Fourier Transform Infrared Spectroscopy Studies Research Articles

Characterization of Mn-Doped Co3O4 Thin Films Prepared by Sol Gel-Based Dip-Coating Process

Abstract In this article, manganese-doped cobalt oxide (Mn-doped Co3O4) thin films have been prepared on glass substrates using sol gel-based dip-coating technique in order to investigate their optical, structural and electrical properties. The Mn concentration was changed from 0 % to 9 %. The synthesized samples were characterized by ultraviolet-visible spectroscopy (UV-visible), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and complex impedance spectroscopy to elucidate the optical, structural, vibrational and electrical properties. Our optical results show that the transmittance of Mn-doped Co3O4 films decreases with increasing doping levels. The optical band gaps were found to be ( E g 1 = 1.51 e V , E g 2 = 2.12 e V ) ({E_{g1}} = 1.51{\ }eV, {E_{g2}} = 2.12{\rm{ eV}}) and ( E g 1 = 1.23 e V , E g 2 = 1.72 e V ) ({E_{g1}} = 1.23{\ }eV, {E_{g2}} = 1.72{\rm{ eV}}){\ } for the case of undoped Co3O4 and 9 % Mn-doped Co3O4, respectively. This shift means that the impurities would create energy levels. The structural analysis provides evidence that obtained powders were crystallized in cubic spinel structure. The complementary phase information is provided by FTIR spectroscopy. The FTIR study depicted the presence of four distinct bands characterizing Mn-doped Co3O4 cubic spinel-type structure. The Nyquist plots suggest that the equivalent circuit of Mn-doped Co3O4 films is an RpCp parallel circuit. It was found that the effective resistance Rp decreases, whereas the effective capacitance Cp increases with doping.

ENHANCEMENT OF THE SOLUBILITY AND THE DISSOLUTION RATE OF CANDESARTAN CILEXETIL USING MICROSPONGE TECHNOLOGY

Objective: The aim of the present study is to enhance the dissolution rate of candesartan cilexetil (CC) using microsponges. Candesartan is therapeutically a potent antihypertensive agent, but it suffers a major drawback of poor oral bioavailability, which is estimated to be 15% due to its low solubility in the gastrointestinal fluids and hepatic first-pass metabolism.Methods: Eudragit-based microsponges were prepared by quasi-emulsion solvent diffusion method using different drug–polymer ratios (1:1 to 1:6), stirring speeds (250–750 rpm), and emulsifier concentrations (polyvinyl alcohol) (0.05%–0.083% w/v). Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) study for CC, physical mixtures of drug–polymer, and selected formula were investigated to estimate compatibility of CC with other used ingredients. All formulations were evaluated for particle size, production yield, and loading efficiency. The in vitro drug release study of optimized formulation was performed in phosphate buffer pH 6.8.Results: The obtained results indicated that formula F3 which contains eudragit RS100 at drug:polymer ratio (6:1) was showed the smallest particle size with higher production yield and loading efficiency. DSC and FTIR study of the physical mixtures of drug and polymer revealed no drug–polymer interaction. The results clearly confirm that the percentage of CC released at 30 min from F3, CC powder, and self-made tablet was 54%, 20.325, and 38.9%, respectively.Conclusion: Microsponges technique was considered as a promising system to enhance the solubility and dissolution rate of poor-water soluble CC.

Amyloid-β fibrils assembled on ganglioside-enriched membranes contain both parallel β-sheets and turns

Some protein and peptide aggregates, such as those of amyloid-β protein (Aβ), are neurotoxic and have been implicated in several neurodegenerative diseases. Aβ accumulates at nanoclusters enriched in neuronal lipids called gangliosides in the presynaptic neuronal membrane, and the resulting oligomeric and/or fibrous forms accelerate the development of Alzheimer's disease. Although the presence of Aβ deposits at such nanoclusters is known, the mechanism of their assembly and the relationship between Aβ secondary structure and topography are still unclear. Here, we first confirmed by atomic force microscopy that Aβ40 fibrils can be obtained by incubating seed-free Aβ40 monomers with a membrane composed of sphingomyelin, cholesterol, and the ganglioside GM1. Using Fourier transform infrared (FTIR) reflection-absorption spectroscopy, we then found that these lipid-associated fibrils contained parallel β-sheets, whereas self-assembled Aβ40 molecules formed antiparallel β-sheets. We also found that the fibrils obtained at GM1-rich nanoclusters were generated from turn Aβ40 Our findings indicate that Aβ generally self-assembles into antiparallel β-structures but can also form protofibrils with parallel β-sheets by interacting with ganglioside-bound Aβ. We concluded that by promoting the formation of parallel β-sheets, highly ganglioside-enriched nanoclusters help accelerate the elongation of Aβ fibrils. These results advance our understanding of ganglioside-induced Aβ fibril formation in neuronal membranes and may help inform the development of additional therapies for Alzheimer's disease.

