Interactions of tamoxifen with distearoyl phosphatidylcholine multilamellar vesicles: FTIR and DSC studies

Combined pulsed electric field-ultrasound assisted extraction of yarrow phenolic-rich ingredients and their nanoliposomal encapsulation for improving the oxidative stability of sesame oil

In this research, yarrow phenolic-rich extract was produced using pulsed electric field (PEF)-ultrasound assisted technology. The highest extraction efficiency (5.99 %) was obtained at 6.25 kV/cm of PEF and the sonication time of 60 min. As the PEF intensity and sonication time rose, the total phenolic content (TPC) and ferric-reducing power (RP) of the extracts increased. The PEF intensity of 2.70 kV/cm and sonication time of 45.83 min were the optimum extraction conditions resulting in the highest extraction efficiency, TPC, and RP. Then, this optimum extract was loaded into nanoliposomes. At higher extract levels, the encapsulation efficiency lowered, while the particle size, polydispersity index (PDI), and zeta potential of the nanoliposomal samples elevated. The results of Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) confirmed the successful encapsulation of yarrow extract into nanoliposomal carriers; the sample containing the extract had the highest enthalpy (3600 J/g) and nanoliposomes loaded with yarrow antioxidant extract (0.11 mL/mg) was the optimum sample. Finally, the sesame oil containing 500 ppm free and nanoliposome extract, as well as the sample with 200 ppm BHT were evaluated for oxidative stability. The highest oxidation stability (14.21 h) belonged to the oil containing nanoliposomal yarrow phenolic extract.

Differential scanning calorimetry in drug-membrane interactions

Differential Scanning Calorimetry (DSC) is a central technique in investigating drug - membrane interactions, a critical component of pharmaceutical research. DSC measures the heat difference between a sample of interest and a reference as a function of temperature or time, contributing essential knowledge on the thermally induced phase changes in lipid membranes and how these changes are affected by incorporating pharmacological substances. The manuscript discusses the use of phospholipid bilayers, which can form structures like unilamellar and multilamellar vesicles, providing a simplified yet representative membrane model to investigate the complex dynamics of how drugs interact with and penetrate cellular barriers. The manuscript consolidates data from various studies, providing a comprehensive understanding of the mechanisms underlying drug - membrane interactions, the determinants that influence these interactions, and the crucial role of DSC in elucidating these components. It further explores the interactions of specific classes of drugs with phospholipid membranes, including non-steroidal anti-inflammatory drugs, anticancer agents, natural products with antioxidant properties, and Alzheimer's disease therapeutics. The manuscript underscores the critical importance of DSC in this field and the need for continued research to improve our understanding of these interactions, acting as a valuable resource for researchers.

On the Mechanism of Membrane Permeabilization by Tamoxifen and 4-Hydroxytamoxifen

Tamoxifen (TMX), commonly used in complementary therapy for breast cancer, also displays known effects on the structure and function of biological membranes. This work presents an experimental and simulation study on the permeabilization of model phospholipid membranes by TMX and its derivative 4-hydroxytamoxifen (HTMX). TMX induces rapid and extensive vesicle contents leakage in phosphatidylcholine (PC) liposomes, with the effect of HTMX being much weaker. Fitting of the leakage curves for TMX, yields two rate constants, corresponding to a fast and a slow process, whereas in the case of HTMX, only the slow process takes place. Interestingly, incorporation of phosphatidylglycerol (PG) or phosphatidylethanolamine (PE) protects PC membranes from TMXinduced permeabilization. Fourier-transform infrared spectroscopy (FTIR) shows that, in the presence of TMX there is a shift in the ν_CH2 band frequency, corresponding to an increase in gauche conformers, and a shift in the ν_C=O band frequency, indicating a dehydration of the polar region. A preferential association of TMX with PC, in mixed PC/PE systems, is observed by differential scanning calorimetry. Molecular dynamics (MD) simulations support the experimental results, and provide feasible explanations to the protecting effect of PG and PE. These findings add new information to explain the various mechanisms of the anticancer actions of TMX, not related to the estrogen receptor, and potential side effects of this drug.

