A systematic evaluation of the factors governing the measured thermal and mechanical property rei... more A systematic evaluation of the factors governing the measured thermal and mechanical property reinforcement in crosslinked polyethylene nanocomposites is presented.
ABSTRACT In the present work, the effective use of poly-ethylene-grafted maleic anhydride (PEg -M... more ABSTRACT In the present work, the effective use of poly-ethylene-grafted maleic anhydride (PEg -MA) copolymer as a compatibilizer in high-density polyethylene composites containing 10–50 mass% hemp fibers was evaluated through mechanical and thermal properties measurements. The results revealed a significant reinforcement on the tensile strength of the composites as a consequence of the incorporation of the compatibilizer. Less pronounced effects were found on the elongation at break and impact strength of the composites. The notable enhancement of tensile strength on the compatibilized composites was related to the improved adhesion of hemp with the matrix in the presence of PEg -MA, which was revealed through scanning electron microscopy observations. Furthermore, Fourier transform infrared spectroscopy analyses suggested that covalent bonding occurs between the fibers and the matrix in the highest PEg -MA concentrations. Differential scanning calorimetry experiments revealed that the presence of compatibilizer increases the crystallinity of the composites. Thermogravimetry studies revealed that for low compatibilizer concentrations the thermal stability of the composites is further reduced, while for the highest concentration, when bonding occurs, it is enhanced. The biodegradation studies of all the composites revealed that the incorporation of compatibilizer enhances the stability of the composites, especially in the higher concentrations, and reduces their final residue.
The aim of the present study was to experimentally examine whether poorly water-soluble drugs dis... more The aim of the present study was to experimentally examine whether poorly water-soluble drugs dispersed in a polymeric matrix exist as amorphous nanodispersions or molecularly dispersed compounds. Felodipine (Felo) dispersed in PVP matrix (solid dispersion) was used as a model drug in this study. Drug/polymer ratios have an impact on the drug average particle size, morphology and dissolution profile while solid dispersions containing up to 50wt% Felo are completely amorphous. SEM, TEM micrographs, and micro-Raman mapping reveal that Felo is dispersed in the form of nanoparticles into the PVP matrix. Due to the high spatial resolution of TEM, it was established that these nanoparticles are not uniform particles, but rather agglomerates of individual particles with sizes smaller than 5-10nm. Moreover, micro-Raman mapping allowed us to observe the size and spatial distribution of domains where the drug existed as molecularly or nanodispersed. Experimental evidence presented in this wor...
Recent Patents on Drug Delivery & Formulation, 2007
Nowadays, pharmaceutical technology and research for new drugs and formulations is of great impor... more Nowadays, pharmaceutical technology and research for new drugs and formulations is of great importance, as scientists attempt to discover even more revolutionary and efficient methods to treat various diseases. At the same time the correct dosing and site targeting are equally important for clinical success. Research in sustained drug release systems is very promising towards such a direction, while it offers advantages and potential rewards contrary to traditional therapy. The drug plasma concentrations remain inside the therapeutic range for a longer time period compared to the conventional formulations. In addition, sustained release formulations may increase the likelihood for the patient to respond to the therapy, since drug formulations are generally characterized by one daily given dose. The rate at which a drug is released from a sustained-release formulation depends upon many factors, while excipients play the most important role. Most sustained release formulations are based on biodegradable polymers in the form of a drug-encapsulating matrix or membrane. Examples range from monolithic devices, polymer-coated capsules and implant devices, hydrogels, to injectable systems based on suspensions of micro-, nanospheres or polymer solutions. The advantages and disadvantages of these different formulation systems are being extensively discussed in the present review.