Study on the Catalytic Effect of Nitric Acid Activated Myanmar Natural Clay for the Degradation of Plastic Wastes

In this study, the performance of different acid treated Myanmar Natural Clay (Mabisian) was conducted the pyrolysis of mixed plastic wastes, 40% high density polyethylene, 30% polypropylene, 25% low density polyethylene and 5% polystyrene. Mabisian clay was refluxed with different concentration of nitric acid (2M, 4M, 6M, 8M, 10M, 12M and 14M) at 100ºC for 3hrs followed by calcination at 500ºC for 1hr. The physico-chemical characteristics of resulted leached clay were studied by X-Ray Fluoresence spectroscopy (XRF), X-Ray Diffraction (XRD) and Fourier Transformed Infrared Spectroscopy (FTIR). The pyrolytic oil was characterized by Gas Chromatography – mass spectopy (GC-MS). XRF and FTIR studies indicated that acid treatment under reflux condition lead to the removal of octahedral Al3+ cations along with other impurities. The chemical treatment increased the Si/Al ratio. The maximum liquid yield (75%) was obtained at 12 M nitric acid, 3hr reaction time and 100 º C reaction temperatures. In addition, the percent peak area of gasoline range hydrocarbon was obtained 55.6% at optimum condition. Thus, the treated clay can be used as promising as catalyst support.

Study on the Catalytic Effect of Nitric Acid Activated Myanmar Natural Clay for the Degradation of Plastic Wastes

In this study, the performance of different acid treated Myanmar Natural Clay (Mabisian) was conducted the pyrolysis of mixed plastic wastes, 40% high density polyethylene, 30% polypropylene, 25% low density polyethylene and 5% polystyrene. Mabisian clay was refluxed with different concentration of nitric acid (2M, 4M, 6M, 8M, 10M, 12M and 14M) at 100ºC for 3hrs followed by calcination at 500ºC for 1hr. The physico-chemical characteristics of resulted leached clay were studied by X-Ray Fluoresence spectroscopy (XRF), X-Ray Diffraction (XRD) and Fourier Transformed Infrared Spectroscopy (FTIR). The pyrolytic oil was characterized by Gas Chromatography – mass spectopy (GC-MS). XRF and FTIR studies indicated that acid treatment under reflux condition lead to the removal of octahedral Al3+ cations along with other impurities. The chemical treatment increased the Si/Al ratio. The maximum liquid yield (75%) was obtained at 12 M nitric acid, 3hr reaction time and 100 º C reaction temperatures. In addition, the percent peak area of gasoline range hydrocarbon was obtained 55.6% at optimum condition. Thus, the treated clay can be used as promising as catalyst support.

Nanocellulose mediated injectable bio-nanocomposite hydrogel scaffold-microstructure and rheological properties

Here we report, for the first time, development of nanocellulose based novel bio-nanocomposite injectable hydrogel scaffold. An integrated approach has been used to incorporate ultrafine fluorcanasite (FC) glass-ceramic particulates within nanocellulose matrix, synthesized from lignocellulosic biomass. Epichlorohydrin (ECH) was used as a chemical cross-linking agent for hydrogel synthesis. The compositions and properties of bio-nanocomposite hydrogels were controlled by varying the loading of FC and ECH. Moreover, microstructural characterizations and functional group analysis of synthesized nanocellulose and bio-nanocomposite hydrogels were carried out using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). SEM studies revealed successful extraction of cellulosic nanofibres and interconnected porous micro-architecture of injectable hydrogels. Incorporation of FC particulates resulted into development of well-defined micro-porous morphology. FT-IR studies indicated the presence of hydroxyl groups and possible interactions between nanocellulose and FC reinforcements. The rheological study of the developed injectable hydrogel was carried out at different frequency, amplitude and temperature sweeps. The studies revealed that after the incorporation of FC, dynamic storage modulus increased, while synergistically enhancing the injectability of the bio-nanocomposite hydrogels. An optimum loading level of FC reinforcement could also be established. Swelling behaviour studies of the hydrogels demonstrated higher degree of swelling and enhanced structural integrity with incorporation of FC. The novel bio-nanocomposite injectable hydrogels developed in this study, could demonstrate promising potential as injectable implant material.

