Release characteristics of a model plasmid DNA encapsulated in biodegradable poly(ethylene glycol fumarate)/acrylamide hydrogel microspheres

Biodegradable hydrogel microspheres were synthesized by free radical suspension copolymerization of poly(ethylene glycol fumarate) macromer with bisacrylamide (PEGF/PAM). The acidic initiator ammonium persulphate in combination with the basic accelerator, N,N,N',N'-tetramethyethylenediamine, were used to form the PEGF/PAM hydrogel at a neutral pH. The equilibrium water content of the microspheres was greater than 90% w/w. A model double stranded plasmid DNA (dsDNA) coding for the enhanced green fluorescence protein (pEGFP) gene was encapsulated in the hydrogel and the effect of loading and water content before swelling on release kinetics was investigated. Fluorescent confocal microscopy demonstrated that the encapsulated dsDNA was in the biologically active double stranded configuration. The highest loading of 0.81 mg ml(-1) resulted in the best encapsulation efficiency of 95%. For that loading, 6% of the dsDNA was released in 25 days at a rate of 16 ng ml(-1). The highest water content of 70% resulted in the highest burst release of 27% and 14% of the dsDNA was released in 25 days at a rate of 30 ng ml(-1). For elucidating the release mechanism, the network mesh size was compared with the radius of gyration (Rg) of the dsDNA plasmid. The mesh size was 7 nm, which was less than Rg of the dsDNA (31 nm) but greater than the chain diameter of 1.1 nm. Since the mesh size was less than Rg, the release mechanism was by reptation of the segments of dsDNA within the tube formed by the network chains between crosslinks. These results indicate that the hydrogel mesh size and the size of the plasmid control the release mechanism.     

Biodegradable alginate microparticles developed by electrohydrodynamic spraying techniques for oral delivery of protein

In this study, alginate microparticles were prepared by cross-linking alginate with calcium chloride solution using an electrohydrodynamic spraying technique. The effects of alginate and calcium chloride concentration as well as electrical potential on particle size and shape were investigated. The results showed that 1 mg ml^?1 alginate medium viscosity (AMV), 2.5 mg ml^?1 CaCl₂, electrical potential 18 kV (F1) and 0.5 mg ml^?1 alginate low viscosity (ALV), 2.5 mg ml^?1 CaCl₂, electrical potential 20 kV (F2) yielded the spherical shape and small particles of 937 ± 158 nm and 1556 ± 51 nm, respectively. In bovine serum albumin (BSA) entrapment efficiency study, initial BSA of 5, 10, 20, 40 and 60% w/w to polymer was incorporated into these alginate microparticles. The results revealed that F2 with initial BSA 10% w/w showed the highest entrapment efficiency of 49.70 ± 0.01%. The result of BSA content revealed that F2'with the initial BSA of 20% w/w showed the highest amount of BSA content of 3.92 ± 0.02 mg g^?1 of particles. F1 and F2 with the initial BSA of 5%, 20% and 40% w/w were chosen to evaluate for the release in PBS pH 7.4. It was found that F1 with the initial BSA of 40% w/w showed the slowest release rate and sustained release. The release of F1 in 0.1 N HCl solution (pH 1.2) was slower than that in pH 7.4. This electrohydrodynamic spray technique (EHDA) can be applied to prepare alginate in micro size and can encapsulate BSA. Alginate microparticles can further be optimized for oral delivery of several pharmaceutical peptides and proteins.     

Comparison of enantioselective disposition of rabeprazole versus lansoprazole in renal-transplant recipients who are CYP2C19 extensive metabolizers

