Optimal Liposomal Formulation Research Articles

Formulation of Metoclopramide Hydrochloride-Loaded Lipid Carriers by QbD Approach for Combating Nausea: Safety and Bioavailability Evaluation in New Zealand Rabbit.

The focus of the research was to overcome the limitations of metoclopramide (MTC) when administered intranasally. The aim was to improve its bioavailability, increase patient compliance, and prolong its residence time in the nasal cavity. MTC-loaded liposomes were prepared by applying the film hydration method. A study was conducted to determine how formulation variables affected encapsulation efficiency (EE %), mean particle size (MPS), and zeta potential (ZP). The MTC-liposomes were further loaded into the in situ gel (gellan gum) for longer residence times following intranasal administration. pH, gelling time, and in vitro release tests were conducted on the formulations produced. In vivo performance of the MTC-loaded in situ gels was appraised based on disparate parameters such as plasma peak concentration, plasma peak time, and elimination coefficient compared to intravenous administration. When the optimal liposome formulation contained 1.98% of SPC, 0.081% of cholesterol, 97.84% of chloroform, and 0.1% of MTC, the EE of MTC was 83.21%, PS was 107.3 nm. After 5 h, more than 80% of the drug was released from MTC-loaded liposome incorporated into gellan gum in situ gel formulation (Lip-GG), which exhibited improved absorption and higher bioavailability compared to MTC loaded into gellan gum in situ gel (MTC-GG). Acceptable cell viability was also achieved. It was found out that MTC-loaded liposomal in situ gel formulations administered through the nasal route could be a better choice than other options due to its ease of administration, accurate dosing, and higher bioavailability in comparison with MTC-GG.

In silico exploration of venlafaxine, a potential non-tricyclic antidepressant in a liposomal formulation for nose-to-brain drug delivery

Objective Non-tricyclic antidepressants (non-TCAs) work by preventing the intake of norepinephrine and serotonin. Therefore, the aim of this study was to identify a potent non-TCAs and to develop liposomal formulation, characterize and to determine the drug release study across model of dialysis membrane via in vitro and in silico techniques. Methods The in silico docking analysis identified venlafaxine (VLF) as the best non-TCAs with the depressant targets (PDB ID: 3PBL and 4BVN). VLF-loaded liposomal formulation was prepared by the thin-film hydration technique and characterized by physicochemical properties, including entrapment efficacy, in vitro drug release, particle size analysis, and FTIR. Moreover, this article also compares VLF and VLF-loaded with liposome carriers (LPs) based on nose-to-brain drug delivery approaches to treating depression. Results Drug release profiles of the optimal liposomal formulation of VLF-LPs were examined in the high entrapment efficiency 94.13 ± 1.20% was attained at 224 nm, composed of spherical particles having a mean particle size of 191 ± 2.0 nm, a polydispersity index of 0.281 ± 0.06 and zeta potential of −20.3 mV. The best formulation of VLF-LPs was more effective than oral VLF treatment, as shown by the in vitro drug release data. Conclusion The results show that the VLF-LPs formulation is a promising potential platform for application in nose-to-brain drug delivery. Thus, highlighting the robustness of the intranasal drug delivery system with enhanced pharmaceutical properties, efficacy, and bioavailability for the anti-depression effect.

Optimization, evaluation and comparative IVPT study of micro and nano liposomal topical formulations of apremilast

Atopic Dermatitis (AD) is an immune system-related, pruritic, chronically relapsing, skin inflammatory disease, which is more prevalent in children while it also affects adults. Apremilast (APT), available in market as a film-coated tablet for oral administration and is indicated for treatment of adult patients with active psoriatic arthritis. Apremilast is a BCS IV drug, has low permeability and solubility. Thus, prepared micro and nano-liposomes of apremilast for enhancement of permeability and compared with cetirizine and niacinamide using in-silico modeling approach. Liposomes were prepared by film hydration technique utilizing design experiment for optimization and evaluated their physicochemical properties such as particle size, PDI, entrapment efficiency, morphology by TEM, interaction study and in-vitro skin permeation test (IVPT) of both prototypes was performed using Franz Diffusion cell (cadaver skin). The prepared optimized liposome formulations showed particle size 2 ± 0.3 µm (microliposomes), 200 ± 31 nm (nanoliposomes), 0.18 ± 0.05 PDI and high entrapment efficiency (95.3 %). TEM image reveal that most of the particles were spherical and no tear was observed. Permeation test (IVPT) of both prototypes showed insignificant difference (p > 0.05) in the permeation of Apremilast delivered by micro-liposomes and nano-liposomes. The outcome of this study contradicted our hypothesis and the conclusion of many other published studies, which had demonstrated that delivery of drug molecules into skin depends on the particle size of liposome.

