Incorporation of liquid lipid in lipid nanoparticles for ocular drug delivery enhancement

In vitro and in vivo studies of ocular topically administered NLC for the treatment of uveal melanoma

Uveal melanoma is one of the most common and aggressive intraocular malignancies, and, due to its great capability of metastasize, it constitutes the most incident intraocular tumor in adults. However, to date there is no effective treatment since achieving the inner ocular tissues still constitutes one of the greatest challenges in actual medicine, because of the complex structure and barriers. Uncoated and PEGylated nanostructured lipid carriers were developed to achieve physico-chemical properties (mean particle size, homogeneity, zeta potential, pH and osmolality) compatible for the ophthalmic administration of (S)-(-)-MRJF22, a new custom-synthetized prodrug for the potential treatment of uveal melanoma. The colloidal physical stability was investigated at different temperatures by Turbiscan® Ageing Station. Morphology analysis and mucoadhesive studies highlighted the presence of small particles suitable to be topically administered on the ocular surface. In vitro release studies performed using Franz diffusion cells demonstrated that the systems were able to provide a slow and prolonged prodrug release. In vitro cytotoxicity test on Human Corneal Epithelium and Human Uveal Melanoma cell lines and Hen's egg-chorioallantoic membrane test showed a dose-dependent cytotoxic effect of the free prodrug on corneal cells, whose cytocompatibility improved when encapsulated into nanoparticles, as also confirmed by in vivo studies on New Zealand albino rabbits. Antiangiogenic capability and preventive anti-inflammatory properties were also investigated on embryonated eggs and rabbits, respectively. Furthermore, preliminary in vivo biodistribution images of fluorescent nanoparticles after topical instillation in rabbits' eyes, suggested their ability to reach the posterior segment of the eye, as a promising strategy for the treatment of choroidal uveal melanoma.

Nano-based eye drop: Topical and noninvasive therapy for ocular diseases

Eye drops are the most accessible therapy for ocular diseases, while inevitably suffering from their lower bioavailability which highly restricts the treatment efficacy. The introduction of nanotechnology has attracted considerable interest as it has advantages over conventional ones such as prolonged ocular surface retention time and enhanced ocular barrier penetrating properties, and achieving higher bioavailability and improved treatment efficacy. This review describes various ocular diseases treated with eye drops as well as the physiological and anatomical ocular barriers faced with through drug administration. It also summarizes the recent advances regarding the utilization of nanotechnology in developing eye drops, and how to optimize the nanocarrier-based ocular drug delivery systems. The prospective future research directions for nano-based eye drops are also discussed here.

Abdelgawad M, Ghoneim MM, Abdou EM. Assessment of Nasal-Brain-Targeting Efficiency of New Developed Mucoadhesive Emulsomes Encapsulating an Anti-Migraine Drug for Effective Treatment of One of the Major Psychiatric Disorders Symptoms

Migraine is one of the major symptoms of many psychiatric and mental disorders like depression and anxiety. Eletriptan Hydrobromide (EH) is a well-tolerated drug in migraine treatment, but suffers from low oral bioavailability and low brain targeting after oral delivery. New nasal mucoadhesive EH-emulsomes development could be a new means to direct the drug from the nose-to-brain to achieve rapid onset of action and high drug concentration in the brain for acute migraine treatment. Eletriptan mucoadhesive emulsomes formulations were prepared using thin-film hydration method and 2³ full factorial design was adopted to study different formulation factors’ effect on the emulsomes characters. The emulsomes were characterized for entrapment efficiency (EE%), zeta potential (ZP), particle size (PS), morphology, and ex-vivo permeation through the nasal mucosa. The selected formula was evaluated in mice for its in-vivo bio-distribution in comparison with EH intranasal and intravenous solutions. Drug targeting efficacy (DTE%) and nose-to-brain direct transport percentage (DTP%) were calculated. The optimization formulation showed a nanoparticle size of 177.01 nm, EE 79.44%, and ZP = 32.12 ± 3.28 mV. In addition, in-vitro permeability studies revealed enhanced drug permeability with suitable mean residence time up to 120 ± 13 min. EH-emulsomes were stable under different storage conditions for three months. In vivo examination and pharmacokinetic drug targeting parameters revealed EH transport to the CNS after EH nanoparticle nasal administration. Histopathology study showed no ciliotoxic effect on the nasal mucosa. From the results, it can be confirmed that the emulsomes formulation of EH proved safe direct nose-to-brain transport of EH after nasal administration of EH emulsomes.

