Comparative study of Pluronic(®) F127-modified liposomes and chitosan-modified liposomes for mucus penetration and oral absorption of cyclosporine A in rats

A Polymer Chemistry Point of View on Mucoadhesion and Mucopenetration

Although oral is the preferred route of administration of pharmaceutical formulations, the long-standing challenge for medically active compounds to efficiently cross the mucus layer barrier limits its wider applicability. Efforts in nanomedicine to overcome this hurdle consider mucoadhesive and mucopenetrating drug carriers by selectively designing (macromolecular) building blocks. This review highlights and critically discusses recent strategies developed in this context including poly(ethylene glycol)-based modifications, cationic and thiolated polymers, as well as particles with high charge density, zeta-potential shifting ability, or mucolytic properties. The latest advances in ex vivo test platforms are also reviewed.

Ciprofloxacin-loaded lipid-core nanocapsules as mucus penetrating drug delivery system intended for the treatment of bacterial infections in cystic fibrosis

Treatment of bacterial airway infections is essential for cystic fibrosis therapy. However, effectiveness of antibacterial treatment is limited as bacteria inside the mucus are protected from antibiotics and immune response. To overcome this biological barrier, ciprofloxacin was loaded into lipid-core nanocapsules (LNC) for high mucus permeability, sustained release and antibacterial activity. Ciprofloxacin-loaded LNC with a mean size of 180nm showed a by 50% increased drug permeation through mucus. In bacterial growth assays, the drug in the LNC had similar minimum inhibitory concentrations as the free drug in P. aeruginosa and S. aureus. Interestingly, formation of biofilm-like aggregates, which were observed for S. aureus treated with free ciprofloxacin, was avoided by exposure to LNC. With the combined advantages over the non-encapsulated drug, ciprofloxacin-loaded LNC represent a promising drug delivery system with the prospect of an improved antibiotic therapy in cystic fibrosis.

Aptamer-Conjugated Chitosan-Anchored Liposomal Complexes for Targeted Delivery of Erlotinib to EGFR-Mutated Lung Cancer Cells

Lung cancer is the leading cancer and has the highest death rate. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib has had a promising response in lung cancer therapy. Unfortunately, individuals with TKI-resistant EGFR mutations often develop acquired resistance against erlotinib. To overcome this resistance, in the present study, we developed liposomes anchored with anti-EGFR aptamer (Apt)-conjugated chitosan (Apt-Cs) as stable carriers to deliver erlotinib to the target. We loaded erlotinib into Apt-Cs-anchored liposomal complexes (Apt-CL-E) and characterized the physicochemistry of Apt-CL-E. The nanoparticles showed good biostability and a binding specificity for EGFR-mutated cancer cells guided by the Apt. The specific binding facilitated the uptake of Apt-CL-E into EGFR-mutated cancer cells. A cytotoxicity study showed an advantage of Apt-CL-E over their nontargeted liposomal counterparts in delivering erlotinib to EGFR-mutated cancer cells, resulting in cell cycle arrest and apoptosis. These results provide a good platform for future in vivo animal studies with Apt-CL-E.

Lipid-based nanocarriers for oral peptide delivery

This article is aimed to overview the lipid-based nanostructures designed so far for the oral administration of peptides and proteins, and to analyze the influence of their composition and physicochemical (particle size, zeta potential) and pharmaceutical (drug loading and release) properties, on their interaction with the gastro-intestinal environment, and the subsequent PK/PD profile of the associated drugs. The ultimate goal has been to highlight and comparatively analyze the key factors that may be determinant of the success of these nanocarriers for oral peptide delivery. The article ends with some prospects on the challenges to be addressed for the intended commercial success of these delivery vehicles.