Effect of ion trapping behavior of TiO2 nanoparticles on different parameters of weakly polar nematic liquid crystal

In the present investigation, TiO2-doped weakly polar nematic liquid crystal (NLC) has been studied. This study mainly focuses on dielectric, electro-optical and optical properties of pure NLC and doped systems. Variation in different parameters like dielectric permittivity, dielectric loss, dielectric anisotropy and conductivity has been noticed. Permittivity of the doped system is almost the same as undoped system. With doping concentration, the ionic contribution to the dielectric loss as observed in low-frequency region has been suppressed and the shift in relaxation frequency toward higher frequency side has also been observed. The electrical conductivity and threshold voltage have been decreased with increasing concentration of nanoparticles (NPs). The continuous increase in dielectric anisotropy with increasing the concentration of NPs has also been observed. These results have been attributed to the trapping capability of free ions by TiO2 NPs. Further, we focused on the study of photoluminescence (PL), UV absorbance and Fourier transformed infrared spectroscopy (FTIR) of pure and doped systems. The continuous increase in PL intensity without any shift in emission peak has been observed for doped systems. Enhancement in UV absorbance with increasing concentration of NPs has also been observed. The effect of NPs doping on molecular dynamics of NLC can be clearly seen by FTIR study. The results suggest that the TiO2 NP-doped weakly polar NLC can have significant improved dielectric, electro-optical and optical properties. This makes the weakly polar NLC to be a potential candidate for many applications.

Characterization of the binding of triprolidine hydrochloride to hen egg white lysozyme by multi-spectroscopic and molecular docking techniques

The interaction between triprolidine hydrochloride (TRP), a strong histamine H1-receptor antagonist and hen egg white lysozyme (HEWL) was investigatied by UV–vis, fluorescence, Förster's resonance energy transfer (FRET), circular dichroism (CD), Fourier transform infrared (FTIR) and molecular docking studies. The steady state fluorescence study shows that TRP quenches the intrinsic fluorescence of HEWL through a static quenching mode which also supported by UV–vis absorption study. The binding constant Kb was 2.31 × 104 M−1 and binding stoichiometry (n) was approximately one. The synchronous fluorescence spectroscopy showed that the binding of TRP changed the microenvironment around Trp and Tyr residue to a more hydrophilic region. The FRET analysis established that there is energy transfer from HEWL to TRP. The decreased α-helical content of HEWL on interaction with TRP indicated that TRP destabilized the native structure of HEWL. The alterations in the secondary structure of HEWL in presence of TRP is also revealed by 3D fluorescence and FTIR spectroscopic studies. In addition, molecular docking was performed to confirm the binding site of TRP on HEWL, mode of binding and amino acids involved in this binding. This study will provide an insight into the molecular basis of the interaction between HEWL and TRP at pharmacological level and highlights its significance in the clinical medicine.

DESIGN, FORMULATION, AND CHARACTERIZATION OF LIPOSOMAL-ENCAPSULATED GEL FOR TRANSDERMAL DELIVERY OF FLUCONAZOLE

Objectives: The present objective for the study was to prepare proliposomal gel bearing an antifungal agent, fluconazole (FLZ) intended for topical application.Methods: Various proliposome formulations were prepared using thin-film hydration technique by varying the lipid phase composition (phosphatidylcholine/cholesterol). Proliposome formulations were characterized for vesicle size, vesicle size distribution, vesicle morphology, drug content, entrapment efficiency, percentage yield value, storage stability analysis, Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), in vitro diffusion study, release kinetic studies, and antifungal activity. Topical proliposomal gels were prepared by incorporation of lyophilized proliposome into a structured vehicle carbopol 934 (2.5%).Results: A spherical shape of reconstituted FLZ liposome with an average vesicle about 5–8 μm was observed in photomicrographs. The percentage entrapment of drug was increased with increase in phospholipid composition in the range of 55.13–69.61%. The FTIR and DSC studies showed no possible drug-excipient interaction. Proliposomal gel showed the prolonged release of FLZ than the lyophilized liposomes. The release kinetic values of regression coefficients confirmed the diffusion-dependent release of the drug. Stability studies indicated that product is stable and should be stored at low temperature.Conclusion: The proposed FLZ proliposomal gel showed sustained release with enhanced antifungal activity implicating its potential in effective transdermal delivery for the topical pharmacotherapy.

