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.

Protective Role of a Donepezil-Huprine Hybrid against the ß-Amyloid (1-42) Effect on Human Erythrocytes.

Aß(1-42) peptide is a neurotoxic agent strongly associated with the etiology of Alzheimer's disease (AD). Current treatments are still of very low effectiveness, and deaths from AD are increasing worldwide. Huprine-derived molecules have a high affinity towards the enzyme acetylcholinesterase (AChE), act as potent Aß(1-42) peptide aggregation inhibitors, and improve the behavior of experimental animals. AVCRI104P4 is a multitarget donepezil-huprine hybrid that improves short-term memory in a mouse model of AD and exerts protective effects in transgenic Caenorhabditis elegans that express Aß(1-42) peptide. At present, there is no information about the effects of this compound on human erythrocytes. Thus, we considered it important to study its effects on the cell membrane and erythrocyte models, and to examine its protective effect against the toxic insult induced by Aß(1-42) peptide in this cell and models. This research was developed using X-ray diffraction and differential scanning calorimetry (DSC) on molecular models of the human erythrocyte membrane constituted by lipid bilayers built of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). They correspond to phospholipids representative of those present in the external and internal monolayers, respectively, of most plasma and neuronal membranes. The effect of AVCRI104P4 on human erythrocyte morphology was studied by scanning electron microscopy (SEM). The experimental results showed a protective effect of AVCRI104P4 against the toxicity induced by Aß(1-42) peptide in human erythrocytes and molecular models.

Phytochemical Analysis and Antioxidant and Anti-Inflammatory Capacity of the Extracts of Fruits of the Sechium Hybrid.

In addition to their own antioxidants, human cells feed on external antioxidants, such as the phenolic compounds of fruits and vegetables, which work together to keep oxidative stress in check. Sechium edule, an edible species of chayote, has phenolic compounds with antioxidant activity and antineoplastic activity. A Sechium hybrid shows one thousand times greater antineoplastic activity than edible species, but its antioxidant and anti-inflammatory activities and the content of phenolic compounds are unknown. The aim of this study was to determine the antioxidant and anti-inflammatory capacity of the extract of fruits of the Sechium hybrid in vitro and in vivo. Phytochemical analysis using HPLC showed that the extract of the Sechium hybrid has at least 16 phenolic compounds; galangin, naringenin, phloretin and chlorogenic acid are the most abundant. In an in vitro assay, this extract inhibited 2,2-diphenyl-L-picrylhydrazyl (DPPH) activity and protected the dimyristoylphosphatidylethanolamine (DMPE) phospholipid model cell membrane from oxidation mediated by hypochlorous acid (HClO). In vivo, it was identified that the most abundant metabolites in the extract enter the bloodstream of the treated mice. On the other hand, the extract reduces the levels of tumor necrosis factor alpha (TNFα), interferon gamma (IFNγ), and interleukin-6 (IL-6) but increases interleukin-10 (IL-10) and glutathione peroxidase levels. Our findings indicate that intake of the fruits of the Sechium hybrid leads to antioxidant and anti-inflammatory effects in a mouse model. Therefore, these results support the possibility of exploring the clinical effect of this hybrid in humans.

Antioxidant effect of resveratrol in single red blood cells measured by thermal fluctuation spectroscopy.

The human red blood cell (RBC) membrane has significant elastic capabilities which can be described measuring typical membrane edge fluctuations and mechanical properties by optical techniques. The RBC elastic properties can be affected by changes in the surrounding media. In an attempt to elucidate the molecular mechanisms of the interaction of resveratrol with the red cell membrane and of its antioxidant capacity the changes in mechanical properties of the RBC membrane were analyzed. These studies were carried out through measurements of RBC membrane fluctuations in the presence of the oxidant agent HClO using thermal fluctuation spectroscopy (TFS). The observed results showed that the elastic capabilities of RBC changed with low concentration of hypochlorous acid but without morphological changes. However, in the presence of resveratrol the deformation and decrease of elastic capabilities induced by HClO on RBC decreased. These in vitro results demonstrated the protective effect of RV against the detrimental effects triggered by HClO upon human erythrocytes.

