Browsing by Author "SUNNY, MC"

Now showing 1 - 13 of 13
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    COLLAGENATED POLYETHER URETHANE UREA - THEIR MODIFICATION TOWARDS ANTITHROMBOGENICITY
    (ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 1988) SHARMA, CP; SUNNY, MC
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    CONTROLLED RELEASE OF ORAL-DRUGS FROM CROSS-LINKED POLYVINYL-ALCOHOL MICROSPHERES
    (JOURNAL OF PHARMACY AND PHARMACOLOGY, 1993)
    A new technique for the preparation of cross-linked polyvinyl alcohol (PVA) microspheres containing various drugs is described. An aqueous solution of PVA containing various concentrations of glutaraldehyde was dispersed as droplets in liquid paraffin using a suitable stabilizing agent. Cross-linking of PVA droplets with glutaraldehyde was induced by an acid catalyst (HCI) which was produced by the addition of small quantities of benzoyl chloride into the dispersion medium. Microspheres containing drugs such as aspirin, griseofulvin and nicotinic acid were prepared by carrying out the cross-linking reaction in the presence of such drugs. The drug release studies were carried out in simulated gastric and intestinal fluids without enzymes at 37-degrees-C. It was observed that increase in the cross-linking density of the microspheres reduced the drug release rate considerably, suggesting that the release profiles could be controlled by changing the cross-linking density. It was also observed that a higher rate of release was obtained from smaller beads.
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    CROSS-LINKED CHITOSAN MICROSPHERES - PREPARATION AND EVALUATION AS A MATRIX FOR THE CONTROLLED RELEASE OF PHARMACEUTICALS
    (JOURNAL OF PHARMACY AND PHARMACOLOGY, 1992)
    Chitosan microspheres having good spherical geometry and a smooth surface were prepared by the glutaraldehyde cross-linking of an aqueous acetic acid dispersion of chitosan in paraffin oil using dioctyl sulphosuccinate as the stabilizing agent. Microspheres having different degrees of swelling were made by varying the cross-linking density. Microspheres were prepared by incorporating theophylline, aspirin or griseofulvin. Drug incorporation efficiencies exceeding 80% could be achieved for these drugs. In-vitro release studies of these drugs were carried out in simulated gastric and intestinal fluids at 37-degrees-C. It was observed that the drug release rates were influenced by the cross-linking density, particle size and initial drug loading in the microspheres.
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    EVALUATION OF AN ALIPHATIC POLYURETHANE AS A MICROSPHERE MATRIX FOR SUSTAINED THEOPHYLLINE DELIVERY
    (JOURNAL OF MICROENCAPSULATION, 1995) SUBHAGA, CS; RAVI, KG; SUNNY, MC; JAYAKRISHNAN, A
    In spite of several biomedical applications of polyurethanes, very little attention has been focused on these polymers for controlled drug delivery. In this study, an aliphatic polyurethane, Tecoflex(R), was evaluated as a microsphere matrix for the controlled release of theophylline. Polyurethane microspheres containing theophylline were prepared using a solvent evaporation technique from a dichloromethane solution of the polymer containing the drug. A dilute solution of poly(vinyl alcohol) served as the dispersion medium. Microspheres of good spherical geometry having theophylline content of 35% could be prepared by the technique. The release of the drug from the microspheres was examined in simulated gastric and intestinal fluids at 37 degrees C. While a large burst effect was observed in gastric fluid, in the intestinal fluid a close to zero-order release was seen. Attempts were made to modulate the release by incorporating poly(ethylene glycol) in the matrix and also coating the spheres with paraffin wax. Preliminary data indicate that polyurethanes could be interesting matrices for controlled drug delivery.
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    FIBRINOGEN ALUMINUM INTERACTION - CHANGES WITH OXIDE LAYER THICKNESS ONTO METAL-SURFACE
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, 1990)
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    ORAL SUSTAINED-RELEASE DRUG DELIVERY SYSTEMS USING POLYCARBONATE MICROSPHERES CAPABLE OF FLOATING ON THE GASTRIC FLUID
    (JOURNAL OF PHARMACY AND PHARMACOLOGY, 1993)
    Polycarbonate microspheres loaded with aspirin, griseofulvin and p-nitroaniline were prepared by a solvent evaporation technique. High drug loading (> 50%) was achieved by this process. Drug-loaded microspheres were found to float on simulated gastric fluid and intestinal fluid. Drug-release studies were carried out in these fluids at 37-degrees-C. Increasing the drug to polymer ratio in the microspheres increased both their mean particle size and the release rate of the drugs. It was concluded that sustained delivery of drugs could be effected using this matrix.
