Liposomes as a topical delivery system: the role of size on transport studied by the EPR imaging method

Development and pharmacological evaluation of liposomes and nanocapsules containing paroxetine hydrochloride

Depression is one of the most common psychiatric disorders. Nanotechnology has emerged to optimize the pharmacological response. Therefore, the aim of this work was to develop and characterize liposomes and nanocapsules containing paroxetine hydrochloride and evaluate their antidepressant-like effect using the open field and tail suspension tests in mice. Liposomes and nanocapsules were prepared using the reverse-phase evaporation and nanoprecipitation methods, respectively. The particle size of the formulation ranged from 121.81 to 310.73 nm, the polydispersity index from 0.096 to 0.303, the zeta potential from -11.94 to -34.50 mV, the pH from 5.31 to 7.38, the drug content from 80.82 to 94.36 %, and the association efficiency was 98 %. Paroxetine hydrochloride showed slower release when associated with liposomes (43.82 %) compared to nanocapsules (95.59 %) after 10 h. In Vero cells, in vitro toxicity showed a concentration-dependent effect for paroxetine hydrochloride nanostructures. Both nanostructures decreased the immobility time in the TST at 2.5 mg/kg without affecting the number of crossings in the open field test, suggesting the antidepressant-like effect of paroxetine. In addition, the nanocapsules decreased the number of groomings, reinforcing the anxiolytic effect of this drug. These results suggest that the nanostructures were effective in preserving the antidepressant-like effect of paroxetine hydrochloride even at low doses.

Gemcitabine-Lipid Conjugate and ONC201 Combination Therapy Effectively Treats Orthotopic Pancreatic Tumor-Bearing Mice

Gemcitabine (GEM) is a nucleoside analogue approved as a first line of therapy for pancreatic ductal adenocarcinoma (PDAC). However, rapid metabolism by plasma cytidine deaminase leading to the short half-life, intricate intracellular metabolism, ineffective cell uptake, and swift development of chemoresistance downgrades the clinical efficacy of GEM. ONC201 is a small molecule that inhibits the Akt and ERK pathways and upregulates the TNF-related apoptosis-inducing ligand (TRAIL), which leads to the reversal of both intrinsic and acquired GEM resistance in PDAC treatment. Moreover, the pancreatic cancer cells that were able to bypass apoptosis after treatment of ONC201 get arrested in the G1-phase, which makes them highly sensitive to GEM. To enhance the in vivo stability of GEM, we first synthesized a disulfide bond containing stearate conjugated GEM (lipid-GEM), which makes it sensitive to the redox tumor microenvironment (TME) comprising high glutathione levels. In addition, with the help of colipids 1,2-dioleoyl-glycero-3-phosphocholine (DOPC), cholesterol, and 1,2-distearoyl-glycero-3-phosphoethanolamine-poly(ethylene glycol)-2000 (DSPE-PEG 2000), we were able to synthesize the lipid-GEM conjugate and ONC201 releasing liposomes. A cumulative drug release study confirmed that both ONC201 and GEM showed sustained release from the formulation. Since MUC1 is highly expressed in 70-90% PDAC, we conjugated a MUC1 binding peptide in the liposomes which showed higher cytotoxicity, apoptosis, and cellular internalization by MIA PaCa-2 cells. A biodistribution study further confirmed that the systemic delivery of the liposomes through the tail vein resulted in a higher accumulation of drugs in orthotopic PDAC tumors in NSG mice. The IHC of the excised tumor grafts further confirmed the higher apoptosis and lower metastasis and cell proliferation. Thus, our MUC1 targeting binary drug-releasing liposomal formulation showed higher drug payload, enhanced plasma stability, and accumulation of drugs in the pancreatic orthotopic tumor and thus is a promising therapeutic alternative for the treatment of PDAC.

Application of biomacromolecule-based passive penetration enhancement technique in superficial tumor therapy: A review

Transdermal drug delivery (TDD) has shown great promise in superficial tumor therapy due to its noninvasive and avoidance of the first-pass effect. Especially, passive penetration enhancement technique (PPET) provides the technical basis for TDD by temporarily altering the skin surface structure without requiring external energy. Biomacromolecules and their derived nanocarriers offer a wide range of options for PPET development, with outstanding biocompatibility and biodegradability. Furthermore, the abundant functional groups on biomacromolecule surfaces can be modified to yield functional materials capable of targeting specific sites and responding to stimuli. This enables precise drug delivery to the tumor site and controlled drug release, with the potential to replace traditional drug delivery methods and make PPET-related personalized medicine a reality. This review focuses on the mechanism of biomacromolecules and nanocarriers with skin, and the impact of nanocarriers' surface properties of nanocarriers on PPET efficiency. The applications of biomacromolecule-based PPET in superficial tumor therapy are also summarized. In addition, the advantages and limitations are discussed, and their future trends are projected based on the existing work of biomacromolecule-based PPET.

