Chitosan as a nasal delivery system: evaluation of insulin absorption enhancement and effect on nasal membrane integrity using rat models

In vitro and in vivo evaluations on nanoparticle and phospholipid hybrid nanoparticles with absorption enhancers for oral insulin delivery

Oral delivery of peptide and proteins is challenging due to their poor physical and chemical stability which usually results in inadequate therapeutic efficacy. Nanoparticles encapsulating insulin was developed by the ionic gelation technique using sulfobutyl ether-β-cyclodextrin as an anionic linker. Phospholipid hybrid nanoparticles were formulated by utilizing ionic gelation and thin-film hydration methods using D-α-Tocopheryl polyethylene glycol 1000 succinate, sodium deoxycholate separately and in combination to take the advantage of liposomes and nanoparticles also various absorption enhancement mechanisms. All formulations were characterized and tested for in vitro gastrointestinal stability, in vitro drug release, and cytotoxicity. On the other hand, in vivo effects of developed formulations on reducing blood glucose levels were monitored for 8 hours. Phospholipid hybrid nanoparticles including D-α-Tocopheryl polyethylene glycol 1000 succinate and sodium deoxycholate in combination with 548.7 nm particle size, 0.332 polydispersity index, 22.0 mV zeta potential, and 61.9% encapsulation efficiency, exhibited desired gastrointestinal stability and insulin release in vitro. In addition, the formulation proved its safety with cytotoxicity studies on L929 cells. The subjected phospholipid hybrid nanoparticle formulation was found to be the most effective formulation by reducing and maintaining blood glucose levels with avoiding fluctuations.

Chronological Delivery of Antihypertensive Drugs in Bilayered Core-in-Cup Buccoadhesive Tablets: In Vitro and In Vivo Evaluation

Hypertension shows circadian blood pressure rhythms (day-night pattern) that urge the delivery of antihypertensive drugs at the right time in the desired levels. Thus, a bilayered core-in-cup buccoadhesive tablet was formulated that immediately releases olmesartan, to give a burst effect, and controls azelnidipine release, to prolong its therapeutic effect. The main challenge was the poor bioavailability of azelnidipine due to its poor aqueous solubility and first-pass effect. Hence, liquisolid compact buccoadhesive tablets were prepared to enhance solubility, dissolution profiles, and bypass the oral route. Two factorial designs were conducted to study the type and concentration effect of the mucoadhesive polymers on the dissolution and mucoadhesion of olmesartan and azelnidipine. Characterization studies were conducted regarding drug content, surface pH, water uptake, mucoadhesive strength, in vitro release, and ex vivo permeability. The core-in-cup olmesartan/azelnidipine buccoadhesive tablet showed similar release profile to the statistically optimized formulae of each drug. In vitro dissolution study showed enhanced release of azelnidipine than the directly compressed tablets, to comply with the regulatory standards of controlled release systems. In vivo pharmacokinetic study of olmesartan and azelnidipine conducted on human volunteers against Rezaltas® 10/8 mg tablet showed percentage relative bioavailability of 106.12 and 470.82%, respectively. Graphical Abstract.

Improving the hypoglycemic effect of insulin via the nasal administration of deep eutectic solvents

This study aimed to develop biocompatible deep eutectic solvents (DESs) as carriers for improving the nasal delivery of insulin. The DES was prepared from malic acid and choline chloride broadly used in foods, drugs, or cosmetics as biocompatible additives. The DES of choline chloride and malic acid (CM-DES) demonstrated lower melting point (-59.1 °C) and higher viscosity (120,000 cP) compared with hydrogels based on sodium carboxyl methyl cellulose (CMC-Na). The conformational structure of insulin does not change in CM-DES as characterized by circular dichroism. The in vitro results showed that CM-DES dissociated gradually but did not disintegrate immediately upon contact with water. CM-DES was able to improve the hypoglycemic effect of insulin significantly at different doses compared with hydrogels or solutions of insulin, which could be ascribed to facilitated penetration of insulin across the nasal epithelia by CM-DES. The hypoglycemic effect of CM-DES loading insulin at a dose of 25 IU/kg was similar to that of subcutaneous insulin at 1 IU/kg. In addition, no evident toxicity to nasal epithelia was observed after nasal administration to rats for seven consecutive days. In conclusion, CM-DES showed promising potential in enhancing the hypoglycemic effect of insulin via the nasal route.

