Optimization of the formulation design of chitosan microspheres containing cisplatin

Green Synthesized Chitosan/Chitosan Nanoforms/Nanocomposites for Drug Delivery Applications

Chitosan has become a highlighted polymer, gaining paramount importance and research attention. The fact that this valuable polymer can be extracted from food industry-generated shell waste gives it immense value. Chitosan, owing to its biological and physicochemical properties, has become an attractive option for biomedical applications. This review briefly runs through the various methods involved in the preparation of chitosan and chitosan nanoforms. For the first time, we consolidate the available scattered reports on the various attempts towards greens synthesis of chitosan, chitosan nanomaterials, and chitosan nanocomposites. The drug delivery applications of chitosan and its nanoforms have been reviewed. This review points to the lack of systematic research in the area of green synthesis of chitosan. Researchers have been concentrating more on recovering chitosan from marine shell waste through chemical and synthetic processes that generate toxic wastes, rather than working on eco-friendly green processes-this is projected in this review. This review draws the attention of researchers to turn to novel and innovative green processes. More so, there are scarce reports on the application of green synthesized chitosan nanoforms and nanocomposites towards drug delivery applications. This is another area that deserves research focus. These have been speculated and highlighted as future perspectives in this review.

Optimized preparation of vinpocetine micelles and in vivo evaluation of its pharmacokinetics in rats

This study aimed to develop a novel monomethoxy poly(ethylene glycol)-b-poly(D, L-lactide) (mPEG₅₀₀₀-PLA_10 000) micelle drug delivery system to improve vinpocetine's (VP) dissolution and sustain VP concentrations in plasma. Three micelle fabrication methods were examined to maximize VP loading, followed by structurally characterization and investigation in vitro release and in vivo pharmacokinetics in Sprague-Dawley rats. The thin-film hydration is the most appropriate method of the three methods because of its high loading content. The loaded micelles exhibited a sustained release behavior up to 48 h. Following intraperitoneal administration (9 mg/kg), VP loaded micelles provided significantly higher (335%) AUC (area under concentration-time) compared to VP injection. And also increased the mean residence time [MRT_(0-t)] and elimination half-life (t_1/2z). There were obviously two peaks at 2 h and 9 h in VP loaded micelles concentration-time profile. In summary, these data demonstrated that poly mPEG-PLA micelles can efficiently sustain VP concentrations in plasma for 36 h, thus apprehending polymeric micelles suitability as poor aqueous solubility drug carriers.

Formulation and development of di-dependent microparticulate system for colon-specific drug delivery

Colorectal cancer (CRC) is the third most common cancer globally and the second most common cause of cancer-related deaths. Site-specific delivery of drugs leads to an increase in the availability of drugs at the targeted region. The objective of the present investigation was to develop a dually functional microparticulate colon-targeted drug delivery system of meloxicam for potential application in the prophylaxis of colorectal cancer. Chitosan microspheres were prepared by using emulsification-chemical cross-linking technique. Formulation parameters studied include chitosan concentration, drug to polymer ratio, agitation speed, emulsifier concentration, quantity of cross-linking agent and time for cross-linking. In vitro evaluation of microspheres revealed premature release of drug in the upper part of gastrointestinal tract. Since coating of microspheres is difficult to accomplish (with reproducible results), they were compacted to tablets. Enteric coating of tableted microspheres was achieved using Eudragit® S100. In vitro evaluation and SEM studies depict that the microspheres remain intact during compression process. The developed system was further evaluated for in vivo pharmacokinetic and roentgenography studies. In vivo pharmacokinetic evaluation in rabbits reveal that the onset of drug absorption from the coated tableted microspheres (T _{lag time} = 4.67 ± 0.58 h) was significantly delayed compared to uncoated tableted microspheres. In vivo roentgenographic study revealed that the system remained intact, until it reaches to the colonic region (5 h). Thus, from the results of the study, it can be revealed that the developed system could serve as a potential tool for efficient delivery of drug to the colonic region.

In situ forming biodegradable poly(ε-caprolactone) microsphere systems: a challenge for transarterial embolization therapy. In vitro and preliminary ex vivo studies

BACKGROUND

In situ forming biodegradable poly(ε-caprolactone) (PCL) microspheres (PCL-ISM) system was developed as a novel embolic agent for transarterial embolization (TAE) therapy of hepatocellular carcinoma (HCC). Ibuprofen sodium (Ibu-Na) was loaded on this platform to evaluate its potential for the treatment of post embolization syndrome.

