Solid lipid nanoparticles bearing flurbiprofen for transdermal delivery

Optimization of Chitosan-Decorated Solid Lipid Nanoparticles for Improved Flurbiprofen Transdermal Delivery

Transdermal delivery is a potential alternative route to oral administration for drugs associated with stomach discomfort, such as flurbiprofen, a widely nonsteroidal anti-inflammatory drug (NSAID). This study aimed to design solid lipid nanoparticle (SLN) transdermal formulations of flurbiprofen. Chitosan-coated SLNs were prepared by the solvent emulsification method, and their properties and permeation profiles across the excised rat skin were characterized. The particle size of uncoated SLNs was at 695 ± 4.65 nm, which increased to 714 ± 6.13, 847 ± 5.38, and 900 ± 8.65 nm upon coating with 0.05, 0.10, and 0.20% of chitosan, respectively. The drug association efficiency was improved when a higher concentration of chitosan was employed over SLN droplets that endowed a higher affinity of flurbiprofen with chitosan. The drug release was significantly retarded as compared to the uncoated entities and followed non-Fickian anomalous diffusion that was depicted by "n" values of >0.5 and <1. Also, the total permeation of chitosan-coated SLNs (F7-F9) was significantly higher than that of the noncoated formulation (F5). Overall, this study has successfully designed a suitable carrier system of chitosan-coated SLNs that provide insight into the current conventional therapeutic approaches and suggest new directions for the advancements in transdermal drug delivery systems for improved permeation of flurbiprofen.

Parametric Drug Release Optimization of Anti-Inflammatory Drugs by Gold Nanoparticles for Topically Applied Ocular Therapy

Eye drops represent 90% of all currently used ophthalmic treatments. Only 0.02% of therapeutic molecules contained in eye drops reach the eye anterior chamber despite their high concentration. The tear film efficiently protects the cornea, reducing access to the target. Thereby, the increase in the drug bioavailability and efficiency must come from the mucoadhesion optimization of the drug delivery system. The gold nanoparticles, used as a drug delivery system in this study, already showcased ultrastable and mucoadhesive properties. The goal was to study the gold nanoparticles' ability to release two specific ophthalmic drugs, flurbiprofen and ketorolac. The parameters of interest were those involving the loading conditions, the gold nanoparticles properties, and the release experimental conditions. The drug release was measured using an in vitro model based on dialysis bags coupled with UV-visible spectroscopy. Gold nanoparticles showed an ability to release different molecules, whether hydrophobic or hydrophilic, in passive or active drug release environments. Based on these preliminary results, gold nanoparticles could represent a promising drug delivery system for ketorolac and flurbiprofen when topically applied through eye drops.

Formulation of Topical Flurbiprofen Solid Lipid Nanoparticle Gel Formulation Using Hot Melt Extrusion Technique

Hot melt extrusion (HME) has been used for the formulation of topical solid lipid nanoparticle (SLN) gel without using any other size reduction technique including high pressure homogenization or sonication. SLN formulation solely using HME has not been applied to other drugs except IBU. Therefore, the purpose of the present study was to formulate FLB SLN solely using HME technique and evaluate the SLN formulation in inflammation animal model. Stable 0.5% w/v FLB SLN gel with particle size < 250 nm, PI < 0.3 and EE of > 98% was prepared. Differential scanning calorimetry (DSC) thermogram showed that the drug was converted to amorphous form in the HME process. Additionally, rheological studies demonstrated that FLB SLN gel and marketed FLB gel showed shear thinning property. FLB SLN formulation showed significantly (p < 0.05) higher peak force required to spread the formulation as compared to marketed FLB formulation. Stability studies showed that FLB SLN gel was stable for a month at room temperature and 2-4°C. Moreover, in vitro permeation test (IVPT) and ex vivo skin deposition study results revealed that FLB SLN gel showed significant (p < 0.05) increase in drug deposition in dermal layer and drug permeation as compared to control marketed formulation. Further, in vivo anti-inflammatory study showed equivalent inhibition of rat paw edema using 0.5% w/v FLB SLN gel which has 10 times less strength compared to control formulation. Overall, FLB SLN formulation was successfully manufactured solely using HME technique which resulted in enhanced the skin permeation of FLB and superior anti-inflammatory activity.

