Preparation and characterization of oxybenzone-loaded gelatin microspheres for enhancement of sunscreening efficacy

The objective of our present study was to prepare and evaluate gelatin microspheres of oxybenzone to enhance its sunscreening efficacy. The gelatin microspheres of oxybenzone were prepared by emulsion method. Process parameters were analyzed to optimize the formulation. The in vitro drug release study was performed in pH 7.4 using cellulose acetate membrane. Microspheres prepared using oxybenzone:gelatin ratio of 1:6 showed slowest drug release and those prepared with oxybenzone:gelatin ratio of 1:2 showed fastest drug release. The gelatin microspheres of oxybenzone were incorporated in aloe vera gel. Sun exposure method using sodium nitroprusside solution was used for in vitro sunscreen efficacy testing. The formulation C₅ containing oxybenzone-bearing gelatin microspheres in aloe vera gel showed best sunscreen efficacy. The formulations were evaluated for skin irritation test in human volunteers, sun protection factor, and minimum erythema dose in albino rats. These studies revealed that the incorporation of sunscreening agent-loaded microspheres into aloe vera gel greatly increased the efficacy of sunscreen formulation more than four times.     

Microsphere based improved sunscreen formulation of ethylhexyl methoxycinnamate

Polymethylmethacrylate (PMMA) microspheres of ethylhexyl methoxycinnamate (EHM) were prepared by emulsion solvent evaporation method to improve its photostability and effectiveness as sunscreening agent. Process parameters like stirring speed and aqueous polyvinyl alcohol (PVA) concentration were analyzed in order to optimize the formulations. Shape and surface morphology of the microspheres were examined using scanning electron microscopy. Particle size of the microspheres was determined using laser diffraction particle size analyzer. The PMMA microspheres of EHM were incorporated in water-removable cream base. The in vitro drug release of EHM in pH 7.4 was performed using dialysis membrane. Thin layer chromatography was performed to determine photostability of EHM inside the microspheres. The formulations were evaluated for sun protection factor (SPF) and minimum erythema dose (MED) in albino rats. Cream base formulation containing microspheres prepared using EHM:PMMA in ratio of 1:3 (C(3)) showed slowest drug (EHM) release and those prepared with EHM: PMMA in ratio of 1:1 showed fastest release. The cream base formulations containing EHM loaded microspheres had shown better SPF (more than 16.0) as compared to formulation C(d) that contained 3% free EHM as sunscreen agent and showed SPF 4.66. These studies revealed that the incorporation of EHM loaded PMMA microspheres into cream base had greatly increased the efficacy of sunscreen formulation approximately four times. Further, photostability was also shown to be improved in PMMA microspheres.     

Development and in vitro evaluations of gelatin A microspheres of ketorolac tromethamine for intranasal administration

Gelatin A microspheres (MS) of ketorolac tromethamine (KT) for intranasal systemic delivery were developed with the aim to avoid gastro-intestinal complications, to improve patient compliance, to use as an alternative therapy to conventional dosage forms, to achieve controlled blood level profiles, and to obtain improved therapeutic efficacy in the treatment of postoperative pain and migraine. Gelatin A microspheres were prepared using the emulsification-crosslinking technique. The drug was dispersed in polymer gelatin and formulated into a w/o emulsion with liquid paraffin, using glutaraldehyde as a crosslinking agent. The formulation variables were drug loading and the concentrations of polymer (gelatin), co-polymer (chitosan) and the crosslinking agent. All the prepared microspheres were evaluated for physical characteristics, such as particle size, incorporation efficiency, swelling ability, in vitro bioadhesion on rabbit small intestine and in vitro drug release characteristics in pH 6.6 phosphate buffer. All the microspheres showed good bioadhesive properties. Gelatin A and chitosan concentrations, percentage of the crosslinking agent and also the drug loading affected significantly the rate and extent of drug release. The data indicated that the KT release followed Higuchi's matrix model.     

