Improved oral bioavailability of alendronate via the mucoadhesive liposomal delivery system

This study aimed to design the chitosan coated liposomes of alendronate and optimize their in vitro/in vivo characteristics to improve the bioavailability as well as potentially to reduce the mucosal irritation of alendronate. Liposomes of alendronate were prepared with DSPC/DSPG by using thin layer film hydration method and then the surface of anionic liposomes was coated by chitosan. In vitro characteristics of liposomes (e.g., stability in various biological media, mucoadhesiveness and cellular uptake profiles) were evaluated along with the pharmacokinetic studies in rats. Lipid vesicles of 200 nm size were obtained with narrow size distribution (PI<0.1) and subsequently coated with chitosan. Chitosan coated liposomes were stable for 24 h without either size change or drug leakage in various biological fluids including simulated gastric fluids and intestinal fluids. Furthermore, it exhibited strong mucoadhesive properties. Compared to the untreated drug (non-liposome), the chitosan coated liposomes indicated significantly (p<0.05) increased cellular uptake of alendronate in Caco-2 cells and also 2.6-fold enhancement in oral bioavailability of alendronate in rats. Taken all together, the mucoadhesive liposomes for the oral delivery of alendronate was prepared by using DSPC and DSPG with narrow size distribution and appeared to be effective to enhance the bioavailability of alendronate in rats.     

Muco-adhesive multivesicular liposomes as an effective carrier for transmucosal insulin delivery

Considering limitations of conventional insulin therapies, the present study characterizes usefulness of novel mucoadhesive multivesicular liposomes as a mucoadhesive sustained release carrier of insulin via nasal and ocular routes, thus attempts to develop non-invasive carrier system for the controlled release of bioactives. Multivesicular liposomes (MVLs) of 26-34 microm were prepared with a high protein loading (58-62%) and were coated with chitosan and carbopol. These mucoadhesive carriers were characterized by zeta potential studies, in vitro mucoadhesion test and insulin protective ability against nasal aminopeptidase. In vitro, mucoadhesive carriers released insulin for a period of 7-9 days compared to 24 h of conventional liposomes. After intranasal administration to STZ induced diabetic rats, the mucoadhesive MVLs (chitosan coated MVLs) effectively reduced plasma glucose level up to 2 days (35% reduction), compared to non-coated MVLs (32% at 12 h) and conventional liposomes (34% at 8 h). Although the differences are statistically insignificant, chitosan coated formulation has shown a better hypoglycemic profile as the effects were prolonged compared to carbopol coated formulation. When compared to ocular route, chitosan formulation after nasal administration has shown better therapeutic profile as the hypoglycemic effects were prolonged until 72 h. The effectiveness of this chitosan coated MVLs was further demonstrated by the significant quantities of ELISA detectable insulin levels after nasal (334.6 microIu/ml) and ocular (186.3 microIu/ml) administration. These results demonstrate that mucoadhesive carrier is a viable option for a sustained release transmucosal insulin carrier, and open an avenue to develop a non-invasive carrier platform for the controlled release of bioactives.     

Muco-adhesive multivesicular liposomes as an effective carrier for transmucosal insulin delivery

Considering limitations of conventional insulin therapies, the present study characterizes usefulness of novel mucoadhesive multivesicular liposomes as a mucoadhesive sustained release carrier of insulin via nasal and ocular routes, thus attempts to develop non-invasive carrier system for the controlled release of bioactives. Multivesicular liposomes (MVLs) of 26–34 μm were prepared with a high protein loading (58–62%) and were coated with chitosan and carbopol. These mucoadhesive carriers were characterized by zeta potential studies, in vitro mucoadhesion test and insulin protective ability against nasal aminopeptidase. In vitro, mucoadhesive carriers released insulin for a period of 7–9 days compared to 24 h of conventional liposomes. After intranasal administration to STZ induced diabetic rats, the mucoadhesive MVLs (chitosan coated MVLs) effectively reduced plasma glucose level up to 2 days (35% reduction), compared to non-coated MVLs (32% at 12 h) and conventional liposomes (34% at 8 h). Although the differences are statistically insignificant, chitosan coated formulation has shown a better hypoglycemic profile as the effects were prolonged compared to carbopol coated formulation. When compared to ocular route, chitosan formulation after nasal administration has shown better therapeutic profile as the hypoglycemic effects were prolonged until 72 h. The effectiveness of this chitosan coated MVLs was further demonstrated by the significant quantities of ELISA detectable insulin levels after nasal (334.6 μIu/ml) and ocular (186.3 μIu/ml) administration. These results demonstrate that mucoadhesive carrier is a viable option for a sustained release transmucosal insulin carrier, and open an avenue to develop a non-invasive carrier platform for the controlled release of bioactives.     

