Charged Liposomes Research Articles

Negatively charged liposomes of sertraline hydrochloride: Formulation, characterization and pharmacokinetic studies

The present study was carried out with an objective to study the extent of delivery of negatively charged liposomes of sertraline hydrochloride to brain via intravenous route for treatment of depressive –like symptoms. Liposomes of sertraline hydrochloride were formulated by film hydration technique using cholesterol, hydrogenated soya phosphatidylcholine-l-α-phosphatidylcholine, and distearoyl phosphatidyl glycerol sodium. Uniform sized vesicles with porous surface morphology with vesicle size of 151.59 nm were prepared. Radioactive imaging performed using 99mTcO4 showed ~5% of uptake of labelled liposomes in brain within 2 h of administration. On administration of liposomes and free drug suspension, approximately, 205.06 ng/ml and 87.18 ng/ml of sertraline were estimated in brain at 36 h. The liposomes can be transported by transcelluar transport which includes phagocytosis and the use of phosphatidylcholine enhances macrophage internalization and delivery to brain. The study indicated significantly higher concentration of sertraline in brain after 36 h, on administration of liposomes as compared to free sertraline suspension.

The effect of ethanol evaporation on the properties of inkjet produced liposomes

BackgroundInkjet method has been used to produce nano-sized liposomes with a uniform size distribution. However, following the production of liposomes by inkjet method, the solvent residue in the product could have a significant effect on the properties of the final liposomes.ObjectiveThis research paper aimed to find a suitable method to remove ethanol content and to study its effect on the properties of the final liposomal suspension.MethodEgg phosphatidylcholine and lidocaine were dissolved in ethanol; and inkjet method at 80 kHz was applied to produce uniform droplets, which were deposited in an aqueous solution to form liposomes. Dry nitrogen gas flow, air-drying, and rotary evaporator were tested to remove the ethanol content. Liposome properties such as size, polydispersity index (PDI), and charge were screened before and after ethanol evaporation.ResultsOnly rotary evaporator (at constant speed and room temperature for 2 h) removed all of the ethanol content, with a final drug entrapment efficiency (EE) of 29.44 ± 6.77%. This was higher than a conventional method. Furthermore, removing ethanol led to liposome size reduction from approximately 200 nm to less than 100 nm in most samples. Additionally, this increased the liposomal net charge, which contributed to maintain the uniform and narrow size distribution of liposomes.ConclusionNano-sized liposomes were produced with a narrow PDI and higher EE compared to a conventional method by using an inkjet method. Moreover, rotary evaporator for 2 h reduced effectively the ethanol content, while maintaining the narrow size distribution.Graphical abstract

Cationic liposomes for generic signal amplification strategies in bioassays

Liposomes have been widely applied in bioanalytical assays. Most liposomes used bare negative charges to prevent non-specific binding and increase colloidal stability. Here, in contrast, highly stable, positively charged liposomes entrapping the fluorescent dye sulforhodamine B (SRB) were developed to serve as a secondary, non-specific label‚ and signal amplification tool in bioanalytical systems by exploiting their electrostatic interaction with negatively charged vesicles, surfaces, and microorganisms. The cationic liposomes were optimized for long-term stability (> 5 months) and high dye entrapment yield. Their capability as secondary, non-specific labels was first successfully proven through electrostatic interactions of cationic and anionic liposomes using dynamic light scattering, and then in a bioassay with fluorescence detection leading to an enhancement factor of 8.5 without any additional surface blocking steps. Moreover, the cationic liposomes bound efficiently to anionic magnetic beads were stable throughout magnetic separation procedures and could hence serve directly as labels in magnetic separation and purification strategies. Finally, the electrostatic interaction was exploited for the direct, simple, non-specific labeling of gram-negative bacteria. Isolated Escherichia coli cells were chosen as models and direct detection was demonstrated via fluorescent and chemiluminescent liposomes. Thus, these cationic liposomes can be used as generic labels for the development of ultrasensitive bioassays based on electrostatic interaction without the need for additional expensive recognition units like antibodies, where desired specificity is already afforded through other strategies.Graphical abstract