Structure and interaction roles in the release profile of chalcone-loaded liposomes

The structures and molecular interactions of established synthetic chalcones were correlated with their release profiles from asolectin liposomes. The effects of chalcones on the properties of liposomes were evaluated by dynamic light scattering (DLS), ultraviolet-visible spectroscopy (UV-VIS), horizontal attenuated total reflection Fourier transform infrared (HATR-FTIR), ³¹P nuclear magnetic resonance (³¹P NMR), zeta (ζ) potential and differential scanning calorimetry (DSC). The profiles and mechanisms of release were accessed according to the Korsmeyer-Peppas model. Results obtained allowed the establishment of a relationship between the chalcone release profile and 1) the ordering effects of chalcones in different membrane regions, 2) their polar or interfacial location in the lipid layer, 3) the influence of hydroxy and methoxy substituents, 4) their effect on reorientation of lipid choline-phosphate regions. The obtained data may improve the development of chalcone-based systems to be used in the therapy of chronic and acute diseases.

Ruscogenin interacts with DPPC and DPPG model membranes and increases the membrane fluidity: FTIR and DSC studies

Ruscogenin, a kind of steroid saponin, has been shown to have significant anti-oxidant, anti-inflammatory, and anti-thrombotic characteristics. Furthermore, it has the potential to be employed as a medicinal medication to treat a variety of acute and chronic disorders. The interaction of a drug molecule with cell membranes can help to elucidate its system-wide protective and therapeutic effects, and it's also important for its pharmacological activity. The molecular mechanism by which ruscogenin affects membrane architecture is still a mystery. Ruscogenin's interaction with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) and anionic dipalmitoyl phosphatidylglycerol (DPPG) multilamellar vesicles (MLVs) was studied utilizing two non-invasive approaches, including: Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry. Ruscogenin caused considerable alterations in the phase transition profile, order, dynamics and hydration state of head groups and glycerol backbone of DPPC and DPPG MLVs at all concentrations. The DSC results indicated that the presence of ruscogenin decreased the main phase transition temperature (T_m) and enthalpy (ΔH) values of both membranes and increased half height width of the main transition (ΔT_1/2). The FTIR results demonstrated that all concentrations (1, 3, 6, 9, 15, 24 and 30 mol percent) of ruscogenin disordered the DPPC MLVs both in the gel and liquid crystalline phases while it increased the order of DPPG MLVs in the liquid crystalline phase. Moreover, ruscogenin caused an increase in the dynamics of DPPC and DPPG MLVs in both phases. Additionally, it enhanced the hydration of the head groups of lipids and the surrounding water molecules implying ruscogenin to interact strongly with both zwitterionic and charged model membranes.

Liposome System for Encapsulation of Spirulina platensis Protein Hydrolysates: Controlled-Release in Simulated Gastrointestinal Conditions, Structural and Functional Properties

This study aimed to evaluate the physicochemical, structural, antioxidant and antibacterial properties of chitosan-coated (0.5 and 1% CH) nanoliposomes containing hydrolyzed protein of Spirulina platensis and its stability in simulated gastric and intestine fluids. The chitosan coating of nanoliposomes containing Spirulina platensis hydrolyzed proteins increased their size and zeta potential. The fourier transform infrared spectroscopy (FT-IR) test showed an effective interaction between the hydrolyzed protein, the nanoliposome, and the chitosan coating. Increasing the concentration of hydrolyzed protein and the percentage of chitosan coating neutralized the decreasing effect of microencapsulation on the antioxidant activity of peptides. Chitosan coating (1%) resulted in improved stability of size, zeta potential, and poly dispersity index (PDI) of nanoliposomes, and lowered the release of the hydrolyzed Spirulina platensis protein from nanoliposomes. Increasing the percentage of chitosan coating neutralized the decrease in antibacterial properties of nanoliposomes containing hydrolyzed proteins. This study showed that 1% chitosan-coated nanoliposomes can protect Spirulina platensis hydrolyzed proteins and maintain their antioxidant and antibacterial activities.

Ultrasonication for production of nanoliposomes with encapsulated soy protein concentrate hydrolysate: Process optimization, vesicle characteristics and in vitro digestion

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Soy protein concentrate hydrolysate (SPH) has been utilized as a mixture of antioxidant peptides.

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Novel ultrasonicated hydrolysate-loaded nanoliposome carriers are developed.

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Encapsulated SPH influenced positively the liposomal nanocarriers' stability.

