Enhanced visible photoluminescence in ZnO quantum dots by promotion of oxygen vacancy formation.

We report on the synthesis of ZnO quantum dots (QDs) rich in oxygen vacancies by inducing an oxygen deficient environment. The precise tunability of particle size is achieved by counter ion capping of the precursor used for synthesis. The prepared QDs show size tunable visible emission with high quantum yield.

Plant system: nature's nanofactory.

Three categories of plants growing under three different extreme conditions were taken for assaying their promises to undertake nano-transformation. It was found that all of them successfully synthesize silver nanoparticles. The synthesis was performed akin to room temperature. X-ray and transmission electron microscopy analyses were performed to ascertain the formation of silver nanoparticles. X-ray analysis indicated that silver nanoparticles have FCC unit cell structure. Individual nanoparticles having the particle sizes of 2-5 nm were found. Possible involved mechanisms for the synthesis of silver nanoparticles from above plant systems have also been proposed.

Synthesis of TiO2 nanoparticles using microorganisms.

A low-cost green and reproducible microbes (Lactobacillus sp. and Sachharomyces cerevisae) mediated biosynthesis of TiO(2) nanoparticles is reported. The synthesis is performed akin to room temperature in the laboratory ambience. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of TiO(2) nanoparticles. Individual nanoparticles as well as a few aggregate having the size of 8-35 nm are found. Concentric Scherrer rings in the selected area electron diffraction pattern indicated that the nanoparticles are having all possible orientations. A possible involved mechanism for the biosynthesis of nano-TiO(2) has also been proposed in which pH as well as partial pressure of gaseous hydrogen (rH(2)) or redox potential of the culture solution seems to play an important role in the process.

pH-Sensitive Mebeverine Microspheres for Colon Delivery.

Mebeverine hydrochloride is known to suffer from extensive first pass effect. In an attempt to improve its oral bioavailability and possibility to restrict its absorption only to the colon, mebeverine microspheres were prepared by emulsion solvent evaporation method. Four formulations were prepared with varying drug and polymer ratio. These formulations were subjected to various evaluation parameters like percent practical yield, entrapment efficiency, particle size, in vitro drug release, in vivo activity. Practical yield of the microspheres was up to 89.59% with encapsulation efficiency up to 79.4%. Scanning electron microscopy confirmed that the microsphere structures were smooth, spherical, and discrete and the particles were of the size range 200 to 300 mum. In vitro release of the drug showed biphasic release pattern with non-Fickian diffusion release in 12 h. On the basis of drug content, particle size, in vitro release and in vivo studies, formulation F-3 was found to be optimal. Antiirritable bowel syndrome activity was performed in colorectal distention in rat, which is a model for constipation-induced irritable bowel syndrome. The formulations F-2 and F-3 showed significant effect in fecal output when compared to the control as well as the marketed preparation in the constipation-induced irritable bowel syndrome in rats.

In vitro and in vivo evaluation of ranitidine hydrochloride ethyl cellulose floating microparticles.

The real issue in the development of oral controlled release dosage forms is not just to prolong the delivery of drugs but also to prolong the presence of dosage forms in the stomach in order to improve the bioavailability of drugs with a 'narrow absorption window'. In the present study, an anti-ulcer drug, ranitidine hydrochloride, is delivered through a gastroretentive ethyl cellulose-based microparticulate system capable of floating on simulated gastric fluid for > 12 h. Preparation of microparticles is done by solvent evaporation technique with modification by using an ethanol co-solvent system. The formulated microspheres were free flowing with good packability and encapsulation efficiencies were up to 96%. Scanning electron microscopy confirmed porous, spherical particles in the size range 300-750 microm. Microspheres showed excellent buoyancy and a biphasic controlled release pattern with 12h. In vivo bioavailability studies performed on rabbits and T(max), C(max), AUC were calculated and confirmed significant improvement in bioavailability. The data obtained thus suggests that a microparticulate floating delivery system can be successfully designed to give controlled drug delivery, improved oral bioavailability and many other desirable characteristics.

Time and pH dependent colon specific, pulsatile delivery of theophylline for nocturnal asthma.