Preparation of luteolin loaded nanostructured lipid carrier based gel and effect on psoriasis of mice

This study investigated a nanostructured lipid carrier (NLC)-gel system containing luteolin (LUT), a potential drug delivery system for the treatment of psoriasis. LUT-NLC was prepared by solvent emulsification ultrasonication method. The particle size was 199.9 ± 2.6 nm, with the encapsulation efficiency of 99.81% and drug loading of 4.06%. X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to characterize the LUT-NLC. The NLC was dispersed in Carbomer 940 to form the NLC based gel. The rheological characteristics of LUT-NLC-gel showed an excellent shear-thinning behavior (non-Newtonian properties) and coincided with the Herschel-Bulkley model. LUT-NLC-gel (78.89 μg/cm2) exhibited better permeation properties and released over 36 hours than LUT gel (32.17 μg/cm2). The dye-labeled LUT-NLC presented intense fluorescence in the epidermis and dermis by the visualization of fluorescence and confocal microscopy, and it could accumulate in the hair follicles. The effect of LUT-NLC-gel on imiquimod-induced psoriasis mice was evaluated by psoriasis area severity index scoring, spleen index assay, histopathology, and inflammatory cytokines. These results confirmed that LUT-NLC-gel with high dose (80 mg/kg/day) remarkably reduced the level of inflammatory and proliferation factors such as TNF-α, IL-6, IL-17, and IL-23 in both skin lesions and blood. LUT-NLC-gel improved the macroscopic features. Therefore, the LUT-NLC-gel had great potential as an effective delivery system for skin diseases.

Tioconazole-Loaded Transethosomal Gel Using Box-Behnken Design for Topical Applications: In Vitro, In Vivo, and Molecular Docking Approaches

Tioconazole (TCZ) is a broad-spectrum fungicidal BCS class II drug with reported activity against Candida albicans, dermatophytes, and certain Staphylococci bacteria. We report the use of TCZ-loaded transethosomes (TEs) to overcome the skin's barrier function. TCZ-loaded TEs were fabricated by using a cold method with slight modification. Box-Behnken composite design was utilized to investigate the effect of independent variables. The fabricated TEs were assessed with various physicochemical characterizations. The optimized formulation of TCZ-loaded TEs was incorporated into gel and evaluated for pH, conductivity, drug content, spreadability, rheology, in vitro permeation, ex vivo permeation, and in vitro and in vivo antifungal activity. The fabricated TCZ-loaded TEs had a % EE of 60.56 to 86.13, with particle sizes ranging from 219.1 to 757.1 nm. The SEM images showed spherically shaped vesicles. The % drug permeation was between 77.01 and 92.03. The kinetic analysis of all release profiles followed Higuchi's diffusion model. The FTIR, DSC, and XRD analysis showed no significant chemical interactions between the drug and excipients. A significantly higher antifungal activity was observed for TCZ-loaded transethosomal gel in comparison to the control. The in vivo antifungal study on albino rats indicated that TCZ-loaded transethosomal gel showed a comparable therapeutic effect in comparison to the market brand Canesten®. Molecular docking demonstrated that the TCZ in the TE composition was surrounded by hydrophobic excipients with increased overall hydrophobicity and better permeation. Therefore, TCZ in the form of transethosomal gel can serve as an effective drug delivery system, having the ability to penetrate the skin and overcome the stratum corneum barrier with improved efficacy.

Skin drug delivery using lipid vesicles: A starting guideline for their development

Lipid vesicles can provide a cost-effective enhancement of skin drug absorption when vesicle production process is optimised. It is an important challenge to design the ideal vesicle, since their properties and features are related, as changes in one affect the others. Here, we review the main components, preparation and characterization methods commonly used, and the key properties that lead to highly efficient vesicles for transdermal drug delivery purposes. We stand by size, deformability degree and drug loading, as the most important vesicle features that determine the further transdermal drug absorption. The interest in this technology is increasing, as demonstrated by the exponential growth of publications on the topic. Although long-term preservation and scalability issues have limited the commercialization of lipid vesicle products, freeze-drying and modern escalation methods overcome these difficulties, thus predicting a higher use of these technologies in the market and clinical practice.

Bioavailability enhancement of voriconazole using liposomal pastilles: Formulation and experimental design investigation

Oral mucosa offers several advantages in the delivery of therapeutic molecules. It avoids presystemic metabolism, Nanoencapsulation techniques might be applied to conquer physical, chemical challenges and enhance drug penetration, formulation performance, prolonging drug residence time, and improving sensorial feeling. The present investigation is aimed to formulate liposomal pastilles with high bioavailability. Voriconazole Liposomes (VL) were produced by utilizing varied ratios of soya lecithin (SL) and cholesterol (CH) by solvent Injection method. RSM is utilized to identify the optimized formulation, as this design provides a thorough understanding of a process and also has great utilization in originating the robustness of the product. The main impact and interaction terms of the formulation variables were assessed quantitatively utilizing a mathematical-statistical approach indicating that both independent variables have significant ('P' value < 0.05) effects on particle size ('P' value: 0.0142), percentage entrapment efficiency ('P' value: 0.0120), percentage drug release through the dialysis membrane ('P' value: 0.0105), percentage drug release through porcine buccal mucosa ('P' value: 0.0171) and percentage zone of inhibition ('P' value: 0.0305). Optimal liposomal encapsulated in noticed in 15:10 lecithin: cholesterol concentration (VLP-6). Higher Lecithin and Cholesterol quantity in the liposome formulations resulted in lower drug entrapment efficiency and drug release when compared with middle levels of lecithin and cholesterol content formulation. The pastilles were prepared from the optimized liposomal formulation with a modified method reported in British Pharmaceutical Codex, 1907. These liposomal pastilles were subjected to evaluation of physicochemical parameters, In vitro drug release studies, stability studies, and In vivo bioavailability studies in comparison with pure voriconazole pastilles (PVP). The statistical data analysis results indicated that there was a significant difference in T_max, K_a, t_{1/2 abs}, t_{1/2 elim,} AUC_0-24, AUC_0-∞, AUMC_0-24 and AUMC_0-∞, values among PVP and VLP-6. There was no significant difference in C_max, K_el, MRT_0-24 and MRT_0-∞values among pure voriconazole pastilles and optimized liposomal formulation.

