Liposomes interiorly thickened with thermosensitive nanogels as novel drug delivery systems

Lyophilized liposomal formulation of a peptidomimetic-Dox conjugate for HER2 positive breast and lung cancer

Nanocarrier-mediated administration of chemotherapeutic drugs can increase the therapeutic index of drugs by reducing off-target site toxicity. Ligand-targeted drug delivery can be utilized to deliver chemotherapeutic drugs to cancer cells selectively and specifically. Here we report the evaluation of a lyophilized formulation of a liposome containing a peptidomimetic-doxorubicin conjugate for targeted delivery of doxorubicin to HER2-positive cancer cells. The lyophilized liposomal formulation exhibited improved release of peptidomimetic-doxorubicin conjugate at pH 6.5 compared to 7.4 and improved cellular uptake in cancer cells at pH 6.5. In vivo studies indicated that pH-sensitive formulation exhibited site-specific formulation delivery and improved anticancer efficacy than free doxorubicin. The findings suggested that combining a lyophilized pH-sensitive liposomal formulation containing trehalose as lyoprotectant with a targeting ligand coupled cytotoxic agent is a potential method for cancer chemotherapy while maintaining long-term stability at 4°C of the liposome formulation.

Exploring a Novel Fasudil-Phospholipid Complex Formulated as Liposomal Thermosensitive in situ Gel for Glaucoma

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"Plurethosome" as Vesicular System for Cutaneous Administration of Mangiferin: Formulative Study and 3D Skin Tissue Evaluation

Human skin is dramatically exposed to toxic pollutants such as ozone. To counteract the skin disorders induced by the air pollution, natural antioxidants such as mangiferin could be employed. A formulative study for the development of vesicular systems for mangiferin based on phosphatidylcholine and the block copolymer pluronic is described. Plurethosomes were designed for mangiferin transdermal administration and compared to ethosome and transethosome. Particularly, the effect of vesicle composition was investigated on size distribution, inner and outer morphology by photon correlation spectroscopy, small angle X-ray diffraction, and transmission electron microscopy. The potential of selected formulations as vehicles for mangiferin was studied, evaluating encapsulation efficiency and in vitro diffusion parameters by Franz cells. The mangiferin antioxidant capacity was verified by the 2,2-diphenyl-1-picrylhydrazyl assay. Vesicle size spanned between 200 and 550 nm, being influenced by phosphatidylcholine concentration and by the presence of polysorbate or pluronic. The vesicle supramolecular structure was multilamellar in the case of ethosome or plurethosome and unilamellar in the case of transethosome. A linear diffusion of mangiferin in the case of ethosome and transethosomes and a biphasic profile in the case of plurethosomes indicated the capability of multilamellar vesicles to retain the drug more efficaciously than the unilamellar ones. The antioxidant and anti-inflammatory potential effect of mangiferin against pollutants was evaluated on 3D human skin models exposed to O3. The protective effect exerted by plurethosomes and transethosomes suggests their possible application to enhance the cutaneous antioxidant defense status.

Viscous Core Liposomes Increase siRNA Encapsulation and Provides Gene Inhibition When Slightly Positively Charged

Since its discovery, evidence that siRNA was able to act as an RNA interference effector, led to its acceptation as a novel medicine. The siRNA approach is very effective, due to its catalytic mechanism, but still the limitations of its cellular delivery should be addressed. One promising form of non-viral gene delivery system is liposomes. The variable and versatile nature of the lipids keeps the possibility to upgrade the liposomal structure, which makes them suitable for encapsulation and delivery of drugs. However, to avoid the limitation of fast release for the hydrophilic drug, we previously designed viscous core liposomes. We aimed in this work to evaluate if these viscous core liposomes (NvcLs) could be of interest for siRNA encapsulation. Then, we sought to add a limited amount of positive charges to provide cell interaction and transfection. Cationic lipid dimyristoylaminopropylaminopropyl or the polymer poly(ethylenimine) were incorporated in NvcL to produce positively charged viscous core liposomes (PvcL) by a customized microfluidic device. We found that NvcLs increased the encapsulation efficiency and loading content with regards to the neutral liposome. Both PvcL_PEI and PvcL_DMAPAP exhibited transfection and GFP knock-down (≈40%) in both 2D and 3D cell cultures. Finally, the addition of slight positive charges did not induce cell toxicity.

