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S Kalachandra - One of the best experts on this subject based on the ideXlab platform.

  • EVA coPolymer matrix for intra-oral delivery of antimicrobial and antiviral agents.
    Journal of materials science. Materials in medicine, 2007
    Co-Authors: A. Ramadevi, T. Padmavathy, G. Stigall, David W. Paquette, S Kalachandra
    Abstract:

    Biocompatible ethylene vinyl acetate coPolymer (EVA) was utilized to study the release of an antiviral drug (acyclovir (ACY)) and an antimicrobial drug (doxycycline hyclate (DOH)). Release of both drugs from EVA was measured individually and in combination. The effect of drug combination of DOH and ACY is presented. Additionally, the release rate of DOH after coating of the matrix with a different coPolymer, in drug-loading with increasing loads of DOH, and with increases in temperature are also presented. The drugs incorporated in EVA films were prepared from the dry sheet obtained by solvent evaporation of Polymer Casting solutions with drugs. Drug release from the films was examined for about 12 days in distilled water at 37 °C. Changes in optical density were followed spectrophotometrically. The combination of ACY and DOH resulted in an increased release of ACY by about three times (P < 0.001) while DOH showed a decrease in rate of about two times compared to the individual release rates (P = 0.008). Increases in drug levels of DOH resulted in increases in drug release rates (P = 0.001). The release rate of DOH increased with temperature (P = .001; 27, 32, 37 and 42 °C were studied) and the energy of activation (ΔE≠ = 56.69 kJ/mol) was calculated using the Arrhenius equation for the diffusion of DOH molecules. Thus, the release rates of drugs were influenced by many factors: drug combination, coating the device, drug-loading, and temperature variation. Therefore it is proposed that controlling these variables should make it possible to obtain therapeutic levels of drugs released from drug loaded Polymer, which may be beneficial in treating oral infections.

  • Stability and release of antiviral drugs from ethylene vinyl acetate (EVA) coPolymer
    Journal of Materials Science: Materials in Medicine, 2006
    Co-Authors: S Kalachandra, D M Lin, T. Takamata, E. A. Snyder, J. Webster-cyriaque
    Abstract:

    The use of Polymer based drug delivery systems in dentistry is a relatively new area of research with the exception of the inhibition of secondary caries by the release of fluoride ions from polyalkenoate cements and their predecessors silicate cements. The present study was to test on orally biocompatible material, ethylene vinyl acetate coPolymer (EVA), for release of antiviral drugs at oral therapeutic levels over extended periods of time. We also determined their stability during film Casting and release. Materials studied include gancyclovir (GCY), acyclovir (ACY), dichloromethane (DCM), and ethylene vinyl acetate (EVA). The square films (3 × 3 × 0.1 cm) were prepared from the dry sheet obtained by solvent evaporation of Polymer Casting solutions. These solutions were made of EVA and the drug (40:1) in 70 ml of dichloromethane at 38^∘C. Then drug release characteristics from the drug loaded films were examined at 37^∘C for a minimum of 14 days in 10 ml medium (ddwater) replaced daily. Kinetics of drug release were followed by spectral measurements using previously determined λ_max values (GCY = 250 nm; ACY = 253 nm). A minimum of three samples was tested and reproducible results were obtained. Drug stability (ACY) during film Casting and its release was determined using ^1H NMR spectrometer (Bruker DRX-500 and 400). Rate of drug release was determined from the part of the curve (rate vs. time) after the onset of the “burst.” Although GCY has a larger molecular weight (255) than ACY (225), GCY exhibited about three times higher rate of release than ACY. This difference in rate values may be explained due to its relatively greater solubility in EVA, facilitating faster diffusion of the molecules through the channels present in EVA. This is consistent with the observation that the rate at which drug molecules diffuse through the channels of the Polymer, can be increased by decreasing the molecular weight. In the case of ACY, the molecules may be undergoing molecular associations, perhaps dimerization or trimerization in addition to its lower solubility in EVA. The diffusion of ACY tends to be slower under these circumstances compared to GCY resulting in lower rate value than in the case of GCY. Biological studies revealed that ACY exhibited a remarkable decrease in a number of viral organisms present in virus infected cell culture system using real-time Polymerase chain reaction (RT-PCR). NMR analysis indicates that the chemical structure of the drug remains stable during film Casting process and release.