Transdermal Delivery of Telmisartan: Formulation, in vitro, ex vivo, Iontophoretic Permeation Enhancement and Comparative Pharmacokinetic Study in Rats

Purpose

The purpose of this study was to prepare telmisartan transethosomes, incorporate them into a gel, evaluate them for in vitro drug release and in vivo permeation using iontophoresis to enhance their transdermal delivery.

Materials and Methods

TE formulae were prepared using various surfactants (SAAs), different ethanol concentrations, and different phospholipid-to-SAA ratios with different cholesterol ratios, characterized according to their entrapment efficiency percentage (EE%), zeta potential (ZP), particle size (PS), and polydispersity index (PDI). The optimum three formulae were incorporated into a gel, evaluated physically, in vitro dissolution, and ex vivo drug permeation using rat skin and Iontophoresis was performed on the best formula.

Results

The optimum three formulae (F29, F31, F32) had an EE% of 97±0.26%, 89±0.25% and 88±0.17%, PS of 244±5.88 nm, 337±4.6 nm and 382.2±3.06 nm, PDI of 0.57±1.9, 0.5±1.4 and 0.63±2.2 and ZP of −31.6±1.59 mV, −28.3±3.79 mV and −31±5.65, respectively. Selecting F29 for in vivo study by iontophoretic enhancement, Cmax was increased by 1.85 folds compared to the commercial oral tablet and by 1.5 folds compared to transdermal gel. Tmax decreased by half using iontophoresis compared to commercial tablets and transdermal gel.

Conclusion

The transethosomal formulation of telmisartan enhanced its transdermal absorption and increased its bioavailability as well. Iontophoresis was used to increase maximum plasma concentration and reduce Tmax by half.

Size-Dependent Absorption through Stratum Corneum by Drug-Loaded Liposomes

PURPOSE

Topical treatment of various skin disorders requires drug absorption and penetration through the stratum corneum (SC) into the epidermis and dermis tissues. The use of nano-drug delivery systems including liposomes and lipid nanoparticles (SLNs) have been shown to facilitate SC penetration. The goal of this work was to study the impact of liposome sizes and the resulted drug distribution inside various skin tissue.

METHODS

All trans retinoic acid (ATRA) was used as the model drug and loaded into gel phase HSPC/CHOL/DSPE-PEG liposomes (lipo-ATRA) with sizes ranging from 80 nm to more than 300 nm. The percutaneous drug absorption process was monitored and analyzed.

RESULTS

There were significant differences in percutaneous absorption and tissue distribution resulted from liposomes smaller than 100 nm and those bigger than 200 nm. Lipo-ATRA with a mean diameter of 83 nm can deliver the content to epidermis and dermis. But for 200 nm - 300 nm liposomes, the resulted epidermis and dermis ATRA levels were less than about one third, suggesting bigger liposomes had poor penetration through the brick and mortar structure of SC.

CONCLUSIONS

Gel phase liposomes with sizes under 100 nm improved encapsulated drug absorption and distribution into the epidermis and dermis tissues. A size dependent mechanism for liposome penetration of the stratum corneum was proposed.

Continuous-Flow Production of Liposomes with a Millireactor under Varying Fluidic Conditions

Continuous-flow production of liposomes using microfluidic reactors has demonstrated advantages compared to batch methods, including greater control over liposome size and size distribution and reduced reliance on post-production processing steps. However, the use of microfluidic technology for the production of nanoscale vesicular systems (such as liposomes) has not been fully translated to industrial scale yet. This may be due to limitations of microfluidic-based reactors, such as low production rates, limited lifetimes, and high manufacturing costs. In this study, we investigated the potential of millimeter-scale flow reactors (or millireactors) with a serpentine-like architecture, as a scalable and cost-effective route to the production of nanoscale liposomes. The effects on liposome size of varying inlet flow rates, lipid type and concentration, storage conditions, and temperature were investigated. Liposome size (i.e., mean diameter) and size dispersity were characterised by dynamic light scattering (DLS); z-potential measurements and TEM imaging were also carried out on selected liposome batches. It was found that the lipid type and concentration, together with the inlet flow settings, had significant effects on the properties of the resultant liposome dispersion. Notably, the millifluidic reactor was able to generate liposomes with size and dispersity ranging from 54 to 272 nm, and from 0.04 to 0.52 respectively, at operating flow rates between 1 and 10 mL/min. Moreover, when compared to a batch ethanol-injection method, the millireactor generated liposomes with a more therapeutically relevant size and size dispersity.