An in vitro study of the protective effect of caffeic acid on human erythrocytes.

The interaction and protective effect of caffeic acid (CA) on human erythrocytes (RBC) and molecular models of its membrane were studied. The latter consisted of bilayers built up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry results indicated that CA induced structural and thermotropic perturbations in multilayers and vesicles of DMPC. Fluorescence spectroscopy analysis showed that CA increased the fluidity of DMPC vesicles and of human erythrocyte ghosts. Scanning electron microscopy observations displayed that CA induced morphological alterations to RBC from their normal discoid form to echinocytes. The assessment of its protective capacity showed that CA inhibits RBC morphological alterations and lysis induced by HClO. These findings imply that CA molecules were located in the outer monolayer of the erythrocyte membrane, and that this preferential location might effectively protect the red cells from damage caused by oxidizing species.

α1-and ß-adrenergic antagonist labetalol induces morphological changes in human erythrocytes.

Labetalol is one of the most used drugs for the treatment of hypertension. This molecule is able to bind to both alpha-1 (α1) and beta (ß) adrenergic receptors present in vascular smooth muscle among other tissues. It has been determined that human erythrocytes possess both alpha receptors and beta-adrenergic receptors expressed on their surface. The objective of this work was to study the effect of labetalol on the morphology of human erythrocytes. To accomplish this goal, human erythrocytes and model membranes built of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. These lipid species are present in the outer and inner monolayers of the red blood cell membrane, respectively. Our findings obtained by X-ray diffraction and differential scanning calorimetry (DSC) indicate that labetalol interacted with both lipids in a process dependent on concentration. In fact, at low concentrations labetalol preferentially interacted with DMPE. On the other hand, results obtained by scanning electron microscopy (SEM) showed that labetalol alters the normal biconcave form of erythrocytes to stomatocytes and knizocytes (cells with one or more cavities, respectively). According to the bilayers couple hypothesis, this result implied that the drug inserted in the inner monolayer of the human erythrocyte membrane.

Biophysical study of the non-steroidal anti-inflammatory drugs (NSAID) ibuprofen, naproxen and diclofenac with phosphatidylserine bilayer membranes.

Non-steroidal anti-inflammatory drugs (NSAIDs) represent an effective pain treatment option and therefore one of the most sold therapeutic agents worldwide. The study of the molecular interactions responsible for their physiological activity, but also for their side effects, is therefore important. This report presents data on the interaction of the most consumed NSAIDs (ibuprofen, naproxen and diclofenac) with one main phospholipid in eukaryotic cells, dimyristoylphosphatidylserine (DMPS). The applied techniques are Fourier-transform infrared spectroscopy (FTIR), with which in transmission the gel to liquid crystalline phase transition of the acyl chains in the absence and presence of the NSAID are monitored, supplemented by differential scanning calorimetry (DSC) data on the phase transition. FTIR in reflection (ATR, attenuated total reflectance) is applied to record the dependence of the interactions of the NSAID with particular functional groups observed in the DMPS spectrum such as the ester carbonyl and phosphate vibrational bands. With Förster resonance energy transfer (FRET) a possible intercalation of the NSAID into the DMPS liposomes and with isothermal titration calorimetry (ITC) the thermodynamics of the interaction are monitored. The data show that the NSAID react in a particular way with this lipid, but in some parameters the three NSAID clearly differ, with which now a clear picture of the interaction processes is possible.

In vitro effects of the anti-Alzheimer drug memantine on the human erythrocyte membrane and molecular models.