Preparation of Terbinafin-Encapsulated Solid Lipid Nanoparticles Containing Antifungal Carbopol® Hydrogel with Improved Efficacy: In Vitro, Ex Vivo and In Vivo Study

The present research was aimed to develop a terbinafin hydrochloride (TH)-encapsulated solid lipid nanoparticles (SLNs) hydrogel for improved antifungal efficacy. TH-loaded SLNs were obtained from glyceryl monostearate (lipid) and Pluronic® F68 (surfactant) employing high-pressure homogenization. The ratio of drug with respect to lipid was optimized, considering factors such as desired particle size and highest percent encapsulation efficiency. Lyophilized SLNs were then incorporated in the hydrogel prepared from 0.2–1.0% w/v carbopol 934P and further evaluated for rheological parameters. The z-average, zeta potential and polydispersity index were found to be 241.3 nm, −15.2 mV and 0.415, respectively. The SLNs show a higher entrapment efficiency of about 98.36%, with 2.12 to 6.3602% drug loading. SEM images, XRD and the results of the DSC, FTIR show successful preparation of SLNs after freeze drying. The TH-loaded SLNs hydrogel showed sustained drug release (95.47 ± 1.45%) over a period of 24 h. The results reported in this study show a significant effect on the zone of inhibition than the marketed formulation and pure drug in Candida albicans cultures, with better physical stability at cooler temperatures. It helped to enhance skin deposition inthe ex vivostudy and improved, in vitro and in vivo, the antifungal activity.

Lipid-Drug Conjugates and Nanoparticles for the Cutaneous Delivery of Cannabidiol

Lipid nanoparticles are currently used to deliver drugs to specific sites in the body, known as targeted therapy. Conjugates of lipids and drugs to produce drug-enriched phospholipid micelles have been proposed to increase the lipophilic character of drugs to overcome biological barriers. However, their applicability at the topical level is still minimal. Phospholipid micelles are amphiphilic colloidal systems of nanometric dimensions, composed of a lipophilic nucleus and a hydrophilic outer surface. They are currently used successfully as pharmaceutical vehicles for poorly water-soluble drugs. These micelles have high in vitro and in vivo stability and high biocompatibility. This review discusses the use of lipid-drug conjugates as biocompatible carriers for cutaneous application. This work provides a metadata analysis of publications concerning the conjugation of cannabidiol with lipids as a suitable approach and as a new delivery system for this drug.

Tacrolimus-Loaded Solid Lipid Nanoparticle Gel: Formulation Development and In Vitro Assessment for Topical Applications

The currently available topical formulations of tacrolimus have minimal and variable absorption, elevated mean disposition half-life, and skin irritation effects resulting in patient noncompliance. In our study, we fabricated tacrolimus-loaded solid lipid nanoparticles (SLNs) that were converted into a gel for improved topical applications. The SLNs were prepared using a solvent evaporation method and characterized for their physicochemical properties. The particle size of the SLNs was in the range of 439 nm to 669 nm with a PDI of ≤0.4, indicating a monodispersed system. The Zeta potential of uncoated SLNs (F1–F5) ranged from −25.80 to −15.40 mV. Those values reverted to positive values for chitosan-decorated formulation (F6). The drug content and entrapment efficiency ranged between 0.86 ± 0.03 and 0.91 ± 0.03 mg/mL and 68.95 ± 0.03 and 83.68 ± 0.04%, respectively. The pH values of 5.45 to 5.53 depict their compatibility for skin application. The surface tension of the SLNs decreased with increasing surfactant concentration that could increase the adherence of the SLNs to the skin. The release of drug from gel formulations was significantly retarded in comparison to their corresponding SLN counterparts (p ≤ 0.05). Both SLNs and their corresponding gel achieved the same level of drug permeation, but the retention of the drug was significantly improved with the conversion of SLNs into their corresponding gel formulation (p ≤ 0.05) due to its higher bioadhesive properties.

Brain targeted delivery of rapamycin using transferrin decorated nanostructured lipid carriers

