The Effect of Surfactant Type and Concentration on Physicochemical Properties of Carvedilol Solid Dispersions Prepared by Wet Milling Method.

The present study mainly aimed to prepare solid dispersions (SDs) of a poorly water-soluble compound, carvedilol (CA), in the presence of pluronic F68 (F68) and myrj 52 by wet milling technique in order to enhance drug dissolution. The process enabled the preparation of SDs without using any toxic organic solvents. SDs with different CA: surfactant ratios were prepared by wet milling followed by freeze-drying method and evaluated for their particle size and dissolution. They were also characterized based on/using X-ray diffraction (XRD), differential scanning calorimetry (DSC), fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and saturated solubility. The effect of cryoprotectant type on the dissolution and particle size of SDs was also investigated. Wet milling process resulted in the reduced particle size depending on the type of surfactant. The significant drug dissolution and saturated solubility enhancement were recorded for milled SD formulations. In this regard, Myrj had a greater impact compared to F68. Dissolution efficiencies (DE30) obtained for the myrj-included SDs were up to 8.2-fold higher than that of untreated CA. The type of cryoprotectant was also found to affect the drug dissolution. According to the results, partial amorphization occurred in wet-milled samples, as confirmed by XRD and DSC analysis. It was concluded that using an appropriate surfactant along with wet-milling method may have been an effective approach for improving the dissolution rate of CA, a poorly soluble compound.

Particle Size Tailoring of Quercetin Nanosuspensions by Wet Media Milling Technique: A Study on Processing and Formulation Parameters.

Background: A large number of new substances have insufficient biopharmaceutical properties for oral administration caused by their slow dissolution rate and poor solubility. Objective: The purpose of our experiment was to improve the physicochemical properties of a hydrophobic drug, quercetin, by the nanomilling approach. Methods: Quercetin nanosuspensions were prepared using a wet-milling method followed by lyophilization. Stabilizer type and ratio, drug content, milling time, and bead size were identified as critical variables, and their impacts on quercetin particle size were assessed. The optimized nanocrystal was characterized by its morphology, crystallinity, molecular interactions, saturation solubility, and dissolution properties. Results: At optimized process conditions of milling at 500 rpm for 18 cycles of grinding with 0.3 - 0.4 mm zirconium oxide beads, minimum particle size, and PDI values were 281.21 nm and 0.22, respectively. Nanocrystals showed rod-like nanostructures, and XRD scans confirmed a decrease in drug crystallinity. The optimized formulation showed increased solubility and dissolution rate, as well as good physical stability. Conclusions: Particle size reduction by media milling technique was an efficient method for the solubility enhancement of hydrophobic drugs.

The Impact of Process and Formulation Parameters on the Fabrication of Efavirenz Nanosuspension to Improve Drug Solubility and Dissolution.

Background: Efavirenz nanosuspensions (EZ-NSs) were developed by the wet milling method as the most promising top-down nanosizing technique. Different process and formulation parameters were studied and optimized to produce appropriate EZ-NS in suitable conditions to enhance drug dissolution. Methods: In the preliminary studies, various polymeric stabilizers, including Pluronic F68, sodium carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC), and polyvinyl alcohol (PVA), as well as different sizes and weight of milling beads were used to prepare NSs. The effect of sodium lauryl sulfate (SLS) concentration on the NS properties was also evaluated. The influence of other formulation and process parameters, including polymer concentration, milling speed, and milling time, on the particle size and distribution of NSs were investigated using Box-Behnken design. The optimized freeze-dried nanosuspension was characterized by redispersibility, physicochemical properties, and stability. Results: A combination of PVA and SLS was selected as steric and electrostatic stabilizers. The optimum EZ-NS displayed a uniform size distribution with a mean particle size and zeta potential of 254.4 nm and 21.1 mV, respectively. The solidified nanosuspension was well redispersed to the original nanoparticles. Significantly enhanced aqueous solubility (about 11-fold) and accelerated dissolution rate were observed for the optimized formulation. This could be attributed to the reduced particle size and partial amorphization of EZ during the preparation process, studied by X-ray diffraction. Accelerated studies confirmed the stability of the optimum freeze-dried formulation over the examined period of three months. Conclusions: Optimization of different variables led to the formation of EZ-NSs with desired properties through wet milling in a very short time compared to the previous study and therefore reduced production costs. This formulation seems to be a suitable approach for solubility and dissolution enhancement of EZ and may have a great potential to improve the drug's oral bioavailability.