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Tailored release properties of SPH are shown by in vitro gastrointestinal digestion study.

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Unilamelarity and sphericity of nanoliposomes have been confirmed by TEM and SEM.

This study presents the state-of-art research about the assembly of soy proteins in nanocarriers, liposomes, and its design includes different physicochemical strategies and approaches: two-step enzymatic hydrolysis of soy concentrate, hydrolysate encapsulation by using phospholipids and cholesterol, and application of ultrasonication. Achieved results revealed that ultrasonication, together with cholesterol addition into phospholipid layers, improved the stability of nanoliposomes, and a maximum EE value of 60.5 % was obtained. Average size of peptide-loaded nanoliposomes was found to be from 191.1 to 286.7 nm, with a ζ potential of −25.5 to −34.6 mV, and a polydispersity index of 0.250–0.390. Ultrasound-assisted encapsulation process did not lead to a decrease in the antioxidant activity of the trapped peptides. FTIR has indicated an effective hydrophobic interaction between phosphatidylcholine and hydrolysate peptides. TEM and SEM have confirmed the spherical nanocarrier structure and unilamelarity. Prolonged gastrointestinal release and stability of peptides have been enabled by liposome nanocarriers.

Anticancer drugs tamoxifen and 4hydroxytamoxifen as effectors of phosphatidylethanolamine lipid polymorphism

The interaction of tamoxifen (TMX) and its metabolite 4-hydroxytamoxifen (HTMX) with a biomimetic membrane model system composed of 1,2-dielaidoylphosphatidylethanolamine (DEPE) has been studied using a biophysical approach. Incorporation of TMX into DEPE bilayers gives rise to a progressive broadening of the L_β/L_α phase transition and a downward temperature shift. The L_β/L_α phase transition presents multiple endotherms, indicating a lateral segregation of TMX/DEPE domains within the plane of the bilayer. TMX and HTMX also widen and shift the L_α to hexagonal-H_II transition toward lower values, the phase diagrams showing that both compounds facilitate formation of the H_II phase. TMX increases motional disorder of DEPE acyl chains in the L_β, L_α and H_II phases, whereas the effect of HTMX is clearly different. In addition, neither TMX nor HTMX significantly perturb the hydration state of the polar headgroup region of DEPE. Molecular dynamics (MD) simulations indicate that these drugs do not affect membrane thickness, area per lipid, or the conformation of DEPE molecules. As a general rule, the interaction of HTMX with DEPE is qualitatively similar to TMX but less intense. However, a significant difference shown by MD is that HTMX is mainly placed around the center of each monolayer while TMX is located mainly at the center of the membrane, also having a greater tendency to cluster formation. These results are discussed to understand the modulation of phosphatidylethanolamine lipid polymorphism carried out by these drugs, which could be of relevance to explain their effects on enzyme activity or membrane permeabilization.

Infrared Spectroscopic Study of Multi-Component Lipid Systems: A Closer Approximation to Biological Membrane Fluidity

Membranes are essential to cellular organisms, and play several roles in cellular protection as well as in the control and transport of nutrients. One of the most critical membrane properties is fluidity, which has been extensively studied, using mainly single component systems. In this study, we used Fourier transform infrared spectroscopy to evaluate the thermal behavior of multi-component supported lipid bilayers that mimic the membrane composition of tumoral and non-tumoral cell membranes, as well as microorganisms such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. The results showed that, for tumoral and non-tumoral membrane models, the presence of cholesterol induced a loss of cooperativity of the transition. However, in the absence of cholesterol, the transitions of the multi-component lipid systems had sigmoidal curves where the gel and fluid phases are evident and where main transition temperatures were possible to determine. Additionally, the possibility of designing multi-component lipid systems showed the potential to obtain several microorganism models, including changes in the cardiolipin content associated with the resistance mechanism in Staphylococcus aureus. Finally, the potential use of multi-component lipid systems in the determination of the conformational change of the antimicrobial peptide LL-37 was studied. The results showed that LL-37 underwent a conformational change when interacting with Staphylococcus aureus models, instead of with the erythrocyte membrane model. The results showed the versatile applications of multi-component lipid systems studied by Fourier transform infrared spectroscopy.