Improved melanoma suppression with target-delivered TRAIL and Paclitaxel by a multifunctional nanocarrier

Malignant melanoma, a highly dangerous type of skin cancer, is usually resistant to pro-apoptosis agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) due to low death receptor expression levels. After verifying combination of chemotherapy drug paclitaxel (PTX) and TRAIL could significantly enhance their anti-melanoma effects, we developed a liposomal melanoma target-delivery system with tumor microenvironment responsiveness (TRAIL-[Lip-PTX]C18-TR) to co-deliver TRAIL and PTX. TRAIL is attached to negatively-charged liposome surface while PTX is encapsulated inside, with final surface modification of a stearyl chain (C18) fused pH-sensitive cell-penetrating peptide (TR). Here, C18-TR could specifically binds to melanoma-rich integrin receptors αvβ3 for melanoma targeting, help release TRAIL in low pH microenvironment by reversing the liposomal charge, and facilitate consequent liposome internalization. TRAIL-[Lip-PTX]C18-TR displayed significantly better in vitro half-maximal inhibitory concentration (IC50) than other formulations, and an in vivo tumor inhibition rate of 93.8%. Mechanistic study revealed that this synergistic effect is associated with the upregulation of death receptors DR4/5 by PTX. This co-delivery system significantly improved TRAIL-based therapy against melanoma, and provided a simple platform to co-deliver other drugs/agents for melanoma treatment.

Electrostatic Environment of Proteorhodopsin Affects the pKa of Its Buried Primary Proton Acceptor

The protonation state of embedded charged residues in transmembrane proteins (TMPs) can control the onset of protein function. It is understood that interactions between an embedded charged residue and other charged or polar residues in the moiety would influence its pKa, but how the surrounding environment in which the TMP resides affects the pKa of these residues is unclear. Proteorhodopsin (PR), a light-responsive proton pump from marine bacteria, was used as a model to examine externally accessible factors that tune the pKa of its embedded charged residue, specifically its primary proton acceptor D97. The pKa of D97 was compared between PR reconstituted in liposomes with different net headgroup charges and equilibrated in buffer with different ion concentrations. For PR reconstituted in net positively charged compared to net negatively charged liposomes in low-salt buffer solutions, a drop of the apparent pKa from 7.6 to 5.6 was observed, whereas intrinsic pKa modeled with surface pH calculated from Gouy-Chapman predictions found an opposite trend for the pKa change, suggesting that surface pH does not account for the main changes observed in the apparent pKa. This difference in the pKa of D97 observed from PR reconstituted in oppositely charged liposome environments disappeared when the NaCl concentration was increased to 150 mM. We suggest that protein-intrinsic structural properties must play a role in adjusting the local microenvironment around D97 to affect its pKa, as corroborated with observations of changes in protein side-chain and hydration dynamics around the E-F loop of PR. Understanding the effect of externally controllable factors in tuning the pKa of TMP-embedded charged residues is important for bioengineering and biomedical applications relying on TMP systems, in which the onset of functions can be controlled by the protonation state of embedded residues.

Counterintuitive Electrostatic Forces in Liposome Colloidal Crystals

We previously studied the repulsive electrostatic forces among like-charged liposomes in deionized water by measuring the shear moduli (rigidity, stiffness) of liposome-water suspensions as a function of liposome charge and concentration (Cohen, Wei & Ou-Yang). The liposomes were extruded, unilamellar, 100 nm, made of weak-acid POPG and zwitterionic POPC mixtures in incremental ratios. At low charge the shear moduli increased with liposome PG content as expected, reaching a maximum at ∼20% PG, then decreased with further increase of PG. At 100% PG the suspension was flaccid with a shear modulus near zero. Our measurements show that in deionized water weakly-charged liposomes interact strongly, and strongly-charged liposomes interact weakly. Here we analyze this counterintuitive finding. We use a Debye-Hückel (DH) Wigner-Seitz (WS) model to calculate electrostatic potentials and electric fields in the suspensions analytically. The unusual bulk behavior arises from a strict correlation, mandated by global electroneutrality, between the deprotonated PG liposome charge and the number of solvated H+ ions in a WS cell. We map the conditions for weak vs. strong inter-liposome forces in terms of the H+ screening length relative to the WS sphere radius, which is a measure of the mean distance between liposomes. The H+ screening length depends on the solvated H+ mean concentration, hence on the net liposome charge including charge-regulation effects. The liposome surface potentials are shown to be small, which justifies use of the DH approximation. We plot electrostatic-potential and pH profiles in a WS cell as a function of the liposome PG/PC ratio, calculate PG/PC at the crossover from strong to weak coupling, and determine the added-salt concentration required to mask the above effects. These results may be relevant to protein-protein interactions in low ionic-strength electrolytes.