Formulation of wax oxybenzone microparticles using a factorial approach

Oxybenzone wax microparticles (MPs) were prepared by the hydrophobic congealable disperse phase method. The formulation of oxybenzone-loaded MPs was optimized using a 2⁴ experimental design. Factorial analysis indicated that the main MP characteristics were influenced by initial drug loading, emulsification speed, emulsifier concentration and hydrophilic-lipophilic balance. MPs were spherical with 50.5–88.1 µm size range, 17.8–38.9 drug content in mg/100 mg MPs and 33.1–87.2% oxybenzone release in 1 h. A wide range of sunscreen delivery systems suitable for different formulation purposes were generated which may contribute to the advanced formulation of sunscreen products with improved performance.     

Preparation of gelatin microspheres containing lactic acid--effect of cross-linking on drug release

In this study, gelatin microspheres containing lactic acid were prepared by the polymerization technique using glutaraldehyde as the cross-linking agent. Dried microspheres were loaded by immersing them in an aqueous solution of lactic acid. In order to prepare microspheres with an appropriate drug release profile, the effect of time of cross-linking and the amount of cross-linking agent on the swelling properties of microspheres and their release profile were investigated. The microencapsulation efficiency, microspheres appearance, particle size, swelling ratio and drug release profile were also studied. Microspheres prepared with a larger amount of cross-linking agent, or after longer cross-linking time, showed a reduced swelling ratio in aqueous media. In vitro release pattern of lactic acid from gelatin microspheres showed a biphasic profile and the release rates were reduced upon increasing the amount of cross-liking agent and prolonging the cross-linking time.     

Controlled release of nifedipine from gelatin microspheres and microcapsules: in vitro kinetics and pharmacokinetics in man

Nifedipine was embedded in a gelatin matrix to develop a prolonged release dosage form. The effects of polymer/drug ratio, size of the beads, cross-linking with formaldehyde and ethylcellulose coating of the gelatin microspheres on the in vitro release rate of the drug were investigated. The data were analysed according to different laws that can govern the release mechanism: first-order, Higuchi square root of time, spherical matrix and zero-order. The in vitro release kinetics of nifedipine from gelatin microspheres were mainly first-order; from formaldehyde hardened gelatin microspheres, complied with the diffusion model for a spherical matrix, and from ethylcellulose-coated gelatin microspheres, obeyed zero-order kinetics. These findings suggest the possibility of modifying the formulation in order to obtain the desired controlled release of the drug for a convenient oral sustained delivery system. The pharmacokinetic parameters of nifedipine, after administration of a single oral dose of nifedipine-loaded hardened gelatin microspheres to volunteers, suggest that the preparation can be considered as a sustained release delivery system for nifedipine.     

Formulation factors in preparing BTM-chitosan microspheres by spray drying method

Chitosan (CTS) microspheres were prepared by a spray drying method using type-A gelatin and ethylene oxide-propylene oxide block copolymer as modifiers. Surface morphological characteristics and surface charges of prepared microspheres were investigated by using scanning electron microscopy (SEM) and microelectrophoresis. The particle shape, size and surface morphology of microspheres were significantly affected by the concentration of gelatin. Betamethasone disodium phosphate (BTM)-loaded microspheres demonstrated good drug stability (less 1% hydrolysis product), high entrapped efficiency (95%) and positive surface charge (37.5 mV). The in vitro drug release from the microspheres was related to gelatin content. Microspheres containing gelatin/CTS 0.4 approximately 0.6(w/w) had a prolong release pattern for 12 h. These formulation factors were correlated to particulate characteristics for optimizing BTM microspheres in pulmonary delivery.     