Effectiveness of submicron-sized, chitosan-coated liposomes in oral administration of peptide drugs

The mucoadhesive behavior of chitosan-coated liposomes in the intestinal tract of the rat was examined to elucidate their particle size effects on the absorption of an entrapped drug, calcitonin. The intestine was removed from rats after oral administration of liposomes containing a fluorescent dye, and its various parts were observed with confocal laser scanning microscopy. Penetration of submicron-sized liposomes (ssLip) or chitosan-coated ssLip (ssCS-Lip) into the mucosa was observed, while such behavior was not observed for the multilamellar liposomes, even when coated with chitosan (CS-Lip). The retentive property of ssCS-Lip was confirmed by measuring the amount of dye in each part of the intestine. The pharmacologic effects of calcitonin-loaded liposomes of different particle size were measured after oral administration in rats. The pharmacologic effect of oral administration of ssLip coated with chitosan was detected up to 120 h after administration. The extensive pharmacologic effect of ssCS-Lip was attributed to their prolonged retention in the intestinal mucosa, partly owing to their penetrative property into the intestinal mucosa. The chitosan-coated ssLip, with their higher retentive property in the intestinal tract, are much more effective than ssLip and CS-Lip in improving the enteral absorption of peptide drugs.     

Development and characterization of mucoadhesive microspheres bearing salbutamol for nasal delivery

Mucoadhesive drug delivery systems are those that provide intimate contact of the drug with the mucosa for an extended period of time. In our present work, mucoadhesive chitosan microspheres were prepared by emulsion solvent method. Formulations were characterized for various physicochemical attributes, shape, surface morphology, size, and size distribution, drug payload, swelling ability, and mucoadhesion. The effect of drug, citric acid, and permeation enhancer concentration on the physicochemical properties was studied. Crosslinked chitosan microspheres showed very good mucoadhesion, which was decreased on increasing the drug concentration and citric acid concentration, and slightly improved upon incorporation of permeation enhancer. The in vitro drug release and in vitro drug permeability through mucous membrane were performed, and slow release/permeation was noted with chitosan citrate complexed microspheres compared with noncomplexed chitosan microspheres. The in vivo performance of mucoadhesive microspheres formulations showed prolonged and controlled release of salbutamol as compared with oral administration of conventional dosage form.     

Liposome coated with low molecular weight chitosan and its potential use in ocular drug delivery

In this study liposome coated with low molecular weight chitosan (LCH) was proposed and investigated its in vitro and in vivo properties, and its potential use in ocular drug delivery was evaluated. LCH with a molecular weight of 8 kDa was prepared and coated on liposome loaded with diclofenac sodium. The LCH coating changed the liposome surface charge and slightly increased its particle size, while the drug encapsulation was not affected. After coating, the liposome displayed a prolonged in vitro drug release profile. LCH coated liposome also demonstrated an improved physicochemical stability at 25 °C in a 30-day storage period. The ocular bioadhesion property was evaluated by rabbit in vivo precorneal retention, and LCH coated liposome achieved a significantly prolonged retention compared with non-coated liposome or drug solution. The LCH coating also displayed a potential penetration enhancing effect for transcorneal delivery of the drug. In the ocular tolerance study, no irritation or toxicity was caused by continual administration of LCH coated liposome in a total period of 7 days. In conclusion, the LCH coating significantly modified the properties of liposome and brought a series of notable advantages for ocular drug delivery.     