METHODS

The influence of formulation parameters on the size/shape, encapsulation efficiency and drug release was investigated using mixture experimental design. Regression models were derived and used to optimize the formulation for particle size, encapsulation efficiency and drug release profile for TAE therapy. An ex vivo model using isolated rat livers was established to assess the in situ formation of microspheres.

RESULTS

All PCL-ISM components affected the studied properties and fitting indices of the regression models were high (Radj² = 0.810 for size, 0.964 encapsulation efficiency, and 0.993 or 0.971 for drug release at 30 min or 48 h). The optimized composition was: PCL = 4%, NMP = 43.1%, oil = 48.9%, surfactant = 2% and drug = 2%. Ex vivo studies revealed that PCL-ISM was able to form microspheres in the hepatic arterial bed.

CONCLUSIONS

PCL-ISM system provides a novel tool for the treatment of HCC and post-embolization syndrome. It is capable of forming microspheres with desirable size and Ibu-Na release profile after injection into blood vessels.

Preparation, characterization, and potential application of chitosan, chitosan derivatives, and chitosan metal nanoparticles in pharmaceutical drug delivery

Naturally occurring polymers, particularly of the polysaccharide type, have been used pharmaceutically for the delivery of a wide variety of therapeutic agents. Chitosan, the second abundant naturally occurring polysaccharide next to cellulose, is a biocompatible and biodegradable mucoadhesive polymer that has been extensively used in the preparation of micro-as well as nanoparticles. The prepared particles have been exploited as a potential carrier for different therapeutic agents such as peptides, proteins, vaccines, DNA, and drugs for parenteral and nonparenteral administration. Therapeutic agent-loaded chitosan micro- or nanoparticles were found to be more stable, permeable, and bioactive. In this review, we are highlighting the different methods of preparation and characterization of chitosan micro- and nanoparticles, while reviewing the pharmaceutical applications of these particles in drug delivery. Moreover, the roles of chitosan derivatives and chitosan metal nanoparticles in drug delivery have been illustrated.

Biological characterization of folate-decorated biodegradable polymer-platinum(II) complex micelles

A biodegradable and amphiphilic copolymer, poly(ethylene glycol)-block-poly(l-lactide-co-2-methyl-2-carboxyl-propylene carbonate) (mPEG-b-P(LA-co-MCC)), which contains pendant carboxyl groups, was chosen as a drug carrier for the active anticancer part (diaminocyclohexane platinum, DACH-Pt) of oxaliplatin to form mPEG-b-P(LA-co-MCC/Pt) complex. A folic acid-conjugated copolymer, folic acid-poly(ethylene glycol)-block-poly(L-lactide) (FA-PEG-PLA), with similar chemical structure was chosen for targeting. Multifunctional micelles were successfully prepared by a coassembling method. In vitro evaluation was performed by using SKOV-3 and MCF-7 cancer cells. In vivo blood clearance of platinum was studied, and the results show that micelles exhibit longer blood circulation after iv injection. Pt biodistribution was studied by measuring its levels in plasma, organs, and tumors, especially in tumor cell DNA, by atomic absorption and inductively coupled plasma mass spectrometry. Antitumor activity was assessed in mice bearing H22 liver cancers, and the results showed that the micelles with FA moieties exhibited greater antitumor efficacy than those without FA or oxaliplatin. Therefore, these novel multifunctional platinum micelles have great potential in future clinical application.

Lipid emulsion as a drug delivery system for breviscapine: formulation development and optimization

In this study, we developed an optimized formulation of a breviscapine lipid emulsion (BLE) and evaluated the physicochemical properties and in vivo pharmacokinetics of BLE in rats. For the preparation of the lipid emulsion, soybean oil and oleic acid were used as the oil phase, lecithin and poloxamer 188 as surfactants and glycerol as co-surfactant. An optimized formulation consisting of soybean oil (10.0%), oleic acid (0.9%), lecithin (1.5%), poloxamer 188 (0.4%), and glycerol (2.25%) was selected. The results showed that the average particle size, polydispersity index, and zeta potential of the optimized formulation were 183.5 ± 5.5 nm, 0.098 ± 0.046, and -35.0 ± 2.5 mV, respectively. The BLE was stable for at least three month at room temperature. After a single intravenous dose of 4 mg/kg to rats, the AUC of scutellarin from the lipid emulsion was about 1.5-fold higher than that of the commercial product (breviscapine injection). In conclusion, the optimized formulation of BLE showed positive results over the commercial product in terms of the physicochemical properties and pharmacokinetics of BLE in rats.