Spanlastics nanovesicular ocular insert as a novel ocular delivery of travoprost: optimization using Box-Behnken design and in vivo evaluation

Currently, travoprost is a synthetic prostaglandin F₂α analogue used in the treatment of glaucoma, it is delivered by eye drop solution. Due to its very low bioavailability and patient non-compliance, the objective of the current study was to enhance its bioavailability, and prolong its release Spanlastic nano-vesicles gels were designed and optimized using Box-Behnken design. The optimized spanlastic nano-vesicles gel exhibited the lowest particle size (PS), polydispersity index (PDI) and the highest zeta potential (ZP), encapsulation efficiency (EE) and mucoadhesive strength was fabricated into spanlastic nano-vesicles ocular insert by solvent casting. In vivo studies showed enhanced bioavailability of travoprost spanlastic nano-vesicles gel and ocular insert compared to the marketed eye drops (travoswix®), as proven by their higher C_max and AUC_0-∞, in addition to being nonirritant to ocular surfaces. However, spanlastic nano-vesicles ocular insert showed more prolonged effect than spanlastic nano-vesicles gel. According to our study, it can be suggested that travoprost spanlastic nano-vesicles ocular insert is a novel ocular delivery system for glaucoma treatment.

Essential Oil and Hydrophilic Antibiotic Co-Encapsulation in Multiple Lipid Nanoparticles: Proof of Concept and In Vitro Activity against Pseudomonas aeruginosa

In the worldwide context of an impending emergence of multidrug-resistant bacteria, this research combined the advantages of multiple lipid nanoparticles (MLNs) and the promising therapeutic use of essential oils (EOs) as a strategy to fight the antibiotic resistance of three Pseudomonas aeruginosa strains with different cefepime (FEP) resistance profiles. MLNs were prepared by ultrasonication using glyceryl trioleate (GTO) and glyceryl tristearate (GTS) as a liquid and a solid lipid, respectively. Rosemary EO (REO) was selected as the model EO. REO/FEP-loaded MLNs were characterized by their small size (~110 nm), important encapsulation efficiency, and high physical stability over time (60 days). An assessment of the antimicrobial activity was performed using antimicrobial susceptibility testing assays against selected P. aeruginosa strains. The assays showed a considerable increase in the antibacterial property of REO-loaded MLNs compared with the effect of crude EO, especially against P. aeruginosa ATCC 9027, in which the minimum inhibitory concentration (MIC) value decreased from 80 to 0.6 mg/mL upon encapsulation. Furthermore, the incorporation of FEP in MLNs stabilized the drug without affecting its antipseudomonal activity. Thus, the ability to co-encapsulate an essential oil and a hydrophilic antibiotic into MLN has been successfully proved, opening new possibilities for the treatment of serious antimicrobial infections.

Topical ocular delivery of vancomycin loaded cationic lipid nanocarriers as a promising and non-invasive alternative approach to intravitreal injection for enhanced bacterial endophthalmitis management

Vancomycin (VCM) is a drug of choice for treating infections caused by Staphylococcus species, reported being the most causative agent of bacterial endophthalmitis. However, the ocular bioavailability of topically applied VCM is low due to its high molecular weight and hydrophilicity. The current study sought to explore whether the nanostructured lipid carriers (NLCs) fabricated via cold homogenization technique could improve ocular penetration and prolong the ophthalmic residence of VCM. A 2³ full factorial design was adopted to evaluate the influence of different process and formulation variables on VCM-loaded NLC formulae. The optimized formula with the particle size of 96.4 ± 0.71 nm and narrow size distribution showed spherical morphology obtained by AFM and represented sustained drug release up to 67% in 48 h fitted to the Korsmeyer-Peppas model with probably non-Fickian diffusion kinetic. FTIR studies visualized the drug-carrier interactions in great detail. High encapsulation of VCM (74.8 ± 4.3% w/w) in NLC has been established in DSC and PXRD analysis. The optimal positively charged (+ 29.7 ± 0.47 mV) colloidal dispersion was also stable for 12 weeks at both 4 °C and 25 °C. According to in vivo studies, incorporation of VCM in NLC resulted in a nearly 3-fold increase in the intravitreal concentration of VCM after eye-drop instillation over control groups. Besides, microbiological evaluation admitted its therapeutic effect within five days is comparable to intravitreal injection of VCM. Further, the optimized formula was found to be nonirritant and safe for ophthalmic administration in RBC hemolytic assay. Also, fluorescent tracking of NLCs on rabbit's cornea showed an increase in corneal penetration of nanoparticles. Thus, it is possible to infer that the evolved NLCs are promising drug delivery systems with superior attainments for enhanced Vancomycin ophthalmic delivery to the eye's posterior segment and improved bacterial endophthalmitis management.