Memantine is a NMDA antagonist receptor clinically used for treating Alzheimer's disease. NMDA receptors are present in the human neurons and erythrocyte membranes. The aim of the present study was to investigate the effects of memantine on human erythrocytes. With this purpose, the drug was developed to in vitro interact with human red cells and bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). The latter represent lipids respectively present in both outer and inner monolayers of the red cell membrane. Results obtained by scanning electron microscopy (SEM) showed that memantine changed the normal biconcave shape of red cells to cup-shaped stomatocytes. According to the bilayer-couple hypothesis the drug intercalated into the inner monolayer of the erythrocyte membrane. Experimental results obtained by X-ray diffraction on multibilayers of DMPC and DMPE, and by differential scanning calorimetry on multilamellar vesicles indicated that memantine preferentially interacted with DMPC in a concentration-dependent manner. Thus, it can be concluded that in the low therapeutic plasma concentration of circa 1 µM memantine is located in NMDA receptor channel without affecting the erythrocyte shape. However, at higher concentrations, once the receptors became saturated excess of memantine molecules (20 µM) would interact with phosphoinositide lipids present in the inner monolayer of the erythrocyte membrane inducing the formation of stomatocytes. However, 40-50 µM memantine was required to interact with isolated phosphatidylcholine bilayers.

An In Vitro Study of the Antioxidant and Antihemolytic Properties of Buddleja globosa (Matico).

The antioxidant and antihemolytic properties contained in the leaves of Buddleja globosa (B. globosa), also known as "Matico," were determined. Aqueous extracts of leaves were assayed in human erythrocytes and molecular models of its membrane. The latter were bilayers built-up of lipids located in the outer and inner leaflets of the erythrocyte membrane. Observations by scanning electron microscopy showed that the extract altered the morphology of erythrocytes inducing the formation of crenated echinocytes. This result implied that the extract components were inserted into the outer leaflet of the cell membrane. This conclusion was confirmed by experiments carried out by fluorescence spectroscopy of red cell membranes and vesicles (LUV) of dimyristoylphosphatidylcholine (DMPC) and by X-ray diffraction of DMPC and dimyristoylphosphatidylethanolamine bilayers. Human erythrocytes were in vitro exposed to HClO, which is a natural powerful oxidant. Results demonstrated that low concentrations of B. globosa aqueous extract neutralized the harmful capacity of HClO. Hemolysis experiments also showed that the extract in very low concentrations reduced hemolysis induced by HClO.

Effects of Thimerosal on Lipid Bilayers and Human Erythrocytes: An In Vitro Study.

Thimerosal (THI, ethyl-mercury thiosalicylate) is added to vaccines as a preservative; as a consequence, infants may have been exposed to bolus doses of Hg that collectively added up to nominally 200 µg Hg during the first 6 months of life. While several studies report an association between THI-containing vaccines and neurological disorders, other studies do not support the causal relation between THI and autism. With the purpose to understand the molecular mechanisms of the toxic effect of THI it was assayed on human red cells and in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), classes of phospholipids found in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of THI to interact with DMPC and DMPE was determined by X-ray diffraction and differential scanning calorimetry, whereas intact human erythrocytes were observed by optical, defocusing and scanning electron microscopy. The experimental findings of this study demonstrated that THI interacted in a concentration-dependent manner with DMPC and DMPE bilayers, and in vitro interacted with erythrocytes inducing morphological changes. However, concentrations were considerable higher than those present in vaccines.

Morphological Effects and Antioxidant Capacity of Solanum crispum (Natre) In Vitro Assayed on Human Erythrocytes.

In order to gain insight into the molecular mechanism of the antioxidant properties of Solanum crispum, aqueous extracts of its leaves were assayed on human erythrocytes and molecular models of its membrane. Phenolics and alkaloids were detected by HPLC-MS. Scanning electron and defocusing microscopy showed that S. crispum changed erythrocytes from the normal shape to echinocytes. These results imply that molecules present in the aqueous extracts were located in the outer monolayer of the erythrocyte membrane. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. X-ray diffraction showed that S. crispum preferentially interacted with DMPC bilayers. Experiments regarding its antioxidant properties showed that S. crispum neutralized the oxidative capacity of HClO on DMPE bilayers; defocusing microscopy and hemolysis assays demonstrated the protective effect of S. crispum against the oxidant effects of HClO on human erythrocytes.