Introduction: Recent studies showed that rapamycin, as a mammalian target of rapamycin (mTOR) inhibitor, could have beneficial therapeutic effects for the central nervous system (CNS) related diseases. However, the immunosuppressive effect of rapamycin as an adverse effect, the low water solubility, and the rapid in vivo degradation along with the blood-brain barrier-related challenges restricted the clinical use of this drug for brain diseases. To overcome these drawbacks, a transferrin (Tf) decorated nanostructured lipid carrier (NLC) containing rapamycin was designed and developed. Methods: Rapamycin-loaded cationic and bare NLCs were prepared using solvent diffusion and sonication method and well characterized. The optimum cationic NLCs were physically decorated with Tf. For in vitro study, the MTT assay and intracellular uptake of nanoparticles on U-87 MG glioblastoma cells were assessed. The animal biodistribution of nanoparticles was evaluated by fluorescent optical imaging. Finally, the in vivo effect of NLCs on the immune system was also studied. Results: Spherical NLCs with small particle sizes ranging from 120 to 150 nm and high entrapment efficiency of more than 90%, showed ≥80% cell viability. More importantly, Tf-decorated NLCs in comparison with bare NLCs, showed a significantly higher cellular uptake (97% vs 60%) after 2 hours incubation and further an appropriate brain accumulation with lower uptake in untargeted tissue in mice. Surprisingly, rapamycin-loaded NLCs exhibited no immunosuppressive effect. Conclusion: Our findings proposed that the designed Tf-decorated NLCs could be considered as a safe and efficient carrier for targeted brain delivery of rapamycin which may have an important value in the clinic for the treatment of neurological disorders.

Features, applications, and sustainability of lipid nanoparticles in cosmeceuticals

Cosmeceuticals are a branch of cosmetic products that forms a bridge between cosmetic and drug products. It is a fast-growing branch of the cosmetic industry, especially after the introduction of novel formulation and manufacturing techniques such as lipid nanoparticles (LNPs). These LNPs-based cosmeceutical products offer several advantages such as enhanced bioavailability of cosmeceutical active ingredients (CAIs), improved aesthetic appeal, and stability of the final products. However, the use of these LNPs may raise some concerns about possible side effects of these LNPs and potential hazards to the customer’s health. Accordingly, an update that focuses on the use of this important branch of nanoparticles is necessary since most review papers are dealing with all types of nanocarriers in the same review with little focus on LNPs. Therefore, in the current review, a detailed analysis of the advantages and disadvantages of LNPs in this field was highlighted, to emphasize the LNPs-based cosmeceuticals on the market, as well as the potential risk posed by LNPs on exposure and recently introduced regulatory guidelines to address them. In addition, if these products can be a candidate as products that meet the sustainable development goals raised by the UN are discussed.

Photodegradation of Anti-Inflammatory Drugs: Stability Tests and Lipid Nanocarriers for Their Photoprotection

The present paper provides an updated overview of the methodologies applied in photodegradation studies of non-steroidal anti-inflammatory drugs. Photostability tests, performed according to international standards, have clearly demonstrated the photolability of many drugs belonging to this class, observed during the preparation of commercial forms, administration or when dispersed in the environment. The photodegradation profile of these drugs is usually monitored by spectrophotometric or chromatographic techniques and in many studies the analytical data are processed by chemometric procedures. The application of multivariate analysis in the resolution of often-complex data sets makes it possible to estimate the pure spectra of the species involved in the degradation process and their concentration profiles. Given the wide use of these drugs, several pharmaceutical formulations have been investigated to improve their photostability in solution or gel, as well as the pharmacokinetic profile. The use of lipid nanocarriers as liposomes, niosomes or solid lipid nanoparticles has demonstrated to both minimize photodegradation and improve the controlled release of the entrapped drugs.

Solid Lipid Nanoparticles for Topical Drug Delivery: Mechanisms, Dosage Form Perspectives, and Translational Status

Solid lipid nanoparticles (SLNs) have shown potential as a novel lipid-based drug delivery system for the topical applications of innumerable therapeutic compounds. However, the mechanisms governing the absorption and cellular uptake of SLNs through topical route, along with the mechanism of drug release from SLNs are still ambiguous, and require further investigation. In addition, the selection of an appropriate dosage form/formulation base is essential for ease of application of SLNs and to enhance dermal and transdermal delivery. Upscaling and regulatory approvals are other challenges that may impede the clinical translation of SLNs. Therefore, this review focusses on different mechanisms involved in skin penetration and cellular uptake of SLNs. This is followed by a comprehensive discussion on the physicochemical properties of SLNs including various formulation and dosage form factors, which might influence the absorption of SLNs through the skin. Finally, translational status with respect to scale-up and regulatory aspects are also discussed. This review will be useful to researchers with an interest in topical applications of SLNs for the efficient delivery of drugs and cosmetics.