A new medium-throughput screening design approach for the development of hydroxymethylnitrofurazone (NFOH) nanostructured lipid carrier for treating leishmaniasis

Hydroxymethilnitrofurazone (NFOH) is a nitrofurazone derivative and has potential use in treating leishmaniasis. However, due to low water solubility and bioavailability, NFOH has failed in in vivo tests. Nanostructured lipid carrier (NLC) is an alternative to overcome these limitations by improving pharmacokinetics and modifying drug delivery. This work is focused on developing a novel NFOH-loaded NLC (NLC-NFOH) using a D-optimal mixture statistical design and high-pressure homogenization, for oral administration to treat leishmaniasis. The optimized NLC-NFOH consisted of Mygliol® 840, Gelucire® 50/13, and Precirol® ATO 5 as lipids. These lipids were selected using a rapid methodology Technobis Crystal 16 T M, microscopy, and DSC. Different tools for selecting lipids provided relevant scientific knowledge for the development of the NLC. NLC-NFOH presented a z-average of 198.6 ± 5.4 nm, PDI of 0.11 ± 0.01, and zeta potential of -13.7 ± 0.7 mV. A preliminary in vivo assay was performed by oral administration of NLC-NFOH (2.8 mg/kg) in one healthy male Wistar rat (341 g) by gavage. Blood from the carotid vein was collected, and the sample was analyzed by HPLC. The plasma concentration of NFOH after 5 h of oral administration was 0.22 μg/mL. This same concentration was previously found using free NFOH in the DMSO solution (200 mg/kg), which is an almost 100-fold higher dose. This study allowed a design space development approach of the first NLC-NFOH with the potential to treat leishmaniasis orally.

Omar M, A. Mahmoud H, A. Abou-Taleb H. Nanostructured Lipid Carriers to Mediate Brain Delivery of Temazepam: Design and In Vivo Study

The opposing effect of the blood–brain barrier against the delivery of most drugs warrants the need for an efficient brain targeted drug delivery system for the successful management of neurological disorders. Temazepam-loaded nanostructured lipid carriers (NLCs) have shown possibilities for enhancing bioavailability and brain targeting affinity after oral administration. This study aimed to investigate these properties for insomnia treatment. Temazepam-NLCs were prepared by the solvent injection method and optimized using a 4² full factorial design. The optimum formulation (NLC-1) consisted of; Compritol^® 888 ATO (75 mg), oleic acid (25 mg), and Poloxamer^® 407 (0.3 g), with an entrapment efficiency of 75.2 ± 0.1%. The average size, zeta potential, and polydispersity index were determined to be 306.6 ± 49.6 nm, −10.2 ± 0.3 mV, and 0.09 ± 0.10, respectively. Moreover, an in vitro release study showed that the optimized temazepam NLC-1 formulation had a sustained release profile. Scintigraphy images showed evident improvement in brain uptake for the oral ^99mTc-temazepam NLC-1 formulation versus the ^99mTc-temazepam suspension. Pharmacokinetic data revealed a significant increase in the relative bioavailability of ^99mTc-temazepam NLC-1 formulation (292.7%), compared to that of oral ^99mTc-temazepam suspension. Besides, the NLC formulation exhibited a distinct targeting affinity to rat brain. In conclusion, our results indicate that the developed temazepam NLC formulation can be considered as a potential nanocarrier for brain-mediated drug delivery in the out-patient management of insomnia.

Advances in ophthalmic preparation: the role of drug nanocrystals and lipid-based nanosystems

Nanocrystals and lipid-based nanosystems have the potential to play a crucial role in a significant shift in the treatment of ophthalmic diseases. These drug delivery systems allow overcoming the barriers imposed by anatomy and physiology of the organ of vision. This review aims to present new perspectives for these innovative preparations, emphasising the applications of the nanocrystal and lipid-based nanosystem while outlining their advantages and the drawbacks. The in vivo performance of the lipid-based nanosystems was highlighted. Lipid-based nanosystems and nanocrystals showed a prolonged effect, improved ocular bioavailability, upper therapeutic efficacy, higher permeation, prolonged residence time, and sustained drug release, compared to the current applications. Well-established and innovative developments updates of these systems are highlighted herein.

Preparation and characterization of nanostructured lipid carriers as drug delivery system: Influence of liquid lipid types on loading and cytotoxicity

In this study, we aimed to investigate the influence of liquid lipid types on different features of NLC. Four variations of liquid lipids such as coconut oil, fish oil, black seed oil and linseed oil were used, while for all variations, cetyl palmitate was used as the solid lipid. Different NLC were characterized and compared in terms of particle size, zeta potential, polydispersity index (PDI), drug entrapment percentage and drug loading capacity. The results indicated that NLC containing black seed oil has the smallest size. Other features like PDI, zeta potential and entrapment efficiency were the same for all the liquid lipids. By close margins, the NLC containing black seed oil had the highest percent of drug release and antioxidant activity compared to the rest. Diffusion was the major mechanism of the drug release according to the drug release kinetic fitted by Higuchi's model. Differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FT-IR) confirmed no strong interaction between NLC constituents. The particles showed spherical shape morphology under atomic force microscopy (AFM). According to the cell viability assay on MCF-7 cell line, the curcumin loaded NLC composed of linseed oil showed better cytotoxic activity compared to the free curcumin.