Megalin-targeting liposomes for placental drug delivery

Every year, complications during pregnancy affect more than 26 million women. Some of those diseases are associated with significant morbidity and mortality, as is the case of preeclampsia, the main cause of maternal deaths globally. The ability to improve the delivery of drugs to the placenta upon administration to the mother may offer new opportunities in the treatment of diseases of pregnancy. The objective of this study was to develop megalin-targeting liposome nanocarriers for placental drug delivery. Megalin is a transmembrane protein involved in clathrin-mediated endocytic processes, and is expressed in the syncytiotrophoblast (SynT), an epithelial layer at maternal-fetal interface. Targeting megalin thus offers an opportunity for the liposomes to hitchhike into the SynT, thus enriching the concentration of any associated therapeutic cargo in the placental tissue. PEGylated (2 KDa) lipids were modified with gentamicin (GM), a substrate to megalin receptors as we have shown in earlier studies, and used to prepare placental-targeting liposomes. The ability of the targeting liposomes to enhance accumulation of a fluorescence probe was assessed in an in vivo placental model - timed-pregnant Balb/c mice at gestational day (GD) 18.5. The targeting liposomes containing 10 mol% GM-modified lipids increased the accumulation of the conjugated fluorescence probe in the placenta with a total accumulation of 2.8% of the initial dose, which corresponds to a 94 fold increase in accumulation compared to the free probe (p < .0001), and 2-4 fold accumulation compared to the non-targeting control liposomes (p < .0001), as measured by both tissue extraction assay and ex vivo imaging. Furthermore, confocal images of placental SynT cross-sections show a 3-fold increase of the targeting liposomes compared with the non-targeting liposomes. The rate and extent of uptake of a fluorescent probe encapsulated within targeting liposomes was also probed in an in vitro model of the human placental barrier (polarized BeWo monolayers) using flow cytometry. Targeting liposomes containing 5 mol% GM-modified lipids enhanced the uptake of the probe by 1.5 fold compared to the non-targeting control. An increase to 10 mol% of the modified lipid resulted in further enhancement in uptake, which was 2 fold greater compared to control. In a competition assay, inhibition of the megalin receptors resulted in a significant reduction in uptake of the fluorescence probe encapsulated in GM-modified liposomes compared to the uptake without free inhibitor (p < .0001), implicating the involvement of megalin receptor in the internalization of the liposomes. Taken together, these results demonstrate that megalin-targeted liposomes may offer an opportunity to enhance the delivery of therapeutics to the placenta for the treatment of diseases of pregnancy.

Lipid-based Vehicles for siRNA Delivery in Biomedical Field

BACKGROUND

Genetic drugs have aroused much attention in the past twenty years. RNA interference (RNAi) offers novel insights into discovering potential gene functions and therapies targeting genetic diseases. Small interference RNA (siRNA), typically 21-23 nucleotides in length, can specifically degrade complementary mRNA. However, targeted delivery and controlled release of siRNA remain a great challenge.

METHODS

Different types of lipid-based delivery vehicles have been synthesized, such as liposomes, lipidoids, micelles, lipoplexes and lipid nanoparticles. These carriers commonly have a core-shell structure. For active targeting, ligands may be conjugated to the surface of lipid particles.

RESULTS

Lipid-based drug delivery vehicles can be utilized in anti-viral or anti-tumor therapies. They can also be used to tackle genetic diseases or discover novel druggable genes.

CONCLUSION

In this review, the structures of lipid-based vehicles and possible surface modifications are described, and applications of delivery vehicles in biomedical field are discussed.

Contribution of headgroup and chain length of glycerophospholipids to thermal stability and permeability of liposomes loaded with calcein

Biological membranes are complex systems that are composed of lipids, proteins and carbohydrates. They are difficult to study, so it is established practice to use lipid vesicles that consist of closed 'shells' of phospholipid bilayers as model systems to study various functional and structural aspects of lipid organisation. To define the effects of the structural properties of lipid vesicles on their phase behaviour, we investigated their headgroup and chain length, and the chemical bonds by which their acyl chains are attached to the glycerol moiety of glycerophospholipid species, in terms of phase transition temperature, enthalpy change and calcein permeability. We used differential scanning calorimetry to measure the temperature and enthalpy changes of phase transition, and fluorescence to follow calcein release through the bilayer structure. Our data show that longer acyl chains increase the stability of the lipid bilayers, whereas higher salt concentrations decrease the thermal stability and widen the phase transitions of these lipid bilayers. We discuss the possible reasons for the observed phase transition behaviour.