In this study, investigation of an oral colon specific, pulsatile device to achieve time and/or site specific release of theophylline, based on chronopharmaceutical consideration. The basic design consists of an insoluble hard gelatin capsule body, filled with eudragit microcapsules of theophylline and sealed with a hydrogel plug. The entire device was enteric coated, so that the variability in gastric emptying time can be overcome and a colon-specific release can be achieved. The theophylline microcapsules were prepared in four batches, with Eudragit L-100 and S-100 (1:2) by varying drug to polymer ratio and evaluated for the particle size, drug content and in vitro release profile and from the obtained results; one better formulation was selected for further fabrication of pulsatile capsule. Different hydrogel polymers were used as plugs, to maintain a suitable lag period and it was found that the drug release was controlled by the proportion of polymers used. In vitro release studies of pulsatile device revealed that, increasing the hydrophilic polymer content resulted in delayed release of theophylline from microcapsules. The gamma scintigraphic study pointed out the capability of the system to release drug in lower parts of GIT after a programmed lag time for nocturnal asthma. Programmable pulsatile, colon-specific release has been achieved from a capsule device over a 2-24h period, consistent with the demands of chronotherapeutic drug delivery.

Phacoemulsification in true exfoliation of the lens capsule: a case series.

PURPOSE: We report five cases (seven eyes) of true exfoliation during an 18-month period. Of the two bilateral cases, the first was identified immediately before cataract surgery and the second spontaneously developed a split in the anterior capsule just before capsulorrhexis, mimicking a partial capsulorrhexis. In the three unilateral cases, true exfoliation was noted during the first examination. METHODS: Vision blue aided uneventful capsulorrhexis differentiating its edge from the true exfoliation edge, and in the first two cases, the anterior capsule was sent for histopathology and ultrasound of the fellow eye was requested. RESULTS: Ultrasound and histopathology demonstrated lamellar separation of the anterior portion of the lens capsule, confirming the diagnosis of true exfoliation. Cataract surgery by phacoemulsification was uneventful in all cases. CONCLUSION: True exfoliation of the lens capsule can masquerade as a partial capsulorrhexis and should be looked for before surgery and immediately before capsulorrhexis to avoid creating a partial thickness capsulorrhexis and its related surgical complications. No zonule weakness was appreciated in our cases. To our knowledge, the spontaneous occurrence of a curvilinear lamellar capsular dehiscence with a flap before capsulorrhexis has not been reported before. This series highlights that cataracts associated with true exfoliation of the lens capsule can be safely operated, with the help of vision blue, by routine phacoemulsification without having to convert to the extracapsular technique.

Ocular manifestations of head injury: a clinical study.

AIM: This prospective study aimed to clinically correlate the various ocular findings with the neurological status in cases of closed head injury. METHODS: A total of 200 consecutive cases of closed head injury admitted to a major teaching hospital underwent a thorough ophthalmic assessment. The Glasgow coma scale (GCS) and the Revised trauma score (RTS) were applied to grade the severity of injury and assess the prognosis. Kendall's tau-b and Fisher's exact test were used in the analysis. RESULTS: The main causes of head injury were road traffic accidents 52.5% followed by assaults in 34%. Ocular involvement was found in 167(83.5%) cases. These included corneal and scleral tears in 2%, subconjunctival haemorrhage or ecchymosis in 46%, orbital fractures 12%, pupillary involvement 6.5%, papilloedema 5.5%, intraocular trauma 5.5%, proptosis 3%, lateral rectus palsy 2%, lacrimal gland prolapse 1%, and optic nerve trauma 0.5%. All 21 patients (10.5%) who died had eye involvement. In all, 150 cases (75%) with a RTS of 12 had a good prognosis. Of these 124 (82.6%) had ocular involvement of no neurological significance. CONCLUSIONS: Although sophisticated imaging techniques are available to localize lesions, early ophthalmic assessment in correlation with the GCS aids in prognosticating outcomes. Pupillary involvement, papilloedema, and ocular motor paresis pointed to a more severe head injury. To our knowledge, this is the only prospective study recording ocular findings in the first few hours and attempting a correlation with the final outcome.

Spontaneous rupture of spleen in falciparum malaria.

Spontaneous rupture of spleen is an extremely rare complication of falciparum malaria. We report a 3 1/2-year-old girl with splenic rupture who was managed successfully with splenectomy and antimalarials.

Crosslinked chitosan microspheres for encapsulation of diclofenac sodium: effect of crosslinking agent.