The influence of physical properties and morphology of crystallised lactose on delivery of salbutamol sulphate from dry powder inhalers

The aim of this work was to investigate the mechanistic evaluation of physicochemical properties of new engineered lactose on aerosolisation performance of salbutamol sulphate (SS) delivered from dry powder inhaler (DPI). Different crystallised lactose particles were obtained from binary mixtures of butanol:acetone. The sieved fractions (63-90 μm) of crystallised lactose were characterised in terms of size, shape, flowability, true density and aerosolisation performance (using multiple twin stage impinger (MSLI), Aerolizer(®) inhaler device, and salbutamol sulphate as a model drug). Compared to commercial lactose, crystallised lactose particles were less elongated, covered with fine lactose particles, and had a rougher surface morphology. The crystallised lactose powders had a considerably lower bulk and tap density and poorer flow when compared to commercial lactose. Engineered carrier with better flow showed improved drug content homogeneity, reduced amounts of drug "deposited" on the inhaler device and throat, and a smaller drug aerodynamic diameter upon inhalation. Aerodynamic diameter of salbutamol sulphate increased as lactose aerodynamic diameter decreased (linear, R(2)=0.9191) and/or as fine particle lactose content increased (linear, R(2)=0.8653). Improved drug aerosolisation performance in the case of crystallised lactose particles was attributed to lower drug-carrier adhesion forces due to a rougher surface and higher fine particle content. In conclusion, this work proved that using binary combinations of solvents in crystallisation medium is vital in modification of the physicochemical and micromeritic properties of carriers to achieve a desirable aerosolisation performance from DPI formulations. Among all lactose samples, lactose particles crystallised from pure butanol generated the highest overall DPI formulations desirability.

Sustained release optimized formulation of anastrozole-loaded chitosan microspheres: in vitro and in vivo evaluation

The purpose of this study was to develop sustained release formulation of anastrozole-loaded chitosan microspheres for treatment of breast cancer. Chitosan microspheres cross-linked with two different cross-linking agents viz, tripolyphosphate (TPP) and glutaraldehyde (GA) were prepared using single emulsion (w/o) method. A reverse phase HPLC method was developed and used for quantification of drug in microspheres and rat plasma. Influence of cross-linking agents on the properties of chitosan microspheres was extensively investigated. Formulations were characterized for encapsulation efficiency (EE), compatibility of drug with excipients, particle size, surface morphology, swelling capacity, erosion and drug release profile in phosphate buffer pH 7.4. EE varied from 30.4 ± 1.2 to 69.2 ± 3.2% and mean particle size distribution ranged from 72.5 ± 0.5 to 157.9 ± 1.5 μm. SEM analysis revealed smooth and spherical nature of microspheres. TPP microspheres exhibited higher swelling capacity, percentage erosion and drug release compared to GA microspheres. Release of anastrozole (ANS) was rapid up to 4 h followed by slow release status. FTIR analysis revealed no chemical interaction between drug and polymer. DSC analysis indicated ANS trapped in the microspheres existed in amorphous form in polymer matrix. The highest correlation coefficients (R (2)) were obtained for Higuchi model, suggesting a diffusion controlled mechanism. There was significant difference in the pharmacokinetic parameters (AUC(0-∞), Kel and t(1/2)) when ANS was formulated in the form of microspheres compared to pure drug. This may be attributed to slow release rate of ANS from chitosan microspheres and was detectable in rat plasma up to 48 h which correlates well with the in vitro release data.

Mucoadhesive chitosan microspheres of carvedilol for nasal administration

The aim of the present study was to develop and characterize chitosan mucoadhesive microspheres of carvedilol (CRV) for nasal delivery to improve bioavailability for treatment of hypertension and angina pectoris. The microspheres were prepared by emulsification-cross-linking method and evaluated for size, shape, entrapment efficiency (EE), in vitro mucoadhesion, in vitro drug release, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The mucoadhesive properties were also evaluated by Freundlich and Langmuir adsorption isotherms. In vivo tests were carried out in rabbits. The microspheres were spherical with size of 20-50 microm, which is favorable for intranasal absorption. The EE was observed from 42% to 68% while percentage mucoadhesion was from 74% to 88%. A strong interaction between mucin and chitosan microspheres was detected explaining adsorption with electrostatic interaction. The microspheres released around 75% of drug in 8 h. DSC and XRD studies revealed that CRV was molecularly dispersed. The absorption rate was rapid and the absolute bioavailability was high, 72.29%. The gamma scintigraphy indicated that the microspheres cleared slowly from the nasal cavity. It was concluded that chitosan microspheres could be used to deliver CRV following nasal administration for improving the bioavailability.