The purpose of this study was to investigate the comparative pharmacokinetics of rabeprazole and lansoprazole enantiomers in renal-transplant recipients on tacrolimus who were CYP2C19 extensive metabolizers. Sixteen Japanese patients were randomly assigned after renal transplantation to receive repeated doses of one of the following two regimens for 28 days; tacrolimus, mycophenolate mofetil and prednisolone together with either 20?mg of racemic rabeprazole (n?=?8) or 30?mg of racemic lansoprazole (n?=?8). The mean C_max and AUC_0–24 of (R)-lansoprazole compared to (S)-lansoprazole in renal transplant recipients were 12-fold (954?±?522 vs. 167?±?137?ng?ml^?1, respectively) and 6.9-fold (4787?±?3454 vs. 451?±?354?ng?h?ml^?1, respectively) greater, and its elimination half-life was 2.1-fold (2.3?±?1.0 vs. 1.2?±?0.6?h, respectively) longer. In contrast, although the elimination half-life of (R)-rabeprazole was significantly longer than that of the (S)-enantiomer (2.1?±?0.5 vs. 1.3?±?0.9?h, respectively; P?C_max between the (R)- and (S)-enantiomer (186?±?40 vs. 200?±?92?ng?ml^?1, respectively). In conclusion, in renal-transplant recipients who are CYP2C19 extensive metabolizers, there is less stereoselective difference in the pharmacokinetic disposition between the (R)- and (S)-enantiomers of rabeprazole than those of lansoprazole.     

Penetration enhancer-containing spanlastics (PECSs) for transdermal delivery of haloperidol: in vitro characterization,ex vivo permeation and in vivo biodistribution studies

Haloperidol (Hal) is one of the widely used antipsychotic drugs. When orally administered, it suffers from low bioavailability due to hepatic first pass metabolism. This study aimed at developing Hal-loaded penetration enhancer-containing spanlastics (PECSs) to increase transdermal permeation of Hal with sustained release. PECSs were successfully prepared using ethanol injection method showing reasonable values of percentage entrapment efficiency, particle size, polydispersity index and zeta potential. The statistical analysis of the ex vivo permeation parameters led to the choice of F1L – made of Span^® 60 and Tween^® 80 at the weight ratio of 4:1 along with 1% w/v Labrasol^® – as the selected formula (SF). SF was formulated into a hydrogel by using 2.5% w/v of HPMC K4M. The hydrogel exhibited good in vitro characteristics. Also, it retained its physical and chemical stability for one month in the refrigerator. The radiolabeling of SF showed a maximum yield by mixing of 100?µl of diluted formula with 50?µl saline having 200 MBq of ^99mTc and containing 13.6?mg of reducing agent (NaBH₄) and volume completed to 300?µl by saline at pH 10 for 10?min as reaction time. The biodistribution study showed that the transdermal ^99mTc-SF hydrogel exhibited a more sustained release pattern and longer circulation duration with pulsatile behavior in the blood and higher brain levels than the oral ^99mTc-SF dispersion. So, transdermal hydrogel of SF may be considered a promising sustained release formula for Hal maintenance therapy with reduced dose size and less frequent administration than oral formula.     

5-Fluorouracil-loaded microspheres prepared by spray-drying poly(D,L-lactide) and poly(lactide-co-glycolide) polymers: Characterization and drug release

5-Fluorouracil (5-FU), a hydrosoluble anti-neoplastic drug, was encapsulated in microspheres of poly(D,L-lactide) (PLA) and poly(lactide-co-glycolide) (PLGA) polymers using the spray-drying technique, in order to obtain small size microspheres with a significant drug entrapment efficiency. Drug-loaded microspheres included between 47?±?11 and 67?±?12?µg 5-FU?mg^?1 microspheres and the percentage of entrapment efficiency was between 52?±?12 and 74?±?13. Microspheres were of small size (average diameter: 0.9?±?0.4–1.4?±?0.8?µm microspheres without drug; 1.1?±?0.5–1.7?±?0.9?µm 5-FU-loaded microspheres) and their surface was smooth and slightly porous, some hollows or deformations were observed in microspheres prepared from polymers with larger T_g. A fractionation process of the raw polymer during the formation of microspheres was observed as an increase of the average molecular weight and also of T_g of the polymer of the microspheres. The presence of 5-FU did not modify the T_g values of the microspheres. Significant interactions between the drug and each one of the polymers did not take place and total release of the included drug was observed in all cases. The time needed for the total drug release (28–129?h) was in the order PLA?>?PLGA 75/25?>?PLGA 50/50. A burst effect (17–20%) was observed during the first hour and then a period of constant release rate (3.52?±?0.82–1.46?±?0.26?µg 5-FU?h^?1 per milligram of microspheres) up to 8 or 13?h, depending on the polymer, was obtained.     