Preparation and characterization of microencapsulated DwPT trivalent vaccine using water soluble chitosan and its in-vitro and in-vivo immunological properties

The paper explained the microencapsulation of three different antigenic materials viz. Diphtheria toxoid (DT), whole cell pertussis antigens (PT and FHA) and tetanus toxoid (TT) by coacervation method using water soluble chitosan as a polymer crosslinked by vanillin/TPP co-crosslinkers for the development of oral trivalent DwPT vaccine. Instrumental characterization of chitosan microspheres suggested specific interaction with vanillin/TPP, higher thermal stability, amorphous nature, spherical morphology with size less than 2μm along with positive charge density offering mucoadhesive properties. Furthermore, PT and FHA showed higher encapsulation up to 94% followed by TT and DT. Cumulative release rate of DT was (68.47%), TT (73.67%), PT (43%) and FHA (53%). Release kinetics interpreted using DD solver program, indicated protein release followed first order kinetics and obeyed Korsmeyer-peppas model, stating fickian diffusion relates to diffusion, erosion and controlled release rate of the encapsulated toxoids. Application of formulations on caco-2 cell line showed negligible cytotoxic effect and efficient uptake of FITC labelled microspheres. The obtained in-vivo results suggests that the final trivalent DwPT formulation were having successful elicitation of both systemic (IgG) and mucosal (sIgA) immune response in balb/c mice. Overall studies indicated that DwPT formulation could be a suitable alternative to available injectable DaPT vaccine.

Spray Dried Chitosan Microparticles for Intravesical Delivery of Celecoxib: Preparation and Characterization

PURPOSE

Chitosan microparticles containing celecoxib (CB), were developed as chemoprevention of bladder cancer. Furthermore two inclusion complexes of CB with methyl-β-cyclodextrin (C1 and C2) were prepared to improve the solubility of the drug.

METHODS

C1 and C2 were obtained by freeze-drying and characterized in the solid state and in solution. Microparticles loaded with CB or C1 or C2 were prepared by spray drying and fully characterized.

RESULTS

The yield and encapsulation efficiencies of microparticles depended by both the viscosity and the presence of the inclusion complex in the feed medium nebulised. Generally, the microparticles exhibited a spherical shape with mean diameter of approximately 2 μm which was compatible with local intravesical administration using a catheter. The CB release studies from the microparticles allowed us to identify both immediate release systems (microparticles including the complexes) and prolonged release systems (microparticles including CB alone). The latter exhibited good adhesion to the bladder mucosa, as highlighted by a mucoadhesion study. Histological studies revealed a desquamation of the superficial cells when the bladder mucosa was treated with microparticles loaded with CB, while the morphology of the urothelium did not change when it was treated with microparticles loaded with the inclusion complex.

CONCLUSION

A new CB intravesical formulation than can easily be administered with a catheter and is able to release the drug at the target site for several hours was realized. This new delivery system could be a good alternative to classic oral CB administration.

Optimization, characterization and evaluation of chitosan-tailored cubic nanoparticles of clotrimazole

The present study deals with improvement of the mucoadhesive properties of monoolein based cubic nanoparticles by incorporating chitosan. Chitosan-tailored cubic nanoparticles were prepared by thin film hydration followed by ultrasonication employing clotrimazole as model drug. The effect of Pluronic F127 fraction and concentration of chitosan on particle size and % mucin binding of the formulations was studied using 2-factor, 3-level, central composite experimental design. The concentration of chitosan was found to influence particle size and % mucin binding of cubic nanoparticles while Pluronic F127 fraction influenced only the % mucin binding. Studies indicated 8.33(%w/w) fraction of Pluronic F127 and 0.17 (%w/v) concentration of chitosan as optimum concentration. Finally, the optimized batch was characterized by polarized light microscopy, small-angle X-ray scattering (SAXS) and transmission electron microscopy. The results unveiled incorporation of chitosan did not disrupt the inner cubic structure of nanoparticles. Peak indexing of SAXS data revealed the coexistence of P-type and D-type cubic phases in nanoparticles. Further, comparative evaluation studies showed significantly higher anti-fungal activity of clotrimazole-loaded chitosan-tailored cubic nanoparticles than conventional suspension of clotrimazole against Candida albicans.

Chitosan tripolyphosphate (CS/TPP) nanoparticles: preparation, characterization and application for gene delivery in shrimp

The present study examines the use of CS/TPP nanoparticles for gene delivery in different tissues of shrimp through oral route. The viral gene of WSSV was used to construct DNA vaccines using pcDNA 3.1, a eukaryotic expression vector and the constructs were named as pVP28. The CS/TPP nanoparticles were synthesized by ionic gelation process and these particles were characterized. The structure and morphology of the nanoparticles were studied by field emission scanning electron microscopy (FE-SEM) and FTIR (Fourier Transform Infrared Spectra). The cytotoxicity of CS/TPP nanoparticles was evaluated by MTT assay using fish cell line. The expression of gene was confirmed by Immuno-dot blot, ELISA and RT-PCR analyses. The results indicate that DNA can be easily delivered into shrimp by feeding with CS/TPP nanoparticles.

Rheological investigation and its correlation with permeability coefficient of drug loaded carbopol gel: influence of absorption enhancers

CONTEXT

The present study was planned to investigate the effect of absorption enhancers on the microstructure of Losartan potassium gel and hence its influence on the diffusion of Losartan potassium across nasal mucosa.