Efficacy of chitosan microspheres for controlled intra-articular delivery of celecoxib in inflamed joints

The use of polymeric carriers in formulations of therapeutic drug delivery systems has gained widespread application, due to their advantage of being biodegradable and biocompatible. In this study, we aimed to prepare celecoxib-loaded chitosan microspheres for intra-articular administration and to compare the retention of the celecoxib solution and chitosan microspheres in the joint cavity. The microspheres were characterized for entrapment efficiency, particle size and surface morphology by scanning electron microscopy. In-vitro drug release studies of microspheres revealed that the microspheres are able to control the release of celecoxib over a period of 96 h. Biodistribution studies of celecoxib and chitosan microspheres were performed by radiolabelling with 99mTc and injecting intra-articularly in rats. The study indicated that following intra-articular administration the distribution of the drug to the organs, like liver and spleen, is very rapid compared with that of the microspheres. Compared with the drug solution, a 10-fold increase in the concentration of the drug in the joint was observed 24 h post intra-articular injection (P < 0.005) when drug was encapsulated in microspheres.

Polymeric drug delivery of platinum-based anticancer agents

Platinum-based anticancer agents such as cisplatin and carboplatin are in widespread clinical use but associated with many side effects. Improving the delivery of cytotoxic platinum compounds may lead to reduced side effects and achieve greater efficacy at lower doses. Polymer-based therapeutics have been investigated as potential drug delivery vehicles for platinum-based drugs. Against a background of the chemistry and pharmacology of cytotoxic platinum compounds, this review discusses the formation and properties of platinum-polymer complexes, dendrimers, micelles, and microparticulates.

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.

Sustained release microspheres of diclofenac sodium using PEGylated rosin derivatives

The PEGylated derivatives of rosin-PD-1 and PD-2 synthesized and characterized earlier (Nande et al., 2006) were investigated as potential materials for sustained release microsphere prepared by emulsion solvent evaporation method using diclofenac sodium (DCS) as model drug. All the microspheres exhibited smooth surfaces intercepted by pores; their sizes (d(90)) ranged between 11-24 microm. The entrapment efficiency (< 80%) of the microspheres increased proportionally with derivative concentration. Presence of solvent like isopropyl alcohol or dichloromethane rendered the microspheres with large sizes but with reduced drug entrapment. Microspheres with small size were obtained at an optimum viscosity of liquid paraffin; any change lead to increase in the particle size. Magnesium stearate was found to be most suitable detackifier in the present system. The drug release was directly related to the particle size--small sized microspheres released drug at a faster rate. The dissolution data complied with Higuchi equation while the mechanism of drug release was Fickian diffusion (n approximately 0.5). Controlled inhibition of edema, as tested by hind paw edema method, was observed for 10 h when the microspheres were administered intraperitoneally. The present study found the derivatives as promising materials for preparing microspheres for sustained delivery of DCS.

Optimized preparation of daidzein-loaded chitosan microspheres and in vivo evaluation after intramuscular injection in rats

A spherical symmetric design-response surface methodology was applied to optimize the preparation of daidzein-loaded chitosan microspheres by the emulsification/chemical cross-linking technique. The influence of polymer concentration, ratio of drug to polymer, and the stirring speed on the encapsulation efficiency, particle size, particle size distribution, and accumulative drug release percent in microspheres were evaluated. Scan electron microscopy of the optimized microspheres showed spherical particles, loading with drug microcrystal uniformly on the surface of and inside the microspheres. In vivo pharmacokinetic characteristics were evaluated after intramuscular injection of the microspheres in rats. The time-resolved fluoroimmunoassay method was used to determine plasma concentrations of daidzein. The data showed that the release of daidzein in the microspheres in vitro and in vivo almost lasted for 35 days. The bioavailability of daidzein in the microspheres by intramuscular injection increased up to 39% in rats, suggesting that the cross-linked chitosan microspheres are a valuable system for the long-term delivery of isoflavones.

Adaptive Neuro-Fuzzy Modeling of Poorly Soluble Drug Formulations

PURPOSE

The purpose of this study was to evaluate the efficiency of a neuro-fuzzy logic-based methodology to model poorly soluble drug formulations and predict the development of the particle size that has been proven to be an important factor for long-term stability.

