Characterization of drug release from liposomal formulations in ocular fluid

Architecting novel multilayer nanosponges for co-administration of two drugs managing high-risk type II diabetes mellitus patients suffering from cardiovascular diseases

Nanosponges are porous solid nanoparticles composed of hyper-cross-linked polymers that serve as specific micro-domains designed for the co-encapsulation of two drugs with different chemical structures. Our goal was to engineer a novel assembly of multilayer nanosponges (MLNS) based on a layer-by-layer approach. This MLNS was engineered to incorporate two drugs (linagliptin and empagliflozin) in a new drug delivery route. Linagliptin has a low oral bioavailability due to intestinal degradation and low permeability. Its pharmacokinetics shows a non-linear profile which leads to a disproportionate increase in its effectiveness with increasing the dose frequency. Empagliflozin has a low permeability and is very slightly soluble in aqueous media between pH 1-7.5. MLNS could improve their bioavailability along with resolving possible risks due to the non-linear pharmacokinetics of linagliptin and maximizing its dose efficiency. 2³ factorial design was used to optimize the novel systems. MLNS (F4) was chosen as the optimal system with an average diameter of 40 nm and the highest entrapment efficiency which accounts for 92.93 % ± 2.27 and 100.94 % ± 0.55 for linagliptin and empagliflozin respectively. Förster resonance energy transfer confirmed the formation of a multilayer structure in MLNS. The optimized system was incorporated within chitosan mucoadhesive buccal films which were optimized through 2²factorial design. The permeation study from optimized MLNS-film (B4) ensured an improved empagliflozin permeation along with a controlled efflux for linagliptin, resolving possible risks due to the nonlinear plasma profile. The in-vivo study of MLNS-film (B4) revealed that AUC_(0-∞)of linagliptin and empagliflozin was enhanced by two-fold and ten-fold, respectively. Therefore, the nano-buccal formulation for the co-delivered hypoglycemic drugs could contribute to improved clinical efficacy in the treatment of diabetes.

Optimization and Characterization of a Liposomal Azithromycin Formulation for Alternative Macrophage Activation

Liposomal azithromycin (L-AZM) promotes macrophage polarization toward an M2-like phenotype in the context of myocardial infarction that results in improved cardiovascular outcomes in mice. To improve upon this formulation, we sought to identify optimized formulation, stability, and biological activity parameters necessary to enhance the immunomodulatory activity and efficacy of L-AZM. While our parent formulation contains a mixture of long-chain saturated phosphatidylcholine and phosphatidylglycerol lipids, we evaluated a series of formulations with different amounts of unsaturated lipids and cholesterol with the goal of improving the loading capacity and stability of the formulations. We also introduce fusogenic lipids to improve the cytosolic delivery to enhance the immune modulatory properties of the drug. To achieve these goals, we initially prepared a library of 24 formulations using thin film hydration and assessed the resultant liposomes for size and polydispersity. Five lead formulations were identified based on low polydispersity (<0.3) and stability over time. The lead formulations were then evaluated for stability in serum using dialysis and macrophage polarization activity in vitro as measured by decreased IL-12 expression. Collectively, our data indicate that the formulation components drive the balance between encapsulation efficiency and stability and that all the lead liposomal formulations improve in vitro alternative macrophage activation as compared to free AZM.

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 3-factor, 3-level Box-Behnken design selecting lipid, cholesterol, and drug content as independent variables and particle size (PS), 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 1h and 91.13% at 12h 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.

The pH-Dependent Controlled Release of Encapsulated Vitamin B1 from Liposomal Nanocarrier

In this work, we firstly presented a simple encapsulation method to prepare thiamine hydrochloride (vitamin B1)-loaded asolectin-based liposomes with average hydrodynamic diameter of ca. 225 and 245 nm under physiological and acidic conditions, respectively. In addition to the optimization of the sonication and magnetic stirring times used for size regulation, the effect of the concentrations of both asolectin carrier and initial vitamin B1 on the entrapment efficiency (EE %) was also investigated. Thermoanalytical measurements clearly demonstrated that after the successful encapsulation, only weak interactions were discovered between the carriers and the drug molecules. Moreover, the dissolution profiles under physiological (pH = 7.40) and gastric conditions (pH = 1.50) were also registered and the release profiles of our liposomal B1 system were compared with the dissolution profile of the pure drug solution and a manufactured tablet containing thiamin hydrochloride as active ingredient. The release curves were evaluated by nonlinear fitting of six different kinetic models. The best goodness of fit, where the correlation coefficients in the case of all three systems were larger than 0.98, was reached by application of the well-known second-order kinetic model. Based on the evaluation, it was estimated that our liposomal nanocarrier system shows 4.5-fold and 1.5-fold larger drug retention compared to the unpackaged vitamin B1 under physiological conditions and in artificial gastric juice, respectively.

