In vitro and in vivo stability of polymerized mixed liposomes composed of 2,4‐octadecadienoyl groups of phospholipids

The in vitro stability, under freeze–thawing procedures, and in vivo degradation, in rat spleen, of two types of polymerized liposomes were examined: 1,2‐bis‐[2E, ­4E) ‐ octadecadienoyl] ‐ sn ‐ glycero ‐ 3 ‐ phosphocholine (DODPC) and 1‐acyl‐2‐[(2E, 4E)‐octadecadienoyl]‐sn‐glycero‐3‐phosphocholine (AODPC) were used as polymerizable phospholipids. The lipid composition of the liposomes was prepared as DODPC/Chol/SA (Chol = cholesterol, SA = stearicacid), AODPC/Chol/SA (7/7/2 by molar ratio), AODPC/DPPC/Chol/SA (3.5/3.5/7/2 by molar ratio). The liposomes were extruded through a 0.2 µm polycarbonate‐ filter to obtain the approximate particle size of 0.2 µm, and then irradiated with γ‐rays. Hemoglobin‐encapsulated liposomes were also prepared in the same manner with concentrated hemoglobin (Hb) solution. The DODPC/Chol/SA liposome exhibited no trace of particle size change nor Hb leakage. Although not as excellent as the former, the AODPC‐base liposome showed slightly diameter change (below 7.5%) with a substantial abatement of Hb leakage (<3.5%). Transmission electron microscopy observation of spleens also revealed more efficient degradability with AODPC/DPPC/Chol/SA liposome than with DODPC/Chol/SA liposome. Hb‐encapsulated AODPC/DPPC/Chol/SA liposome, after five freeze–thawing cycles, attained an Hb leakage below 3.5% with a particle size change of 0.7–7.5%, and reduced the spleen retention compared with the DODPC‐base liposome. These results suggest that AODPC/DPPC/Chol/SA liposome can be used as a long‐term preservable blood substitute. Copyright © 2000 John Wiley & Sons, Ltd.     

Effect of the Phospholipid Chain Length and Head Group on Beta‐Phase Formation of Poly(9,9‐dioctylfluorene) Enclosed in Liposomes

We have studied the effect of head group and alkyl chain length on β‐phase formation in poly(9,9‐dioctylfluorene) (PFO) solubilized in phospholipid liposomes. Systems studied have three different alkyl chain lengths (1,2‐dimyristoyl‐sn‐glycero‐3‐phosphatidylcholine [DMPC], 1,2‐didodecanoyl‐sn‐glycero‐3‐phosphatidylcholine [DLPC], 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphatidylcholine [DPPC]) and head groups (1,2‐dimyristoyl‐sn‐glycero‐3‐phosphate monosodium salt [DMPA], 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphoethanolamine [DMPE] and 1,2‐dimyristoyl‐sn‐glycero‐3‐phospho‐l ‐serine sodium salt [DMPS]). Changes in liposome size upon addition of PFO are followed by dynamic light scattering. All the phospholipids induce the formation of PFO β‐phase, which is followed by the emission intensity and deconvolution of the absorption spectra. Both the head group and alkyl chain length affect the yield of β‐phase. The photophysics of PFO incorporated in liposomes is characterized by stationary and time‐resolved fluorescence, whereas the polymer‐phospholipid interactions have been studied by the effect of the PFO concentration on the phospholipid phase transitions (differential scanning calorimetry [DSC]).     

Controlled Release of a Sparingly Water‐Soluble Anticancer Drug through pH‐Responsive Functionalized Gold‐Nanoparticle‐Decorated Liposomes

The binding and detachment of carboxyl‐modified gold nanoparticles from liposomes is used for controlled drug delivery. This study reveals that the binding and detachment of nanoparticles from liposomes depends on the degree of hydration of the liposomes. Liposomes with a lower hydration level undergo stronger electrostatic interactions with negatively charged gold nanoparticles, thus leading to a slower detachment of the carboxyl‐modified gold nanoparticles under gastric conditions. Therefore, under gastric conditions, gold‐nanoparticle‐decorated dipalmitoylphosphatidylcholine (DPPC) liposomes exhibit an at least ten‐times‐slower drug release compared to gold‐nanoparticle‐decorated 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC) liposomes, although both liposomes in the bare state fail to pursue controlled release. Our study also reveals that one can modulate the drug‐release rate by simply varying the concentration of nanoparticles. This study highlights a novel strategy for the controlled release of drug molecules from liposomes.     