Pharmacokinetic, pharmacodynamic and biodistribution following oral administration of nanocarriers containing peptide and protein drugs

The influence of nanoparticle (NP) formulations on the pharmacokinetic, pharmacodynamic and biodistribution profiles of peptide- and protein-like drugs following oral administration is critically reviewed. The possible mechanisms of absorption enhancement and the effects of the physicochemical properties of the NP are examined. The potential advantages and challenges of physiologically-based pharmacokinetic (PBPK) modelling to help predict efficacy in man are discussed. The importance of developing and expanding the regulatory framework to help translate the technology into the clinic and accelerate the availability of oral nanoparticulate formulations is emphasized. In conclusion, opportunities for future work to improve the state of the art of oral nanomedicines are identified.

Composite chitosan-transfersomal vesicles for improved transnasal permeation and bioavailability of verapamil

The creation of composite systems has become an emerging field in drug delivery. Chitosan has demonstrated several pharmaceutical advantages, especially in intranasal delivery. In this manuscript, a comparative study was conducted between regular vesicles (transfersomes and penetration enhancer vesicles) and composite vesicles (chitosan containing transfersomes and penetration enhancer vesicles) loaded with a model antihypertensive drug; verapamil hydrochloride VRP. Composite vesicles displayed larger particle size than regular vesicles owing to the coating potential of chitosan on the vesicular bilayer as displayed by transmission electron microscopy, with an increased viscosity of composite vesicles and a shift in the zeta potential values from negative to positive. The entrapment efficiency of VRP in the vesicles ranged from 24 to 64%, with best physical stability displayed with transfersomal vesicles prepared using sodium deoxycholate. Chitosan slowed the in vitro release of VRP from the selected formulation but managed to achieve high penetrability across sheep nasal mucosa as displayed by confocal laser microscopy. The chitosan composite transfersomal formulation exhibited absolute bioavailability of 81.83% compared to the oral solution which displayed only 13.04%. Findings of this manuscript highly recommend chitosan as a promising functional additive in vesicular formulations to improve the intranasal delivery of drugs with low oral bioavailability.

Pharmacological and toxicological assessment of innovative self-assembled polymeric micelles as powders for insulin pulmonary delivery

Aim: Explore the use of polymeric micelles in the development of powders intended for pulmonary delivery of biopharmaceuticals, using insulin as a model protein. Materials & methods: Formulations were assessed in vitro for aerosolization properties and in vivo for efficacy and safety using a streptozotocin-induced diabetic rat model. Results: Powders presented good aerosolization properties like fine particle fraction superior to 40% and a mass median aerodynamic diameter inferior of 6 μm. Endotracheally instilled powders have shown a faster onset of action than subcutaneous administration of insulin at a dose of 10 IU/kg, with pharmacological availabilities up to 32.5% of those achieved by subcutaneous route. Additionally, micelles improved the hypoglycemic effect of insulin. Bronchoalveolar lavage screening for toxicity markers (e.g., lactate dehydrogenase, cytokines) revealed no signs of lung inflammation and cytotoxicity 14 days postadministration. Conclusion: Developed powders showed promising safety and efficacy characteristics for the systemic delivery of insulin by pulmonary administration.

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.

Recent advances in liposome surface modification for oral drug delivery

Oral delivery via the gastrointestinal (GI) tract is the dominant route for drug administration. Orally delivered liposomal carriers can enhance drug solubility and protect the encapsulated theraputic agents from the extreme conditions found in the GI tract. Liposomes, with their fluid lipid bilayer membrane and their nanoscale size, can significantly improve oral absorption. Unfortunately, the clinical applications of conventional liposomes have been hindered due to their poor stability and availability under the harsh conditions typically presented in the GI tract. To overcome this problem, the surface modification of liposomes has been investigated. Although liposome surface modification has been extensively studied for oral drug delivery, no review exists so far that adequately covers this topic. The purpose of this paper is to summarize and critically analyze emerging trends in liposome surface modification for oral drug delivery.