  • Poly(ethylene-co-vinyl acetate) coPolymer matrix for delivery of chlorhexidine and acyclovir drugs for use in the oral environment: Effect of drug combination, coPolymer composition and coating on the drug release rate
    Dental materials : official publication of the Academy of Dental Materials, 2006
    Co-Authors: Padmavathy Tallury, Nazila Alimohammadi, S Kalachandra
    Abstract:

    Abstract Objectives This study utilizes a bio-compatible ethylene vinyl acetate (EVA) coPolymer to deliver drugs at therapeutic levels over extended periods of time. The release rate of an anti-fungal and an anti-microbial drug namely acyclovir (ACY) and chlorhexidine diacetate (CDA) from EVA was investigated individually and as a mixture. The effect of drug combination, the composition of the coPolymer and the coating of the matrix with a different Polymer on the rate of drug release are presented. Method Polymer Casting solutions were prepared by homogeneously dissolving EVA coPolymer and the drugs in the ratio (40:1) in dichloromethane. The drugs ACY and CDA were used individually as well as in three different weight ratios maintaining the total drug concentration in the Polymer at 2.5%. Different concentrations of vinyl acetate (VA) 28, 32 and 40% in the EVA matrix were used to study the release of either ACY or CDA alone while 40% VA was used for the release study of the individual drug as well as their mixtures. Thin square films of 3 cm × 3 cm with a thickness of 0.7 mm were cut from the dry sheet obtained by solvent evaporation. Coated films were prepared by dipping ACY and CDA drug-loaded EVA films (VA 40%) into EVA coPolymer of VA 32% and then dried. All of the drug-loaded samples were extracted at 37 °C in 10 ml distilled water that was replaced daily. The rate of individual drug release was measured by UV-spectrophotometer while the mixtures of drugs were measured by high performance liquid chromatography (HPLC). Results The release rate of ACY is higher than that of CDA both individually and in the ACY/CDA 50/50 mixture. In the other mixtures, the release of the drug is proportional to its concentration in the mixture. Total release of ACY is higher than CDA in most compositions. The effect of increasing the vinyl acetate content of the EVA matrix increased the drug release rate ( p  = 0.02) while coating of films resulted in a decrease of the release rate of the drugs. Significance Measurements of the in vitro rate of drug release showed that there was a sustained release of drug at an almost constant concentration over extended period of time, thus providing a basis for oral treatment modality. We show that it is possible to alter the rate of drug release in the EVA matrix to a desired value by: (1) changing the composition of the EVA coPolymer, (2) altering the mixtures of drugs and (3) coating the matrix with additional Polymer. The use of mixtures of drugs that can enhance or decrease the rate of drug release may prove more effective in treating persistent oral infections in immunocompromised patients.

  • Stability and release of antiviral drugs from ethylene vinyl acetate (EVA) coPolymer.
    Journal of materials science. Materials in medicine, 2006
    Co-Authors: S Kalachandra, D M Lin, T. Takamata, E. A. Snyder, J. Webster-cyriaque
    Abstract:

    The use of Polymer based drug delivery systems in dentistry is a relatively new area of research with the exception of the inhibition of secondary caries by the release of fluoride ions from polyalkenoate cements and their predecessors silicate cements. The present study was to test on orally biocompatible material, ethylene vinyl acetate coPolymer (EVA), for release of antiviral drugs at oral therapeutic levels over extended periods of time. We also determined their stability during film Casting and release. Materials studied include gancyclovir (GCY), acyclovir (ACY), dichloromethane (DCM), and ethylene vinyl acetate (EVA). The square films (3 x 3 x 0.1 cm) were prepared from the dry sheet obtained by solvent evaporation of Polymer Casting solutions. These solutions were made of EVA and the drug (40:1) in 70 ml of dichloromethane at 38 degrees C. Then drug release characteristics from the drug loaded films were examined at 37 degrees C for a minimum of 14 days in 10 ml medium (ddwater) replaced daily. Kinetics of drug release were followed by spectral measurements using previously determined lambda(max) values (GCY = 250 nm; ACY = 253 nm). A minimum of three samples was tested and reproducible results were obtained. Drug stability (ACY) during film Casting and its release was determined using 1H NMR spectrometer (Bruker DRX-500 and 400). Rate of drug release was determined from the part of the curve (rate vs. time) after the onset of the "burst." Although GCY has a larger molecular weight (255) than ACY (225), GCY exhibited about three times higher rate of release than ACY. This difference in rate values may be explained due to its relatively greater solubility in EVA, facilitating faster diffusion of the molecules through the channels present in EVA. This is consistent with the observation that the rate at which drug molecules diffuse through the channels of the Polymer, can be increased by decreasing the molecular weight. In the case of ACY, the molecules may be undergoing molecular associations, perhaps dimerization or trimerization in addition to its lower solubility in EVA. The diffusion of ACY tends to be slower under these circumstances compared to GCY resulting in lower rate value than in the case of GCY. Biological studies revealed that ACY exhibited a remarkable decrease in a number of viral organisms present in virus infected cell culture system using real-time Polymerase chain reaction (RT-PCR). NMR analysis indicates that the chemical structure of the drug remains stable during film Casting process and release.

  • drug release from cast films of ethylene vinyl acetate eva coPolymer stability of drugs by 1h nmr and solid state 13c cp mas nmr
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

Steven Offenbacher - One of the best experts on this subject based on the ideXlab platform.

  • drug release from cast films of ethylene vinyl acetate eva coPolymer stability of drugs by 1h nmr and solid state 13c cp mas nmr
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

  • Drug release from cast films of ethylene vinyl acetate (EVA) coPolymer: Stability of drugs by ^1H NMR and solid state ^13C CP/MAS NMR
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH_2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation ( E ^∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E ^∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

  • A Polymeric device for delivery of anti-microbial and anti-fungal drugs in the oral environment: effect of temperature and medium on the rate of drug release.
    Dental materials : official publication of the Academy of Dental Materials, 2003
    Co-Authors: D M Lin, S Kalachandra, J Valiyaparambil, Steven Offenbacher
    Abstract:

    The use of drug delivery systems in dentistry is a relatively new area of research with the exception of fluoride ion release from polyalkenoate cements and their predecessor silicate cements. The present study is based on the use of a bio-compatible material ethylene vinyl acetate coPolymer (EVA) that enables constant release of drugs of therapeutic levels over extended periods of time at doses suitable for the treatment of oral conditions. Polymer Casting solutions were made by dissolving EVA and the drug in the ratio of 40:1 in 70 ml of dichloromethane at 38 degrees C for 6 h. Thin square films of 3 x 3 cm2 with a thickness of 1 mm were cut from the dry sheet obtained by solvent evaporation technique. Drug loaded samples were extracted for a minimum of 14 days in 10 ml medium (double distilled water or water/ethanol (4:1)) which was replaced daily. Spectral measurements were made to follow changes in optical densities (OD) during release kinetics. Effect of temperature (24 and 37 degrees C) on the rate of drug release was studied and the energies of activation (DeltaE not equal ) were calculated using Arrehenius equation for the diffusion (translocation) of molecules of tetracycline hydrochloride (TTH), doxycycline hydrochloride (DOH), and chlorhexidine diacetate (CDA) in water as extracting medium. Effect of extracting medium (water and water/ethanol (4:1)) was also investigated on the rate of drug release measurements at 24 degrees C. Analysis of variance of the data revealed that significantly enhanced rates were observed at the higher temperature (37 degrees C) and when extracting medium was changed to water/ethanol (4:1) for TTH, DOH and CDA (p<0.0015). The enhanced rate values seem to be due to the formation of channels in the Polymer. The largest activation energy (21.83 kcal mol(-1)) observed for CDA was interpreted as due to the highest average molecular weight (626) compared to TTH (481) and DOH (481).Significance. These in vitro rate of drug release measurements will provide a basis for establishing a novel approach (treatment modality) for sustained intra-oral drug delivery over extended time periods using laboratory methods and materials that are readily available to dentists.