Synthesis and Characterization of Alginate Encapsulated Zirconium-Based Ferromagnetic Sorbent for Adsorptive Removal of Dyes

This paper provides insight on the removal of dyes from water using magnetic separation technique. A new alginate encapsulated zirconium-based encapsulated ferromagnetic sorbent has been synthesized by co-precipitation and electrostatic extrusion techniques. The ferromagnetic sorbent has the alginate as outer polymeric shell and zirconium-based iron oxides as inner ferromagnetic cores. The sorbent has the multi-functional properties as it is can be easily separated using external magnetic force, and effective in adsorptive removal of congo red, methyl violet, and methylene blue dyes. The sorbent was characterized by particle size analyser, Scanning Electron Microscope (SEM), Thermal Gravimetric-Differential Thermal Analyzer (TG-DTA), and Fourier Transform Infrared Spectroscopy (FT-IR). Adsorption assays were performed in batch using methyl violet, methylene blue, and congo red dyes as contaminants. The alginate encapsulated zirconium-based ferromagnetic sorbent was a potential candidate for removal of dyes under a magnetic field as separating agent. The present investigation demonstrates the ferromagnetic sorbent exhibiting good performance to remove the methyl violet, congo red, and methylene blue dyes from aqueous solutions. The adsorption experiments reveal that the adsorption performance is higher for the cationic dye than the anionic dye. The SEM and FT-IR studies show that the interaction characteristics between the dyes and the ferromagnetic sorbent where the surface of the ferromagnetic sorbent became smoother and less porous when the metal-O group (Zr-O and Fe-O) of the ferromagnetic sorbent attaches to the dye.

Preparation and Characterization of MgO Nanoparticles by Sol–Gel Method

Liquid phase method (sol–gel method) was employed to synthesize MgO nanparticles. The particles were subjected to structural, morphological and optical property studies. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform Infrared Spectroscopy (FT-IR), UV-Vis Spectrophotometer were employed to characterize the given sample. The X-ray pattern obtained had no impurity peak, revealing high purity of the sample. The particle size and morphology were investigated by SEM. EDS and FT-IR studies were done for knowing the composition and surface passivation respectively of the prepared sample. The estimation of the band-gap was carried out by UV-vis absorption spectra.

Influence of cobalt substitution on structural, optical, electrical and magnetic properties of nanosized lithium ferrite

A series of Co2+ substituted Li0.5CoxFe2.5−xO4 (x = 0.1, 0.3, 0.5) has been prepared by a citrate precursor method. The distribution of cations on A-site and B-site was studied by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Mossbauer Spectroscopy. XRD confirmed the formation of ordered α-phase with prominent peaks at (220), (311), (400), (422), (511), (440). SEM and TEM confirmed the homogeneous formation of cubic phase with an average crystallite size of 50 nm. From FTIR studies, the bands at 603.78, 606.14 and 610.08 cm−1 confirmed the formation of Fe3+–O2− bond at tetrahedral (A-site), whereas bands at 477.25, 474.84 and 471.69 cm−1 confirmed the formation of Fe3+–O2− bond at octahedral site (B-site); shifting in frequency was observed with an increased amount of cobalt doping. Further, Raman spectra revealed the distribution of cations at tetrahedral and octahedral site by means of modes A1g, T2g, Eg. Mossbauer spectra with two magnetic sextets confirmed two different environments of Fe3+ ions. With an increase in cobalt doping, the crystallite size was observed to increase and hence an increase in relative area B/A ratio confirming the occupancy of Co2+ at B-site. The temperature dependence of DC resistivity was found to decrease with an increase in temperature. With an increase in cobalt substitution, DC resistivity was observed to increase from 2.32 × 106 to 3.46 × 107 Ω cm. A decrease in activation energy is noticed in the present investigation and this observed semiconducting behavior makes these nanomaterials suitable in NTC (negative temperature coefficient) devices. These observations were explained on various models and theories.