Ocular Delivery System for Propranolol Hydrochloride Based on Nanostructured Lipid Carrier

One drawback of traditional forms of medical ocular dosage is drug dilution by tear; moreover, drugs are rapidly drained away from pre-corneal cavity by tear flow and lacrimo-nasal drainage. Prolonging contact time with different strategies and mucoadhesive vehicles will help to continuously deliver drugs to the eyes. For this study, we prepared and evaluated the effects of a nanostructure lipid carrier (NLC) on propranolol hydrochloride as a hydrophilic drug model for rabbit corneal permeation. Propranolol hydrochloride NLC was prepared using cold homogenization. The lipid was melted, then the drug and surfactant were dispersed and stirred into the melted lipid. This fused lipid phase was scattered in aqueous solution containing the cosurfactant at 4 °C and then homogenized. We evaluated particle size, drug loading, drug release, and NLC permeability through rabbit cornea as well as the formula’s effect on the cornea. Our results show that drug loading efficiency depended on the surfactant/lipid ratio (S/L) and the percentages of liquid lipid and Transcutol (Gattefosse, Saint-Priest, France) (as solubilizer). Drug release data were evaluated with the Higuchi model and a significant correlation was shown between the S/L ratio and the amount of drug released after 4 and 48 h. NLC formulations improved propranolol hydrochloride permeation. We conclude that the effect of the NLC formulations was due to mucoadhesive and film forming properties.

Ocular Drug Delivery Barriers-Role of Nanocarriers in the Treatment of Anterior Segment Ocular Diseases

Ocular drug delivery is challenging due to the presence of anatomical and physiological barriers. These barriers can affect drug entry into the eye following multiple routes of administration (e.g., topical, systemic, and injectable). Topical administration in the form of eye drops is preferred for treating anterior segment diseases, as it is convenient and provides local delivery of drugs. Major concerns with topical delivery include poor drug absorption and low bioavailability. To improve the bioavailability of topically administered drugs, novel drug delivery systems are being investigated. Nanocarrier delivery systems demonstrate enhanced drug permeation and prolonged drug release. This review provides an overview of ocular barriers to anterior segment delivery, along with ways to overcome these barriers using nanocarrier systems. The disposition of nanocarriers following topical administration, their safety, toxicity and clinical trials involving nanocarrier systems are also discussed.

Lipid nanoparticles (SLN, NLC): Overcoming the anatomical and physiological barriers of the eye - Part II - Ocular drug-loaded lipid nanoparticles

In the recent decades, various controlled delivery systems have been introduced with the aim to improve solubility, stability and bioavailability of poorly absorbed drugs. Among all, lipid nanoparticles gather interesting properties as drug or gene delivery carriers. These systems, composed either of solid lipids (SLN) or of solid and liquid lipids (NLC) stabilized with surfactants, combine the advantages of other colloidal particles such as polymeric nanoparticles, fat emulsions and liposomes avoiding their main disadvantages. Lipid nanoparticles represent an interesting approach for eye drug delivery as they can improve the corneal absorption of drugs enhancing their bioavailability. The Generally Recognized as Safe status of formulation excipients, the scaling-up facilities and the possibility of sterilization, make them suitable for industrial production. In this review, the latest findings, potential applications, and challenges related to the use of lipid nanoparticles for ocular drug delivery are comprehensively discussed.

Influence of Lipid Core Material on Physicochemical Characteristics of an Ursolic Acid-Loaded Nanostructured Lipid Carrier: An Attempt To Enhance Anticancer Activity

The impact of saturation and unsaturation in the fatty acyl hydrocarbon chain on the physicochemical properties of nanostructured lipid carriers (NLCs) was investigated to develop novel delivery systems loaded with an anticancer drug, ursolic acid (UA). Aqueous NLC dispersions were prepared by a high-pressure homogenization-ultrasonication technique with Tween 80 as a stabilizer. Mutual miscibility of the components at the air-water interface was assessed by surface pressure-area measurements, where attractive interactions were recorded between the lipid mixtures and UA, irrespective of the extent of saturation or unsaturation in fatty acyl chains. NLCs were characterized by combined dynamic light scattering, transmission electron microscopy (TEM), atomic force microscopy (AFM), differential scanning calorimetry, drug encapsulation efficiency, drug payload, in vitro drug release, and in vitro cytotoxicity studies. The saturated lipid-based NLCs were larger than unsaturated lipids. TEM and AFM images revealed the spherical and smooth surface morphology of NLCs. The encapsulation efficiency and drug payload were higher for unsaturated lipid blends. In vitro release studies indicate that the nature of the lipid matrix affects both the rate and release pattern. All UA-loaded formulations exhibited superior anticancer activity compared to that of free UA against human leukemic cell line K562 and melanoma cell line B16.