Advancement in nanogel formulations provides controlled drug release

Nanogels are currently considered as promising nanosized drug delivery carriers. Nanogels are made of a crosslinked polymeric network which could encapsulate both hydrophilic and hydrophobic drugs due to their tunable nature. The ability of nanogels to control drug release is vastly described in the literature and researchers are consistently improving the control of drug release from nanogel by designing new polymers having specific sensitivity to a chemical or physical stimulus. In this review, we briefly discuss the definition of nanogels, their release profiles, their specific gel-based characteristics and the pathways of dug release from nanogels. We have focused on the stimuli responsive nanogels and their release profile. This compilation opens the window for understanding the influence of chemical composition and design of various nanogel on their release in the presence and absence of corresponding stimuli such as temperature, pH, enzymes and others. The uniqueness of this review is that it highlights the data of release profiles in terms of the different nanogel composition and triggers. It also points the high potential of nanogels in the list of candidates for drug delivery systems, thanks to their properties regarding drug encapsulation and release, combined advantages of nano-size and swelling characteristics of hydrogel.

Liposome-Enveloped Molecular Nanogels

Novel hydrogel@liposome particles were prepared by pH-triggered molecular gel formation inside of liposomes loaded with a low-molecular weight gelator derived from l-valine (1). Liposome formation was carried out using l-α-phosphatidylcholine (PC) and cholesterol as components of the lipid bilayer. Molecular hydrogelator 1 and pyranine, a ratiometric fluorescent pH probe, were entrapped in the liposomes at pH 9 and posterior acidification with d-glucono-1,5-lactone to pH 5-6 provoked intraliposomal gel formation. Removal of the lipid bilayer with sodium dodecyl sulfate yielded naked nanogel particles. The systems were characterized by transmission electron microscopy and dynamic light scattering. The hydrogel@liposomes were loaded with doxorubicin, showing a similar release than that observed for liposomes. The hybrid particles described here are the first case of nonpolymeric hydrogel@liposome systems reported. This type of nanocarriers merges the benefits of liposomal vehicles with the inherent stimuli responsiveness and enhanced biocompatibility of hydrogels formed by low-molecular weight molecules, foretelling a potential use in environmentally sensitive drug release.

Conception of nanosized hybrid liposome/poloxamer particles to thicken the interior core of liposomes and delay hydrophilic drug delivery

Liposomes are nanocarriers composed of phospholipids, especially designed to potentially carry drugs. However, liposomes suffer in terms of leakage of small hydrophilic drugs. To control the release, a system with lipid shell and polymeric viscous core, namely Hybrid liposome/polymer inside (HLP_in), has been designed. For this purpose, we setup a syringe pump apparatus equipped with homemade tubing system. HLPin formulation consisting of poloxamer (5% w/v) was found to be optimal when produced at injection rates of 5 mL.min^-1. Then, we tend to characterize the HLP_in with DLS, TEM, TRPS, thermal analysis and densitometry in comparison with a polymer added after formation of the liposomes. The optimal formulation was evaluated for its stability and cytotoxicity. The selected conditions and composition resulted in nanocarriers which are highly reproducible with mono-disperse size distribution with an average size of 206 ± 4.8 nm and a polydispersity index of 0.15 ± 0.015. Densitometry and thermal analysis results confirmed the formation of HLP_in. Interestingly, HLP_in were stable over 2 months, produced no cytotoxicity and exhibited slow release of rhodamine and Doxorubicin in comparison to liposome formulation. Our homemade tubing system coupled with syringe pump apparatus achieved reproducible, precisely controlled production for the HLPin formulation which can be scale up.

Adapting liposomes for oral drug delivery

Liposomes mimic natural cell membranes and have long been investigated as drug carriers due to excellent entrapment capacity, biocompatibility and safety. Despite the success of parenteral liposomes, oral delivery of liposomes is impeded by various barriers such as instability in the gastrointestinal tract, difficulties in crossing biomembranes, and mass production problems. By modulating the compositions of the lipid bilayers and adding polymers or ligands, both the stability and permeability of liposomes can be greatly improved for oral drug delivery. This review provides an overview of the challenges and current approaches toward the oral delivery of liposomes.