Thermal degradation of high-impact polystyrene with pro-oxidant additives

The oxo-degradation process of high-impact polystyrene (HIPS) with 0, 1.5 and 3% w/w of pro-oxidant d2w® was studied. The degradation was conducted in a convection oven employing temperatures of 50, 55, 60 and 65 °C. The process was monitored by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile tests (i.e., strain at break). Neat HIPS samples did not exhibit significant changes for all conditions evaluated. Samples with oxo-additive exhibited a complex behavior in relation to the rate of degradation; HIPS with 1.5% oxo-additive exhibited faster degradation than samples with 3% oxo-additive at temperatures of 50 and 55 °C, but no significant differences at 60 and 65 °C. FTIR studies showed the evolution of hydroxyl and carbonyl functional groups during degradation and allowed to infer that polybutadiene phase is degraded preferentially. A complete loss of mechanical properties of samples with pro-oxidant was observed with changes occurring faster as temperature increased. Tensile and DSC tests were the most effective techniques for monitoring the degree of decomposition of HIPS, since the results obtained evidenced early structural changes during thermal aging that were undetected by FTIR and TGA at identical exposure times.

FTIR and DSC Studies of Binary Mixtures of Long-Chain Aliphatic Compounds: Lauric Acid – Cetyl-trimethylammonium Bromide

Structural and thermal properties of a solid-state binary mixture of long-chain cationic and anionic surfactants (so-called catanionic complexes) composed of cetyltrimethyl-ammonium bromide, [H3C–(CH2)15–N+(CH3)3]Br−(CTAB), and saturated fatty acid (FA), CH3(CH2)12COOH (lauric acid, kC12), are studied. To clarify the effect of intermolecular interactions on the crystalline structure and phase transitions in this class of supramolecular compounds, the 1 : 1 kC12-CTAB binary mixture is investigated by means of X-ray diffraction, differential scanning calorimetry (DSC), and temperature-variable Fourier transform infrared spectroscopy (FTIR). Based on the comparison of the obtained results with those of other CTAB-FA binary mixtures with different alkyl chain length mismatches, the possible molecular packing in the crystal phase of CTAB-FA complexes and the mechanism of successive phase transitions in the condensed state are proposed.

PREPARATION AND EVALUATION OF DROTAVERINE HCL ORAL DISINTEGRATING TABLETS USING SOLID MIXTURE TECHNIQUE

Objective: The objective of this study is to formulate orally disintegrating taste masked tablets of drotaverine HCl using solid mixture technique.Methods: Taste masked drug-polymer solid mixtures of drotaverine HCl were prepared by using hydroxypropyl methylcellulose (HPMC) 3 cps and rxcipient® FM1000/calcium silicate (rxcipient) as carriers employing kneading method using varying drug-polymer ratios of 1:1, 1:5, 1:7.5, and 1:9. Prepared drug-polymer mixtures evaluated for taste masking, and the ratio of drug-polymer is optimized. The granules and tablets prepared with optimized drug-polymer ratio were evaluated for pre- and post-compression parameters, in vitro dissolution studies, Fourier-transformation infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD) studies.Results: The drug:polymer ratios 1:7.5 with rxcipient and 1:9 with HPMC were optimized based on taste evaluation. The pre-compression results showed that all the formulae have good flow properties. The post-compression evaluations showed that all the formulae met the specifications of orally disintegrating tablets. From all the prepared taste masked drotaverine HCl tablets, R10 formulation consisting of 4% croscarmellose sodium and H9 formulation consisting of 3% croscarmellose sodium, 3% sodium starch glycolate, and 2% microcrystalline cellulose shown more than 99% drug release in 60 min, and both the formulations showed better taste masking and were meting oral disintegrating tablet (ODT) parameters. The optimized formulation was characterized by FTIR, DSC, and XRD studies and found no incompatibility.Conclusion: The results demonstrated that the prepared drotaverine HCl ODT showed better taste masking and meeting the parameters of ODT formulations R10 and H9. The present solid mixture technique can be effectively used for taste masking.

