Influence of liposome charge and composition on their interaction with human blood serum proteins

Advancements in liposomal formulations: A comprehensive exploration of industrial production techniques

Liposomes are nanosized, spherical vesicles consisting of an aqueous core encircled by one or more phospholipid bilayer shells. Liposomes have found extensive use in numerous biomedicine and nanomedicine applications due to their excellent biocompatibility, adaptable chemical composition, ease of preparation, and diverse structural characteristics. These applications include nanocarriers for drug delivery, immunoassays, nutraceuticals, tissue engineering, clinical diagnostics, and theranostics formulations. These applications stimulated significant efforts toward scaling up formation processes in anticipation of appropriate industrial advancement. Despite the advancements in conventional methods and the emergence of new approaches for liposome production, their inherent susceptibility to chemical and mechanical influences contributes to critical challenges, including limited colloidal stability and decreased efficiency in encapsulating cargo molecules. With this context, the current review provides brief insights into liposomes conventional and novel industrial production techniques. With a special focus on the structural parameters, and pivotal elements influencing the synthesis of an appropriate and stable formulation, followed by the various regulatory aspects of industrial production.

Liposome bilayer stability: emphasis on cholesterol and its alternatives

Liposomes are spherical lipidic nanocarriers composed of natural or synthetic phospholipids with a hydrophobic bilayer and aqueous core, which are arranged into a polar head and a long hydrophobic tail, forming an amphipathic nano/micro-particle. Despite numerous liposomal applications, their use encounters many challenges related to the physicochemical properties strongly affected by their constituents, colloidal stability, and interactions with the biological environment. This review aims to provide a perspective and a clear idea about the main factors that regulate the liposomes' colloidal and bilayer stability, emphasising the roles of cholesterol and its possible alternatives. Moreover, this review will analyse strategies that offer possible approaches to provide more stable in vitro and in vivo liposomes with enhanced drug release and encapsulation efficiencies.

AR13 peptide-conjugated liposomes improve the antitumor efficacy of doxorubicin in mice bearing C26 colon carcinoma; in silico, in vitro, and in vivo study

Currently, liposomes have emerged as efficient and safer nano-carriers for targeted therapy in different cancers. This work aimed to employ PEGylated liposomal doxorubicin (Doxil®/PLD), modified with AR13 peptide, to target Muc1 on the surface of colon cancerous cells. We performed molecular docking and simulation studies (using Gromacs package) of AR13 peptide against Muc1 to analyze and visualize the peptide-Muc1 binding combination. For in vitro analysis, the AR13 peptide was post-inserted into Doxil® and verified by TLC, ¹H NMR, and HPLC techniques. The zeta potential, TEM, release, cell uptake, competition assay, and cytotoxicity studies were performed. In vivo antitumor activities and survival analysis on mice bearing C26 colon carcinoma were studied. Results showed that after 100 ns simulation, a stable complex between AR13 and Muc1 formed, and molecular dynamics analysis confirmed this interaction. In vitro analysis demonstrated significant enhancement of cellular binding and cell uptake. The results of in vivo study on BALB/c mice bearing C26 colon carcinoma, revealed an extended survival time to 44 days and higher tumor growth inhibition compared to Doxil®. Thus, the AR13 peptide could be explored as a potent ligand for Muc1, improving therapeutic antitumor efficiency in colon cancer cells.

Tuning Liposome Stability in Biological Environments and Intracellular Drug Release Kinetics

Ideal drug carriers should be stable in biological environments but eventually release their drug load once inside the targeted cells. These two aspects can be in contrast with each other, thus they need to be carefully tuned in order to achieve the desired properties for specific applications. Quantifying drug release profiles in biological environments or inside cells can be highly challenging, and standard methods to determine drug release kinetics in many cases cannot be applied to complex biological environments or cells. Within this context, the present work combined kinetic studies by flow cytometry with aging experiments in biological fluids and size-exclusion chromatography to determine drug release profiles in biological environments and inside cells. To this purpose, anionic and zwitterionic liposomes were used as model nanomedicines. By changing lipid composition, liposome stability in serum and intracellular release kinetics could be tuned and formulations with very different properties could be obtained. The methods presented can be used to characterize liposome release profiles in complex biological media, as well as inside cells. In this way, liposome composition can be tuned in order to achieve formulations with optimal balance between stability and release kinetics for specific applications.

The effectiveness of ursolic acid niosomes with chitosan coating for prevention of liver damage in mice induced by n-nitrosodiethylamine

Ursolic acid (UA) is a pentacyclic triterpene carboxylic acid which produces various effects, including anti-cancer, hepatoprotective, antioxidant and anti-inflammatory. However, UA demonstrates poor water solubility and permeability. Niosomes have been reported to improve the bioavailability of low water-soluble drugs. This study aimed to investigate the protective action of UA-niosomes with chitosan layers against liver damage induced by N-Nitrosodiethylamine (NDEA). UA niosomes were prepared using a thin layer hydration method, with chitosan being added by vortexing the mixtures. For the induction of liver damage, the mice were administered NDEA intraperitoneally (25 mg/kgBW). They were given niosomes orally (11 mg UA/kgBW) seven and three days prior to NDEA induction and subsequently once a week with NDEA induction for four weeks. The results showed that chitosan layers increased the particle sizes, PDI, and ζ-potentials of UA niosomes. UA niosomes with chitosan coating reduced the SGOT and SGPT level. The histopathological evaluation of liver tissue showed an improvement with reduced bile duct inflammation and decreasing pleomorphism and enlargement of hepatocyte cell nuclei in UA niosomes with the chitosan coating treated group. It can be concluded that UA niosomes with chitosan coating improved the efficacy of preventive UA therapy in liver-damaged mice induced with NDEA.

