Evaluation of the Thermal and Morphological Properties of γ-Irradiated Chitosan-Glycerol-Based Polymeric Films

Industry-sponsored research has intensified to find suitable substitutes for synthetic polymers. For this purpose, biopolymers are promising materials that are extracted from renewable resources. However, there are areas of concern (biopolymers are mostly brittle in the dry state) that require further research before they are used in advanced applications. To overcome this, plasticizers are often added to biopolymers to enhance their physicochemical properties. In this study, chitosan (CH)-glycerol (GL)-based polymeric films were prepared by a simple drop-casting technique, and the influence of a plasticizer (GL) on the properties of chitosan films was analyzed. Additionally, the as-prepared samples were irradiated with γ-rays (60Co γ rays with a dose of 102 kGy) to study the effect of γ-irradiation on the properties of polymeric composites. To achieve this, different samples were prepared by varying the amount of GL. FT-IR analysis revealed the interruption of hydrogen bonding in chitosan by the incorporation of GL. This led to the chain-spreading of CH, which ultimately increased the flexibility of the composite films (CH-GL). The DSC of the CH film showed two peaks: one endothermic peak below 100 °C (due to water vapor) and a second exothermic peak that appeared between 130 and 360 °C (degradation of the amino group). Plasticization of CH films with GL was confirmed by DSC, where the exothermic degradation was converted into an endothermic peak. Depending upon the amount of GL, γ-irradiation considerably affected the chemical structure of CH by breaking the carbohydrate and pyranose rings; this led to a decrease in the crystallinity of the composite films. The changes studied in the DSC and TGA analysis complemented each other. γ-irradiation also affected the morphology of the films, which changed from smooth and homogeneous to roasted structures, with random swelling on the surface of the films. This swelling reflected the degradation of the surfaces into thin layers. Considering the changes that occurred in the films post-γ-irradiation, it can be inferred that the irradiation dose of 102 kGy is sufficient to degrade as-prepared biopolymer composites.

The Physico-Chemical Properties of Glipizide: New Findings

The present work is a concrete example of how physico-chemical studies, if performed in depth, are crucial to understand the behavior of pharmaceutical solids and constitute a solid basis for the control of the reproducibility of the industrial batches. In particular, a deep study of the thermal behavior of glipizide, a hypoglycemic drug, was carried out with the aim of clarifying whether the recognition of its polymorphic forms can really be done on the basis of the endothermic peak that the literature studies attribute to the melting of the compound. A number of analytical techniques were used: thermal techniques (DSC, TGA), X-ray powder diffraction (XRPD), FT-IR spectroscopy and scanning electron microscopy (SEM). Great attention was paid to the experimental design and to the interpretation of the combined results obtained by all these techniques. We proved that the attribution of the endothermic peak shown by glipizide to its melting was actually wrong. The DSC peak is no doubt triggered by a decomposition process that involves gas evolution (cyclohexanamine and carbon dioxide) and formation of 5-methyl-N-[2-(4-sulphamoylphenyl) ethyl] pyrazine-2-carboxamide, which remains as decomposition residue. Thermal treatments properly designed and the combined use of DSC with FT-IR and XRPD led to identifying a new polymorphic form of 5-methyl-N-[2-(4-sulphamoylphenyl) ethyl] pyrazine-2-carboxamide, which is obtained by crystallization from the melt. Hence, our results put into evidence that the check of the polymorphic form of glipizide cannot be based on the temperature values of the DSC peak, since such a peak is due to a decomposition process whose Tonset value is strongly affected by the particle size. Kinetic studies of the decomposition process show the high stability of solid glipizide at room temperature.

Sulbactam pivoxil powder attributes and compatibility study with excipients

Background Sulbactam pivoxil is an irreversible β-lactamase inhibitor that can be used with β-lactam antibiotics to improve antibacterial therapy by the oral route. Relevant properties of this drug for pharmaceutical manufacturing are not available in the open literature. In this work, a solid-state characterization of sulbactam pivoxil at the molecular, particle, and bulk levels was performed. Results Particles exhibited a mean diameter of about 350 μm, irregular shape crystals, and good flow properties. This work presents for the first time the crystal structure of this β-lactamase inhibitor obtained by X-ray diffraction analysis. Fourier-transform infrared results showed the characteristic bands of aliphatic hydrocarbons and ester groups. The differential scanning calorimetry curve exhibited a sharp endothermic peak at 109 °C corresponding to sulbactam pivoxil melting. The thermogravimetric curve revealed a mass loss at 184 °C associated with a decomposition process. This powder showed a moisture content of 0.34% and a water activity of 0.463. Potential interactions between sulbactam pivoxil and common pharmaceutical excipients were evaluated by thermal analysis. The endothermic peak and the enthalpies of melting were preserved in almost all the analyzed mixtures. Conclusion The powder was constituted by micro-sized crystals of sulbactam pivoxil that had suitable physicochemical properties for processing in controlled humidity environments. Thermal analyses suggested that sulbactam pivoxil is compatible with most of the evaluated excipients. The information obtained in the present study is relevant for the development, manufacturing, and storage of formulations that include sulbactam pivoxil.