N-trimethyl chitosan-modified liposomes as carriers for oral delivery of salmon calcitonin

Therapeutic peptide and protein drugs have high specificity and activity in their functions but present challenges in their administration route, requiring development of new delivery systems to improve their bioavailability. The aim of this work was to investigate the role of N-trimethyl chitosan- (TMC-) coated liposomes in the oral administration of calcitonin. TMC with a degree of quaternization around 78% was synthesized and its mucoadhesive properties were examined in vitro using the mucin-particle method, which confirmed that TMC showed mucoadhesion comparable to that of chitosan. TMC-coated liposomes containing calcitonin were prepared and characterized as having a particle size of 262 nm, zeta potential of 35.8 mV and high entrapment efficiency (89.1%). The in vivo evaluation of mucoadhesion was carried out using confocal laser microscopy to observe the residence time and permeation extent after intragastric administration. The results showed that TMC-coated liposomes prolonged the residence time and increased the penetration effect of the liposomal system compared to non-coated liposomes. The study of pharmacological effects confirmed that TMC-coated liposomes increased the area above the blood calcium concentration-time curves (AAC) from 3.13?±?20.50 to 448.84?±?103.56 compared to the calcitonin solution. These results support the feasibility of TMC-coated liposomes as a new oral delivery system for peptide and protein drugs.     

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

Vaginal administration of sildenafil citrate has shown recently to develop efficiently the uterine lining with subsequent successful embryo implantation following in vitro fertilization. The aim of the present study was to develop sildenafil-loaded liposomes coated with bioadhesive polymers for enhanced vaginal retention and improved drug permeation. Three liposomal formulae were prepared by thin-film method using different phospholipid:cholesterol ratios. The optimal liposomal formulation was coated with bioadhesive polymers (chitosan and HPMC). A marked increase in liposomal size and zeta potential was observed for all coated liposomal formulations. HPMC-coated liposomes showed the greater bioadhesion and higher entrapment efficiency than chitosan-coated formulae. The in vitro release studies showed prolonged release of sildenafil from coated liposomes as compared to uncoated liposomes and sildenafil solution. Ex vivo permeation study revealed the enhanced permeation of coated relative to uncoated liposomes. Chitosan-coated formula demonstrated highest drug permeation and was thus selected for further investigations. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful coating of the liposomes by chitosan. Histopathological in vivo testing proved the efficacy of chitosan-coated liposomes to improve blood flow to the vaginal endometrium and to increase endometrial thickness. Chitosan-coated liposomes can be considered as potential novel drug delivery system intended for the vaginal administration of sildenafil, which would prolong system's retention at the vaginal site and enhance the permeation of sildenafil to uterine blood circulation.     

The effect of particle structure of chitosan-coated liposomes and type of chitosan on oral delivery of calcitonin

To optimize the properties of chitosan-coated liposomes for oral administration of peptide drugs, we examined the effect of type of chitosan and the structure of liposomal systems on the mucoadhesiveness of liposomes and resultant pharmacological effects of the liposomal peptide drug. A low-molecular weight chitosan (LCS) and a high-molecular weight chitosan (CS) were used as coating polymers of liposomes containing elcatonin (eCT). The muco-penetrative behaviors across the mucous gel layer covering the intestinal epithelial cells and the pharmacological effect after intragastric administration were determined in rats. The results showed that both LCS-coated liposomes (LCS-Lips) and CS-coated liposomes (CS-Lips) could permeate the mucous layer in the small intestine. The most interesting result was that LCS-Lips containing eCT showed remarkably more prolonged effectiveness in decreasing the blood calcium concentration than did CS-Lips containing eCT, moreover, it was also found that LCS had more efficiency to protect eCT from the enzymatic degradation than CS. In comparing the area above the plasma calcium concentration time curves (AAC) values among eCT-containing liposomes with different structures, i.e. eCT adsorbed on coated liposomes (eCT-ad-CS-Lip, eCT-ad-LCS-Lips) and eCT encapsulated in coated liposomes (eCT-encap-CS-Lips, eCT-encap-LCS-Lips), eCT-encap-CS-Lip showed much higher effectiveness than eCT-ad-CS-Lip. However, the AAC value for eCT-ad-LCS-Lip was comparable to that for eCT-encap-CS-Lip, while the value for eCT-ad-CS-Lip was nearly zero. These results suggested that LCS is a good mucoadhesive polymer candidate for enhancing the bioavailability of orally administered peptide containing liposomes, while encapsulation of eCT within the liposomal particles is important to protect eCT against enzymatic degradation in the gastrointestinal (GI) tract.     

