Effect of Molecular Architecture on Cell Interactions and Stealth Properties of PEG

Four-Component Statistical Copolymers by RAFT Polymerization

This manuscript serves as the starting point for in-depth research of multicomponent, statistical, methacrylate-based copolymers that potentially mimic the behavior of proteins in aqueous solutions. These synthetic macromolecules are composed of specially chosen comonomers: methacrylic acid (MAA), oligoethylene glycol methyl ether methacrylate (OEGMA475), 2-(dimethylamino)ethyl methacrylate (DMAEMA) and benzyl methacrylate (BzMA). Monomer choice was based on factors such as the chemical nature of pendant functional groups, the polyelectrolyte/polyampholyte and amphiphilic character and the overall hydrophobic-hydrophilic balance (HLB) of the obtained quaterpolymers. Their synthesis was achieved via a one-pot reversible addition fragmentation chain transfer (RAFT) polymerization in two distinct compositions and molecular architectures, linear and hyperbranched, respectively, in order to explore the effects of macromolecular topology. The resulting statistical quaterpolymers were characterized via 1H-NMR and ATR-FTIR spectroscopies. Their behavior in aqueous solutions was studied by dynamic (DLS) and electrophoretic light scattering (ELS) and fluorescence spectroscopy (FS), producing vital information concerning their self-assembly and the structure of the formed aggregates. The physicochemical studies were extended by tuning parameters such as the solution pH and ionic strength. Finally, the quaterpolymer behavior in FBS/PBS solutions was investigated to test their colloid stability and biocompatibility in an in vivo-mimicking, biological fluid environment.

Gout therapeutics and drug delivery

Gout is a common inflammatory arthritis caused by persistently elevated uric acid levels. With the improvement of people's living standards, the consumption of processed food and the widespread use of drugs that induce elevated uric acid, gout rates are increasing, seriously affecting the human quality of life, and becoming a burden to health systems worldwide. Since the pathological mechanism of gout has been elucidated, there are relatively effective drug treatments in clinical practice. However, due to (bio)pharmaceutical shortcomings of these drugs, such as poor chemical stability and limited ability to target the pathophysiological pathways, traditional drug treatment strategies show low efficacy and safety. In this scenario, drug delivery systems (DDS) design that overcome these drawbacks is urgently called for. In this review, we initially describe the pathological features, the therapeutic targets, and the drugs currently in clinical use and under investigation to treat gout. We also comprehensively summarize recent research efforts utilizing lipid, polymeric and inorganic carriers to develop advanced DDS for improved gout management and therapy.

Molecular Sieving with PEGylated Dendron-Protein Conjugates

A series of generation 3-5 dendrons based on a bis(2,2-hydroxymethylpropionic acid) (bis-MPA) scaffold bearing three respective lengths of linear poly(ethylene glycol) at their periphery and a dibenzocyclooctyne unit at their core was prepared. These dendrons were appended to the surface of azide-decorated α-chymotrypsin (α-CT) via strain-promoted azide-alkyne cycloaddition to yield a library of dendron-protein conjugates. These conjugates were characterized by FT-IR and NMR spectroscopy and were imaged using cryo-electron microscopy. The activity of the PEGylated α-CT-dendron conjugates was investigated using a small molecule (benzoyl-l-tyrosine p-nitroanilide) as well as different proteins of different sizes and crystallinities (casein and bovine serum albumin) as substrates. It was found that the activity of the conjugates toward the small molecule was largely retained, while the activity toward the proteins was significantly diminished. Furthermore, the results indicate that for most of the conjugates the PEG length had a more pronounced impact on enzyme activity than the dendron generation. Overall, the highest sieving ratios were found for α-CT-dendron conjugates decorated with G3-PEG2000, G4-PEG2000, and G5-PEG1000, with the latter two structures offering the best combination of sieving ratio and small molecule activity.