The manufacturing of 3D-printed microfluidic chips to analyse the effect upon particle size during the synthesis of lipid nanoparticles.

The process of 3D printing to produce microfluidic chips is becoming commonplace, due to its quality, versatility and newfound availability. In this study, a UV liquid crystal display (LCD) printer has been implemented to produce a progression of microfluidic chips for the purpose of liposomal synthesis. The emphasis of this research is to test the limitations of UV LCD printing in terms of resolution and print speed optimisation for the production of microfluidic chips. By varying individual channel parameters such as channel length and internal geometries, the essential channel properties for optimal liposomal formulation are being investigated to act as a basis for future experimentation including the encapsulation of active pharmaceutical ingredients. Using the uniquely designed chips, liposomes of ≈120 nm, with polydispersity index values of ≤0.12 are able to be reproducibly synthesised. The influence of total flow rates and lipid choice is investigated in depth, to provide further clarification on how a microfluidic setup should be optimised. In-depth explanations of the importance of each channel parameter are also explained throughout, with reference to their importance for the properties of a successful liposome.

Liposomal siRNA Formulations for the Treatment of Herpes Simplex Virus-1: In Vitro Characterization of Physicochemical Properties and Activity, and In Vivo Biodistribution and Toxicity Studies.

Herpes simplex virus-1 (HSV-1) is highly contagious, and there is a need for a therapeutic means to eradicate it. We have identified an siRNA (siHSV) that knocks down gene expression of the infected cell protein 0 (ICP0), which is important in the regulation of HSV infection. The selected siHSV was encapsulated in liposomes to overcome its poor stability, increase cell permeability, and prolonging siRNA circulation time. Several siRNAs against ICP0 have been designed and identified. We examined the role of various parameters, including formulation technique, lipids composition, and ratio. An optimal liposomal siHSV formulation (LipDOPE-siHSV) was characterized with desirable physiochemical properties, in terms of nano-size, low polydispersity index (PDI), neutral surface charge, high siHSV loading, spherical shape, high stability in physiologic conditions in vitro, and long-term shelf-life stability (>1 year, 4 °C). The liposomes exhibited profound internalization by human keratinocytes, no cytotoxicity in cell cultures, no detrimental effect on mice liver enzymes, and a gradual endo-lysosomal escape. Mice biodistribution studies in intact mice revealed accumulation, mainly in visceral organs but also in the trigeminal ganglion. The therapeutic potential of siHSV liposomes was demonstrated by significant antiviral activity both in the plaque reduction assay and in the 3D epidermis model, and the mechanism of action was validated by the reduction of ICP0 expression levels.

Entrapment of rosemary extract by liposomes formulated by Mozafari method: physicochemical characterization and optimization

A major obstacle in the utilization of phenolic antioxidant compounds is their sensitivity and as a result stability issue. The current study aimed to encapsulate polyphenolic compounds, extracted from Rosemary, in liposomes prepared by the Mozafari method without the utilization of toxic solvents or detergents. The extract was prepared and converted into a powder by freeze-drying. The process conditions were optimized using response surface analysis, and the optimal parameters were as follows: phosphatidylcholine (PC), 2.5% (25 mg/mL); extract, 0.7% (7 mg/mL); process temperature, 70 °C and process time, 60 min. The entrapment efficiency in optimal sample was 54.59%. Also, optimal glycerosomes formulation were finally physicochemical characterized (permeability, zeta potential, and size distribution). The mean size of empty and containing rosemary extract glycerosome were 265.4 nm and 583.5 nm, respectively, and the Z-potential of optimal glycerosome was -65.1 mV. Total phenolic content was obtained 151.38 mg gallic acid/g extract, in optimal liposomal formulation, which was measured by Folin-Ciocalteu's phenol reagent. Also, the antioxidant activity of rosemary extract by DPPH for the free and optimal liposomal formulation was determined to be 84.57% and 92.5% respectively. It can be concluded that the liposomal rosemary extract formulation prepared in this study, employing a safe, scalable, and green technology, has great promise in food and pharmaceutical applications.