Mucus-penetrating nanoparticles made with "mucoadhesive" poly(vinyl alcohol)

Nanoparticles that readily penetrate mucosal layers are desirable for a variety of biomedical applications. Nevertheless, most nanoparticles tend to be immobilized in mucus via steric and/or adhesive interactions. Contrary to the established opinion that poly(vinyl alcohol) (PVA) is mucoadhesive, we discovered that coating otherwise mucoadhesive nanoparticles with certain partially hydrolyzed PVAs can aid particle mobility in mucus. We describe two approaches to producing such mucus-penetrating particles (non-covalent modification of pre-formed nanoparticles and emulsification in the presence of PVA) and provide mobility data in human cervicovaginal mucus ex vivo as measured by multiple particle tracking and bulk permeation. When coated with PVAs that are ≥95% hydrolyzed, nanoparticles as small as ~210nm were immobilized in mucus similarly to well-established mucoadhesive controls (P>0.05). However, nanoparticles coated with PVAs that are <95% hydrolyzed penetrated mucus with velocities significantly exceeding those for the mucoadhesive controls (P<0.001) and were mobile in the bulk permeation assay.

Readily restoring freeze-dried probilosomes as potential nanocarriers for enhancing oral delivery of cyclosporine A

Formulating vesicular nanocarriers into dried precursors so as to overcome the drawbacks associated with liquid formulations is challengeable due to low efficiency of restoration. In this study, bilosomes interiorly thickened with gelatin (G-BLs) was evaluated for the ability to withstand freeze-drying stress and enhanced oral bioavailability of a model drug, cyclosporine A (CyA). The restoration efficiency of freeze-dried pro-G-BLs is investigated by comparing the particle size distribution, entrapment efficiency and morphology of the bilosomes before and after freeze-drying. Particle size and polydispersity index (PI) of pro-G-BLs after restoration was similar to that before freeze-drying, whereas freeze-dried bilosomes without gelatin thickening (pro-BLs) show irreversible damage and aggregation along with significantly increased particle size and PI after restoration. Entrapment efficiency of pro-G-BLs remains as high as 83.7%, in sharp contrast with 66.7% for pro-BLs. Pharmacokinetics in beagle dogs show improved absorption of CyA in pro-G-BLs as compared to pro-BLs, G-BLs and microemulsion-based Sandimmun Neoral(®). The relative oral bioavailability of CyA-loaded pro-G-BLs, pro-BLs and G-BLs was 165.2%, 123.5% and 130.1%, respectively, with Neoral(®) as the reference. It is concluded that interior thickening with gelatin significantly enhanced the stability against freeze-drying stress, which as a result improves the restoring efficiency and oral bioavailability.

Core–shell stability of nanoparticles plays an important role for overcoming the intestinal mucus and epithelium barrier

The stability of the core–shell structure plays an important role in the nanoparticles ability to overcome both the mucus and epithelium absorption barrier.

Mucoadhesive vs. mucopenetrating particulate drug delivery

Mucus layer is a hydrophilic absorption barrier found in various regions of the body. The use of particulate delivery systems showed potential in drug delivery to mucosal membranes by either prolonging drug residence time at the absorption or target membrane or promoting permeation of particles across mucus gel layer to directly reach underlying epithelium. Mucoadhesive particles (MAP) are advantageous for delivering drug molecules to various mucosal membranes including eyes, oral cavity, bladder and vagina by prolonging drug residence time on those membranes. In contrast, a broader particle distribution and deeper penetration of the mucus gel layer are accomplished by mucopenetrating particles (MPP) especially in the gastrointestinal tract. Based on the available literature in particular dealing with in vivo results none of both systems (MAP and MPP) seems to be advantageous over the other. The choice of system primarily depends on the therapeutic target and peculiar properties of the target mucosa including thickness of the mucus gel layer, mucus turnover rate and water movement within the mucus. Future trends are heading in the direction of combining both systems to one i.e. mucoadhesive and mucopenetrating properties on the same particles.