An injectable PEG-like conjugate forms a subcutaneous depot and enables sustained delivery of a peptide drug

Many biologics have a short plasma half-life, and their conjugation to polyethylene glycol (PEG) is commonly used to solve this problem. However, the improvement in the plasma half-life of PEGylated drugs' is at an asymptote because the development of branched PEG has only had a modest impact on pharmacokinetics and pharmacodynamics. Here, we developed an injectable PEG-like conjugate that forms a subcutaneous depot for the sustained delivery of biologics. The PEG-like conjugate consists of poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) conjugated to exendin, a peptide drug used in the clinic to treat type 2 diabetes. The depot-forming exendin-POEGMA conjugate showed greater efficacy than a PEG conjugate of exendin as well as Bydureon, a clinically approved sustained-release formulation of exendin. The injectable depot-forming exendin-POEGMA conjugate did not elicit an immune response against the polymer, so that it remained effective and safe for long-term management of type 2 diabetes upon chronic administration. In contrast, the PEG conjugate induced an anti-PEG immune response, leading to early clearance and loss of efficacy upon repeat dosing. The exendin-POEGMA depot also showed superior long-term efficacy compared to Bydureon. Collectively, these results suggest that an injectable POEGMA conjugate of biologic drugs that forms a drug depot under the skin, providing favorable pharmacokinetic properties and sustained efficacy while remaining non-immunogenic, offers significant advantages over other commonly used drug delivery technologies.

Recent advances in long-acting drug delivery systems for anticancer drug

The use of systemic anticancer chemotherapy is intrinsically limited by its toxicity. Whether dealing with small molecules or biopharmaceuticals, after systemic administration, small doses fail to reach effective intratumoral concentrations, while high doses with significant tumor inhibition effects may also drive the death of healthy cells, endangering the patients. Therefore, strategies based on drug delivery systems (DDSs) for avoiding the systemic toxicity have been designed. Due to their ability to protect drugs from early elimination and control drug release, DDSs can foster tumor exposure to anticancer therapeutics by extending their circulation time or steadily releasing drugs into the tumor sites. However, approval of tailored DDSs systems for clinical use is minimal as the safety and the in vivo activity still need to be ameliorated by manipulating their physicochemical characteristics. During the last few years, several strategies have been described to improve their safety, stability, and fine-tune pharmaceuticals release kinetics. Herein, we reviewed the main DDSs, namely polymeric conjugates, nano or microparticles, hydrogels, and microneedles, explored for long-acting anticancer treatments, highlighting recently proposed modifications and their potential advantages for different anticancer therapies. Additionally, important limitations of long-acting anticancer therapies and future technology directions were also covered.

Curcumin-Loaded PnBA-b-POEGA Nanoformulations: A Study of Drug-Polymer Interactions and Release Behavior

The current study focuses on the development of innovative and highly-stable curcumin (CUR)-based therapeutics by encapsulating CUR in biocompatible poly(n-butyl acrylate)-block-poly(oligo(ethylene glycol) methyl ether acrylate) (PnBA-b-POEGA) micelles. State-of-the-art methods were used to investigate the encapsulation of CUR in PnBA-b-POEGA micelles and the potential of ultrasound to enhance the release of encapsulated CUR. Dynamic light scattering (DLS), attenuated total reflection Fourier transform infrared (ATR-FTIR), and ultraviolet-visible (UV-Vis) spectroscopies confirmed the successful encapsulation of CUR within the hydrophobic domains of the copolymers, resulting in the formation of distinct and robust drug/polymer nanostructures. The exceptional stability of the CUR-loaded PnBA-b-POEGA nanocarriers over a period of 210 days was also demonstrated by proton nuclear magnetic resonance (¹H-NMR) spectroscopy studies. A comprehensive 2D NMR characterization of the CUR-loaded nanocarriers authenticated the presence of CUR within the micelles, and unveiled the intricate nature of the drug-polymer intermolecular interactions. The UV-Vis results also indicated high encapsulation efficiency values for the CUR-loaded nanocarriers and revealed a significant influence of ultrasound on the release profile of CUR. The present research provides new understanding of the encapsulation and release mechanisms of CUR within biocompatible diblock copolymers and has significant implications for the advancement of safe and effective CUR-based therapeutics.