Formulation design and optimization of cationic-charged liposomes of brimonidine tartrate for effective ocular drug delivery by design of experiment (DoE) approach

Objective The present study was aimed to design and optimize brimonidine tartrate (BRT) loaded cationic-charged liposome formulation with enhanced trans-corneal drug permeation, prolonged corneal residence, and sustained drug release for effective ocular delivery. Methods Design of experiment (DoE) based formulation optimization was done by three-factor, three-level Box–Behnken design selecting lipid, cholesterol, and drug content as independent variables and particle size (PS), polydispersity index (PDI), zeta potential (ZP), entrapment efficiency (EE%), and cumulative % drug release (CDR) as response variables. The optimized formulation consisting of 79.2 mM lipid, 36.2 mM cholesterol, and 15.8 mg/mL drug was prepared by thin film hydration-sonication method using EPCS:DOTAP (1:1) as lipid component and characterized for all desired critical quality attributes (CQAs), drug release kinetics, TEM, DSC, XRD analysis, ex vivo trans-corneal drug permeation, and physical stability studies. Results The optimized liposome formulation exhibited experimentally observed responses close to predicted values having 150.4 nm (PS), 0.203 (PDI), 30.62 mV (ZP), and 55.17% (EE). The observed CDR (%) was 36.15% at 1 h and 91.13% at 12 h exhibiting sustained drug release profile and followed Higuchi drug release kinetics. The TEM, DSC, and XRD studies revealed spherical, nanosized, small unilamellar vesicles effectively entrapping BRT in liposomes. The ex vivo permeation study across goat cornea recorded apparent permeability (P app) 1.011 ± 0.07 cm.min−1 and steady-state flux (J ss) 17.63 ± 1.22 µg.cm−2.min−1 showing >2-fold enhanced drug permeation as compared to BRT solution. Conclusion The developed liposomal formulation possessed all recommended CQAs in optimal range with enhanced trans-corneal drug permeation and remained physically stable in 3 months stability study.

Liposomes Loaded with Unsaponifiable Matter from Amaranthus hypochondriacus as a Source of Squalene and Carrying Soybean Lunasin Inhibited Melanoma Cells.

Amaranthus hypochondriacus is a source of molecules with reported health benefits such as antioxidant activity and cancer prevention. The objective of this research was to optimize the conditions for preparing a liposome formulation using amaranth unsaponifiable matter as a source of squalene in order to minimize the particle size and to maximize the encapsulation efficiency of liposomes for carrying and delivering soybean lunasin into melanoma cell lines. Amaranth oil was extracted using supercritical dioxide carbon extraction (55.2 MPa pressure, 80 °C temperature, solvent (CO2)-to-feed (oil) ratio of 20). The extracted oil from amaranth was used to obtain the unsaponifiable enriched content of squalene, which was incorporated into liposomes. A Box–Behnken response surface methodology design was used to optimize the liposome formulation containing the unsaponifiable matter, once liposomes were optimized. Soybean lunasin was loaded into the liposomes and tested on A-375 and B16-F10 melanoma cells. The squalene concentration in the extracted oil was 36.64 ± 0.64 g/ 100 g of oil. The particle size in liposomes was between 115.8 and 163.1 nm; the squalene encapsulation efficiency ranged from 33.14% to 76.08%. The optimized liposome formulation contained 15.27 mg of phospholipids and 1.1 mg of unsaponifiable matter. Cell viability was affected by the liposome formulation with a half-maximum inhibitory concentration (IC50) equivalent to 225 μM in B16-F10 and 215 μM in A-375. The liposomes formulated with lunasin achieved 82.14 ± 3.34% lunasin encapsulation efficiency and improved efficacy by decreasing lunasin IC50 by 31.81% in B16-F10 and by 41.89% in A-375 compared with unencapsulated lunasin.

