Current Physical Chemistry - Volume 14, Issue 1, 2024

Polymorphism permits solids to have two or multiple crystal structures with varying orientations or conformations, and polymorph drug dissolution and solubility vary. Polymorphism influences drug efficacy, bioavailability and toxicity. Various parameters can regulate polymorph crystallization, including supersaturation phase, temperature, stirring rate, solvent addition rate, seed crystal, additives and pH. To characterize and monitor polymorphs, various analytical approaches are available, including powder X-Ray diffraction / X-Ray diffraction (PXRD/XRD), also called as Gold Standard method, differential scanning calorimetry (DSC), Infrared spectroscopy (IR), and microscopical studies. To prevent polymorphic change during production, distribution, and storage, formulation with the most stable form in the marketed product is considered. In addition, by monitoring each phase of raw material processing, polymorphisms can be controlled during dosage form manufacturing. The objective of this review is to provide concise information on drug polymorphism, their characterization process, their effect on the stability of dosage forms, factors controlling polymorphism in the crystallization process, some case studies on polymorphs, control of polymorphism during the formulation of successful dosage forms and some of the regulatory considerations regarding polymorphs. Various databases like Pubmed/Medline, Google Scholar and Web of Science of all English language articles were searched, and relevant information was collected regarding the importance of polymorphism in formulation development. From a vast literature survey, it was found that polymorphism is a very important tool in a pre-formulation study that provides information about the fate of a drug molecule in its journey. From the present study, it was concluded that the polymorphism property of a drug should be taken into consideration at the pre-formulation stage since it is a very important tool for the formulation of a successful dosage form with stability and efficacy.

Background: The aim of this research is to study the effect of length-to-width ratio on mesomorphism to enhance the understanding of its potential applications. This will be achieved by synthesizing a unique and innovative series of identical ester molecules, including lateral methoxy groups and terminal ethyl benzoate groups. In this research, we aim to find new insights into the relationship between molecular structures and mesomorphic behaviors, which could have significant implications for the development of advanced materials with adapted properties. The objective of the study is to investigate the mesophase behavior of new ester mesogens and determine how they are influenced by lateral methoxy groups. By identifying the underlying perspectives and relationships between these variables, we hope to better understand the unique properties and potential applications of these materials. Method: In this research work, the focus is on the synthesis of ethyl(E)-4-((3-(4-alkoxy-3- methoxyphenyl)acryloyl)oxy)benzoate, which is prepared from Steglich esterification method by using (E)-3-(4-alkoxy-3-methoxyphenyl)acrylic acid and ethyl 4- hydroxybenzoate. Synthesis processes involve precise reaction sequences designed to ensure maximum yield and purity of the final product. By providing a detailed report on the experimental process, this study contributes to the ongoing research efforts aimed at the development of innovative compounds with various applications in liquid crystals. Result: A new set of liquid crystal derivatives has been synthesized and studied to investigate the effect of molecular structure on the behavior of liquid crystals, with particular attention to the group -OCH3 located laterally. This series was composed of 12 derivatives (C1-C16). Among them, the first six derivatives (C1-C6) did not have the characteristics of a liquid crystal, while the remaining derivatives (C7 and C8) had a monotropic behavior, and C10-C16 had an enantiotropic smectogenic liquid crystal behavior without exhibition of the nematic phase. The average thermal stability of the smectic property was 87.33 °C, and the mesophase range was 2 °C to 14 °C. The molecular structure was confirmed by analytical and spectral analysis. The properties of liquid crystals of this new series were compared with those of other known structurally similar homologous series. The transition temperatures were determined with an optical polarizing microscope equipped with a heating phase. Conclusion: The mesomorphic thermal and optical properties of the compounds have been validated by DSC and POM techniques. The result shows that the length of the alkyl chain has a significant influence on the mesomorphic characteristics and thermal stability of the different mesophases. Evaluation of the compounds studied indicates that the molecules are sensitive to their lateral substituent, which influences the thermal characteristics and stability of the mesophase.

Background: The physicochemical properties, including the thermodynamics of micellization studies, received much attention. Cationic surfactant cetrimonium bromide (C16TABr) in electrolytes (sodium chloride and sodium salicylate) and nonelectrolyte (Ethylene glycol) in an aqueous solution were examined, and interesting results were obtained. The present investigation aims to identify a suitable combination of cationic surfactant cetrimonium bromide + electrolytes and nonelectrolytes having the ability to alter the size or shape of the micellar system using available methods. Methods: Surface tension, conductivity, viscosity, ultrasonic velocity, and dynamic light scattering (DLS) methods at different temperatures (303-323K) were used during the experimental research work. Results: The experimental results pointed out that the incorporation of electrolytes and nonelectrolyte into the cationic surfactant affects the physicochemical properties such as critical micelle concentration (CMC), surface tension (ST), degree of ionization (α), degree of counterion binding (β), standard Gibbs free energy of micellization (ΔG^om), standard entropy of micellization (ΔSom), standard heat of micellization (ΔHo m), viscosities, and acoustic parameters. Dynamic light scattering (DLS) measurements reveal exciting facts related to the size and shape transformation of the mixed micellar assembly. Structure modification can be obtained by choosing right the combination of cationic surfactant cetrimonium bromide + electrolytes (sodium chloride and sodium salicylate) and nonelectrolyte (Ethylene glycol) ratio. Conclusion: It concluded that, over a threshold level, an electrolyte such as NaCl concentration causes the micelle size to rise. The entropy of micellization goes down when a structure-breaker (EG) is added to the water phase, and this is because the structure of the water is changed near hydrophobic groups. The physicochemical features of cetrimonium bromide (C16TABr) show unique behaviour under the influence of micelle-driven and micelle- forbidden systems.

