DPPC Liposomes Research Articles

A Coarse-Grained Molecular Dynamics Perspective on the Release of 5-Fluorouracil from Liposomes.

Liposomes, small bilayer phospholipid-containing vesicles, are frequently used to ensure slow drug release for a prolonged and improved therapeutic effect. Nevertheless, current findings on the membrane affinity and permeability of the anticancer agent 5-fluorouracil (5-FU) are confounding, which leads to a lack of a clear understanding of how lipid composition impacts the distribution of 5-FU within liposomal structures and its delivery. In the current work, we report a comprehensive coarse-grained molecular dynamics (CGMD) investigation on the influence of cholesterol (CHOL) and the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) on the partitioning of 5-FU in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) double-bilayer systems, as well as its in vitro release from liposomes with identical lipid compositions. Our results show that 5-FU tends to accumulate at the water-lipid interface, in the vicinity of polar headgroups, without partitioning in the hydrophobic tail region. At the same time, the presence of CHOL proportionally increases the distribution of this drug in the interbilayer aqueous space, decreasing the drug's affinity toward the membrane polar head region, while DOTAP has only a slight effect on drug distribution. Thus, it is expected that 5-FU will be released slower from CHOL-containing DPPC liposomes but not DOTAP-containing vesicles. However, in vitro release studies showed that the release kinetics of 5-FU from DPPC vesicles is not influenced by the presence of CHOL and that the incorporation of 10 mol % DOTAP leads to the best release profile for 5-FU, highlighting the complexity of nanocarrier drug release kinetics. We hypothesize that the initial rapid release seen in dialysis experiments is not related to drug membrane permeability but rather to 5-FU adsorbed on the outer surface of liposomes.

Anti-cancer and anti-microbial drug encapsulated lipid vesicles as drug delivery systems: Calorimetric and spectroscopic study

Lipid-based drug delivery systems (DDS) have attracted considerable interest for their capacity to achieve controlled drug release and encapsulate a variety of drug molecules—hydrophobic, hydrophilic, and amphiphilic—enabling diverse therapeutic applications. The research focuses on the structural and functional aspects of lipid-based vesicles that encapsulate both anti-cancer and anti-microbial drugs. The study employs ultrasensitive isothermal titration calorimetry and differential scanning calorimetry to gain mechanistic insights into the partitioning of drugs in the lipid-based DDS, release mechanisms, and binding interactions with serum proteins after the release.The structural properties of 5-fluorouracil (5-FU) suggest that the drug can partition into the outer region of the bilayer, where it forms hydrogen bonds with the polar heads of the amphiphilic lipid chains. Kanamycin indicates strong partitioning into liposomes as it displays a binding constant of the order of 106. Erythromycin exhibits limited partitioning into the bilayer, as assessed by fitting ITC data using a sequential two-binding site model. The values of change in enthalpy and entropy reflect the interaction nature and desolvation process during the drug's partitioning into liposomes. Thermodynamic signatures and transition temperatures obtained from ITC and DSC studies indicate that no diffusion-based drug release occurs from DPPC and DSPC-based liposomes. The interaction heat between the released drug and carrier serum albumin protein is very low and shows no consistent pattern. This suggests that the drugs are stably encapsulated in the drug delivery system (DDS), with no significant leakage over time. Insights from such studies on the influence of drug molecule structure on its partitioning into various lipid vesicles and further release of the same drugs from it guide in criteria for developing improvised drug delivery systems.

Aggression to Biomembranes by Hydrophobic Tail Chains under the Stimulus of Reductant.

Stimulus-responsive materials hold significant promise for antitumor applications due to their variable structures and physical properties. In this paper, a series of peptides with a responsive viologen derivative, Pep-CnV (n = 1, 2, 3) were designed and synthesized. The process and mechanism of the interaction were studied and discussed. An ultraviolet-visible (UV) spectrophotometer and fluorescence spectrophotometer were used to study their redox responsiveness. Additionally, their secondary structures were measured by Circular Dichroism (CD) in the presence or absence of the reductant, Na2SO3. DPPC and DPPG liposomes were prepared to mimic normal and tumor cell membranes. The interaction between Pep-CnV and biomembranes was investigated by the measurements of surface tension and cargo leakage. Results proved Pep-CnV was more likely to interact with the DPPG liposome and destroy its biomembrane under the stimulus of the reductant. And the destruction increased with the length of the hydrophobic tail chain. Pep-CnV showed its potential as an intelligent antitumor agent.