Anti-inflammatory effects of aloe vera gel in human colorectal mucosa in vitro

BACKGROUND: Oral aloe vera gel is widely used by patients with inflammatory bowel disease and is under therapeutic evaluation for this condition. AIM: To assess the effects of aloe vera in vitro on the production of reactive oxygen metabolites, eicosanoids and interleukin-8, all of which may be pathogenic in inflammatory bowel disease. METHODS: The anti-oxidant activity of aloe vera was assessed in two cell-free, radical-generating systems and by the chemiluminescence of incubated colorectal mucosal biopsies. Eicosanoid production by biopsies and interleukin-8 release by CaCo2 epithelial cells in the presence of aloe vera were measured by enzyme-linked immunosorbent assay. RESULTS: Aloe vera gel had a dose-dependent inhibitory effect on reactive oxygen metabolite production; 50% inhibition occurred at 1 in 1000 dilution in the phycoerythrin assay and at 1 in 10-50 dilution with biopsies. Aloe vera inhibited the production of prostaglandin E2 by 30% at 1 in 50 dilution (P = 0.03), but had no effect on thromboxane B2 production. The release of interleukin-8 by CaCo2 cells fell by 20% (P < 0.05) with aloe vera diluted at 1 in 100, but not at 1 in 10 or 1 in 1000 dilutions. CONCLUSION: The anti-inflammatory actions of aloe vera gel in vitro provide support for the proposal that it may have a therapeutic effect in inflammatory bowel disease.     

Surface modification of poly (l-lactic acid) microspheres for site-specific delivery of ketoprofen for chronic inflammatory disease

The purpose of this research was to investigate the potential of surface modified Poly (l-lactic acid) (PLA) microspheres as a carrier for site-specific delivery of anti-inflammatory drug, ketoprofen, for the treatment of rheumatoid arthritis. Microspheres were prepared by solvent evaporation method using 20% w/w PLA in methylene chloride and 100 mL of a 2.5% poly vinyl alcohol (PVA) solution. Formulations were optimized for several processing parameters like drug to polymer ratio, stirring rate and volume of preparation medium etc. The surface of PLA microspheres was modified with gelatin to impart fibronectin recognition. The microspheres were characterized by surface morphology, size distribution, encapsulation efficiency, and by in vitro drug release studies. The prepared microspheres were light yellow, discrete, and spherical. Formulation with optimum drug to polymer ratio exhibited smallest vesicle size (43.02), high drug encapsulation efficiency (81.11) and better process yield (83.45). The release of drug was extended up to 24 h with Higuchi pattern of drug release. The in vivo results showed that the gelatin modified formulation reduced paw edema at greater extent than pure drug and PLA microspheres and it could be a promising carrier system for controlled and site-specific delivery of ketoprofen with possible clinical applications.     

Randomized, double-blind, placebo-controlled trial of oral aloe vera gel for active ulcerative colitis

BACKGROUND: The herbal preparation, aloe vera, has been claimed to have anti-inflammatory effects and, despite a lack of evidence of its therapeutic efficacy, is widely used by patients with inflammatory bowel disease. AIM: To perform a double-blind, randomized, placebo-controlled trial of the efficacy and safety of aloe vera gel for the treatment of mildly to moderately active ulcerative colitis. METHODS: Forty-four evaluable hospital out-patients were randomly given oral aloe vera gel or placebo, 100 mL twice daily for 4 weeks, in a 2 : 1 ratio. The primary outcome measures were clinical remission (Simple Clinical Colitis Activity Index /= 3 points; response was defined as remission or improvement), Baron score, histology score, haemoglobin, platelet count, erythrocyte sedimentation rate, C-reactive protein and albumin. RESULTS: Clinical remission, improvement and response occurred in nine (30%), 11 (37%) and 14 (47%), respectively, of 30 patients given aloe vera, compared with one (7%) [P = 0.09; odds ratio, 5.6 (0.6-49)], one (7%) [P = 0.06; odds ratio, 7.5 (0.9-66)] and two (14%) [P < 0.05; odds ratio, 5.3 (1.0-27)], respectively, of 14 patients taking placebo. The Simple Clinical Colitis Activity Index and histological scores decreased significantly during treatment with aloe vera (P = 0.01 and P = 0.03, respectively), but not with placebo. Sigmoidoscopic scores and laboratory variables showed no significant differences between aloe vera and placebo. Adverse events were minor and similar in both groups of patients. CONCLUSION: Oral aloe vera taken for 4 weeks produced a clinical response more often than placebo; it also reduced the histological disease activity and appeared to be safe. Further evaluation of the therapeutic potential of aloe vera gel in inflammatory bowel disease is needed.     