Antioxidant Capacity of Gallic Acid in vitro Assayed on Human Erythrocytes.

Gallic acid (GA) is a polyphenol present in many plants. This study was aimed to investigate the molecular interaction of GA with the human erythrocyte membrane and to determine its antioxidant capacity. The molecular interaction with the membrane of human red cells and the antioxidant property was assayed on both human red cells and molecular models of its membrane. Observations by optical, scanning electron, and defocusing microscopy demonstrated that GA is capable to convert red cells from their normal biconcave shape to crenated echinocytes. This result indicates that GA molecules are positioned in the outer monolayer of the red cell membrane. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were selected as classes of phospholipids found in the outer and inner monolayers of the red cell membrane, respectively. X-ray diffraction and differential scanning calorimetry showed that GA was preferentially bound to DMPC bilayers. Experiments related to the antioxidant capacity of GA indicated that this compound offsets HClO oxidative capacity on DMPE bilayers. In addition, optical, scanning, defocusing microscopy, and hemolysis assays confirmed the protective capacity of GA against HClO deleterious effects on human red cells. As a conclusion, GA would be capable to block the access of oxidants into the lipid bilayer, and thus avoid their access into red cells.

Structural effects of the Solanum steroids solasodine, diosgenin and solanine on human erythrocytes and molecular models of eukaryotic membranes.

This report presents evidence that the following Solanum steroids: solasodine, diosgenin and solanine interact with human erythrocytes and molecular models of their membranes as follows: a) X-ray diffraction studies showed that the compounds at low molar ratios (0.1-10.0mol%) induced increasing structural perturbation to dimyristoylphosphatidylcholine bilayers and to a considerable lower extent to those of dimyristoylphosphatidylethanolamine; b) differential scanning calorimetry data showed that the compounds were able to alter the cooperativity of dimyristoylphosphatidylcholine, dimyristoylphosphatidylethanolamine and dimyristoylphosphatidylserine phase transitions in a concentration-dependent manner; c) in the presence of steroids, the fluorescence of Merocyanine 540 incorporated to the membranes decreased suggesting a fluidization of the lipid system; d) scanning electron microscopy observations showed that all steroids altered the normal shape of human erythrocytes inducing mainly echinocytosis, characterized by the formation of blebs in their surfaces, an indication that their molecules are located into the outer monolayer of the erythrocyte membrane.

Morphological Effects Induced In Vitro by Propranolol on Human Erythrocytes.

Despite the extended use and well-documented information, there are insufficient reports concerning the effects of propranolol on the structure and functions of cell membranes, particularly those of human erythrocytes. Aimed to better understand the molecular mechanisms of its interactions with cell membranes, human erythrocyte and molecular models of the red cell membrane were utilized. The latter consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of propranolol to perturb the multibilayer structures of DMPC and DMPE was evaluated by X-ray diffraction. Moreover, we took advantage of the capability of differential scanning calorimetry to detect the changes in the thermotropic phase behavior of lipid bilayers resulting from propranolol interaction with DMPC and DMPE multilamellar vesicles. In an attempt to further elucidate their effects on cell membranes, the present work also examined their influence on the morphology of intact human erythrocytes by means of defocusing and scanning electron microscopy. Results indicated that propranolol induced morphological changes to human erythrocytes and interacted in a concentration-dependent manner with phospholipid bilayer.

Antioxidant capacity of Ugni molinae fruit extract on human erythrocytes: an in vitro study.