Vesicular and Planar Membranes of Archaea Lipids: Unusual Physical Properties and Biomedical Applications

Liposomes and planar membranes made of archaea or archaea-like lipids exhibit many unusual physical properties compared to model membranes composed of conventional diester lipids. Here, we review several recent findings in this research area, which include (1) thermosensitive archaeosomes with the capability to drastically change the membrane surface charge, (2) MthK channel's capability to insert into tightly packed tetraether black lipid membranes and exhibit channel activity with surprisingly high calcium sensitivity, and (3) the intercalation of apolar squalane into the midplane space of diether bilayers to impede proton permeation. We also review the usage of tetraether archaeosomes as nanocarriers of therapeutics and vaccine adjuvants, as well as the biomedical applications of planar archaea lipid membranes. The discussion on archaeosomal therapeutics is focused on partially purified tetraether lipid fractions such as the polar lipid fraction E (PLFE) and glyceryl caldityl tetraether (GCTE), which are the main components of PLFE with the sugar and phosphate removed.

Designing Adjuvant Formulations to Promote Immunogenicity and Protective Efficacy of Leptospira Immunoglobulin-Like Protein A Subunit Vaccine

The leptospirosis burden on humans, especially in high-risk occupational groups and livestock, leads to public health and economic problems. Leptospirosis subunit vaccines have been under development and require further improvement to provide complete protection. Adjuvants can be used to enhance the amplitude, quality, and durability of immune responses. Previously, we demonstrated that LMQ adjuvant (neutral liposomes containing monophosphoryl lipid A (MPL) and Quillaja saponaria derived QS21 saponin) promoted protective efficacy of LigAc vaccine against Leptospira challenge. To promote immunogenicity and protective efficacy of the subunit vaccines, three alternative adjuvants based on neutral liposomes or squalene-in-water emulsion were evaluated in this study. LQ and LQuil adjuvants combined the neutral liposomes with the QS21 saponin or Quillaja saponaria derived QuilA^® saponin, respectively. SQuil adjuvant combined a squalene-in-water emulsion with the QuilA^® saponin. The immunogenicity and protective efficacy of LigAc (20 µg) formulated with the candidate adjuvants were conducted in golden Syrian hamsters. Hamsters were vaccinated three times at a 2-week interval, followed by a homologous challenge of L. interrogans serovar Pomona. The results showed that LigAc combined with LQ, LQuil, or SQuil adjuvants conferred substantial antibody responses and protective efficacy (survival rate, pathological change, and Leptospira renal colonization) comparable to LMQ adjuvant. The LigAc+LQ formulation conferred 62.5% survival but was not significantly different from LigAc+LMQ, LigAc+LQuil, and LigAc+SQuil formulations (50% survival). This study highlights the potential of saponin-containing adjuvants LMQ, LQ, LQuil, and SQuil for both human and animal leptospirosis vaccines.

Methods of Liposomes Preparation: Formation and Control Factors of Versatile Nanocarriers for Biomedical and Nanomedicine Application

Liposomes are nano-sized spherical vesicles composed of an aqueous core surrounded by one (or more) phospholipid bilayer shells. Owing to their high biocompatibility, chemical composition variability, and ease of preparation, as well as their large variety of structural properties, liposomes have been employed in a large variety of nanomedicine and biomedical applications, including nanocarriers for drug delivery, in nutraceutical fields, for immunoassays, clinical diagnostics, tissue engineering, and theranostics formulations. Particularly important is the role of liposomes in drug-delivery applications, as they improve the performance of the encapsulated drugs, reducing side effects and toxicity by enhancing its in vitro- and in vivo-controlled delivery and activity. These applications stimulated a great effort for the scale-up of the formation processes in view of suitable industrial development. Despite the improvements of conventional approaches and the development of novel routes of liposome preparation, their intrinsic sensitivity to mechanical and chemical actions is responsible for some critical issues connected with a limited colloidal stability and reduced entrapment efficiency of cargo molecules. This article analyzes the main features of the formation and fabrication techniques of liposome nanocarriers, with a special focus on the structure, parameters, and the critical factors that influence the development of a suitable and stable formulation. Recent developments and new methods for liposome preparation are also discussed, with the objective of updating the reader and providing future directions for research and development.

Preparation of liposomal nanocarrier by extruder to enhance tumor accumulation of paclitaxel

Despite the wide-spectrum and effective anti-cancer activity of paclitaxel (PTX), their low solubility and side effects are the main challenges in their clinical application. In this study, a model paclitaxel-encapsulated nanoliposome (NLips-PTX) carrier was synthesized to enhance PTX solubility and increase its passive accumulation at the tumor site. Soy lecithin and cholesterol at a 9:1 ratio were used to prepare the nano-sized liposomes through the thin-film hydration followed by extrusion technique. The prepared spherical NLips-PTX liposomes with an average size of about 150 nm and high uniformity were characterized by DLS and TEM. PTX load efficiency of NLips was determined at about 85% by HPLC. NLips-PTX also showed a therapeutic effect toward breast cancer cells (MCF-7) in a dose- and time-dependent manner via in vitro cellular uptake and a cytotoxicity study. This research indicates that extrusion is a simple and convenient method for nano-sizing and homogenising liposome suspension for potentially effective delivery of drug to target tumor sites.