The effect of particle structure of chitosan-coated liposomes and type of chitosan on oral delivery of calcitonin

To optimize the properties of chitosan-coated liposomes for oral administration of peptide drugs, we examined the effect of type of chitosan and the structure of liposomal systems on the mucoadhesiveness of liposomes and resultant pharmacological effects of the liposomal peptide drug. A low-molecular weight chitosan (LCS) and a high-molecular weight chitosan (CS) were used as coating polymers of liposomes containing elcatonin (eCT). The muco-penetrative behaviors across the mucous gel layer covering the intestinal epithelial cells and the pharmacological effect after intragastric administration were determined in rats. The results showed that both LCS-coated liposomes (LCS-Lips) and CS-coated liposomes (CS-Lips) could permeate the mucous layer in the small intestine. The most interesting result was that LCS-Lips containing eCT showed remarkably more prolonged effectiveness in decreasing the blood calcium concentration than did CS-Lips containing eCT, moreover, it was also found that LCS had more efficiency to protect eCT from the enzymatic degradation than CS. In comparing the area above the plasma calcium concentration time curves (AAC) values among eCT-containing liposomes with different structures, i.e. eCT adsorbed on coated liposomes (eCT-ad-CS-Lip, eCT-ad-LCS-Lips) and eCT encapsulated in coated liposomes (eCT-encap-CS-Lips, eCT-encap-LCS-Lips), eCT-encap-CS-Lip showed much higher effectiveness than eCT-ad-CS-Lip. However, the AAC value for eCT-ad-LCS-Lip was comparable to that for eCT-encap-CS-Lip, while the value for eCT-ad-CS-Lip was nearly zero. These results suggested that LCS is a good mucoadhesive polymer candidate for enhancing the bioavailability of orally administered peptide containing liposomes, while encapsulation of eCT within the liposomal particles is important to protect eCT against enzymatic degradation in the gastrointestinal (GI) tract.     

Improved Permeability of Acyclovir: Optimization of Mucoadhesive Liposomes Using the Phospholipid Vesicle-Based Permeation Assay

The antiviral drug acyclovir (ACV) suffers from poor solubility both in lipophilic and hydrophilic environment, leading to low and highly variable bioavailability. To overcome these limitations, this study aimed at designing mucoadhesive ACV-containing liposomes to improve its permeability. Liposomes were prepared from egg phosphatidylcholine (E-PC) and E-PC/egg phosphatidylglycerol (E-PC/E-PG) and their surfaces coated with Carbopol. All liposomal formulations were fully characterized and for the first time the phospholipid vesicle-based permeation assay (PVPA) was used for testing in vitro permeability of drug from mucoadhesive liposome formulations. The negatively charged E-PC/E-PG liposomes could encapsulate more ACV than neutral E-PC liposomes. Coating with Carbopol increased the entrapment in the neutral E-PC liposomes. The incorporation of ACV into liposomes exhibited significant increase in its in vitro permeability, compared with its aqueous solution. The neutral E-PC liposomal formulations exhibited higher ACV permeability values compared with charged E-PC/E-PG formulations. Coating with Carbopol significantly enhanced the permeability from the E-PC/E-PG liposomes, as well as sonicated E-PC liposomes, which showed the highest permeability of all tested formulations. The increased permeability was according to the formulations’ mucoadhesive properties. This indicates that the PVPA is suitable to distinguish between permeability of ACV from different mucoadhesive liposome formulations developed for various routes of administration.     