LC-MS-MS analysis of 2-pyridylacetic acid,a major metabolite of betahistine: application to a pharmacokinetic study in healthy volunteers

1.?A sensitive liquid chromatographic-tandem mass spectrometric assay was developed and validated to determine the major metabolite of betahistine, 2-pyridylacetic acid, in human plasma.

2.?The analyte was extracted from plasma samples by liquid–liquid extraction and analysed using liquid chromatography-tandem mass spectrometry with an electrospray ionization interface. The method has a lower limit of quantitation of 1?ng?ml^?1 for a 0.5-ml plasma aliquot. The intra- and interday precision (relative standard deviation), calculated from quality control (QC) samples, was less than 10%. Accuracy as determined from QC samples was within ±7%.

3.?The validated method was successfully applied to a pharmacokinetic study of betahistine in healthy volunteers. After oral administration of a single dose of 24?mg betahistine mesylate to 20 healthy Chinese male volunteers, C_max was 339.4?ng?ml^?1 (range 77.3–776.4?ng?ml^?1). The t_1/2 was 5.2?h (range 2.0^?1?11.4?h). The AUC_0?t obtained was 1153.5?ng?ml^?1?h (range 278.5–3150.8?ng ml^?1?h). The disposition of the metabolite exhibited a marked interindividual variation.

4.?The plasma concentrations of the parent drug were less than 0.5?ng ml^?1, suggesting that it undergoes almost complete first-pass metabolism. The reported two active metabolites were not detected in the plasma of any volunteer. Although there is no evidence that the major metabolite has pharmacological activity, the clinical importance of 2-pyridylacetic acid in humans should be reinvestigated.     

Assessment of the drug loading,in vitro and in vivo release behavior of novel pH-sensitive hydrogel

Context: As a glucocorticoid drug, dexamethasone has good therapeutic effects for ulcerative colitis. pH-sensitive hydrogels could make conventional changes of volume in response with different pH values. Meanwhile, they could load drugs depending on its internal three-dimensional network structure.

Objective: Appropriate methods were used to improve the drug-loading capacity of hydrogel and exploring the colon-targeting character of dexamethasone hydrogel.

Materials and methods: Different solvents (ethanol and 1,2-propanediol) were employed to dissolve dexamethasone as well as hydrogel monomer materials (poly(ethylene glycol) methyl ether (MPEG)–poly(lactide acid)–acryloyl chloride macromonomer, itaconic acid (IA) and MPEG–methacrylate), then mixing them together to prepare hydrogel through the heat-initiated free radical polymerization method. Differential scanning calorimetry and X-ray diffraction methods were used to verify whether dexamethasone was loaded into hydrogels. In vitro drug release behavior and in vivo pharmacokinetic study were also investigated in detail.

Results: Dexamethasone was successfully loaded into hydrogel, and its loading capacity was improved (5?mg/g). Both the in vitro release study and the in vivo pharmacokinetic study showed the good colon-targeting character of the pH-sensitive P(LE–IA–MEG) hydrogel (T_max?=?1.0?h, C_max?=?2.16?µg/ml of dexamethasone; T_max?=?3.9?h, C_max?=?0.43?µg/ml of dexamethasone hydrogel).

Discussion: Dexamethasone could be targeted to the colon site by P(LE–IA–MEG) hydrogel, thereby improving its therapeutic effect and reduce its side effects.

Conclusion: P(LE–IA–MEG) hydrogel might have great potential application in colon-targeted drug delivery systems.     