Competition Between Heparin and Polyethylene Glycol as Biofunctionalization for Improving Stability of Liposomal Doxorubicin

In order to improve liposomal doxorubicin stability, differentiation between Heparin and Polyethylene Glycol (PEG) as biofunctionalization for liposomal doxorubicin has been investigated by measuring the entrapment efficiency, size distribution, zeta potential, evaluating the in vitro potential cytotoxicity against MCF-7 (Breast cancer cell) and stability in serum by measuring the drug release rate. We synthesized Four liposomal formulations: (A) Conventional liposomes; DPPC:DOX, (B) Positively charged PEGylated liposomes; DPPC:CHOL:SA:PEG:DOX (C) Negatively charged PEGylated liposomes: DPPC:CHOl:DCP:PEG:DOX (D) positively charged liposomes to conjugate heparin; DPPC:CHOL:SA:DOX. Entrapment efficiency of doxorubicin dramatically increased after PEGylation and conjugation with heparin. In addition, zeta potential was changed upon the encapsulation of doxorubicin into conventional and PEGylated liposomes which indicates that DOX encapsulated completely into liposomes. For heparin conjugated liposomes, zeta potential was slightly changed. Sulphorhodamine-B (SRB) assay showed a greater cytotoxic effect of the liposomal doxorubicin formulations at different concentrations with respect to free drug against MCF-7 cell lines. The anticancer activity order was observed between the various liposome formulations, especially those observed with conjugated heparin liposomes. Slower drug release rate showed an order of D > C > B > A that means stability showed an order of D > C > B > A. From above results, the most stable liposomal doxorubicin formulation was the liposomal formulation D. The results optimized using heparin than PEG as biofunctionalization. Further studies are suggested for better understanding why heparin improves the stability of liposomal doxorubicin.

Dynamic Behavior of Complex Coacervates with Internal Lipid Vesicles under Nonequilibrium Conditions

During the evolution of life on earth, the emergence of lipid membrane-bounded compartments is one of the most enigmatic events. Endosymbiosis has been hypothesized as one of the solutions. In this work, using a coacervate droplet formed by single-stranded oligonucleotides (ss-oligo) and poly(l-lysine) (PLL) as the protocell model, we monitored the uptake of liposomes of different types and studied the dynamic behavior of the resulting composite droplet under the electric field. The coacervate droplet exhibits affinity for the liposomes of varying charges. However, the permeation of liposome is also controlled by electrostatic interactions. Dominated by electrostatic attraction, the positively charged liposome is retained inside the droplet as growing fibrous structures, while the negatively charged liposome is mainly coated on the droplet surface. Permeation and even distribution occur when the liposome and the droplet carry the same charges, or at least one of them is neutral. As an electric field is applied to trigger repetitive cycles of vacuolization in the ss-oligo/PLL droplet, the fibrous structure formed by the positively charged liposome is basically intact, while a new phase is generated together with uneven mass transport as the negatively charged liposome is internalized. Interestingly, the release of daughter droplets with similar components occurs on the droplet containing neutral liposomes. Our work not only provides a step toward creating protocells with hierarchical structures and biofunctions using a biogenetic material via simple mixing but also sheds light on the possible origin of the lipid structure inside a living organism.