Formulations Based on Drug Loaded Aptamer-Conjugated Liposomes as a Viable Strategy for the Topical Treatment of Basal Cell Carcinoma-In Vitro Tests.

Topical liposomal drug formulations containing AS1411-aptamer conjugated liposomes were designed to deliver in a sustained way the 5-fluorouracil to the tumor site but also to increase the compliance of patients with basal cell carcinoma. The 5-fluorouracil penetrability efficiency through the Strat-M membrane and the skin irritation potential of the obtained topical liposomal formulations were evaluated in vitro and the Korsmeyer Peppas equation was considered as the most appropriate to model the drug release. Additionally, the efficiency of cytostatic activity for targeted antitumor therapy and the hemolytic capacity were performed in vitro. The obtained results showed that the optimal liposomal formulation is a crosslinked gel based on sodium alginate and hyaluronic acid containing AS1411-aptamer conjugated liposomes loaded with 5-fluorouracil, which appeared to have favorable biosafety effects and may be used as a new therapeutic approach for the topical treatment of basal cell carcinoma.

Quality by Design Approach for the Development of Liposome Carrying Ghrelin for Intranasal Administration.

The therapeutic use of peptides has increasingly recognized in the development of new therapies. However, the susceptible enzymatic cleavage is a barrier that needs to overcome. Nose-to-brain delivery associated with liposomes can protect peptides against biodegradation and improve the accessibility to brain targets. The aim was to develop a liposomal formulation as ghrelin carrier. The quality by design (QbD) approach was used as a strategy for method development. The initial risk assessments were carried out using a fishbone diagram. A screening design study was performed for the critical material attributes/critical process parameters (CMAs/CPPs) on critical quality attributes (CQAs). Liposomes were obtained by hydrating phospholipid films, followed by extrusion or homogenization, and coated with chitosan. The optimized liposome formulation was produced by high-pressure homogenization coated with chitosan, and the resulted were liposomes size 72.25 ± 1.46 nm, PDI of 0.300 ± 0.027, the zeta potential of 50.3 ± 1.46 mV, and encapsulation efficiency of 53.2%. Moreover, chitosan coating improved performance in ex vivo permeation and mucoadhesion analyzes when compared to the uncoated liposome. In this context, chitosan coating is essential for the performance of the formulations in the ex vivo permeation and mucoadhesion analyzes. The intranasal administration of ghrelin liposomes coated with chitosan offers an innovative opportunity to treat cachexia.

Levobupivacaine-Loaded Liposome Associated with Thermogel for Prolonged Analgesia.

Pain is a phenomenon present in the majority of the population, affecting, among others, the elderly, overweight people, and especially recently operated patients, analgesia being necessary. In the specific case of relief of postoperative pain, different kinds of anesthetics are being used, among them bupivacaine, a widely used drug which promotes long-lasting analgesic effects. However, cardiotoxicity and neurotoxicity are related to its repetitive use. To overcome these shortcomings, Novabupi® (a racemic mixture) was developed and is marketed as an injectable solution. This formulation contains an enantiomeric excess of the levogyre isomer, which has reduced toxicity effects. Seeking to rationalize its use by extending the duration of effect and reducing the number of applications, the objectives of this work were to develop and evaluate liposomes containing Novabupi (LBPV), followed by incorporation into thermogel. Liposomes were prepared using the lipid hydration method, followed by size reduction using sonication, and the developed formulations were characterized by hydrodynamic diameter, polydispersity index (PDI), surface zeta potential, and encapsulation efficiency. The selected optimal liposomal formulation was successfully incorporated into a thermogel without loss of thermoresponsive properties, being suitable for administration as a subcutaneous injection. In the ex vivo permeation studies with fresh rodent skin, the thermogel with liposomes loaded with 0.5% LBPV (T-gel formulation 3) showed higher permeation rates compared to the starting formulation, thermogel with 0.5% LBPV (T-Gel 1), which will probably translate into better therapeutic benefits for treatment of postoperative analgesia, especially with regard to the number of doses applied.