METHOD

Losartan potassium loaded carbopol gel (1% w/v) with and without absorption enhancers was prepared. Polyethylene glycol (PEG) 4000 and ethanol were used as absorption enhancers. Microstructural elucidation of prepared gels was done using shear rheology. Ex vivo drug release studies were performed on the prepared gels.

RESULTS

It was observed that the absorption enhancers PEG 4000 and ethanol altered the gel microstructure. The prepared gels were viscoelastic in nature suggesting their suitability for topical application. Permeability coefficient of Losartan potassium loaded into gels was found to be inversely proportional to the storage modulus. Thus increase in storage modulus lead to slow drug diffusion.

CONCLUSION

The current study emphasizes on the fact that selection of polymeric carrier for nasal drug delivery and/or absorption enhancer strongly influence the microstructure of the gel and hence the pharmaceutical performance of the formulation.

Gastroretentive microparticles for drug delivery applications

Many strategies have been proposed to explore the possibility of exploiting gastroretention for drug delivery. Such systems would be useful for local delivery, for drugs that are poorly soluble at higher pH or primarily absorbed from the proximal small intestine. Generally, the requirements of such strategies are that the vehicle maintains controlled drug release and exhibits prolonged residence time in the stomach. Despite widespread reporting of technologies, many have an inherent drawback of variability in transit times. Microparticulate systems, capable of distributing widely through the gastrointestinal tract, can potentially minimise this variation. While being retained in the stomach, the drug content is released slowly at a desired rate, resulting in reduced fluctuations in drug levels. This review summarises the promising role of microencapsulation in this field, exploring both floating and mucoadhesive microparticles and their application in the treatment of Helicobacter pylori, highlighting the clinical potential of eradication of this widespread infection.

Polysaccharide drug delivery systems based on pectin and chitosan

Chitosans and pectins are natural polysaccharides which show great potential in drug delivery systems. Chitosans are a family of strongly polycationic derivatives of poly-N-acetyl-D-glucosamine. This positive charge is very important in chitosan drug delivery systems as it plays a very important role in mucoadhesion (adhesion to the mucosal surface). Other chitosan based drug delivery systems involve complexation with ligands to form chitosan nanoparticles with can be used to encapsulate active compounds. Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions often described in simplified terms as the "smooth" and "hairy" regions respectively. Pectin HG regions consist of poly-glacturonic acid residues which can be partially methyl esterified. Pectins with a degree of methyl esterification (DM) > 50% are known as high methoxyl (HM) pectins and consequently low methoxyl (LM) pectins have a DM less than 50%. Low methoxyl pectins are of particular interest in drug delivery as they can form gels with calcium ion (Ca2+) which has potential applications especially in nasal formulations. In this chapter we will discuss the physicochemical properties of both chitosans and pectins and how these translate to current and potential drug delivery systems.

Chitosan nanoparticles: a promising system in novel drug delivery

The ability of nanoparticles to manipulate the molecules and their structures has revolutionized the conventional drug delivery system. The chitosan nanoparticles, because of their biodegradability, biocompatibility, better stability, low toxicity, simple and mild preparation methods, offer a valuable tool to novel drug delivery systems in the present scenario. Besides ionotropic gelation method, other methods such as microemulsion method, emulsification solvent diffusion method, polyelectrolyte complex method, emulsification cross-linking method, complex coacervation method and solvent evaporation method are also in use. The chitosan nanoparticles have also been reported to have key applications in parentral drug delivery, per-oral administration of drugs, in non-viral gene delivery, in vaccine delivery, in ocular drug delivery, in electrodeposition, in brain targeting drug delivery, in stability improvement, in mucosal drug delivery in controlled drug delivery of drugs, in tissue engineering and in the effective delivery of insulin. The present review describes origin and properties of chitosan and its nanoparticles along with the different methods of its preparation and the various areas of novel drug delivery where it has got its application.

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.

Some observations on the effects of bioprocessing on biopolymer stability

A short review is given of some of the effects of the stresses encountered during bioprocessing of protein and carbohydrate-based macromolecular systems. This is of relevance to the effectiveness and safety of protein or peptide drugs themselves (such as insulin and monoclonal antibodies) and for the integrity of delivery systems (such as various carbohydrate-based hydrogel or mucoadhesive polymers). Some carbohydrate polymers are themselves bioactive or immunostimulatory and particular use is being made of polysaccharide and glycoconjugate vaccines whose effectiveness can be severely effected by chain degradation. Stability criteria include molecular weight and conformation and techniques ranging from simple viscomery measurements to sophisticated analytical ultracentrifuge and multi-angle light scattering coupled to size exclusion chromatography and precision viscometry measurements have been useful in this regard. We focus on some recent work on the degradation and aggregation of immunoglobulin G4-based monoclonal antibodies in response to repeated freezing and thawing and long-term storage, looking at the possible connection between conformation change and aggregation, the effects of storage conditions on the stability of chitosan mucoadhesive systems used for nasal and oral delivery. We look at the effects of sterilization conditions (thermal and irradiation) on the stability of a variety of other polysaccharides such as starches, κ-carrageenan, carboxymethylcellulose, alginate, low- and high-methoxy pectins, guar, and xyloglucans and consider the use of a relatively new method for the evaluation of the molecular weight distribution of glycoconjugate vaccines with molecular weights as high as 100 × 10(6) g/mol.

