Effects of surfactants on the spectral behaviour of calcein (II): a method of evaluation

Assessment of asphaltene and resin fractions in crude oil using laser-induced fluorescence spectroscopy based on modified Beer-Lambert (LIFS-MBL)

Crude oil is one of the most significant petrogenic sources of polycyclic aromatic compounds (PACs). These substances play an essential role in the pollution of the marine environment. Therefore, the rapid identification of this pollutant source and its fractions is vital. For this purpose, a fast and on-site method of laser-induced fluorescence spectroscopy based on modified Beer-Lambert (LIFS-MBL) is proposed here using solvent densitometry. Three optical parameters of the self-quenching (K), the extinction (α), and the peak concentration (Cp) are experimentally extracted from MBL graphs. Note that the parameters above are known to be unique characteristics of various crude oils. The corresponding compounds are generally classified into saturate, aromatic, resin, and asphaltene fractions, abbreviated as SARA. Differentiation among these fractions is achieved using the LIFS-MBL method by selecting the optimal excitation wavelength at 405 nm. This line effectively rules out the light aromatic rings and focuses on heavy fractions. The correlation of optical parameters with heavy oil fractions is verified according to analysis of variance. Statistical relations are proposed to calculate crude oil fractions values. The values of light fractions including saturate and aromatic components can also be determined by the heavy fractions. In this method, the test time is notably reduced from four days using the standard methods to less than half an hour according to the presented LIFS-MBL technique.

Accelerated Recombination of Lophyl Radicals in Micelles: Rapid Controlled Self-Assembly of Micelles Formed by Amphiphilic Lophine Dimers and Release of Solubilized Substance by Photoirradiation

Controlling the morphology of molecular assemblies formed by surfactants by photoirradiation enables the controlled release of incorporated substances, which can be applied to delivery systems for drugs and active ingredients. On the other hand, conventional photoresponsive surfactants and molecular assemblies have a slow response speed, making it difficult to control their functions at the desired time. In this review, I discuss our recent progress in the accelerated control of functions of photoresponsive molecular assemblies by using lophine dimer as a photochromic compound. The lophine dimer derivative dissociates into a pair of lophyl radicals that upon ultraviolet (UV) light irradiation, and these radical species thermally recombine although the recombination reaction is extremely slow due to the diffusion of lophyl radicals. By using the confined inner space of micelles formed by surfactants, the recombination reaction was extremely accelerated. With UV light irradiation, rapid morphological changes in micelles, formed by amphiphilic lophine dimers were observed by using in situ small-angle neutron scattering (in situ SANS) system. Moreover, the rapid controlled release of calcein as a model drug was achieved by UV light irradiation using the photoresponsive micelles. This rapid system can realize the controlled release of drugs truly at the desired time, developing an efficient and precise drug delivery system (DDS). Furthermore, it can be applied in a wide range of fields such as release control of active ingredients, efficient heat exchange control, and actuating systems.

Laser-induced fluorescence spectroscopy of plant-based drugs: Opium and hashish provoking at 405 nm

Here, the fluorescence properties of some plant-based drug samples are characterized using a coherent excitation source at 405 nm. The laser-induced fluorescence (LIF) spectroscopy is examined to analyze opium and hashish. In order to improve traditional fluorescence methods for better analysis of optically dense materials, we have proposed five characteristic parameters based on solvent densitometry assay as the fingerprints of drugs of interest. The signal emissions are recorded in terms of various drug concentrations, such that the best fitting over experimental data determines the fluorescence extinction (α) and self-quenching (k) coefficients according to the modified Beer-Lambert formalism. The typical α value is determined to be 0.30 and 0.15 mL/(cm∙mg) for opium and hashish, respectively. Similarly, typical k is obtained 0.390 and 1.25 mL/(cm∙mg), respectively. Furthermore, the concentration at max fluorescence intensity (Cp) is determined for opium and hashish to be 1.8 and 1.3 mg/mL, respectively. Results reveal that opium and hashish benefit their own characteristic fluorescence parameters to discriminate those illicit substances promptly using the present method.