The effect of triamcinolone in liposomes on oral wound healing in rats

The purpose of this study was to determine whether oral mucosa wounds in rats can be successfully treated with triamcinolone acetonide (TA), incorporated into liposomes. A round wound was inflicted on the oral mucosa of female Wistar rats divided into four groups of 12 animals. This wound was treated topically from day 1 with liposomes without the inclusion of TA and liposomes containing 0.01% or 0.05% TA. The wounds of the animals in the control group were not treated. Polymethyl metacrylate was used as an ointment for mixing in liposomes. The size of the wound was measured until day 6. The area of inflammatory infiltrate under the wound was evaluated by histopathology, the expression of iNOS (inducible nitric oxide synthase) enzyme under the wound was evaluated by immunohistochemistry until day 6. On the sixth day of experiment, the size of the wound and the area of the inflammatory infiltrate was the smallest in the group receiving empty liposomes (EL). Expression of iNOS was the most reduced in the group receiving EL. We conclude that oral mucosa wounds can be successfully treated with liposomes, although the incorporated drug triamcinolone would not be the appropriate drug for treating wounds of traumatic origin.

Development of β-elemene and Cisplatin Co-Loaded Liposomes for Effective Lung Cancer Therapy and Evaluation in Patient-Derived Tumor Xenografts

PURPOSE

β-elemene and cisplatin combined chemotherapy currently is one of the most important settings available for lung cancer therapy in China. However, the clinical outcome is limited by their pharmacokinetic drawbacks. On the other hand, most of nanomedicines have failed in clinical development due to the huge differences between heterogeneous clinical tumor tissues and homogenous cell-derived xenografts. In this work, we fabricated a β-elemene and cisplatin co-loaded liposomal system to effectively treat lung cancer.

METHOD

In vitro cytotoxicity of co-loaded liposomes was studied by MTT, trypan and Hoechst/PI staining, and western blot in A549, A549/DDP, and LCC cells. In vivo antitumor efficacy was evaluated in cell-derived and clinically relevant patient-derived xenografts.

RESULTS

Co-loaded liposomes were more cytotoxic to cancer cells, especially than the combination of single-loaded liposomes, benefiting from their simultaneous drug internalization and release. As a result, they exhibited desirable therapeutic outcome in both cell-derived and patient-derived xenografts.

CONCLUSION

β-elemene and cisplatin co-loaded liposomes are a clinically promising candidate for effective lung cancer therapy.

Cubosomal based oral tablet for controlled drug delivery of telmisartan: formulation, in-vitro evaluation and in-vivo comparative pharmacokinetic study in rabbits

A nanoparticulate system; cubosomes has been suggested to support the controlled release of Telmisartan (TEL), a poorly water-soluble medication. Four distinctive formulae were selected according to the results of three estimated responses. The liquid cubosomes were successfully adsorbed onto Aerosil 380 to form granules. The formulae were evaluated for their flow properties. The best granules were compressed into tablets suitable for oral administration. The tablets were evaluated for its performance. The in vivo study of the best selected cubosomal tablets was checked after oral administration in the blood of albino rabbits utilizing an HPLC method. Results revealed that the highest EE was shown in formulae C5 (59.68 ± 1.3). All the prepared formulae had particle size less than 500 nm with PDI < 0.5 and the highest zeta potential results were observed in C5, C7, C9, C11 and C12 (>30 mv). A7 and A9 prepared using Aerosil 380 showed a perfect flowability. After 1 h of dissolution testing, the commercial product showed a 66% drug release while the release of all cubosomal formulae didn't exceed 35% during the first hour reaching a 85% of the drug released at the end of 24 h. A7 was selected for the in vivo study; T_max of TEL absorption is increased for cubosomal formula by three folds indicating sustained release pattern. The relative bioavailability is also increased by 2.6 fold. The investigation proposed the rationality of cubosome to figure an effective controlled release tablets to improve its bioavailability and expand its activity.

Proniosomal gel-mediated topical delivery of fluconazole: Development, in vitro characterization, and microbiological evaluation

The aim of this study was to explore the potential of proniosomal gel for topical delivery of fluconazole, an antifungal drug used in fungal infections caused by pathogenic fungi. Fluconazole-loaded proniosomal gels were prepared by the coacervation phase separation method using different nonionic surfactants (spans and tweens). The prepared fluconazole proniosomal gels were evaluated for various parameters such as particle size (PS), drug entrapment efficiency percentage (EE%), and in vitro drug release. The experimental results showed that the EE% for the prepared formulae are acceptable (85.14%–97.66%) and they are nanosized (19.8–50.1 nm) and the diffusion from the gels gave the desired sustaining effect. F4, which was prepared from span 60, tween 80 (1:1), and cholesterol showed highest EE% and gave slow release (40.50% ± 1.50% after 6 h), was subjected to zeta potential (ZP) test, transmission electron microscopy as well as microbiological study. The results showed a well-defined spherical vesicle with sharp boundaries with good physical stability of fluconazole within the prepared gel. Moreover, F4 showed an excellent microbiological activity represented by a greater zone of inhibition (5.3 cm) compared to control gel (fluconazole in 2% hydroxy propyl methyl cellulose (HPMC) gel formula) (4.2 cm) and plain gel with no drug (0 cm) against Candida albicans. This study showed the suitability of the proniosomal gel in attaining the desired sustainment effect for topical delivery of fluconazole for the management of fungal infection. The physical stability study showed that there was no significant change in EE%, PS, and ZP of fluconazole proniosomal gel after storage for 6 months.