Comparison of different absorption enhancers on the intranasal absorption of isosorbide dinitrate in rats

The objective of this work was to study the influence of different absorption enhancers on the intranasal absorption of isosorbide dinitrate (ISDN). First of all, an in situ nasal perfusion technique in rats was used to investigate the effect of pH, concentration of drug solution and different absorption enhancers on the intranasal absorption of ISDN. The absorption enhancers investigated include hydroxypropyl-beta-cyclodextrin (HP-beta-CD), chitosans (CS) of different molecular weight, and poloxamer 188. All of them enhanced the intranasal absorption of ISDN remarkably. It was found that poloxamer 188 had better permeation enhancing effect than that of HP-beta-CD and CS of the same concentration. Thereafter, in vivo behaviors of the selected formulations were studied in rats and the pharmacokinetic parameters were calculated and compared with that of intravenous injection. Both in situ and in vivo studies demonstrated that poloxamer 188 played a key role in promoting intranasal absorption of ISDN. In nasal ciliotoxicity test, all the absorption enhancers investigated showed good safety profiles. Taking both enhancing effect and safety into account, we suggest poloxamer 188 is the most promising as an intranasal absorption enhancer.

Polymer based solutions of bupranolol hydrochloride for intranasal systemic delivery

The present study was aimed at developing intranasal polymer based solutions as alternative route for systemic delivery of Bupranolol hydrochloride (BPH). It is a potent β-blocker drug which upon oral administration undergoes extremely high hepatic first-pass metabolism (>90% in humans). The polymeric solutions were prepared using varying concentrations of polymers like sodium alginate, chitosan, sodium carboxymethylcellulose, methylcellulose (MC), polyvinyl alcohol, carbopol, hydroxypropyl MC, and hydroxypropyl cellulose. The prepared formulations were evaluated in terms of pH of the solution, angular viscosity, drug content, gel strength, gelation temperature, in vitro drug release, in vivo pharmacodynamic studies, histopathological, and stability studies. Except MC based solutions, a biphasic pattern of drug release was obtained in all other cases. Nasal administration of selected batches of polymeric solutions were found to be nontoxic and were able to improve drug bioavailability when compared to oral, nasal, and intravenous solution administrations of BPH.

Study on the mechanisms of chitosan and its derivatives used as transdermal penetration enhancers

The efficacy of chitosan (CS) and its derivatives used as transdermal penetration enhancers has been confirmed in our previous research. This study investigated the mechanisms of penetration enhancement by CS and its derivatives, i.e., N-trimethyl chitosan (TMC) with different degree of quaternization (DQ) and mono-N-carboxylmethyl chitosan (MCC). After treatment with CS, TMCs or MCC, the secondary structure changes of keratin in stratum corneum (SC) from mice were examined by an Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) combined with the application of the second-order derivative, deconvolution and curve-fitting. The water content in the SC was also studied by ATR-FTIR. HaCaT cell lines were employed as the cell models in the study. HaCaT cells were first treated with blank D-Hanks solution, CS or its derivatives, and were then fluorescent labeled with DiBAC(4) (3). The change of membrane potential was measured by a flow cytometer (FCM). Alternatively, the treated HaCaT cells were labeled with NBD-C(6)-HPC and the change of membrane fluidity was examined under a Confocal Laser Scanning Microscope (CLSM). It was found that CS, TMCs and MCC could significantly affect the secondary structure of keratin in SC in different ways. Although the amide II absorption peak of keratin moved to a lower wave number following treatment with CS, TMCs, or MCC, the beta-turning structure of keratin was converted to beta-sheeting and random coiling after treatment with TMCs and was converted to beta-sheeting and alpha-helix following treatment with MCC and CS. At the same time, CS and its derivatives all could increase the water content of SC, decrease HaCaT cells membrane potentials and enhance HaCaT cells membrane fluidity significantly. The effect of TMCs appeared to be independent of their DQ. The results suggest that the mechanisms of transdermal enhancement of CS, TMCs and MCC are closely related to their effects on the secondary structure of keratin and water content in SC, cell membrane potential and fluidity.