Clickable functionalization of liposomes with the gH625 peptide from Herpes simplex virus type I for intracellular drug delivery

Liposomes externally modified with the nineteen residues gH625 peptide, previously identified as a membrane‐perturbing domain in the gH glycoprotein of Herpes simplex virus type I, have been prepared in order to improve the intracellular uptake of an encapsulated drug. An easy and versatile synthetic strategy, based on click chemistry, has been used to bind, in a controlled way, several copies of the hydrophobic gH625 peptide on the external surface of 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPG)‐based liposomes. Electron paramagnetic resonance studies, on liposomes derivatized with gH625 peptides, which are modified with the 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐4‐amino‐4‐carboxylic acid (TOAC) spin label in several peptide positions, confirm the positioning of the coupled peptides on the liposome external surface, whereas dynamic light scattering measurements indicate an increase of the diameter of the liposomes of approximately 30 % after peptide introduction. Liposomes have been loaded with the cytotoxic drug doxorubicin and their ability to penetrate inside cells has been evaluated by confocal microscopy experiments. Results suggest that liposomes functionalized with gH625 may act as promising intracellular targeting carriers for efficient delivery of drugs, such as chemotherapeutic agents, into tumor cells.     

A Micromechanical Cantilever‐Based Liposome Biosensor for Characterization of Protein‐Membrane Interaction

We have newly evaluated the interaction of lipid membrane with two different proteins of lysozyme and carbonic anhydrase from bovine (CAB) using a micro cantilever‐based liposome biosensor with a new droplet‐sealing structure. Herein 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC) liposomes are used as model lipid membrane and are immobilized on the surface of cantilever. The interaction of DPPC liposome with the target protein causes deflection of the micro‐cantilever, which can stably be detected by measuring the resistance change of the strain gauge. The resistance change dependent on time is used to evaluate the characteristic of liposome‐protein interaction. The resistance of the cantilever‐based biosensor increases monotonously with time in both of the two protein solutions. Especially, chronological resistance change depends markedly on both the concentration and species of target proteins. Finally, these results lead us to conclude that the cantilever‐based liposome biosensor with the droplet‐sealing structure facilitates the characterization of protein‐membrane interaction. It also means that this biosensor is a promising candidate device for label‐free detection of concentration and species of different target proteins.     

Determination of liposome–buffer distribution coefficients of charged drugs by capillary electrophoresis frontal analysis

The potential of using CE frontal analysis (CE‐FA) to study the interactions between a range of charged low molecular weight drug substances and liposomes was evaluated. The liposomes used were net negatively charged and consisted of 2‐oleoyl‐1‐palmitoyl‐sn‐glycero‐3‐phosphocholine and 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphate monosodium salt in a ratio of 80/20 mol%. Apparent distribution coefficients (D_mem), defined as the molar concentration of drug substance in the membrane phase divided by the molar concentration of drug substance in the aqueous phase, were successfully determined for six positively and eight negatively charged drug substances with log D_mem ranging from 1.35 to 3.63. The extent of liposome–buffer distribution was found to be dependent on the drug concentration. The results obtained with the developed CE‐FA method were in good agreement with results obtained by equilibrium dialysis. Furthermore, the CE‐FA method was faster, less labor intensive and required smaller sample volumes (～50 μL) compared with equilibrium dialysis. Thus, CE‐FA is an efficient and useful tool for the characterization of interactions between liposomes and low molecular weight drug substances.     