Gelatin microspheres of rifampicin cross-linked with sucrose using thermal gelation method for the treatment of tuberculosis

Oral controlled release microspheres of rifampicin (RIF) were prepared in order to circumvent the required regular high dose of the conventional dosage forms for the treatment of tuberculosis. Rifampicin containing microspheres were designed by using a biodegradable and biocompatible polymer, gelatin B, using a thermal gelation method. The microspheres were cross-linked with natural cross-linker, sucrose, to avoid the toxicities due to the synthetic di- and poly-aldehydes. This formulation was found to be controlled release for drug in the gastro-intestinal tract. Drug encapsulation efficiency was found to be in the range of 52-83%. These microspheres were characterized for; particle size analysis by optical microscopy and scanning electron microscopy; in vitro release study by USP paddle apparatus and drug polymer interaction study using DSC and FT-IR. The results suggested that microspheres prepared by the above method were smaller in size, i.e. less than 60 microm and sucrose could be used as an interesting means to cross-link gelatin B microspheres, allowing the use of this formulation for controlled release of rifampicin. Microspheres could be observed in the intestinal lumen at 4 h and were detectable in the intestine 24 h post-oral administration, although the percentage of radioactivity had significantly decreased (t(1/2) of (99m)Tc = 4-5 h). Dissolution and scintigraphy studies have shown promising results, proving the utility of the formulation for the whole intestine.     

Effect of Formulation and Processing Variables on the Characteristics of Tolmetin Microspheres Prepared by Double Emulsion Solvent Diffusion Method

The aim of this study was to evaluate microencapsulated controlled release preparations of tolmetin sodium using ethylcellulose as a retardant material. Microspheres were prepared by using water-in-oil-in-oil (W/O₁/O₂) double-emulsion solvent diffusion method, using different ratios of ethylcellulose to tolmetin sodium. Span 80 was used as the droplet stabilizer and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeritic properties, drug content, loading efficiency, production yield, and particle size. Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray powder diffractometry and scanning electron microscopy were used to characterize microparticles. The in vitro release studies were performed in pH 1.2 and 7.4. The prepared microspheres were spherical in shape. The drug-loaded microspheres showed near to the theoretical of entrapment and release was extended up to 24. The X-ray diffractogram and differential scanning thermographs showed amorphous state of the drug in the microspheres. It was shown that the drug: polymer ratio, stirring rate, volume of dispersing medium and surfactant influenced the drug loading, particle size and drug release behavior of the formed microparticles. The results showed that, generally, an increase in the ratio of drug: polymer (0.5:1) resulted in a reduction in the release rate of the drug which may be attributed to the hydrophobic nature of the polymer. The in vitro release profile could be modified by changing various processing and formulation parameters to give a controlled release of drug from the microparticules. The release of tolmetin was influenced by the drug to polymer ratio and particle size and was found to be diffusion and erosion controlled. The best-fit release kinetic was achieved with Peppas model.     