Effect of ultrasound exposure time in the size distribution of lecithin liposomes in the nanoscale

Abstract The characteristics of liposome suspensions subjected to ultrasound were studied using the Nanoparticle Trajectory Analysis (NTA) technique. These were prepared with either DPPC or soy lecithin using the thin layer method. For each preparation protocol, the size and ζ potential probability densities were determined by averaging the densities obtained in several measurements. Ultrasound exposure changed the characteristics of the size and ζ potential distributions. For the size distribution, the exposure resulted in an increment of the number of liposomes with diameters in the range of ∼ 100 nm, the corresponding size distributions became slimmer, with mean diameters smaller than the ones without exposure. This is reflected in the reduction of the polydispersity index experienced by the liposome suspensions after sonication. For DPPC liposomes, it changed from ≈ 0.26 without exposure to ≈ 0.19 after 10 min sonication whereas for soy lecithin liposomes it changed from ≈ 0.30 without exposure to ≈ 0.21 after 10 min sonication. For the ζ potential, after 10 min exposure, the distributions became wider, with mean values more negative than the ones without exposure. The mean ζ potential, for DPPC liposomes, changed from ≈ −35 mV without exposure to ≈ −39 mV after 10 min sonication whereas for soy lecithin liposomes it changed from ≈ −38 mV without exposure to ≈ −42 mV after 10 min sonication. Therefore, our results show that exposure to ultrasound reduced the polydispersity and increased the stability of the liposome suspensions.

Calcein release from DPPC liposomes by phospholipase A2 activity: Effect of cholesterol and amphipathic copolymers

In this study, we evaluated the impact of incorporating diblock and triblock amphiphilic copolymers, as well as cholesterol into DPPC liposomes on the release of a model molecule, calcein, mediated by exogenous phospholipase A2 activity. Our findings show that calcein release slows down in the presence of copolymers at low concentration, while at high concentration, the calcein release profile resembles that of the DPPC control. Additionally, calcein release mediated by exogenous PLA2 decreases as the amount of solubilized cholesterol increases, with a maximum between 18 mol% and 20 mol%. At concentrations higher than 24 mol%, no calcein release was observed. Studies conducted on HEK-293 and HeLa cells revealed that DPPC liposomes reduced viability by only 5% and 12%, respectively, after 3 hours of incubation, while DPPC liposome in presence of 33 mol% of Cholesterol reduced viability by approximately 11% and 23%, respectively, during the same incubation period. For formulations containing copolymers at low and high concentrations, cell viability decreased by approximately 20% and 40%, respectively, after 3 hours of incubation. Based on these preliminary results, we can conclude that the presence of amphiphilic copolymers at low concentration can be used in the design of new DPPC liposomes, and together with cholesterol, they can modulate liposome stabilization. The new formulations showed low cytotoxicity in HEK-293 cells, and it was observed that calcein release depended entirely on PLA2 activity and the presence of calcium ions.

Liposome‐Based Delivery of a Bis‐benzimidazole Derivative to Duplex DNA: A Spectroscopic Study

AbstractDue to the immense pharmacological significance, the interaction of small molecules with liposome and the exact knowledge of their binding location and distribution within the lipid bilayer of liposome is an active field of biophysical research. Here, we have studied the binding interaction of H33258 with DPPC liposome, a model biological membrane. From the steady‐state fluorescence spectroscopy it was revealed that H33258 bounded to DPPC liposome and the estimated binding constant value was 2.5×102 M−1. It was also revealed that the H33258 essentially partitioned within the lipid bilayer of DPPC liposome. Moreover, from steady‐state fluorescence, time‐resolved lifetime, time‐resolved anisotropy and ITC studies it was established that the probe molecules were sequestrated from the lipid bilayer and bounded to a duplex DNA structure. Our results on the binding consequences of H33258 with liposome will aid development of a simple and safe strategy to deliver drugs to the target sites using liposome, endogenously.