Protein charge parameters that influence stability and cellular internalization of polyelectrolyte complex micelles

Proteins are an important class of biologics, but there are several recurring challenges to address when designing protein-based therapeutics. These challenges include: the propensity of proteins to aggregate during formulation, relatively low loading in traditional hydrophobic delivery vehicles, and inefficient cellular uptake. This last criterion is particularly challenging for anionic proteins as they cannot cross the anionic plasma membrane. Here we investigated the complex coacervation of anionic proteins with a block copolymer of opposite charge to form polyelectrolyte complex (PEC) micelles for use as a protein delivery vehicle. Using genetically modified variants of the model protein green fluorescent protein (GFP), we evaluated the role of protein charge and charge localization in the formation and stability of PEC micelles. A neutral-cationic block copolymer, poly(oligoethylene glycol methacrylate-block-quaternized 4-vinylpyridine), POEGMA₇₉-b-qP4VP₁₇₅, was prepared via RAFT polymerization for complexation and microphase separation with the panel of engineered anionic GFPs. We found that isotropically supercharged proteins formed micelles at higher ionic strength relative to protein variants with charge localized to a polypeptide tag. We then studied GFP delivery by PEC micelles and found that they effectively delivered the protein cargo to mammalian cells. However, cellular delivery varied as a function of protein charge and charge distribution and we found an inverse relationship between the PEC micelle critical salt concentration and delivery efficiency. This model system has highlighted the potential of polyelectrolyte complexes to deliver anionic proteins intracellularly. Using this model system, we have identified requirements for the formation of PEC micelles that are stable at physiological ionic strength and that smaller protein-polyelectrolyte complexes effectively deliver proteins to Jurkat cells.

Nanogap-containing thermo-plasmonic nano-heaters for amplified photo-triggered tumor ablation at low laser power density

Herein, nanogap amplified plasmonic heat-generators are fabricated by decorating Pt nanodots on gold nanospheres (GNSs@Pt@mPEG) by maintaining strategic nano-gaps (1-2 nm) and studied precisely for plasmonic photothermal therapy (PPTT) of colon cancer by passive tumor targeting. The surface modification of GNSs@Pt with poly(ethylene glycol) methyl ether thiol (mPEG) increases their accumulation in tumor cells and hence the GNSs@Pt@mPEG stay at the tumor site for a longer time. The nanogap amplified GNSs@Pt@mPEG (O.D. = 4.0) generated high plasmonic photothermal hyperthermia and utilized a low NIR power density (0.36 W cm^-2) for the elimination of tumor cells in only 150 s of irradiation time and shows excellent colloidal and photo-stability. The predominant distribution of GNSs@Pt@mPEG caused effective tumor cell death and promoted uniform treatment on tumor sites. In vivo studies demonstrated that the GNSs@Pt@mPEG have very low toxicity, high biocompatibility, and thermal stability, stay longer at the tumor site, induce tumor cell death without side effects, and show significantly less uptake in other organs except for the spleen. The significant accumulations and longer stay suggested that they are favorable for tumor passive uptake and the possibility of enhanced PPTT after intravenous administration. The nano-particles were stable up to O.D. 200 and have at least 12 months shelf-life without losing colloidal stability or photothermal efficacy. These findings lay the groundwork for using GNSs@Pt@mPEG as a NIR light-responsive PPTT agent and demonstrated their potential for further use in clinical applications.

Polyethylene Glycol-Like Brush Polymer Conjugate of a Protein Drug Does Not Induce an Antipolymer Immune Response and Has Enhanced Pharmacokinetics than Its Polyethylene Glycol Counterpart

Protein therapeutics, except for antibodies, have a short plasma half-life and poor stability in circulation. Covalent coupling of polyethylene glycol (PEG) to protein drugs addresses this limitation. However, unlike previously thought, PEG is immunogenic. In addition to induced PEG antibodies, ≈70% of the US population has pre-existing anti-PEG antibodies. Both induced and preexisting anti-PEG antibodies result in accelerated drug clearance, reduced clinical efficacy, and severe hypersensitivity reactions that have limited the clinical utility of uricase, an enzyme drug for treatment for refractory gout that is decorated with a PEG corona. Here, the authors synthesize a poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) conjugate of uricase that decorates the protein with multiple polymer chains to create a corona to solve these problems. The resulting uricase-POEGMA is well-defined, has high bioactivity, and outperforms its PEG counterparts in its pharmacokinetics (PK). Furthermore, the conjugate does not induce anti-POEGMA antibodies and is not recognized by anti-PEG antibodies. These findings suggest that POEGMA conjugation may provide a solution to the immunogenicity and antigenicity limitations of PEG while improving upon its PK benefits. These results transcend uricase and can be applied to other PEGylated therapeutics and the broader class of biologics with suboptimal PK.