Preparation and characterization of ibuprofen microspheres

Ibuprofen was microencapsulated with Eudragit RS using an o/w emulsion solvent evaporation technique. The effects of three formulation variables including the drug:polymer ratio, emulsifier (polyvinyl alcohol) concentration and organic solvent (chloroform) volume on the entrapment efficiency and microspheres size distribution were examined. The drug release rate from prepared microspheres and the release kinetics were also studied. The results demonstrated that microspheres with good range of particle size can be prepared, depending on the formulation components. The drug:polymer ratio had a considerable effect on the entrapment efficiency. However, particle size distribution of microspheres was more dependent on the volume of chloroform and polyvinyl alcohol concentration rather than the drug:polymer ratio. The drug release pattern showed a burst effect for all prepared microspheres due to the presence of uncovered drug crystals on the surface. It was shown that the release profiles of all formulations showed good correlation with the Higuchi model of release.     

尼莫地平明胶微球的制备及其性质研究

目的研究尼莫地平明胶微球的制备工艺,并考察其体外释药特性。方法以天然的可生物降解的明胶为载体,液体石蜡为油相,Span80为乳化剂,采用正交设计优化空白明胶微球的制备工艺,用乳化法制备尼莫地平明胶微球。结果优选所制尼莫地平明胶微球形态圆整,大小均匀,表面光滑,载药量为13.48%。体外释药结果表明,一级动力学方程能较好地对其进行拟合。结论制备工艺稳定可行,所得尼莫地平明胶微球具有良好的缓释效果。     

Preparation and characterization of ibuprofen microspheres

Ibuprofen was microencapsulated with Eudragit RS using an o/w emulsion solvent evaporation technique. The effects of three formulation variables including the drug:polymer ratio, emulsifier (polyvinyl alcohol) concentration and organic solvent (chloroform) volume on the entrapment efficiency and microspheres size distribution were examined. The drug release rate from prepared microspheres and the release kinetics were also studied. The results demonstrated that microspheres with good range of particle size can be prepared, depending on the formulation components. The drug:polymer ratio had a considerable effect on the entrapment efficiency. However, particle size distribution of microspheres was more dependent on the volume of chloroform and polyvinyl alcohol concentration rather than the drug:polymer ratio. The drug release pattern showed a burst effect for all prepared microspheres due to the presence of uncovered drug crystals on the surface. It was shown that the release profiles of all formulations showed good correlation with the Higuchi model of release.     

Solid lipid nanoparticles bearing oxybenzone: In-vitro and in-vivo evaluation

In the present project, Solid Lipid Nanoparticles (SLNs) bearing oxybenzone were prepared by ethanol injection method to improve its effectiveness as sunscreen. SLNs were characterized for particle size, polydispersity index, zeta potential and surface morphology. The optimized SLNs bearing oxybenzone were incorporated into water-removable cream base and compared with SLNs unloaded water-removable cream base for in vitro and in vivo parameters. Cream base formulation containing SLNs (Csd) with 5% oxybenzone showed slow drug release and better sun protecting factor (more than 25) compared to cream base containing 5% oxybenzone. Confocal Laser Scanning Microscopy was used to visualize the distribution of developed formulations in skin. CLSM indicated prolonged retention of SLNs in the stratum corneum as compared to plain cream base. These studies revealed that the cream base bearing SLNs exhibited good skin retention as well as enhanced sun protection effect compared to cream base.     

长春西汀聚乳酸-聚乙醇酸缓释微球的研制

目的:制备长春西汀聚乳酸-聚乙醇酸(PLGA)缓释微球,并研究其药剂学性质。方法:采用改良O/W乳化-溶剂挥发法制备微球,以PLGA浓度、理论载药量、有机相与分散介质的比例和分散介质中明胶的浓度为4因素,每个因素选定3个水平,按L9(34)的正交设计方案,以载药量、包封率和粒径分布为指标,优化处方。用扫描电镜观察微球的形态,用光学显微镜观察并计算微球的粒径分布,用差示扫描量热(DSC)法研究药物在载体中的分散状态,用紫外分光光度法检测微球中长春西汀含量并计算载药量和包封率,用动态透析释药法进行微球的体外释放研究。结果:最佳处方为PLGA浓度16%,理论载药量20%,有机相与分散介质的比例1:10,分散介质中明胶的浓度1%;制备的长春西汀PLGA缓释微球的形态圆整、光滑,粒径分布均匀,平均粒径为(10.0±0.18)μm(n=500),DSC法分析药物确已被包裹于微球中,载药量为(18.46±0.26)%,包封率为(91.30±0.98)%(n=3),24h累积释药率约为18%。结论:长春西汀PLGA缓释微球制备工艺稳定,质量符合药剂学要求,缓释性好。     