Detergent-free Ultrafast Reconstitution of Membrane Proteins into Lipid Bilayers Using Fusogenic Complementary-charged Proteoliposomes

Detergents are indispensable for delivery of membrane proteins into 30-100 nm small unilamellar vesicles, while more complex, larger model lipid bilayers are less compatible with detergents. Here we describe a strategy for bypassing this fundamental limitation using fusogenic oppositely charged liposomes bearing a membrane protein of interest. Fusion between such vesicles occurs within 5 min in a low ionic strength buffer. Positively charged fusogenic liposomes can be used as simple shuttle vectors for detergent-free delivery of membrane proteins into biomimetic target lipid bilayers, which are negatively charged. We also show how to reconstitute membrane proteins into fusogenic proteoliposomes with a fast 30-min protocol. Combining these two approaches, we demonstrate a fast assembly of an electron transport chain consisting of two membrane proteins from E. coli, a primary proton pump bo3-oxidase and F1Fo ATP synthase, in membranes of vesicles of various sizes, ranging from 0.1 to >10 microns, as well as ATP production by this chain.

Fluorescence lifetime-based sensing of polymersome leakage

Assays to analyze the degradation, lysis and leakage of vesicles are commonly utilized in biology and physical chemistry. Here we show the fluorescence lifetime-based sensing of the leakage of stimuli responsive PEG₁₁₄-b-PLA₁₆₇ block copolymer vesicles. The time-resolved technique differentiates between the fluorophore molecules in the solvated state at high concentrations, and in the wall material and in the solvated state at low concentrations. The vesicle leakage occurs after an incubation period, which was detected by the change of the time correlated single photon counting decays.

Change of Multiple-Layered Phospholipid Vesicles Produced by Electrostatic Deposition of Polymers during Storage

In this study, 1 wt% lecithin (–), chitosan (+), and λ-carrageenan (–) were prepared to manufacture multiple-layered liposomes with optimal formulations developed in a previous study by using layer-by-layer electrostatic deposition. We observed their particle size, ζ-potential, sedimentation behavior, and microstructure for 6 weeks. Multiple-layered liposomes were quenched with calcein to evaluate stability in terms of factors such as encapsulation efficiency and released amount of calcein. The particle size of multi-layered liposomes increased with storage periods and the ζ-potential of multiple-layered liposomes gained a neutral charge. Interestingly, negatively charged layered liposomes were smaller than positively charged layered liposomes and showed a lower polydispersity index. Moreover, the ζ-potential did not apparently change compared to positively charged layered liposomes. For the calcein release study, multiple-layered liposomes significantly sustained quenched calcein more than that observed using non-layered liposomes. This study showed that it was possible to increase the thickness of the liposome surface and to manipulate its charge using chitosan and λ-carrageenan through electrostatic deposition. Results showed that manufacturing negatively charged multiple-layer (over 4-layer) liposomes with charged biopolymer improved the physicochemical stability of liposomes.

Fluorescence properties of several chemotherapy drugs: doxorubicin, paclitaxel and bleomycin

Several chemo-drugs act as the biocompatible fluorophores. Here, the laser induced fluorescence (LIF) properties of doxorubicin, paclitaxel and bleomycin are investigated. The absorption lines mostly lie over UV range according to the UV-VIS spectra. Therefore, a single XeCl laser provokes the desired transitions of the chemo-drugs of interest at 308 nm. It is shown that LIF spectra are strongly dependent on the fluorophore concentration giving rise to the sensible red shift. This happens when large overlapping area appears between absorption and emission spectra accordingly. The red shift is taken into account as a characteristic parameter of a certain chemo-drug. The fluorescence extinction (α) and self-quenching (k) coefficients are determined based on the best fitting of the adopted Lambert-Beer equation over experimental data. The quantum yield of each chemo-drug is also measured using the linearity of the absorption and emission rates.