Hydrophilic matrices or hydrocolloids are polymers which swell on contact with aqueous solutions ... more Hydrophilic matrices or hydrocolloids are polymers which swell on contact with aqueous solutions and dissolve slowly from the surface forming a gel mass. Several studies have been carried out in the past few years on the use of hydro-colloids in controlled release formulations. The present study used three modified celluloses, carboxymethyl cellulose sodium, hydroxyethyl cellulose (HEC), and hydroxypro-pylmethyl cellulose (HPMC)
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2000
The most widely-used inorganic pigments of Byzantine and post-Byzantine hagiography are earth pig... more The most widely-used inorganic pigments of Byzantine and post-Byzantine hagiography are earth pigments called ochres such as, red and yellow ochres, limonite, goethite, raw and burnt sienna, caput mortuum and hematite. The present experimental work proposes a technique of differentiation that allows one to distinguish among all the different kinds of iron oxides, thereby providing a better understanding of the painting technique used on portable icons and wall paintings. The ratios between the main spectroscopic peaks, attributable to the major components usually present in ochres, were calculated and compared, one against the another, from the spectra obtained through micro-Raman spectroscopy. Elementary composition is also revealed through a scanning electron microscopy (SEM) analysis. The possibility for detailed study on a particular Byzantine ochre palette can thus be performed based on the small differences in its nature and composition. These differences can first be observed and then measured among all of the natural earth pigments, through microRaman and microFTIR spectroscopies.
ABSTRACT In this work, the enhancement of drug dissolution rate through the preparation of new fo... more ABSTRACT In this work, the enhancement of drug dissolution rate through the preparation of new formulations containing Nimodipine in molecular level dispersion or in nanodispersion into poly(vinyl pyrrolidone) (PVP) matrix, was investigated. Differential scanning calorimetry (DSC) and modulated-temperature differential scanning calorimetry (MTDSC) in combination with X-ray powder diffractometry (XRPD) and scanning electron microscopy (SEM) studies showed that Nimodipine was amorphous in solid dispersions of 10 or 20 mass%, and mainly dispersed on a molecular level. This behaviour is attributed to the strong interactions taking place between the amine group of Nimodipine and carbonyl group of PVP. At higher drug loadings, crystal reflections in XRPD patterns and melting peaks of Nimodipine in DSC traces, indicated presence of drug in crystalline form. Micro-Raman studies in combination with SEM micrographs showed that the mean particle size increases with drug content in the formulations, up to 10 μm. Moreover, both XRPD patterns and micro-Raman spectra seem to indicate that Nimodipine crystallized in a second, thermodynamically stable, crystal modification II. The physicochemical characteristics of Nimodipine and the particle size distribution directly affect the dissolution rate enhancement, which is higher in amorphous dispersions.
A systematic evaluation of the factors governing the measured thermal and mechanical property rei... more A systematic evaluation of the factors governing the measured thermal and mechanical property reinforcement in crosslinked polyethylene nanocomposites is presented.
ABSTRACT In the present work, the effective use of poly-ethylene-grafted maleic anhydride (PEg -M... more ABSTRACT In the present work, the effective use of poly-ethylene-grafted maleic anhydride (PEg -MA) copolymer as a compatibilizer in high-density polyethylene composites containing 10–50 mass% hemp fibers was evaluated through mechanical and thermal properties measurements. The results revealed a significant reinforcement on the tensile strength of the composites as a consequence of the incorporation of the compatibilizer. Less pronounced effects were found on the elongation at break and impact strength of the composites. The notable enhancement of tensile strength on the compatibilized composites was related to the improved adhesion of hemp with the matrix in the presence of PEg -MA, which was revealed through scanning electron microscopy observations. Furthermore, Fourier transform infrared spectroscopy analyses suggested that covalent bonding occurs between the fibers and the matrix in the highest PEg -MA concentrations. Differential scanning calorimetry experiments revealed that the presence of compatibilizer increases the crystallinity of the composites. Thermogravimetry studies revealed that for low compatibilizer concentrations the thermal stability of the composites is further reduced, while for the highest concentration, when bonding occurs, it is enhanced. The biodegradation studies of all the composites revealed that the incorporation of compatibilizer enhances the stability of the composites, especially in the higher concentrations, and reduces their final residue.
The aim of the present study was to experimentally examine whether poorly water-soluble drugs dis... more The aim of the present study was to experimentally examine whether poorly water-soluble drugs dispersed in a polymeric matrix exist as amorphous nanodispersions or molecularly dispersed compounds. Felodipine (Felo) dispersed in PVP matrix (solid dispersion) was used as a model drug in this study. Drug/polymer ratios have an impact on the drug average particle size, morphology and dissolution profile while solid dispersions containing up to 50wt% Felo are completely amorphous. SEM, TEM micrographs, and micro-Raman mapping reveal that Felo is dispersed in the form of nanoparticles into the PVP matrix. Due to the high spatial resolution of TEM, it was established that these nanoparticles are not uniform particles, but rather agglomerates of individual particles with sizes smaller than 5-10nm. Moreover, micro-Raman mapping allowed us to observe the size and spatial distribution of domains where the drug existed as molecularly or nanodispersed. Experimental evidence presented in this wor...
