Gemcitabine hydrochloride microspheres used for intravesical treatment of superficial bladder cancer: a comprehensive in vitro/ex vivo/in vivo evaluation.

INTRODUCTION: Bladder cancer is responsible for more than 130,000 deaths annually worldwide. Intravesical delivery of chemotherapeutic agents provides effective drug localization to the target area to reduce toxicity and increase efficacy. This study aimed to develop an intravesical delivery system of gemcitabine HCl (Gem-HCl) to provide a sustained-release profile, to prolong residence time, and to enhance its efficiency in the treatment of bladder cancer. MATERIALS AND METHODS: For this purpose, bioadhesive microspheres were successfully prepared with average particle size, encapsulation efficiency, and loading capacity of 98.4 µm, 82.657%±5.817%, and 12.501±0.881 mg, respectively. For intravesical administration, bioadhesive microspheres were dispersed in mucoadhesive chitosan or in situ poloxamer gels and characterized in terms of gelation temperature, viscosity, mechanical, syringeability, and bioadhesive and rheological properties. The cytotoxic effects of Gem-HCl solution, Gem-HCl microspheres, and Gem-HCl microsphere-loaded gel formulations were evaluated in two different bladder cancer cell lines: T24 (ATCC HTB4TM) and RT4 (ATCC HTB2TM). RESULTS: According to cell-culture studies, Gem-HCl microsphere-loaded poloxamer gel was more cytotoxic than Gem-HCl microsphere-loaded chitosan gel. Antitumor efficacy of newly developed formulations were investigated by in vivo studies using bladder-tumor-induced rats. CONCLUSION: According to in vivo studies, Gem-HCl microsphere-loaded poloxamer gel was found to be an effective and promising alternative for current intravesical delivery-system therapies.

Mucoadhesive in situ gel formulation for vaginal delivery of clotrimazole: formulation, preparation, and in vitro/in vivo evaluation.

The purpose of this study was to develop a suitable mucoadhesive in situ gel formulation of clotrimazole (CLO) for the treatment of vaginal candidiasis. For this aim, the mixture of poloxamer (PLX) 407 and 188 were used to prepare in situ gels. Hydroxypropyl methylcellulose (HPMC) K100M or E50 was added to in situ gels in 0.5% ratio to improve the mucoadhesive and mechanical properties of formulations and to prolong the residence time in vaginal cavity. After the preparation of mucoadhesive in situ gels; gelation temperature/time, viscosity, mechanical, mucoadhesive, syringeability, spreadibility and rheological properties, in vitro release behavior, and anticandidal activities were determined. Moreover vaginal retention of mucoadhesive in situ gels was investigated with in vivo distribution studies in rats. Based on the obtained results, it was found that gels prepared with 20% PLX 407, 10% PLX 188 and 0.5% HPMC K100M/E50 might be suitable for vaginal administration of CLO. In addition, the results of in vivo distribution studies showed that gel formulations remained on the vaginal mucosa even 24 h after application. In conclusion, the mucoadhesive in situ gels of CLO would be alternative candidate for treatment of vaginal candidiasis since it has suitable gel properties with good vaginal retention.

Design and evaluation of an intravesical delivery system for superficial bladder cancer: preparation of gemcitabine HCl-loaded chitosan-thioglycolic acid nanoparticles and comparison of chitosan/poloxamer gels as carriers.

This study aimed to develop an intravesical delivery system of gemcitabine HCl for superficial bladder cancer in order to provide a controlled release profile, to prolong the residence time, and to avoid drug elimination via urination. For this aim, bioadhesive nanoparticles were prepared with thiolated chitosan (chitosan-thioglycolic acid conjugate) and were dispersed in bioadhesive chitosan gel or in an in situ gelling poloxamer formulation in order to improve intravesical residence time. In addition, nanoparticle-loaded gels were diluted with artificial urine to mimic in vivo conditions in the bladder and were characterized regarding changes in gel structure. The obtained results showed that chitosanthioglycolic acid nanoparticles with a mean diameter of 174.5±3.762 nm and zeta potential of 32.100±0.575 mV were successfully developed via ionotropic gelation and that the encapsulation efficiency of gemcitabine HCl was nearly 20%. In vitro/ex vivo characterization studies demonstrated that both nanoparticles and nanoparticle-loaded chitosan and poloxamer gels might be alternative carriers for intravesical administration of gemcitabine HCl, prolonging its residence time in the bladder and hence improving treatment efficacy. However, when the gel formulations were diluted with artificial urine, poloxamer gels lost their in situ gelling properties at body temperature, which is in conflict with the aimed formulation property. Therefore, 2% chitosan gel formulation was found to be a more promising carrier system for intravesical administration of nanoparticles.

Assessment of Aprotinin Loaded Microemulsion Formulations for Parenteral Drug Delivery: Preparation, Characterization, in vitro Release and Cytotoxicity Studies.