Interaction between a cationic bolaamphiphile and DNA: The route towards nanovectors for oligonucleotide antimicrobials

Bacterial resistance to antimicrobials is a global threat that requires development of innovative therapeutics that circumvent its onset. The use of Transcription Factor Decoys (TFDs), DNA fragments that act by blocking essential transcription factors in microbes, represents a very promising approach. TFDs require appropriate carriers to protect them from degradation in biological fluids and transfect them through the bacterial cell wall into the cytoplasm, their site of action. Here we report on a bolaform cationic surfactant, [12-bis-THA]Cl2, with proven transfection activity in vivo. By studying the physical-chemical properties of its aqueous solutions with light scattering, cryo-TEM, ζ-potential, absorption and fluorescence spectroscopies, we prove that the bolaamphiphiles associate into transient vesicles which convert into one-dimensional elongated structures over time. These surfactant assemblies complex TFDs with extremely high efficiency, if compared to common cationic amphiphiles. At Z+/-=11, the nanoplexes are stable and have a size of 120nm, and they form independently of the original morphology of the [12-bis-THA]Cl2 aggregate. DNA is compacted in the nanoplexes, as shown through CD spectroscopy and fluorescence, but is readily released in its native form if sodium taurocholate is added.

The impact of bubbles on measurement of drug release from echogenic liposomes

Echogenic liposomes (ELIP) encapsulate gas bubbles and drugs within lipid vesicles, but the mechanisms of ultrasound-mediated drug release from ELIP are not well understood. The effect of cavitation activity on drug release from ELIP was investigated in flowing solutions using two fluorescent molecules: a lipophilic drug (rosiglitazone) and a hydrophilic drug substitute (calcein). ELIP samples were exposed to pulsed Doppler ultrasound from a clinical diagnostic ultrasound scanner at pressures above and below the inertial and stable cavitation thresholds. Control samples were exposed to a surfactant, Triton X-100 (positive control), or to flow alone (negative control). Fluorescence techniques were used to detect release. Encapsulated microbubbles reduced the measured fluorescence intensity and this effect should be considered when assessing drug release from ELIP. The origin of this effect is not specific to ELIP. Release of rosiglitazone or calcein compared to the negative control was only observed with detergent treatment, but not with ultrasound exposure, despite the presence of stable and inertial cavitation activity. Release of rosiglitazone or calcein from ELIP exposed to diagnostic ultrasound was not observed, even in the presence of cavitation activity. Ultrasound-mediated drug delivery strategies with ELIP will thus rely on passage of the drug-loaded liposomes to target tissues.

Characterization of fluorinated catansomes: a promising vector in drug-delivery

Catansomes, which are vesicles prepared from mixtures of oppositely charged surfactants, have been suggested as effective alternatives to phospholipid vesicles, i.e., liposomes, in applications such as drug-delivery. This is mainly due to their enhanced chemical and physical stability as well as to their relatively easy preparation, which is an advantage for large-scale productions. In this study we have investigated catansomes prepared from a perfluorinated anionic surfactant (sodium perfluorooctanoate) premixed with a hydrogenated cationic surfactant (dodecyltrimethylammonium bromide or 1-dodecylpyridinium chloride). The aim was to gain insights into the physicochemical properties of these systems, such as size, stability, surface charge, and membrane morphology, which are essential for their use in drug-delivery applications. The catansomes were mostly unilamellar and 100-200 nm in size, and were stable for more than five months at room temperature. After loading the catansomes with the fluorescent marker calcein, they were found to exhibit an appreciable encapsulation efficiency and a low calcein leakage over time. The addition of fatty acids to calcein-loaded catansomes considerably promoted the release of calcein, and the rate and efficiency of calcein release were found to be proportional to the fatty acid concentration and chain length. Our results prove the feasibility of utilizing catansomes as drug-delivery vehicles as well as provide a means to efficiently release the encapsulated load.