PEG-Like Brush Polymer Conjugate of RNA Aptamer That Shows Reversible Anticoagulant Activity and Minimal Immune Response

Ribonucleic acid (RNA) therapeutics are an emerging class of drugs. RNA aptamers are of significant therapeutic and clinical interest because their activity can be easily reversed in vivo-a useful feature that is difficult to achieve using other therapeutic modalities. Despite their therapeutic promise, RNA aptamers are limited by their poor blood circulation. The attachment of polyethylene glycol (PEG) to RNA aptamers addresses this limitation. However, an RNA aptamer-PEG conjugate that is a reversible anticoagulant fails in a clinical trial due to the reactivity of the conjugate with pre-existing PEG antibodies and has cast a pall over PEGylation of aptamers and other biologics, despite its long history of utility in drug delivery. Here, PEG antibody-reactivity of this RNA aptamer is eliminated by conjugating it to a next-generation PEG-like brush polymer-poly[(oligoethylene glycol) methyl ether methacrylate)] (POEGMA). The conjugate retained the drug's therapeutic action and the ability to be easily reversed. Importantly, this conjugate does not bind pre-existing PEG antibodies that are prevalent in humans and does not induce a humoral immune response against the polymer itself in mice. These findings suggest a path to rescuing the PEGylation of RNA therapeutics and vaccines from the deleterious side-effects of PEG.

Confinements of Thermoresponsive Dendronized Polymers to Proteins

Crowding environment created by host polymers plays crucial roles in manipulating interactions with proteins and modulating their bioactivity. Here, we report our investigation on interactions between polymers and proteins in...

PEGylation of Guanidinium and Indole Bearing Poly(methacrylamide)s - Biocompatible Terpolymers for pDNA Delivery

This study describes the first example for shielding of a high performing terpolymer that consists of N-(2-hydroxypropyl)methacrylamide (HPMA), N-(3-guanidinopropyl)methacrylamide (GPMA), and N-(2-indolethyl)methacrylamide monomers (IEMA) by block copolymerization of a polyethylene glycol derivative - poly(nona(ethylene glycol)methyl ether methacrylate) (P(MEO₉ MA)) via reversible addition-fragmentation chain transfer (RAFT) polymerization. The molecular weight of P(MEO₉ MA) is varied from 3 to 40 kg mol^-1 while the comonomer content of HPMA, GPMA, and IEMA is kept comparable. The influence of P(MEO₉ MA) block with various molecular weights is investigated over cytotoxicity, plasmid DNA (pDNA) binding, and transfection efficiency of the resulting polyplexes. Overall, the increase in molecular weight of P(MEO₉ MA) block demonstrates excellent biocompatibility with higher cell viability in L-929 cells and an efficient binding to pDNA at N/P ratio of 2. The significant transfection efficiency in CHO-K1 cells at N/P ratio 20 is obtained for block copolymers with molecular weight of P(MEO₉ MA) up to 10 kg mol^-1 . Moreover, a fluorescently labeled analogue of P(MEO₉ MA), bearing perylene monoimide methacrylamide (PMIM), is introduced as a comonomer in RAFT polymerization. Polyplexes consisting of labeled block copolymer with 20 kg mol^-1 of P(MEO₉ MA) and pDNA are incubated in Hela cells and investigated through structured illumination microscopy (SIM).

Nano-Assemblies from Amphiphilic PnBA-b-POEGA Copolymers as Drug Nanocarriers

The focus of this study is the development of highly stable losartan potassium (LSR) polymeric nanocarriers. Two novel amphiphilic poly(n-butyl acrylate)-block-poly(oligo(ethylene glycol) methyl ether acrylate) (PnBA-b-POEGA) copolymers with different molecular weight (M_w) of PnBA are synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization, followed by the encapsulation of LSR into both PnBA-b-POEGA micelles. Based on dynamic light scattering (DLS), the PnBA₃₀-b-POEGA₇₀ and PnBA₂₇-b-POEGA₇₃ (where the subscripts denote wt.% composition of the components) copolymers formed micelles of 10 nm and 24 nm in water. The LSR-loaded PnBA-b-POEGA nanocarriers presented increased size and greater mass nanostructures compared to empty micelles, implying the successful loading of LSR into the inner hydrophobic domains. A thorough NMR (nuclear magnetic resonance) characterization of the LSR-loaded PnBA-b-POEGA nanocarriers was conducted. Strong intermolecular interactions between the biphenyl ring and the butyl chain of LSR with the methylene signals of PnBA were evidenced by 2D-NOESY experiments. The highest hydrophobicity of the PnBA₂₇-b-POEGA₇₃ micelles contributed to an efficient encapsulation of LSR into the micelles exhibiting a greater value of %EE compared to PnBA₃₀-b-POEGA₇₀ + 50% LSR nanocarriers. Ultrasound release profiles of LSR signified that a great amount of the encapsulated LSR is strongly attached to both PnBA₃₀-b-POEGA₇₀ and PnBA₂₇-b-POEGA₇₃ micelles.