The interaction mechanism between liposome and whey protein: Effect of liposomal vesicles concentration

The interaction mechanism between liposomes (Lips) and whey protein isolates (WPI) with different mass ratios was explored in this paper. After binding with different concentration of Lips, the changes in hydrophilic and hydrophobic regions of WPI were investigated with fluorescein isothiocyanate (FITC) and pyrene fluorescence probes. The spatial structure changes of WPI were further characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, and circular dichroism. The results indicated that the structure of WPI was changed due to binding with Lips in hydrophilic and hydrophobic groups. The binding process might result in the migration, recombination, and alignment of WPI and Lip groups. Moreover, the oil-water interfacial tension with WPI decreased from 9.20 mN/m to 3.29 mN/m upon increasing the Lip-to-WPI ratio. This work suggests that the physiochemical properties of Lip-WPI complexes could be manipulated by adjusting the Lip-to-WPI ratio. This study shed some light on the mechanism explanation of the WPI structural changes due to the interaction with Lips during food processing.

Polar Lipid Fraction E from Sulfolobus acidocaldarius and Dipalmitoylphosphatidylcholine Can Form Stable yet Thermo-Sensitive Tetraether/Diester Hybrid Archaeosomes with Controlled Release Capability

Archaeosomes have drawn increasing attention in recent years as novel nano-carriers for therapeutics. The main obstacle of using archaeosomes for therapeutics delivery has been the lack of an efficient method to trigger the release of entrapped content from the otherwise extremely stable structure. Our present study tackles this long-standing problem. We made hybrid archaeosomes composed of tetraether lipids, called the polar lipid fraction E (PLFE) isolated from the thermoacidophilic archaeon Sulfolobus acidocaldarius, and the synthetic diester lipid dipalmitoylphosphatidylcholine (DPPC). Differential polarized phase-modulation and steady-state fluorometry, confocal fluorescence microscopy, zeta potential (ZP) measurements, and biochemical assays were employed to characterize the physical properties and drug behaviors in PLFE/DPPC hybrid archaeosomes in the presence and absence of live cells. We found that PLFE lipids have an ordering effect on fluid DPPC liposomal membranes, which can slow down the release of entrapped drugs, while PLFE provides high negative charges on the outer surface of liposomes, which can increase vesicle stability against coalescence among liposomes or with cells. Furthermore, we found that the zeta potential in hybrid archaeosomes with 30 mol% PLFE and 70 mol% DPPC (designated as PLFE/DPPC(3:7) archaeosomes) undergoes an abrupt increase from −48 mV at 37 °C to −16 mV at 44 °C (termed the ZP transition), which we hypothesize results from DPPC domain melting and PLFE lipid ‘flip-flop’. The anticancer drug doxorubicin (DXO) can be readily incorporated into PLFE/DPPC(3:7) archaeosomes. The rate constant of DXO release from PLFE/DPPC(3:7) archaeosomes into Tris buffer exhibited a sharp increase (~2.5 times), when the temperature was raised from 37 to 42 °C, which is believed to result from the liposomal structural changes associated with the ZP transition. This thermo-induced sharp increase in drug release was not affected by serum proteins as a similar temperature dependence of drug release kinetics was observed in human blood serum. A 15-min pre-incubation of PLFE/DPPC(3:7) archaeosomal DXO with MCF-7 breast cancer cells at 42 °C caused a significant increase in the amount of DXO entering into the nuclei and a considerable increase in the cell’s cytotoxicity under the 37 °C growth temperature. Taken together, our data suggests that PLFE/DPPC(3:7) archaeosomes are stable yet potentially useful thermo-sensitive liposomes wherein the temperature range (from 37 to 42–44 °C) clinically used for mild hyperthermia treatment of tumors can be used to trigger drug release for medical interventions.

In vitro - in vivo relations for the parenteral liposomal formulation of Amphotericin B: A clinically relevant approach with PBPK modeling

In vitro release testing is a useful tool for the quality control of controlled release parenteral formulations, but in vitro release test conditions that reflect or are able to predict the in vivo performance are advantageous. Therefore, it is important to investigate the factors that could affect drug release from formulations and relate them to in vivo performance. In this study the effect of media composition including albumin presence, type of buffer and hydrodynamics on drug release were evaluated on a liposomal Amphotericin B formulation (Ambisome®). A physiologically based pharmacokinetic (PBPK) model was developed using plasma concentration profiles from healthy subjects, in order to investigate the impact of each variable from the in vitro release tests on the prediction of the in vivo performance. It was found that albumin presence was the most important factor for the release of Amphotericin B from Ambisome®; both hydrodynamics setups, coupled with the PBPK model, had comparable predictive ability for simulating in vivo plasma concentration profiles. The PBPK model was extrapolated to a hypothetical hypoalbuminaemic population and the Amphotericin B plasma concentration and its activity against fungal cells were simulated. Selected in vitro release tests for these controlled release parenteral formulations were able to predict the in vivo AmB exposure, and this PBPK driven approach to release test development could benefit development of such formulations.