METHODS

An adaptive neuro-fuzzy inference system was used to model the natural structures within the data and construct a set of fuzzy rules that can subsequently used as a predictive tool. The model was implemented in Matlab 6.5 and trained using 75% of an experimental data set. Subsequently, the model was evaluated and tested using the remaining 25%, and the predicted values of the particle size were compared to the ones from the experimental data. The produced adaptive neuro-fuzzy inference system-based model consisted of four inputs, i.e., acetone, propylene glycol, POE-5 phytosterol (BPS-5), and hydroxypropylmethylcellulose 90SH-50, with four membership functions each. Moreover, 256 fuzzy rules were employed in the model structure.

RESULTS

Model training resulted in a root mean square error of 4.5 x 10(-3), whereas model testing proved its highly predictive efficiency, achieving a correlation coefficient of 0.99 between the actual and the predicted values of the particle size (mean diameter).

CONCLUSIONS

Neuro-fuzzy modeling has been proven to be a realistic and promising tool for predicting the particle size of drug formulations with an easy and fast way, after proper training and testing.

Drug targeting systems for cancer chemotherapy

Tumour specific drug targeting has been a very actively investigated area for over 2 decades. Various approaches have involved the use of drug delivery systems that can localise the anticancer agent at the tumour site without damaging the normal cells. For this purpose, various delivery systems that have been utilised are liposomes, microspheres and recently, nanoparticles. Two liposome formulations containing anticancer drugs for example, adriamycin and daunomycin are already on the market in the USA and Europe. Microspheres are also being investigated for delivering various anticancer drugs and protein/peptides for anticancer treatment, and several formulations are in Phase I/II clinical trials. Antitumour drugs have also been linked to tumour specific monoclonal antibodies via various chemical linkages. Doxorubicin was linked to a chimeric monoclonal antibody that was targeted to the Lewis Y antigen. Though this conjugate initially showed potential, it was recently dropped from Phase II clinical trials. Another approach with monoclonal antibodies has been the use of immunotoxins. Immunotoxins initially showed promise as potential anticancer agents at picomolar concentrations but several clinical and preclinical studies have not shown much promise in this regard. Drug containing liposomes and microspheres have been further linked to tumour specific monoclonal antibodies to enhance their tumour specificity. Most of the studies with immunoliposomes or targeted microspheres have not gone beyond the preclinical studies. New therapeutic approaches are presently emerging based on natural products like cytokines, peptide growth factor antagonists, antisense oligonucleotides and specific genes. These approaches need the help of delivery systems to deliver these complex molecules to tumour cells. One of the current pursued approaches is the use of cationic liposomes. Several clinical studies are undergoing with various cationic liposomes and the next few years will demonstrate the usefulness of this approach. In recent years, the problems in cancer treatment have been complicated with the emergence of resistance strains leading to resistant and cross-resistant tumour cells. Several agents have been used to overcome or reverse drug-resistance in solid tumours and it remains a highly pursued area in cancer treatment.

Celecoxib incorporated chitosan microspheres: in vitro and in vivo evaluation

Recently, considerable interest has been focussed on the use of biodegradable polymers for specialized applications such as controlled release of drug formulations; meanwhile, microsphere drug delivery systems using various kinds of biodegradable polymers have been studied extensively during the past two decades. In the present investigation, it was aimed to prepare microsphere formulations of celecoxib using a natural polymer, chitosan as a carrier for intra-articular administration to extend the retention of the drug in the knee joint. Microsphere formulations were evaluated in vitro for particle size, entrapment efficiency, surface morphology and in vitro drug release. For in vivo studies, (99m)Technetium- labeled glutathione was used as a radiopharmaceutical to demonstrate arthritic lesions by gamma scintigraphy. Evaluation of arthritic lesions post therapy in rats showed a significant difference (P < 0.005) in the group treated with celecoxib solution compared to the group treated with celecoxib loaded chitosan microspheres.

Preparation of arsenic trioxide albumin microspheres and its release characteristics in vitro

Arsenic trioxide albumin microspheres (As2O3-BSA-NS) were prepared by using methods of chemical cross-linking. The desirability function (DF), calculated according to the size (<1 microm) distribution, drug loading and drug trapping efficiency, was introduced as a total index for the microspheres formulation. Four factors, inculding W/O ratio, decentralization speed, BSA concentration and stirring stabilization time, were selected and arranged in an orthogonal experimental table. The release characteristic was studied by the drug release experiment in vitro. The four factors affected DF differently. Decentralization speed behaved as the maximum (P<0.01), followed by BSA concentration (P<0.05) and the W/O ratio dose (P<0.05). Stirring stabilization time did not influence DF (P>0.05). The release experiment in vitro showed that As2O3 in As2O3-BSA-NS was released more slower than pure As2O3. It was concluded that regular As2O3-BSA-NS may be prepared by the methods of chemical cross-linking, which was optimized by orthogonal experimental analysis of different factors, and the microspheres can release As2O3 slowly.