N-trimethyl chitosan-modified liposomes as carriers for oral delivery of salmon calcitonin

Therapeutic peptide and protein drugs have high specificity and activity in their functions but present challenges in their administration route, requiring development of new delivery systems to improve their bioavailability. The aim of this work was to investigate the role of N-trimethyl chitosan- (TMC-) coated liposomes in the oral administration of calcitonin. TMC with a degree of quaternization around 78% was synthesized and its mucoadhesive properties were examined in vitro using the mucin-particle method, which confirmed that TMC showed mucoadhesion comparable to that of chitosan. TMC-coated liposomes containing calcitonin were prepared and characterized as having a particle size of 262?nm, zeta potential of 35.8 mV and high entrapment efficiency (89.1%). The in vivo evaluation of mucoadhesion was carried out using confocal laser microscopy to observe the residence time and permeation extent after intragastric administration. The results showed that TMC-coated liposomes prolonged the residence time and increased the penetration effect of the liposomal system compared to non-coated liposomes. The study of pharmacological effects confirmed that TMC-coated liposomes increased the area above the blood calcium concentration-time curves (AAC) from 3.13?±?20.50 to 448.84?±?103.56 compared to the calcitonin solution. These results support the feasibility of TMC-coated liposomes as a new oral delivery system for peptide and protein drugs.     

Microemulsion based intranasal delivery system for treatment of insomnia

The aim of this investigation was to prepare and characterize microemulsions/mucoadhesive microemulsions of Diazepam (D), Lorazepam (L) and Alprazolam (A), evaluate their pharmacodynamic performances by performing comparative sleep induction studies in male albino rats to assess their role in effective management of insomnia patients. Microemulsions of Diazepam (DME), Lorazepam (LME) and Alprazolam (AME) were prepared by titration method and characterized for drug content, globule size distribution and zeta potential, nasal toxicity and sleep induction. DME, LME and AME were transparent and stable with mean globule size and zeta potential in the range of 95.6?nm to 141.7?nm and -2.205?to -0.111?mV respectively. The prepared microemulsions exhibited reversible nasal toxicity. Onset of sleep and duration of sleep were observed in the following order: Lorazepam > Alprazolam>Diazepam. Faster onset of sleep following intranasal administration of microemulsions (<20?min) compared to oral administration (29-33?min) and control group (>45?min) for all three drugs suggested selective nose-to-brain transport of drug(s). Intranasal administration of microemulsion based formulations resulted in even faster onset of sleep (<12?min) with intranasal mucoadhesive microemulsion(s) resulting in fastest onset of sleep (<9?min). Duration of sleep was longest with the intranasal mucoadhesive microemulsions. These results are suggestive of larger extent of distribution of drug(s) to brain after intranasal administration of mucoadhesive microemulsion(s). These results are further corroborated with by loss or rightening reflex and startle reflex at earlier time points (within 10?min and 15?min respectively) with mucoadhesive microemulsions. Thus, the results of this investigation indicated rapid and larger extent of drug transport to the rat brain resulting in rapid induction of sleep followed by prolonged duration of sleep in rats following intranasal administration of mucoadhesive microemulsion(s). However, the role of microemulsion based formulations developed in this investigation in clinical practice can only be established after animal studies in two different animal models followed by extensive clinical trials.     

Novel mucoadhesion tests for polymers and polymer-coated particles to design optimal mucoadhesive drug delivery systems

To design an effective particulate drug delivery system having mucoadhesive function, several mucoadhesion tests for polymers and the resultant particulate systems were developed. Mucin particle method is a simple mucoadhesion test for polymers, in which the commercial mucin particles are used. By measuring the change in particle size or zeta potential of the mucin particle in a certain concentration of polymer solution, we could estimate the extent of their mucoadhesive property. BIACORE method is also a novel mucoadhesion test for polymers. On passing through the mucin suspension on the polymer-immobilized chip of BIACORE instrument, the interaction was quantitatively evaluated with the change in its response diagram. By using these mucoadhesion tests, we detected a strong mucoadhesive property of several types of chitosan and Carbopol. Evaluation of mucoadhesive property of polymer-coated particulate systems was demonstrated with the particle counting method developed by us. To detect the mucoadhesive phenomena in the intestinal tract, we observed the rat intestine with the confocal laser scanning microscope (CLSM) after oral administration of the particulate systems. The resultant photographs clearly showed a longer retention of submicron-sized chitosan-coated liposomes (ssCS-Lip) in the intestinal tract than other liposomal particles tested such as non-coated liposomes and chitosan-coated multilamellar one. These observations explained well the superiority of the ssCS-Lip as drug carrier in oral administration of calcitonin in rats than other liposomal particles.     