Elastic Liposomes Containing Calcium/Magnesium Ferrite Nanoparticles Coupled with Gold Nanorods for Application in Photothermal Therapy.

This work reports on the design, development, and characterization of novel magneto-plasmonic elastic liposomes (MPELs) of DPPC:SP80 (85:15) containing Mg0.75Ca0.25Fe2O4 nanoparticles coupled with gold nanorods, for topical application of photothermal therapy (PTT). Both magnetic and plasmonic components were characterized regarding their structural, morphological, magnetic and photothermal properties. The magnetic nanoparticles display a cubic shape and a size (major axis) of 37 ± 3 nm, while the longitudinal and transverse sizes of the nanorods are 46 ± 7 nm and 12 ± 1.6 nm, respectively. A new methodology was employed to couple the magnetic and plasmonic nanostructures, using cysteine as bridge. The potential for photothermia was evaluated for the magnetic nanoparticles, gold nanorods and the coupled magnetic/plasmonic nanoparticles, which demonstrated a maximum temperature variation of 28.9 °C, 33.6 °C and 37.2 °C, respectively, during a 30 min NIR-laser irradiation of 1 mg/mL dispersions. Using fluorescence anisotropy studies, a phase transition temperature (Tm) of 35 °C was estimated for MPELs, which ensures an enhanced fluidity crucial for effective crossing of the skin layers. The photothermal potential of this novel nanostructure corresponds to a specific absorption rate (SAR) of 616.9 W/g and a maximum temperature increase of 33.5 °C. These findings point to the development of thermoelastic nanocarriers with suitable features to act as photothermal hyperthermia agents.

Effect of DMSO on Structural Properties of DMPC and DPPC Liposome Suspensions.

The study and characterization of the biophysical properties of membranes and drug-membrane interactions represent a critical step in drug development, as biological membranes act as a barrier that the drug must overcome to reach its active site. Liposomes are widely used in drug delivery to circumvent the poor aqueous solubility of most drugs, improving systemic bioavailability and pharmacokinetics. Further, they can be targeted to deliver to specific disease sites, thus decreasing drug load, and reducing side effects and poor adherence to treatment. To improve drug solubility during liposome preparation, DMSO is the most widely used solvent. This raises concern about the potential effect of DMSO on membranes and leads us to investigate, using DSC and EPR, the influence of DMSO on the behavior of lipid model membranes of DMPC and DPPC. In addition, we tested the influence of DMSO on drug-membrane interaction, using compounds with different hydrophobicity and varying DMSO content, using the same experimental techniques. Overall, it was found that with up to 10% DMSO, changes in the bilayer fluidity or the thermotropic properties of the studied liposomes were not significant, within the experimental uncertainty. For higher concentrations of DMSO, there is a stabilization of both the gel and the rippled gel phases, and increased bilayer fluidity of DMPC and DPPC liposomes leading to an increase in membrane permeability.

Calreticulin P-domain-derived “Eat-me” peptides for enhancing liposomal uptake in dendritic cells

Discovering new ligands for enhanced drug uptake and delivery has been the core interest of the drug delivery field. This study capitalizes on the natural “eat-me” signal of calreticulin (CRT), proposing a novel strategy for functionalizing liposomes to improve cellular uptake. CRT is presented on the surfaces of apoptotic cells, and it plays a crucial role in immunogenic cell death (ICD). This is because it is essential for antigen uptake via low-density lipoprotein (LDL) receptor-mediated phagocytosis. Inspired by this mechanism, we interrogated CRT’s “eat-me” feature using CRT-derived peptides to functionalize liposomes. We studied liposomal formulation stability, properties, cellular uptake, toxicity, and intracellular trafficking in dendritic cells. We identified key peptide fragments of CRT, specifically from the hydrophilic P-domain, that are compatible with liposomal formulations. Contrary to the more hydrophobic N-domain peptides, the P-domain peptides induced significantly higher liposomal uptake in DC2.4 dendritic cells than cationic DOTAP and anionic DPPG liposomes without inducing toxicity. The P-domain-derived peptides led to enhanced liposomal uptake into DC2.4 dendritic cells compared to the standard DPPC liposomes. The uptake can be partially blocked by the receptor-associated protein (RAP). Upon internalization, P-domain-peptide-decorated liposomes showed higher co-localization with lysosomes compared to the standard DPPC liposomes. Our findings illuminate CRT's operational role and identify P-domain peptides as promising agents for developing biomimetic drug delivery systems that can potentially replicate CRT's “eat-me” function.