Skin Permeation of Nanoparticles: Mechanisms Involved and Critical Factors Governing Topical Drug Delivery

Transdermal route has been an ever sought-after means of drug administration, regarded as being the most convenient and patient compliant. However, skin poses a great barrier to the entry of the external particles including bacteria, viruses, allergens, and drugs as well (mostly hydrophilic or high molecular weight drugs), consequent to its complex structure and composition. Among the various means of enhancing drug permeation through the skin, e.g. chemical permeation enhancers, electroporation, thermophoresis, etc. drug delivery through nanoparticles has been of great interest. Current literature reports a vast number of nanoparticles that have been implicated for drug delivery through the skin. However, a precise account of critical factors involved in drug delivery and mechanisms concerning the permeation of nanoparticles through the skin is necessary. The purpose of this review is to enumerate the factors crucial in governing the prospect of drug delivery through skin and classify the skin permeation mechanisms of nanoparticles. Among the various mechanisms discussed are the ones governed by principles of kinetics, osmotic gradient, adhesion, hydration, diffusion, occlusion, electrostatic interaction, thermodynamics, etc. Among the most common factors affecting skin permeation of nanoparticles that are discussed include size, shape, surface charge density, composition of nanoparticles, mechanical stress, pH, etc.

Solid Lipid Nanoparticles: A Promising Nanomaterial in Drug Delivery

The solid lipid nanoparticles (SLNs) usually consists of active drug molecules along with solid lipids, surfactants, and/or co-surfactants. They possess some potential features such as nano-size, surface with a free functional group to attach ligands, and as well they prove safe homing for both lipophilic as well as hydrophilic molecules. As far as synthesis is concerned, SLNs can be prepared by employing various techniques viz., homogenization techniques (e.g., high-pressure, high-speed, cold, or hot homogenization), spray drying technique, ultrasonication, solvent emulsification, double emulsion technique, etc. Apart from this, they are characterized by different methods for determining various parameters like particle-size, polydispersity-index, surface morphology, DSC, XRD, etc. SLNs show good stability as well as the ability for surface tailoring with the specific ligand, which makes them a suitable candidate in the therapy of numerous illnesses, especially in the targeting of the cancers. In spite of this, SLNs have witnessed their application via various routes e.g., oral, parenteral, topical, pulmonary, rectal routes, etc. Eventually, SLNs have also shown great potential for delivery of gene/DNA, vaccines, as well as in cosmeceuticals. Hence, SLNs have emerged as a promising nanomaterial for efficient delivery of various Active Pharmaceutical Ingredients (APIs).

Development of novel pH-sensitive nanoparticle-based transdermal patch for management of rheumatoid arthritis

Aim: To formulate and evaluate a pH-responsive nanoparticle (NP)-based patch for efficient transdermal delivery of flurbiprofen against rheumatoid arthritis. Materials & methods: Nanoprecipitation technique was used for preparation of NPs and central composite design was employed for optimization purposes. Optimized NPs were loaded into the transdermal patch by the solvent evaporation method. Results: Prepared NPs exhibited an average size of 69 nm, while NPs loaded onto the transdermal patch showed sustained release and high permeation through the skin. In in vivo studies, the prepared carrier system elucidated high therapeutic potential in both acute and chronic inflammatory models as evident from the results of behavioral, radiological, histopathological and antioxidant analyses. Conclusion: The flurbiprofen-loaded pH-sensitive NP-based transdermal patch has the potential to manage rheumatoid arthritis effectively.

Pharmacokinetic and pharmacodynamic studies of etodolac loaded vesicular gels on rats by transdermal delivery

BACKGROUND

The present study includes the development of liposomal and ethosomal gels for transdermal delivery to overcome the side effects associated with oral route.

METHODS

The liposomes and ethosomes were prepared by 32 factorial design using film hydration and cold methods, respectively. Different concentrations of liposomal (ETO-LG) and ethosomal (ETO-EG) gels were prepared at 1%, 2 and 3% (w/v) using carbopol 940 NF. 1%w/v ETO-LG & ETO-EG were optimized upon rheological studies of prepared gels. The optimized gels were further characterized for various physicochemical properties and biophysical studies using FTIR, pharmacokinetic (PK) and pharmacodynamic (PD) studies. The pharmacodynamic activity was performed using carrageenan paw oedema model. The prepared vesicular gels were compared with 45% v/v ethanolic ETO-solution and marketed gel PROXYM® in all the characteristic parameters.

RESULTS

The pharmacokinetic study reveals that the half life of etodolac in ETO-EG was 1.56 folds whereas ETO-LG showed 1.31 folds higher than PROXYM®. The mean residence time (MRT) of etodolac in ETO-EG and ETO-LG is increased in 1.57 and 1.25 folds, respectively, when compared to PROXYM®. The ETO-EG showed higher percentage reduction in oedema (81.67%) compared to other test products.