Low-intensity light-induced drug release from a dual delivery system comprising of a drug loaded liposome and a photosensitive conjugate

This study reports the development of a binary drug delivery system consisting of charged liposomes and an oppositely charged peptide–photosensitiser conjugate. Liposomes were prepared with phosphatidyl-l-serine as a negatively charged lipid. Calcein, a fluorophore marker, and doxorubicin, an anticancer drug, were used as model hydrophilic loads. The conjugate consisted of a positively charged arginine-rich peptide synthesised by solid-phase peptide synthesis, and a phthalocyanine derivative with characteristic absorption around 685 nm. Illumination of the binary system with far-red light of 12–15 mW/cm2 intensity resulted in 5- to 15-fold increase in release of payloads from the liposomes. The mechanism of drug release was based on photosensitised oxidation of lipids destabilising the liposomal membrane. The cytotoxicity of the liposomes loaded with doxorubicin was tested on B16-F10 melanoma and Y79 retinoblastoma cells. The cytotoxicity of the illuminated binary system in melanoma cell line was significantly higher as compared to the system without illumination. The components of the binary system can be individually prepared and stored with greater storage stability. However, their combination will allow for substantial release of hydrophilic payload from the liposomes under externally applied light.

Effect of surface charge of gold nanoparticles on fluorescence amplification of polydiacetylene-based liposomes

Polydiacetylene (PDA)-based liposome have been attractive as sensory platforms owing to their applicability in simultaneous detection of colorimetric and fluorogenic signals. As PDA show low quantum yield, gold nanoparticles (GNPs) were used to amplify the fluorescence of the PDA by localized surface plasmon resonance. In this study, positively and negatively surface charged GNPs at different concentrations were complexed with negatively charged PDA liposome (GNP/PDA). Positively charged GNPs caused tight binding at the surface of negatively charged PDA liposome, became aggregated due to colloidal instability and thereby dramatically quenched the fluorescence of PDA. While negatively charged GNPs sparsely placed on the surface of the PDA liposome, at the optimized complexing condition, generated ∼10%of fluorescence amplification compared to non-complexed PDA liposome as observed by the photoluminescence spectra of the stable colloids. Under the optimum incubation conditions, GNP/PDA liposome that specifically binds with Pb2+ via its phenolic group, exhibited increased fluorescence intensity compared to the non-complexed PDA liposome-at the same concentration of target Pb2+.

Novel Liposome Aggregate Platform (LAP) system for sustained retention of drugs in the posterior ocular segment following intravitreal injection.

A novel Liposome Aggregate Platform (LAP) system for prolonged retention of drugs in the posterior eye segment after intravitreal injection (IVT) was developed and evaluated. Calcein, FITC-dextran-4000 (FD4) and Flurbiprofen (FLB), were encapsulated in negatively charged liposomes, and mixed with protamine to produce the LAP. The lipid/protamine ratio was fixed, in order to have a convenient aggregation rate permitting IVT injection and also a sustained release of liposome-entrapped molecules (in vitro) from LAP. In vitro release studies confirmed the potential of LAP system consisted of HPC/DPPG/Chol liposomes and protamine (at 1:1 w/w to lipid), to delay calcein, FD4 and FLB release, compared to free liposomes. In vivo studies demonstrated increased vitreous retention of liposomes and LAP for all molecules, compared to the corresponding solutions; however the retention of FD4 is similar for non-aggregated liposomes and LAP, and calcein retention is only slightly increased by LAP compared to liposomes. The later result may be connected with the visible ocular inflammation caused by both dyes; interestingly inflammation was moderately reduced when dyes were entrapped in liposomes and even more when in LAP. No visible inflammation was demonstrated for FLB, and the LAP system significantly increased the retention of FLB in the ocular tissues (compared to non-aggregated liposomes). Taking into account the capability of the novel LAP system to decrease inflammatory reactions towards calcein and FD4, and prolong the retention of FLB in ocular tissues, it is concluded that such systems, after further optimization, may be considered as promising effective and safe approaches for treatment of posterior segment ocular pathologies.

Curcumin-In-Deformable Liposomes-In-Chitosan-Hydrogel as a Novel Wound Dressing.