Evidence of nose-to-brain delivery of nanoemulsions: cargoes but not vehicles

The nose-to-brain pathway has been proven to be a shortcut for direct drug delivery to the brain. However, whether and to what extent nanoparticles can be delivered through this passage is still awaiting validation with evidence. In this study, nose-to-brain transportation of nanoparticles is tracked via fluorescence bioimaging strategies using nanoemulsions (NEs) as model carriers. Identification of NEs in biological tissues is based on the on → off signal switching of a new type of environment-responsive embedded dyes, P2 and P4, and two conventional probes, DiR and coumarin-6 (C6), are embedded to represent the cargoes. Evidence for the translocation of NEs was collected either via live imaging or ex vivo histological examination in rats after nasal administration. Results suggest that NEs with a particle size of about 100 nm, either naked or coated with chitosan, have longer retention duration in nostrils and slower mucociliary clearance than larger ones. P2 signals, representing integral NEs, can be found in mucosa and trigeminal nerves for all size groups, whereas only weak P2 signals are detected in the olfactory bulb for chitosan-coated NEs of 100 nm. Confocal microscopy further confirms the translocation of integral 100 nm NEs in nasal mucosa and along the trigeminal nerve in decremental intensity. Weak signals of the P4 probe, also representing integral NEs, can be detected in the olfactory bulb but few in the brain. NEs as large as 900 nm cannot be transported to the olfactory bulb. However, the DiR or C6 signals that represent the cargoes can be found in significant amounts along the nose-to-brain pathway and finally reach the brain. Evidence shows that integral NEs can be delivered to the olfactory bulb, but few to the brain, whereas the cargoes can be released and permeated into the brain in greater amounts.

Preparation and Evaluation of Oxaliplatin Thermosensitive Liposomes with Rapid Release and High Stability

Oxaliplatin (OXP) was reported to show low anti-tumor activity when used alone and to display side effects; this low activity was attributed to high partitioning to erythrocytes and low accumulation in tumors. Thermosensitive liposomes (TSL) were considered able to specifically deliver drugs to heated tumors and to resolve the OXP distribution problem. Regretfully, TSL encapsulating doxorubicin did not demonstrate significant improvement in progression-free survival. Drug release below 41°C and significant leakage were considered major reasons for the failure. The purpose of this study was to acquire OXP TSL with rapid release at the triggered temperature and high stability at body temperature and at storage temperatures. A small quantity of poloxamer 188 was introduced into the TSL formulation to stabilize the encapsulated drug. It was shown that the addition of poloxamer 188 had no influence on the TSL characteristics. More than 90% of OXP was released within 10 min at 42°C, and less than 15% was released within 60 min at temperatures below 39°C. TSL were stable at 37°C for 96 h and at 4°C for 6 months. The anti-tumor activity of TSL at the dose of 2.5 mg/kg was certified to be equal to those of OXP injection and non-thermosensitive liposomes (NTSL) at the dose of 5 mg/kg, and significant improvement of tumor inhibition was observed in TSL compared with injection and NTSL at the same dose. It was also shown from the histological transmutation of tumors that TSL had stronger anti-tumor activity. Therefore, it could be concluded that TSL composed of a proper amount of poloxamer had rapid release and high stability, and OXP TSL would be anticipated to exert prominent anti-tumor activity in the clinic.

Glucan microparticles thickened with thermosensitive gels as potential carriers for oral delivery of insulin

Although glucan microparticles (GMs) can be efficiently taken up and transported by M cells, their subsequent accumulation in lymphatic tissues of sub-follicle-associated epithelia (FAE) in Peyer's patches might present a barrier to the oral delivery of insulin by GMs into the systemic circulation. The goal of this study is to weigh the potential of GMs as carriers for oral delivery of systemic therapeutics using insulin (INS) as a model drug. INS is encapsulated into the inner cavities of GMs by repeated soaking in INS solution at acidic pH values and switching to an isoelectric pH of 5.6 to precipitate INS. To immobilize INS, a thermosensitive poloxamer 407 (P407) gel is introduced into the interior of GMs. Interiorly thickened GMs show significantly decreased in vitro release and well protected INS stability against enzyme-enriched media, highlighting the importance of thickening with P407 gels. A mild and prolonged hypoglycaemic effect is achieved in both normal and diabetic rats for a duration of at least 20 h with pharmacological bioavailability as high as about 9-10%. Lymphatic transportation of GMs is investigated by labelling with a near-infrared water-quenching fluorescent probe in a conscious mesentery lymphatic duct cannulation rat model following oral administration. GMs appear in lymph within the first 2 h, peak at around 6 h and slow down after 10 h with a cumulative amount of over 8% in 24 h. The high correlation between lymphatic transportation and pharmacological bioavailability implies that GMs are principally absorbed via the lymphatic route. An in vitro study on phagocytosis by macrophages confirms the easy and fast uptake of GMs by J774A.1 cell lines with as many as over 10 particles within the cytoplasm of a single cell. Intracellular pharmacokinetics indicates robustness and persistent residence of GMs within the cells. Little effect on cell viability and tight junctions was observed in Caco-2 cell models. It is concluded that GMs are mainly absorbed via the lymphatic route and show potential as carriers for oral delivery of labile therapeutics, though with limited bioavailability due to the sub-FAE residence barriers.