Preclinical safety of solid lipid nanoparticles and nanostructured lipid carriers: Current evidence from in vitro and in vivo evaluation

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were designed as exceptionally safe colloidal carriers for the delivery of poorly soluble drugs. SLN/NLC have the particularity of being composed of excipientsalready approved for use in medicines for human use, which offers a great advantage over any other nanoparticulate system developed from novel materials. Despite this fact, any use of excipients in new route of administration or in new dosage form requires evidence of safety. After 25 years of research on SLN and NLC, enough evidence on their preclinical safety has been published. In the present work, published data on in vitro and in vivo compatibility of SLN/NLC have been surveyed, in order to provide evidence of high biocompatibility distinguished by intended administration route. We also identified critical factors and possible weak points in SLN/NLC formulations, such as the effect of surfactants on the cell viability in vitro, which should be considered for further development.

Nanoparticle-Based Topical Ophthalmic Gel Formulation for Sustained Release of Hydrocortisone Butyrate

This study was conducted to develop formulations of hydrocortisone butyrate (HB)-loaded poly(D,L-lactic-co-glycolic acid) nanoparticles (PLGA NP) suspended in thermosensitive gel to improve ocular bioavailability of HB for the treatment of bacterial corneal keratitis. PLGA NP with different surfactants such as polyvinyl alcohol (PVA), pluronic F-108, and chitosan were prepared using oil-in-water (O/W) emulsion evaporation technique. NP were characterized with respect to particle size, entrapment efficiency, polydispersity, drug loading, surface morphology, zeta potential, and crystallinity. In vitro release of HB from NP showed a biphasic release pattern with an initial burst phase followed by a sustained phase. Such burst effect was completely eliminated when nanoparticles were suspended in thermosensitive gels and zero-order release kinetics was observed. In HCEC cell line, chitosan-emulsified NP showed the highest cellular uptake efficiency over PVA- and pluronic-emulsified NP (59.09 ± 6.21%, 55.74 ± 6.26%, and 62.54 ± 3.30%, respectively) after 4 h. However, chitosan-emulsified NP indicated significant cytotoxicity of 200 and 500 μg/mL after 48 h, while PVA- and pluronic-emulsified NP exhibited no significant cytotoxicity. PLGA NP dispersed in thermosensitive gels can be considered as a promising drug delivery system for the treatment of anterior eye diseases.

Ophthalmic applications of lipid-based drug nanocarriers: an update of research and patenting activity

Ophthalmic diseases collect great attention by researchers and pharmaceutical technologists, since they can dramatically worsen the quality of life. Because of the limited duration of action on the eye surface, and anatomical/physiological barriers to drug penetration from it into the inner eye structures, conventional ocular formulations are generally unable to perform at their best. Nanotechnology approaches can represent a solution to improve the therapeutic efficiency, compliance and safety of ocular drugs. In this respect, lipid-based nanocarriers are among the most interesting systems. Their composition and production methods make them highly biocompatible and safe formulations. This review illustrates the developments achieved in ocular drug delivery using lipid-based nanocarriers, with a critical revision of recent scientific articles and filed patents.

Lipid Nanoparticles for Ocular Gene Delivery

Lipids contain hydrocarbons and are the building blocks of cells. Lipids can naturally form themselves into nano-films and nano-structures, micelles, reverse micelles, and liposomes. Micelles or reverse micelles are monolayer structures, whereas liposomes are bilayer structures. Liposomes have been recognized as carriers for drug delivery. Solid lipid nanoparticles and lipoplex (liposome-polycation-DNA complex), also called lipid nanoparticles, are currently used to deliver drugs and genes to ocular tissues. A solid lipid nanoparticle (SLN) is typically spherical, and possesses a solid lipid core matrix that can solubilize lipophilic molecules. The lipid nanoparticle, called the liposome protamine/DNA lipoplex (LPD), is electrostatically assembled from cationic liposomes and an anionic protamine-DNA complex. The LPD nanoparticles contain a highly condensed DNA core surrounded by lipid bilayers. SLNs are extensively used to deliver drugs to the cornea. LPD nanoparticles are used to target the retina. Age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy are the most common retinal diseases in humans. There have also been promising results achieved recently with LPD nanoparticles to deliver functional genes and micro RNA to treat retinal diseases. Here, we review recent advances in ocular drug and gene delivery employing lipid nanoparticles.

Development and evaluation of nanoemulsifying preconcentrate of curcumin for colon delivery

The present study aimed to develop and optimize a nanoemulsifying preconcentrate formulation of curcumin with good emulsification ability and optimal globule size, for controlled targeting in colon. Content of formulation variables, namely, X₁ (Peceol), X₂ (Cremophor-EL), and X₃ (Transcutol HP), were optimized by Box-Behnken design of experiments for its impact on mean globule size (Y₁), emulsification time (Y₂), and time required for drug release (85%) in phosphate buffer (pH 7.2), t_85% (Y₃). Transmission electron micrographs confirmed that there is no coalescence among globules, with size range concordant with the globule size analysis by dynamic light scattering technique (100 nm). 3D plots indicated that concentration of formulation ingredients significantly influences the formulation properties (globule size, emulsification time, and drug release). In vitro release profile (in phosphate buffer; pH 7.2) represents the fact that more than 50% of the drug was released within initial 15 min whereas in vivo release showed limited systemic absorption (C_max 200 ng/mL) of curcumin. Stability study ensures the protection of drug in alkaline media which may further confirm the localised delivery of drug to colonic region. Study demonstrated that the nanoemulsifying preconcentrate can be a promising system for the colon specific delivery of curcumin to treat local pathologies.