Photoswitchable and Water‐Soluble Fluorescent Nano‐Aggregates Based on a Diarylethene–Dansyl Dyad and Liposome

In this work, a unique approach is developed to generate photoswitchable and water‐soluble fluorescent nano‐aggregates. Initially, a new light‐controlled diarylethene–dansyl dyad DAE 1 is formed by linking two dansyl fluorophores covalently to a symmetrical dithienylethene backbone, whose photophysical properties can be reversibly switched by optical stimuli. Subsequently, the water insolubility of the molecular switch 1 is overcome by incorporating it into the bilayer of liposome DPPC (1,2‐dihexadecanoyl‐sn ‐glycero‐3‐phosphocholine) in water. This strategy creates stable fluorescent nano‐aggregates OF‐1@DPPC (≈25 nm diameter) that are soluble in an aqueous medium. The nano‐aggregates OF‐1@DPPC retain and even improve the photoswitchable fluorescence properties of DAE 1 . More importantly, OF‐1@DPPC exhibits a remarkable photostability and fatigue resistance after 5 cycles of irradiation with UV and visible light, which is crucial for its practical application.     

Effect of curcumin on liposome: curcumin as a molecular probe for monitoring interaction of ionic liquids with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposome

Recent increase and wider use of ionic liquids (ILs) for various applications has drawn attention to their toxicological consequence on human health. The present study explores effects of three different kinds of widely used ILs, such as 1‐methyl‐3‐octylimidazolium chloride, 1‐buytl‐3‐methyl imadazolium tetrafluoroborate and 1‐benzyl‐3‐methyl imidazolium tetrafluoroborate, on liposome properties of 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC) by applying curcumin as molecular probe. Fluorescence intensity of curcumin is reported as a novel rotor which is sensitive to viscosity and thus the fluidity of the solvent. It follows a linear relationship of log fluorescence vs viscosity as proposed by Förster–Hoffmann equation. Curcumin binds strongly to liposome. At low concentration, the lipophilic drug curcumin does not appreciably influence the phase transition temperature of DPPC but as concentration reaches high levels significantly depresses the phase transition temperature. ILs diminish membrane fluidity. 1‐methyl‐3‐octylimidazolium chloride disorders membrane properties by lowering the phase transition as is observed for higher concentration of curcumin, but 1‐buytl‐3‐methyl imidazolium tetrafluoroborate and 1‐benzyl‐3‐methyl imidazolium tetrafluoroborate do not modify phase transition temperature perceptibly; rather they broaden the phase transition at low molar concentration ratio. The three different kinds of ILs under study behave similarly at a high IL:DPPC ratio (1:2), while they behave differently at lower ratios (1:10–1:5).     

Design of liposomes containing photopolymerizable phospholipids for triggered release of contents

We describe a novel class of light-triggerable liposomes prepared from a photo-polymerizable phospholipid DC_8,9PC (1,2-bis (tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine) and DPPC (1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine). Exposure to UV (254 nm) radiation for 0–45 min at 25 °C resulted in photo-polymerization of DC_8,9PC in these liposomes and the release of an encapsulated fluorescent dye (calcein). Kinetics and extents of calcein release correlated with mol% of DC_8,9PC in the liposomes. Photopolymerization and calcein release occurred only from DPPC/DC_8,9PC but not from Egg PC/DC_8,9PC liposomes. Our data indicate that phase separation and packing of polymerizable lipids in the liposome bilayer are major determinants of photo-activation and triggered contents release.     

A Cantilever‐based Biosensor for Real‐time Monitoring of Interactions between Amyloid‐β(1–40) and Membranes Comprised of Phosphatidylcholine Lipids with Different Hydrophobic Acyl Chains