Suppression of Intracellular Reactive Oxygen Species in Human Corneal Epithelial Cells via the Combination of Quercetin Nanoparticles and Epigallocatechin Gallate and In Situ Thermosensitive Gel Formulation for Ocular Drug Delivery

Oxidative stress can cause several severe ophthalmological diseases. In this study, we developed a thermosensitive gel as a delivery system for two antioxidant substances, namely, quercetin and epigallocatechin gallate. The quercetin was loaded in the PLGA nanoparticles using a solvent displacement method. The physical and chemical stability of the quercetin nanoparticles were evaluated, and the degradation kinetics of the quercetin in the nanoparticles was investigated. The in vitro antioxidant and intracellular reactive oxygen species inhibition of the quercetin nanoparticles, combined with the epigallocatechin gallate (EGCG), were determined using a 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay and a 2,7-dichlorodihydrofluorescein fluorescent probes, respectively. The thermosensitive gel loaded with the quercetin nanoparticles and EGCG was formulated. We confirmed that quercetin nanoparticles displayed the desired physical characteristics, release kinetics, and stability. The combination of quercetin nanoparticles and EGCG suggested the additive effect of antioxidant activity. We also demonstrated the superior intracellular ROS inhibition activity of the quercetin nanoparticles and EGCG with n-acetyl cysteine. The thermosensitive gel showed an appropriate gelation temperature and time for ocular drug delivery. Our results provide promising prospects for applying the thermosensitive gel loaded with quercetin nanoparticles and EGCG as an efficient drug delivery system for antioxidant activity in human corneal epithelial cells.

Targeting brain cells with glutathione-modulated nanoliposomes: in vitro and in vivo study

Background

The blood–brain barrier prevents many drug moieties from reaching the central nervous system. Therefore, glutathione-modulated nanoliposomes have been engineered to enhance the targeting of flucytosine to the brain.

Methods

Glutathione-modulated nanoliposomes were prepared by thin-film hydration technique and evaluated in the primary brain cells of rats. Lecithin, cholesterol, and span 65 were mixed at 1:1:1 molar ratio. The molar percentage of PEGylated glutathione varied from 0 mol% to 0.75 mol%. The cellular binding and the uptake of the targeted liposomes were both monitored by epifluorescent microscope and flow cytometry techniques. A biodistribution and a pharmacokinetic study of flucytosine and flucytosine-loaded glutathione–modulated liposomes was carried out to evaluate the in vivo brain-targeting efficiency.

Results

The size of glutathione-modulated nanoliposomes was <100 nm and the zeta potential was more than −65 mV. The cumulative release reached 70% for certain formulations. The cellular uptake increased as molar percent of glutathione increased to reach the maximum at 0.75 mol%. The uptake of the targeted liposomes by brain cells of the rats was three times greater than that of the nontargeted liposomes. An in vivo study showed that the relative efficiency was 2.632±0.089 and the concentration efficiency was 1.590±0.049, and also, the drug-targeting index was 3.670±0.824.

Conclusion

Overall, these results revealed that glutathione-PEGylated nanoliposomes enhance the effective delivery of flucytosine to brain and could become a promising new therapeutic option for the treatment of the brain infections.

Stealth anti-CD4 conjugated immunoliposomes with dual antiretroviral drugs--modern Trojan horses to combat HIV

Highly active antiretroviral therapy (HAART) is the currently employed therapeutic intervention against AIDS where a drug combination is used to reduce the viral load. The present work envisages the development of a stealth anti-CD4 conjugated immunoliposomes containing two anti-retroviral drugs (nevirapine and saquinavir) that can selectively home into HIV infected cells through the CD4 receptor. The nanocarrier was characterized using transmission electron microscopy, FTIR, differential scanning calorimetry, particle size and zeta potential. The cell uptake was also evaluated qualitatively using confocal microscopy and quantitatively by flow cytometry. The drug to lipid composition was optimized for maximum encapsulation of the two drugs. Both drugs were found to localize in different regions of the liposome. The release of the reverse transcriptase inhibitor was dominant during the early phases of the release while in the later phases, the protease inhibitor is the major constituent released. The drugs delivered via anti-CD4 conjugated immunoliposomes inhibited viral proliferation at a significantly lower concentration as compared to free drugs. In vitro studies of nevirapine to saquinavir combination at a ratio of 6.2:5 and a concentration as low as 5 ng/mL efficiently blocked viral proliferation suggesting that co-delivery of anti-retroviral drugs holds a greater promise for efficient management of HIV-1 infection.