Immunological and Toxicological Considerations for the Design of Liposomes

Liposomes hold great potential as gene and drug delivery vehicles due to their biocompatibility and modular properties, coupled with the major advantage of attenuating the risk of systemic toxicity from the encapsulated therapeutic agent. Decades of research have been dedicated to studying and optimizing liposomal formulations for a variety of medical applications, ranging from cancer therapeutics to analgesics. Some effort has also been made to elucidate the toxicities and immune responses that these drug formulations may elicit. Notably, intravenously injected liposomes can interact with plasma proteins, leading to opsonization, thereby altering the healthy cells they come into contact with during circulation and removal. Additionally, due to the pharmacokinetics of liposomes in circulation, drugs can end up sequestered in organs of the mononuclear phagocyte system, affecting liver and spleen function. Importantly, liposomal agents can also stimulate or suppress the immune system depending on their physiochemical properties, such as size, lipid composition, pegylation, and surface charge. Despite the surge in the clinical use of liposomal agents since 1995, there are still several drawbacks that limit their range of applications. This review presents a focused analysis of these limitations, with an emphasis on toxicity to healthy tissues and unfavorable immune responses, to shed light on key considerations that should be factored into the design and clinical use of liposomal formulations.

mTHPC-loaded extracellular vesicles outperform liposomal and free mTHPC formulations by an increased stability, drug delivery efficiency and cytotoxic effect in tridimensional model of tumors

Efficient photodynamic therapy with meta-tetra(hydroxyphenyl)chlorine requires the application of specific nanoformulations. mTHPC liposomal formulation (Foslip®) demonstrated favorable pharmacokinetics properties. However, rapid liposomes destruction in circulation and rapid mTHPC release impedes Foslip® applications. Alternatively, mTHPC nanovectorization using extracellular vesicles (EVs) could be an attractive option. EVs are naturally secreted by the organism to play a role in intercellular communication due to the capacity to transport proteins and nucleic acids. EVs also possess a natural ability to deliver therapeutic molecules into cancer cells. The aim of the present study was to evaluate photophysical and photobiological properties of mTHPC loaded in endothelial EVs as nanocarriers. We also studied efficiency of nanovectorisation on mTHPC distribution and PDT activity in multicellular tumor spheroids (MCTSs). MCTS is a nonvascularized in vitro 3D model of cells that mimics a similar microenvironment to in vivo situation. mTHPC-EVs were characterized by means of spectroscopic techniques, flow cytometry and nanoparticle tracking analysis. Compared with Foslip®, mTHPC-EVs are stable in murine plasma. Better mTHPC accumulation and penetration (up to 100 µm) in MCTS was observed for mTHPC-EVs compared with liposomal mTHPC. These factors could explain enhanced photodynamic activity of mTHPC-EVs compared with free and liposomal mTHPC. The light dose inducing 50% of cell death with mTHPC-EVs was 4 and 2.5-times lower than that of free and liposomal mTHPC. The obtained results demonstrate that EVs should be considered as perspective nanocarriers for mTHPC-mediated PDT.

Efficacy of neutral and negatively charged liposome-loaded gentamicin on planktonic bacteria and biofilm communities

We investigated the efficacy of liposomal gentamicin formulations of different surface charges against Pseudomonas aeruginosa and Klebsiella oxytoca. The liposomal gentamicin formulations were prepared by the dehydration-rehydration method, and their sizes and zeta potential were measured. Gentamicin encapsulation efficiency inside the liposomal formulations was determined by microbiologic assay, and stability of the formulations in biologic fluid was evaluated for a period of 48 h. The minimum inhibitory concentration and the minimum bactericidal concentration were determined, and the in vitro time kill studies of the free form of gentamicin and liposomal gentamicin formulations were performed. The activities of liposomal gentamicin in preventing and reducing biofilm-forming P. aeruginosa and K. oxytoca were compared to those of free antibiotic. The sizes of the liposomal formulations ranged from 625 to 806.6 nm in diameter, with the zeta potential ranging from -0.22 to -31.7 mV. Gentamicin encapsulation efficiency inside the liposomal formulation ranged from 1.8% to 43.6%. The liposomes retained >60% of their gentamicin content during the 48 h time period. The minimum inhibitory concentration of neutral formulation was lower than that of free gentamicin (0.25 versus 1 mg/L for P. aeruginosa and 0.5 versus 1 mg/L for K. oxytoca). The negatively charged formulation exhibited the same bacteriostatic concentration as that of free gentamicin. The minimum bactericidal concentration of neutral liposomes on planktonic bacterial culture was twofold lower than that of free gentamicin, whereas the negatively charged formulations were comparable to free gentamicin. The killing time curve values for the neutral negatively charged formulation against planktonic P. aeruginosa and K. oxytoca were better than those of free gentamicin. Furthermore, liposomal formulations prevent the biofilm-formation ability of these strains better than free gentamicin. In summary, liposomal formulations could be an effective lipid nanoparticle to combat acute infections where planktonic bacteria are predominant.

Determination of the Subcellular Distribution of Liposomes Using Confocal Microscopy

It is being increasingly recognized that therapeutics need to be delivered to specific organelle targets within cells. Liposomes are versatile lipid-based drug delivery vehicles that can be surface-modified to deliver the loaded cargo to specific subcellular locations within the cell. Hence, the development of such technology requires a means of measuring the subcellular distribution possibly by utilizing imaging techniques that can visualize and quantitate the extent of this subcellular localization. The apparent increase of resolution along the Z-axis offered by confocal microscopy makes this technique suitable for such studies. In this chapter, we describe the application of confocal laser scanning microscopy (CLSM) to determine the subcellular distribution of fluorescently labeled mitochondriotropic liposomes.