Accumulating evidence suggests that interaction between amyloid‐β (Aβ) and cell membrane is crucial to the pathogenesis of Alzheimer's disease (AD), and thus an increasing understanding of the impact of membrane composition on Aβ‐membrane interaction becomes essential for the mechanism elucidation of Aβ‐membrane interaction and the early diagnosis of AD. In this work, electrically neutral phosphatidylcholine (PC) as the most major class of membrane phospholipids, including 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC), 1,2‐distearoyl‐sn‐glycero‐3‐phosphocholine (DSPC), 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (POPC), and Aβ(1–40) as the most common amyloid protein were selected as the research subjects, and a developed cantilever‐based biosensor, on which liposomes comprised of PC lipids were immobilized, was applied to characterize in real time the interactions between Aβ(1–40) and membranes comprised of PC lipids with different hydrophobic acyl chains, and to evaluate the effect of cholesterol incorporated in membrane on Aβ‐membrane interaction during the whole process of Aβ(1–40) fibrillization. The results illustrate that the interaction between Aβ(1–40) and PC membrane can be divided into three stages, which are related to the change in molecular states of Aβ. More importantly, it is found that membranes comprised of PC lipids with shorter saturated acyl chains show higher interaction ability with Aβ(1–40), and the incorporation of cholesterol into PC bilayer can remarkably accelerate and strengthen Aβ(1–40)‐membrane interaction. These results confirm that hydrophobicity is the main driving force for the interactions between Aβ(1–40) and PC membranes. In return, the above results enlightened us to apply the current micro‐cantilever immobilized with cholesterol‐containing DPPC liposomes to challenge the detection of low‐concentration Aβ(1–40). This time 50‐nM Aβ(1–40) in aqueous solution has been effectively detected, suggesting that this proposed detection technique would contribute to Aβ detection and early diagnosis of AD in the future.     

Serum metabolomics of laryngeal cancer based on liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry

The discovery of new laryngeal cancer‐related metabolite biomarkers could help to facilitate early diagnosis. A serum metabolomics study from laryngeal cancer patients and healthy individuals was conducted using liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry. Univariate and multivariate statistics were used to discriminate laryngeal cancer patients and healthy individuals. 1‐Palmitoyl‐sn‐glycero‐3‐phosphocholine (LysoPC 16:0), 1‐o‐hexadecyl‐2‐acetyl‐sn‐glycero‐3‐phosphocholine (PAF) and 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine were found to be significantly different between the laryngeal cancer group and the healthy group. They are mainly involved in phospholipids catabolism, linoleic acid metabolism, α‐linoleic acid metabolism and arachidonic acid metabolism. The area under the curve of the biomarker combined by two metabolites (LysoPC 16:0 and PAF) was 0.935, the sensitivity was 0.962 and the specificity was 0.825. LysoPC 16:0 and PAF may show diagnostic potential for laryngeal carcinoma.     

Study on capillaries covalently bound with phospholipid vesicles for open‐tubular CEC and application to on‐line open‐tubular CEC‐MS

Phospholipid vesicles were covalently attached to iminoaldehyde‐coated fused silica capillaries and applied to the separation of model steroids by open‐tubular CEC (OT‐CEC). The effects of reducing the formed Schiff's base with sodium borohydride and of the liposome composition on the stability of the coating were investigated. In addition, the studies were focused on the optimization of running conditions (pH values and composition of BGE solution) when CEC, using capillaries covalently bound with liposome dispersions, was coupled to MS. The effect of cholesterol in the liposome dispersion on the binding of model analytes was studied, using liposome dispersions comprising 80:20 mol% zwitterionic 1‐palmitoyl‐2‐oleyl‐sn‐glycero‐3‐phosphocholine (POPC) and the negatively charged phospholipid 1 ‐ palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phospho‐l ‐serine (POPS) and 40:40:20 mol% POPC/POPS/cholesterol. Cholesterol in liposomes (greatly) enhanced the stability of the capillaries by making the coatings more rigid, resulting in lower retention factors for all the studied model steroids. Although most of the studies were carried out by open tubular CEC‐UV Vis, the applicability of the capillaries to on‐line CEC‐MS was demonstrated as well. On‐line CEC‐MS studies on model steroids proved the suitability of coated capillaries for analyte–lipid membrane interaction studies, and especially for such analytes that are difficult to detect by conventional on‐line UV Vis.     