In vitro and in vivo evaluation of ranitidine hydrochloride loaded hollow microspheres in rabbits

The objective of this investigation was to develop the hollow microspheres as a new dosage form of floating drug delivery systems with prolonged stomach retention time. Hollow microspheres containing ranitidine hydrochloride (RH) were prepared by a novel solvent diffusion-evaporation method using ethyl cellulose (EC) dissolved in a mixture of ethanol and ether (6:1.0, v/v). The yield and drug loading amount of hollow microspheres were 83.21±0.28% and 20.71±0.32%, respectively. The in vitro release profiles showed that the drug release rate decreased with increasing viscosity of EC and the diameter of hollow microspheres, while increased with the increase of RH/EC weight ratio. Hollow microspheres could prolong drug release time (approximately 24 h) and float over the simulate gastric fluid for more than 24 h. Pharmacokinetic analysis showed that the bioavailability from RH-hollow microspheres alone was about 3.0-times that of common RH gelatin capsules, and it was about 2.8-times that of the solid microspheres. These results demonstrated that RH hollow microspheres were capable of sustained delivery of the drug for longer period with increased bioavailability.     

洛索洛芬钠缓释微球的制备及体外释药特性考察

目的延缓洛索洛芬钠在局部的作用时间,了解洛索洛芬钠缓释微球的体外释药特性。方法采用乳化-化学交联法制备明胶微球,采用正交试验优化明胶微球的处方和制备工艺;采用流化床包衣技术制备缓释微球;采用透析法考察体外释药特性。结果制备明胶微球最优处方和工艺为:洛索洛芬钠5.0 g,质量分数为20%的明胶溶液100 mL作为水相,含质量分数0.5%Span 80的液体石蜡混合液400 mL作为油相,55℃搅拌下将水相缓缓加入至油相中,500 r.min-1乳化20 min,冰水浴20 min,加入戊二醛使体积分数为50%,交联90 min,4000 r.min-1离心分离10 min,用丙酮、乙醚交替洗涤3次,40℃真空干燥12 h;制备的明胶微球平均粒径为18.25μm,载药量为19.37%,包封率为87.72%,包衣后质量增加25%;洛索洛芬钠缓释微球体外释药过程符合Higuchi方程。结论制备的洛索洛芬钠缓释微球具有明显的缓释作用。     

Controlled release of nifedipine from gelatin microspheres and microcapsules: in vitro kinetics and pharmacokinetics in man

Abstract

Nifedipine was embedded in a gelatin matrix to develop a prolonged release dosage form. The effects of polymer/drug ratio, size of the beads, cross-linking with formaldehyde and ethylcellulose coating of the gelatin microspheres on the in vitro release rate of the drug were investigated. The data were analysed according to different laws that can govern the release mechanism: first-order, Higuchi square root of time, spherical matrix and zero-order. The in vitro release kinetics of nifedipine from gelatin microspheres were mainly first-order; from formaldehyde hardened gelatin microspheres, complied with the diffusion model for a spherical matrix, and from ethylcellulose-coated gelatin microspheres, obeyed zero-order kinetics. These findings suggest the possibility of modifying the formulation in order to obtain the desired controlled release of the drug for a convenient oral sustained delivery system. The pharmacokinetic parameters of nifedipine, after adminstration of a single oral dose of nifedipine-loaded hardened gelatin microspheres to volunteers, suggest that the preparation can be considered as a sustained release delivery system for nifedipine.