Microspheres of chitosan crosslinked with three different crosslinking agents viz, glutaraldehyde, sulphuric acid and heat treatment have been prepared to encapsulate diclofenac sodium (DS). Chitosan microspheres are produced in a w/o emulsion followed by crosslinking in the water phase by one of the crosslinking methods. Encapsulation of DS has been carried out by soaking the already swollen crosslinked microspheres in a saturated solution of DS. Microspheres are further characterized by FTIR, x-RD and SEM. The in-vitro release studies are performed in 7.4 pH buffer solution. Microspheres produced are spherical and have smooth surfaces, with sizes ranging between 40-230 microm, as evidenced by SEM. The crosslinking of chitosan takes place at the free amino group in all the cases, as evidenced by FTIR. This leads to the formation of imine groups or ionic bonds. Polymer crystallinity increases after crosslinking, as determined by x-RD. The method adopted for drug loading into the microspheres is satisfactory, and up to 28-30% w/w loading is observed for the sulphuric acid-crosslinked microspheres, whereas 23-29 and 15-23% of loadings are obtained for the glutaraldehyde (GA)- and heat-crosslinked microspheres, respectively. Among all the systems studied, the 32% GA crosslinked microspheres have shown the sloxvest release i.e. 41% at 420 min, and a fastest release of 81% at 500 min is shown by heat crosslinking for 3 h. Drug release from the matrices deviates slightly from the Fickian process.

An assessment of solubility profiles of structurally similar hazardous pesticide in water + methanol mixture and co-solvent effect on partition coefficient.

This paper reports solubility and partition coefficient data for the structurally similar pesticides, fenvalerate and cypermethrin, measured by UV spectrophotometry in binary mixtures of methanol and water at different temperatures. The solubility of both pesticides is much higher in methanol than in water at all temperatures. Partition coefficients were also measured between water+heptanol immiscible mixtures at 298.15K, and these data show a decrease with increasing composition of methanol in water.

Cellulose acetate microspheres prepared by o/w emulsification and solvent evaporation method.

The study is concerned with the development of cellulose acetate microspheres by the o/w emulsification and solvent evaporation method in the presence of polyvinyl alcohol as an emulsifying agent. The influence of process parameters such as solvent mixture (acetone + dichloromethane) composition, concentration of the emulsifying agent and speed of stirring has been examined. The microspheres have been analysed for their size, drug loading capacity and release kinetics. Spherical and smooth surfaced microspheres with encapsulation efficiencies ranging between 73-98%, were obtained. Use of acetone in the oil phase drastically reduced the particle size. Slow drug release from microspheres occurred up to approximately 8 h and the release was found to be non-Fickian. An optimization procedure was employed to investigate and identify the key parameters affecting the properties of the microspheres. A 33 randomized full factorial design was used in the analyses of the data. A linear model with interactive terms was generated using a multiple linear regression approach. The statistical analysis confirms the significant effect of solvent composition and concentration of emulsifying agent on the drug release characteristics.

Development of hollow microspheres as floating controlled-release systems for cardiovascular drugs: preparation and release characteristics.

Hollow microspheres of cellulose acetate loaded with four cardiovascular drugs (nifedipine [NFD], nicardapine hydrochloride [NCD], verapamil hydrochloride [VRP], and dipyridamole [DIP]) were prepared by a novel solvent diffusion-evaporation method. The oil-in-water emulsion prepared in an aqueous solution of 0.05% poly(vinyl alcohol) medium with ethyl acetate, a water-soluble and less toxic solvent, was used as the dispersing solvent. The yield of the microspheres was up to 80%. The microspheres had smooth surfaces, with free-flowing and good-packing properties. Scanning electron microscopy (SEM) confirmed their hollow structures, with sizes in the range 489-350 microm. The microspheres tended to float over the gastric media for more than 12 h. The drug loaded in hollow microspheres was in an amorphous state, as confirmed by differential scanning microscopy (DSC). The release of the drugs was controlled for more than 8 h. The release kinetics followed different transport mechanisms depending on the nature of the drug molecules.

Microspheres as floating drug-delivery systems to increase gastric retention of drugs.

Gastric emptying is a complex process, which is highly variable and makes in vivo performance of the drug-delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug-delivery systems for more than 12 h. The floating or hydrodynamically controlled drug-delivery systems are useful in such applications. The present review addresses briefly the physiology of the gastric emptying process with respect to floating drug-delivery systems. In recent years, the multiparticulate drug-delivery systems are used in the oral delivery of drugs. One of the approaches toward this goal is to develop the floating microspheres so as to increase the gastric retention time. Such systems have more advantages over the single-unit dosage forms. The development of floating microspheres involves different solvent evaporation techniques to create the hollow inner core. The present review addresses the preparation and characterization of the floating microspheres for the peroral route of administration of the drug.