Trimethyl chitosan and its applications in drug delivery

Chitosan, a polymer obtained by deacetylation of chitin is widely studied for its pharmaceutical and nonpharmaceutical applications. Recommendations about uses of this polymer although could not be always realized due to limited solubility. Chitosan, for example, has been extensively evaluated for its mucoadhesive and absorption enhancement properties. The positive charge on the chitosan molecule gained by acidic environment in which it is soluble seems to be important for absorption enhancement. However chitosan is not soluble in medium except below pH 5.6. This limits its use as permeation enhancer in body compartments where pH is high. In this regard there is a need for chitosan derivatives with increased solubility, especially at neutral and basic pH values. Trimethylation of chitosan is an effort in this direction. Despite the abundance of the research related to trimethyl chitosan (TMC), the overview of the topic is not available. Hence an attempt is made in this review to cover the recent findings pertaining to synthesis, characterization and applications of TMC especially in pharmaceutical field. TMC has been synthesized by different ways and characterized by FTIR, NMR, DSC etc. This quaternized derivative of chitosan possesses a positive charge and is soluble over a wide range of pH. TMC, being a derivative of cationic polymer enriched with positive charge shows better mucoadhesive, permeation enhancement, drug delivery and DNA delivery properties. TMC can be further derivitized or grafted for modulating properties as solubility, cytotoxicity or cell recognition ability. Apart from these applications, TMC itself and its derivatives exhibit antimicrobial properties also. Quaternization of chitosan not only with methyl group but higher group as ethyl or along with spacer or quaternization of modified chitosan can be of interest too.

Intranasal Bioavailability of Insulin from Carbopol-Based Gel Spray in Rabbits

The purpose of this study was to investigate the nasal absorption of insulin from a carbopol-based nasal gel spray in rabbits. An insulin nasal gel was prepared by dispersing carbopol in distilled water, followed by the addition of insulin solution, then neutralization and viscosity adjustment. The nasal absorption of insulin from the gel, in conscious rabbits, was evaluated in comparison with absorption from an insulin solution. The absolute bioavailability of insulin from the nasal gel was studied using blood glucose level in comparison to intravenous injection. The insulin gel formulation produced a significant hypoglycemic response in rabbits, whereas no response was seen following administration of the insulin solution formulation. The bioavailability of insulin from the nasal gel formulation was 20.6% compared with the intravenous injection. The results of the present study suggest that the carbopol gel promotes the nasal absorption of insulin in rabbit model and due to its sprayability with commercially available spray pumps, could be considered as a preferred platform in nasal drug administration.

Effect of Chitosan-Coated Alginate Microspheres on the Permeability of Caco-2 Cell Monolayers

Alginate microspheres were prepared by emulsification/internal gelation and coated with chitosan. The ability of chitosan-coated alginate microspheres to increase the paracellular transport across Caco-2 cell monolayers was evaluated in comparison to uncoated microspheres and chitosan solutions. Transport studies were performed by using a permeability marker, Lucifer Yellow (LY), and by measuring the transepithelial electric resistance (TEER) variations. Furthermore, the occurrence of cytotoxic effects was assessed by evaluating neutral red uptake in viable cells and lactate dehydrogenase (LDH) release from damaged cells. A 3-fold increase on LY permeability was obtained for coated microspheres when compared to chitosan solutions. TEER variations were in agreement with permeability results. Chitosan solutions exhibited a dose-dependent toxicity, but coated microspheres did not decrease the viability of cells. Chitosan-coated alginate microspheres have potential to be used as carriers of poorly absorbable hydrophilic drugs to the intestinal epithelia and possibly increase their oral bioavailability.

Photoregulation of drug release in azo-dextran nanogels

A simple photoresponsive azo-dextran polymer has been investigated for its ability to act as a nanogel drug carrier. Self aggregation of the azo-dextran polymer leads to the formation of nanogels, AD (5 and 10) in aqueous media, which were characterized by TEM and DLS. When examined under UV light (365 nm), the unloaded nanogels, which were observed to be in the range of 120-290 nm, show dependence on the degree of crosslinking, pH and ionic concentration of the dispersed media. Nanogels, AD (5 and 10), have been loaded with a model fluorophore, rhodamine B and a drug, aspirin, by freeze drying an aqueous dispersion of the nanogels in the presence of the substrate dissolved in water or PBS buffer. The release pattern of the encapsulated bio-active molecules from these nanogels was regulated by (trans-cis) photoisomerization of the azobenzene moiety present in the crosslinker. A comparison of the release behavior of the loaded (rhodamine, aspirin) AD (5 and 10) nanogels reveal that the rate of release of the encapsulated active molecules from the nanogels was slower when the azo moiety was in E-configuration as compared to that the azo in the Z-configuration. The in vitro release behavior of drug from these polymeric micellar systems is revelative of the potential of the nanogels for targeted drug delivery in nanomedicine.