A liposomes-in-hydrogel system as an advanced wound dressing for dermal delivery of curcumin was proposed for improved chronic wound therapy. Curcumin, a multitargeting poorly soluble active substance with known beneficial properties for improved wound healing, was incorporated in deformable liposomes to overcome its poor solubility. Chitosan hydrogel served as a vehicle providing superior wound healing properties. The novel system should assure sustained skin delivery of curcumin, and increase its retention at the skin site, utilizing both curcumin and chitosan to improve the therapy outcome. To optimize the properties of the formulation and determine the effect of the liposomal charge on the hydrogel properties, curcumin-containing deformable liposomes (DLs) with neutral (NDLs), cationic (CDLs), and anionic (ADLs) surface properties were incorporated in chitosan hydrogel. The charged DLs affected the hydrogel’s hardness, cohesiveness, and adhesiveness. Importantly, the incorporation of DLs, regardless of their surface charge, in chitosan hydrogel did not decrease the system’s bioadhesion to human skin. Stability testing revealed that the incorporation of CDLs in hydrogel preserved hydrogel´s bioadhesiveness to a higher degree than both NDLs and ADLs. In addition, CDLs-in-hydrogel enabled the most sustained skin penetration of curcumin. The proposed formulation should be further evaluated in a chronic wound model.

Poly(Sarcosine) Surface Modification Imparts Stealth-Like Properties to Liposomes.

Circulation lifetime is a crucial parameter for a successful therapy with nanoparticles. Reduction and alteration of opsonization profiles by surface modification of nanoparticles is the main strategy to achieve this objective. In clinical settings, PEGylation is the most relevant strategy to enhance blood circulation, yet it has drawbacks, including hypersensitivity reactions in some patients treated with PEGylated nanoparticles, which fuel the search for alternative strategies. In this work, lipopolysarcosine derivatives (BA-pSar, bisalkyl polysarcosine) with precise chain lengths and low polydispersity indices are synthesized, characterized, and incorporated into the bilayer of preformed liposomes via a post insertion technique. Successful incorporation of BA-pSar can be realized in a clinically relevant liposomal formulation. Furthermore, BA-pSar provides excellent surface charge shielding potential for charged liposomes and renders their surface neutral. Pharmacokinetic investigations in a zebrafish model show enhanced circulation properties and reduction in macrophage recognition, matching the behavior of PEGylated liposomes. Moreover, complement activation, which is a key factor in hypersensitivity reactions caused by PEGylated liposomes, can be reduced by modifying the surface of liposomes with an acetylated BA-pSar derivative. Hence, this study presents an alternative surface modification strategy with similar benefits as the established PEGylation of nanoparticles, but with the potential of reducing its drawbacks.

Sertraline Delivered in Phosphatidylserine Liposomes Is Effective in an Experimental Model of Visceral Leishmaniasis.

Liposomes containing phosphatidylserine (PS) has been used for the delivery of drugs into the intramacrophage milieu. Leishmania (L.) infantum parasites live inside macrophages and cause a fatal and neglected viscerotropic disease, with a toxic treatment. Sertraline was studied as a free formulation (SERT) and also entrapped into phosphatidylserine liposomes (LP-SERT) against intracellular amastigotes and in a murine model of visceral leishmaniasis. LP-SERT showed a potent activity against intracellular amastigotes with an EC50 value of 2.5 μM. The in vivo efficacy of SERT demonstrated a therapeutic failure. However, when entrapped into negatively charged liposomes (−58 mV) of 125 nm, it significantly reduced the parasite burden in the mice liver by 89% at 1 mg/kg, reducing the serum levels of the cytokine IL-6 and upregulating the levels of the chemokine MCP-1. Histopathological studies demonstrated the presence of an inflammatory infiltrate with the development of granulomas in the liver, suggesting the resolution of the infection in the treated group. Delivery studies showed fluorescent-labeled LP-SERT in the liver and spleen of mice even after 48 h of administration. This study demonstrates the efficacy of PS liposomes containing sertraline in experimental VL. Considering the urgent need for VL treatments, the repurposing approach of SERT could be a promising alternative.

Metformin-Encapsulated Liposome Delivery System: An Effective Treatment Approach against Breast Cancer.