Initial Quenching Efficiency Determines Light-Driven H2 Evolution of [Mo3 S13 ]2- in Lipid Bilayers.

Nature uses reactive components embedded in biological membranes to perform light-driven photosynthesis. Here, a model artificial photosynthetic system for light-driven hydrogen (H2 ) evolution is reported. The system is based on liposomes where amphiphilic ruthenium trisbipyridine based photosensitizer (RuC9 ) and the H2 evolution reaction (HER) catalyst [Mo3 S13 ]2- are embedded in biomimetic phospholipid membranes. When DMPC was used as the main lipid of these light-active liposomes, increased catalytic activity (TONCAT ~200) was observed compared to purely aqueous conditions. Although all tested lipid matrixes, including DMPC, DOPG, DPPC and DOPG liposomes provided similar liposomal structures according to TEM analysis, only DMPC yielded high H2 amounts. In situ scanning electrochemical microscopy (SECM) measurements using Pd microsensors revealed an induction period of around 26 minutes prior to H2 evolution, indicating an activation mechanism which might be induced by the fluid-gel phase transition of DMPC at room temperature. Stern-Volmer-type quenching studies revealed that electron transfer dynamics from the excited state photosensitizer are most efficient in the DMPC lipid environment giving insight for design of artificial photosynthetic systems using lipid bilayer membranes.

Effect of phospholipid head group on ultrasound-triggered drug release and cellular uptake of immunoliposomes

Liposomes are the most successful nanoparticles used to date to load and deliver chemotherapeutic agents to cancer cells. They are nano-sized vesicles made up of phospholipids, and targeting moieties can be added to their surfaces for the active targeting of specific tumors. Furthermore, Ultrasound can be used to trigger the release of the loaded drugs by disturbing their phospholipid bilayer structure. In this study, we have prepared pegylated liposomes using four types of phospholipids with similar saturated hydrocarbon tails including a phospholipid with no head group attached to the phosphate head (DPPA) and three other phospholipids with different head groups attached to their phosphate heads (DPPC, DPPE and DPPG). The prepared liposomes were conjugated to the monoclonal antibody trastuzumab (TRA) to target the human epidermal growth factor receptor 2 (HER2) overexpressed on HER2-positive cancer cells (HER2+). We have compared the response of the different formulations of liposomes when triggered with low-frequency ultrasound (LFUS) and their cellular uptake by the cancer cells. The results showed that the different formulations had similar size, polydispersity, and stability. TRA-conjugated DPPC liposomes showed the highest sensitivity to LFUS. On the other hand, incubating the cancer cells with TRA-conjugated DPPA liposomes triggered with LFUS showed the highest uptake of the loaded calcein by the HER2+ cells.

Evaluating pesticide ecotoxicity using a stimuli-response model in liposomes

Pesticides are widely used around the home and in agriculture to control unwanted populations; however, they may also be toxic to non-targeted organisms. Because traditional methods of assessing pesticide toxicity are expensive, lengthy, and ethically questionable, we evaluated pesticide toxicities using stimuli-responses in liposomes. Pesticide ecotoxicity was evaluated using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes. Changes in membrane permeability were measured using calcein leakage assays as stimuli-responses in the presence of six pesticides (Chlorpyrifos-methyl, fluometuron, imidacloprid, pirimicarb, pyrethrin, and quizalofop-ethyl), for which the calcein release rate was analyzed using a first-order kinetics equation. The calcein release rate constants of the DPPC liposomes were used to classify the pesticides into lower and higher toxicity groups. In each group, the initial calcein release rate from the DPPC/DOPC liposomes mixed with 33 ​mol% DOPC correlated well with previously reported pesticide toxicities. The DOPC liposomes underwent lateral phase separation in a different manner between the two toxicity groups. Pesticides with lower toxicities were partitioned in the DPPC-enriched phase, disrupting the gel phase order through their hydrophobicity, whereas pesticides with higher toxicity were partitioned in the DOPC-enriched phase and stabilizing the liquid disordered phase owing to their hydrophobicity and molecular shape. The toxicity of each pesticide was well represented by an equation that combined the calcein release rate constant of the DPPC liposomes and the initial calcein release rate of the 33 ​mol% DOPC mixed liposomes. The findings indicate that stimuli-response assays using liposomes can be used to complement traditional ecotoxicity assessments.