Metformin hydrochloride and wound healing: from nanoformulation to pharmacological evaluation

Niosomes as drug delivery systems have the ability to decrease drugs' side effects and increase their therapeutic effectiveness. Metformin HCl is an oral antihyperglycemic agent belonging to biguanides. It is the most commonly chosen drug as a startup therapy for patients newly diagnosed with type 2 diabetes. This study aims to encapsulate metformin HCl inside niosomes to be used as a transdermal formulation helping to prolong its antidiabetic effect and investigate its ability to enhance wound healing in diabetic patients. Thin film hydration method was used to prepare metformin HCl niosomes using different proportions of Span 60, Span 40, Tween 80, and cholesterol. All formulations were characterized using transmission electron microscope, zeta potential, and vesicle size. In vitro release studies, stability studies and in vivo evaluation were conducted on selected niosomal formulations. The results of entrapment efficiency ranged from 13% to 32%. Vesicle sizes were determined in nano-range. The in vitro release profile of metformin HCl from niosomes occurred in two consecutive phases. Biological evaluation on diabetic rats revealed that metformin HCl niosomal gel given every 2 days showed a better sustained antidiabetic effect than oral doses given daily. It also showed an improvement in wound healing for diabetic rats given metformin formulations compared to nontreated ones.

On the design of tailored liposomes for KRX29 peptide delivery

The high interest in therapeutic peptides, due to the specificity of their mechanisms of action, has stimulated the research of new delivery strategies to overcome bioavailability problems concerning the use of peptides in their naked form. In this study liposomal suitable delivery system was designed and produced.

In vitro models for evaluating safety and efficacy of novel technologies for skin drug delivery

For preclinical testing of novel therapeutics, predictive in vitro models of the human skin are required to assess efficacy, absorption and safety. Simple as well as more sophisticated three-dimensional organotypic models of the human skin emerged as versatile and powerful tools simulating healthy as well as diseased skin states. Besides addressing the demands of research and industry, such models serve as valid alternative to animal testing. Recently, the acceptance of several models by regulatory authorities corroborates their role as important building block for preclinical development. However, valid assessment of readout parameters derived from these models requires suitable analytical techniques. Standard analytical methods are mostly destructive and limited regarding in-depth investigation on molecular level. The combination of adequate in vitro models with modern non-invasive analytical modalities bears a great potential to address important skin drug delivery related questions. Topics of interest are for instance the assessment of repeated dosing effects and xenobiotic biotransformation, which cannot be analyzed by destructive techniques. This review provides a comprehensive overview of current in vitro skin models differing in functional complexity and mimicking healthy as well as diseased skin states. Further, benefits and limitations regarding analytical evaluation of efficacy, absorption and safety of novel drug carrier systems applied to such models are discussed along with a prospective view of anticipated future directions. In addition, emerging non-invasive imaging modalities are introduced and their significance and potential to advance current knowledge in the field of skin drug delivery is explored.

Transdermal potential and anti-arthritic efficacy of ursolic acid from niosomal gel systems

The aim of the present study was to optimize niosomes by experimental design for enhanced transdermal delivery of ursolic acid for the effective treatment of arthritis. The experimental design (3 factor 3 levels, Box-Behnken design) was used to study individual and combined effects of different formulation variables. The variables cholesterol (X1), span 60 (X2) and phospholipid (X3) were taken as independent factors and their effect was observed on size (Y1) entrapment efficiency (Y2), and transflux (Y3). The formulation composition with span 60 (85mg), cholesterol (12.3mg), and phospholipid (65mg) was found to fulfil requisites of optimized ursolic acid niosome formulation (URNF). URNF had shown vesicle size of 665.45nm, entrapment efficiency of 92.74% with transflux of 17.25μg/cm(2)/h. The in vivo bioactivity showed that the prepared URNF-gel was able to provide good anti-arthritic activity due to enhanced permeation of UA through the skin and results were found to be comparable to standard gel (Omni gel). The radiographical image confirmed that, the developed URNF-gel was found to be effective to treat arthritis. Thus niosomal gel of ursolic acid would be a promising alternative to conventional therapy for safe and efficient treatment of arthritis and musculoskeletal disorders.

In vivo evaluation of different alterations of redox status by studying pharmacokinetics of nitroxides using magnetic resonance techniques

Free radicals, particularly reactive oxygen species (ROS), are involved in various pathologies, injuries related to radiation, ischemia-reperfusion or ageing. Unfortunately, it is virtually impossible to directly detect free radicals in vivo, but the redox status of the whole organism or particular organ can be studied in vivo by using magnetic resonance techniques (EPR and MRI) and paramagnetic stable free radicals - nitroxides. Here we review results obtained in vivo following the pharmacokinetics of nitroxides on experimental animals (and a few in humans) under various conditions. The focus was on conditions where the redox status has been altered by induced diseases or harmful agents, clearly demonstrating that various EPR/MRI/nitroxide combinations can reliably detect metabolically induced changes in the redox status of organs. These findings can improve our understanding of oxidative stress and provide a basis for studying the effectiveness of interventions aimed to modulate oxidative stress. Also, we anticipate that the in vivo EPR/MRI approach in studying the redox status can play a vital role in the clinical management of various pathologies in the years to come providing the development of adequate equipment and probes.