CONCLUSION

The pharmacokinetic and pharmacodynamic studies indicated that the vesicular gels show better results compared to PROXYM®. The correlation coefficient value between PK and PD was found to be 0.9635. Graphical abstract ᅟ.

Etodolac transdermal cubosomes for the treatment of rheumatoid arthritis: ex vivo permeation and in vivo pharmacokinetic studies

In this study, transdermal etodolac-loaded cubosomes were developed in order to relieve patient pain and joints stiffness by providing stable etodolac concentration at the targeting sites through controlled drug delivery via the noninvasive skin route with more sustaining and less frequent dosing. Different ratios and percentages of poloxamer 407 and monoolein were used to formulate the cubosomes using emulsification and homogenization processes. The etodolac-loaded cubosomes showed particle size values ranging from 135.95 to 288.35 nm and zeta potential values ranging from -18.40 to -36.10 mV. All the cubosomes offered an encapsulation efficiency value of about 100% and showed drug loading capacity ranging from 1.28 to 6.09%. The in vitro drug release studies revealed a controlled drug release profile with a drug release rate up to 15.08%/h. Increasing poloxamer concentration in etodolac-loaded cubosomes resulted in nanoparticles with less particle size and faster drug release. The particles exhibited cubic and hexagonal shapes. The DSC and X-ray analysis demonstrated that the drug was encapsulated in the cubosomes bicontinuous structures in amorphous form. In addition, investigated cubosomes exhibited fast drug penetration through excited mice skin followed by slower drug penetration for up to 24 h. The pharmacokinetic study in human volunteers showed that the selected etodolac-loaded cubosomes enhanced the bioavailability of etodolac as compared to the oral capsules (266.11%) with evidence of longer half-life and higher MRT that reached 18.86 and 29.55 h, respectively. The etodolac-loaded cubosomes propose a promising system for treatment of arthritis simply through skin application.

Advances in Hybrid Polymer-Based Materials for Sustained Drug Release

The use of biomaterials composed of organic pristine components has been successfully described in several purposes, such as tissue engineering and drug delivery. Drug delivery systems (DDS) have shown several advantages over traditional drug therapy, such as greater therapeutic efficacy, prolonged delivery profile, and reduced drug toxicity, as evidenced by in vitro and in vivo studies as well as clinical trials. Despite that, there is no perfect delivery carrier, and issues such as undesirable viscosity and physicochemical stability or inability to efficiently encapsulate hydrophilic/hydrophobic molecules still persist, limiting DDS applications. To overcome that, biohybrid systems, originating from the synergistic assembly of polymers and other organic materials such as proteins and lipids, have recently been described, yielding molecularly planned biohybrid systems that are able to optimize structures to easily interact with the targets. This work revised the biohybrid DDS clarifying their advantages, limitations, and future perspectives in an attempt to contribute to further research of innovative and safe biohybrid polymer-based system as biomaterials for the sustained release of active molecules.

Ex vivo permeation of carprofen from nanoparticles: A comprehensive study through human, porcine and bovine skin as anti-inflammatory agent

The purpose of this study was the development of poly(d,l-lactide-co-glycolide) acid (PLGA) nanoparticles (NPs) for the dermal delivery of carprofen (CP). The developed nanovehicle was then lyophilized using hydroxypropyl-β-cyclodextrin (HPβCD) as cryoprotectant. The ex vivo permeation profiles were evaluated using Franz diffusion cells using three different types of skin membranes: human, porcine and bovine. Furthermore, biomechanical properties of skin (trans-epidermal water loss and skin hydration) were tested. Finally, the in vivo skin irritation and the anti-inflammatory efficacy were also assayed. Results demonstrated the achievement of NPs 187.32 nm sized with homogeneous distribution, negatively charged surface (-23.39 mV) and high CP entrapment efficiency (75.38%). Permeation studies showed similar diffusion values between human and porcine skins and higher for bovine. No signs of skin irritation were observed in rabbits. Topically applied NPs significantly decreased in vivo inflammation compared to the reference drug in a TPA-induced mouse ear edema model. Thus, it was concluded that NPs containing CP may be a useful tool for the dermal treatment of local inflammation.

