Browsing by Author "THANOO, BC"

Now showing 1 - 16 of 16
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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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    HYDROGEL MICROSPHERES FROM CROSSLINKED POLY(METHYL METHACRYLATE) - SYNTHESIS AND BIOCOMPATIBILITY STUDIES
    (BULLETIN OF MATERIALS SCIENCE, 1989) JAYAKRISHNAN, A; THANOO, BC; RATHINAM, K; MANDALAM, KR; RAO, VRK; LAL, AV; MOHANTY, M
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    HYDROLYZED MICROSPHERES FROM CROSS-LINKED POLYMETHYL METHACRYLATE (HYDROGEL) - A NEW EMBOLIC MATERIAL FOR INTERVENTIONAL NEURORADIOLOGY
    (JOURNAL OF NEURORADIOLOGY, 1991)
    Highly hydrophilic, perfectly smooth and spherical microspheres have been synthetized. These non-biodegradable microspheres absorb water in varying degrees and can be injected easily through microcatheters due to their slippery and compressible characteristics. The material was successfully used of embolization of 4 vascular intracranial tumours and 2 spinal vascular lesions in the cervical region, by superselective delivery. Histopathology confirmed absolute inertness of the microspheres.
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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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    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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    PREPARATION OF HYDROGEL BEADS FROM CROSSLINKED POLY(METHYL METHACRYLATE) MICROSPHERES BY ALKALINE-HYDROLYSIS
    (JOURNAL OF APPLIED POLYMER SCIENCE, 1990) THANOO, BC; JAYAKRISHNAN, A
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    RADIOPAQUE HYDROGEL MICROSPHERES
    (JOURNAL OF MICROENCAPSULATION, 1989)
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    SYNTHESIS AND POLYMERIZATION OF SOME IODINE-CONTAINING MONOMERS FOR BIOMEDICAL APPLICATIONS
    (JOURNAL OF APPLIED POLYMER SCIENCE, 1992) JAYAKRISHNAN, A; THANOO, BC
    Triiodophenol and iothalamic acid (5-acetamido-2,4,6-triiodo-N-methyl isophthalamic acid) were converted to their acrylic derivatives by esterification with methacryloyl chloride and 2-hydroxyethyl methacrylate (HEMA), respectively. The monomers due to presence of heavy iodine atoms were expected to be radiopaque in nature. The monomers were characterized using TLC, IR, and H-1-NMR spectroscopy. Both monomers were highly resistant to homopolymerization and copolymerization with other acrylic monomers such as methyl methacrylate (MMA) or HEMA by initiators such as 2,2'-azobis isobutyronitrile (AIBN) or benzoyl peroxide (BPO) yielding only polymers of low molecular weight. The polymers obtained were characterized by gel permeation chromatography (GPC) and differential thermal analysis (DTA). The resistance to polymerization is presumably due to the presence of bulky iodine atoms in the monomers sterically hindering the propagation step. The decomposition temperatures of the homopolymers and copolymers were close to 300-degrees-C. Copolymers of HEMA with both radiopaque monomers incorporated to the extent of 25 wt % in the feed, however, produced polymers with good radiopacity. Copolymers with HEMA were also prepared in the form of microspheres by a solvent evaporation method with the aim of using them as particles in therapeutic embolization. While the polymer based on triiodophenol was found to cause extensive blood haemolysis in in vitro tests, polymer based on iothalamic acid was found to be nonhemolytic in character suggesting that copolymers based on iothalamic acid would be suitable for implantation in the living tissue.
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    SYNTHETIC HYDROGEL MICROSPHERES AS SUBSTRATA FOR CELL-ADHESION AND GROWTH
    (IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY, 1989) SHIVAKUMAR, K; NAIR, RR; JAYAKRISHNAN, A; THANOO, BC; KARTHA, CC
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    TANTALUM LOADED SILICONE MICROSPHERES AS PARTICULATE EMBOLI
    (JOURNAL OF MICROENCAPSULATION, 1991)
    Chloroform solutions of medical grade silicone resin were cured in an aqueous dispersion medium containing poly(vinyl alcohol) (PVA) as the drop stabilizer at 40-60-degrees-C to generate smooth, spherical, elastic microspheres. The microspheres were encapsulated with tantalum powder to render them radiopaque. Tantalum loaded microspheres having diameter more than 1.00 mm could be prepared by this technique. Incorporation of radiopaques such as barium sulphate and methyl iothalamate resulted in the instability of the suspension giving rise to an agglomerated product. Microspheres were grafted with hydrophilic monomers such as 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP) using ionizing radiation from a Co-60 source in an effort to make their surfaces hydrophilic. While the graft yield was very little when HEMA alone was used for grafting, a combination of HEMA/NVP in a 1:1 ratio produced better graft yields resulting in improved surface hydrophilicity. The tantalum loaded microspheres were found to be very resistant to surface modification. Microspheres could be dispersed in water with the aid of small quantities of surfactants such as Tween 20. These microspheres may find use in particulate embolization.
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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.