Formulation optimization of water-in-oil-water multiple emulsion for intestinal insulin delivery

Formulation optimization of the water-in-oil-in-water multiple emulsion incorporating insulin was performed based on statistical methods such as the orthogonal experimental design and the response surface evaluation. As model formulations, 16 types of emulsions were prepared according to the orthogonal experimental design. To optimize the formulation, the influence of causal factors such as amounts of gelatin, insulin, oleic acid (OA) and the volume ratio of the outer aqueous phase to total and agitation time of the second emulsification process on individual characteristics of the emulsion, such as inner droplet size, viscosity, stability and pharmacological effect, was evaluated first. Based on the analysis of ANOVA, it was concluded that the droplet size of the emulsion was influenced by the volume ratio of the outer aqueous phase significantly. The viscosity of the emulsion was affected by these causal factors and their interactions; however, the most predominant contribution of all causal factors was the volume ratio of the outer aqueous phase. Similarly, one of the most important characteristics in the design of the formulation, stability, was affected by the causal factors. With regard to the hypoglycemic effect, the most influential factor was the content of OA in the emulsion. By means of a novel optimization technique involving a multivariate spline interpolation (MSI), formulation optimization was performed with respect to pharmacological effect and stability, and the optimum formulation with a desirable pharmacological effect and high stability was successfully estimated.

Chitosan microspheres as a potential carrier for drugs

Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications due to its biocompatibility, high charge density, non-toxicity and mucoadhesion. It has been shown that it not only improves the dissolution of poorly soluble drugs but also exerts a significant effect on fat metabolism in the body. Gel formation can be obtained by interactions of chitosans with low molecular counterions such as polyphosphates, sulphates and crosslinking with glutaraldehyde. This gelling property of chitosan allows a wide range of applications such as coating of pharmaceuticals and food products, gel entrapment of biochemicals, plant embryo, whole cells, microorganism and algae. This review is an insight into the exploitation of the various properties of chitosan to microencapsulate drugs. Various techniques used for preparing chitosan microspheres and evaluation of these microspheres have also been reviewed. This review also includes the factors that affect the entrapment efficiency and release kinetics of drugs from chitosan microspheres.

Development of modified release diltiazem HCl tablets using composite index to identify optimal formulation

This article reports the preparation of tartaric acid treated ispaghula husk powder for the development of modified release tablets of diltiazem HCl by adopting direct compression technique and a 32 full factorial design. The modified ispaghula husk powder showed superior swelling and gelling as compared to untreated powder. Addition of compaction augmenting agent such as dicalcium phosphate was found to be essential for obtaining tablets with adequate crushing strength. In order to improve the crushing strength of diltiazem HCl tablets, to modulate drug release pattern, and to obtain similarity of dissolution profiles in distilled water and simulated gastric fluid (pH 1.2), modified guar gum was used along with modified ispaghula husk powder and tartaric acid. A novel composite index, which considers a positive or a negative deviation from an ideal value, was calculated considering percentage drug release in 60, 300, and 540 min as dependent variables for the selection of a most appropriate batch. Polynomial equation and contour plots are presented. The concept of similarity factor (f2) was used to prove similarity of dissolution in water and simulated gastric fluid (pH 1.2).

Chitosan and sodium alginate-based bioadhesive vaginal tablets

Metronidazole was formulated in mucoadhesive vaginal tablets by directly compressing the natural cationic polymer chitosan, loosely cross-linked with glutaraldehyde, together with sodium alginate with or without microcrystalline cellulose (MCC). Sodium carboxymethylcellulose (CMC) was added to some of the formulations. The drug content in tablets was 20%. Drug dissolution rate studies from tablets were carried out in buffer pH 4.8 and distilled water. Swelling indices and adhesion forces were also measured for all formulations. The formula (FIII) containing 6% chitosan, 24% sodium alginate, 30% sodium CMC, and 20% MCC showed adequate release properties in both media and gave lower values of swelling index compared with the other examined formulations. FIII also proved to have good adhesion properties with minimum applied weights. Moreover, its release properties (% dissolution efficiency, DE) in buffer pH 4.8, as well as release mechanism (n values), were negligibly affected by aging. Thus, this formula may be considered a good candidate for vaginal mucoadhesive dosage forms.