Antimicrobial Nanoformulations Based on Schinus areira Essential Oil

The goal of this research was to create an antibacterial formulation from Scinus areira essential oil (EO) that could spread in water. To achieve this, we developed liposomal formulations of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) or DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) that encapsulated the EO. In addition, we utilized the EO as a reducing and stabilizing agent to synthesize silver nanoparticles (AgNPs). The nanoformulations were characterized by determining their size and zeta potential. In the case of liposomal formulations, chemical composition, and encapsulation efficiency were also determined. Furthermore, antimicrobial activity studies against Gram-positive and Gram-negative model bacteria were carried out for both kinds of formulations. The results obtained showed the successful encapsulation of the S. areira EO in multilamellar liposomes of phosphatidylcholine with high efficiency. DPPC liposomes have proven to be a better encapsulation system, retaining more monoterpenes from the EO and therefore presenting antimicrobial activity against S. aureus with an minimal inhibitory concentration (MIC) value of 3 mg/mL of EO. On the other hand, it was also possible to obtain AgNPs by using S. areira EO, which showed antimicrobial activity against S. aureus and E. coli at low concentrations of EO, with MIC values of 6.68 µg/mL and 3.4 µg/mL of silver, respectively. The data obtained will contribute to enhancing the biotechnological value of natural products derived from native plant species in Argentina. This will be achieved through the generation of novel formulations with antibacterial activity and potential bioavailability.

Synthesis and Evaluation of Clinically Translatable Targeted Microbubbles Using a Microfluidic Device for In Vivo Ultrasound Molecular Imaging.

The main aim of this study is to synthesize contrast microbubbles (MB) functionalized with engineered protein ligands using a microfluidic device to target breast cancer specific vascular B7-H3 receptor in vivo for diagnostic ultrasound imaging. We used a high-affinity affibody (ABY) selected against human/mouse B7-H3 receptor for engineering targeted MBs (TMBs). We introduced a C-terminal cysteine residue to this ABY ligand for facilitating site-specific conjugation to DSPE-PEG-2K-maleimide (M. Wt = 2.9416 kDa) phospholipid for MB formulation. We optimized the reaction conditions of bioconjugations and applied it for microfluidic based synthesis of TMBs using DSPE-PEG-ABY and DPPC liposomes (5:95 mole %). The binding affinity of TMBs to B7-H3 (MBB7-H3) was tested in vitro in MS1 endothelial cells expressing human B7-H3 (MS1B7-H3) by flow chamber assay, and by ex vivo in the mammary tumors of a transgenic mouse model (FVB/N-Tg (MMTV-PyMT)634Mul/J), expressing murine B7-H3 in the vascular endothelial cells by immunostaining analyses. We successfully optimized the conditions needed for generating TMBs using a microfluidic system. The synthesized MBs showed higher affinity to MS1 cells engineered to express higher level of hB7-H3, and in the endothelial cells of mouse tumor tissue upon injecting TMBs in a live animal. The average number (mean ± SD) of MBB7-H3 binding to MS1B7-H3 cells was estimated to be 354.4 ± 52.3 per field of view (FOV) compared to wild-type control cells (MS1WT; 36.2 ± 7.5/FOV). The non-targeted MBs did not show any selective binding affinity to both the cells (37.7 ± 7.8/FOV for MS1B7-H3 and 28.3 ± 6.7/FOV for MS1WT cells). The fluorescently labeled MBB7-H3 upon systemic injection in vivo co-localized to tumor vessels, expressing B7-H3 receptor, as validated by ex vivo immunofluorescence analyses. We have successfully synthesized a novel MBB7-H3 via microfluidic device, which allows us to produce on demand TMBs for clinical applications. This clinically translatable MBB7-H3 showed significant binding affinity to vascular endothelial cells expressing B7-H3 both in vitro and in vivo, which shows its potential for clinical translation as a molecular ultrasound contrast agent for human applications.