PEG modified liposomes containing CRX-601 adjuvant in combination with methylglycol chitosan enhance the murine sublingual immune response to influenza vaccination

The mucosa is the primary point of entry for pathogens making it an important vaccination site to produce a protective mucosal immune response. While the sublingual (SL) mucosa presents several barriers to vaccine penetration, its unique anatomy and physiology makes it one of the best options for mucosal vaccination. Efficient and directed delivery of adjuvants and antigens to appropriate immune mediators in the SL tissue will aid in development of effective SL vaccines against infectious diseases. Herein we demonstrate a robust immune response against influenza antigens co-delivered sublingually with engineered liposomes carrying the synthetic Toll-like receptor-4 agonist, CRX-601. Liposome modification with PEG copolymers (Pluronics), phospholipid-PEG conjugates and chitosan were evaluated for their ability to generate an immune response in a SL murine influenza vaccine model. Phospholipid-PEG conjugates were more effective than Pluronic copolymers in generating stable, surface neutral liposomes. SL vaccination with surface modified liposomes carrying CRX-601 adjuvant generated significant improvements in flu-specific responses compared with unmodified liposomes. Furthermore, the coating of modified liposomes with methylglycol chitosan produced the most effective flu-specific immune response. These results demonstrate efficient SL vaccine delivery utilizing a combination of a muco-adhesive and surface neutral liposomes to achieve a robust mucosal and systemic immune response.

Lipid nanoparticles for cyclosporine A administration: development, characterization, and in vitro evaluation of their immunosuppression activity

Cyclosporine A (CsA) is an immunosuppressant commonly used in transplantation for prevention of organ rejection as well as in the treatment of several autoimmune disorders. Although commercial formulations are available, they have some stability, bioavailability, and toxicity related problems. Some of these issues are associated with the drug or excipients and others with the dosage forms. With the aim of overcoming these drawbacks, lipid nanoparticles (LN) have been proposed as an alternative, since excipients are biocompatible and also a large amount of surfactants and organic solvents can be avoided. CsA was successfully incorporated into LN using the method of hot homogenization followed by ultrasonication. Three different formulations were optimized for CsA oral administration, using different surfactants: Tween(®) 80, phosphatidylcholine, taurocholate and Pluronic(®) F127 (either alone or mixtures). Freshly prepared Precirol nanoparticles showed mean sizes with a narrow size distribution ranging from 121 to 202 nm, and after freeze-drying were between 163 and 270 nm, depending on the stabilizer used. Surface charge was negative in all LN developed. High CsA entrapment efficiency of approximately 100% was achieved. Transmission electron microscopy was used to study the morphology of the optimized LN. Also, the crystallinity of the nanoparticles was studied by X-ray powder diffraction and differential scanning calorimetry. The presence of the drug in LN surfaces was confirmed by X-ray photoelectron spectroscopy. The CsA LN developed preserved their physicochemical properties for 3 months when stored at 4°C. Moreover, when the stabilizer system was composed of two surfactants, the LN formulations were also stable at room temperature. Finally, the new CsA formulations showed in vitro dose-dependent immuno-suppressive effects caused by the inhibition of IL-2 levels secreted from stimulated Jurkat cells. The findings obtained in this paper suggest that new lipid nanosystems are a good alternative to produce physicochemically stable CsA formulations for oral administration.