pH响应纳米载药系统DOX@MIL-101(Fe)-NH2/HA的制备及靶向抗肿瘤作用研究

目的 制备透明质酸(hyaluronan acid，HA)修饰的纳米金属有机框架MIL-101(Fe)-NH₂载药系统，并进行体外抗肿瘤活性评价。方法 采用溶剂热法制备MIL-101(Fe)-NH₂，通过物理吸附法制备HA修饰载阿霉素的DOX@MIL-101(Fe)- NH₂/HA(DMNH)。并利用扫描电子显微镜、X射线衍射仪、氮气吸附-脱附法等对所合成材料及载药系统进行表征。采用透析法考察了载药系统的体外释药行为，并利用激光共聚焦显微镜观察HepG2细胞对其摄取情况。结果 MIL-101(Fe)-NH₂形貌为规则的正八面体，比表面积和粒径分别为1 061.45 m²·g^-1和200 nm。载药后DMNH的尺寸均一，比表面积为205.84 m²·g^-1，粒径为300 nm。MIL-101(Fe)-NH₂的最佳载药率为65.3%，根据药物释放曲线，从装有阿霉素的MIL-101(Fe)-NH₂载药体系(DMN)、DMNH中释放阿霉素显示出时间和pH依赖性。细胞摄取试验结果显示DMNH较其他组别可以运输更多的阿霉素进入HepG2细胞。细胞毒性的结果证实在相同的药物浓度下，DMNH表现出更高的肿瘤细胞杀伤效率。结论 本研究制备的DMNH载药系统结构稳定、载药量和释药效率高，同时具有优异的肿瘤细胞靶向性及pH响应释放特性，在抗肿瘤药物靶向传输方面具有应用前景。     

An electro-conductive fluid as a responsive implant for the controlled stimuli-release of diclofenac sodium

The purpose of this study was to develop an electro-responsive co-polymeric (ERP) implantable gel from polyethylene glycol (PEG), sodium polystyrene sulphonate (NaPss), polyvinyl alcohol (PVA), and diethyl acetomidomalonate (DAA) for electro-liberation of the model drug diclofenac sodium. Various physicochemical and physicomechanical characterization tests were undertaken on the synthesized drug-free gel (ERP G1) and drug-loaded gel (ERP G2). The ability of the gel to release diclofenac sodium following electrical stimulation was evaluated using a galvanostat while Molecular Mechanics (MM) simulations were performed to elucidate the experimental mechanisms. A stable electro-active gel exhibiting superior cycling stability was produced with desirable rheological properties, rigidity (BHN?=?35.4 N?±?0.33 N/mm²; resilience?=?10.91?±?0.11%), thermal properties (T_g?≈?70?°C; T_c?≈?200?°C) and homogeneous morphology. “ON–OFF” pursatile gradual drug release (37–94% from t_{30 min}?t₁₈₀?_min) kinetics was observed upon applying electric stimulation intermittently, indicating that drug release from the gel was electrically controlled. Overall, the galvanometric and MM evaluation ascertained the suitability of the PEG/NaPss/PVA ERP-Gel for application as a subcutaneously injectable drug delivery implant.     

Testosterone solid lipid microparticles for transdermal drug delivery. Formulation and physicochemical characterization

Purpose: The main objective of the study was to formulate and characterize testosterone (TS) solid lipid microparticles (SLM) to be applied as a transdermal delivery system.

Methods: Testosterone SLMs were formulated using an emulsion melt homogenization method. Various types and concentrations of fatty materials, namely glyceryl monostearate (GM), glyceryl distearate (GD), stearic acid (SA) and glyceryl behanate (GB) were used. The formulations contained 2.5 or 5?mg TS?g^?1. Morphology, particle size, entrapment efficiency (EE), rheological properties and thermal behaviour of the prepared SLM were examined. In vitro release characteristics of TS from various prepared SLM were also evaluated over 24?h using a vertical Franz diffusion cell. In addition, the effect of storage and freeze-drying on particle size and release pattern of TS from the selected formulation was evaluated.

Results: The results indicated that the type of lipid affected the morphology and particle size of SLM. A relatively high drug percentage entrapment efficiency ranging from 80.7–95.7% was obtained. Rheological studies showed plastic flow characteristics of the prepared formulations. DSC examination revealed that TS existed in amorphous form in the prepared SLM. Release studies revealed the following rank order of TS permeation through cellophane membrane after application of various formulations: 5% GM?<?5% GD?<?5% SA?<?5% GB?<?2.5% GM?<?2.5% SA?<?10% GD?<?10% GB. The drug permeation through excised abdomen rat skin after application of 10% GB–2.5?mg TS?g^?1 SLM was lower than that permeated through cellophane membrane. Moreover, SLM containing 10% GB–2.5?mg TS?g^?1 stored at 5°C showed good stability as indicated by the release study and particle size analysis. Trehalose showed high potential as a cryoprotectant during freeze drying of the selected SLM formulation.

