Dielectric properties of binary solvent mixtures of dimethyl sulfoxide with water

Microwave Sensor for the Determination of DMSO Concentration in Water-DMSO Binary Mixture

This research aims to develop a microwave sensor to accurately measure the concentration of dimethyl sulfoxide (DMSO) in water-DMSO binary mixtures. The proposed sensor will utilize microwave frequency measurements to determine the DMSO concentration, providing a non-invasive and efficient method for analyzing DMSO solutions. The research will involve the design, fabrication, and testing of the sensor, as well as the development of an appropriate calibration model. The outcomes of this study will contribute to improved monitoring and quality control in various fields, including pharmaceuticals, chemical synthesis, and biomedical research. The binary mixtures of dimethyl sulfoxide (DMSO) and water with varying concentrations were investigated in the frequency range of 1 GHz to 5 GHz at room temperature using a microwave sensor. The proposed microwave sensor design was based on an interdigital capacitor (IDC) microstrip antenna loaded with a hexagonal complementary ring resonator (HCRR). The performance of the sensor, fabricated using the print circuit board (PCB) technique, was validated through simulations and experiments. The reflection coefficient (S₁₁) and resonance frequency (F_r) of binary mixtures of DMSO and water solutions were recorded and analyzed for DMSO concentrations ranging from 0% v/v to 75% v/v. Mathematical models were developed to analyze the data, and laboratory tests showed that the sensor can detect levels of DMSO/water binary mixtures. The sensor is capable of detecting DMSO concentrations ranging from 0% v/v to 75% v/v, with a maximum sensitivity of 0.138 dB/% for S₁₁ and ΔS₁₁ and 0.2 MHz/% for F_r and ΔF_r at a concentration of 50% v/v. The developed microwave sensor can serve as an alternative for detecting DMSO concentrations in water using a simple and cost-effective technique. This method can effectively analyze a wide range of concentrations, including highly concentrated solutions, quickly and easily.

Lincomycin HCl-Loaded Borneol-Based In Situ Gel for Periodontitis Treatment

Solvent exchange-induced in situ forming gel (ISG) has emerged as a versatile drug delivery system, particularly for periodontal pocket applications. In this study, we developed lincomycin HCl-loaded ISGs using a 40% borneol-based matrix and N-methyl pyrrolidone (NMP) as a solvent. The physicochemical properties and antimicrobial activities of the ISGs were evaluated. The prepared ISGs exhibited low viscosity and reduced surface tension, allowing for easy injection and spreadability. Gel formation increased the contact angle on agarose gel, while higher lincomycin HCl content decreased water tolerance and facilitated phase separation. The drug-loading influenced solvent exchange and matrix formation, resulting in thinner and inhomogeneous borneol matrices with slower gel formation and lower gel hardness. The lincomycin HCl-loaded borneol-based ISGs demonstrated sustained drug release above the minimum inhibitory concentration (MIC) for 8 days, following Fickian diffusion and fitting well with Higuchi's equation. These formulations exhibited dose-dependent inhibition of Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 8739, and Prophyromonas gingivalis ATCC 33277, and the release of NMP effectively inhibited Candida albicans ATCC 10231. Overall, the 7.5% lincomycin HCl-loaded 40% borneol-based ISGs hold promise as localized drug delivery systems for periodontitis treatment.

Clotrimazole-Loaded Borneol-Based In Situ Forming Gel as Oral Sprays for Oropharyngeal Candidiasis Therapy