Mucoadhesive nanoparticulate systems for peptide drug delivery

This chapter describes the preparation of and methods for evaluating mucoadhesive nanoparticulate systems, including liposomes and polymeric nanoparticles. Mucoadhesive ability is conferred on the particulate systems by coating their surface with mucoadhesive polymers such as chitosan and Carbopol. The feasibility of this surface modification was confirmed by measuring the zeta potential. Several methods of evaluating the mucoadhesive properties of particulate systems have been reported in the literature. We have also developed some novel evaluation procedures including a particle counting method using a Coulter counter for polymer-coated liposomes. The mucoadhesive properties of the polymer-coated liposomes and polymeric nanoparticles were confirmed by means of these mucoadhesion tests. In applying these mucoadhesive nanoparticles to the oral and pulmonary administration of peptide drugs, more effective and prolonged action was observed in comparison with non-coated systems, thereby confirming the usefulness of mucoadhesive nanoparticulate systems for the delivery of peptide drugs.     

Mucoadhesive Microspheres for Gastroretentive Delivery of Acyclovir: In Vitro and In Vivo Evaluation

The aim of the present investigation was to evaluate the potential use of mucoadhesive microspheres for gastroretentive delivery of acyclovir. Chitosan, thiolated chitosan, Carbopol 71G and Methocel K15M were used as mucoadhesive polymers. Microsphere formulations were prepared using emulsion-chemical crosslinking technique and evaluated in vitro, ex-vivo and in-vivo. Gelatin capsules containing drug powder showed complete dissolution (90.5 +/- 3.6%) in 1 h. The release of drug was prolonged to 12 h (78.8 +/- 3.9) when incorporated into mucoadhesive microspheres. The poor bioavailability of acyclovir is attributed to short retention of its dosage form at the absorption sites (in upper gastrointestinal tract to duodenum and jejunum). The results of mucoadhesion study showed better retention of thiolated chitosan microspheres (8.0 +/- 0.8 h) in duodenal and jejunum regions of intestine. The results of qualitative and quantitative GI distribution study also showed significant higher retention of mucoadhesive microspheres in upper GI tract. Pharmacokinetic study revealed that administration of mucoadhesive microspheres could maintain measurable plasma concentration of acyclovir through 24 h, as compared to 5 h after its administration in solution form. Thiolated chitosan microsphere showed superiority over the other formulations as observed with nearly 4.0-fold higher AUC(0-24) value (1,090 +/- 51 ng h/ml) in comparison to drug solution (281 +/- 28 ng h/ml). Overall, the result indicated prolonged delivery with significant improvement in oral bioavailability of acyclovir from mucoadhesive microspheres due to enhanced retention in the upper GI tract.     

pH-sensitive and mucoadhesive thiolated Eudragit-coated chitosan microspheres

The aim of this study was using Eudragit-cysteine conjugate to coat on chitosan microspheres (CMs) for developing an oral protein drug delivery system, having mucoadhesive and pH-sensitive property. Bovine serum albumin (BSA) as a protein model drug was loaded in thiolated Eudragit-coated CMs (TECMs) to study the release character of the delivery system. After thiolated Eudragit coating, it was found that the release rate of BSA from BSA-loaded TECMs was observably suppressed at pH 2.0 PBS solution, while at pH 7.4 PBS solution the BSA can be sustainingly released for several hours. The structural integrity of BSA released from BSA-loaded TECMs was guaranteed by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and circular dichroism (CD) spectroscopy. The mucoadhesive property of TECMs was evaluated and compared with CMs and Eudragit-coated chitosan microspheres (ECMs). It was confirmed that after coating thiolated Eudragit, the percentage of TECMs remained on the isolated porcine intestinal mucosa surface was significantly higher than those of CMs and ECMs. Likewise, gamma camera imaging of Tc-99m labeled microsphere distribution in rats after oral administration also suggested that TECMs had comparatively stronger mucoadhesive characters. Therefore, our results indicated that TECMs have potentials to be an oral protein drug carrier.     