Investigating the role of Pluronic-g-Cationic polyelectrolyte as functional stabilizer for nanocrystals: Impact on Paclitaxel oral bioavailability and tumor growth

Paclitaxel (PTX) is a potent anticancer drug which suffers limitations of extremely low oral bioavailability due to low solubility, rapid metabolism and efflux by P-gp transporters. The main objective of this study was to overcome the limitation of PTX by designing delivery systems that can enhance the absorption using multiple pathways. A novel Pluronic-grafted chitosan (Pl-g-CH) copolymer was developed and employed as a functional stabilizer for nanocrystals (NCs) and hypothesized that it would improve PTX absorption by several mechanisms and pathways. Pl-g-CH was synthesized and characterized using (1)H NMR and then used as a stabilizer during nanocrystal development. To establish our proof of concept the optimized formulation having a particle size 192.7 ± 9.2 nm and zeta potential (+) 38.8 ± 3.12 mV was studied extensively on in vitro Caco-2 model. It was observed that nanocrystals rendered higher PTX accumulation inside the cell than Taxol™. P-gp inhibitory potential of Pl-g-CH was proved by flow cytometry and fluorescence microscopy where the much enhanced fluorescence intensity of Rhodamine 123 (Rho-123, P-gp substrate) was observed in the presence of Pl-g-CH. In addition, a significant decrease in Trans Epithelial Electrical Resistance (TEER) of Caco-2 cell monolayers was observed with nanocrystals as well as with Taxol™ (in the presence of free Pl-g-CH compared to only Taxol™). This supports the role of the stabilizer in reversible opening of tight junctions between cells which can allow paracellular transport of drug. The in vivo results were in complete corroboration with in vitro results. Nanocrystals resulted in much enhanced absorption with 12.6-fold improvement in relative bioavailability to that of Taxol™. Concomitantly efficacy data in B16 F10 murine melanoma model also showed a significant reduction in tumor growth with nanocrystals compared to Taxol™ and control. Based on the results it can be suggested that nanocrystals with functional stabilizers can be a promising approach for the oral delivery of anticancer drugs which are P-gp substrates

STATEMENT OF SIGNIFICANCE

Nanocrystals are currently one of the most explored novel drug delivery systems especially for oral delivery of drugs because of ease in synthesis and high drug loading. But their use is still limited for oral delivery of anticancer drugs which are P-gp substrates. This particular study aims at widening the scope of nanocrystals by using a functional stabilizer which participates in enhancing the oral absorption of anticancer drugs and controlling the tumor growth.

Improved stability and skin permeability of sodium hyaluronate-chitosan multilayered liposomes by Layer-by-Layer electrostatic deposition for quercetin delivery

Layer-by-Layer (LbL) technology, based on the electrostatic interaction of polyelectrolytes, is used to improve the stability of drug delivery systems. In the present study, we developed multilayered liposomes with up to 10 alternating layers based on LbL deposition of hyaluronate-chitosan for transdermal delivery. Dihexadecyl phosphate was used to provide liposomes with a negative charge; the liposomes were subsequently coated with cationic chitosan (CH) followed by anionic sodium hyaluronate (HA). The resulting particles had a cumulative size of 528.28±29.22nm and an alternative change in zeta potential. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) revealed that the multilayered liposomes formed a spherical polyelectrolyte complex (PEC) after deposition. Observations in size distribution after 1 week found that the particles coated with even layers of polyelectrolytes, hyaluronate and chitosan (HA-CH), were more stable than the odd layers. Membrane stability in the presence of the surfactant Triton X-100 increased with an increase in bilayers as compared to uncoated liposomes. An increase in the number of bilayers deposited on the liposomal surface resulted in a sustained release of quercetin, with release kinetics that fit the Korsmeyer-Peppas model. In an in vitro skin permeation study, negatively charged (HA-CH)-L and positively charged CH-L were observed to have similar skin permeability, which were superior to uncoated liposomes. These results indicate that multilayered liposomes properly coated with polyelectrolytes of HA and CH by electrostatic interaction improve stability and can also function as potential drug delivery system for the transdermal delivery of the hydrophobic antioxidant quercetin.