ISOLATION OF A COMPOUND FROM THE BULBS OF ELEUTHERINE BULBOSA (MILLER) URBAN (IRIDACEAE)

Objective: The present study is concerned with the detection, isolation, identification, and structural elucidation of the bioactive phytochemical from the bulbs of Eleutherine bulbosa.Methods: Ethyl acetate is the solvent used in Soxhlet extraction. Column chromatography and thin layer chromatography is employed in the isolation procedure. Identification and structural elucidation of the bioactive compound is determined using ultraviolet-visible (UV-vis), Fourier transform-infrared (FTIR) spectroscopy, liquid chromatography–mass spectrometry (LCMS-MS), and 1H nuclear magnetic resonance (1HNMR) spectroscopy.Results: A compound was isolated from the bulbs of E. bulbosa by solvent extraction and chromatography. UV-vis, FTIR spectroscopy, LCMS-MS, and 1HNMR studies showed that the isolated compound was bis (2-6,7-diamino-5,8-dioxo naphthalene-1yl) propanal.Conclusion: An yellowish-brown crystalline needle-shaped compound was isolated from the bulbs of E. bulbosa and characterized chemically. Spectroscopic analysis identified the compound as bis (2-6,7-diamino-5,8-dioxo naphthalene-1yl) propanal. Mass of the compound is m/z 244 (MH+=245).

PREPARATION, CHARACTERISATION AND EVALUATION OF ROPINIROLE HYDROCHLORIDE LOADED CONTROLLED RELEASE MICROSPHERES USING SOLVENT EVAPORATION TECHNIQUE

Objective: The major objective of the research work was to design, characterise and evaluate controlled release microspheres of ropinirole hydrochloride by using non-aqueous solvent evaporation technique to facilitate the delivery of the drug at a predetermined rate for a specific period of time.Methods: Ropinirole hydrochloride microspheres were prepared by using different low-density polymers such as eudragit RL 100, eudragit RS 100 and ethylcellulose either alone or in combination with the help of non-aqueous solvent evaporation technique. All the formulated microparticles were subjected to various evaluation parameters such as particle size analysis, micrometric properties, drug entrapment efficiency, percentage drug loading, percentage yield and in vitro drug release study. The compatibility of the drug and polymers was confirmed by physical compatibility study, fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and x-ray diffraction study (XRD). The formation of the most optimized batch of the microsphere (F12) was confirmed by scanning electron microscopy (SEM), DSC, FTIR, and XRD. In vitro drug release study and in vitro drug release kinetics study of the formulated microspheres were also carried out.Results: Drug-polymer compatibility studies performed with the help of FTIR and DSC indicated that there were no interactions. Results revealed that non-aqueous solvent evaporation technique was a suitable technique for the preparation of microspheres as most of the formulations were discrete, free-flowing and spherical in shape with a good yield of 55.67% to 80.09%, percentage drug loading of 35.52% to 94.50% and percentage drug entrapment efficiency of 36.24% to 95.07%. Different drug-polymer ratios, as well as the combination of polymers, played a significant role in the variation of over-all characteristics of formulations. Based on the data of various evaluation parameters such as particle size analysis, percentage drug loading, percentage drug entrapment, percentage yield, rheological studies and in vitro drug release characteristics, formulation F12 was found to fulfil the criteria of ideal controlled release drug delivery system. F12 showed controlled release till the 14th hour (97.99%) and its in vitro release kinetics was best explained by zero-order kinetics and followed Korsemeyer-Pappas model (Non-Fickian mechanism). SEM of F12 revealed the formation of spherical structures. The FTIR study of F12 confirmed the stable nature of ropinirole in the drug-loaded microspheres. DSC and XRD patterns showed that ropinirole hydrochloride was dispersed at the molecular level in the polymer matrix.Conclusion: The controlled release microparticles were successfully prepared and from this study, it was concluded that the developed microspheres of ropinirole hydrochloride can be used for controlled drug release to improve the bioavailability and patient compliance and to maintain a constant drug level in the blood target tissue by releasing the drug in zero order pattern.