MOFs and PDA-supported immobilization of BSA in open tubular affinity capillary electrochromatography: Prediction and study on drug-protein interactions

Owing to the satisfactory properties such as high specific surface area, finely tunable chemical composition, large yet adjustable pore sizes, and diverse architecture, metal-organic frameworks (MOFs) have the potential to be used as a stable, efficient, reusable and protective biomacromolecule immobilization carrier in capillary electrophoresis. Herein, a novel immobilized receptor open-tubular affinity capillary electrochromatography (OT-ACEC) strategy was developed for the first time to rapidly investigate the interactions between a set of drugs and bovine serum albumin (BSA). To further increase the amount of immobilized BSA and maintain the bioactivity of BSA, BSA was immobilized on the inner capillary surface by using polydopamine (PDA) as the adhesion layer and surface functionalization agent, a MOF namely dresden university of technology-5 (DUT-5) as supporting platform and biomacromolecule immobilization carrier, respectively. The amount of immobilized BSA on the capillary surface of the BSA@capillary and the PDA/MOFs/BSA@capillary column are separately calculated as 0.00756 nmol and 0.01812 nmol. Besides, the PDA/MOFs/BSA@capillary column was applied to investigate the interactions between BSA and flavonoids, fluoroquinolones. Under the optimal interaction conditions, three flavonoids and three fluoroquinolones are able to achieve baseline separation in the PDA/MOFs/BSA@capillary column (with resolution values of three flavonoids, 5.78 and 4.13; three fluoroquinolones, 1.72 and 1.68). The PDA/MOFs/BSA@capillary column shows good stability and reproducibility over 100 runs (relative standard deviation (RSD)＜5%). In addition, the normalized capacity factor (K_RCE) in this method replaced the binding constant and was used as an evaluation index to fast predict the activities of 20 drugs, some of which have not yet been reported for their interactions with BSA. Spectroscopy and molecular docking further illuminated the binding mechanism.

Dissimilar action of tamoxifen and 4-hydroxytamoxifen on phosphatidylcholine model membranes

The anticancer drug tamoxifen and its primary metabolite 4-hydroxytamoxifen tend to accumulate in membranes due to its strong hydrophobic character. Thus, in this work we have carried out a systematic study to investigate their effects on model phosphatidylcholine membranes. Tamoxifen and 4-hydroxytamoxifen affect the phase behaviour of phosphatidylcholine model membranes, giving rise to formation of drug/dipalmitoylphosphatidylcholine domains, which is more evident in the case of 4-hydroxytamoxifen. These drugs have differential effects on the polar and apolar regions of the phospholipid supporting a different location of both compounds within the bilayer. Both compounds induce contents leakage in fluid phosphatidylcholine unilamellar liposomes, the effect of 4-hydroxytamoxifen being negligible as compared to that of tamoxifen. Molecular dynamics confirmed the tendency of both drugs to form clusters, tamoxifen locating all along the bilayer, whereas 4-hydroxytamoxifen mostly locates near the lipid/water interface, which can explain the different effects of both drugs in fluid phosphatidylcholine membranes.

Spirulina sp. LEB 18-extracted phycocyanin: Effects on liposomes' physicochemical parameters and correlation with antiradical/antioxidant properties

This study describes the physicochemical properties of soybean asolectin (ASO) liposomes loaded with phycocyanin (Phy) extracted from Spirulina sp. LEB 18. The effects of Phy in the liposomes' properties were investigated by Fourier transform infrared spectroscopy (FTIR), ¹H and ³¹P nuclear magnetic resonance (NMR), zeta (ζ)-potential, dynamic light scattering (DLS) and ultraviolet-visible (UV-vis) techniques. Phy restricted the motion of ASO polar and interface groups and disrupted the package arrangement of the lipid hydrophobic regions, as a likely effect of dipolar and π interactions related to its amino acid residues and pyrrole portions. These interactions were correlated to antiradical/antioxidant Phy responses obtained by 2,2-diphenyl-1-picrylhidrazil (DPPH) assay, thiobarbituric acid reactive substances (TBARS) and ferric reducing antioxidant power (FRAP) methods, and discussed to bring new chemical perspectives about Phy-loaded liposomes-related nutraceutical applications in inflammatory and viral infection processes.