Design and evaluation of biodegradable, biosensitive in situ gelling system for pulsatile delivery of insulin

Biodegradable glucose-sensitive in situ gelling system based on chitosan for pulsatile delivery of insulin was developed. The sols/gels were thoroughly characterized for swelling properties, rheology, texture analysis and water content. The developed glucose-sensitive gels responded to varied glucose concentrations in vitro indicating their ability to function as environment-sensitive systems. Insulin load onto the gels was optimized and was found to affect the rheological behavior of these gels, the final preparation used for in vitro contained 1IU/200mul of the sol. These gels released the entrapped insulin in a pulsatile manner in response to the glucose concentration in vitro. Furthermore, the formulations when evaluated for their in vivo efficacy in streptozotocin-induced diabetic rats at a dose of 3IU/kg, demonstrated their ability to release insulin in response to glucose concentration and were preferred much better against subcutaneously given plain insulin formulation used as the control. Together, these preliminary results indicate that biosensitive chitosan in situ gelling systems have substantial potential as pulsatile delivery systems for insulin.

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.

In vivo evaluation of a nasal insulin delivery system based on thiolated chitosan

The aim of this study was the preparation and in vivo evaluation of a nasal insulin delivery system based on thiolated chitosan. 2-Iminothiolane was covalently attached to chitosan. The resulting conjugate (chitosan-TBA) exhibited 304.9 +/- 63.5 micromol thiol groups per gram polymer. Microparticles were prepared via a new precipitation-micronization technique. The microparticulate delivery system comprised insulin, reduced glutathione and chitosan-TBA (Chito-TBA/Ins) or unmodified chitosan (Chito/Ins) and control microparticles were composed of insulin and mannitol (Mannitol/Ins). Due to a hydration process the size of Chito-TBA/Ins and Chito/Ins microparticles increased in phosphate buffer pH 6.8 2.6- and 2.2-fold, respectively. Fluorescent-labeled insulin-loaded chitosan-TBA microparticles showed a controlled release over 4 h. Chito-TBA/Ins administered nasally to rats led to an absolute bioavailability of 6.9 +/- 1.5%. The blood glucose level decreased for more than 2 h and the calculated absolute pharmacological efficacy was 4.9 +/- 1.4%. Chito/Ins, in comparison, displayed a bioavailability of 4.2 +/- 1.8% and a pharmacological efficacy of 0.7 +/- 0.6%. Mannitol/Ins showed a bioavailability of 1.6 +/- 0.4% and no reduction of the blood glucose level at all. According to these findings microparticles comprising chitosan-TBA seem to have substantial higher potential for nasal insulin administration than unmodified chitosan.

Effect of cationized gelatins on the paracellular transport of drugs through caco-2 cell monolayers

Cationized gelatins, candidate absorption enhancers, were prepared by addition of ethylenediamine or spermine to gelatin and the effects of the resulting ethylenediaminated gelatin (EG) and sperminated gelatin (SG) on the paracellular transport of 5(6)-carboxyfluorescein (CF), FITC-dextran-4 (FD4), and insulin through caco-2 cell monolayers were examined. The Renkin function was used for characterization of the paracellular pathway and changes in the pore radius (R) and pore occupancy/length ratio (epsilon/L) calculated from the apparent permeability coefficients (P(app)) of CF and FD4 are discussed. Ethylenediaminetetraacetic acid (EDTA) increased the R of the caco-2 cell monolayer and the P(app) of all compounds examined was markedly increased by the addition of EDTA. On the other hand, EG and SG did not increase R and their enhancing effects were not as strong as those of EDTA. The increase in epsilon/L could be the enhancing mechanism for the cationized gelatins. The number of pathways for water-soluble drugs, such as CF and FD4, in the caco-2 monolayers could be increased by the addition of the cationized gelatins. The ratios of the permeability coefficients of insulin (observed/calculated based on the Renkin function) suggest that insulin undergoes enzymatic degradation during transport which is not inhibited by enhancers.

Rapid-onset intranasal delivery of metoclopramide hydrochloride. Part I. Influence of formulation variables on drug absorption in anesthetized rats

Intranasal (IN) administration is a promising approach for rapid-onset delivery of medications and to circumvent their first-pass elimination when taken orally. Metoclopramide (MCP) is a potent antiemetic, effective even for preventing emesis induced by cancer chemotherapy. The feasibility of developing an efficacious intranasal formulation of metoclopramide has been undertaken in this study. The nasal absorption of MCP was studied in anesthetized rats over 60min using the in vivo in situ technique. The influence of several formulation variables, vis., pH and the addition of preservative, viscosity and absorption enhancing agents on the nasal MCP absorption was examined. The data obtained showed that MCP was well absorbed nasally where almost 90% of the drug was absorbed after 60min from the rat nasal cavity. The MCP absorption was pH-dependant such that the apparent first-order rate constant of absorption (K(app)) was almost tripled when the pH of the solution was increased from 5 to 8. However, deviation from the classical pH-partition theory was observed pointing to the role of aqueous pore pathway in MCP nasal absorption. The K(app) was significantly increased (P<0.05) by incorporation of 0.01% of the preservative benzalkonium chloride. Conversely, increasing the solution viscosity by the use of hydroxylpropyl methylcellulose adversely affected the rate of absorption. The use of enhancers namely sodium deoxycholate, sodium cholate, chitosan low and high molecular weight, protamine sulphate and poly-l-arginine resulted in significant increase in MCP absorption. The highest promoting effect was observed with the bile salt sodium deoxycholate where about 92% of the drug was absorbed in 25min from the rat nasal cavity and the K(app) showed more than two-fold increase as compared to control (from 0.0452 to 0.1017min(-1)).