Effect of surface chemistry on nanoparticle interaction with gastrointestinal mucus and distribution in the gastrointestinal tract following oral and rectal administration in the mouse

It is believed that mucoadhesive surface properties on particles delivered to the gastrointestinal (GI) tract improve oral absorption or local targeting of various difficult-to-deliver drug classes. To test the effect of nanoparticle mucoadhesion on distribution of nanoparticles in the GI tract, we orally and rectally administered nano- and microparticles that we confirmed possessed surfaces that were either strongly mucoadhesive or non-mucoadhesive. We found that mucoadhesive particles (MAP) aggregated in mucus in the center of the GI lumen, far away from the absorptive epithelium, both in healthy mice and in a mouse model of ulcerative colitis (UC). In striking contrast, water absorption by the GI tract rapidly and uniformly transported non-mucoadhesive mucus-penetrating particles (MPP) to epithelial surfaces, including reaching the surfaces between villi in the small intestine. When using high gavage fluid volumes or injection into ligated intestinal loops, common methods for assessing oral drug and nanoparticle absorption, we found that both MAP and MPP became well-distributed throughout the intestine, indicating that the barrier properties of GI mucus were compromised. In the mouse colorectum, MPP penetrated into mucus in the deeply in-folded surfaces to evenly coat the entire epithelial surface. Moreover, in a mouse model of UC, MPP were transported preferentially into the disrupted, ulcerated tissue. Our results suggest that delivering drugs in non-mucoadhesive MPP is likely to provide enhanced particle distribution, and thus drug delivery, in the GI tract, including to ulcerated tissues.

Chitosan-coated nano-liposomes for the oral delivery of berberine hydrochloride

Berberine hydrochloride (BH) possesses various pharmacological properties including anticancer; unfortunately, it has low oral bioavailability and potential side effects for its parenteral administration. Nanoscale delivery carriers can increase the oral bioavailability of BH. Chitosan has interesting biopharmaceutical properties such as nontoxicity, biocompatibility, biodegradability, and mucoadhesiveness, and the ability to open epithelial tight junctions. This study aims to engineer a chitosan-coated nano-liposomal carrier for the oral delivery of BH. The engineered formulation had a size in the nanoscale range. Chitosan-coated nano-liposomes displayed better stability and slower BH release in the simulated gastrointestinal (GI) environment as compared to the uncoated ones. All values of pharmacokinetic analysis for chitosan-coated nano-liposomes were higher than for uncoated ones. These findings demonstrate that chitosan-coated nano-liposomes are more efficient than uncoated ones for the oral delivery of BH. It can be concluded that the stability and delayed BH release in the simulated GI environment were improved with engineered chitosan-coated nano-liposomes. Moreover, since desirable in vitro and in vivo characteristics were achieved, they are promising release devices for the oral delivery of BH increasing the bioavailability of the drug.

Liposomes interiorly thickened with thermosensitive nanogels as novel drug delivery systems

The fundamental structure of liposomes suffers from drawbacks of physical instability. To overcome this problem, the hypothesis of this study was to thicken the liposomal interior by incorporating thermosensitive in situ gel. The so called gelliposomes (GLs) were prepared by a thin-film method using poloxamer solutions as interior aqueous phase. Interior thermosensitive gelation was proved by observation of sustained dissolving of the poloxamer gel after destroying the lipid bilayers with Triton X-100; structural transformation as observed under optical microscopy in a heating-cooling circle also proved the fact of interior gelling. The sol-gel transition temperatures of GLs were in good correlation with those of the bulk poloxamer solution counterparts, which could be easily tailored by adjusting the concentration and ratio of poloxamer 407 (P407) to poloxamer 188 (P188). Membrane anisotropy measurement indicated increased membrane rigidity. In vitro release of the model drug cytosine arabinoside from GLs showed sustained release characteristics for at least one week with typical biphasic kinetics. Study on storage stability and protection against the destroying effect by membrane destroyers indicated improved physical stability in comparison with conventional liposomes. In situ evading of phagocytic uptake by macrophages was observed for GLs, which however should be attributed to the effect of exteriorly adsorbed poloxamers. In conclusion, GLs present distinct characteristics to be used as potential drug delivery systems.