Recent Patents on Drug Delivery & Formulation, 2007
Nowadays, pharmaceutical technology and research for new drugs and formulations is of great impor... more Nowadays, pharmaceutical technology and research for new drugs and formulations is of great importance, as scientists attempt to discover even more revolutionary and efficient methods to treat various diseases. At the same time the correct dosing and site targeting are equally important for clinical success. Research in sustained drug release systems is very promising towards such a direction, while it offers advantages and potential rewards contrary to traditional therapy. The drug plasma concentrations remain inside the therapeutic range for a longer time period compared to the conventional formulations. In addition, sustained release formulations may increase the likelihood for the patient to respond to the therapy, since drug formulations are generally characterized by one daily given dose. The rate at which a drug is released from a sustained-release formulation depends upon many factors, while excipients play the most important role. Most sustained release formulations are based on biodegradable polymers in the form of a drug-encapsulating matrix or membrane. Examples range from monolithic devices, polymer-coated capsules and implant devices, hydrogels, to injectable systems based on suspensions of micro-, nanospheres or polymer solutions. The advantages and disadvantages of these different formulation systems are being extensively discussed in the present review.
Hydrophilic matrices or hydrocolloids are polymers which swell on contact with aqueous solutions ... more Hydrophilic matrices or hydrocolloids are polymers which swell on contact with aqueous solutions and dissolve slowly from the surface forming a gel mass. Several studies have been carried out in the past few years on the use of hydro-colloids in controlled release formulations. The present study used three modified celluloses, carboxymethyl cellulose sodium, hydroxyethyl cellulose (HEC), and hydroxypro-pylmethyl cellulose (HPMC)
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2000
The most widely-used inorganic pigments of Byzantine and post-Byzantine hagiography are earth pig... more The most widely-used inorganic pigments of Byzantine and post-Byzantine hagiography are earth pigments called ochres such as, red and yellow ochres, limonite, goethite, raw and burnt sienna, caput mortuum and hematite. The present experimental work proposes a technique of differentiation that allows one to distinguish among all the different kinds of iron oxides, thereby providing a better understanding of the painting technique used on portable icons and wall paintings. The ratios between the main spectroscopic peaks, attributable to the major components usually present in ochres, were calculated and compared, one against the another, from the spectra obtained through micro-Raman spectroscopy. Elementary composition is also revealed through a scanning electron microscopy (SEM) analysis. The possibility for detailed study on a particular Byzantine ochre palette can thus be performed based on the small differences in its nature and composition. These differences can first be observed and then measured among all of the natural earth pigments, through microRaman and microFTIR spectroscopies.
ABSTRACT In this work, the enhancement of drug dissolution rate through the preparation of new fo... more ABSTRACT In this work, the enhancement of drug dissolution rate through the preparation of new formulations containing Nimodipine in molecular level dispersion or in nanodispersion into poly(vinyl pyrrolidone) (PVP) matrix, was investigated. Differential scanning calorimetry (DSC) and modulated-temperature differential scanning calorimetry (MTDSC) in combination with X-ray powder diffractometry (XRPD) and scanning electron microscopy (SEM) studies showed that Nimodipine was amorphous in solid dispersions of 10 or 20 mass%, and mainly dispersed on a molecular level. This behaviour is attributed to the strong interactions taking place between the amine group of Nimodipine and carbonyl group of PVP. At higher drug loadings, crystal reflections in XRPD patterns and melting peaks of Nimodipine in DSC traces, indicated presence of drug in crystalline form. Micro-Raman studies in combination with SEM micrographs showed that the mean particle size increases with drug content in the formulations, up to 10 μm. Moreover, both XRPD patterns and micro-Raman spectra seem to indicate that Nimodipine crystallized in a second, thermodynamically stable, crystal modification II. The physicochemical characteristics of Nimodipine and the particle size distribution directly affect the dissolution rate enhancement, which is higher in amorphous dispersions.
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