This study aimed at developing metformin hydrochloride (Met) encapsulated liposomal vesicles for enhanced therapeutic outcomes at reduced doses against breast cancer. Liposomal Met was prepared using thin-film hydration through various loading methods; passive loading, active loading, and drug-loaded lipid film. The drug-loaded film method exhibited maximum entrapment efficiency (~65%) as compared to active loading (~25%) and passive loading (~5%) prepared Met-loaded liposomes. The therapeutic efficacy of these optimized liposomes was evaluated for cellular uptake, cytotoxicity, inhibition of metastatic activity, and apoptosis-inducing activity. Results demonstrated significantly superior activity of positively charged liposomes resulting in reduced IC50 values, minimal cell migration activity, reduced colony formation, and profound apoptosis-induced activity in breast cancer cells as compared to Met. The anti-tumor activity was investigated using a clinically relevant in vitro tumor simulation model, which confirmed enhanced anti-tumorigenic property of liposomal Met over Met itself. To the authors’ knowledge, this is the first report of Met-loaded liposomes for improving the efficacy and therapeutic effect of Met against breast cancer. With the results obtained, it can be speculated that liposomal encapsulation of metformin offers a potentially promising and convenient approach for enhanced efficacy and bioavailability in breast cancer treatment.

Didodecyldimethylammonium Bromide Role in Anchoring Gold Nanoparticles onto Liposome Surface for Triggering the Drug Release.

Liposomes with their capacity to anchor gold nanoparticles (AuNPs) onto their surface are used in the treatment of several pathologies such as cancer. The objective of this work was the optimization of the vesicle composition by using cationic agents in order to reinforce the anchoring process of AuNPs, and for the study of the influence of local temperature and vesicle size on drug release. A Plackett-Burman design was conducted to determine the optimal composition for the anchoring of AuNPs. A comprehensive study of the influence of lipid bilayer composition on the surface charge, size, and polydispersity index (PdI) of liposomes was carried out. Afterwards, in vitro release studies by dialysis were performed and several release parameters were evaluated as a function of temperature. Cholesterol was fixed as the rigid agent and Didodecyldimethylammonium bromide (DDAB) was selected as the cationic lipid into the liposome bilayer. Photomicrographs revealed that DDAB facilitated the anchoring of AuNPs onto the liposomal surface. The anchoring of AuNPs also enhanced the amount and rate of calcein released, especially in extruded samples, at several incubating temperatures. In addition, it was observed that both the anchoring of AuNPs and the calcein release were improved by increasing the surface of the vesicles. The contributions of liposome composition (DDAB inclusion, incubation temperature, anchoring of AuNPs) and size and surface availability of the vesicles on calcein release could be used to design improved lipid nanostructures for the controlled release of anticancer drugs.

Protein surface charge effect on 3D domain swapping in cells for c-type cytochromes

Many c-type cytochromes (cyts) can form domain-swapped oligomers. The positively charged Hydrogenobacter thermophilus (HT) cytochrome (cyt) c552 forms domain-swapped oligomers during expression in the Escherichia coli (E. coli) expression system, but the factors influencing the oligomerization remain unrevealed. Here, we found that the dimer of the negatively charged Shewanella violacea (SV) cyt c5 exhibits a domain-swapped structure, in which the N-terminal helix is exchanged between protomers, similar to the structures of the HT cyt c552 and Pseudomonas aeruginosa (PA) cyt c551 domain-swapped dimers. Positively charged horse cyt c and HT cyt c552 domain swapped during expression in E. coli, whereas negatively charged PA cyt c551 and SV cyt c5 did not. Oligomers were formed during expression in E. coli for HT cyt c552 attached to either a co- or post-translational signal peptide for transportation through the cytoplasm membrane, but not for PA cyt c551 attached to either signal peptide. HT cyt c552 formed oligomers in E. coli in the presence and absence of rare codons. More oligomers were obtained from the in vitro folding of horse cyt c and HT cyt c552 by the addition of negatively charged liposomes during folding, whereas the amount of oligomers for the in vitro folding of PA cyt c551 and SV cyt c5 did not change significantly by the addition. These results indicate that the protein surface charge affects the oligomerization of c-type cyts in cells; positively charged c-type cyts assemble on a negatively charged membrane, inducing formation of domain-swapped oligomers during folding.