Charge effect of a liposomal delivery system encapsulating simvastatin to treat experimental ischemic stroke in rats

BACKGROUND AND AIMS

Although the beneficial effects of statins on stroke have been widely demonstrated both in experimental studies and in clinical trials, the aim of this study is to prepare and characterize a new liposomal delivery system that encapsulates simvastatin to improve its delivery into the brain.

MATERIALS AND METHODS

In order to select the optimal liposome lipid composition with the highest capacity to reach the brain, male Wistar rats were submitted to sham or transitory middle cerebral arterial occlusion (MCAOt) surgery and treated (intravenous [IV]) with fluorescent-labeled liposomes with different net surface charges. Ninety minutes after the administration of liposomes, the brain, blood, liver, lungs, spleen, and kidneys were evaluated ex vivo using the Xenogen IVIS(®) Spectrum imaging system to detect the load of fluorescent liposomes. In a second substudy, simvastatin was assessed upon reaching the brain, comparing free and encapsulated simvastatin (IV) administration. For this purpose, simvastatin levels in brain homogenates from sham or MCAOt rats at 2 hours or 4 hours after receiving the treatment were detected through ultra-high-protein liquid chromatography.

RESULTS

Whereas positively charged liposomes were not detected in brain or plasma 90 minutes after their administration, neutral and negatively charged liposomes were able to reach the brain and accumulate specifically in the infarcted area. Moreover, neutral liposomes exhibited higher bioavailability in plasma 4 hours after being administered. The detection of simvastatin by ultra-high-protein liquid chromatography confirmed its ability to cross the blood-brain barrier, when administered either as a free drug or encapsulated into liposomes.

CONCLUSION

This study confirms that liposome charge is critical to promote its accumulation in the brain infarct after MCAOt. Furthermore, simvastatin can be delivered after being encapsulated. Thus, simvastatin encapsulation might be a promising strategy to ensure that the drug reaches the brain, while increasing its bioavailability and reducing possible side effects.

The influence of liposomal formulation on the incorporation and retention of PNA oligomers

Liposomal formulations composed of phospholipids with different unsaturation degrees, head groups and at different cholesterol content have been tested for the encapsulation of Peptide Nucleic Acid (PNA) oligomers. The best loading capability (177μg, ER%=87.2) was obtained for pure liposomes of phosphatidylglycerol (DOPG) with negatively charged head group. The insertion of a 10-20% of cholesterol in DOPG based liposomes provides a slight decrease (∼160μg) of the PNA loading. On the other hand, the cholesterol addition (20-30%) slows down the PNA's release (∼27%) in fetal bovine serum from the liposomal formulation. Based on the encapsulation and the release properties, PEGylated DOPG liposomes with a percentage of cholesterol of 10-20% are the optimal formulation for the loading of PNA-a210.

Novel stable dendrimersome formulation for safe bioimaging applications

Dendrimersomes are nanosized vesicles constituted by amphiphilic Janus dendrimers (JDs), which have been recently proposed as innovative nanocarriers for biomedical applications. Recently, we have demonstrated that dendrimersomes self-assembled from (3,5)12G1-PE-BMPA-G2-(OH)8 dendrimers can be successfully loaded with hydrophilic and amphiphilic imaging contrast agents. Here, we present two newly synthesized low generation isomeric JDs: JDG0G1(3,5) and JDG0G1(3,4). Though less branched than the above-cited dendrimers, they retain the ability to form self-assembled, almost monodisperse vesicular nanoparticles. This contribution reports on the characterization of such nanovesicles loaded with the clinically approved MRI probe Gadoteridol and the comparison with the related nanoparticles assembled from more branched dendrimers. Special emphasis was given to the in vitro stability test of the systems in biologically relevant media, complemented by preliminary in vivo data about blood circulation lifetime collected from healthy mice. The results point to very promising safety and stability profiles of the nanovesicles, in particular for those made of JDG0G1(3,5), whose spontaneous self-organization in water gives rise to a homogeneous suspension. Importantly, the blood lifetimes of these systems are comparable to those of standard liposomes. By virtue of the reported results, the herein presented nanovesicles augur well for future use in a variety of biomedical applications.

Intracellular trafficking of hybrid gene delivery vectors

Viral and non-viral gene delivery vectors are in development for human gene therapy, but both exhibit disadvantages such as inadequate efficiency, lack of cell-specific targeting or safety concerns. We have recently reported the design of hybrid delivery vectors combining retrovirus-like particles with synthetic polymers or lipids that are efficient, provide sustained gene expression and are more stable compared to native retroviruses. To guide further development of this promising class of gene delivery vectors, we have investigated their mechanisms of intracellular trafficking. Moloney murine leukemia virus-like particles (M-VLPs) were complexed with chitosan (Chi) or liposomes (Lip) comprising DOTAP, DOPE and cholesterol to form the hybrid vectors (Chi/M-VLPs and Lip/M-VLPs, respectively). Transfection efficiency and cellular internalization of the vectors were quantified in the presence of a panel of inhibitors of various endocytic pathways. Intracellular transport and trafficking kinetics of the hybrid vectors were dependent on the synthetic component and used a combination of clathrin- and caveolar-dependent endocytosis and macropinocytosis. Chi/M-VLPs were slower to transfect compared to Lip/M-VLPs due to the delayed detachment of the synthetic component. The synthetic component of hybrid gene delivery vectors plays a significant role in their cellular interactions and processing and is a key parameter for the design of more efficient gene delivery vehicles.