Oral candidiasis encompasses fungal infections of the tongue and other oral mucosal sites with fungal overgrowth and its invasion of superficial oral tissues. Borneol was assessed in this research as the matrix-forming agent of clotrimazole-loaded in situ forming gel (ISG) comprising clove oil as the co-active agent and N-methyl pyrrolidone (NMP) as a solvent. Their physicochemical properties, including pH, density, viscosity, surface tension, contact angle, water tolerance, gel formation, and drug release/permeation, were determined. Their antimicrobial activities were tested using agar cup diffusion. The pH values of clotrimazole-loaded borneol-based ISGs were in the range of 5.59-6.61, which are close to the pH of 6.8 of saliva. Increasing the borneol content in the formulation slightly decreased the density, surface tension, water tolerance, and spray angle but increased the viscosity and gel formation. The borneol matrix formation from NMP removal promoted a significantly (p < 0.05) higher contact angle of the borneol-loaded ISGs on agarose gel and porcine buccal mucosa than those of all borneol-free solutions. Clotrimazole-loaded ISG containing 40% borneol demonstrated appropriate physicochemical properties and rapid gel formation at microscopic and macroscopic levels. In addition, it prolonged drug release with a maximum flux of 370 µg·cm^-2 at 2 days. The borneol matrix generated from this ISG obsentively controlled the drug penetration through the porcine buccal membrane. Most clotrimazole amounts still remained in formulation at the donor part and then the buccal membrane and receiving medium, repectively. Therefore, the borneol matrix extended the drug release and penetration through the buccal membrane efficiently. Some accumulated clotrimazole in tissue should exhibit its potential antifugal activity against microbes invading the host tissue. The other predominant drug release into the saliva of the oral cavity should influence the pathogen of oropharyngeal candidiasis. Clotrimazole-loaded ISG demonstrated efficacious inhibition of growth against S. aureus, E. coli, C. albicans, C. krusei, C. Lusitaniae, and C. tropicalis. Consequently, the clotrimazole-loaded ISG exhibited great potential as a drug delivery system for oropharyngeal candidiasis treatment by localized spraying.

Physicochemical and Bioactivity Characteristics of Doxycycline Hyclate-Loaded Solvent Removal-Induced Ibuprofen-Based In Situ Forming Gel

Modulation with the suppression of infection and inflammation is essential to the successful treatment of periodontitis. An aqueous insoluble hydrophobic anti-inflammatory compound, i.e., ibuprofen (IBU), was investigated in this study as the matrix-forming agent of a doxycycline hyclate (DH)-loaded solvent removal-induced in situ forming gel (ISG) using dimethyl sulfoxide (DMSO) and N-methyl pyrrolidone (NMP) as the solvents. Their physicochemical properties, including pH, density, viscosity, surface tension, contact angle, water tolerance, injectability, mechanical properties, gel formation, and drug release, were determined. Their antimicrobial activities were tested using agar cup diffusion, and their anti-inflammatory activity was assessed using thermal inhibition of protein denaturation of egg albumin. Increasing the IBU content decreased the density, pH, surface tension, and contact angle but increased the viscosity, force and work of injection, and gel formation of IBU-based ISG solution. Although their water tolerance values decreased with the increase in IBU content, the addition of DH and the use of NMP led to high water tolerance. The characterization of the dried gel remnants of ISGs presented no change in IBU crystallinity and thermal properties and confirmed no chemical interaction among the components of ISGs. The obtained transformed IBU matrix prolonged the release of DH and IBU from ISGs over 7 days from its tortuously packed IBU matrix with small pores, and conformed well with Fickian diffusion mechanism. The developed DH-loaded solvent removal-induced IBU-based ISGs exhibited efficient antimicrobial activities against Staphylococcus aureus, methicillin-resistant S. aureus, Escherichia coli, Candida albicans, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. IBU in formulation promoted the antimicrobial activity of ISGs, whereas DH and NMP promoted the anti-inflammatory activity of ISGs. Consequently, the DH-loaded solvent removal-induced IBU-based ISGs proposed in this study show great potential as an effective bioactive drug delivery system for periodontitis treatment by localized periodontal pocket injection.

Cosolvent effects on the structure and thermoresponse of a polymer brush: PNIPAM in DMSO–water mixtures

Structural characterisation of thermoresponsive polymer brushes in binary DMSO–water mixtures reveals both LCST and UCST behaviour.