Nanostructured lipid carriers: effect of solid phase fraction and distribution on the release of encapsulated materials

Emulsions, solid lipid nanoparticles (SLN), and nanostructured lipid carriers (NLC) containing a mix of liquid and solid domains are of interest as encapsulation vehicles for hydrophobic compounds. Studies of the release rate from these particles yield contradictory results: Some find that increasing the fraction of solid phase increases the rate of release and others the opposite. In this paper we study the release of encapsulated materials from lipid-based nanoparticles using Monte Carlo simulations. We find that, quite surprisingly, the release rate is largely insensitive to the size of solid domains or the fraction of solid phase. However, the distribution of the domains significantly affects the rate of release: Solid domains located at the interface with the surrounding solution inhibit transport, while nanoparticles where the solid domains are concentrated in the center enhance it. The latter can lead to release rates in NLCs that are faster than in the equivalent emulsions. We conclude that controlling the release rate from NLCs requires the ability to determine the location and distribution of the solid phase, which may be achieved through choice of the surfactants stabilizing the particles, incorporation of nucleation sites, and/or the cooling rates and temperatures.

Potential of Nanomaterials as Movers and Packers for Drug Molecules

As the development of nanotechnology has extended to the world of biomolecules, a revolution has occurred in the design and assembly of nanomaterials for drug delivery with a significant potential to impact drug efficacy and patient outcomes. Currently a number of nanomaterials are under investigation for their suitability as sustained, controlled and targeted drug carriers. Leading edge of the rapidly developing nanosciences is the development and assessment of these nanomaterials, with specific physicochemical properties different from their larger/ bulk counterparts, as vehicles for transport of small and large drug molecules. The characteristics such as size, shape, chemical composition, surface structure and charge, aggregation and agglomeration, and solubility, can greatly influence interactions of these nanostructured systems or carriers with biomembranes and cells. The selectivity and reactivity achieved due to the very small size assigns these systems with a wide spectrum of applications. In this review, nanomaterials are considered in terms of the physical attributes or pharmaceutical effects allocated by them to the all-inclusive carrier or vehicle system (s). However we will limit our discussion to lipidic and polymeric nanomaterials, the two most commonly promoted, and safe nanosystems for delivery of both, the chemical or small molecular entities (SME) and the macromolecules including genes and siRNA.Contents of Paper

Preparation and in vitro-in vivo evaluation of ofloxacin loaded ophthalmic nano structured lipid carriers modified with chitosan oligosaccharide lactate for the treatment of bacterial keratitis

The objective of this study was to explore the potential of the nanostructured lipid carriers (NLCs) modified with chitosan oligosaccharide lactate (COL) for topical ocular application. Ofloxacin (OFX) loaded NLCs were prepared by microemulsion or high shear homogenization methods. For combination of NLCs Compritol HD5 ATO was used as solid lipid, oleic acid as liquid lipid, Tween 80 as surfactant, ethanol as co-surfactant. The optimum NLCs was modified with 0.75% COL. The properties of NLCs in the absence or presence of OFX (0.3%) were characterized as zeta potential, particle size, viscosity and pH, TEM, drug loading, encapsulation efficiency and anti-microbial properties. Ex-vivo penetration/permeation studies were performed with rabbit cornea in Franz-diffusion cells. The penetration rate of OFX from NM-COL4OFX and NH-COL4OFX were significantly higher than commercial solution. Based on the selected formulations, in vivo tests were carried out by eye-drop instillation of NLCs in rabbit. The addition of COL improved the preocular residence time, controlled the drug release and enhanced the corneal bioavailability. In conclusion, OFX COL modified NLCs prepared by high shear homogenization method could be offered as a promising strategy for ocular drug delivery.

Topical delivery of ocular therapeutics: carrier systems and physical methods

OBJECTIVE

The basic concepts, major mechanisms, technological developments and advantages of the topical application of lipid-based systems (microemulsions, nanoemulsions, liposomes and solid lipid nanoparticles), polymeric systems (hydrogels, contact lenses, polymeric nanoparticles and dendrimers) and physical methods (iontophoresis and sonophoresis) will be reviewed.