Atomistic insight towards the impact of polymer architecture and grafting density on structure-dynamics of PEGylated bovine serum albumin and their applications

Macromolecules such as proteins conjugated to polyethylene glycol (PEG) have been employed in therapeutic drug applications, and recent research has emphasized the potential of varying polymer architectures and conjugation strategies to achieve improved efficacy. In this study, we performed atomistic molecular dynamics simulations of bovine serum albumin (BSA) conjugated to 5 kDa PEG polymers in an array of schemes, including varied numbers of attached chains, grafting density, and nonlinear architectures. Nonlinear architectures included U-shaped PEG, Y-shaped PEG, and poly(oligoethylene glycol methacrylate) (POEGMA). Buried surface area calculations and polymer volume map analyses revealed that volume exclusion behaviors of the high grafting density conjugate promoted additional protein-polymer interactions when compared to simply increasing numbers of conjugated chains uniformly across the protein surface. Investigation of nonlinear polymer architectures showed that stable polymer-lysine loop-like conformations seen in previous conjugate designs were more variable in prevalence, especially in POEGMA, which contained short oligomer PEG chains. The findings of this comprehensive study of alternate PEGylation schemes of BSA provide critical insight into molecular patterns of interaction within bioconjugates and highlight their importance in the future of controlled modification of conjugate system parameters.

Combining CROP and ATRP to synthesize pH-responsive poly(2-ethyl-2-oxazoline-b-4-vinylpyridine) block copolymers

Herein, we present the synthesis and characterization of block copolymers based on the biocompatible and stealth polymer poly(2-ethyl-2-oxazoline) and the polydentate ligand and pH-responsive poly(4-vinylpyridine).

A supramolecular platform for controlling and optimizing molecular architectures of siRNA targeted delivery vehicles

It requires multistep synthesis and conjugation processes to incorporate multifunctionalities into a polyplex gene vehicle to overcome numerous hurdles during gene delivery. Here, we describe a supramolecular platform to precisely control, screen, and optimize molecular architectures of siRNA targeted delivery vehicles, which is based on rationally designed host-guest complexation between a β-cyclodextrin-based cationic host polymer and a library of guest polymers with various PEG shape and size, and various density of ligands. The host polymer is responsible to load/unload siRNA, while the guest polymer is responsible to shield the vehicles from nonspecific cellular uptake, to prolong their circulation time, and to target tumor cells. A series of precisely controlled molecular architectures through a simple assembly process allow for a rapid optimization of siRNA delivery vehicles in vitro and in vivo for therapeutic siRNA-Bcl2 delivery and tumor therapy, indicating the platform is a powerful screening tool for targeted gene delivery vehicles.

Phospholipid-Free Small Unilamellar Vesicles for Drug Targeting to Cells in the Liver

It is reported that cholesterol (Chol) and TWEEN 80 at a molar ratio of 5:1 can form small unilamellar vesicles (SUVs) using a staggered herringbone micromixer. These phospholipid-free SUVs (PFSUVs) can be actively loaded with a model drug for targeting hepatocytes via the endogenous apolipoprotein mechanism. PFSUVs particles with compositions of Chol:TWEEN 80 ranging between 1.5:1 and 5:1 (mol/mol) can be produced with a mean diameter of ≈80 nm, but only the high-Chol formulations (3:1 and 5:1) can retain a transmembrane gradient of ammonium sulfate for active loading of doxorubicin (DOX). Under cryo-transmission electron microscopy, PFSUVs-DOX displays a unilamellar bilayer structure with DOX molecules forming spindle-shape aggregates inside the aqueous core. Relative to PEGylated liposomal doxorubicin (PLD) that exhibits little interaction with cells in various conditions, the cellular uptake of PFSUVs-DOX is dependent on the presence of serum and enhanced with an increased concentration of apolipoproteins. After intravenous injection, the vast majority of PFSUVs-DOX accumulates in the liver and DOX is detected in all liver cells (predominantly the hepatocytes), while PLD is captured only by the sinusoidal cells (i.e., macrophages). This report discloses an innovative lipid bilayer vesicle for highly efficient and selective hepatocyte targeting.