Pharmaceutical and biomedical applications of lipid-based nanocarriers

Increasing attention is being given to lipid nanocarriers (LNs) as drug delivery systems, due to the advantages offered of a higher biocompatibility and lower toxicity compared with polymeric nanoparticles. Many administration routes are being investigated for LNs, including topical, oral and parenteral ones. LNs are also proposed for specific applications such as cancer treatment, gene therapy, diagnosis and medical devices production. However, the high number of published research articles does not match an equal amount of patents. A recent Review of ours, published in Pharmaceutical Patent Analyst, reported the patents proposing novel methods for the production of LNs. This review work discusses recent patents, filed in 2007-2013 and dealing with the industrial applications of lipid-based nanocarriers for the vectorization of therapeutically relevant molecules, as well as biotech products such as proteins, gene material and vaccines, in the pharmaceutical, diagnostic and biomedical areas.

Enhanced bioavailability of orally administered flurbiprofen by combined use of hydroxypropyl-cyclodextrin and poly(alkyl-cyanoacrylate) nanoparticles

Flurbiprofen was formulated into nanoparticle suspension to improve its oral bioavailability. Hydroxypropyl-β-cyclodextrin inclusion-flurbiprofen complex (HP-β-CD-FP) was prepared, then incorporating this complex into poly(alkyl-cyanoacrylate) (PACA) nanoparticles. HP-β-CD-FP-PACA nanoparticle was prepared by the emulsion solvent polymerization method. The zeta potential was -26.8 mV, the mean volume particle diameter was 134 nm, drug encapsulation efficiency was 53.3 ± 3.6 % and concentration was 1.5 mg/mL. The bioavailability of flurbiprofen from optimized nanoparticles was assessed in male Wistar rats at a dose of 15 mg/kg. As compared to the flurbiprofen suspension, 211.6 % relative bioavailability was observed for flurbiprofen nanoparticles. The reduced particle size and increased surface area may contribute to improve oral bioavailability of flurbiprofen.

Lipid nanoparticles as novel delivery systems for cosmetics and dermal pharmaceuticals

INTRODUCTION

Lipid nanoparticles are innovative carrier systems developed as an alternative to traditional vehicles such as emulsions, liposomes and polymeric nanoparticles. Solid lipid nanoparticles (SLN) and the newest nanostructured lipid carriers (NLC) show important advantages for dermal application of cosmetics and pharmaceuticals.

AREA COVERED

This article focuses on the main features of lipid nanoparticles, in terms of their preparation and recent advancements. A detailed review of the literature is presented, introducing the importance of these systems in the topical delivery of drugs and active substances.

EXPERT OPINION

Lipid nanoparticles are able to enhance drug penetration into the skin, allowing increased targeting to the epidermis and consequently increasing treatment efficiency and reducing the systemic absorption of drugs and cosmetic actives. The complete biodegradation of lipid nanoparticles and their biocompatible chemical nature have secured them the title of 'nanosafe carriers.' SLN and NLC represent a new technological era, which has been taken over by the cosmetic and pharmaceutical industry, which will open new channels for effective topical delivery of substances.

Nanoparticles and microparticles for skin drug delivery

Skin is a widely used route of delivery for local and systemic drugs and is potentially a route for their delivery as nanoparticles. The skin provides a natural physical barrier against particle penetration, but there are opportunities to deliver therapeutic nanoparticles, especially in diseased skin and to the openings of hair follicles. Whilst nanoparticle drug delivery has been touted as an enabling technology, its potential in treating local skin and systemic diseases has yet to be realised. Most drug delivery particle technologies are based on lipid carriers, i.e. solid lipid nanoparticles and nanoemulsions of around 300 nm in diameter, which are now considered microparticles. Metal nanoparticles are now recognized for seemingly small drug-like characteristics, i.e. antimicrobial activity and skin cancer prevention. We present our unpublished clinical data on nanoparticle penetration and previously published reports that support the hypothesis that nanoparticles >10nm in diameter are unlikely to penetrate through the stratum corneum into viable human skin but will accumulate in the hair follicle openings, especially after massage. However, significant uptake does occur after damage and in certain diseased skin. Current chemistry limits both atom by atom construction of complex particulates and delineating their molecular interactions within biological systems. In this review we discuss the skin as a nanoparticle barrier, recent work in the field of nanoparticle drug delivery to the skin, and future directions currently being explored.