Beyond Trial and Error: A Systematic Development of Liposomes Targeting Primary Macrophages

Monocytes/macrophages are phagocytic innate immune cells playing a pivotal role in tissue homeostasis, inflammation, and antitumor immunity in a microenvironment‐dependent manner. By expressing pattern recognition and scavenger receptors on their surface, macrophages selectively take up pathogens, cellular debris, and often—undesirably—drug delivery systems. On the other hand, the propensity of phagocytic cells to internalize particulate drug carriers is used to load them with a cargo of choice, turning the monocytes/macrophages into a diagnostic or therapeutic Trojan horse. Identifying the ideal physicochemical properties of particulate carriers such as liposomes to achieve the most efficient macrophage‐mediated drug delivery has been object of extensive research in the past, but the studies reported so far rely solely on trial‐and‐error approaches. Herein, a design of experiment (DoE) strategy to identify the optimal liposomal formulation is proposed, fully characterized in terms of size, surface charge, and membrane fluidity, to maximize macrophage targeting. The findings are validated using mouse bone marrow‐derived macrophages, a primary preparation modeling in vivo monocyte‐derived macrophages, thus confirming the robustness and versatility of the systematic and iterative approach and suggesting the promising potential of the DoE approach for the design of cell‐targeting delivery systems.

Mitotane liposomes for potential treatment of adrenal cortical carcinoma: ex vivo intestinal permeation and in vivo bioavailability

The adrenal cortical carcinoma (ACC) treatment, for which mitotane (o,p′-DDD) is the drug of choice, still remains a challenge both because of the well-known solubility problems of the drug, and its serious side effects. Mitotane is currently administered as oral tablets. The loading of mitotane into nanocarriers has been suggested as a way to circumvent the low solubility of the drug and its limited oral bioavailability. In this work, we have developed liposomes containing mitotane to enhance its intestinal absorption and oral bioavailability. Liposomes were produced by spray-drying of a mixture of phospholipids and the developed formulation was optimized by studying the degree of crystallinity, spray-drying conditions, phospholipid/mitotane ratio, and influence of mannitol in the hydrating ethanolic solution. An optimal liposomal formulation was produced with a phospholipid:mitotane combination (3.34:1), exhibiting a mean hydrodynamic diameter around 1 μm and spherical shape. The produced mitotane liposomes were re-suspended by hydrating the spray-dried powders in a stirred tank, and tested their intestinal permeability (ex vivo) and relative bioavailability (in vivo), against a free drug solution (with or without Trigliceril®CM). Our results support the conclusion that the loading of mitotane in liposomes enhanced its intestinal absorption and relative bioavailability.

Phenylethyl Resorcinol Loaded in Liposomal Cream Formulation for Cosmeceutical Application

Phenylethyl Resorcinol (PR) is a cosmeceutical skin lightening agent and the purpose of this study was to enhance its stability by using liposomal cream formulation which increases local efficacy and safety. Liposome formulation was prepared by modified ethanol injection method, and it contained soy phosphatidyl choline (SPC), cholesterol (CHO), Tween 80 (TW80) and deoxycholic acid (DA) mixed with 2% PR. The physicochemical properties, skin permeation as well as cellular study were evaluated in order to obtain the optimized formulation. The optimized liposome formulation composed of SPC:TW80:DA (84:16:2.5) and exhibited vesicle size, polydispersity index (PDI) and zeta potential of 286.4±8.04 nm, 0.317±0.03 and -39.20±3.85 mV, respectively. Entrapment efficiency (EE) of liposome formulation was 93.55±0.05%. The vesicle was spherical in shape and showed good physicochemical stability for 4 months. The skin permeation study demonstrated that liposome with a negative charge could result in a high PR skin deposition value of 1732.76±216.24 µg/cm2 after 24 h. Cellular study showed that liposome formulation could inhibit melanin content in B16 melanoma cells and enhance cell viability in HaCaT keratinocyte cells. The optimized PR liposome was incorporated in cream and investigated physicochemical properties, stability and skin permeation. Liposomal PR cream showed a good stability and a superior result than PR cream in skin permeation parameters, as well as in tyrosinase inhibition.

Development of a novel liposomal nanoparticle formulation of cisplatin to breast cancer therapy.

