Exploring the binding mechanism and esterase-like activity of human serum albumin with levofloxacin and its choline based conjugates: A biophysical approach

Human serum albumin (HSA) effectively binds to compounds having different molecular weight and thus facilitates their distribution in the living organisms. Thus, the binding interactions between a potential antibacterial drug (levofloxacin) and synthesized choline based levofloxacinate conjugates with HSA have been explored. The binding efficacy and mechanism were explored by utilizing different spectroscopic techniques; UV-Visible, steady state fluorescence, time resolved fluorescence and esterase-like activity. The interactions between the ligands and protein were electrostatic as well as hydrophobic in nature. The influence of different ligands having different alkyl chain shows quenching of the fluorescence emission of HSA. The spontaneous binding/quenching of HSA with ligands was static in nature, validated by steady state and time resolved fluorescence spectroscopy. Also, the impact of these ligands on the conformation of the native HSA structure was evaluated by using circular dichroism spectroscopy. In combination to the structural change study, the native protein functionality was observed (in terms of 'esterase-like activity') which has been found to be on lower side due to ligand binding. Further, we have performed the reverse study to check the impact of HSA on the fluorescent fluoroquinolone drug. The current study may prove helpful in elucidating the chemico-biological interactions which may prove useful in the pharmaceuticals, pharmacology, and different biochemistry fields.

The interaction between formylphenoxyacetic acid derivatives (chalcone and flavones) and ionic surfactants: Insights into binding constants, solubilisation and physiochemical properties

In this study, UV-vis spectroscopy was employed to investigate the interaction between formylphenoxyacetic acid (FPAA) and its derivatives (chalcone and flavones) with ionic surfactants (SDS, CTAB, and DTAB) in different physiological environments. Changes in the physiochemical properties of FPAA chalcone and flavones including binding constants, partitioning constants, and Gibbs free energy were observed which were influenced by the presence of ionic surfactants computed using mathematical models. The solubilization of the targeted compounds in the ionic surfactants was determined through the binding constant (Kb). The results of the present study indicated that electrostatic interactions played a significant role in the solubilization of the targeted compounds in SDS, CTAB, and DTAB. At pH 4.1, FPAA chalcone exhibited stronger binding affinity with SDS compared to CTAB and DTAB. However, at pH 7.4, chalcone showed stronger binding with DTAB compared to SDS, while negligible interaction with CTAB was observed at pH 7.4. The flavones demonstrated stronger binding with DTAB at pH 7.4 compared to SDS and CTAB and it exhibited strong bonding with CTAB at pH 4.1. The negative values of the Gibbs free energy for binding (ΔGb˚) and partitioning (ΔGp˚) constants displayed the spontaneity of the process. However, FPAA chalcone with SDS and FPAA flavones with DTAB furnished positive ΔGb˚, indicating a non-spontaneous process.

Interaction and antibacterial activity of ciprofloxacin with choline based ionic liquid and CTAB: A comparative spectroscopic study

In this study, the complexation of potential chemo-therapeutic antibacterial drug, ciprofloxacin (CIP) with varying concentrations of surface active compounds (SACs) i.e., (N-(2-hydroxyethyl)-N,N-dimethyl-1-dodecanaminium bromide (12Cho.Br) and cetyltrimethylammonium bromide (CTAB) has been studied. Multispectroscopic techniques were exploited to carry out the study. The higher binding constant (Kb) value for CIP-CTAB than CIP-12Cho.Br obtained from fluorescence data revealed stronger binding of CTAB than 12Cho.Br, owing to the stronger hydrophobic-hydrophobic interaction betweeen CIP and CTAB compared to CIP and 12Cho.Br. The time resolve fluorescence decay shows changes in average lifetime (τavg) with the increasing concentration of 12Cho.Br and CTAB. The changes in τavg suggests that complex formation is taking place between CIP and 12Cho.Br / CTAB. Further, the formation of micelles by 12Cho.Br / CTAB and the effect of alkyl chain length was studied by dynamic light scattering (DLS) and zeta potential to confirm the drug complexation with 12Cho.Br and CTAB. The antibacterial activity has been performed for CIP and 12Cho.Br and CTAB. It was observed that in presence of lower concentrations of 12Cho.Br/ CTAB, the activity of the drug increased. The activity was also found cationic alkyl chain length dependent. Moreover, in-vitro cytotoxicity of CIP and its combinations with 12Cho.Br and CTAB was performed using MTT assay on HEK293 (Human embryonic kidney cells).