Ramírez M, Zezza P, Lucío MI, Bañuls MJ, Maquieira Á, Morales-Vidal M, Beléndez A, Pascual I. Processing of Holographic Hydrogels in Liquid Media: A Study by High-Performance Liquid Chromatography and Diffraction Efficiency

The storage of time-stable holographic gratings in hydrogel matrices when the material is immersed in aqueous media is a real challenge at present. The optimization of the storage stages of the holograms must be properly investigated to identify the most suitable development processes. For this reason, this work is focused on the study of the optimization of the washing stages of the hydrogels based on acrylamide and N,N’-methylenebis(acrylamide) once unslanted transmission holograms have been stored. High-performance liquid chromatography and UV-visible measurements have been employed in our system to analyze the composition of the washing solutions. PBST and DMSO:H₂O are used as solvents in the washing stages. The diffraction efficiencies are measured during the washing stages and after the storing of the holograms during several days in PBST. Maximum diffraction efficiencies of 38 and 27.6% are reached when PBST and DMSO:H₂O are employed, respectively, for the washing process. Holograms show temporal stability after being stored immersed in PBST at 4 °C for 4 days.

Redefining the Molecular Interplay between Dimethyl Sulfoxide, Lipid Bilayers, and Dehydration

The potentially damaging action of dimethyl sulfoxide (DMSO) on phospholipid bilayers remains a matter of controversy. We have conducted a series of long-scale molecular dynamics simulations of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers at various levels of hydration in the presence of variable quantities of DMSO. These simulations provide evidence for a non-destructive dehydrating mechanism of action for DMSO on DOPC bilayers across a wide concentration range and levels of hydration. Specifically, under full- and low-hydration conditions, the bilayer underwent a minor lateral contraction, coinciding with surface dehydration in the presence of dilute DMSO solutions (X_DMSO < 0.3). At higher DMSO concentrations, this bilayer structure was retained despite a progressive deterioration of the hydration structure at the interface. A similar convergence of bilayer structural properties was observed under dehydration conditions for 0.3 < X_DMSO < 0.7. Destabilization occurred for dehydrated bilayers in the presence of X_DMSO ≥ 0.7, suggesting the existence of a DMSO concentration and/or dehydration threshold. However, such DMSO concentrations far exceed those established as toxic to other cellular components. Our findings represent a computational model for DMSO-DOPC interactions that is consistent with a range of experimental characterizations, offering new molecular insights into the cryoprotective mechanisms of action of DMSO.

Surfactant-like Peptide Self-Assembled into Hybrid Nanostructures for Electronic Nose Applications

An electronic nose (e-nose) utilizes a multisensor array, which relies on the vector contrast of combinatorial responses, to effectively discriminate between volatile organic compounds (VOCs). In recent years, hierarchical structures made of nonbiological materials have been used to achieve the required sensor diversity. With the advent of self-assembling peptides, the ability to tune nanostructuration, surprisingly, has not been exploited for sensor array diversification. In this work, a designer surfactant-like peptide sequence, CG₇-NH₂, is used to fabricate morphologically and physicochemically heterogeneous "biohybrid" surfaces on Au-covered chips. These multistructural sensing surfaces, containing immobilized hierarchical nanostructures surrounded by self-assembled monolayers, are used for the detection and discrimination of VOCs. Through a simple and judicious design process, involving changes in pH and water content of peptide solutions, a five-element biohybrid sensor array coupled with a gas-phase surface plasmon resonance imaging system is shown to achieve sufficient discriminatory capabilities for four VOCs. Moreover, the limit of detection of the multiarray system is bench-marked at <1 and 6 ppbv for hexanoic acid and phenol (esophago-gastric biomarkers), respectively. Finally, the humidity effects are characterized, identifying the dissociation rate constant as a robust descriptor for classification, further exemplifying their efficacy as biomaterials in the field of artificial olfaction.

Dielectric Characteristics, Electrical Conductivity and Solvation of Ions in Electrolyte Solutions