The object of the current study was to prepare novel microemulsion formulations of aprotinin for parenteral delivery and to compare in vitro characteristics and release behaviour of different Technetium-99m ((99m)Tc)-Aprotinin loaded microemulsion formulations. In addition, cytotoxicity of microemulsion formulation was evaluated with cell culture studies on human immortalized pancreatic duct epithelial-like cells. For this aim, firstly, pseudo-ternary phase diagrams were plotted to detect the formulation region and optimal microemulsions were characterized for their thermodynamic stability, conductivity, particle size, zeta potential, viscosity, pH and in vitro release properties. For in vitro release studies aprotinin was labelled with (99m)Tc and labelling efficiency, radiochemical purity and stability of the radiolabeled complex were determined by several chromatography techniques. Radiolabeling efficiency of (99m)Tc-Aprotinin was found over than 90% without any significant changes up to 6 hours after labelling at room temperature. After that, in vitro release studies of (99m)Tc-Aprotinin loaded microemulsions were performed with two different methods; dissolution from diffusion cells and dialysis bags. Both methods showed that release rate of (99m)Tc- Aprotinin from microemulsion could be controlled by microemulsion formulations. Drug release from the optimized microemulsion formulations was found lower compared to drug solution at the end of six hours. According to stability studies, the optimized formulation was found to be stable over a period of 12 months. Also, human immortalized pancreatic duct epithelial-like cells were used to evaluate the cytotoxicity of optimum formulation. Developed microemulsion did not reveal cytotoxicity. In conclusion the present study indicated that the M1-APT microemulsion is appropriate for intravenous application of aprotinin.

Evaluation of chitosan based vaginal bioadhesive gel formulations for antifungal drugs.

The aim of the present study was to evaluate chitosan as a vaginal mucoadhesive gel base for econazole nitrate and miconazole nitrate. To this aim, different types of chitosan with different molecular masses and viscosity properties [low molecular mass chitosan (viscosity: 20,000 mPa s), medium molecular mass chitosan (viscosity: 200,000 mPa s), high molecular mass chitosan (viscosity: 800,000 mPa s)] have been used. First, rheological studies were conducted on chitosan gels. Mechanical, syringeability and mucoadhesive properties of chitosan gels were determined. Release profiles of econazole nitrate and miconazole nitrate from chitosan gels were obtained and evaluated kinetically. In addition, anticandidal activities of formulations were determined. Finally, vaginal retention of chitosan gels in rats was evaluated by in vivo distribution studies. Based on the results, it can be concluded that gels prepared with medium molecular mass chitosan might be effectively used for different antifungal agents in the treatment of vaginal candidiosis, since it has high mucoadhesiveness, suitable mechanical and release properties with good vaginal retention.

In-situ gel formulations of econazole nitrate: preparation and in-vitro and in-vivo evaluation.

OBJECTIVES: This study describes the in-situ gelling of econazole nitrate containing thermosensitive polymers composed of poloxamer 407 and 188 as a novel treatment platform for vaginal candidiasis. METHODS: Aqueous thermosensitive formulations containing 1% of econazole nitrate and poloxamer 407 and/or 188 were prepared and their rheological, mechanical and drug-release properties determined at 20 ± 0.1°C and/or 37 ± 0.1°C. Based on their biologically suitable thermorheological properties, formulations containing the mixtures of poloxamer 407 and 188 in ratios of 15:15 (F1), 15:20 (F2) and 20:10 (F3) were chosen for comprehensive analysis. KEY FINDINGS: Formulations based on F3 exhibited typical gel-type mechanical spectra (G' > G″) at 37°C whereas formulations based on F1 and F2 exhibited properties akin to weakly cross-linked gels. Texture profile analysis demonstrated that F3 showed the highest cohesiveness, adhesiveness, hardness and compressibility. No statistically significant differences (P > 0.5) were observed in the release of econazole nitrate from the formulations at pH 4.5, which in all cases followed anomalous diffusion kinetics. Formulations based on 20% poloxamer 407:10% poloxamer 188 were chosen for in-vivo studies and were shown to be effective for the treatment of the vaginal candidiasis. Histopathologic evaluation also supported the effectiveness of the thermosensitive formulation administered intravaginally. CONCLUSION: By careful engineering of the rheological properties, in-situ thermosensitive gel formulations of econazole nitrate were prepared and were shown to be efficacious in the treatment of vaginal candidiasis.

A comprehensive in vitro and in vivo evaluation of thiolated matrix tablets as a gastroretentive delivery system.