Novel method to label solid lipid nanoparticles with 64cu for positron emission tomography imaging

Solid lipid nanoparticles (SLNs) are submicrometer (1-1000 nm) colloidal carriers developed in the past decade as an alternative system to traditional carriers (emulsions, liposomes, and polymeric nanoparticles) for intravenous applications. Because of their potential as drug carriers, there is much interest in understanding the in vivo biodistribution of SLNs following intravenous (i.v.) injection. Positron emission tomography (PET) is an attractive method for investigating biodistribution but requires a radiolabeled compound. In this work, we describe a method to radiolabel SLN for in vivo PET studies. A copper specific chelator, 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N',N'',N'''-tetraacetic acid (BAT), conjugated with a synthetic lipid, was incorporated into the SLN. Following incubation with (64)CuCl(2) for 1 h at 25 °C in 0.1 M NH(4)OAc buffer (pH 5.5), the SLNs (∼150 nm) were successfully radiolabeled with (64)Cu (66.5% radiolabeling yield), exhibiting >95% radiolabeled particles following purification. The (64)Cu-SLNs were delivered intravenously to mice and imaged with PET at 0.5, 3, 20, and 48 h post injection. Gamma counting was utilized post imaging to confirm organ distributions. Tissue radioactivity (% injected dose/gram, %ID/g), obtained by quantitative analysis of the images, suggests that the (64)Cu-SLNs are circulating in the bloodstream after 3 h (blood half-life ∼1.4 h), but are almost entirely cleared by 48 h. PET and gamma counting demonstrate that approximately 5-7%ID/g (64)Cu-SLNs remain in the liver at 48 h post injection. Stability assays confirm that copper remains associated with the SLN over the 48 h time period and that the biodistribution patterns observed are not from free, dissociated copper. Our results indicate that SLNs can be radiolabeled with (64)Cu, and their biodistribution can be quantitatively evaluated by in vivo PET imaging and ex vivo gamma counting.

Carriers in the topical treatment of skin disease

Topical drug application is less prone to severe systemic side-effects than systemic application. Starting with the liposomes, various types of nanosized and microsized drug carriers have been developed to increase the notoriously low penetration of active agents into the skin, which limits not only the topical therapy of skin disease but also transdermal therapy. Today, liposome- and microsponge-based preparations are approved for dermatomycosis, acne and actinic keratosis. Under investigation are drug carriers such as lipid nanoparticles, polymeric particles, dendrimers, and dendritic-core multi-shell nanotransporters. According to the rapidly increasing research in this field, both in academia and industry, a breakthrough appears likely, once stability problems (nanoparticles) and safety concerns (dendrimers) are overcome. Technical approaches and results of in vitro, ex vivo and in vivo testing are described, taking into account pharmacokinetic, efficacy and safety aspects.

Solid lipid nanoparticles: a modern formulation approach in drug delivery system

Solid lipid nanoparticles are at the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery, clinical medicine and research, as well as in other varied sciences. Due to their unique size-dependent properties, lipid nanoparticles offer the possibility to develop new therapeutics. The ability to incorporate drugs into nanocarriers offers a new prototype in drug delivery that could be used for secondary and tertiary levels of drug targeting. Hence, solid lipid nanoparticles hold great promise for reaching the goal of controlled and site specific drug delivery and hence have attracted wide attention of researchers. This review presents a broad treatment of solid lipid nanoparticles discussing their advantages, limitations and their possible remedies. The different types of nanocarriers which were based on solid lipid like solid lipid nanoparticles, nanostructured lipid carriers, lipid drug conjugates are discussed with their structural differences. Different production methods which are suitable for large scale production and applications of solid lipid nanoparticles are described. Appropriate analytical techniques for characterization of solid lipid nanoparticles like photon correlation spectroscopy, scanning electron microscopy, differential scanning calorimetry are highlighted. Aspects of solid lipid nanoparticles route of administration and their biodistribution are also incorporated. If appropriately investigated, solid lipid nanoparticles may open new vistas in therapy of complex diseases.

Multivesicular Liposomes Bearing Celecoxib-β-Cyclodextrin Complex for Transdermal Delivery

In our work depot delivery systems of celecoxib were developed using multivesicular liposomes. Moreover, the solubility of celecoxib was enhanced by complexing drug with cyclodextrin to overcome the limitation of conventional therapy. The multivesicular liposomes (MVLs) bearing celecoxib-beta -cyclodextrin inclusion complex were prepared by reverse phase evaporation method, and multilamellar vesicles (MLVs)-bearing drug complex was prepared by the cast film method. The formulations were characterized for vesicle size, encapsulation efficiency, and in vitro drug release. In vivo performance of multivesicular liposomes bearing celecoxib-beta -cyclodextrin inclusion complex was evaluated by assessing anti-inflammatory activity using carrageenan-induced rat paw edema volume method. The results were compared with that of celecoxib-cyclodextrin complex and MLVs containing celecoxib-beta -cyclodextrin inclusion complex in equal amounts. Phase solubility studies for the celecoxib-beta -cyclodextrin inclusion complex clearly indicated an increase in aqueous solubility of celecoxib with an increase in beta -CD concentration. The in vitro release studies reveal that MLVs release more than 80% drug within 48 hr whereas MVL formulations release nearly the same amount of drug in 120 hr. In vivo data reveal that reduction in paw volume with MVL formulation was not rapid and fast, but the effect was maintained for prolonged periods, and even after 24 hr there was 40.7 +/- 3.40% reduction in paw volume. MVL formulation showed more sustained and prolonged anti-inflammatory effect compared with plain drug and MLVs. We concluded that multivesicular liposome can be successfully utilized for the sustained delivery of celecoxib.