Rapid-onset intranasal delivery of metoclopramide hydrochloride Part II: Safety of various absorption enhancers and pharmacokinetic evaluation

In the present study, several nasal absorption enhancers, used in metoclopramide hydrochloride (MCP HCl) nasal solutions, have been screened for their possible damaging effect in the in vitro human erythrocytes lysis experiment. Moreover, the in vivo leaching of biological markers from the rat nasal epithelium was used as a quantitative assessment for possible nasal mucosal irritation whereby the extent of release of total protein and lactate dehydrogenase (LDH) in the nasal lavage fluid was determined. Results showed that insignificant hemolysis from normal saline (P<0.05) occurred with the enhancer protamine sulphate while poly-l-arginine and sodium cholate demonstrated very low (<15%) hemolysis and caused insignificant protein and LDH release from the rat nasal mucosa. Conversely, sodium deoxycholate and chitosan polymers (either of low or high molecular weight) showed high (>60%) hemolysis in vitro and the release of the biological markers in vivo was significantly higher (P<0.05) than the control solution (no enhancer). A significant correlation (P<0.05) existed between the enhancement effect of MCP HCl nasal absorption and the amounts of protein (r=0.85) and LDH (r=0.88). Furthermore, the pharmacokinetics of MCP HCl was determined after intravenous (IV), per-oral and intranasal administration of 10mg drug dose in rabbits. The application of a nasal spray (NS) solution containing 0.5% sodium cholate resulted in a significant improvement (P<0.05) in both the rate and extent of absorption of MCP HCl where the T(max) achieved was 23.3min as compared to 50min in case of the oral solution while the area under the serum concentration-time curve (AUC(0-infinity)) were 506.1, 434.9 and 278.7microg/mlmin for IV, NS and oral solutions, respectively. These values corresponded to absolute bioavailabilities of 87.21 and 55.61% for the NS and oral solutions, respectively. It could thus be concluded that NS of MCP HCl represents a viable approach to achieving rapid and high systemic drug absorption during the emergency treatment of severe emesis.

Aminated gelatin microspheres as a nasal delivery system for peptide drugs: Evaluation of in vitro release and in vivo insulin absorption in rats

Aminated gelatin microspheres (AGMS) was investigated as a nasal drug delivery system for peptide drugs. The in vitro drug release from microspheres was evaluated using a fluorescein-labeled insulin (RITC-insulin) and FITC-dextran with a molecular weight of 4.4 kDa (FD-4) as model drugs. RITC-insulin release from AGMS was significantly slower than from native gelatin microspheres (GMS), with a cumulate release of 18.4% and 32.4% within 30 min, and 56.9% and 75.1% within 8 h respectively. However, the release of FD-4 from both AGMS and GMS was quite rapid and no difference was observed for the two microspheres. The electrostatic interactions between the model drugs and the microspheres were supposed to be the main factor that controlled the release behavior. The absorption enhancing effect was estimated by measuring the changes of plasma glucose concentrations of healthy rats following intranasal administration of insulin-incorporated microspheres in both suspension and dry powder forms. AGMS could significantly increase the nasal absorption of insulin in rats when administered in a dry powder formulation, but no significant hypoglycemic effect was observed when given in suspensions. One of the mechanisms for the increased insulin absorption was attributed to the hydrogel nature of the microspheres that could absorb water from the nasal mucosa and thus resulted in a temporarily dehydration of the epithelium membrane and opening of the tight junctions. The positive charge of the AGMS has also evidently contributed to the absorption enhancing effect. In addition, the mucoadhesive properties of AGMS might also have played a role to the total effect. AGMS might be a new candidate carrier for the nasal delivery of peptide drugs.