The aim of this study was to investigate the potential of thiolated matrix tablets for gastroretentive delivery systems. Poly(acrylic acid)-cysteine (PAA-Cys) and chitosan-4-thiobuthylamidine (chitosan-TBA) were evaluated as anionic and cationic thiolated polymers and riboflavin was used as a model drug. Tablets were prepared by direct compression and each formulation was characterized in terms of disintegration, swelling, mucoadhesion, and drug release properties. Thereafter, the gastric residence times of tablets were determined with in vivo study in rats. The resulting PAA-Cys and chitosan-TBA conjugates displayed 172.80 ± 30.33 and 371.11 ± 72.74 µmol free thiol groups, respectively. Disintegration studies demonstrated the stability of thiolated tablets up to 24 h, whereas tablets prepared with unmodified PAA and chitosan disintegrated within a time period of 1 h. Mucoadhesion studies showed that mucoadhesion work of PAA-Cys and chitosan-TBA tablets were 1.341- and 2.139-times higher than unmodified ones. The mucoadhesion times of PAA, PAA-Cys, chitosan, and chitosan-TBA tablets were 1.5 ± 0.5, 21 ± 1, 1 ± 0.5, 17 ± 1 h, respectively. These results confirm the theory that thiol groups react with mucin glycoproteins and form covalent bonds to the mucus layer. Release studies indicated that a controlled release was provided with thiolated tablets up to 24 h. These promising in vitro results of thiolated tablets were proved with in vivo studies. The thiolated tablets showed a gastroretention time up to 6 h, whereas unmodified tablets completely disintegrated within 1 h in rat stomach. Consequently, the study suggests that thiolated matrix tablets might be promising formulations for gastroretentive delivery systems.

Rheological and mechanical properties of poloxamer mixtures as a mucoadhesive gel base.

This study described the thermosensitive formulations composed of poloxamer mixtures for use as drug delivery platform via mucosal route. It also characterized the poloxamer mixtures' rheological, mechanical and mucoadhesive properties. Poloxamer (Plx) 407 and Plx 188 were used alone and together for preparing the mucosal drug delivery platform. The mixtures of Plx 407 and Plx 188 in ratio of 15:15 (F5); 15:20 (F6); 20:10 (F7) existed liquid at room temperature, but gelled at physiological temperature. Flow rheometry studies and oscillatory analysis of each formulation were performed at 20 ± 0.1°C and 37 ± 0.1°C. F5 and F7 formulations exhibited typical gel-type mechanical spectra (G' > G″) after the determined frequency value at 37°C whereas F6 behaved as weakly cross-linked gel. Texture profile analysis presented that F5 and F7 showed similar mechanical properties and can be used as base for mucosal dosage form. Mucoadhesion studies indicated the difference among the formulations and the effect of the mucosal surface on mucoadhesive properties. Mucin disc, bovine vaginal and buccal mucosa were used as mucosal platform for mucoadhesion studies. It is suggested that these investigations may be usefully combined to provide a more rational basis for selecting the ratio of Plx to prepare a topical thermosensitive drug delivery system for mucosal administration.

Gastroretentive particles formulated with thiomers: development and in vitro evaluation.

The objective of this study is to develop and evaluate gastroretentive particulate delivery systems using Riboflavin-5'-monophosphate sodium salt dihydrate (RF5'PNa) as model drug. Poly(acrylic acid)-cysteine and chitosan-4-thiobuthylamidine were evaluated and compared as anionic and cationic polymers for gastroretentive particles. Permeation studies were performed with freshly excised stomach mucosa from rats. Polymers and combination with glutathione were evaluated for permeation enhancing properties. Furthermore, particles were prepared by air jet milling and characterized. Permeation studies showed that the apparent permeability coefficients for RF5'PNa with thiomers and glutathione are 1.511-fold and 2.354-fold higher than control, respectively. It can be seen from the results glutathione in combination with thiomers has a significant influence for increasing permeation. Poly(acrylic acid)-cysteine and chitosan-4-thiobuthylamidine particles demonstrated a mean diameter of 336.5 +/- 16.5 and 396.3 +/- 17.0 nm and zeta potential of -19.98 +/- 1.015 and 27.15 +/- 0.500 mV, respectively. The drug loading of Poly(acrylic acid) particles was significantly higher than chitosan particles. The release rate of RF5'PNa from the thiolated particles was slower compared with unmodified particles. Moreover, thiolated particles showed higher mucoadhesive properties compared to unmodified particles. Overall, thiolated particles of both anionic and cationic polymers had improved mucoadhesive and controlled release properties. Therefore, they could be promising for gastroretentive delivery systems.

Strategies to prolong the intravaginal residence time of drug delivery systems.

The vagina has been studied as a favorable site for local and systemic delivery of drugs for female-related conditions. There are a large number of vaginal medications on the market and most of them require frequent application due to their short vaginal residence time. A prolonged vaginal residence time of formulations is therefore a key parameter for improved therapeutic efficacy. Promising approaches to prolong the residence time base on mucoadhesion, in- situ sol-gel transition and mechanical fixation. Mucoadhesive drug delivery systems can be tailored to adhere to the vaginal tissue. In-situ gelling systems offer the advantage of increased viscosity in vaginal cavity and consequently reduce outflow from the vagina. Mechanical fixation needs specially shaped drug delivery systems and reduce the frequency of administration significantly. Within this review an overview on these different strategies and systems is provided. Furthermore, the techniques to evaluate the potential of these systems for prolonged vaginal residence time are described.