Growing a Nucleotide/Lanthanide Coordination Polymer Shell on Liposomes.

Coating liposomes with a shell is a useful strategy to increase membrane stability and prevent leakage or fusion. Nucleotide/lanthanide coordination nanoparticles (NPs) are formed by a simple mixing at ambient conditions. Because some lipid headgroups contain lanthanide binding ligands, they may direct the growth of such coordination NPs. Herein, a gadolinium/adenosine monophosphate (Gd3+/AMP) shell was formed on liposomes (liposome@Gd3+/AMP) using lipids containing phosphoserine (PS) or cholinephosphate (CP) headgroups, while phosphocholine liposomes did not support the shell. Liposome binding Gd3+ is confirmed by transmission electron microscopy (TEM). The negatively charged CP and PS liposomes reversed to positive upon Gd3+ binding, while other metals such as Ca2+ and Zn2+ did not reverse the charge. Binding of Gd3+ did not leak the PS liposomes. Then, AMP was further added to cross-link Gd3+ on the liposome surface. A shell was formed as indicated by TEM, and the content inside the liposome remained for the PS liposomes. While adding Triton X-100 still induced leakage of the encapsulated liposomes, the shell protected the liposomes from leakage induced by ZnO NPs, suggesting a porous structure of the Gd3+/AMP shell which allowed penetration of Triton X-100 but not the larger ZnO NPs. This work provides a simple method to coat liposomes, and also offers a fundamental understanding of liposome adsorption of lanthanide ions.

Coating of Nanolipid Structures by a Novel Simil-Microfluidic Technique: Experimental and Theoretical Approaches

Nanolipid vesicular structures are ideal candidates for the controlled release of various ingredients, from vitamins for nutraceutical purposes to chemoterapic drugs. To improve their stability, permeability, and some specific surface properties, such as mucoadhesiveness, these structures can require a process of surface engineering. The interaction of lipid vesicles with oppositely charged polyelectrolytes seems to be an interesting solution, especially when the negatively charged liposomes are complexed with the cationic chitosan. In this work, a novel simil-microfluidic technique was used to produce both chitosan-coated vesicles and a vegan alternative composed of cholesterol-free liposomes coated by Guar Hydroxypropyltrimonium Chloride (Guar-HC). The combination between the experimental approach, based on experimental observations in terms of Z-potential, and size evolutions, and the theoretical approach, based on concepts of saturation, was the methodology applied to define the best polycation concentration to fairly cover (vegan or not) liposomes without aggregation. The smart production of coated nanolipid structures was confirmed by characterizations of morphology, mucoadhesiveness, and stability.

Effect of Different Charged Liposomes on Transmembrane Incorporation Efficiency of the Staphylococcus Aureus Receptor Histidine Kinase AgrC

AgrC is a membrane-embedded histidine kinase in Staphylococcus aureus that is thought to act as a sensor for the recognition of environmental signals and the transduction of signals into the cytoplasm so as to regulate and control a series of related pathogenic gene expression. However, for the complexity of cell membrane, it turns to be difficult to study AgrC on bacterial cell membrane directly. Many researches tried to take advantage of proteoliposome which could provide an approximate natural membrane environment and keep the protein activity to study the structure and function of membrane proteins. In order to build a transmembrane protein incorporation system with a relatively high incorporation efficiency, function activity and stability, various factors were considered, such as the impact of different charge polarity head on protein transmembrane incorporation efficiency. Here, four kinds of different charged liposomes were prepared by changing the phospholipid components in liposome and a detergent-mediated method was used to reconstitute truncated AgrC protein(AgrC(TM6-7C)) into them. The results showed that negatively charged liposomes leaded to a higher incorporation efficiency compared with the positively charged one and about 60%-70% C-terminal cytoplasmic domain of AgrC(TM6-7C) c protein reconstituted into negatively charged liposomes were outside-orientated which remained a highly kinase activity. Furthermore, from circular dichroism detection result, we can draw a conclusion that liposome has certain protective effect on AgrC(TM6-7C)-protein secondary structure and improve the thermal stability of the protein.