Encapsulation of oyster protein hydrolysates in nanoliposomes: Vesicle characteristics, storage stability, in vitro release, and gastrointestinal digestion

In this study, oyster protein hydrolysates (OPH) were obtained from oyster meat by hydrolysis using animal complex proteases and then encapsulated in nanoliposomes. The physicochemical properties, stability, and digestive characteristics of OPH-loaded nanoliposomes were evaluated. The average size and zeta potential ranged from 95.64 to 102.39 nm and from -47.36 to -36.43 mV, respectively. Liposomes containing 4 mg/mL OPH had the highest encapsulation efficiency (74.53%). Fourier transform infrared spectroscopy analysis showed that effective ionic complexation and hydrogen bonding existed between phospholipid and peptides. The liposomes exhibited the highest stability when stored at 4 °C. Liposomal encapsulation may protect the antioxidant peptides in OPH during storage and simulated digestion. The nanoliposomes were not hydrolyzed and the structural integrity was maintained in gastric digestion, but exhibited lower stability in the intestinal phase. A prolonged release of OPH from nanoliposomes was also observed as compared with free OPH. Liposome containing protein hydrolysates may be used as a formula in functional foods. PRACTICAL APPLICATION: This study provides some useful information on the application of oyster protein hydrolysates or peptides in functional foods. The incorporation into liposomes may protect the hydrolysates against harsh conditions during storage and digestion, and also prolong the release time.

Effect of nanoliposomal entrapment on antioxidative hydrolysates from goose blood protein

In this study, the encapsulation of goose blood hydrolysate (GBH) was performed within nanoliposomes. We investigated the physicochemical properties, stability, antioxidant indices, the morphology of nanoparticles, the digestion stability in simulated gastrointestinal fluid, differential scanning calorimetry (DSC) analysis, and Fourier transform infrared (FTIR) spectroscopy. GBH was successfully encapsulated into nanoliposomes using reverse-phase evaporation method. The entrapment efficiency of GBH-loaded nanoliposomes was about 70.99 ± 2.85%, the average particle size was 93.3 ± 2.45 nm, the zeta-potential of GBH-loaded nanoliposomes was -30 mV, and the morphology of GBH-loaded nanoliposomes was characterized by transmission electron microscope. Moreover, the results of DSC and FTIR showed that the GBH nanoliposome was more stable than the empty liposomes due to hydrogen bond complexation between liposome and GBH. The release of GBH from nanoliposomes could be significantly controlled, and the release ratios were 48.9 ± 2.96% in simulated gastric fluid and 59.9 ± 5.30% in simulated intestinal fluid, respectively, proving that degradation rate of antioxidant activities of GBH encapsulated in nanoliposomes was decreased. In conclusion, nanoliposomes embedding is a promising and effective way to increase the stability of hydrolysates from GBH and produce various types of functional food.

Ratite oils for local transdermal therapy of 4-OH tamoxifen: development, characterization, and ex vivo evaluation

The anti-inflammatory property of ratite oils as well as its ability to act as a penetration enhancer makes it an ideal agent to be used in transdermal formulations. The present study aims to develop an effective transfersomal delivery of 4-hydroxytamoxifen (4-OHT), an anti-cancer drug, using ratite oil as a carrier agent for the treatment of breast cancer (BC). The 4-OHT transfersomes were prepared with and without ratite oils using soy phosphatidylcholine and three different edge activators (EAs) in five different molar ratios using the rotary evaporation-ultrasonication method. Optimal transfersome formulations were selected using physical-chemical characterization and ex vivo studies. Results from physical-chemical characterization of the developed formulations found sodium taurocholate to be the most suitable EA, which recorded highest entrapment efficiency of 95.1 ± 2.70% with 85:15, (w/w) and lowest vesicle size of 82.3 ± 0.02 nm with 75:25, (w/w) molar ratios. TEM and DSC studies showed that the vesicles were readily identified and present in a nearly perfect spherical shape. In addition, formulations with emu oil had better stability than formulations with ostrich oil. Physical stability studies at 4 °C showed that ratite oil transfersomes were stable up to 4 weeks, while transfersomes without ratite oils were stable for 8 weeks. Ex vivo permeability studies using porcine skin concluded that 4-OHT transfersomal formulations with (85:15, w/w) without emu oil have the potential to be used in transdermal delivery approach to enhance permeation of 4-OHT, which may be beneficial in the treatment of BC.