Cisplatin is one of the conventional drugs used in chemotherapy which has a potent antitumor function. However, due to the dangerous side effects, including the damage to DNA of the normal cells, its clinical use is limited. The aim of this study was to prepare and characterize nanoliposome containing cisplatin. We optimized liposome formulations through the modification of the proportion of SPC80 (soybeanphospholipids with 75% phosphatidylcholine) and cholesterol content. Then, novel PEGylated liposomal formulations containing SPC80: cholesterol: DSPE-mPEG (at ratios of 85:10:5) were designed and developed to serve as a therapy to achieve more improved pharmaceutical efficiency. Zeta Sizer showed that PEGylated nanoliposomes had a mean diameter of 119.7 ± 2.1 nm, a zeta potential of -26.03 ± 1.34 mV, and entrapment efficiency of 96.65 ± 3%. The optimum formulations represented sustained, thermo-sensitive release, and augmented cellular uptake. The cytotoxic effect of the liposomal drug was higher than the free medication drug that confirmed the efficiency of cellular uptake. This study suggests that nanoliposome-loaded cisplatin plays a vital role in improving drug efficacy and the reduction of dosage.

Gene delivery into hepatic cells with ternary complexes of plasmid DNA, cationic liposomes and apolipoprotein E-derived peptide.

Cationic liposomes containing a cationic lipid, such as 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), have often been used for the transduction of plasmid DNA (pDNA) in vivo. However, such liposomes induce gene expression primarily in the lungs after intravenous injection. To improve the delivery of cationic liposomes/pDNA complexes (pDNA lipoplexes) to the liver by intravenous administration, the current study synthesized two apolipoprotein E (ApoE)-derived peptides, dApoE-R9 and ApoE-F-R9, for liver targeting via certain ApoE receptors, including the low-density lipoprotein receptor. Ternary complexes of pDNA, cationic liposomes and ApoE-R9 peptide were also prepared. After in vitro transfection, ternary complexes with DOTAP/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) liposomes exhibited high transfection activity in HepG2 cells compared with DOTAP/cholesterol (Chol) liposomes. In particular, ternary complexes with dApoE-R9 exhibited high transfection activity in cells compared with ApoE-F-R9. However, in vivo transfection studies revealed that ternary complexes with DOTAP/DOPE liposomes and dApoE-R9 did not increase gene expression in the liver compared with DOTAP/DOPE lipoplexes. In contrast, ternary complexes with DOTAP/Chol liposomes and dApoE-R9 increased gene expression in the liver compared with DOTAP/Chol lipoplexes. The results demonstrated that the in vivo optimal liposomal formulation in ternary complexes with ApoE-R9 peptide for liver delivery were different from those that were in vitro.

Liposomes of probiotic's lyophilized cell free supernatant; a potential cosmeceutical product.

The potential uses of lyophilized cell free supernatant (CFS) of human oral derived Lactobacillus paracasei SD1 and Lactobacillus rhamnosus SD11 as cosmeceutical ingredients were investigated in the present study. Lyophilized CFS of both strains showed the antioxidant activity in concentration dependent manner. They also exhibited antimicrobial activity against P. acne, S. aureus and S. epidermidis. In combination, these two strains produced synergistic responses, not only on antioxidant activity but also on antimicrobial activity. A liposomal delivery system was employed to mask the unpleasant colour and odour of CFS. The optimal liposome formulation was characterized by a particle size of 344 nm, PDI of 0.19, zeta value of -48.05 mV and %EE of 69.45. The cytotoxicity results showed that the lyophilized CFS, which was toxic, became non-toxic after encapsulating into liposomes. Altogether, current findings demonstrate the worthiness of development of liposomes of probiotic's lyophilized CFS for cosmeceutical applications.