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    PHOTO-CROSS-LINKING OF AZIDATED POLY(VINYL CHLORIDE) COATED ONTO PLASTICIZED PVC SURFACE - ROUTE TO CONTAINING PLASTICIZER MIGRATION
    (JOURNAL OF APPLIED POLYMER SCIENCE, 1995) JAYAKRISHNAN, A; SUNNY, MC; RAJAN, MN
    The migration of phthalate esters which are commonly employed for plasticizing poly(vinyl chloride) (PVC) is a significant problem in PVC-based medical devices as well as in packaging used for food stuffs and pharmaceuticals. Medical-grade PVC resin was treated with sodium azide in dimethylformamide (DMF) to prepare the azide polymer. The polymeric azide was coated onto the surface of plasticized PVC sheets by dipping in a solution of the polymer in tetrahydrofuran (THF). Crosslinking of the azide polymer was accomplished by irradiating the surface using a 125 W UV lamp for various lengths of time. Migration of the plasticizer di-2-(ethylhexyl phthalate) (DEHP) from coated and uncoated samples was examined in n-hexane at 30 degrees C. It was found that 50-80% reduction in migration of DEHP could be effected from plasticized PVC in comparison with the controls in 72 h by this technique depending on the concentration of the coating solution, coating thickness, azide concentration, and irradiation dose. (C) 1995 John Wiley and Sons, Inc.
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    POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE AS LARGE SIZE SPHERICAL BEADS
    (POLYMER, 1990) JAYAKRISHNAN, A; SUNNY, MC; THANOO, BC
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    PREPARATION AND PROPERTIES OF BARIUM-SULFATE AND METHYL IOTHALAMATE LOADED POLY(VINYL ALCOHOL) MICROSPHERES AS RADIOPAQUE PARTICULATE EMBOLI
    (JOURNAL OF APPLIED BIOMATERIALS, 1991) THANOO, BC; SUNNY, MC; JAYAKRISHNAN, A
    Poly(vinyl alcohol) (PVA) microspheres impregnated with barium sulphate and methyl iothalamate, having diameters ranging from 100 to 1500-mu-m were prepared by the glutaraldehyde cross-linking of an aqueous dispersion of PVA containing the radiopaques in paraffin oil using dioctyl sulfosuccinate (DOS) as the stabilizing agent and thionyl chloride as the catalyst. While the use of thionyl chloride allowed the formation of spherical, nonaggregatory beads, other catalysts such as magnesium chloride and hydrochloric acid gave rise to an agglomerated product. The radiopaques were found to be firmly trapped inside the microspheres as they did not leach out on prolonged standing in water, on sonication, or on stem sterilization. Microspheres with pores and channels were also made by incorporating a fine powder of methyl methacrylate along with barium sulphate during their preparation and washing out the polymer after the microspheres were formed. The porous nature of such microspheres was confirmed by transmission electron microscopy (TEM). Microspheres containing the radiopaques exhibited hydrophilicity, swelling ability, and compressibility to a significant extent. The radiopaque nature of the microspheres was confirmed by their x-ray images. In vitro tests using heparinized calf blood showed that the microspheres were nonhaemolytic in nature. These microspheres may find application as radiopaque emboli in particulate embolization.
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    SURFACE MODIFICATION OF CORNEAL CONTACT-LENS WITH PHOSPHORYL CHOLINE BY GLOW-DISCHARGE
    (BIOMATERIALS ARTIFICIAL CELLS AND IMMOBILIZATION BIOTECHNOLOGY, 1991)
    Polymers like poly(methylmethacrylate) (PMMA) and poly(2-hydroxyethylmethacrylate) (PHEMA) are widely used in the development of hard and soft contact lenses. Cell adhesion and deposition of chemicals such as calcium, lipoproteins and mucin on the lens surface cause visual acuity which is the main problem in extended uses of contact occular lenses. In order to minimise the cell adhesion and other type of depositions, a method of surface modification of lens involving the use of phosphoryl choline, a phospholipid and the glow discharge technique has been described. The power variation of the lenses after modification has been checked using Topcon lensometer. The possible power changes of the modified samples due to the exposure to the normal light in the laboratory, darkness, ultraviolet (U.V.) light or saline have been investigated by taking the visible and ultra violet spectra using Beckman spectrophotometer. Surface energy variations after modifications of the samples have been checked by sessile drop water contact angle measurements. Glow discharge treatment increases the hydrophilicity of the samples. It seems, the modifications do not affect the power of hard contact lens significantly. It is also observed that the exposure of samples to the normal light in the laboratory, darkness, U.V. light or saline make no significant change in the visible and ultraviolet spectra of the samples before and after modification.
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    TANTALUM-LOADED POLYURETHANE MICROSPHERES FOR PARTICULATE EMBOLIZATION - PREPARATION AND PROPERTIES
    (BIOMATERIALS, 1991)
    Polyurethane microspheres having diameters in the range 150-1500-mu-m were prepared by condensation polymerization of toluene diisocyanate (TDI) with poly(tetramethylene glycol) (PTMG) of average mol wt 990 in an aqueous dispersion medium containing dioctyl sulphosuccinate (DOS) as the suspension stabilizer and 1,4-diazabicyclo[2.2.2]octane (DABCO) as the catalyst for polymerization. Incorporation of tantalum powder in the polymerizing phase led to the formation of Ta-loaded microspheres with good radiopacity. Microspheres were surface-modified by grafting methacrylic acid (MA) on to them using gamma-radiation from a Co60 source. Conversion of the grafted MA into its sodium salt imparted hydrophilicity and slipperiness to the microspheres enabling them to pass through Teflon(R) cathers without obstructing the catheter lumen. These microspheres may find application as radiopaque embolization agents.