Effect of Tumor Relevant Acidic Environment in the Interaction of a N-hydroxyindole-2-Carboxylic Derivative with the Phospholipid Bilayer

PURPOSE

The inhibitors of the human isoform 5 of lactate dehydrogenase (hLDH5) have attracted growing interest as efficient anti-cancer agents. In the present paper, the interactions between an efficient hLDH5 inhibitor (N-hydroxyindole-2-carboxylic derivative) and lipid bilayers based on dipalmitoylphosphatidylcholine (DPPC) were investigated. Additionally, since interstitial acidification plays a key role in tumor pathogenesis and tumor drug therapy, the effect of acidic pH was assessed and correlated to DPPC/drug interaction.

METHODS

Four different techniques were used: differential scanning calorimetry, dynamic light scattering, UV-VIS second derivative spectrometry and attenuated total reflection Fourier transformed infrared spectroscopy.

RESULTS

All techniques concur in highlighting a structural change of lipid assembly, susceptible both to pH change and to the presence of the antitumor compound. Lipid vesicles appeared more compact at the lower pH, since the thermal pre-transition from the lamellar gel phase to the ripple gel phase was absent at pH 7.4 and the infrared analysis revealed a stronger acyl chain packing as well as a different hydration degree. Drug interaction was mainly detected in the lipid region including the ester linkages and the first portion of the acyl chains. Furthermore, a lower drug partitioning was recorded at pH 6.6.

CONCLUSIONS

The investigated antitumor agent possesses a stable negative charge at the investigated pH values, thus the lower interaction at the acidic pH is mainly ascribable to an environmental effect on lipid assembly. Therefore, drug efficacy under tumor acid conditions may be hampered by the observed lipid membrane constraints, and suggest for the development of suitable prodrugs.

Thermal Response Analysis of Phospholipid Bilayers Using Ellipsometric Techniques

Biomimetic planar artificial membranes have been widely studied due to their multiple applications in several research fields. Their humectation and thermal response are crucial for reaching stability; these characteristics are related to the molecular organization inside the bilayer, which is affected by the aliphatic chain length, saturations, and molecule polarity, among others. Bilayer stability becomes a fundamental factor when technological devices are developed—like biosensors—based on those systems. Thermal studies were performed for different types of phosphatidylcholine (PC) molecules: two pure PC bilayers and four binary PC mixtures. These analyses were carried out through the detection of slight changes in their optical and structural parameters via Ellipsometry and Surface Plasmon Resonance (SPR) techniques. Phospholipid bilayers were prepared by Langmuir-Blodgett technique and deposited over a hydrophilic silicon wafer. Their molecular inclination degree, mobility, and stability of the different phases were detected and analyzed through bilayer thickness changes and their optical phase-amplitude response. Results show that certain binary lipid mixtures—with differences in its aliphatic chain length—present a co-existence of two thermal responses due to non-ideal mixing.

Novel Prodrug of Doxorubicin Modified by Stearoylspermine Encapsulated into PEG-Chitosan-Stabilized Liposomes

Here, we report a new modification of doxorubicin based on an amphiphilic stearoylspermine anchor, enabling loading into liposomal membranes. Doxorubicin is coupled with stearoylspermine through an acid-labile hydrazone linker to ensure the release of the drug in the acidic interstitium of tumors. Using ATR-FTIR spectroscopy (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy), the mechanism of interaction of doxorubicin with the anionic liposomal membrane was studied: incorporation of stearoyl chains leads to an increase in local microfluidity, and the amino groups of spermine interact with the phosphate groups of lipids. To stabilize liposomes against aggregation, we applied the copolymer PEG-chitosan as a coating: complex formation leads to charge neutralization, and the liposomes grow in size. According to MTT tests and confocal microscopy for cell lines A459 and Caco-2, PEG-chitosan-coated liposomes are as effective as neutral liposomes but are much more stable.