Development of doxorubicin hydrochloride loaded pH-sensitive liposomes: Investigation on the impact of chemical nature of lipids and liposome composition on pH-sensitivity

This study investigates the impact of the chemical nature of lipids and additive on the formulation and properties of pH sensitive liposomes. The objective is to understand the respective role of the formulation parameters on the liposome properties in order to optimize the conditions for efficient encapsulation of doxorubicin (DOX). These liposomes should be stable at physiological pH, and disrupt in slightly acidic media such as the tumor microenvironment to release their DOX load. The major challenge for encapsulating DOX in pH sensitive liposomes lies in the fact that this drug is soluble at low pH (when the pH-sensitive liposomes are not stable), but the DOX aqueous solubility decreases in the pH conditions corresponding to the stability of the pH-sensitive liposomes. The study of pH-sensitivity of liposomes was conducted using carboxyfluorescein (CF) encapsulated in high concentration, i.e. quenched, and following the dye dequenching as sensor of the liposome integrity. We studied the impact of (i) the chemical nature of lipids (dioleoyl phosphatidyl ethanolamine (DOPE), palmitoyl-oleoyl phosphatidyl ethanolamine (POPE) and dimyristoyl phosphatidyl ethanolamine (DMPE)) and (ii) the lipid/stabilizing agent ratio (alpha-tocopheryl succinate), on the pH sensitivity of the liposomes. Optimized liposome formulations were then selected for the encapsulation of DOX by an active loading procedure, i.e. driven by a difference in pH inside and outside the liposomes. Numerous experimental conditions were explored, in function of the pH gradient and liposome composition, which allowed identifying critical parameters for the efficient DOX encapsulation in pH-sensitive liposomes.

Microfluidic self-assembly of a combinatorial library of single- and dual-ligand liposomes for in vitro and in vivo tumor targeting

Precise engineering of nanoparticles with systematically varied properties (size, charge surface properties, targeting ligands, etc.) remains a challenge, limiting the effective optimization of nanoparticles for particular applications. Herein we report a single-step microfluidic combinatorial approach for producing a library of single and dual-ligand liposomes with systematically-varied properties including size, zeta potential, targeting ligand, ligand density, and ligand ratio. A targeting ligand folic acid and a cell penetrating peptide TAT were employed to achieve the optimal synergistic targeting effect. In 2D cell monolayer models, the single-ligand folic acid modified liposome didn’t show any enhanced cellular uptake, while the incorporation of TAT peptide “switched on” the function of folic acid, and induced significant elevated cellular uptake compared to the single ligand modified liposomes, showing a strong synergistic targeting effect. The folic acid and TAT peptide dual-ligand liposome also demonstrated enhanced tumor penetration as observed using 3D tumor spheroid models. The in vivo study further confirmed the improved tumor targeting and longer tumor retention (up to 72 h) of the dual-ligand liposomes. Our work not only proved the versatility of this microfluidic combinatorial approach in producing libraries of multifunctional liposomes with controlled properties but also revealed the great potential of the optimized liposome formulation for synergistic targeting effects.

Detection of Sunlight Exposure with Solar-Sensitive Liposomes that Capture and Release Food Dyes

Direct assessment of sunlight exposure can be challenging over extended periods or in multiple remote locations. We optimized liposome formulations that included egg and hydrogenated soy lipids as well as small amounts of a chlorophyll-derived phospholipid (PoP) to confer sunlight reactivity and triggered-release of entrapped dyes. Dye release occurred with PoP-mediated photooxidation of unsaturated phospholipids and could be tuned by varying the unsaturated (egg) to saturated (soy) lipid ratio or by varying the amount of PoP included. Numerous food coloring dyes were entrapped within the liposomes and, when applied onto a polyacrylamide gel, remained intact and immobilized for at least a month in the dark. When exposed to sunlight, the dyes were released and rapidly diffused through the gel, creating a detection system for assessing sunlight exposure by the naked eye based on dye diffusion. Acid Blue 9 and Acid Yellow 23 were particularly effective reporter food dyes in this system. By using liposomes with varying PoP amounts, light-induced dye release could be tuned to coincide with varying amounts of solar exposure. Additionally, exposure-dependent, color-coded release patterns were generated using colloidal mixtures of separately formed liposomes loaded with different dyes. Using customized 3D printed enclosures, a small and readily deployable device was created for visualizing solar-sensitive liposome sunlight reporting. These studies show proof-of-principle that PoP liposomes can serve as simple nonelectric reporters for visually assessing sunlight exposure based on diffusion of entrapped food coloring.