Solvation and association of ions in solutions largely depend on the dielectric properties of the solvent, the distance between ions in solutions, and temperature. This paper considers the effect of temperature on static dielectric constant (DC), dipole dielectric relaxation (DR) time, and limiting (ultimate) high frequency (HF) electrical conductivity (EC) of water and some polar solvents. In the investigated temperature range (0–370 °C), the static DC and DR time of water decrease, and limiting HF EC passes through a maximum at 250–300 °C with temperature growth. The dielectric characteristics of methanol, ethanol, and propanol behave in a similar way. It is shown that the existence of an HF EC temperature maximum is due to the different nature of the temperature dependences of DC and DR time. It is suggested that the same dependences are responsible for the presence of a maximum in the temperature dependences of the dissociation degree and the ionic product of water. The influence of non-electrolytes concentration as well as metal salts on the dielectric properties of their aqueous solutions is considered. The limiting HF EC of water determines the specific EC value of aqueous electrolyte solutions. Analysis of the absorption of microwave energy by polar solvents, as well as aqueous solutions of non-electrolytes and electrolytes, at a frequency of 2455 MHz is carried out. The optimal conditions for high-frequency heating of solutions have been established. The distance between ions in aqueous solutions of inorganic salts and in non-aqueous solutions of ionic liquids is calculated. It is shown that the maximum on the concentration dependence of the specific EC can be related to ions association.

Revealing and Attenuating the Electrostatic Properties of Tubulin and Its Polymers

Tubulin is an electrostatically negative protein that forms cylindrical polymers termed microtubules, which are crucial for a variety of intracellular roles. Exploiting the electrostatic behavior of tubulin and microtubules within functional microfluidic and optoelectronic devices is limited due to the lack of understanding of tubulin behavior as a function of solvent composition. This work displays the tunability of tubulin surface charge using dimethyl sulfoxide (DMSO) for the first time. Increasing the DMSO volume fractions leads to the lowering of tubulin's negative surface charge, eventually causing it to become positive in solutions >80% DMSO. As determined by electrophoretic mobility measurements, this change in surface charge is directionally reversible, i.e., permitting control between -1.5 and + 0.2 cm²  (V s)^-1 . When usually negative microtubules are exposed to these conditions, the positively charged tubulin forms tubulin sheets and aggregates, as revealed by an electrophoretic transport assay. Fluorescence-based experiments also indicate that tubulin sheets and aggregates colocalize with negatively charged g-C₃ N₄ sheets while microtubules do not, further verifying the presence of a positive surface charge. This study illustrates that tubulin and its polymers, in addition to being mechanically robust, are also electrically tunable.

Microstructural free volume and dynamics of cryoprotective DMSO–water mixtures at low DMSO concentration

This work investigates the free-volume properties of the dimethyl sulfoxide (DMSO)–water mixtures by positron annihilation lifetime spectroscopy over a wide temperature range of 20–320 K. The processes of melting and solidification of the water, DMSO and the DMSO–water mixtures at 1.8, 2.0 and 10% vol. DMSO respectively were studied. It was found that the recrystallization during heating of the water–DMSO cryoprotective mixtures above 160 K at low DMSO concentrations is affected by the amount of DMSO in the mixture. The amount of amorphous phase formed during cooling influences the hysteresis between cooling and heating cycles which could be crucial for cell survival. Experiments also show the time dependence of crystallization which indicates that rapid heating can suppress this secondary crystallization which is undesirable during the cell thawing process. Similar concentrations of DMSO (1.8% and 2% vol. DMSO in water) where a 2% vol. DMSO mixture secures cell survival but 1.8 vol% does not, showed differences in structural and dynamic properties that are key factors in cell survival. These results were supported by differential scanning calorimetry and low frequency dielectric spectroscopy measurements. The obtained data are in strong agreement with the observed cryoprotective efficacy of the DMSO–water mixtures on living cells.

Positron annihilation lifetime spectroscopy reveals changes in the DMSO–water microstructure in low concentrations of DMSO (1.8%, 2.0% and 10% v/v) that have a great impact on the cryoprotective effect during the cryopreservation of cells.

Photoisomers of Azobenzene Star with a Flat Core: Theoretical Insights into Multiple States from DFT and MD Perspective