Multilayer Alginate Microcapsules For Live Cell Microencapsulation; Is There Any Preference For Selecting Cationic Polymers?

Since 1980 after introducing the concept of live cell encapsulation by Lim et al., this technology has received enormous attention. Several studies have been conducted to improve this technique; different polymers, either natural or synthetic, have been used as microcapsules` making materials and different substances as coating layers. Literature review leads us to the conclusion that alginate (Alg) multilayer microcapsules and, in particular, alginate-poly l-lysine (PLL)-alginate (APA) are the most used structures for live cell encapsulation. Although, disadvantages of PLL (e.g., weak mechanical strength and low biocompatibility) made researchers work on other cationic polymers to find an alternative. This review aims to discuss more popularly suggested cationic polymers such as poly l-ornithine (PLO), chitosan, etc. As alternatives for PLL and, more importantly, we want to take a closer look to see which one of these systems are closer to clinical applications.

The Impact of Surfactant Composition and Surface Charge of Niosomes on the Oral Absorption of Repaglinide as a BCS II Model Drug.

BACKGROUND: Niosomes, bilayer vesicles formed by the self-assembly of nonionic surfactants, are receiving increasing attention as potential oral drug delivery systems but the impact of niosomal formulation parameters on their oral capability has not been studied systematically. The aim of this study was to investigate the impact of surfactant composition and surface charge of niosomes in enhancing oral bioavailability of repaglinide (REG) as a BCS II model drug. METHODS: Niosomes (13 formulations) from various nonionic surfactants having HLB in the range of 4-28 (Tweens, Spans, Brijs, Myrj, poloxamer 188, TPGS and Labrasol) were prepared and characterized concerning their loading efficiency, hydrodynamic diameter, zeta potential, drug release profile, and stability. The oral pharmacokinetics of the selected formulations were studied in rats (8 in vivo groups). RESULTS: The results revealed that type of surfactant markedly affected the in vitro and in vivo potentials of niosomes. The Cmax and AUC values of REG after administration of the selected niosomes as well as the drug suspension (as control) were in the order of Tween 80> TPGS> Myrj 52> Brij 35> Span 60≈Suspension. Adding stearyl amine as a positive charge-inducing agent to the Tween 80-based niosomes, resulted in an additional increase in drug absorption and values of AUC and Cmax were 3.8- and 4.7-fold higher than the drug suspension, respectively. CONCLUSION: Cationic Tween 80-based niosomes may represent a promising platform to develop oral delivery systems for BCS II drugs.

Comparison of Linear Poly Ethylene Imine (LPEI) and Poly L-Lysine (PLL) in Fabrication of CHOK1 Cell-Loaded Multilayer Alginate Microcapsules.

Purpose: Poly l-lysine (PLL) has been introduced as a strengthening covering layer for alginate microcapsules which are the most convenient way for cell encapsulation. Some disadvantages of PLL such as high price and low biocompatibility have prompted scientists to find better alternatives. Linear poly ethylene imine (LPEI), thanks to its highly similar structure to PLL, could be considered as a proper cost-effective alternative. In this study LPEI and PLL were compared as covering layers of cell-loaded alginate-LPEI-alginate (cALA) and alginate-PLL-alginate (cAPA) microcapsules. Methods: In addition to the physico-mechanical properties, the encapsulation efficiency, cell survival post encapsulation, cell viability, and cellular metabolic activity within the microcapsules were evaluated using trypan blue, live/dead cell staining, and MTT test, respectively. Results: Physico-mechanical evaluation of the microcapsules revealed that the cell microencapsulation process did not affect their shape, size, and mechanical stability. Although the encapsulation efficiency for cALA and cAPA was not different (P >0.05), cell survival post encapsulation was higher in cALA than in cAPA (P<0.05) which could be the reason for the higher cell viability and also cellular metabolic activity within these microcapsules in comparison to cAPA. Conclusion: Here, based on these results, ALA could be introduced as a preferable alternative to APA for cell encapsulation.

Comparison of different cationic polymers efficacy in fabrication of alginate multilayer microcapsules.