Impregnation and release of aspirin from chitosan/poly(acrylic acid) graft copolymer microspheres

The purpose of this study was to produce aspirin-impregnated microspheres of chitosan/poly(acrylic acid) copolymer in order to evaluate the release characteristics as a function of pH, simulating the fluids in the gastrointestinal tract. Chitosan microspheres were obtained by the coacervation-phase separation method, induced by the addition of a non-solvent (NaOH 2.0 M solution). The microspheres were cross-linked with glutaraldehyde, reduced with sodium cianoborohydride and grafted with poly(acrylic acid). The impregnation of aspirin into chitosan/poly(acrylic acid) copolymer microspheres was achieved by the dissolution of the drug in water:ethanol (2:1), which was adsorbed by the microspheres for 24h at 25 degrees C. The efficiency of aspirin impregnation was high (approximately 94%). The approach employed herein in the production of aspirin-impregnated microspheres using chitosan/poly(acrylic acid) can be a suitable drug-release control system.

Characterization of polyvinylalcohol microspheres of diclofenac sodium: application of statistical design

Microspheres of polyvinylalcohol (PVA) containing diclofenac sodium were prepared by an emulsion-chemical cross-linking method. A statistical design was used to study the variables that affect the preparation of microspheres and to study the release profile of diclofenac from the microspheres. To account for the drug content, a mass balance study of the process was performed. A high concentration of polyvinylalcohol, a high stirring speed, and a low level of glutaraldehyde were found to be important to obtain spherical and discrete microspheres. The concentration of polyvinylalcohol and the amount of heavy liquid paraffin were found to be critical factors in influencing the t50 value. Almost 98% of the total diclofenac sodium added was accounted for in mass balance studies.

Chitosan-gadopentetic acid complex nanoparticles for gadolinium neutron-capture therapy of cancer: preparation by novel emulsion-droplet coalescence technique and characterization

PURPOSE

The gadopentetic acid (Gd-DTPA)-loaded chitosan nanoparticles (Gd-nanoCPs) were prepared for gadolinium neutron-capture therapy (Gd-NCT) and characterized and evaluated as a device for intratumoral (i.t.) injection.

METHODS

Gd-nanoCPs were prepared by a novel emulsion-droplet coalescence technique. The effects of the deacetylation degree of chitosan and Gd-DTPA concentration in chitosan medium on the particle size and the gadolinium content in Gd-nanoCPs were examined. In vitro Gd-DTPA release from Gd-nanoCPs was evaluated using an isotonic phosphate-buffered saline solution (PBS, pH 7.4) and human plasma. In vivo Gd-DTPA retention in the tumor after i.t. injection of Gd-nanoCPs was estimated on mice bearing s.c. B16F10 melanoma.

RESULTS

Gd-nanoCPs with the highest Gd content, which were obtained using 100% deacetylated chitosan in 15% Gd-DTPA aqueous solution, were 452 nm in diameter and 45% in Gd-DTPA content. A lower deacetylation degree of chitosan led to an increase in particle size and a decrease in Gd-DTPA content in Gd-nanoCPs. As Gd-DTPA concentration in the chitosan solution increased, Gd-DTPA content in Gd-nanoCPs increased but the particle size did not vary. Gd-DTPA loaded to Gd-nanoCPs was hardly released over 7 days in PBS (1.8%) despite the high water solubility of Gd-DTPA. In contrast, 91% of Gd-DTPA was released in plasma over 24 hours. When Gd-nanoCPs were i.t. injected, 92% of Gd-DTPA injected effectually without outflow was held in the tumor tissue for 24 hours, which was different from the case of gadopentetate solution injection (only 1.2%).

CONCLUSIONS

Gd-nanoCPs highly incorporating Gd-DTPA were successfully prepared by the emulsion-droplet coalescence technique. Their releasing properties and their ability for long-term retention of Gd-DTPA in the tumor indicated that Gd-nanoCPs might be useful as an i.t. injectable device for Gd-NCT.