Aim: Potassium dihydrogen phosphate (KDP) is an excellent nonlinear optical material that has many potential applications, such as laser frequency conversion, Qswitches, Pockels cells, 3-D optical data storage devices, etc. Doping enhances various optical parameters of KDP. Doping changes in the absorbance and dopants such as aspartic acid, succinic acid, glycine, and L-alanine improved the optical band gap of the sample. Background: KDP is a non-linear optic material that has many important applications. Many researchers all over the world are trying to improve its optical properties. Objective: To synthesise pure KDP and KDP doped with aspartic acid, succinic acid, glycine, and L-alanine. Also, to study the temperature stability of the grown samples using TGA, DTA, and DSC analysis. Methods: Growth from solution at low temperatures is used for the growth of crystals. TGA, DTA, and DSC are used to analyse the stability of the samples against temperature variations. Results: KDP crystals of good quality were grown using the slow cooling solution growth technique. Determined their band gap using the Tauc Plot. Significant variations in the optical bandgap are noticed. Also, the TGA, DTA, and DSC characterizations were done. Conclusion: KDP solution and grown crystals of good quality were synthesized. The variation in the bandgap on doping is a significant result as the modifications in bandgap enable the sample to be used in a more enhanced applications. Also, the doped samples were stable for variations in temperature, like the pure KDP.

Background: The present work describes the synthesis, characterization, and thermo-acoustical parameters of binary solutions of 1-(2-(4-fluorophenyl)-5-(pyridin-4-yl)- 1,3,4-oxadiazol-3(2H)-yl)-3-(pyridin-2-yl)prop-2-en-1-one, (AS1-08) and 1-(2-(4- methoxyphenyl)-5-(pyridin-4-yl)-1,3,4-oxadiazol-3(2H)-yl)-3-(pyridin-2-yl)prop-2-en-1- one, (AS1-12) in dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) were estimated. Methods: Viscosity, ultrasonic velocity, and density methods at different solvents (DMSO and DMF) and different temperatures (298.15, 308.15, and 318.15 K) were used during the experimental research work. Results: Some acoustic parameters such as adiabatic compressibility (Κs), intermolecular free path length (Lf), Rao’s molar sound function (Rm), Van der Waals constant (b), internal pressure (π), free volume (Vf) and solvation number (Sn) were calculated. The results obtained were interpreted in terms of solute-solvent and solute-solute interactions. Conclusion: The thermodynamic and various acoustical properties were determined at three different temperatures viz. (298.15, 308.15, and 318.15 K) at atmospheric pressure. Likewise, the similarity between experimental results of the binary solutions was studied to analyze how the change in the structural modification and solvent changes the values of Gibbs energy of activation (ΔG*), enthalpy of activation (ΔH*), and entropy of activation (ΔS*).

Introduction: Remdesivir for injection is a Gilead Sciences manufactured drug product approved by the FDA to treat COVID-19. One of the critical attributes of this drug product, which is lyophilized, is its water moisture content. The current method used to determine the water content of remdesivir is the Karl Fischer titration method. The Karl Fischer method is considered the gold standard for determining the residual water moisture content of lyophilized drug products in the pharmaceutical industry. However, it is timeconsuming, can at times be sensitive to difficult-to-control techniques, and most importantly is destructive. The purpose of this study was to create a non-destructive residual water moisture determination method using FT-NIR. Methods: Three FT-NIR methods were proposed as a non-destructive alternative to Karl Fischer method: partial least squares regression, Beer’s law and area under the curve, and Beer’s law and peak height. Results were statistically validated using RMSEC, RMSEP, and R², and the percent differences of predicted and accepted residual moisture values were compared with external validation vials. Results: Results showed that the partial least squares regression method produced a 0.999 correlation coefficient and a 95% performance index score, highlighting the accuracy between the actual Karl Fischer moisture values and the predicted FT-NIR moisture values. The Beer’s law methods produced acceptable correlation coefficients of 0.996 and 0.982 for the peak area and height, respectively, but comparisons between the actual and predicted values were not as closely matched as the partial least squares method. Conclusion: Our results support the use of a non-destructive partial least squares FT-NIRbased moisture contest method, which is a useful alternative to the destructive Karl Fischer method for determining residual water moisture of lyophilized drug products. Only an FTNIR instrument and chemometric statistical software along with the appropriately trained/educated analysts, and routine Karl Fischer instrumentation to measure/determine moisture content values of either water spiked or lyo-thieved and normal lyophilized samples are required.