Ugni molinae is an important source of molecules with strong antioxidant activity widely used as a medicinal plant in Southern Chile-Argentina. Total phenol concentration from its fruit extract was 10.64 ± 0.04 mM gallic acid equivalents. Analysis by means of HPLC/MS indicated the presence of the anthocyanins cyanidin and peonidin, and the flavonol quercitin, all in glycosylated forms. Its antioxidant properties were assessed in human erythrocytes in vitro exposed to HClO oxidative stress. Scanning electron microscopy showed that HClO induced an alteration in erythrocytes from a normal shape to echinocytes; however, this change was highly attenuated in samples containing U. molinae extracts. It also had a tendency in order to reduce the hemolytic effect of HClO. In addition, X-ray diffraction experiments were performed in dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine bilayers, classes of lipids preferentially located in the outer and inner monolayers, respectively, of the human erythrocyte membrane. It was observed that U. molinae only interacted with DMPC. Results by fluorescence spectroscopy on DMPC large unilamellar vesicles and isolated unsealed human erythrocyte membranes also showed that it interacted with the erythrocyte membrane and DMPC. It is possible that the location of U. molinae components into the membrane outer monolayer might hinder the diffusion of HClO and of free radicals into cell membranes and the consequent decrease of the kinetics of free radical reactions.

Effects of an antimalarial quinazoline derivative on human erythrocytes and on cell membrane molecular models.

Plasmodium, the parasite which causes malaria in humans multiplies in the liver and then infects circulating erythrocytes. Thus, the role of the erythrocyte cell membrane in antimalarial drug activity and resistance has key importance. The effects of the antiplasmodial N(6)-(4-methoxybenzyl)quinazoline-2,4,6-triamine (M4), and its inclusion complex (M4/HPßCD) with 2-hydroxypropyl-ß-cyclodextrin (HPßCD) on human erythrocytes and on cell membrane molecular models are herein reported. This work evidences that M4/HPßCD interacts with red cells as follows: a) in scanning electron microscopy (SEM) studies on human erythrocytes induced shape changes at a 10µM concentration; b) in isolated unsealed human erythrocyte membranes (IUM) a concentration as low as 1µM induced sharp DPH fluorescence anisotropy decrease whereas increasing concentrations produced a monotonically decrease of DPH fluorescence lifetime at 37°C; c) X-ray diffraction studies showed that 200µM induced a complete structural perturbation of dimyristoylphosphatidylcholine (DMPC) bilayers whereas no significant effects were detected in dimyristoylphosphatidylethanolamine (DMPE) bilayers, classes of lipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively; d) fluorescence spectroscopy data showed that increasing concentrations of the complex interacted with the deep hydrophobic core of DMPC large unilamellar vesicles (LUV) at 18°C. All these experiments are consistent with the insertion of M4/HPßCD in the outer monolayer of the human erythrocyte membrane; thus, it can be considered a promising and novel antimalarial agent.

Acetylsalicylic acid (aspirin) and salicylic acid interaction with the human erythrocyte membrane bilayer induce in vitro changes in the morphology of erythrocytes.

Despite the well-documented information, there are insufficient reports concerning the effects of salicylate compounds on the structure and functions of cell membranes, particularly those of human erythrocytes. With the aim to better understand the molecular mechanisms of the interaction of acetylsalicylic acid (ASA) and salicylic acid (SA) with cell membranes, human erythrocyte membranes and molecular models were utilized. These consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of ASA and SA to perturb the multibilayer structures of DMPC and DMPE was evaluated by X-ray diffraction while DMPC unilamellar vesicles (LUV) were studied by fluorescence spectroscopy. Moreover, we took advantage of the capability of differential scanning calorimetry (DSC) to detect the changes in the thermotropic phase behavior of lipid bilayers resulting from ASA and SA interaction with PC and PE molecules. In an attempt to further elucidate their effects on cell membranes, the present work also examined their influence on the morphology of intact human erythrocytes by means of defocusing and scanning electron microscopy, while isolated unsealed human erythrocyte membranes (IUM) were studied by fluorescence spectroscopy. Results indicated that both salicylates interact with human erythrocytes and their molecular models in a concentration-dependent manner perturbing their bilayer structures.