  • Controlled drug release for oral condition by a novel device based on ethylene vinyl acetate (EVA) coPolymer
    Journal of Materials Science: Materials in Medicine, 2002
    Co-Authors: S Kalachandra, Lin Dongming, Steven Offenbacher
    Abstract:

    The application of drug delivery systems in oral environment is relatively a new area of research with the exception of release of fluoride ions from polyalkenoate cements and their predecessor silicate cements. The present study addresses development of a novel device based on ethylene vinyl acetate coPolymer (EVA), a biocompatible material which enables constant drug release over several days to treat oral infections. Drugs incorporated in EVA included tetracycline, minocycline and nystatin together with combinations (C) of nytatin-tetracycline (1 : 1) and nystatin-minocycline (1 : 1). Polymer Casting solutions were prepared by dissolving EVA and the drugs in the ratio of 10 : 1 in 70 ml of dichloromethane at 38 °C for 6 h. Thin square films of 3×3 cm and 1 mm thickness were cut from the dry sheet obtained by solvent evaporation. Drug loaded samples were extracted for a minimum of 15 days in 10 ml medium (water or water/ethanol (1 : 2) or 0.9% saline solution) which is replaced daily. Spectral measurements were made to follow changes in optical densities (OD) during release kinetics. Analysis of the data revealed that among all the drugs tested tetracycline exhibited the highest release rate (56.15ug/cm^2/day) and % cumulative release (27.92).The observed enhanced values may be interpreted as due to the channels formed due to changes in free volume (microvoids). In case of nystatin-minocycline combination, the observed increased values of release rates and percent cumulative release, may be attributed to the swelling component or channels or relative hydrophobic interactions. Initial “burst” effects due to liberation of surface-bound drug molecules were observed with reference to all the three drugs and the combinations of drugs studied. Among all the drugs, minocycline exhibited the least “burst” effect suggesting that the drug is more homogeneously distributed in the coPolymer. Drug loaded EVA thermoplastic coPolymer may provide a favorable therapeutic material for the development of a novel, local treatment for oral, mucosal and periodontal infections.

D M Lin - One of the best experts on this subject based on the ideXlab platform.

  • Stability and release of antiviral drugs from ethylene vinyl acetate (EVA) coPolymer
    Journal of Materials Science: Materials in Medicine, 2006
    Co-Authors: S Kalachandra, D M Lin, T. Takamata, E. A. Snyder, J. Webster-cyriaque
    Abstract:

    The use of Polymer based drug delivery systems in dentistry is a relatively new area of research with the exception of the inhibition of secondary caries by the release of fluoride ions from polyalkenoate cements and their predecessors silicate cements. The present study was to test on orally biocompatible material, ethylene vinyl acetate coPolymer (EVA), for release of antiviral drugs at oral therapeutic levels over extended periods of time. We also determined their stability during film Casting and release. Materials studied include gancyclovir (GCY), acyclovir (ACY), dichloromethane (DCM), and ethylene vinyl acetate (EVA). The square films (3 × 3 × 0.1 cm) were prepared from the dry sheet obtained by solvent evaporation of Polymer Casting solutions. These solutions were made of EVA and the drug (40:1) in 70 ml of dichloromethane at 38^∘C. Then drug release characteristics from the drug loaded films were examined at 37^∘C for a minimum of 14 days in 10 ml medium (ddwater) replaced daily. Kinetics of drug release were followed by spectral measurements using previously determined λ_max values (GCY = 250 nm; ACY = 253 nm). A minimum of three samples was tested and reproducible results were obtained. Drug stability (ACY) during film Casting and its release was determined using ^1H NMR spectrometer (Bruker DRX-500 and 400). Rate of drug release was determined from the part of the curve (rate vs. time) after the onset of the “burst.” Although GCY has a larger molecular weight (255) than ACY (225), GCY exhibited about three times higher rate of release than ACY. This difference in rate values may be explained due to its relatively greater solubility in EVA, facilitating faster diffusion of the molecules through the channels present in EVA. This is consistent with the observation that the rate at which drug molecules diffuse through the channels of the Polymer, can be increased by decreasing the molecular weight. In the case of ACY, the molecules may be undergoing molecular associations, perhaps dimerization or trimerization in addition to its lower solubility in EVA. The diffusion of ACY tends to be slower under these circumstances compared to GCY resulting in lower rate value than in the case of GCY. Biological studies revealed that ACY exhibited a remarkable decrease in a number of viral organisms present in virus infected cell culture system using real-time Polymerase chain reaction (RT-PCR). NMR analysis indicates that the chemical structure of the drug remains stable during film Casting process and release.

  • Stability and release of antiviral drugs from ethylene vinyl acetate (EVA) coPolymer.
    Journal of materials science. Materials in medicine, 2006
    Co-Authors: S Kalachandra, D M Lin, T. Takamata, E. A. Snyder, J. Webster-cyriaque
    Abstract:

    The use of Polymer based drug delivery systems in dentistry is a relatively new area of research with the exception of the inhibition of secondary caries by the release of fluoride ions from polyalkenoate cements and their predecessors silicate cements. The present study was to test on orally biocompatible material, ethylene vinyl acetate coPolymer (EVA), for release of antiviral drugs at oral therapeutic levels over extended periods of time. We also determined their stability during film Casting and release. Materials studied include gancyclovir (GCY), acyclovir (ACY), dichloromethane (DCM), and ethylene vinyl acetate (EVA). The square films (3 x 3 x 0.1 cm) were prepared from the dry sheet obtained by solvent evaporation of Polymer Casting solutions. These solutions were made of EVA and the drug (40:1) in 70 ml of dichloromethane at 38 degrees C. Then drug release characteristics from the drug loaded films were examined at 37 degrees C for a minimum of 14 days in 10 ml medium (ddwater) replaced daily. Kinetics of drug release were followed by spectral measurements using previously determined lambda(max) values (GCY = 250 nm; ACY = 253 nm). A minimum of three samples was tested and reproducible results were obtained. Drug stability (ACY) during film Casting and its release was determined using 1H NMR spectrometer (Bruker DRX-500 and 400). Rate of drug release was determined from the part of the curve (rate vs. time) after the onset of the "burst." Although GCY has a larger molecular weight (255) than ACY (225), GCY exhibited about three times higher rate of release than ACY. This difference in rate values may be explained due to its relatively greater solubility in EVA, facilitating faster diffusion of the molecules through the channels present in EVA. This is consistent with the observation that the rate at which drug molecules diffuse through the channels of the Polymer, can be increased by decreasing the molecular weight. In the case of ACY, the molecules may be undergoing molecular associations, perhaps dimerization or trimerization in addition to its lower solubility in EVA. The diffusion of ACY tends to be slower under these circumstances compared to GCY resulting in lower rate value than in the case of GCY. Biological studies revealed that ACY exhibited a remarkable decrease in a number of viral organisms present in virus infected cell culture system using real-time Polymerase chain reaction (RT-PCR). NMR analysis indicates that the chemical structure of the drug remains stable during film Casting process and release.