Nanomedicine for treating spinal cord injury

Spinal cord injury results in significant mortality and morbidity, lifestyle changes, and difficult rehabilitation. Treatment of spinal cord injury is challenging because the spinal cord is both complex to treat acutely and difficult to regenerate. Nanomaterials can be used to provide effective treatments; their unique properties can facilitate drug delivery to the injury site, enact as neuroprotective agents, or provide platforms to stimulate regrowth of damaged tissues. We review recent uses of nanomaterials including nanowires, micelles, nanoparticles, liposomes, and carbon-based nanomaterials for neuroprotection in the acute phase. We also review the design and neural regenerative application of electrospun scaffolds, conduits, and self-assembling peptide scaffolds.

Formulation of liposomes gels of paeonol for transdermal drug delivery by Box-Behnken statistical design

The aim of this study was to design and optimize a transdermal liposomes gel formulation for paeonol (PAE). A three-factor, three-level Box-Behnken design was used to derive a second-order polynomial equation to construct three-dimensional (3-D) contour plots for prediction of responses. Independent variables studied were the DC-Chol concentration (X₁), molar ratio of lipid/drug (X₂), and the polymer concentration (X₃), and the levels of each factor were low, medium, and high. The dependent variables studied were the encapsulation efficiency (%EE) of PAE (Y₁), flux of PAE (Y₂), and viscosity of the gels (Y₃). Response surface plots were drawn and statistical validity of the polynomials was established to find the compositions of optimized formulation, which was evaluated using the Franz diffusion cell. The %EE of PAE increased proportionally with the molar ratio of lipid/drug, but decreased with polymer concentration, whereas the flux of PAE increased proportionally with polymer concentration and the DC-Chol concentration. The viscosity of gels increased with the polymer concentration. Gels showed a non-Fickian diffusion release mechanism for PAE, and the in vitro release profiles were fit for Higuchi's order model. The design demonstrated the role of the derived polynomial equation and 3-D contour plots in predicting the values of dependent variables for the preparation and optimization of gel formulation for transdermal drug release.

Design and characterization of targeted ultrasound microbubbles for diagnostic use

Targeted ultrasound (US) contrast agents represent, because of their size (1 to 5 μm), a unique class of diagnostic imaging agents enabling true vascular imaging of conditions like inflammation and tumor angiogenesis. The objective of this study was to develop technology for preparing targeted microbubbles with binding and acoustic properties compatible with diagnostic use. Phosphatidylcholine (PC) was shown to represent the most favorable wall material. Various thiolated peptide binders were effectively conjugated to PC-based microbubbles containing maleimide functionalized lipids (95:5) without the need for biotin-streptavidin or antibody technology. By optimizing the technology, specific targeting of the inflammatory target E-selectin and the angiogenic target VEGFR2 in the presence of 100% serum was achieved. Increased phospholipid chain length from 18 carbons to 22 carbons improved the stability of the microbubbles during US exposure, without compromising binding or acoustic properties.

Role of surface charge and oxidative stress in cytotoxicity of organic monolayer-coated silicon nanoparticles towards macrophage NR8383 cells

Background

Surface charge and oxidative stress are often hypothesized to be important factors in cytotoxicity of nanoparticles. However, the role of these factors is not well understood. Hence, the aim of this study was to systematically investigate the role of surface charge, oxidative stress and possible involvement of mitochondria in the production of intracellular reactive oxygen species (ROS) upon exposure of rat macrophage NR8383 cells to silicon nanoparticles. For this aim highly monodisperse (size 1.6 ± 0.2 nm) and well-characterized Si core nanoparticles (Si NP) were used with a surface charge that depends on the specific covalently bound organic monolayers: positively charged Si NP-NH₂, neutral Si NP-N₃ and negatively charged Si NP-COOH.

Results

Positively charged Si NP-NH₂ proved to be more cytotoxic in terms of reducing mitochondrial metabolic activity and effects on phagocytosis than neutral Si NP-N₃, while negatively charged Si NP-COOH showed very little or no cytotoxicity. Si NP-NH₂ produced the highest level of intracellular ROS, followed by Si NP-N₃ and Si NP-COOH; the latter did not induce any intracellular ROS production. A similar trend in ROS production was observed in incubations with an isolated mitochondrial fraction from rat liver tissue in the presence of Si NP. Finally, vitamin E and vitamin C induced protection against the cytotoxicity of the Si NP-NH₂ and Si NP-N₃, corroborating the role of oxidative stress in the mechanism underlying the cytotoxicity of these Si NP.

Conclusion

Surface charge of Si-core nanoparticles plays an important role in determining their cytotoxicity. Production of intracellular ROS, with probable involvement of mitochondria, is an important mechanism for this cytotoxicity.