This study focuses on comparing physical properties of photoisomers of an azobenzene star with benzene-1,3,5-tricarboxamide core. Three azobenzene arms of the molecule undergo a reversible trans-cis isomerization upon UV-vis light illumination giving rise to multiple states from the planar all-trans one, via two mixed states to the kinked all-cis isomer. Employing density functional theory, we characterize the structural and photophysical properties of each state indicating a role the planar core plays in the coupling between azobenzene chromophores. To characterize the light-triggered switching of solvophilicity/solvophobicity of the star, the difference in solvation free energy is calculated for the transfer of an azobenzene star from its gas phase to implicit or explicit solvents. For the latter case, classical all-atom molecular dynamics simulations of aqueous solutions of azobenzene star are performed employing the polymer consistent force field to shed light on the thermodynamics of explicit hydration as a function of the isomerization state and on the structuring of water around the star. From the analysis of two contributions to the free energy of hydration, the nonpolar van der Waals and the electrostatic terms, it is concluded that isomerization specificity largely determines the polarity of the molecule and the solute-solvent electrostatic interactions. This convertible hydrophilicity/hydrophobicity together with readjustable occupied volume and the surface area accessible to water, affects the self-assembly/disassembly of the azobenzene star with a flat core triggered by light.

Sub-50 nm Channel Vertical Field-Effect Transistors using Conventional Ink-Jet Printing

A printed vertical field-effect transistor is demonstrated, which decouples critical device dimensions from printing resolution. A printed mesoporous semiconductor layer, sandwiched between vertically stacked drive electrodes, provides <50 nm channel lengths. A polymer-electrolyte-based gate insulator infiltrates the percolating pores of the mesoporous channel to accumulate charge carriers at every semiconductor domain, thereby, resulting in an unprecedented current density of MA cm^-2 .

Ion specificities of artificial macromolecules

Artificial macromolecules are well-defined synthetic polymers, with a relatively simple structure as compared to naturally occurring macromolecules. This review focuses on the ion specificities of artifical macromolecules. Ion specificities are influenced by solvent-mediated indirect ion-macromolecule interactions and also by direct ion-macromolecule interactions. In aqueous solutions, the role of water-mediated indirect ion-macromolecule interactions will be discussed. The addition of organic solvents to aqueous solutions significantly changes the ion specificities due to the formation of water-organic solvent complexes. For direct ion-macromolecule interactions, we will discuss specific ion-pairing interactions for charged macromolecules and specific ion-neutral site interactions for uncharged macromolecules. When the medium conditions change from dilute solutions to crowded environments, the ion specificities can be modified by either the volume exclusion effect, the variation of dielectric constant, or the interactions between ions, macromolecules, and crowding agents.

Relation of molecular structure to Franck-Condon bands in the visible-light absorption spectra of symmetric cationic cyanine dyes

A Franck-Condon (FC) model is used to study the solution-phase absorbance spectra of a series of seven symmetric cyanine dyes having between 22 and 77 atoms. Electronic transition energies were obtained from routine visible-light absorbance and fluorescence emission spectra. Harmonic normal modes were computed using density functional theory (DFT) and a polarizable continuum solvent model (PCM), with frequencies corrected using measured mid-infrared spectra. The model predicts the relative energies of the two major vibronic bands to within 5% and 11%, respectively, and also reproduces structure-specific differences in vibronic band shapes. The bands themselves result from excitation of two distinct subsets of normal modes, one with frequencies between 150 and 625cm(-1), and the other between 850 and 1480cm(-1). Vibronic transitions excite symmetric in-plane bending of the polymethine chain, in-plane bends of the polymethine and aromatic C-H bonds, torsions and deformations of N-alkyl substituents, and in the case of the indocyanines, in-plane deformations of the indole rings. For two dyes, the model predicts vibronic coupling into symmetry-breaking torsions associated with trans-cis photoisomerization.

Physicochemical and biological properties of oxovanadium(IV), cobalt(II) and nickel(II) complexes with oxydiacetate anions

The potentiometric and conductometric titration methods have been used to characterize the stability of series of VO(IV)-, Co(II)- and Ni(II)-oxydiacetato complexes in DMSO-water solutions containing 0-50 % (v/v) DMSO. The influence of DMSO as a co-solvent on the stability of the complexes as well as the oxydiacetic acid was evaluated. Furthermore, the reactivity of the complexes towards superoxide free radicals was assessed by employing the nitro blue tetrazolium (NBT) assay. The biological properties of the complexes were investigated in relation to their cytoprotective activity against the oxidative damage generated exogenously by using hydrogen peroxide in the Human Dermal Fibroblasts adult (HDFa) cell line as well as to their antimicrobial activity against the bacteria (Bacillus subtilis, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis). The relationship between physicochemical and biological properties of the complexes was discussed.