Conclusions: The developed TS SLM delivery system seemed to be promising as a TS transdermal delivery system.     

Lipid Based nanoformulation of lycopene improves oral delivery: formulation optimization,ex vivo assessment and its efficacy against breast cancer

This study aims at developing an optimised nanostructured lipid carrier (NLC) of lycopene for efficient absorption following oral administration. The optimised formulation showed an average particle size of 121.9?±?3.66?nm, polydispersity index (PDI) 0.370?±?0.97 and zeta potential ?29.0?±?0.83?mV. Encapsulation Efficiency (% EE) and drug loading (% DL) was found to be 84.50%?±?4.38 and 9.54%?±?2.65, respectively. In vitro release studies demonstrated the burst release within 4–9?h followed by sustained release over 48?h. The IC₅₀ value of lycopene extract and optimised NLC for ABTS^+? were found to be 172.37?μg Trolox equivalent and 184.17?μg Trolox equivalent whereas, for DPPH^?, 117.76?μg Trolox equivalent and 143.08?μg Trolox equivalent respectively. Ex vivo studies and MTT assay revealed that the NLC had better permeation and cause sufficiently more cytotoxicity as compared to drug extract due to higher bioavailability and greater penetration.     

Pharmacokinetics and metabolism of (R,R)-methoxyfenoterol in rat

1. (R,R)-fenoterol (Fen), a β₂-adrenoceptor agonist, is under clinical investigation in the treatment of congestive heart disease. The pharmacokinetics and metabolism of the 4-methoxyphenyl derivative of (R,R)-Fen, (R,R)-MFen, have been determined following intravenous and oral administration to the rat and compared with corresponding results obtained with (R,R)-Fen. Results from the study suggest that (R,R)-MFen can offer pharmacokinetic and metabolic advantages in comparison to an earlier (R,R)-Fen.

2. The oral administration revealed that the net exposure of (R,R)-MFen was about three-fold higher than that of (R,R)-Fen (7.2 versus 2.3?min × nmol ml^?1), while intravenous administration proved that the clearance was significantly reduced, 48 versus 146?ml min^?1 kg^?1, the T_1/2 was significantly longer, 152.9 versus 108.9?min, and the area under the curve (AUC) was significantly increased, 300 versus 119?min × nmol ml^?1.

3. (R,R)-MFen was primarily cleared by glucuronidation associated with significant presystemic glucuronidation of the compound. After intravenous and oral administration of (R,R)-MFen, (R,R)-Fen and (R,R)-Fen-G were detected in the urine samples indicating that (R,R)-MFen was O-demethylated and subsequently conjugated to (R,R)-Fen-G. The total (R,R)-Fen and (R,R)-Fen-G as a percentage of the dose after intravenous administration was 3.6%, while after oral administration was 0.3%, indicating that only a small fraction of the drug escaped presystemic glucuronidation and was available for O-demethylation.

4. The glucuronidation pattern was confirmed by the results from in vitro studies where incubation of (R,R)-MFen with rat hepatocytes produced (R,R)-MFen-G, (R,R)-Fen and (R,R)-Fen-G, while incubation with rat intestinal microsomes only resulted in the formation of (R,R)-MFen-G.

     

巴曲酶对急性心肌缺血犬冠脉节段阻力和流量的影响

犬冠状动脉定量狭窄造成急性心肌缺血,观察巴曲酶(batroxobin)对冠脉循环及血流动力学的影响。结果显示,batroxobin可剂量依赖性地增加缺血心脏冠脉血流量,2BU·kg^-1(0.1BU·kg^-1·min^-1)iv后40min,缺血犬冠脉流量比盐水对照组增加12%,此时小冠脉阻力由4.1±0.5降至3.2±0.5mmHg·min·ml^-1,而大冠脉阻力无明显变化;给药后120min,上述作用仍然持续,且冠脉总阻力降低13%,左室压上升及下降最大速率与盐水对照组相比分别增大14%和16%。结果表明,batroXobin在冠脉低灌流状态下仍可降低小冠脉阻力,增加冠脉流量,这可能是其改善缺血犬冠状循环及心脏功能的机理之一。     