Chemically modified polyacrylamide-g-guar gum-based crosslinked anionic microgels as pH-sensitive drug delivery systems: preparation and characterization.

New spherically shaped cross-linked hydrogels of polyacrylamide-grafted guar gum were prepared by the emulsification method. These were selectively derivatized by saponification of the -CONH2 group to the -COOH group. The derived microgels were characterized by FTIR and elemental analyses. The derivatized microgels were responsive to pH and ionic strength of the external medium. The swelling of microgels increased when the pH of the medium changed from acidic to alkaline. Transport parameters, viz., solvent front velocity and diffusion coefficients were calculated from a measurement of the dimensional response of the microgels under variable pH conditions. The variation in pH changed the transport mechanism from Case II (in 0.1 N HCl) to non-Fickian (in pH 7.4 buffer), and these processes are relaxation-controlled. Ionic strength exerted a profound influence on the swelling of the microgels. Swelling was reversible and pulsatile with the changing environmental conditions. The pH-sensitive microgels were loaded with diltiazem hydrochloride and nifedipine (both antihypertensive drugs) and their release studies were performed in both the simulated gastric and intestinal pH conditions. The release was relatively quicker in pH 7.4 buffer than observed in 0.1 N HCl; the release followed non-Fickian transport in almost all the cases.

Encapsulation of antihypertensive drugs in cellulose-based matrix microspheres: characterization and release kinetics of microspheres and tableted microspheres.

This study is an attempt to prepare microspheres loaded with two antihypertensive drugs viz., nifedipine (NFD) and verapamil hydrochloride (VRP) using cellulose-based polymers viz., ethyl cellulose (EC) and cellulose acetate (CA). Emulsification and solvent evaporation methods were optimized using ethyl acetate as a dispersing solvent. The particles are spherical in shape and have smooth surfaces, as evidenced by the scanning electron microscopy. The microspheres were characterized for their particle size and distribution, tapped density and encapsulation efficiency. Smaller sized particles with a narrow size distribution were produced with EC when compared to CA matrices. Molecular level drug distribution in the microspheres was confirmed by differential scanning calorimetry. The microspheres were directly compressed into tablets using different excipients. The drug release from CA was faster than EC microspheres and, also, the VRP release was faster than NFD. The excipients used in tableting showed an effect on the release as well as the physical properties of the tablets.

In-vitro release kinetics of cefadroxil-loaded sodium alginate interpenetrating network beads.

This paper reports the development of new interpenetrating polymeric networks of sodium alginate with gelatin or egg albumin cross-linked with a common cross-linking agent, glutaraldehyde, for the in-vitro release of cefadroxil. The beads formed were characterized by Fourier transform infra-red spectroscopy, scanning electron microscopy and differential scanning calorimetry. Swelling/drying experiments were performed to compute the diffusion coefficients and the molecular mass between cross-links of the beads. The release results were evaluated using an empirical equation to understand the transport mechanism. The extent of cross-linking was studied in terms of the size and release characteristics of the beads. The experimental and derived quantities have been used to study their dependencies on the nature of the polymeric beads, transport mechanism, encapsulation efficiency and drug diffusion, as well as the cross-linking abilities of the polymers.

Biodegradable polymeric nanoparticles as drug delivery devices.

This review presents the most outstanding contributions in the field of biodegradable polymeric nanoparticles used as drug delivery systems. Methods of preparation, drug loading and drug release are covered. The most important findings on surface modification methods as well as surface characterization are covered from 1990 through mid-2000.

In vitro release study of verapamil hydrochloride through sodium alginate interpenetrating monolithic membranes.

Polymeric sodium alginate interpenetrating network membranes containing verapamil hydrochloride were fabricated for transdermal application. The membranes were evaluated for their physical properties, weight and thickness uniformity, water vapor transmission, as well as drug content uniformity. All the thin patches were transparent, smooth, and flexible. The drug-loaded membranes were analyzed by X-ray diffraction to understand the drug polymorphism inside the membrane. The transdermal patches were permeable to water vapor, indicating the permeability characteristics of the polymers. The in vitro drug release was performed in distilled water using a Keshary-Chien diffusion cell. The release data were analyzed to understand the mechanism of drug release.