Architectonics of phage-liposome nanowebs as optimized photosensitizer vehicles for photodynamic cancer therapy

Filamentous M13 phage can be engineered to display cancer cell-targeting or tumor-homing peptides through phage display. It would be highly desirable if the tumor-targeting phage can also carry anticancer drugs to deliver them to the cancer cells. We studied the evolution of structures of the complexes between anionic filamentous M13 phage and cationic serum-stable liposomes that encapsulate the monomeric photosensitizer zinc naphthalocyanine. At specific phage-liposome ratios, multiple phage nanofibers and liposomes are interwoven into a "nanoweb." The chemical and biological properties of the phage-liposome nanoweb were evaluated for possible application in drug delivery. This study highlights the ability of phage-liposome nanowebs to serve as efficient carriers in the transport of photosensitizers to cancer cells.

Liposome Opsonization

Adsorption of serum proteins to the liposomal surface plays a critical role in the clearance of liposomes from the blood circulation. In this review, we will discuss the role of the liposomal opsonins proposed so far in liposome clearance. Additional, related topics that will be addressed are the cell-surface receptors that might be involved in liposome elimination from the blood compartment and the effect of poly(ethylene glycol) (PEG) modification on prevention of liposome opsonization.

Co-encapsulation of gallium with gentamicin in liposomes enhances antimicrobial activity of gentamicin against Pseudomonas aeruginosa

OBJECTIVES

The aim of this study was to enhance the antimicrobial efficacy of a liposomal gentamicin formulation with gallium metal (Lipo-Ga-GEN) against clinical isolates of Pseudomonas aeruginosa.

METHODS

Sputum isolates of P. aeruginosa from cystic fibrosis patients were used to determine the MIC and MBC of Lipo-Ga-GEN. P. aeruginosa biofilms were formed and used to compare the minimum biofilm eradication concentration of the conventional drugs with that of Lipo-Ga-GEN. Quorum sensing (QS) molecule reduction of P. aeruginosa was determined by monitoring N-acyl homoserine lactone production using Agrobacterium tumefaciens reporter strain (A136). Viability of the cultured human lung epithelial cells (A549) was determined by Trypan Blue assay in order to assess Ga toxicity.

RESULTS

MIC and MBC values indicated that gentamicin was more effective against a highly resistant strain of P. aeruginosa (PA-48913) when delivered as a Lipo-Ga-GEN formulation (256 mg/L free gentamicin versus 2 mg/L Lipo-Ga-GEN). Lipo-Ga-GEN was the only formulation that completely eradicated biofilms and blocked QS molecules at a very low concentration (0.94 mg/L gentamicin). The decrease in cell viability was less in A549 cells exposed to Lipo-Ga, suggesting that encapsulated Ga is safer.

CONCLUSIONS

The results clearly indicate that the Lipo-Ga-GEN formulation is more effective than gentamicin alone in eradicating antibiotic-resistant P. aeruginosa isolates growing in a planktonic or biofilm community.

Analysis of interaction between dendriplexes and bovine serum albumin

Dendrimers are new nanotechnological carriers for gene delivery. Short oligodeoxynucleotides (ODNs) are a new class of antisense therapy drugs for cancer and infectious or metabolic diseases. The interactions between short oligodeoxynucleotides (GEM91, CTCTCGCACCCATCTCTCTCCTTCT; SREV, TCGTCGCTGTCTCCGCTTCTTCCTGCCA; unlabeled or fluorescein-labeled), novel water-soluble carbosilane dendrimers, and bovine serum albumin were studied by fluorescence and gel electrophoresis. The molar ratios of the dendrimer/ODN dendriplexes ranged from 4 to 7. The efficiency of formation and stability of the dendriplexes depended on electrostatic interactions between the dendrimer and the ODNs. Dendriplex formation significantly decreased the interactions between ODNs and albumin. Thus, the formation of dendriplexes between carbosilane dendrimers and ODNs may improve ODN delivery.

Water-soluble carbosilane dendrimers protect phosphorothioate oligonucleotides from binding to serum proteins

Treatment of dendriplexes formed between water-soluble carbosilane dendrimers and phosphorothioate oligodeoxynucleotides (ODN) with the anionic detergent sodium dodecyl sulfate disrupted the complexes indicating that the nature of the union in such dendriplexes is merely electrostatic. However, dendriplexes were not dissociated by serum proteins like bovine or human serum albumins, as assessed by gel electrophoresis and fluorescence experiments. This would imply a dendrimer-mediated protective effect able to prevent ODN interactions with serum proteins and additionally could translate into a reduction of the ODN doses needed to achieve the biological effects. The employment of carbosilane dendrimers as carriers may solve the problem of ODN kidnapping by plasmatic proteins as a key drawback for therapeutics involving ODNs. As examples, transfection processes on normal primary peripheral blood cells and diagnosis of HIV infection in the presence of serum have been assayed.

The use of immunoliposome for nutrient target regulation (a review)

Although research on the role of genetically engineered antibodies and liposomes in the immunology or the nutrition field is extensive, there is no case for immunoliposome to nutrient target regulation. It is known that liposomes are spherical particles that encapsulate a fraction of the solvent, in which they freely diffuse (float) into their interior. Therefore, identification of immunoliposomes in hypothalamic site or intestinal epithelial cells that are differentially regulated by liposomes encapsulating nutrients or drugs will be an important step toward understanding the role of immunoliposomes in nutrition regulation progression and ingredient stability. Consequently, a useful model (immunoliposomal nutrient delivery system, ILNDS) of nutrient target regulation via immunoliposomes is designed to regulate the endocrine system effectively. This review focuses on antibody libraries' construction, display and selection, a brief introduction of immunoliposome, and how to use ILNDS for nutrient target regulation.

