bioavailability relative to SC injection of insulin solution was up to 14.9%.