  • drug release from cast films of ethylene vinyl acetate eva coPolymer stability of drugs by 1h nmr and solid state 13c cp mas nmr
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

  • Drug release from cast films of ethylene vinyl acetate (EVA) coPolymer: Stability of drugs by ^1H NMR and solid state ^13C CP/MAS NMR
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH_2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation ( E ^∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E ^∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

  • A Polymeric device for delivery of anti-microbial and anti-fungal drugs in the oral environment: effect of temperature and medium on the rate of drug release.
    Dental materials : official publication of the Academy of Dental Materials, 2003
    Co-Authors: D M Lin, S Kalachandra, J Valiyaparambil, Steven Offenbacher
    Abstract:

    The use of drug delivery systems in dentistry is a relatively new area of research with the exception of fluoride ion release from polyalkenoate cements and their predecessor silicate cements. The present study is based on the use of a bio-compatible material ethylene vinyl acetate coPolymer (EVA) that enables constant release of drugs of therapeutic levels over extended periods of time at doses suitable for the treatment of oral conditions. Polymer Casting solutions were made by dissolving EVA and the drug in the ratio of 40:1 in 70 ml of dichloromethane at 38 degrees C for 6 h. Thin square films of 3 x 3 cm2 with a thickness of 1 mm were cut from the dry sheet obtained by solvent evaporation technique. Drug loaded samples were extracted for a minimum of 14 days in 10 ml medium (double distilled water or water/ethanol (4:1)) which was replaced daily. Spectral measurements were made to follow changes in optical densities (OD) during release kinetics. Effect of temperature (24 and 37 degrees C) on the rate of drug release was studied and the energies of activation (DeltaE not equal ) were calculated using Arrehenius equation for the diffusion (translocation) of molecules of tetracycline hydrochloride (TTH), doxycycline hydrochloride (DOH), and chlorhexidine diacetate (CDA) in water as extracting medium. Effect of extracting medium (water and water/ethanol (4:1)) was also investigated on the rate of drug release measurements at 24 degrees C. Analysis of variance of the data revealed that significantly enhanced rates were observed at the higher temperature (37 degrees C) and when extracting medium was changed to water/ethanol (4:1) for TTH, DOH and CDA (p<0.0015). The enhanced rate values seem to be due to the formation of channels in the Polymer. The largest activation energy (21.83 kcal mol(-1)) observed for CDA was interpreted as due to the highest average molecular weight (626) compared to TTH (481) and DOH (481).Significance. These in vitro rate of drug release measurements will provide a basis for establishing a novel approach (treatment modality) for sustained intra-oral drug delivery over extended time periods using laboratory methods and materials that are readily available to dentists.

A Prakki - One of the best experts on this subject based on the ideXlab platform.

  • drug release from cast films of ethylene vinyl acetate eva coPolymer stability of drugs by 1h nmr and solid state 13c cp mas nmr
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

  • Drug release from cast films of ethylene vinyl acetate (EVA) coPolymer: Stability of drugs by ^1H NMR and solid state ^13C CP/MAS NMR
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH_2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation ( E ^∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E ^∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

E O Stejskal - One of the best experts on this subject based on the ideXlab platform.

  • drug release from cast films of ethylene vinyl acetate eva coPolymer stability of drugs by 1h nmr and solid state 13c cp mas nmr
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.

  • Drug release from cast films of ethylene vinyl acetate (EVA) coPolymer: Stability of drugs by ^1H NMR and solid state ^13C CP/MAS NMR
    Journal of Materials Science: Materials in Medicine, 2005
    Co-Authors: S Kalachandra, D M Lin, E O Stejskal, A Prakki, Steven Offenbacher
    Abstract:

    The study utilizes an oral biocompatible material based on ethylene vinyl acetate coPolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film Casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of Polymer Casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH_2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation ( E ^∗) were calculated using Arrhenius plots. Effect of EVA coPolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the Polymer. The highest E ^∗ observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film Casting process.