Synthesis,physicochemical properties and ocular pharmacokinetics of thermosensitive in situ hydrogels for ganciclovir in cytomegalovirus retinitis treatment

Ganciclovir (GCV) is one of the most widely used antiviral drugs for the treatment of cytomegalovirus (CMV) retinitis. In this context, the aim of this study was to design in situ thermosensitive hydrogels for GCV ocular delivery by intravitreal injection to achieve sustained drug release behavior and improved ocular bioavailability in the treatment of CMV retinitis. A thermosensitive poly-(β-butyrolactone-co-lactic acid)-polyethylene glycol-poly (β-butyrolactone-co-lactic acid) (PBLA-PEG-PBLA) triblock copolymer was synthesized by ring-opening polymerization and characterization. The GCV-loaded PBLA-PEG-PBLA in situ hydrogels (15%, w/w) were then prepared with drug concentration at 2?mg·mL^?1 and the gelation temperatures, rheological properties, in vitro degradation and syringeability of in situ hydrogels for intravitreal injection were also investigated. Membraneless dissolution model was used to explore drug release behavior of PBLA-PEG-PBLA in situ hydrogel. The results indicated that more than 45 and 85% of GCV can be released within 24 and 96?h, respectively, which was verified by a non-Fickian diffusion mechanism. In vivo ocular pharmacokinetics study showed that area under drug-time curve (AUC) and half-life of PBLA-PEG-PBLA in situ hydrogel was higher (AUC was 61.80?μg·mL^?1·h (p?t_1/2 was 10.29?h in aqueous humor; AUC was 1008.66?μg·mL^?1·h (p?t_1/2 was 13.26?h (p?in situ hydrogel is a promising carrier of GCV for intravitreal injection.     

Angiopep-2修饰载神经毒素介孔二氧化硅脂质囊纳米粒的制备及其体内外评价

目的 制备Angiopep-2（ANG）修饰的载神经毒素（neurotoxin,NT）介孔二氧化硅脂质囊纳米粒（mesoporous silica nanoparticles,MSN）（ANG-LP-MSN-NT）,并进行体内外评价。方法 利用改进的Stober法制备介孔二氧化硅纳米粒,然后运用薄膜水化法制备ANG-LP-MSN-NT。考察其形态、粒径、Zeta电位、载药量和包封率;通过小角粉末衍射、氮气吸-脱附法等技术对其进行表征;透析袋法考察其体外释药特性;热板法和醋酸扭体法考察其镇痛效果。结果 制备的MSN比表面积为557 m²·g^-1,孔径和孔容积（V_p）分别为2.94 nm和0.58 cm³·g^-1。ANG-LP-MSN-NT分布均一,无团聚现象,粒径为（123.37±3.76）nm（PDI 0.20±0.02）,Zeta电位为（-16.57±1.59）mV,载药量与包封率分别为（10.75±0.54）%与（91.82±3.12）%。ANG-LP-MSN-NT较MSN-NT体外突释降低,缓释特性明显;药效学实验结果表明ANG-LP-MSN-NT起效快、最大镇痛效应优于其他组别。结论 ANG-LP-MSN-NT解决了二氧化硅易团聚、易突释的问题,且更有利于NT在脑部富集,发挥更好的镇痛效果,该纳米递药系统作为神经毒素载体在镇痛方面具有较好的应用前景。     

Protective effects of Scutellaria lindbergii root extract against oxidative-induced cell and DNA damage in mouse fibroblast-like cells