Assessment of DPPC Liposome Disruption by Embedded Tocopheryl Malonate

In this study, the effect of α-tocopheryl malonate (TM) on physical and structural properties of DPPC liposomes was investigated using ANS fluorescence, DPH, and TMA–DPH anisotropy fluorescence and differential scanning calorimetry (DSC) methods. The presence of embedded TM in DPPC liposomes caused alteration in its phase transition temperatures, structural order, dynamics, and hydration of head groups increasingly with growing TM concentration. The ANS fluorescence results demonstrated that increasing TM presence in the DPPC gel phase due to interrupted membrane structure caused the formation of new binding sites. Temperature investigations in the range of 20 °C to 60 °C showed that increasing temperature rises ANS fluorescence which reaches local and global maxima at 36 °C and 42 °C, respectively. The rising TM concentration at the phase transition temperature of DPPC led to the lowering of ANS fluorescence, indicating a decreased binding of ANS. Simultaneously, during heating, a roughly 10-nm shift of ANS emission maximum was observed. The results indicated that in the fluid phase, the observed quenching appears as a result of increasing accessibility of water molecules into ANS in this region. The DPH results indicated that in the gel phase presence of TM introduced disorder in the hydrophobic acyl chain region led to its fluidization. The TMA–DPH results indicated an increasing disorder in the interface region and an increasing hydration of head group atoms at the surface of the membrane. The increasing concentration of TM results in the formation of multicomponent DSC traces, suggesting the formation of another structural phase. The applied methods proved that the incorporation of TM into DPPC membrane results in the interaction of malonate moiety with DPPC head group atoms in the interphase layer and induces the interruption in the membrane packing order, leading to its structural changes. The presented results show that TM presence could regulate the membrane properties, thus it may indicate one of the possible mechanisms responsible for the effective disruption of cell membranes by TM. The knowledge of molecular mechanism how TM interacts with the membrane will help to elucidate its possible pharmacological activity.

Efficient controlled release of cannabinoids loaded in γ-CD-MOFs and DPPC liposomes as novel delivery systems in oral health

Olivetol (OLV), as a cannabidiol (CBD) analog, was incorporated in γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes as potential analgesic drug delivery systems (DDS) for dental hypersensitivity (DH) treatment. These DDS have been scarcely employed in oral health, being the first time in case of MOFs loaded with cannabinoids. In vitro experiments using bovine teeth were performed to verify if the drug is able to reach the dentin, where it can flow to the pulp tissues and exert its analgesic effect; enamel and dentin regions were analyzed by synchrotron radiation-based FTIR microspectroscopy. Principal component analysis (PCA) was used to process the spectroscopic data as a powerful chemometric tool, and it revealed a similar behavior in both regions. The studied DDS have been characterized by different techniques, and is was demonstrated that DDS is an efficient way to carry the drug through dental tissues without compromising their structure.Graphical

Hybrid liposome-erythrocyte drug delivery system for tumor therapy with enhanced targeting and blood circulation.