Interaction of Dipalmitoyl Phosphatidylcholine with n‐Hexadecanol in Monolayer and Liposome

The monolayer collapse behavior of n‐hexadecanol/dipalmitoyl phosphatidylcholine (DPPC) was investigated in this study at the air/water interface at 37 °C. Surface pressure variations with time for the mixed monolayers of DPPC with 20 mol% and 50 mol% n‐hexadecanol at corresponding collapse points were recorded by a Langmuir trough system. In addition, the interaction of n‐hexadecanol with a pure DPPC monolayer was identified by fluorescence microscopy (FM). The results demonstrated distinct differences between these systems; according to our observation, the higher the ratio of n‐hexadecanol to DPPC, the more nucleation domains can be induced. The FM images demonstrated that pronounced domain formation was associated with a longer relaxation time of the collapsed DPPC and DPPC/n‐hexadecanol monolayers, and the presence of n‐hexadecanol appeared to enhance the relaxation processes. The liposome was prepared by the thin‐film hydration method. The average diameter of DPPC and DPPC/n‐hexadecanol liposomes was investigated by dynamic light scattering. It is shown that the diameter of DPPC liposome with n‐hexadecanol is smaller than pure DPPC liposome at the initial state. After 24 hours, DPPC/n‐hexadecanol liposome became larger than pure DPPC liposome and lasted for the next four days. The effects of a greater ratio of n‐hexadecanol did not play an important role in DPPC liposome formation based on our dynamic light scattering analysis. Our result demonstrated that n‐hexadecanol might affect the DPPC liposome stability. The increased ratio of n‐hexadecanol in DPPC liposomes could only a play a minor role in DPPC liposome fusion.     

Stable preservation of hemoglobin vesicles as a blood substitute

Long‐term preservation of hemoglobin (Hb) vesicles, the so‐called artificial red cell (ARC), in dry powder was studied. Carbonylhemoglobin (COHb) was encapsulated in the vesicle of 1,2‐bis(2,4‐octadecadienoyl)‐sn‐glycero‐3‐phosphocholine (DODPC) and the polymerizable membrane components were polymerized by γ‐ray irradiation. The obtained ARC suspension was then freeze‐dried in the presence of sucrose. The factors influencing the shelf‐life of the freeze‐dried ARC, such as sucrose concentration, moisture and storage temperature, were elucidated. After storage in the dry state for more than one year, the oxygen‐carrying capacity was recovered by rehydration of the freeze‐dried ARC with distilled water and substitution of the carbon monoxide ligand with oxygen. Copyright © 1999 John Wiley & Sons, Ltd.     

Sequential Synthesis of Coordination Polymersomes

Novel organic–inorganic hybrid liposomes, so‐called coordination polymersomes (CPsomes), with artificial domains that exhibit strong lateral cohesion were prepared by a three‐step procedure that formed a coordinative interaction leading to a lipid bilayer. First, the lipophilic complex (dabco‐C₁₈)[Mn(N)(CN)₄(dabco‐C₁₈)] ( 1 ; dabco‐C₁₈⁺=1,4‐diazabicyclo[2,2,2]octane‐(CH₂)₁₇? CH₃ cation), was synthesized. 1 has a lipophilic alkyl tail part and a tetracyanometallate head group, which can be used for an expansion to two‐dimensional coordination networks. Second, 1 and 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine were mixed to prepare the liposomes. Finally, CPsomes were obtained by the addition of transition‐metal ions ( M ) to form unilamellar faceted liposomes with plain CP raft domains with Mn? CN? M linkages. The concentration of 1 influences the size of the CP raft domains and the shape of the CPsomes. The synthesis of coordination polymers in lipid bilayers is a novel approach for the construction of artificial architectures as raft domains, for example, in cell membranes.     

Enhancement of immune response and protection in BALB/c mice immunized with liposomal recombinant major surface glycoprotein of Leishmania (rgp63): The role of bilayer composition

Development of new generation vaccines requires adjuvants to elicit the type and intensity of immune response needed for protection. Liposomes have been shown to be an effective adjuvant formulation. In this study, the role of liposome bilayer composition with different phase transition temperature (T_c) to induce a T helper 1 (Th1) type of immune response and protection against leishmaniasis in BALB/c mice was assessed. Liposome formulations with different bilayer compositions consisting of egg phosphatidylcholine (EPC, T_c < 0 °C), dipalmitoylphosphatidylcholine (DPPC, T_c 41 °C), or distearoylphosphatidylcholine (DSPC, T_c 54 °C) were prepared. All liposomes were contained rgp63 as a recombinant antigen and used to immunize mice subcutaneously 3 times in 3-week intervals. Evaluation of lesion development and splenic parasite burden after challenge with L. major, evaluation of Th1 cytokine (IFN-γ) and Th2 cytokine (IL-4), and titration of IgG isotypes were carried out to assess the type of generated immune response and extent of protection. The results indicated the generated immune response in mice was influenced by the bilayer composition of liposomes, so that mice immunized with liposomes consisting of EPC induced a Th2 type of immune response while liposome consisting of DPPC or DSPC induced Th1 type of immune response. It seems that liposomes prepared with higher Tm phospholipids are suitable formulation to induce Th1 type of immune response and protection, and so might be used for further investigations to develop an effective vaccine against leishmaniasis.     