Development and in vitro/in vivo evaluation of controlled release provesicles of a nateglinide-maltodextrin complex

The aim of this study was to characterize the provesicle formulation of nateglinide (NTG) to facilitate the development of a novel controlled release system of NTG with improved efficacy and oral bioavailability compared to the currently marketed NTG formulation (Glinate™ 60). NTG provesicles were prepared by a slurry method using the non-ionic surfactant, Span 60 (SP), and cholesterol (CH) as vesicle forming agents and maltodextrin as a coated carrier. Multilamellar niosomes with narrow size distribution were shown to be successfully prepared by means of dynamic laser scattering (DLS) and field emission scanning electron microscopy (FESEM). The absence of drug-excipient interactions was confirmed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. In vitro release of NTG in different dissolution media was improved compared to pure drug. A goat intestinal permeation study revealed that the provesicular formulation (F4) with an SP:CH ratio of 5:5 gave higher cumulative amount of drug permeated at 48 h compared to Glinate™ 60 and control. A pharmacodynamic study in streptozotocin-induced diabetic rats confirmed that formulation F4 significantly (P<0.05) reduced blood glucose levels in comparison to Glinate 60. Overall the results show that controlled release NTG provesicles offer a useful and promising oral delivery system for the treatment of type II diabetes.

Origins of microstructural transformations in charged vesicle suspensions: the crowding hypothesis

It is observed that charged unilamellar vesicles in a suspension can spontaneously deflate and subsequently transition to form bilamellar vesicles, even in the absence of externally applied triggers such as salt or temperature gradients. We provide strong evidence that the driving force for this deflation-induced transition is the repulsive electrostatic pressure between charged vesicles in concentrated suspensions, above a critical effective volume fraction. We use volume fraction measurements and cryogenic transmission electron microscopy imaging to quantitatively follow both the macroscopic and microstructural time-evolution of cationic diC18:1 DEEDMAC vesicle suspensions at different surfactant and salt concentrations. A simple model is developed to estimate the extent of deflation of unilamellar vesicles caused by electrostatic interactions with neighboring vesicles. It is determined that when the effective volume fraction of the suspension exceeds a critical value, charged vesicles in a suspension can experience "crowding" due to overlap of their electrical double layers, which can result in deflation and subsequent microstructural transformations to reduce the effective volume fraction of the suspension. Ordinarily in polydisperse colloidal suspensions, particles interacting via a repulsive potential transform into a glassy state above a critical volume fraction. The behavior of charged vesicle suspensions reported in this paper thus represents a new mechanism for the relaxation of repulsive interactions in crowded situations.

Development of ketoprofen loaded proliposomal powders for improved gastric absorption and gastric tolerance: in vitro and in situ evaluation

The aim of the current investigation was to improve dissolution rate, gastric absorption and tolerance of a water insoluble non-steroidal anti-inflammatory drug ketoprofen by developing proliposomal powders. Ketoprofen proliposomal powders were prepared by solvent evaporation method with varying ratios of hydrogenated soyphosphatidyl choline (HSPC) and cholesterol. The prepared proliposomal powders were characterized for vesicle size, micromeritics, entrapment efficiency and in vitro dissolution behavior. Proliposomal powder (KPL3) composed of equimolar ratios of HSPC and cholesterol loaded on pearlitol SD 200 was selected as optimized formulation as it produced smaller liposomes (5.24 ± 1.35 μm) upon hydration with highest entrapment efficiency (53.16 ± 0.06%). All proliposomal powders showed improved dissolution characteristics than pure drug, however dissolution of drug from KPL3 was found to be highest (91.17 ± 6.3) and which is about 24 times higher than pure ketoprofen within 5 min. The transformation of crystalline ketoprofen to amorphous form was confirmed by solid state characterization. The absorption rate per hour for pure ketoprofen and proliposomal formulation (KPL3) was assessed in the stomach by conducting in situ gastric absorption studies in Wistar rats and was found to be 27 ± 1.22 and 36.98 ± 1.95%, respectively. In conclusion, enhanced dissolution and gastric absorption rate of ketoprofen from proliposomal powders suggest them as potential candidate for oral bioavailability improvement of ketoprofen.

Microfluidic-enabled liposomes elucidate size-dependent transdermal transport

Microfluidic synthesis of small and nearly-monodisperse liposomes is used to investigate the size-dependent passive transdermal transport of nanoscale lipid vesicles. While large liposomes with diameters above 105 nm are found to be excluded from deeper skin layers past the stratum corneum, the primary barrier to nanoparticle transport, liposomes with mean diameters between 31-41 nm exhibit significantly enhanced penetration. Furthermore, multicolor fluorescence imaging reveals that the smaller liposomes pass rapidly through the stratum corneum without vesicle rupture. These findings reveal that nanoscale liposomes with well-controlled size and minimal size variance are excellent vehicles for transdermal delivery of functional nanoparticle drugs.