Observation of Electrostatically Driven Surface Adsorption in Mixed Surfactant Systems

We employed heterodyne-detected vibrational sum-frequency generation (HD-VSFG) spectroscopy to obtain a molecular-level understanding of the interaction between the anionic surfactant sodium dodecyl ammonium sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB). We observed that these surfactants show a strong cooperative effect on their adsorption to the water-air interface. Even at bulk concentrations 1000 times lower than the critical micelle concentrations of SDS and DTAB, a nearly complete surface surfactant layer is observed when both surfactants are present. This strong enhancement of the surface concentrations of DS- and DTA+ can be quantitatively explained from the favorable Coulomb interaction of the oppositely charged headgroups of DS- and DTA+ and the electrostatic interactions with their counterions. The HD-VSFG results are complemented by a modified Langmuir adsorption model in which we include the free energy associated with the electrostatic interactions of the surfactant ions and their counterions.

Association behavior and physico-chemical parameters of a cetylpyridinium bromide and levofloxacin hemihydrate mixture in aqueous and additive media

The investigation of the micellization of a mixture of cetylpyridinium bromide (CPB) and levofloxacin hemihydrate (LFH) was carried out by a conductivity technique in aqueous and aq. additive mixtures, including NaCl, NaOAc, NaBenz, 4-ABA, and urea. The aggregation behavior of the CPB + LFH mixture was studied considering the variation in additive contents and the change in experimental temperature. The micelle formation of the CPB + LFH mixture was examined from the breakpoint observed in the specific conductivity versus surfactant concentration plots. Different micellar characteristics, such as the critical micelle concentration (CMC) and the extent of counter ion bound (β), were evaluated for the CPB + LFH mixture. The CMC and β were found to undergo a change with the types of solvents, composition of solvents, and working temperatures. The ΔG⁰_m values of the CPB + LFH system in aqueous and aq. additive solutions were found to be negative, which denotes a spontaneous aggregation phenomenon of the CPB + LFH system. The changes in ΔH⁰_m and ΔS⁰_m for the CPB + LFH mixture were also detected with the alteration in the solvent nature and solution temperature. The ΔH⁰_m and ΔS⁰_m values obtained for the association of the CPB + LFH mixture reveal that the characteristic interaction forces may possibly be ion-dipole, dipole-dipole, and hydrophobic between CPB and LFH. The thermodynamics of transfer and ΔH⁰_m-ΔS⁰_m compensation variables were also determined. All the parameters computed in the present investigation are illustrated with proper logic.

A recent overview of surfactant-drug interactions and their importance

This review focuses on the self-aggregation properties of different drugs, as well as on their interaction with anionic, cationic, and gemini surfactants. The interaction of drugs with surfactants has been reviewed concerning conductivity, surface tension, viscosity, density, and UV-Vis spectrophotometric measurements, and their relation with critical micelle concentration (CMC), cloud point, and binding constant. The conductivity measurement technique is used for the micellization of ionic surfactants. Cloud point studies can be used for the non-ionic, and also for certain ionic surfactants. Usually, surface tension studies are mostly employed for non-ionic surfactants. The degree of dissociation that is determined is used to evaluate thermodynamic parameters of micellization at various temperatures. The effect of external parameters like temperature, salt, solvent, pH, etc., is discussed for thermodynamics parameters using recent experimental works on drug-surfactant interactions. Consequences of drug-surfactant interaction, condition of drugs during interaction with surfactants, and applications of drug-surfactant interaction are being generalized which reflects current and future potential uses of drug-surfactant interactions.