Ghrelin–liposome interactions: Characterization of liposomal formulations of an acylated 28‐amino acid peptide using CE

Ghrelin is a pharmacologically interesting peptide hormone due to its effects on appetite and metabolism. The cationic, octanoylated 28 amino acid peptide has a short biological half‐life; thus, prolonged release formulations are of interest. Acylated peptides have been suggested to bind to or be incorporated into liposomes. Formulations based on neutral dipalmitoylphosphatidylcholine (DPPC) liposomes and phosphatidylcholine:cholesterol (70:30 mol%) liposomes, and negatively charged dipalmitoylphosphatidylcholine:dipalmitoylphosphatidylserine (DPPC:DPPS) (70:30 mol%) liposomes (2 mM total lipid concentration) were characterized using ACE. Pre‐equilibrium CZE and frontal analysis CE methods circumventing capillary wall adsorption of the peptide and the liposomes and suitable for characterizing ghrelin–liposome interactions were developed. The cationic peptide exhibited low affinity (<10% bound) for DPPC and phosphatidylcholine:cholesterol (70:30 mol%) liposomes whereas electrostatic interactions caused a higher affinity for DPPC:DPPS (70:30 mol%) liposomes. Studies on desacyl ghrelin instead of ghrelin demonstrated the significance of the n‐octanoyl side chain as an affinity providing moiety towards DPPC:DPPS liposomes (48 and 73% bound peptide, respectively). CE experiments showed that the binding was characterized by rapid dissociation kinetics.     

Combination of COSMOmic and molecular dynamics simulations for the calculation of membrane–water partition coefficients

The importance of membrane‐water partition coefficients led to the recent extension of the conductor‐like screening model for realistic solvation (COSMO‐RS) to micelles and biomembranes termed COSMOmic. Compared to COSMO‐RS, this new approach needs structural information to account for the anisotropy of colloidal systems. This information can be obtained from molecular dynamics (MD) simulations. In this work, we show that this combination of molecular methods can efficiently be used to predict partition coefficients with good agreement to experimental data and enables screening studies. However, there is a discrepancy between the amount of data generated by MD simulations and the structural information needed for COSMOmic. Therefore, a new scheme is presented to extract data from MD trajectories for COSMOmic calculations. In particular, we show how to calculate the system structure from MD, the influence of lipid conformers, the relation to the COSMOmic layer size, and the water/lipid ratio impact. For a 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (DMPC) bilayer, 66 partition coefficients for various solutes were calculated. Further, 52 partition coefficients for a 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine (POPC) bilayer system were calculated. All these calculations were compared to experimental data. © 2013 Wiley Periodicals, Inc.     

Dioctylamine‐Sulfonamide‐Modified Carbon Nanoparticles as High Surface Area Substrates for Coenzyme Q10?Lipid Electrochemistry

Dioctylaminesulfonamide‐modified carbon nanoparticles are characterised and employed as high surface area substrate for (i) coenzyme Q10 and (ii) 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (or DMPC) ‐ Q10 redox processes. The carbon nanoparticles provide a highly hydrophobic substrate with ca. 25 Fg^?1 capacitance when bare. Q10 or DMPC‐Q10 immobilised onto the carbon nanoparticles lower the capacitance, but give rise to well‐defined pH‐dependent voltammetric responses. The DMPC‐Q10 deposit shows similar characteristics to those of Q10, but with better reproducibility and higher sensitivity. Both redox systems, Q10 and DMPC‐Q10, are sensitive to the Na⁺ concentration in the electrolyte and mechanistic implications are discussed.