Research on drug-receptor interactions and prediction of drug activity via oriented immobilized receptor capillary electrophoresis

Oriented covalent immobilized β2 -adrenergic receptor (β2 -AR) CE (OIRCE) was developed to determine the interactions between a set of natural extracts of Radix Paeoniae Rubra (NERPR) and β2 -AR, and to predict the activity of NERPR. The inner capillary surface is chemically bonded with stable β2 -AR coating via microwave-assisted technical synthesis. The modified capillaries were characterized via infrared spectroscopy and fluorescence microscopy. Furthermore, the bonding amounts of β2 -AR were first obtained via fluorescence spectroscopy method. In determining the amount of bonded β2 -AR, the regression equation A  =  576 707C + 35.449 and the correlation coefficient 0.9995 were obtained. This result revealed an excellent linear relationship in the range of 2 × 10(-4)  mg/mL to 1 × 10(-3)  mg/mL. The normalized capacity factor (KRCE ) was obtained using OIRCE in evaluating drug-receptor interactions. Related theories and equations were used to calculate KRCE values from apparent migration times of a solute and EOF. The order of KRCE and the binding constant (Kb ) values between drugs and β2 -AR was well consistent. The results confirmed that the OIRCE and KRCE values can be effectually used to investigate drug-receptor interactions, and OIRCE has the potential to predict drug activity and to select leading compounds from natural chemicals.

Interactions of the anticancer drug tamoxifen with lipid membranes

Interactions of the hydrophobic anticancer drug tamoxifen (TAM) with lipid model membranes were studied using calcein-encapsulated vesicle leakage, attenuated total reflection Fourier transform infrared (FTIR) spectroscopy, small-angle neutron scattering (SANS), atomic force microscopy (AFM) based force spectroscopy, and all-atom molecular dynamics (MD) simulations. The addition of TAM enhances membrane permeability, inducing calcein to translocate from the interior to the exterior of lipid vesicles. A large decrease in the FTIR absorption band's magnitude was observed in the hydrocarbon chain region, suggesting suppressed bond vibrational dynamics. Bilayer thickening was determined from SANS data. Force spectroscopy measurements indicate that the lipid bilayer area compressibility modulus KA is increased by a large amount after the incorporation of TAM. MD simulations show that TAM decreases the lipid area and increases chain order parameters. Moreover, orientational and positional analyses show that TAM exhibits a highly dynamic conformation within the lipid bilayer. Our detailed experimental and computational studies of TAM interacting with model lipid membranes shed new light on membrane modulation by TAM.

Exploring quercetin and luteolin derivatives as antiangiogenic agents

The formation of new blood vessels from the pre-existing vasculature (angiogenesis) is a crucial stage in cancer progression and, indeed, angiogenesis inhibitors are now used as anticancer agents, clinically. Here we have explored the potential of flavonoid derivatives as antiangiogenic agents. Specifically, we have synthesised methoxy and 4-thio derivatives of the natural flavones quercetin and luteolin, two of which (4-thio quercetin and 4-thio luteolin) had never been previously reported. Seven of these compounds showed significant (p < 0.05) antiangiogenic activity in an in vitro scratch assay. Their activity ranged from an 86% inhibition of the vascular endothelium growth factor (VEGF)-stimulated migration (observed for methoxyquercetin at 10 μM and for luteolin at 1 μM) to a 36% inhibition (for thiomethoxy quercetin at 10 μM). Western blotting studies showed that most (4 out of 7) compounds inhibited phosphorylation of the VEGF receptor-2 (VEGFR2), suggesting that the antiangiogenic activity was due to an interference with the VEGF/VEGFR2 pathway. Molecular modelling studies looking at the affinity of our compounds towards VEGFR and/or VEGF confirmed this hypothesis, and indeed the compound with the highest antiangiogenic activity (methoxyquercetin) showed the highest affinity towards VEGFR and VEGF. As reports from others have suggested that structurally similar compounds can elicit biological responses via a non-specific, promiscuous membrane perturbation, potential interactions of the active compounds with a model lipid bilayer were assessed via DSC. Luteolin and its derivatives did not perturb the model membrane even at concentrations 10 times higher than the biologically active concentration and only subtle interactions were observed for quercetin and its derivatives. Finally, cytotoxicity assessment of these flavonoid derivatives against MCF-7 breast cancer cells demonstrated also a direct anticancer activity albeit at generally higher concentrations than those required for an antiangiogenic effect (10 fold higher for the methoxy analogues). Taken together these results show promise for flavonoid derivatives as antiangiogenic agents.