Liposomes for (trans)dermal drug delivery: the skin-PVPA as a novel in vitro stratum corneum model in formulation development

Penetration potential of vesicles destined for trans(dermal) administration remains to be of great interests both in respect to drug therapy and cosmetic treatment. This study investigated the applicability of the phospholipid vesicle-based permeation assay (PVPA) as a novel in vitro skin barrier model for screening purposes in preformulation studies. Various classes of liposomes containing hydrophilic model drug were examined, including conventional liposomes (CLs), deformable liposomes (DLs) and propylene glycol liposomes (PGLs). The size, surface charge, membrane deformability and entrapment efficiency were found to be affected by the vesicle lipid concentration, the presence of the surfactant and propylene glycol. All liposomes exhibited prolonged drug release profiles with an initial burst effect followed by a slower release phase. The permeation of the drug from all of the tested liposomes, as assessed with the mimicked stratum corneum--PVPA model, was significantly enhanced as compared to the permeability of the drug in solution form. Although the DLs and the PGLs exhibited almost the same membrane elasticity, the permeability of the drug delivered by PGLs was higher (6.2 × 10⁻⁶ cm/s) than DLs (5.5 × 10⁻⁶ cm/s). Therefore, this study confirmed both the potential of liposomes as vesicles in trans(dermal) delivery and potential of the newly developed skin-PVPA for the screening and optimization of liposomes at the early preformulation stage.

Neuroprotective study of Nigella sativa-loaded oral provesicular lipid formulation: in vitro and ex vivo study

AIM

The aim of this research was to develop proniosome (niosomes) of Nigella sativa (NS) to improve its drug release, gastrointestinal (GI) permeation and neuroprotective activity.

MATERIALS AND METHODS

Proniosomes were prepared by thin film method using various compositions of nonionic surfactants, cholesterol, and phosphatidylcholine. The optimum influence of different formulation variables of NS such as surfactant type, phosphatidylcholine and cholesterol concentration were optimized for size and entrapment efficiency.

RESULTS AND DISCUSSION

Results indicated that prepared niosome showed smaller size with high entrapment efficiency. The permeation enhancement ratio was found to be 2.16 in comparison to control with maximum flux value obtained was 7.23 µg/cm(2)/h for formulation NS6. The in vivo study revealed that the niosomal dispersion significantly improved neuroprotective activity in comparison to standard and control formulation.

CONCLUSION

In conclusion, developed proniosomal formulation could be one of the promising delivery system for NS with better drug release and GI permeation profiles and improved neuroprotective activity and merits for further study.

Flow-directed loading of block copolymer micelles with hydrophobic probes in a gas-liquid microreactor

We investigate the loading efficiencies of two chemically distinct hydrophobic fluorescent probes, pyrene and naphthalene, for self-assembly and loading of polystyrene-block-poly(acrylic acid) (PS-b-PAA) micelles in gas-liquid segmented microfluidic reactors under different chemical and flow conditions. On-chip loading efficiencies are compared to values obtained via off-chip dropwise water addition to a solution of copolymer and probe. On-chip, probe loading efficiencies depend strongly on the chemical probe, initial solvent, water content, and flow rate. For pyrene and naphthalene probes, maximum on-chip loading efficiencies of 73 ± 6% and 11 ± 3%, respectively, are obtained, in both cases using the more polar solvent (DMF), an intermediate water content (2 wt % above critical), and a low flow rate (∼5 μL/min); these values are compared to 81 ± 6% and 48 ± 2%, respectively, for off-chip loading. On-chip loading shows a significant improvement over the off-chip process where shear-induced formation of smaller micelles enables increased encapsulation of probe. As well, we show that on-chip loading allows off-chip release kinetics to be controlled via flow rate: compared to vehicles produced at ∼5 μL/min, pyrene release kinetics from vehicles produced at ∼50 μL/min showed a longer initial period of burst release, followed by slow release over a longer total period. These results demonstrate the necessity to match probes, solvents, and running conditions to achieve effective loading, which is essential information for further developing these on-chip platforms for manufacturing drug delivery formulations.

Effect of flavonoid structure on the fluidity of model lipid membranes

We investigated how the structural properties of (+)-catechin, (-)-epicatechin, (-)-epigallocatechin (EGC) and (-)-epigallocatechin-3-gallate (EGCG) and butylated hydroxytoluene (BHT) correlate with structural changes of phosphatidylcholine plus sphingomyelin (2.4:1) model lipid membranes. Changes were measured by fluorescence anisotropy, electron paramagnetic resonance, and differential scanning calorimetry. Two fluorophores and two spin probes were used to monitor membrane characteristics close to water-lipid interface and in the middle of the bilayer. The data obtained were correlated to the amount of bounded compounds, the number of H-bonds, and the topological polar surface area (TPSA) of the compounds. These correlations reflect the behaviours of (+)-catechin, (-)-epicatechin, EGC, EGCG and BHT. Our results confirm that phenolics studied here are bounded to a membrane surface predominantly via hydrogen bonds, while BTH is inserted into the lipid bilayer.