Effects of lipo prostaglandin E1 on distribution of cis-diamminedichloroplatinum in lung metastasis derived from Dunn osteosarcoma cell-inoculated mouse foot-pad

This study was designed to determine the effect of lipid microspheres containing prostaglandin E1 (lipo PGE1) on cis-diamminedichloroplatinum (CDDP) accumulation in primary and lung metastatic lesions. Sixty mice were divided into four groups, depending on whether or not an intra-foot-pad injection of Dunn osteosarcoma cells had been administered and on whether or not an intraperitoneal injection of lipo PGE1 had been administered. CDDP was injected intraperitoneally into all the mice 6 weeks after the inoculation. Tumor colonies of spontaneous metastases in the left lung were found in 21 out of 30 tumor-inoculated mice at autopsy. Tissue platinum concentrations in the lungs with metastatic colonies and in the foot-pad tumors were significantly higher in the lipo PGE1-administered mice than in those without treatment. Terminal deoxytransferase-mediated dUTP nick end labeling (TUNEL) assay showed marked localization of dying cells in the lung metastatic lesions of the lipo PGE1-administered mice. The results of this study showed that pretreatment with lipo PGE1 may augment the antitumor effects of CDDP at the tumor site.

Lipid grafts of egg-box complex: a new supramolecular biovector for 5-fluorouracil delivery

An attempt was made to improve the pharmacokinetic behaviour of 5-fluorouracil (5-FU) by incorporating it into lipoprotein imitating synthetic carrier 'supramolecular biovector (SMBV)' which is an important prerequisite for achieving its better therapeutic performance against cancer. The polysaccharide core of SMBVs was prepared by ionotropic gelation technique by cross-linking polyguluronate units in the alginate molecules with calcium ions to form so called 'egg-box structure'. The formulation and process variables were optimized to obtain particles of nanometer size range. Hydrophobization was carried out by fatty-acylation on the surface followed by phospholipid coating. Palmitoyl polyethylene glycol (p-PEG) was anchored to impart stealth behaviour. The scanning electron microscopy showed discrete spheres of average diameter 748 nm. Polydispersity was estimated to be 0.37. Overall zeta potential was -21.3 mV. The drug loading capacity and encapsulation efficiency was found to be 10.0% and 97.9%, respectively. The release from drug solution (AP) followed zero-order kinetics. Higuchi release pattern was obtained for egg-box complex cores (AP1) while first-order pattern was followed for fatty acylated (AP2) and lipid coated cores before (AP3) and after p-PEG anchoring (AP4). The amount of drug liberated in 24 h was in the order AP > AP1 > AP2 > AP4 > AP3. The release pattern obtained was a combined effect of drug diffusion through egg-box matrix as well as partitioning in hydrophobic layer and p-PEG layer around the SMBV. The stability study showed negligible leakage and no appreciable change in particle size upon storage at different temperatures which is an indication of good stability of SMBV formulation. The plasma clearance data revealed increase in circulation half-life of drug and bioavailability. Tissue distribution data obtained was a result of competitive uptake of formulations from tissue macrophages and lymphatics depending upon its surface characteristics and residence period in vascular system. The enhanced delivery of drug to lymphatics and improvement in its half-life render SMBVs useful for control of metastasis and tumour growth.

Artificial neural network as a novel method to optimize pharmaceutical formulations

One of the difficulties in the quantitative approach to designing pharmaceutical formulations is the difficulty in understanding the relationship between causal factors and individual pharmaceutical responses. Another difficulty is desirable formulation for one property is not always desirable for the other characteristics. This is called a multi-objective simultaneous optimization problem. A response surface method (RSM) has proven to be a useful approach for selecting pharmaceutical formulations. However, prediction of pharmaceutical responses based on the second-order polynomial equation commonly used in RSM, is often limited to low levels, resulting in poor estimations of optimal formulations. The aim of this review is to describe the basic concept of the multi-objective simultaneous optimization technique in which an artificial neural network (ANN) is incorporated. ANNs are being increasingly used in pharmaceutical research to predict the non-linear relationship between causal factors and response variables. The usefulness and reliability of this ANN approach is demonstrated by the optimization for ketoprofen hydrogel ointment as a typical numerical example, in comparison with the results obtained with a classical RSM approach.

Chitosan: a unique polysaccharide for drug delivery

The aim of this review is to give an insight into the many potential applications of chitosan as a pharmaceutical drug carrier. The first part of this review concerns the principal uses of chitosan as an excipient in oral formulations (particularly as a direct tableting agent) and as a vehicle for parenteral drug delivery devices. The use of chitosan to manufacture sustained-release systems deliverable by other routes (nasal, ophthalmic, transdermal, and implantable devices) is discussed in the second part.