KEY FINDINGS

Although very convenient for patients, topical administration of conventional drug formulations for the treatment of eye diseases requires high drug doses, frequent administration and rarely provides high drug bioavailability. Thus, strategies to improve the efficacy of topical treatments have been extensively investigated. In general, the majority of the successful delivery systems are present on the ocular surface over an extended period of time, and these systems typically improve drug bioavailability in the anterior chamber whereas the physical methods facilitate drug penetration over a very short period of time through ocular barriers, such as the cornea and sclera.

SUMMARY

Although in the early stages, the combination of these delivery systems with physical methods would appear to be a promising tool to decrease the dose and frequency of administration; thereby, patient compliance and treatment efficacy will be improved.

Nanoparticles in the ocular drug delivery

Ocular drug transport barriers pose a challenge for drug delivery comprising the ocular surface epithelium, the tear film and internal barriers of the blood-aqueous and blood-retina barriers. Ocular drug delivery efficiency depends on the barriers and the clearance from the choroidal, conjunctival vessels and lymphatic. Traditional drug administration reduces the clinical efficacy especially for poor water soluble molecules and for the posterior segment of the eye. Nanoparticles (NPs) have been designed to overcome the barriers, increase the drug penetration at the target site and prolong the drug levels by few internals of drug administrations in lower doses without any toxicity compared to the conventional eye drops. With the aid of high specificity and multifunctionality, DNA NPs can be resulted in higher transfection efficiency for gene therapy. NPs could target at cornea, retina and choroid by surficial applications and intravitreal injection. This review is concerned with recent findings and applications of NPs drug delivery systems for the treatment of different eye diseases.

Liposomes containing bile salts as novel ocular delivery systems for tacrolimus (FK506): in vitro characterization and improved corneal permeation

The objective of this study was to investigate the potential of liposomes containing bile salts as an ophthalmic delivery system for tacrolimus to improve corneal permeability. Liposomes containing bile salts, including sodium taurocholate, sodium deoxycholate, and sodium glycocholate, were produced by the thin-film dispersion method with a particle size of approximately 100 nm and an entrapment efficiency of more than 90%. Less than 5% tacrolimus was released from conventional liposomes and from liposomes containing sodium taurocholate, sodium deoxycholate, or sodium glycocholate over 12 hours. The cellular uptake of conventional liposomes was significantly higher than that of liposomes containing bile salts. However, liposomes containing bile salts exerted a 3–4-fold increase of tacrolimus in ex vivo corneal transport of tacrolimus compared with conventional liposomes. When rabbit eyes were treated with a DiI perchlorate-loaded liposome suspension, liposomes containing bile salts showed fast and sustained penetration across the cornea. Unfortunately, liposomes containing sodium deoxycholate caused toxicity or irritation to both spontaneously derived human corneal epithelial cells and the rabbit cornea. Therefore, liposomes containing sodium taurocholate and sodium glycocholate are potential carriers in ocular drug delivery systems, given their low toxicity and vastly improved permeability.

Enhanced payload of lipid nanocarriers using supersaturated solution prepared by solvent-mediated method

With the aim to effectively enhance the payload for nanocarriers, supersaturated deltamethrin (SSD) solution was prepared using the solvent-mediated method to produce lipid nanocarriers by a combination method of homogenization and sonication. In this study, deltamethrin was used as an active ingredient, corn oil was used as a lipid medium, soybean lecithin and Tween-80 were used as surfactants. At 25°C, the solubility of deltamethrin in SSD solution prepared by solvent-mediated method was 3.4 times and 1.5 times higher than that in saturated deltamethrin (SD) solution and that in SSD solution prepared by thermal-mediated method, respectively. Therefore, compared to the use of SD solution for the production of nanocarriers, the use of SSD solution significantly enhanced the payload, while keeping the encapsulation efficiency high. Particularly, nanocarriers produced from SSD solution prepared by solvent-mediated method had the higher payload of 2.1 times and 4.4 times compared with preparations using SSD solution prepared by thermal-mediated method and SD solution, respectively.

Optimization of LDL targeted nanostructured lipid carriers of 5-FU by a full factorial design

Background:

Nanostructured lipid carriers (NLC) are a mixture of solid and liquid lipids or oils as colloidal carrier systems that lead to an imperfect matrix structure with high ability for loading water soluble drugs. The aim of this study was to find the best proportion of liquid and solid lipids of different types for optimization of the production of LDL targeted NLCs used in carrying 5-Fu by the emulsification-solvent evaporation method.

Materials and Methods:

The influence of the lipid type, cholesterol or cholesteryl stearate for targeting LDL receptors, oil type (oleic acid or octanol), lipid and oil% on particle size, surface charge, drug loading efficiency, and drug released percent from the NLCs were studied by a full factorial design.

Results:

The NLCs prepared by 54.5% cholesterol and 25% of oleic acid, showed optimum results with particle size of 105.8 nm, relatively high zeta potential of –25 mV, drug loading efficiency of 38% and release efficiency of about 40%. Scanning electron microscopy of nanoparticles confirmed the results of dynamic light scattering method used in measuring the particle size of NLCs.