Physicochemical characteristics of organophilic clays prepared using two organo-modifiers: alkylammonium cation arrangement models

The clay was modified by an ion exchange reaction with cetylpyridinium chloride CPC and hexadecyltrimethylammonium bromide HDTMA. The modified samples were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The basal spacing of unmodified clay determined by XRD was 12.72 Å and, after modification, increased with increasing concentration; expressed as a function of the cation exchange capacity (CEC) of the clay; to reach 21.08 and 26 Å for clays modified with CPC and HDTMA successively for an equal concentration of 3CEC. FTIR studies revealed structural differences between modified and unmodified clay samples. Modified clay spectra showed C–N functional bands (1480 cm−1) and C–H vibrations (near 2936 and 2871 cm−1). The results of the SEM study reveal a difference between natural and modified clays. The purified clay has massive and curved plates. However, the modified clays show numerous small aggregate particles and plaques that become relatively flat. The arrangement of surfactants in clay is rather complicated. It depends on the nature of the surfactant molecules, the CEC of the clay and the method of preparation. According to these parameters, the inserted surfactants may be arranged in monolayer, paraffinic or admicelles structures.

Effect of silicone oil on the microstructure, gelation and rheological properties of sorbitan monostearate–sesame oil oleogels

Oleogels contain oil or a non-polar liquid which is gelled with an agent called an organogelator. The aim of this study was to evaluate the effects of the addition of silicone oil (cyclopentasiloxane) to the gelation process and to the properties of sorbitan monostearate (SMS)–sesame oil oleogel and compared with that of SMS–sesame oil oleogel and SMS–cyclopentasiloxane oleogel. Three different oil phases; sesame oil phase, cyclopentasiloxane phase and a mixture of cyclopentasiloxane and sesame oil, were used to prepare oleogels with SMS gelator. The critical gelling concentrations (CGC) for oleogels were determined using different concentration of SMS in a range of 5%–22% (w/w). The characterization of the developed oleogels was done using Fourier transform infrared spectroscopy (FTIR), polarized light microscope, rheometer, X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The addition of cyclopentasiloxane reduced the CGC of SMS–sesame oil oleogel from 20% to 10% (w/w). In microscopic characterization, the oleogels with a mixture of oil phases showed the longer and thicker three-dimensional gel network than that of oleogels with sesame oil and cyclopentasiloxane. FTIR studies demonstrated that this network formation was mainly due to hydrogen bonding. Rheological measurements revealed that the combination of cyclopentasiloxane and sesame oil produced strong gel with higher complex modulus values and longer linear viscoelastic region than oleogels prepared with sesame oil and cyclopentasiloxane. In addition, oleogels with the combination of the two oils had higher enthalpy (ΔHm) and entropy (ΔSm) thus could increase thermodynamic stability of the oleogels. Therefore, the addition of cyclopentasiloxane can improve the physical, thermal properties and stability of SMS–sesame oil oleogel, provide greater sensory profile and better product aesthetics. The developed oleogel can be a novel carrier for topical drug delivery.

A combined FTIR and DSC study on the bilayer-stabilising effect of electrostatic interactions in ion paired lipids

Investigating lipid ion pair formation is important for understanding the mechanisms of lipid-mediated drug resistance in bacteria. In this study we have used the charged amphiphiles dipalmitoylphosphatidylglycerol (DPPG) and dihexadecyldimethylammonium bromide (DHDAB), as a model to evaluate the formation of ion pairs by a combined Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analysis. FTIR was employed to study the environment of the DPPC headgroup phosphate and lipid/surfactant alkane chains, in vesicles formed by the two amphiphiles mixed in various molar ratios. An increase of the absorbance ratio of 1221-1201 cm-1 in the asymmetric phosphate stretching mode was found to follow a sigmoidal relationship with the proportion of DHDAB, increasing to a plateau above a DPPG/DHDAB 1:1 molar ratio of, providing evidence that the PG headgroup phosphate is involved in ion pairing. A consistent red shift was measured for the position of the symmetric CH2 stretch band for the lipid/surfactant 1:1 molar ratio mixture, which is indicative of an increased ordering of the hydrophobic chains. The DSC experiments yielded information about the thermotropic and the mixing behaviour of the lipid/surfactant systems. DPPG and DHDAB seem to form an ion pair with cluster compound characteristics at the equimolar ratio. Most interestingly, the DPPG/DHDAB 2:1 molar ratio mixture is characterized by strong intermolecular interactions, which result in a pronounced stabilization of the gel phase, possibly through the formation of a closely-associated ion triplet configuration in which the charges are delocalised across the headgroups.