Formulation and evaluation of carnosic acid nanoparticulate system for upregulation of neurotrophins in the brain upon intranasal administration

To develop formulations of carnosic acid nanoparticles and to assess their in vivo efficacy to enhance the expression of neurotrophins in rat model. Carnosic acid loaded chitosan nanoparticles were prepared by ionotropic gelation technique using central composite design. Response surface methodology was used to assess the effect of three factors namely chitosan concentration (0.1–1% w/v), tri-poly phosphate concentration (0.1–1% w/v) and sonication time (2–10?min) on the response variables such as particle size, zeta potential, drug encapsulation efficiency and drug release. The neurotrophins level in the rat brain upon intranasal administration of optimized batch of carnosic acid nanoparticles was determined. The experimental values for the formulation were in good agreement with those predicted by the mathematical models. A single intranasal administration of the optimized formulation of carnosic acid nanoparticles was sufficient to result in comparable levels of endogenous neurotrophins level in the brain that was almost on par with four, once a day intranasal administration of solution in rats. The results clearly demonstrated the fact that nanoparticulate drug delivery system for intranasal administration of carnosic acid would require less number of administrations to elicit the required pharmacological activity owing to its ability to localize on the olfactory mucosal region and provide controlled delivery of carnosic acid for prolonged time periods.     

Chitosan–aprotinin coated liposomes for oral peptide delivery: Development, characterisation and in vivo evaluation

In order to improve the systemic uptake of therapeutic peptides/proteins after oral administration, the polymer-protease inhibitor conjugate chitosan–aprotinin was synthesised and polyelectrolyte complexes between negatively charged multilamellar vesicles (MLV) and positively charged chitosan–aprotinin conjugate were prepared. It could be demonstrated that chitosan–aprotinin was capable of significantly inhibiting Trypsin in vitro in concentrations of 0.05% and 0.1%, whereas no inhibition was observed in the presence of 0.1% chitosan. The size range of the prepared MLV was between 3 and 4.5 μm and the initially negative zeta potential (ca. −90 mV) of the core liposomes switched to a positive value after polymer coating (ca. +40 mV). Confocal laser microscopy studies showed comparable mucoadhesive properties of chitosan–aprotinin coated MLV and chitosan coated MLV. In comparison to calcitonin in solution, the area above the blood calcium concentration–time curve (AAC) after oral administration of calcitonin loaded chitosan coated MLV to rats increased around 11-fold, and around 15-fold in the case of calcitonin loaded chitosan–aprotinin coated MLV. Data gained in the current study are believed to contribute to the development of novel polymer-protease inhibitor based delivery systems.     

Enhanced bioavailability of metoclopramide HCl by intranasal administration of a mucoadhesive in situ gel with modulated rheological and mucociliary transport properties

The prolonged residence of drug formulation in the nasal cavity is of utmost importance for intranasal drug delivery. The objective of the present investigation was to develop a mucoadhesive in situ gel with reduced nasal mucociliary clearance in order to improve the bioavailability of the antiemetic drug, metoclopramide hydrochloride (MCP HCl). The in situ gelation upon contact with nasal mucosa was conferred via the use of the thermogelling poloxamer 407 whereas mucoadhesion and drug release enhancement were modulated via the use of mucoadhesive and polyethylene glycol (PEG) polymers respectively. The results revealed that the different mucoadhesives augmented the gel viscosity but reduced its sol–gel transition temperatures (T_sol–gel) and the drug release. The inclusion of PEG counteracted the effect of the mucoadhesive polymers whereby it decreased the gel consistency and increased the T_sol–gel as well as the in vitro drug release. The formulations with favorable sol–gel transition temperatures (25–32 °C) and high in vitro drug release (100% release in 60 min) were also rheologically stable upon storage. The mucoadhesiveness test was performed in vivo in rats, results showed that the carbopol-containing in situ gel prolonged the mucociliary transport time from 10 min (control solution) to 52 min (mucoadhesive gel) and maintained nasal mucosal integrity after 14-days application. The bioavailability study in rabbits revealed that the absolute bioavailability of MCP HCl was significantly increased from 51.7% in case of the oral drug solution to 69.1% in case of the nasal in situ gel. The study point to the potential of mucoadhesive nasal in situ gel in terms of ease of administration, accuracy of dosing, prolonged nasal residence and improved drug bioavailability.