Investigation of the impacts of simple electrolytes and hydrotrope on the interaction of ceftriaxone sodium with cetylpyridinium chloride at numerous study temperatures

Herein, interactions between cetylpyridinium chloride (CPC) and ceftriaxone sodium (CTS) were investigated applying conductivity technique. Impacts of the nature of additives (e.g. electrolytes or hydrotrope (HDT)), change of temperatures (from 298.15 to 323.15 K), and concentration variation of CTS/additives were assessed on the micellization of CPC + CTS mixture. The conductometric analysis of critical micelle concentration (CMC) with respect to the concentration reveals that the CMC values were increased with the increase in CTS concentration. In terms of using different mediums, CMC did not differ much with the increase in electrolyte salt (NaCl, Na2SO4) concentration, but increased significantly with the rise of HDT (NaBenz) amount. In the presence of electrolyte, CMC showed a gentle increment with temperature, while the HDT showed the opposite trend. Obtained result was further correlated with conventional thermodynamic relationship, where standard Gibb's free energy change ( Δ G m o ) , change of enthalpy ( Δ H m o ) , and change of entropy ( Δ S m o ) were utilized to investigate. The Δ G m o values were negative for all the mixed systems studied indicating that the micellization process was spontaneous. Finally, the stability of micellization was studied by estimating the intrinsic enthalpy gain (Δ H m o , ∗ ) and compensation temperature (Tc). Here, CPC + CTS mixed system showed more stability in Na2SO4 medium than the NaCl, while in NaBenz exhibited the lowest stability.

The effect of polysorbate 20 and polysorbate 80 on the solubility of quercetin

Background: Quercetin acts as an antioxidant, anti-inflammatory, wound healing, and anti-aging so quercetin can be used as a topical preparation. However, it has low solubility in water at 0.01 mg/ml at 25°C. Increasing the solubility of quercetin in water was done by the addition of surfactants. Objective: This study compared the solubility of quercetin in Polysorbate 20 (P20) and Polysorbate 80 (P80) in a citrate buffer medium pH 4.5±0.2. Methods: The surfactants Polysorbate 80 and Polysorbate 20 differ in their alkyl chain length. Polysorbate 80 has an alkyl chain length of 18, while Polysorbate 20 has an alkyl chain length of 12. The concentrations of surfactant are above, below, and at the critical micelle concentration (CMC) values. The concentrations of quercetin were determined at the maximum wavelength by spectrophotometric method. Results: The results of the quercetin solubility test without surfactant were 3.89±0.59 mg/L. The results of the quercetin solubility test by adding Polysorbate 20 at a concentration of 42.0 ppm; 57.5 ppm; and 73.0 ppm were 3.62±0.72, 4.04±0.23 and 8.35±1.97 mg/L, respectively. While the solubility of quercetin by adding Polysorbate 80 at a concentration of 4.0 ppm, 11.5 ppm, and 19.0 ppm was 11.15±0.72, 11.37±1.23 and 14.17±1.96 mg/L, respectively. The solubility of quercetin is greater after the addition of surfactant Polysorbate 20 only at the concentration above the CMC value and the solubility of quercetin is greater with the addition of surfactant Polysorbate 80 at all concentrations. Surfactant Polysorbate 20 increases the solubility of quercetin in citrate buffer pH 4.5±0.2 only at concentrations above the CMC value of 2.14 times. Polysorbate 80 can increase the solubility of quercetin in citrate buffer pH 4.5±0.2 at concentrations below, at, and above CMC by 2.87, 2.92, and 3.63 times, respectively. Conclusion: Polysorbate 80 can increase the solubility of quercetin in citrate buffer pH 4.5±0.2 higher than Polysorbate 20.