Solubility, spectroscopic properties and photostability of Rhein/cyclodextrin inclusion complex

The host-guest interaction between Rhein (Rh)--an anthraquinonic drug characterized by low water solubility and recently considered for its potential antidiabetic and antitumoral activities other than for the well-established anti-inflammatory properties--with cyclodextrins (CDs) was investigated using phase-solubility diagrams. The typical A(L) phase-solubility profiles suggest the formation of the 1:1 inclusion complexes between Rh and the two CDs investigated, namely beta-cyclodextrin and 2-hydroxypropyl-beta-cyclodextrin and the resulting constant values of complex formation, K(c), were estimated. Due to the higher K(c) value, complex of Rhein with 2-hydroxypropyl-beta-cyclodextrin was chosen for further investigation. Characterization in solution of 2-hydroxypropyl-beta-cyclodextrin/Rhein complex was achieved both by fluorescence and visible spectroscopic techniques. These results confirm the formation of inclusion complexes in solution and the 1:1 stoichiometry of the binary system. With respect to Rhein aqueous solution behavior, the inclusion complex appears to be able: (i) to enhance Rhein solubility; (ii) to control its neutral/anionic equilibrium; (iii) to affect both its electronic absorption and fluorescence spectra. Finally, the photostability of Rhein in the presence of cyclodextrins was evaluated.

Redox-triggered contents release from liposomes

An exciting new direction in responsive liposome research is endogenous triggering of liposomal payload release by overexpressed enzyme activity in affected tissues and offers the unique possibility of active and site-specific release. Bringing to fruition the fully expected capabilities of this new class of triggered liposomal delivery system requires a collection of liposome systems that respond to different upregulated enzymes; however, a relatively small number currently exist. Here we show that stable, approximately 100 nm diameter liposomes can be made from previously unreported quinone-dioleoyl phosphatidylethanolamine (Q-DOPE) lipids, and complete payload release (quenched fluorescent dye) from Q-DOPE liposomes occurs upon their redox activation when the quinone headgroup possesses specific substituents. The key component of the triggerable, contents-releasing Q-DOPE liposomes is a "trimethyl-locked" quinone redox switch attached to the N-terminus of DOPE lipids that undergoes a cleavage event upon two-electron reduction. Payload release by aggregation and leakage of "uncapped" Q-DOPE liposomes is supported by results from liposomes wherein deliberate alteration of the "trimethyl-locked" switch completely deactivates the redox-destructible phenomena (liposome opening). We expect that Q-DOPE liposomes and their variants will be important in treatment of diseases with associated tissues that overexpress quinone reductases, such as cancers and inflammatory diseases, because the quinone redox switch is a known substrate for this group of reductases.

Kinetic models for peptide-induced leakage from vesicles and cells

In this article analytical expressions for peptide-induced membrane leakage are presented. Two different models for time-dependent leakage have been developed. In the first, the leakage is assumed to be coupled by pores formed by the peptides. In the second model the peptide is assumed to induce a stress/perturbation in the membrane, and in order to reduce the stress, rearrangements in the membrane are induced. The leakage is coupled to these rearrangements, and when equilibrium is achieved no more leakage occurs. From the kinetic models simple fitting routines have been developed involving only two fitting parameters, and these have been used to fit experimental data for two prion protein-derived peptides as well as the honey bee toxin melittin in both vesicles and erythrocytes with good results. The fitted parameters provide both a quantitative and a qualitative basis for interpreting the experimental results. In addition a model for the peptide concentration-dependent leakage is presented, which was used to fit experimental data for leakage induced by the prion protein-derived peptides. The models presented in this article are compared with other models for peptide-induced membrane leakage.