Effects of sodium metavanadate on in vitro neuroblastoma and red blood cells.

Toxicity of vanadium on cells is one of the less studied effects. This prompted us to study the structural effects induced on neuroblastoma and erythrocytes by vanadium (V) sodium metavanadate. This salt was incubated with mice cholinergic neuroblastoma cells and intact human erythrocytes. To learn whether metavanadate interacts with membrane lipid bilayers it was incubated with bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). These are phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. Exposure of neuroblastoma cells to metavanadate showed significant decreases in cell viability as well as in cell number correlating with inhibition of aconitase activity. In scanning electron microscopy (SEM) and defocusing microscopy (DM) it was observed that induced on erythrocytes the formation of echinocytes. However, no effects were obtained when metavanadate was made to interact with DMPC and DMPE multibilayers and liposomes, assays performed by X-ray diffraction and differential scanning calorimetry (DSC), respectively. These results imply that the effects of metavanadate on erythrocytes are through interactions with proteins located in the membrane outer moiety, and could still involve other minor lipid components as well. Also, partly unsaturated lipids could interact differently the fully saturated chains in the model systems.

A rhein-huprine hybrid protects erythrocyte membrane integrity against Alzheimer's disease related Aß(1-42) peptide.

Alzheimer's disease remains largely unknown, and currently there is no complete cure for the disease. New synthetic approaches have been developed to create multi-target agents, such as RHE-HUP, a rhein-huprine hybrid which can modulate several biological targets that are relevant to the development of the disease. While RHE-HUP has shown in vitro and in vivo beneficial effects, the molecular mechanisms by which it exerts its protective effect on cell membranes have not been fully clarified. To better understand RHE-HUP interactions with cell membranes, we used synthetic membrane models and natural models of human membranes. For this purpose, human erythrocytes and molecular model of its membrane built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. The latter correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry (DSC) results indicated that RHE-HUP was able to interact mainly with DMPC. In addition, scanning electron microscopy (SEM) analysis showed that RHE-HUP modified the normal biconcave shape of erythrocytes inducing the formation of echinocytes. Moreover, the protective effect of RHE-HUP against the disruptive effect of Aß(1-42) on the studied membrane models was tested. X-ray diffraction experiments showed that RHE-HUP induced a recovery in the ordering of DMPC multilayers after the disruptive effect of Aß(1-42), confirming the protective role of the hybrid.

Human cells and cell membrane molecular models are affected in vitro by the nonsteroidal anti-inflammatory drug ibuprofen.

This report presents evidence that ibuprofen interacts with red cell membranes as follows: a) in scanning electron microscopy (SEM) studies on human erythrocytes induced shape changes at a concentration as low as 10µM; b) in isolated unsealed human erythrocyte membranes (IUM) induced mild increase in the water content or in their molecular dynamics at the hydrophobic-hydrophilic interphase, while a corresponding ordering decrease at the deep phospholipids acyl chain level; c) at physiological temperature (37°C), 300µM ibuprofen induced a significant increase in the generalized polarization (GP) of dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles (LUV), an indication that ibuprofen molecules locate in the head polar group region of DMPC; d) X-ray diffraction studies showed that ibuprofen concentrations≥300µM induced increasing structural perturbation to DMPC bilayers; e) differential scanning calorimetry (DSC) data showed that ibuprofen was able to alter the cooperativity of DMPC phase transition in a concentration-dependent manner, to destabilize the gel phase and that ibuprofen did not significantly perturb the organization of the lipid hydrocarbon chains. Additionally, the effect on the viability of both human promyelocytic leukemia HL-60 and human cervical carcinoma HeLa cells was studied.