In past decades, alginate-based multilayer microcapsules have been given important attention in various pharmaceutical investigations. Alginate-poly l lysine-alginate (APA) is studied the most. Due to the similarity between the structure of polyethyleneimine (PEI) and poly-L-lysine (PLL) and also lower price of PEI than PLL, this study was conducted to compare the efficacy of linear (LPEI) and branch (BPEI) forms of PEI with PLL as covering layers in fabrication of microcapsules. The microcapsules were fabricated using electrostatic bead generator and their shape/size, surface roughness, mechanical strength, and interlayer interactions were also investigated using optical microscopy, AFM, explosion test and FTIR, respectively. Furthermore, cytotoxicity was evaluated by comparing the two anionic final covering layers alginate (Alg) and sodium cellulose sulphate (NCS) using MTT test. BPEI was excluded from the rest of the study due to its less capacity to strengthen the microcapsules and also the aggregation of the resultant alginate-BPEI-alginate microcapsules, while LPEI showed properties similar to PLL. MTT test also showed that NCS has no superiority over Alg as final covering layer. Therefore, it is concluded that, LPEI could be considered as a more cost effective alternative to PLL and a promising subject for future studies.

Preparation and physicochemical characterization of binary and ternary ground mixtures of carvedilol with PVP and SLS aimed to improve the drug dissolution.

The objective of the present study was to enhance the dissolution rate of carvedilol (CA), a poorly water-soluble antihypertensive drug, using a co-grinding method in the presence of polyvinylpyrrolidone (PVP) and sodium lauryl sulfate (SLS). Various ratios of CA:PVP:SLS were ground by a planetary ball mill. They were studied in terms of dissolution, solubility, and particle size. The solid state and morphology of the intact drug and prepared samples were also characterized using differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray diffraction (XRD), and scanning electron microscope (SEM). According to the results, co-grinding in the presence of PVP and SLS significantly increased CA dissolution rate. DE60 (dissolution efficiency) obtained for the best ternary ground mixture (89.31%) was 3.4 and 4.5 times higher than that of the related physical mixture (PM) and the intact drug, respectively. Further, the solubility of this formulation was about 10 times higher compared to that of the intact CA. A direct correlation was also observed between the chamber rotation speed of the planetary mill within the range of 100-400 rpm and CA dissolution rate. Finally, DSC, IR, and XRD analysis ruled out any polymorphic changes and chemical interactions during the grinding process.

An Investigation into the Role of P-Glycoprotein in the Intestinal Absorption of Repaglinide: Assessed by Everted Gut Sac and Caco-2 Cell Line.

The present study aimed at exploring the potential of the P-glycoprotein (P-gp) transporters as a barrier to the repaglinide (REG) epithelial permeability. In-vitro intestinal absorption models, the everted gut sac, and Caco-2 cell line, were used to study the possible role of P-gp in intestinal transport of REG. In the everted gut sacs, apparent permeability coefficients showed cargo concentration dependency transport over the concentration of 40 µM, indicating involvement of a saturable mechanism in REG absorption (Papp were 1.23 × 10 -5 and 3.29 × 10 -5 at drug concentrations of 40 and 100 µM, respectively). Adding verapamil (100 µM), valspodar (5 µM) and ketoconazole (10 µM) significantly enhanced the permeability of REG across mucosal to serosal in the rat jejunum (P < 0.05) suggesting role of CYP 3A4 and/or efflux transporters in oral bioavailability of REG. However, the results of Caco-2 cell experiments indicated low efflux ratios (less than 2) and insignificant involvement of P-gp efflux pumps in REG intestinal transport. Given that Caco-2 cells do not express adequate level of CYP 3A4, the current study suggests that the presystemic metabolism by cytochrome P450 (and not ejection by P-gp) may play a significant role in limiting the oral absorption of REG in small intestine.

Design, Synthesis, Radiolabeling, and Biologic Evaluation of Three 18F-FDG-Radiolabeled Targeting Peptides for the Imaging of Apoptosis.