Liposome, a widely used drug delivery system (DDS), still shows several disadvantages such as dominant clearance by liver and poor target organ deposition. To overcome the drawbacks of liposomes, we developed a novel red blood cell (RBC)-liposome combined DDS to modulate the tumor accumulation and extend the blood circulation life of the existing liposomal DDS. Here, RBCs, an ideal natural carrier DDS, were utilized to carry liposomes and avoid them undergo the fast clearance in the blood. In this study, liposomes could either absorbed onto RBCs' surface or fuse with RBCs' membrane by merely altering the interaction time at 37°C, while the interaction between liposome and RBCs would not affect RBCs' characteristics. In the in vivo antitumor therapeutic efficacy study, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes attached onto RBCs' surfaces exhibited lung targeting effect (via RBC-hitchhiking approach) and reduced clearance in the liver, while DPPC liposomes fused with RBCs had prolong blood circulation up to 48 h and no enrichment in any organ. Furthermore, 20 mol% of DPPC liposomes were replaced with pH-sensitive phospholipid 1,2-dioleoyl-Sn-glycero-3-phosphoethanolamine (DOPE) as it could respond to the low pH tumor microenvironment and then accumulate in the tumor. The DOPE attached/fusion RBCs showed partial enrichment in lung and about 5-8% tumor accumulation, which were significantly higher than (about 0.7%) the conventional liposomal DDS. Thus, RBC-liposome composite DDS is able to improve the liposomal tumor accumulation and blood circulation and shows the clinical application promises of using autologous RBCs for antitumor therapy.

Establishing a Robust and Reliable Response from a Potent Osmium-Based Photosensitizer Via Lipid Nanoformulation†.

Osmium (Os) based photosensitizers (PSs) are a unique class of nontetrapyrrolic metal-containing PSs that absorb red light. We recently reported a highly potent Os(II) PS, rac-[Os(phen)2 (IP-4T)](Cl)2 , referred to as ML18J03 herein, with light EC50 values as low as 20 pm. ML18J03 also exhibits low dark toxicity and submicromolar light EC50 values in hypoxia in some cell lines. However, owing to its longer oligothiophene chain, ML18J03 is not completely water soluble and forms 1-2 μm sized aggregates in PBS containing 1% DMSO. This aggregation causes variability in PDT efficacy between assays and thus unreliable and irreproducible reports of invitro activity. To that end, we utilized PEG-modified DPPC liposomes (138 nm diameter) and DSPE-mPEG2000 micelles (10.2 nm diameter) as lipid nanoformulation vehicles to mitigate aggregation of ML18J03 and found that the spectroscopic properties important to biological activity were maintained or improved. Importantly, the lipid formulations decreased the interassay variance between the EC50 values by almost 20-fold, with respect to the unformulated ML18J03 when using broadband visible light excitation (P =0.0276). Herein, lipid formulations are presented as reliable platforms for more accurate invitro photocytotoxicity quantification for PSs prone to aggregation (such as ML18J03) and will be useful for assessing their invivo PDT effects.

Protective Effects of Resveratrol Encapsulated In Liposomes or PLA Nanoparticles against Oxidative Stress in NRK-52E Cells

Liposomes and Polymeric nanoparticles are nanocarriers that can be used to enhance the pharmacokinetics of different drugs. The objective of the current study was to encapsulate resveratrol in DPPC liposomes and PLA nanoparticles; separately for the amelioration of PQ-induced oxidative stress on NRK-52E cells. Liposomes were produced by the hydration of a lipid film. Polymeric nanoparticles were prepared by double emulsification solvent diffusion method using PLA. They were then characterized for their particle size, zeta potential, drug loading, antioxidant activity, toxicity on NRK-52E cells, and protection against paraquat oxidation. The mean particle size for liposomes and PLA nanoparticles were respectively 197.4 ± 102.4 and 457.9 ± 56.1 nm and their surface zeta-potentials were -7.86 ± 6.36 and -21.6 ± 10.4 mV; respectively. LM and SEM images showed both types of nanoparticles to be spherical in shape. %LE efficiency for liposomes (12.04 ± 1.23%) was quite low compared to PLA nanoparticles (40.81 ± 29.14%). However, the % internalization for liposomes (5.95 ± 0.09%) was around 11 times higher than free resveratrol compared to PLA nanoparticles (0.93 ± 0.03%) which were only around two-fold higher. The toxicity tests showed that both liposomes and PLA nanoparticle forms of resveratrol showed less harmful effect on the cells than its free form mainly in the LDH assay. Furthermore, the benefit of encapsulation was also clear in the activity tests against PQ on the NRK-52E cell. From these results, it can be concluded that resveratrol-loaded liposomes and PLA nanoparticles can show more benefits over free resveratrol.

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

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