Heat treatment of liquid egg yolk

Starting from mechanical revolution, each day new methods and new equipment have emerged. Today, the Ultra Heat Treatment (UHT) is one of the important technologies that permits to the industry to reduce processing time while maintaining the same quality of the products. Egg and egg products are known as heat-sensitive products, so the UHT enables us to preserve their qualities after a heat treatment.Our aim is to study the effect of UHT treatment (approximately 67 °C for 190 s) on the Liquid Egg Yolk (LEY). For twenty-one days, the color and the apparent viscosity were measured every seven days, we also studied the damage of protein using DSC (Differential Scanning Calorimetry).Comparing the two graphs of DSC, the denaturation of protein is distinct. The endothermic peak decreased. This could be seen also on the rheological curves. The apparent viscosity is diminished from 231 mPa.s on the 1st day of storage to 224 mPa.s on 21st day. However, the treated LEY could be stored for longer period than the raw LEY.

Thermodynamic analysis of point mutations inhibiting high-temperature reversible oligomer of PDZ3

Differential scanning calorimetry (DSC) indicated that PDZ3 undergoes a peculiar thermal denaturation exhibiting two endothermic peaks due to the formation of reversible oligomers at high temperature (N↔I6↔D). This contrasts sharply with the standard 2-state denaturation model observed for small, globular proteins. We performed an alanine scanning analysis by individually mutating three hydrophobic residues at the crystallographic oligomeric interface (Phe340, Leu342, Ile389) and one away from the interface (Leu349, as a control). DSC analysis indicated that PDZ3-F340A and PDZ3-L342A exhibited a single endothermic peak. Furthermore, PDZ3-L342A underwent a perfect 2-state denaturation, as evidenced by the single endothermic peak, and confirmed by detailed DSC analysis, including global fitting of data measured at different protein concentrations. Reversible oligomerization (RO) at high temperatures by small globular proteins is a rare event. While we designed the mutations based on our previous study showing that a point mutation Val380 to a nonhydrophobic amino acid inhibited RO in DEN4 ED3, the results are nevertheless surprising since high-temperature RO involves proteins in a denatured state, as assessed by circular dichroism. Future studies will determine how and why mutations designed using crystal structures determined at ambient temperatures influence the formation of RO at high temperatures, and whether high-temperature ROs are related to the propensity of proteins to aggregate or precipitate at lower temperatures, which would provide a novel and unique way of controlling protein solubility and aggregation.SignificanceDespite being a small globular protein, which normaly undergo a two-state unfolding, the thermal denaturation of PSD95-PDZ3, monitored by DSC, exhibited two endothermic peaks. The second peak resulted from a reversible oligomerization (RO) at high temperatures, which is, on its own, a rare phenomenon. In this study, we show that the substitution of a single hydrophobic residue to an alanine at the interface of the crystallographic tetramers inhibited high-temperature RO, resulting in a single endothermic peak. Future studies are required to determine why mutations designed using crystal structures determined at ambient temperatures can inhibit high-temperature RO, and whether the ROs are precursor of irreversible aggregation, If so, the present observations will provide an entirely new basis for creating aggregation-resistant proteins.

EVALUATION OF CALLINECTES CHITOSAN AS A SUPERDISINTEGRANT IN METRONIDAZOLE TABLET

Objective: The objective of this study is to evaluate callinectes chitosan as a superdisintegrant in tablet formulation; superdisintegrants are incorporated into tablets at concentrations below 5% of tablet weight to effect prompt break-up of tablets after administration.Methods: Chitosan was extracted from shells of Callinectes gladiator. The polymer was characterized and then used as a disintegrant (in comparison with Ac-Di-Sol® and corn starch) at concentrations of 2, 4 and 8% for the formulation of metronidazole tablets. The micromeritic properties of granules; and mechanical and release properties of the tablets were studied.Results: A yield of 36.7% chitosan having degree of deacetylation of 62.7% was obtained from the crab shell. Fourier Transform Infrared absorption bands at 1495 and 3240 cm-1 typical of N-H bending and stretching respectively; and endothermic peak of 159 °C typical of melting of chitosan were obtained. No adverse interaction between the chitosan and metronidazole was observed. The disintegration times of tablets containing 2, 4 and 8% chitosan were 12.2, 10.4 and 9.3 min respectively.Conclusion: Callinectes chitosan is suitable for use as a superdisintegrant in tablets. It appears to be superior to corn starch as disintegrant although less effective compared to Ac-Di-Sol®. However, the relative cheapness and ready availability of chitosan would make it to be preferred to Ac-Di-Sol®.