Background: Early detection of apoptosis is very important for therapy and follow-up treatment in various pathologic conditions. Annexin V interacts strongly and specifically with phosphatidylserine, specific biomarkers of apoptosis with some limitations. Small peptides are suitable alternatives to annexin V. A reliable and noninvasive in vivo technique for the detection of apoptosis is in great demand. Based on our previous studies, three new peptide analogs of LIKKPF (Leu-Ile-Lys-Lys-Pro-Phe) as apoptosis imaging agents were developed. Materials and Methods: Aoa-LIKKP-Cl-F, Aoe-LIKKP-Pyr-F, and Aoe-LIKKP-Nap-F were synthesized, functionalized with aminooxy, and radiolabeled with 18F-FDG. Their biologic properties were evaluated in vitro using apoptotic Jurkat cells. 18F-FDG-Aoe-LIKKP-Pyr-F peptide was injected into normal and apoptotic mice models for biodistribution and in vivo positron emission tomography/computed tomography imaging studies. Results: 18F-FDG-Aoe-LIKKP-Pyr-F peptide showed higher affinity for apoptotic cells. The localization of peptide in apoptotic liver mice was confirmed in biodistribution and imaging studies. Conclusion: The results showed that Aoe-LIKKP-Pyr-F peptide is an auspicious agent for molecular imaging of apoptosis.

Design and In Vitro Evaluation of Eudragit-Based Extended Release Diltiazem Microspheres for Once- and Twice-Daily Administration: The Effect of Coating on Drug Release Behavior.

OBJECTIVES: The aim of this investigation was to develop an extended release formulation of diltiazem hydrochloride (DL) for once- and twice-daily administration, based on Eudragit (Eud) RL and RS microspheres using emulsion solvent evaporation. MATERIALS AND METHODS: Formulations with different drug-polymer concentrations were produced and characterized in terms of yield, encapsulation efficiency (EE), particle size, and surface morphology. The drug release and thermal behavior of the microspheres were also investigated. Selected microspheres were then coated with Eud RS by continuous solvent evaporation, in order to modify the microspheres' properties and burst release. RESULTS: According to the results, the EE was in the range of 56%-93% for uncoated microspheres. The mean particle size of microspheres was different from 470 to above 1000 µm, based on various formulation variables. No difference was observed between the mean size of particles prepared with Eud RL and Eud RS. Microspheres showed sustained release behavior, which was affected by the drug:polymer ratio as well as particle size. Coating the microspheres not only improved the EE values (82%-92%) but also reduced the mean dissolution rate as well as the burst release. CONCLUSION: Microspheres prepared with DL:Eud RL ratios of 1:3 and 1:4 showed release profiles in accordance with the USP criteria for a DL extended release product for dosing every 12 and 24 h, respectively.

Preparation and In-vitro Evaluation of Rifampin-loaded Mesoporous Silica Nanoaggregates by an Experimental Design.

The goal of this research is preparation, optimization and in-vitro evaluation of rifampin-loaded silica nanoparticles in order to use in the pulmonary drug delivery. Nanoparticles are exhaled because of their small size. Preparation of nanoaggregates in a micron-size scale and re-dispersion of them after deposition in the lung is an approach to overcome this problem. We used this approach in our research. Rifampin was selected as a model lipophilic molecule since it was a well-documented and much used anti tuberculosis drug. A half factorial design was used to identify significant parameters of the spray drying process. The results showed that feed concentration, feed pH and the interaction between feed flow rate and gas atomizer flow rate had statistically significant effects on the particle size of nanoaggregates. The Box-Behnken design was employed to optimize the spray drying process. Finally, a quadratic equation which explains the relation between independent variables and aerodynamic diameter of nanoaggregates was obtained. Rifampin-loaded silica nanoaggregates underwent different in-vitro tests including: SEM, Aerosol performance and drug release. The in-vitro drug release was investigated with buffer phosphate (pH=7.4). Regarding the drug release study, a triphasic pattern of release was observed. The rifampin-loaded silica nanoaggregates were capable of releasing 90% drug content after 24 h in combination patterns of release. The prepared rifampin-loaded nanoaggregates seem to have a potential to be used in a pulmonary drug delivery.

The effect of PEG molecular weights on dissolution behavior of simvastatin in solid dispersions.

The purpose of the present study was to investigate the effect of polyethylene glycol (PEG) molecular weights (6000, 12000 and 20000) as solid dispersion (SD) carriers on the dissolution behavior of simvastatin. SDs with various drug : carrier ratios were prepared by solvent method and evaluated for dissolution rate. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), infrared spectroscopy and solubility studies were also performed on the optimum SD formulation. Samples prepared with all three types of PEG showed improved drug dissolution compared to intact drug and corresponding physical mixtures. Meanwhile, the best result was obtained by PEG 12000 with drug : carrier ratio of 1:7 which showed a 3-fold increase in dissolution rate compared to the intact drug. Based on DSC and XRD, no crystalline change occurred during the sample preparation. Solubility studies revealed that increasing the PEG molecular weight resulted in higher phase solubility of drug. In addition, saturated solubility of the optimum SD was significantly higher than that of intact drug and the related physical mixture (24.83, 8.74 and 8.88 µg/mL, respectively) that could be due to the decreased particle size and aggregation. The results confirmed the influence of PEG molecular weight on drug dissolution rate from solid dispersion systems.