Enhanced transdermal delivery of acyclovir sodium via elastic liposomes

The elastic liposomes bearing acyclovir sodium were prepared for its enhanced transdermal delivery by conventional rotary evaporation method and characterized for various parameters such as vesicle shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, polydispersity index, turbidity and in vitro release pattern. Permeability studies of acyclovir sodium incorporated in elastic liposomes were performed across artificial membranes and rat skin. Skin permeation potential of the developed formulation was assessed using confocal laser scanning microscopy, that revealed an enhanced permeation of the formulation to the deeper layers of the skin (up to 160 microm) following channel like pathways. Skin permeation profile of elastic liposomal formulation bearing acyclovir sodium was observed and the investigations revealed an enhanced transdermal flux (6.21 +/- 1.8 microg/cm(2)/hr) and decreased lag time (0.6 hr) for acyclovir sodium. The obtained flux was nearly 2.0 and 6.3 times higher than conventional liposomal formulation bearing acyclovir sodium and plain drug solution, respectively (p < 0.01). The elastic liposomal formulation for transdermal delivery of acyclovir sodium provides better transdermal flux, higher entrapment efficiency, ability as a self-penetration enhancer and effectiveness for transdermal delivery as compared with conventional liposomes. In vivo studies showed that on transdermal application of elastic liposomes, the concentration of acyclovir sodium in plasma was found to be 105 +/- 9.4 ng/ml after 24 hr which is about 4.2 times compared with conventional liposomes. Thus it is concluded that the elastic liposomes may be promising vehicles for the transdermal delivery of acyclovir sodium.

Effect of solid lipid nanoparticles formulation compositions on their size, zeta potential and potential for in vitro pHIS-HIV-hugag transfection

PURPOSE

This work was conducted to determine model equations describing the effect of solid lipid nanoparticles (SLN) formulation compositions on their size and zeta potential using the face-centered central composite design and to determine the effect of SLN formulation compositions on the potential for in vitro pHIS-HIV-hugag transfection.

MATERIALS AND METHODS

SLN were prepared by the hot high pressure homogenization technique using cetylpalmitate as lipid matrix at varying concentrations of Tween 80 and Span 85 mixture, dimethyldioctadecyl ammonium bromide (DDAB) and cholesterol. Size and zeta potential used as responses of the design were measured at pH 7.0. The model equations were accepted as statistical significance at p value of less than 0.05. Ability of SLN to form complex with pHIS-HIV-hugag was evaluated by electrophoretic mobility shift assay. In vitro cytotoxicity of SLN was studied in HeLa cells using alamar blue bioassay. The potential of SLN for in vitro pHIS-HIV-hugag transfection was also determined in HeLa cells by western blot technique.

RESULTS

SLN possessed diameter in a range of 136-191 nm and zeta potential 11-61 mV depending on the concentrations of surfactant mixture, DDAB and cholesterol. The regression analysis showed that the model equations of responses fitted well with quadratic equations. The ability of SLN to form complex with pHIS-HIV-hugag was also affected by formulation compositions. In vitro cytotoxicity results demonstrated that HeLa cells were not well tolerant of high concentrations of SLN but still survived in a range of 100-200 microg/ml of SLN in culture medium. The results of transfection study showed ability of SLN to use as a vector for in vitro pHIS-HIV-hugag transfection. However, their potential for in vitro transfection was lower than the established transfection reagent.

CONCLUSIONS

Size and zeta potential of SLN could be predicted from their quadratic model equations achieved by combination of three variables surfactant, DDAB and cholesterol concentrations. In addition, these variables also affected the potential of SLN as a vector for in vitro pHIS-HIV-hugag transfection. The results here provide the framework for further study involving the SLN formulation design for DNA delivery.