Spectroscopic and DFT study of imidazolium based ionic liquids with broad spectrum antibacterial drug levofloxacin

Herein, we have shown the interaction of levofloxacin (LVF) with two imidazolium based ionic liquids (ILs), 1-butly-3-methylimidazolium chloride ([Bmim][Cl]) and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]) by utilising spectroscopic techniques along with computational approach. Both [Bmim][Cl] and [Dmim][Cl] quenched the fluorescence emission of LVF suggesting complex formation between ILs and the drug. The steady-state and time-resolve fluorescence studies revealed that the quenching of fluorescence emission of LVF in the presence of [Bmim][Cl] and [Dmim][Cl], which signified the non-fluorescent complex formation between LVF and ILs. The complex formation between LVF and ILs were also validated by the UV-visible spectroscopy method. The cyclic voltammetry (CV) results further suggest the strong interaction between LVF and ILs. The estimated binding constant (K_b) and free energy change (ΔG) parameters shows the substantial binding of LVF with both the ILs and spontaneous in nature. The value suggested that LVF have stronger binding with [Dmim][Cl] than [Bmim][Cl]. Further, in order to support the results classical density functional theory (DFT) model was performed. The DFT calculations were utilized to explore the 3D structure and the molecular orbitals (HOMO and LUMO) of ILs, LVF and their complexes using Gaussian 09 software. The aggregate size (D_h) and zeta potential of ILs and IL-drug complexes were determined by dynamic light scattering (DLS) and zeta potential in aqueous medium.

The Influence of Lipid Matrix Composition on the Microenvironment of Levofloxacin in Liposomal Forms

We have studied the interaction of the antibacterial drug levofloxacin with lipid bilayers of various compositions: 100% DPPC and with the addition of 20% cardiolipin. For DPPC liposomes, levofloxacin was found to penetrate into the subpolar region at the lipid-water interface. The role of the anionic lipid in the interaction of an active molecule with a bilayer has been established: levofloxacin enters the microenvironment of the phosphate group, displacing water, and does not penetrate into the hydrophobic part of the bilayer. For the first time, the study of the microenvironment of levofloxacin in the liposome by IR and CD spectroscopy was carried out. Such an approach based on a combination of several spectral methods opens up new prospects for the creation of new medicinal properties and the possibility of predicting the nature of the interaction of active molecules with biomembranes in order to predict their efficacy and potential side effects.

Preparation of Antibacterial Gelatin/Genipin Nanofibrous Membrane for Tympanic Membrane Repair

Tympanic membrane perforation (TMP), a common disease, often needs a scaffold as the patch to support surgery. Due to the environment of auditory meatus, the patch can be infected by bacteria that results in failure; therefore, the ideal scaffold may combine biomimetic and antibacterial features. In this work, gelatin was used as the electrospinning framework, genipin as the crosslinking agent, and levofloxacin as an antibacterial in order to prepare the scaffold for TMP. Different contents of levofloxacin have been added to gelatin/genipin. It was found that, with the addition of levofloxacin, the gelatin/genipin membranes exhibit improved hydrophilia and enhanced tensile strength. The antibacterial and cell-cultured experiments showed that the prepared antibacterial membranes had excellent antibacterial properties and good biocompatibility, respectively. In summary, levofloxacin is a good group for the gelatin/genipin scaffold because it improves the physical properties and antibacterial action. Compared with different amounts of levofloxacin, a gelatin/genipin membrane with 1% levofloxacin is more suitable for a TM.

Drug Solubilization by Surfactants: Experimental Methods and Theoretical Perspectives

This mini review will give an insight into the need and usefulness of investigating the solubilization of poorly soluble drugs. Commonly used experimental and theoretical models are outlined to study the efficacy of the carrier or excipient for the poorly soluble drugs. Furthermore, the use of surface active agents for drug solubilization is discussed in correlation with the mathematical models suggested from time to time. A few experimental techniques are also discussed which would be very helpful in elucidating the interactions prevailing in the mixed systems of poorly soluble drugs and surface active agents.