Dissolution rate enhancement of clarithromycin using ternary ground mixtures: nanocrystal formation.

Clarithromycin (CLA), a broad-spectrum macrolide, is a poorly soluble drug with dissolution rate limited absorption. The aim of this investigation was to prepare CLA nanoparticles from a ternary ground mixture in the presence of sodium lauryl sulfate (SLS) and polyvinyl pyrrolidone (PVP) as co-grinding water-soluble compounds, in order to improve the drug dissolution rate. Different weight ratios of CLA: SLS: PVP were ground in a dry process by planetary ball mill using different grinding ball size. Following the dissolution rate study, physical properties of the best dissolved co-ground formulation was studied. The accelerated stability studies were also conducted on the co-ground formulation. The results revealed that the dissolution rate of ternary ground mixtures was much higher than that of the intact drug (p < 0.001). Decreasing the grinding ball size and weight with the same rotation speed resulted in particles with decreased dissolution. On the other hand, increasing the PVP concentration in the formulations reduced the drug dissolution. Dissolution efficiencies (DE10 and DE30) for the best dissolved formulation, which consisted of the equal ratio of each co-ground component, were 8.7 and 5 folds higher than the untreated CLA, respectively. This formulation formed nanocrystals with enhanced solubility after dispersing in water. X-ray diffraction, differential scanning calorimetry and infrared spectrophotometry confirmed no chemical interaction and phase transition during the process. Accelerated stability studies confirmed that the co-ground mixture almost remained unchanged in terms of dissolution rate, drug assay and particle size after exposing in stability conditions for three months.

Prolonged release matrix tablet of pyridostigmine bromide: formulation and optimization using statistical methods.

The aim of this study was to design and optimize a prolonged release matrix formulation of pyridostigmine bromide, an effective drug in myasthenia gravis and poisoning with nerve gas, using hydrophilic - hydrophobic polymers via D-optimal experimental design. HPMC and carnauba wax as retarding agents as well as tricalcium phosphate were used in matrix formulation and considered as independent variables. Tablets were prepared by wet granulation technique and the percentage of drug released at 1 (Y(1)), 4 (Y(2)) and 8 (Y(3)) hours were considered as dependent variables (responses) in this investigation. These experimental responses were best fitted for the cubic, cubic and linear models, respectively. The optimal formulation obtained in this study, consisted of 12.8 % HPMC, 24.4 % carnauba wax and 26.7 % tricalcium phosphate, had a suitable prolonged release behavior followed by Higuchi model in which observed and predicted values were very close. The study revealed that D-optimal design could facilitate the optimization of prolonged release matrix tablet containing pyridostigmine bromide. Accelerated stability studies confirmed that the optimized formulation remains unchanged after exposing in stability conditions for six months.

Development and optimization of a sublingual tablet formulation for physostigmine salicylate.

This study is aimed to design and optimize a sublingual tablet formulation of physostigmine salicylate, an effective drug in Alzheimer's disease and nerve gas poisoning, by means of the D-optimal experimental design methodology. Polyvinyl pyrrolidone, lactose, starch 1500 and sodium starch glycolate were used in the formulations as independent variables. Tablets were prepared by the direct compression method and evaluated for their physical properties (tablet hardness, disintegration time and friability), which were regarded as responses in a D-optimal design. Due to the significance of the special cubic model for data fitted, compared to other models, it was used to examine the obtained results. Response surface plots were plotted to study the tablet properties and the optimized overlay plot was generated based on the results and targets considered for the responses. After verification of the optimum checkpoint formulations, an optimized formulation was chosen due to its desirable physical properties and closely observed and predicted values. Drug assay, content uniformity of the dosage unit, drug dissolution and accelerated stability studies were done on the optimum formulation as further experiments. All the obtained results complied with the requirements of a sublingual tablet formulation.