The role of surfactants in the reversal of active transport mediated by multidrug resistance proteins

A variety of seven nonionic, one amphoteric and, one anionic surfactant that are applied or investigated as surfactants in drug formulation, were analyzed for their capacity to modulate carrier-mediated transport by efflux pumps. Two cell lines, murine monocytic leukemia cells overexpressing P-glycoprotein (P-gp) and Madin-Darby canine kidney cells stably overexpresssing human multidrug resistance-associated protein 2 (MRP2), were used as test systems. The modulation of P-gp and of MRP2 function was studied by the reversal of rhodamine 123 and of methylfluorescein-glutathione conjugate transport, respectively. Mechanisms that were not transporter related and could lead to misinterpretations were identified, such as probe quenching, probe encapsulation by micelles, and membrane damage. P-gp-mediated rhodamine 123 transport was inhibited by five nonionic surfactants in a concentration-dependent manner and in the order TPGS > Pluronic PE8100 > Cremophor EL > Pluronic PE6100 approximately Tween 80. In contrast, none of the surfactants showed a significant inhibition of MRP2-mediated efflux in Madin-Darby canine kidney/MRP2 cells. In conclusion, the results indicate that surfactants demonstrate a transporter-specific interaction, rather than unspecific membrane permeabilization. The present analysis offers insight in the possible mechanisms of surfactant interactions with biological membranes and could help to identify specific drug formulations.

Noninvasive fluorescent study in situ and in real time of glucose effects on the pharmacokinetic of calcein

This study was undertaken to compare the effect of glucose injection on the pharmacokinetic behavior of a soluble dye in normal and tumoral tissues. The measurements were done using a noninvasive fluorescent spectroscopy in situ and in real time. The experiments were performed on three groups of animals with calcein as a soluble pH-insensitive fluorescent dye combined or not with glucose. Glucose solution was injected 5 or 30 min before calcein. Fluorescence emission intensity was recorded on normal and tumor tissues with an optical multichannel analyzer. Calcein concentration was also measured in blood using repetitive blood sampling. In the control group (without glucose injection), calcein is rapidly cleared from the blood, with a slow tissue clearance. Fluorescence of normal tissue was higher than fluorescence measured in tumor tissue. When glucose is injected 5 min before calcein, there was a rapid increase of tissue fluorescence followed by a plateau remaining during the whole experiment. No difference between tumor and normal tissue fluorescence intensity was observed. When glucose was injected 30 min before calcein, the plateau phase was reduced to 50 min in normal tissue. Tumor tissue fluorescence displays no distinct plateau phase. These results clearly showed the effect of glucose injection in situ and in real time, by a noninvasive method, on the pharmacokinetic of a soluble dye in a tumor tissue compared to a normal tissue. Differences between blood compartment and tissues kinetic profiles were also clearly demonstrated.

Functional characterization of an endosome-disruptive peptide and its application in cytosolic delivery of immunoliposome-entrapped proteins

Antibody-directed liposomes (immunoliposomes) are frequently used for targeted drug delivery. However, delivery of large biotherapeutic molecules (i.e. peptides, proteins, or nucleic acids) with immunoliposomes is often hampered by an inefficient cytosolic release of entrapped macromolecules after target cell binding and subsequent endocytosis of immunoliposomes. To enhance cytosolic drug delivery from immunoliposomes present inside endosomes, a pH-dependent fusogenic peptide (diINF-7) resembling the NH(2)-terminal domain of influenza virus hemagglutinin HA-2 subunit was used. Functional characterization of this dimeric peptide showed its ability to induce fusion between liposome membranes and leakage of liposome-entrapped compounds when exposed to low pH. In a second series of experiments, diINF-7 peptides were encapsulated in immunoliposomes to enhance the endosomal escape of diphtheria toxin A chain (DTA), which inhibits protein synthesis when delivered into the cytosol of target cells. Immunoliposomes targeted to the internalizing epidermal growth factor receptor on the surface of ovarian carcinoma cells (OVCAR-3) and containing encapsulated DTA did not show any cytotoxicity toward OVCAR-3 cells. Cytotoxicity was only observed when diINF-7 peptides and DTA were co-encapsulated in the immunoliposomes. Thus, diINF-7 peptides entrapped inside liposomes can greatly enhance cytosolic delivery of liposomal macromolecules by pH-dependent destabilization of endosomal membranes after cellular uptake of liposomes.