Tetracycline Water Soluble Formulations with Enhanced Antimicrobial Activity

The negligible water solubility of tetracycline (TC), a well-known antibiotic of clinical use, is the major disadvantage for its oral administration. With the aim to improve the water solubility of TC, the micelles of formulae SLS@TC and CTAB@TC (SLS = sodium lauryl sulphate and CTAB = cetrimonium bromide) were synthesized. The micelles SLS@TC and CTAB@TC were characterized by melting point (m.p.), thermogravimetric differential thermal analysis (TG-DTA), differential scanning calorimetry (DTG/DSC), attenuated total reflection spectroscopy (FT-IR-ATR), ultra-violet visible (UV/vis) spectroscopy, proton nucleus magnetic resonance (1H-NMR) spectroscopy, and the ultrasonically-induced biregringence technique. The antimicrobial activity of SLS@TC and CTAB@TC was evaluated, by means of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and inhibition zone (IZ), against the Gram negative bacterial strains Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) and the Gram positive ones of the genus of Staphylococcus epidermidis (S. epidermidis) and Staphylococcus aureus (S. aureus). Generally, both micelles show better activity than that of TC against the microbial strains tested. Thus, the MIC value of CTAB@TC is 550-fold higher than that of free TC against S. epidermidis. Despite the stronger activity of CTAB@TC than SLS@TC against both Gram negative and Gram positive microbes, SLS@TC is classified as a bactericidal agent (in that it eliminates 99.9% of the microbes), in contrast to CTAB@TC, which is bacteriostatic one (inhibits, but does not kill the organisms). The toxicity of SLS@TC and CTAB@TC was evaluated against human corneal eukaryotic cells (HCECs). Moreover, SLS@TC and CTAB@TC exhibit low in vivo toxicity against Artemia salina, even at concentrations up to threefold higher than those of their MICmax. Therefore, SLS@TC and CTAB@TC can be candidates for the development of new antibiotics.

Effects of temperature and polyols on the ciprofloxacin hydrochloride-mediated micellization of sodium dodecyl sulfate

Herein, a conductivity method was engaged to explore the effects of a fluoroquinolone drug, namely ciprofloxacin hydrochloride (CFH)/CFH + polyols (organic compounds with multiple hydroxyl groups (glucose and fructose)), on the aggregation phenomenon of sodium dodecyl sulfate (SDS) at different temperatures (298.15–318.15 K) while maintaining a gap of 5 K. In this study, the critical micelle concentration (cmc) of the SDS/SDS + CFH mixture in water and polyols media was determined from plots of the specific conductivity versus the concentration of SDS to gain knowledge of the effects of CFH/CFH + polyols on the micelle formation behavior of SDS. The cmc value of the surfactant decreases in the presence of CFH in an aqueous medium; thus, CFH favors the micellization of SDS. The cmc values of SDS and the SDS + CFH mixture were enhanced in polyols media. The cmc values of SDS/SDS + CFH show a U-shaped behavior with temperature. The counterion dissociation (α) of the pure surfactant is higher in the presence of the drug and is further enhanced through an increase in the CFH concentration in water/polyols media. Different thermodynamic parameters, such as the Gibbs free energy of micellization , standard enthalpy , entropy , different transfer energies and enthalpy–entropy compensation parameters of micellization were determined and illustrated in detail to compare these parameters between the pure SDS and SDS + CFH mixture in polyols media. The negative values of for the SDS/SDS + CFH mixture in all cases indicate spontaneous micelle formation. The and values indicate the presence of both hydrophobic and electrostatic interactions amongst the studied components.

A conductivity method was used to see effects of a ciprofloxacin hydrochloride (CFH)/CFH + polyols (organic compounds with multiple hydroxyl groups (glucose and fructose)) on aggregation phenomenon of sodium dodecyl sulfate (SDS) at 298.15–318.15 K.