Strategies for DNA vaccine delivery

Strategies for gene delivery comprise a diverse range of live and synthetic approaches; DNA delivery for the purposes of immunisation in turn comprises a large part of this research. This review mainly discusses synthetic systems for application in the delivery of plasmid DNA vaccines, outlining polylactide-co-glycolide, liposome, chitosan and complex combination delivery systems. Areas of promise for DNA vaccine candidates include immune modulation of allergic responses and veterinarian application. The potential for realistic consideration of DNA vaccines as an alternative to existing approaches is dependent on the development of efficient DNA vaccine vectors and improved systems for DNA vaccine delivery. DNA vaccine technology may yet prove to be an important asset in an environment where there is a critical need for therapeutic and prophylactic strategies to combat a wide range of disease states.

In vitro adsorption of plasma proteins onto the surface (charges) modified-submicron emulsions for intravenous administration

Surface (charge) modified submicron emulsions (cationic and anionic) were prepared following the well established combined emulsification techniques and characterized for their droplet size distribution and surface charge. The effect of these emulsions on in vitro adsorption of plasma proteins was investigated by means of two dimensional polyacrylamide gel electrophoresis (2D PAGE). The presence of poloxamer 188 in tested emulsions effectively eliminated the adsorption of the larger proteins like immunoglobulins, fibrinogen, etc. However, depending on the type of surface charges, the smaller proteins such as apolipoproteins and albumin were almost completely adsorbed onto the submicron emulsions. Indeed, when compared to marketed lipofundin MCT 10%-and deoxycholic acid-based anionic emulsions, the adsorption of apolipoprotein, especially apoA-1, was approximately three times more on stearylamine-and oleylamine-based cationic emulsions and oleic acid-based anionic emulsions. In addition, the ratio between the apoA-1 and apoA-IV was found to be 1 for lipofundin MCT 10% whereas it was about 0.26 for deoxycholic acid-based anionic emulsion and above 5 for oleic acid-based anionic emulsions and cationic emulsions. This indicates that emulsions having similar surface/interfacial charge imparted by different anion-forming stabilizers (oleic or deoxycholic acids) exhibited markedly different protein adsorption patterns.

Etoposide-incorporated tripalmitin nanoparticles with different surface charge: formulation, characterization, radiolabeling, and biodistribution studies

Etoposide-incorporated tripalmitin nanoparticles with negative (ETN) and positive charge (ETP) were prepared by melt emulsification and high-pressure homogenization techniques. Spray drying of nanoparticles led to free flowing powder with excellent redispersibility. The nanoparticles were characterized by size analysis, zeta potential measurements, and scanning electron microscopy. The mean diameter of ETN and ETP nanoparticles was 391 nm and 362 nm, respectively, and the entrapment efficiency was more than 96%. Radiolabeling of etoposide and nanoparticles was performed with Technetium-99m (99mTc) with high labeling efficiency and in vitro stability. The determination of binding affinity of 99mTc-labeled complexes by diethylene triamine penta acetic acid (DTPA) and cysteine challenge test confirmed low transchelation of 99mTc-labeled complexes and high in vitro stability. Pharmacokinetic data of radiolabeled etoposide, ETN, and ETP nanoparticles in rats reveal that positively charged nanoparticles had high blood concentrations and prolonged blood residence time. Biodistribution studies of 99mTc-labeled complexes were performed after intravenous administration in mice. Both ETN and ETP nanoparticles showed significantly lower uptake by organs of the reticuloendothelial system such as liver and spleen (P < .001) compared with etoposide. The ETP nanoparticles showed a relatively high distribution to bone and brain (14-fold higher than etoposide and ETN at 4 hours postinjection) than ETN nanoparticles. The ETP nanoparticles with long circulating property could be a beneficial delivery system for targeting to tumors by Enhanced Permeability and Retention effect and to brain.

Interaction of the water-soluble protein aprotinin with liposomes: gel-filtration, turbidity studies, and 31P NMR studies

The interactions of a water-soluble nonmembrane protein aprotinin with multilamellar vesicles (MLV) and small unilamellar vesicles (SUV) from soybean phospholipids were studied using Sephadex G-75 gel chromatography combined with different methods of the analysis of the eluate fractions (fluorescence, light-scattering, turbidity; 31P NMR spectroscopy). The composition of the liposomes mainly containing soybean phosphatidylcholine (PC) was varied by the addition of phosphatidylethanolamine (PE), phosphatidylinositol (PI) and lyso-phosphatidylcholine (lyso-PC). To evaluate the lipid-protein interactions, the amount of aprotinin in the MLV-aprotinin complexes was determined. Lipid-protein interactions were found to strongly depend on the liposome composition, medium pH and ionic strength. These dependencies point to the electrostatic nature of the aprotinin-lipid interactions. 31P NMR spectroscopy of the MLV-aprotinin complexes indicated that aprotinin influences the phospholipid structure in MLV at pH 3.0. In the case of PC:PE:PI and PC:PE:PI:lyso-PC vesicles, aprotinin induced liposome aggregation and a lamellar-to-isotropic phase transition of the phospholipids.