Preparation and characterization of sodium hexameta phosphate cross-linked chitosan microspheres for controlled and sustained delivery of centchroman

The cross-linked microspheres using chitosan with different molecular weights and degree of deacetylation have been prepared in presence of sodium hexameta polyphosphate (SHMP) as physical cross-linker. The degree of cross-linking through electrostatic interactions in chitosan microspheres has been evaluated by varying the charge density on chitosan and varying degree of dissociation of sodium hexameta polyphosphate by solution pH. The degree of deacetylation and molecular weight of chitosan has controlled electrostatic interactions between hexameta polyphosphate anions and chitosan, which played significant role in swelling, loading and release characteristics of chitosan microspheres for centchroman. The microspheres prepared by hexameta polyphosphate anions cross-linker were compact and more hydrophobic than covalently cross-linked microspheres, which has been attributed to the participation of all amino groups of chitosan in physical cross-linking with added hexameta polyphosphate anions. The microspheres prepared under different experimental conditions have shown an initial step of burst release, which was followed by a step of controlled release for centchroman. The extent of drug release in these steps has shown dependence on properties of chitosan and degree of cross-linking between chitosan and added polyanions. The degree of swelling and release characteristics of microspheres was also studied in presence of organic and inorganic salts, which shown significant effect on controlled characteristics of microspheres due to variations in ionic strength of the medium. The initial step of drug release has followed first order kinetics and become zero order after attaining an equilibrium degree of swelling in these microspheres. The microspheres prepared using chitosan with 62% (w/w) degree of deacetylation and molecular weight of 1134kgmol(-1) have shown a sustained release for centchroman for 50h at 4% (w/w) degree of cross-linking with SHMP.

Glutaraldehyde and glyoxal cross-linked chitosan microspheres for controlled delivery of centchroman

Glutaraldehyde and glyoxal cross-linked microspheres were prepared using chitosan with different molecular weights (MWs) and degrees of deacetylation (DDAs) for sustained release of centchroman under physiological conditions. The DDA in chitosan was determined by different methods, and the samples were categorized as chitosan with low (48%), medium (62%), and high (75%) DDA. The size and shape of the microspheres were determined by scanning electron microscopy (SEM), and hydrophobicity was determined by adsorption of Rose Bengal dye on microspheres cross-linked with glutaraldehyde or glyoxal. The effect of MW, DDA, and degree of cross-linking in microspheres was studied on the degree of swelling, as well as by the loading and release of centchroman. The glyoxal cross-linked microspheres were more compact and hydrophobic and showed better sustained release in companion to chitosan microspheres and glutaraldehyde cross-linked microspheres. The linear fractional release of centchroman with the square root of time indicated a Fickian behavior of centchroman, and the microspheres also showed zero-order release kinetics for centchroman.

Nasal delivery of insulin using bioadhesive chitosan gels

Recently nasal delivery of insulin has gained considerable attention. Some limitations of this route include rapid mucociliary clearance of the drug from the site of deposition resulting in short time span available for absorption and low permeability of the nasal membrane for peptides. The objective of the present study was development of a chitosan bioadhesive gel for nasal delivery of insulin. A nasal perfusion test was used to study the toxicity of 4 absorption enhancers: saponin, sodium deoxycholate, ethylendiamine tetra-Acetic Acid (EDTA) and lecithin. The gels contained 4,000 Iu/dl insulin, 2 or 4% of low and medium molecular weight of chitosan, and lecithin or EDTA. Drug release was studied by a membraneless diffusion method and bioadhesion by a modified tensiometry test. The optimized gel was administered nasally in diabetic rats. The serum insulin levels were analyzed by an insulin enzyme immunoassay kit and serum glucose by glucose oxidase method kits. Formulations containing 2% of low molecular weight of chitosan with EDTA had higher release percentage and dissolution efficiency (DE)(2.5%), lower T(50%) (Time required to release 50% of the drug), mean dissolution time, and bioadhesion than gels containing 4% of medium molecular weight of chitosan with lecithin. Insulin was released by a zero-order kinetic from the gels. The gel of 2% medium molecular weight of chitosan with EDTA caused increase in insulin absorption and reduction the glucose level by as much as 46% of the intravenous route. Considering our in vitro and in vivo studies, the proposed gel formulation could be a useful preparation for controlled delivery of insulin through the nasal route.

Effect of aminated gelatin on the nasal absorption of insulin in rats

Absorption enhancers, which increase the permeability of drugs through epithelial membranes without damaging them, are especially useful for intranasal administration of peptide drugs. In this study, aminated gelatins, candidate enhancers, having different numbers of amino groups were prepared from gelatin (H-gelatin, isoelectric point = 9.0, MW 100 kDa) and a partial gelatin hydrolysate (L-gelatin, isoelectric point = 8.0, MW 5 kDa), and the enhancing effects on the nasal absorption of insulin, used as a model peptide drug, and 5(6)-carboxyfluorescein (CF), a paracellular marker, were examined in rats. The enhancing effect on insulin and CF depends on the MW and number of amino groups. A high correlation between the enhancing effects on insulin and CF was observed and this suggests that an increase in the paracellular permeability is the mechanism governing the nasal absorption-enhancement of aminated gelatins, at least as far as insulin and CF are concerned. The enhancing mechanism might be shared with other cationic polymers having absorption-enhancing effects.