Conclusions:

The optimization method by a full factorial statistical design is a useful optimization method for production of nanostructured lipid carriers.

Development of solid lipid nanoparticles and nanostructured lipid carriers for improving ocular delivery of acyclovir

The objective of the present investigation was to improve the ocular bioavailability of acyclovir by incorporating it into solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). This required optimization of the process parameters, such as type of lipid, drug to lipid ratios, type and concentration of surfactants, and type and amount of liquid lipids used in the formulations. SLNs and NLCs were prepared by the modified hot oil in water microemuslion method. The prepared nanoparticles were evaluated for their particle size, zeta potential, entrapment efficiency, solid state characteristics, surface morphology, in vitro drug release, and permeation through excised cornea. The prepared nanoparticles were spherical and within the size range suitable for ocular drug delivery (400-777.56 nm). Incorporation of liquid oil in the structure of SLNs resulted in the formation of NLCs with high entrapment efficiency (25-91.64%) compared to SLNs (11.14%). The drug release from SLNs and NLCs was rather a surface-based phenomenon. In comparison to free drug solution, NLCs were capable of having faster permeation through the excised cornea indicating their potential enhanced corneal penetration properties. However, SLNs have reduced the permeation rate significantly. The results of the study suggest that SLNs can be successfully converted to physically superior NLCs, which have the potential to be developed further as ocular drug delivery systems for ACV.

Galactosylated nanostructured lipid carriers for delivery of 5-FU to hepatocellular carcinoma

The aim of the present study was to design a targeted delivery system of 5-fluorouracil (5-FU) for hepatocellular carcinoma (HCC). Lactobionic acid (LB) was conjugated to stearyl amine (SA) by a chemical reaction. The nanostructured lipid carriers (NLCs), containing LB conjugate, lecithin, glyceryl monostearate, oil [oleic acid (OA) or Labrafac 5 or 10%], and 5-FU, were dissolved in alcohol/acetone, the oil phase was added to the aqueous phase containing Tween 80 or Solutol(®) HS15 (0.25 or 0.5%), and NLCs were prepared by an emulsification-solvent diffusion method. Physical properties and drug release were studied in NLCs. The thiazolyl blue tetrazolium bromide assay was used to study the cytotoxicity of NLCs on HepG(2) cells, and the cellular uptake of NLCs was determined by flow cytometry. Fourier transform infrared spectroscopy and (1)H-NMR spectra confirmed the successful conjugation of LB and SA. The optimized NLCs consisted of 0.5% Solutol HS15 and 10% OA oil. The particle size of these nanoparticles was 139.2 nm, with a zeta potential of -18 mV, loading efficiency of 34.2%, release efficiency after 2 hours of the release test was 72.6%, and crystallinity was 0.63%. The galactosylated NLCs of 5-FU were cytotoxic on the HepG(2) cell line in a half concentration of 5-FU and seems promising in reducing 5-FU dose in HCC.

Optimizing flurbiprofen-loaded NLC by central composite factorial design for ocular delivery

The purpose of this study was to design and optimize a new topical delivery system for ocular administration of flurbiprofen (FB), based on lipid nanoparticles. These particles, called nanostructured lipid carriers (NLC), were composed of a fatty acid (stearic acid (SA)) as the solid lipid and a mixture of Miglyol(®) 812 and castor oil (CO) as the liquid lipids, prepared by the hot high pressure homogenization method. After selecting the critical variables influencing the physicochemical characteristics of the NLC (the liquid lipid (i.e. oil) concentration with respect to the total lipid (cOil/L (wt%)), the surfactant and the flurbiprofen concentration, on particle size, polydispersity index and encapsulation efficiency), a three-factor five-level central rotatable composite design was employed to plan and perform the experiments. Morphological examination, crystallinity and stability studies were also performed to accomplish the optimization study. The results showed that increasing cOil/L (wt%) was followed by an enhanced tendency to produce smaller particles, but the liquid to solid lipid proportion should not exceed 30 wt% due to destabilization problems. Therefore, a 70:30 ratio of SA to oil (miglyol + CO) was selected to develop an optimal NLC formulation. The smaller particles obtained when increasing surfactant concentration led to the selection of 3.2 wt% of Tween(®) 80 (non-ionic surfactant). The positive effect of the increase in FB concentration on the encapsulation efficiency (EE) and its total solubilization in the lipid matrix led to the selection of 0.25 wt% of FB in the formulation. The optimal NLC showed an appropriate average size for ophthalmic administration (228.3 nm) with a narrow size distribution (0.156), negatively charged surface (-33.3 mV) and high EE (∼90%). The in vitro experiments proved that sustained release FB was achieved using NLC as drug carriers. Optimal NLC formulation did not show toxicity on ocular tissues.