Context: Scutellaria lindbergii Rech. f. (Lamiaceae) is an Iranian species of Scutellaria which has been shown to exert antimicrobial, antioxidant and cytotoxic effects. Objective: The protective properties of total methanol extract (TME) of S. lindbergii and its fractions (defatted and CH₂Cl₂) were investigated against cytotoxic and genotoxic effects of H₂O₂ in NIH 3T3 cell line as non-malignant cells. Materials and methods: The cells were incubated with different concentrations of S. lindbergii root extracts [TME (15–250?μg ml^?1), defatted fraction (15–500?μg ml^?1) and CH₂Cl₂ fraction (5–40?μg ml^?1)] and toxic concentration of H₂O₂ (200?µM) at 37?°C for 2?h concurrently and Cell viability was quantitated by MTT assay. The antigenotoxic effect of extracts was investigated using comet assay. The cells were incubated with extracts [TME (25–250?μg ml^?1), defatted fraction (25–500?μg ml^?1) and CH₂Cl₂ fraction (5–40?μg ml^?1)] and H₂O₂ (25?µM) at 4?°C for 20?min, then the comet assay was performed. DNA damage was expressed as percentage tail DNA. Results: Total methanol extract of S. lindbergii and its fractions had a significant inhibitory effect on DNA damage. The IC₅₀ values of TME, defatted fraction and CH₂Cl₂ fraction against DNA damage were determined as 48, 138 and 8?μg ml^?1, respectively. Conclusion: S. lindbergii extracts can prevent oxidative DNA damage, which is likely due to its flavonoids and phenolic compounds as antioxidant constituents.     

Novel hydrogel microspheres of chitosan and pluronic F-127 for controlled release of 5-fluorouracil

Hydrogel microspheres of chitosan (CS) and Pluronic F127 (PF-127) were prepared by the emulsion-crosslinking method employing glutaraldehyde (GA) as a crosslinker. 5-Fluorouracil (5-FU), an anticancer drug with good water solubility, was encapsulated into hydrogel microspheres. Various formulations were prepared by varying the ratio of CS and PF-127, % drug loading and amount of GA. Microspheres were characterized by Fourier transform infrared (FTIR) spectroscopy to confirm the absence of chemical interactions between drug, polymer and the crosslinking agent. Scanning electron microscopy (SEM) was performed to study the surface morphology of the microspheres. SEM showed that microspheres have smooth shiny surfaces. Particle size, as measured by laser light scattering technique, gave an average size ranging from 110 to 382?µm. Differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) studies were performed to understand the crystalline nature of the drug after encapsulation into hydrogel microspheres. Encapsulation of the drug up to 86% achieved was measured by UV spectroscopy. Equilibrium swelling experiments were performed in distilled water. Diffusion coefficients (D) of water through microspheres were estimated by an empirical equation. In vitro release studies indicated the dependence of release rate on the extent of crosslinking, drug loading and the amount of PF-127 used to produce the microspheres; slow release was extended up to 24?h. The release data were also fitted to an empirical equation to compute the diffusional exponent (n), which indicated that the release mechanism followed the non-Fickian trend.     

Optimization of prednisolone acetate-loaded chitosan microspheres using a 23 factorial design for preventing restenosis

Prednisolone acetate (PA)-loaded microspheres were prepared by the spray-drying technique using different polymer (1% and 2%) and drug concentrations (10% and 20%). To obtain the optimum formulation, a three-factor two-level (2³) design was employed. The independent variables were polymer molecular weight, polymer concentration, and theoretical drug loading. Responses were the particle size, percentage of encapsulation efficiency, and the t_50% release. The best formulation was prepared with 20% of PA and 1% of chitosan with medium molecular weight showing relative good yield of production (48.0?±?6.7%) and encapsulation efficiency (45.7?±?0.3%), and released the drug at a constant rate in 11 days.     

Preparation,characterization, and antitumor activities of folate-decorated docetaxel-loaded human serum albumin nanoparticles

Abstract

Context: Docetaxel is now a major antitumor drug in clinical use for the treatment of a variety of tumors. The ethanol/Tween 80 solvent required in the formulation to increase the docetaxel solubility is at least partly responsible for the hypersensitivity reaction, decreased uptake by tumor tissue, and increased exposure to other body compartments.

Objective: The present study was aimed at developing hydrosoluble DTX-FA-HSANPs targeting tumor cells and to investigate antitumor activities of the nanoparticles.

Materials and methods: The DTX-HSANPs were prepared using a desolvation technique and the carboxylic groups of NHS-folate were conjugated with the amino groups of the human serum albumin nanoparticles, and studied their size and zeta potential, drug loading efficiency, surface morphology, release properties in vitro, and antitumor activities.