Anticancer drug delivery to cancer cells using alkyl amine-functionalized nanodiamond supraparticles

Nanocarriers have attracted increasing interest due to their potential applications in anticancer drug delivery. In particular, the ability of nanodiamonds (NDs) to spontaneously self-assemble into unique nano-structured architectures has been exploited in the development of nanocarriers. In this context, we synthesized functional supraparticles (SPs) by the self-assembly of alkyl amine-modified NDs for use in anticancer chemotherapy. The structural, physical, and physiological properties of these ND-SPs as well as their high biocompatibility were assessed using microscopic techniques and various characterization experiments. Finally, a model anticancer drug (CPT; camptothecin) was loaded into the ND-SPs to investigate their anticancer efficacy in vitro and in vivo. After incubation of CPT-loaded ND-SPs with cancer cells, a dramatic anticancer effect of ND-SPs was expressed, compared to CPT-loaded ordinary nanocarriers of polyethylene glycol-modified polymer micelles and conventional Intralipid® 20% emulsions containing CPT. Our results demonstrated that ND-SPs may serve as a nanomedicine with significant therapeutic potential.

Synthesis of stimuli-responsive nanosized ring-like colloids and cyclic polymers via a dual-template approach

Ring-like particles have received considerable attention due to their unique interior cavity and properties. However, the preparation of stimuli-responsive nanosized rings with internal size smaller than 100 nm remains unexplored likely due to the challenges encountered in their synthesis. The successful fulfillment of this target will not only significantly enrich the family of ring-like nanoparticles but also build a connection that bridges ring-like nanoparticles and cyclic polymers. For this purpose, we report in this study a controlled synthesis of stimuli-responsive ring-like colloids and cyclic polymers using both star-shaped polymers and β-cyclodextrin (β-CD) as the dual templates. The first template comprising star-shaped polymers generated a ring-like structure and adoption of β-CD as the second template further restricted the ring thickness to the height of a β-CD, leading to the generation of stimuli-responsive nanosized ring-like colloids with ring thickness less than 1 nm, which shifted the ring-like structure to cyclic polymers with reversible cross-linked disulfide bridges. The reported "dual-template" approach is thus a valuable alternative to the current synthetic strategies toward stimuli-responsive ring-like colloids and cyclic polymers.

Multi-targeted approach by 2-benzimidazolylquinoxalines-loaded cationic arginine liposomes against сervical cancer cells in vitro

Multi-targeted approaches for inhibition of сervical cancer cells in vitro were developed by implementing two different strategies and drug combination for creation of new therapeutic target agents and for nanotechnological-enhancement of intracellular delivery. New 2-benzimidazolylquinoxalines derivatives were synthesized and characterized by combining two different pharmacophores - benzimidazole and quinoxaline rings directly bonded in their structures. Spectrophotometric technique for determination of content of compounds in various media was developed to evaluate their solubility in water and micellar solutions of surfactants. The bioavailability of poorly water-soluble 2-benzimidazolylquinoxalines was improved by PEGylated liposomes as antitumor drug delivery carriers. 2-benzimidazolylquinoxalines-loaded PEGylated liposomes, with size close to 100 nm and negative zeta potential ranging from -13 mV to -27 mV, were time-stable at room temperature. The design of liposomal formulations for improving cellular uptake and in vitro antitumor efficacy was performed by modification of liposome surface with the new arginine surfactant. The cell viability of 2-benzimidazolylquinoxalines-loaded arginine liposomes on human cancer M-Hela cells was 16% at the concentration 0.15 mg/ml. Moreover, these liposomes showed a lower toxicity (40%) against normal human Gang liver cells both at the lowest and highest tested concentrations.