Core-shell structured gel-nanocarriers for sustained drug release and enhanced antitumor effect

The present paper attempted to develop temperature-sensitive and core-shell structured gel-nanocarriers (gel-NCs) for paclitaxel (PTX) with 12-hydroxystearic acid (12-HSA) as an organic gelator, which aims at sustaining drug release over time and thus improves the therapeutic effect. The gel-NCs were prepared by a mechanical mixing and high-pressure homogenization method. The gelation transition temperature (Tgel) of the organic phase contained in the cores of the gel-NCs was optimized by a stirring method. The gel-NCs were characterized in terms of the particle size, morphology and in vitro drug release. The in vivo studies, including the antitumor effects on H22 tumor-bearing mice, biocompatibility and toxicity in mice, were performed. Gel-NCs with approximately 170 nm were prepared successfully, and the gelation of the liquid cores at 37°C was achieved, while the amount of gelator was 3.75% (w/w). Due to the gelation of the cores, sustained drug release over time was obtained. Moreover, the PTX-loaded gel-NCs suppressed tumor growth more efficiently than the conventional nanocarriers with better in vivo biocompatibility and no toxicity to other healthy organs. In conclusion, the 12-HSA organogel-based NCs appear to be promising systems for the sustained release of active compounds for a long time and thus improve the therapeutic outcome.

Liposome incorporated ion sensitive in situ gels for opthalmic delivery of timolol maleate

This study was aimed to design a liposomal based ion-sensitive in situ ophthalmic delivery system of timolol maleate (TM). The TM liposome was produced by the reverse evaporation technique coupled with pH-gradients method (REVPR), and then was incorporated into deacetylated gellan gum gels. The TM liposome was demonstrated to be a round and uniform shape in TEM pictures. Compared with the TM eye drops, the TM liposome produced a 1.93 folds increase in apparent permeability coefficients (Papp), resulting in a significant increase of the corneal penetration. The TM-loaded liposome incorporated ion sensitive in situ gels (TM L-ISG) showed longer retention time on corneal surface compared with the eye drops using gamma scintigraphy technology. Draize testing showed that TM L-ISG was non-irritant for ocular tissues. The biggest efficacy of TM L-ISG occurred 30 min after eye drops administration, and efficacy disappeared after 240min. Then, compared with the eye drops, the optimal TM L-ISG could quickly reduce the intraocular pressure and the effective time was significantly longer (P≤0.05). These results indicate that liposome incorporated ion sensitive in situ gels have a potential ability for the opthalmic delivery.

Solidification of liposomes by freeze-drying: the importance of incorporating gelatin as interior support on enhanced physical stability

The main purpose of this study was to investigate the effect of gelatin as interior support on the physical stability of freeze-dried liposomes. Anticancer agent paclitaxel (PTX) was selected as a model drug. Freeze-dried liposomes containing interior gelatin support (GLs) were prepared by thin-film dispersion/freeze-drying method. Several properties of the GLs, including entrapment efficiency, particle size and gelation temperature, were extensively characterized. Encapsulation efficiency of conventional liposomes (CLs) and liposomes containing lyoprotectants as interior support dropped to lower than 20% after reconstitution, while GLs still maintained an entrapment efficiency of over 84%. Scanning electron microscopy revealed well preserved liposomal structure of GLs after reconstitution. Meanwhile, the particle size and entrapment efficiency of GLs were also well preserved after reconstitution. In contrary, deformation of CLs and recrystallization of PTX were observed, as well as significant changes in particle size and entrapment efficiency. Taken together, interior gelatin support obviously enhanced the physical stability of liposomes against the lyophilization stress.