Results: The spherical nanoparticles obtained were negatively charged with a zeta potential of about ?30?mV and characterized around 150?nm with a narrow size distribution. Drug loading efficiency was approximately 17.2%. The folate-decorated nanoparticles targeted a human hepatoma cell line effectively. The in vitro drug release of DTX-FA-HSANPs in the first 96?h corresponded with the following equation: Q?=?18.87851???0.13866t?+?0.21276t^2???0.00704t³?+?0.0000847854t^4???0.00000034991t⁵ (R^2?=?0.98155). Moreover, the in vitro antitumor activities of DTX-FA-HSANPs were close to the activities of the positive control (docetaxel). The in vivo inhibition ratios of DTX-FA-HSANPs and docetaxel were 66.2% and 59.5%, respectively, at a dose of 5?mg/kg.

Discussion and conclusion: In light of the observed antitumor activities, it would be of considerable interest to collect sufficient data for the clinical application of docetaxel-loaded nanoparticles.     

Cytochromes of the P450 2C subfamily are the major enzymes involved in the O-demethylation of verapamil in humans

The calcium channel blocker verapamil [2,8-bis-(3,4-dimethoxyphenyl)-6-methyl-2-isopropyl-6-azaoctanitrile] undergoes extensive biotransformation in man. We have previously demonstrated cytochrome P450 (CYP) 3A4 and 1A2 to be the enzymes responsible for verapamil N-dealkylation (formation of D-617 [2-(3,4-dimethoxyphenyl)-5-methylamino-2-isopropylvaleronitrile]), and verapamil N-demethylation (formation of norverapamil [2,8-bis(3,4-dimethoxyphenyl)-2-isopropyl-6-azaoctanitrile]), while there was no involvement of CYP3A4 and CYP1A2 in the third initial metabolic step of verapamil, which is verapamil O-demethylation. This pathway yields formation of D-703 [2-(4-hydroxy-3-methoxyphenyl)-8-(3,4-dimethoxyphenyl)-6-methyl-2-isopropyl-6-azaoctanitrile] and D-702 [2-(3,4-dimethoxyphenyl)-8-(4-hydroxy-3-methoxyphenyl)6-methyl-2-isopropyl-6-azaoctanitrile]. The enzymes catalyzing verapamil O-demethylation have not been characterized so far. We have therefore identified and characterized the enzymes involved in verapamil O-demethylation in humans by using the following in vitro approaches: (I) characterization of O-demethylation kinetics in the presence of the microsomal fraction of human liver, (II) inhibition of verapamil O-demethylation by specific antibodies and selective inhibitors and (111) investigation of metabolite formation in microsomes obtained from yeast strain Saccharomyces cerevisiae W(R), that was genetically engineered for stable expression of human CYP2C8, 2C9 and 2C18.In human liver microsomes (n=4), the intrinsic clearance (CL_int), as derived from the ratio of V _max/K_m, was significantly higher for O-demethylation to D-703 compared to formation of D-702 following incubation with racemic verapamil (13.9±1.0 vs 2.4±0.6 ml^*min^{-1 *}g^-1 mean±SD; p<0.05), S-Verapamil (16.8±3.3 vs 2.2±1.2 ml^* mini^*g^-1, p<0.05) and R-verapamil (12.1±2.9 vs 3.6 ±1.3 ml^*min^{-1 *} g^-1; p<0.05), thus indicating regioselectivity of verapamil O-demethylation process. The CL_int of D-703 formation in human liver microsomes showed a modest but significant degree of stereo selectivity (p<0.05) with a S/R-ratio of 1.41±0.17. Anti-LKM2 (anti-liver/kidney microsome) autoantibodies (which inhibit CYP2C9 and 2C19) and sulfaphenazole (a specific CYP2C9 inhibitor) reduced the maximum rate of formation of D-703 by 81.5±4.5% and 45%, that of D-702 by 52.7±7.5% and 72.5%, respectively. Both D-703 and D-702 were formed by stably expressed CYP2C9 and CYP2C18, whereas incubation with CYP2C8 selectively yielded D-703.In conclusion, our results show that enzymes of the CYP2C subfamily are mainly involved in verapamil O-demethylation. Verapamil therefore has the potential to interact with other drugs which inhibit or induce these enzymes.