Electrochemical and computational analysis of solvent effects on the kinetics of reaction of nitrite ion with o-quinone

The effect of solvent on the rate constant of the reaction of nitrite ion with o-quinone has been investigated by means of voltammetry and voltammogram digital simulation methods. The experimental results have been compared with theoretical calculations; the latter results are in good agreement with experimental data and confirm that the dielectric constant of the solvent is the most influential factor on the rate of reaction.

Tunable negative differential electrolyte resistance in a conical nanopore in glass

Liquid-phase negative differential resistance (NDR) is observed in the i-V behavior of a conical nanopore (~300 nm orifice radius) in a glass membrane that separates an external low-conductivity 5 mM KCl solution of dimethylsulfoxide (DMSO)/water (v/v 3:1) from an internal high-conductivity 5 mM KCl aqueous solution. NDR appears in the i-V curve of the negatively charged nanopore as the voltage-dependent electro-osmotic force opposes an externally applied pressure force, continuously moving the location of the interfacial zone between the two miscible solutions to a position just inside the nanopore orifice. An ~80% decrease in the ionic current occurs over less that a ~10 mV increase in applied voltage. The NDR turn-on voltage was found to be tunable over a ~1 V window by adjusting the applied external pressure from 0 to 50 mmHg. Finite-element simulations based on solution of Navier-Stokes, Poisson, and convective Nernst-Planck equations for mixed solvent electrolytes within a negatively charged nanopore yield predictions of the NDR behavior that are in qualitative agreement with the experimental observations. Applications in chemical sensing of a tunable, solution-based electrical switch based on the NDR effect are discussed.

1H NMR spectroscopic investigations on the conformation of amphiphilic aromatic amino acid derivatives in solution: effect of chemical architecture of amphiphiles and polarity of solvent medium

In this study, the conformation of the amphiphilic lauryl esters of L-tyrosine (LET) and L-phenylalanine (LEP) in water and dimethyl sulfoxide is established. The alkyl chain protons of LEP in D(2)O appear at δ 1.010-1.398 and show an upfield shift and large line width, suggesting the proximity of the phenyl ring to the alkyl chain in contrast to that of LET. Quite interestingly, in DMSO-d(6), the (1)H NMR spectra of LET and LEP show a strong similarity that is suggestive of an orientation that positions the aromatic ring and aliphatic chain away from each other. These results are substantiated with two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOSEY). Theoretical molecular models of the conformation at the interface corroborate the experimental findings. Investigations of the solvent polarity and chemical structure-dependent conformation are discussed.

On the role of the SP1 domain in HIV-1 particle assembly: a molecular switch?

Expression of a retroviral protein, Gag, in mammalian cells is sufficient for assembly of immature virus-like particles (VLPs). VLP assembly is mediated largely by interactions between the capsid (CA) domains of Gag molecules but is facilitated by binding of the nucleocapsid (NC) domain to nucleic acid. We have investigated the role of SP1, a spacer between CA and NC in HIV-1 Gag, in VLP assembly. Mutational analysis showed that even subtle changes in the first 4 residues of SP1 destroy the ability of Gag to assemble correctly, frequently leading to formation of tubes or other misassembled structures rather than proper VLPs. We also studied the conformation of the CA-SP1 junction region in solution, using both molecular dynamics simulations and circular dichroism. Consonant with nuclear magnetic resonance (NMR) studies from other laboratories, we found that SP1 is nearly unstructured in aqueous solution but undergoes a concerted change to an α-helical conformation when the polarity of the environment is reduced by addition of dimethyl sulfoxide (DMSO), trifluoroethanol, or ethanol. Remarkably, such a coil-to-helix transition is also recapitulated in an aqueous medium at high peptide concentrations. The exquisite sensitivity of SP1 to mutational changes and its ability to undergo a concentration-dependent structural transition raise the possibility that SP1 could act as a molecular switch to prime HIV-1 Gag for VLP assembly. We suggest that changes in the local environment of SP1 when Gag oligomerizes on nucleic acid might trigger this switch.