Effects of Sn Addition on Clustering and Age-Hardening Behavior in a Pre-Aged Al-Mg-Si Alloy

The effects of Sn addition on clustering and age-hardening behavior in an Al-0.6Mg-1.0Si (mass %) alloy were investigated. Addition of Sn delayed the age-hardening in single aging at 170 ̊C. On the other hand, Sn promoted the age-hardening response in 3-step aging process which comprises a pre-aging (PA) at 90 ̊C for 18ks followed by natural aging (NA) for 604.8ks and artificial aging (AA) at 170 ̊C. The characteristics of clusters formed during PA and NA were evaluated by differential scanning calorimetry (DSC) analysis and atom probe tomography (APT). The DSC results show that the endothermic peak at around 160 ̊C to 200 ̊C was observed in the Sn-free alloy. On the other hand, in the Sn-added alloy, endothermic peak was not observed. It is suggested that Sn addition suppresses the formation of the clusters formed during NA. The APT results show that the Sn addition decreases the number density of clusters, especially smaller clusters. No Sn precipitates were found in Mg-Si precipitates formed during AA at 170 ̊C for 3.6ks. It is speculated that suppression of smaller cluster formation by addition of Sn promotes the age-hardening response

Thermal properties of flax fiber scoured by different methods

Thermal properties of flax roves untreated and treated were characterized by differential scanning calorimetry (DSC) and thermal gravity analyzer (TGA) in order to understand their thermal behavior in more detail and to evaluate the effect of scouring processing on the thermal behavior. Flax roves were treated with six kinds of methods including biological scouring, one bath, two bath, bleaching, alkali scouring and industry chemical scouring as standards. Results showed that all treatments improved thermal stability of flax roves. The results indicated that glass transition temperature (Tg) decreased after scouring besides the sample by directly bleaching. It is more difficult to determine the endothermic peak of flax treated by chemical scouring in industry because it takes a very flat course. A distinct endothermic peak was observed for the untreated flax rove, while a distinct exothermic peak in different temperature interval was revealed for other four treated flax rove samples. For TGA analysis, thermal degradation of flax roves studied consists of three regions of the initial, main, and char decomposition, and the third stage consists of secondary weight loss and carbonization for flax roves with biological scouring, one-bath and two-bath. Besides, different residue left indicates that the bio-scoured flax roves are lost with volatile products and does not contribute to char formation. These results provide valuable preferences for mechanism and top value added application of bio-scouring in flax roves.

Thermal Analytical Characteristics by TGA-DTA-DSC Analysis of Carica papaya Leaves from Kachchh

An experimental study on Carica papaya leaves was carried out in Thermo gravimetric analyzer (TGA), Differential Thermal Analyzer (DTA) and Differential Scanning Calorimetric (DSC) analyzer to investigate the effects of reaction atmosphere on thermal chemical characteristics. Experimental results show that In DSC curve, Endothermic peak at 101 °C is attributed to dehydration/Water loss from surface and pores of the powder sample. Step at 215 °C is associated with second order phase transition such as Glass Transition and it should be further confirmed in second heating (During heat- cool- heat cycle). Endothermic peak at 336 °C is associated protease thermal decomposition /Beta Cyclodextrin breakdown. In the TGA Curve, The initial 4 % weight loss is due to water loss from surface/pores of powder sample. Second weight loss between 200-450 °C is associated to degradation of cellulose and hemicellulose.

Changes of Endothermic Peak of Expanded Graphite Based Chemical Heat Storage Materials CaxZny(OH)2(x+y)

Expanded graphite is used as framework material in inorganic or organic heat storage materials commonly, of which the function is to improve thermal performance of the relevant materials. However, its negative effect is unclear. In this paper, the change of endothermic temperature of chemical heat storage material CaxZny(OH)2(x+y) by graphite addition is reported. Differential scanning calorimetry (DSC) is employed to perform the measurement. The result shows that the initial temperature and width of the endothermic peak decrease due to the action of the added graphite slightly; Along with the increase of graphite content, the endothermic peak moves to lower temperature further, the width and height of the peak reduce simultaneously.