Characterization and formulation optimization of solid lipid nanoparticles in vitamin K1 delivery

Background: Solid lipid nanoparticle (SLN) systems have been applied to various drugs and delivery routes. Vitamin K1 is an important cofactor for maintaining hemostasis and preventing hemorrhage. Method: Vitamin K1-loaded SLNs are systematically being developed by optimizing triglycerides and lipophilic and hydrophilic surfactants based on the size and stability of the resulting SLNs. Concentrations of the surfactants, Myverol and Pluronic, were optimized by a central composite design and response surface methodology. Vitamin K1 (phylloquinone) was used as a lipophilic drug in the SLN system to evaluate the potential for oral delivery. Results: Vitamin K1-loaded SLNs had a mean size of 125 nm and a zeta potential of ?23 mV as measured by photon correlation spectroscopy. The prepared SLNs were examined by differential scanning calorimetry and transmission electron microscopy and found to have an imperfect crystalline lattice and a spherical morphology. Effects of ultrasonication duration and drug load on the particle size and entrapment efficiency of the SLNs were also evaluated. Conclusion: More than 85% of the vitamin K1 was entrapped in SLNs when the payload was <5%. The vitamin K1 in SLNs was stable for a 54-h duration in simulated gastric and intestinal fluids. The particle size and vitamin K1 entrapped in the SLN were stable after 4 months of storage at 25°C. The results demonstrated that SLNs prepared herein can potentially be exploited as carriers for the oral delivery of vitamin K1.     

Sustained release of piroxicam from solid lipid nanoparticle as an effective anti-inflammatory therapeutics in vivo

Abstract

This study aims to investigate the solid lipid nanoparticle (SLN) as a novel vehicle for the sustained release and transdermal delivery of piroxicam, as well as to determine the anti-inflammation effect of piroxicam-loaded SLN. SLN formulation was optimized and the particle size, polydispersity index, zeta potential (ZP), encapsulation efficiency, drug release, and morphological properties were characterized. The transdermal efficiency and mechanism of the piroxicam-loaded SLNs were investigated in vitro. With the inflammation induced edema model in rat, the anti-inflammatory efficiency of piroxicam-enriched SLNs (Pir-SLNs) was evaluated. The SLN formulation was optimized as: lecithin 100?mg, glycerin monostearate 200?mg, and Tween (1%, w/w). The particle size is around 102?±?5.2?nm with a PDI of 0.262. The ZP is 30.21?±?2.05?mV. The prepared SLNs showed high entrapment efficiency of 87.5% for piroxicam. There is no interaction between piroxicam and the vehicle components. The presence of polymorphic form of lipid with higher drug content in the optimized Pir-SLNs enables the Pir-SLNs to release the drug with a sustained manner. Pir-SLNs with oleic acid as enhancer can radically diffuse into both the stratum corneum and dermal layer, as well as penetrate through the hair follicles and sebaceous glands with significantly higher density than the other control groups. Pir-SLNs promptly inhibited the inflammation since the 3rd hour after the treatment by decreasing the PGE₂ level. SLN was demonstrated to be a promising carrier for encapsulation and sustained release of piroxicam. Pir-SLN is a novel topical preparation with great potential for anti-inflammation application.     

Optimization of the lyophilization process for long-term stability of solid-lipid nanoparticles

Objectives: To optimize a lyophilization protocol for solid-lipid nanoparticles (SLNs) loaded with dexamethasone palmitate (Dex-P) and to compare the long-term stability of lyophilized SLNs and aqueous SLN suspensions at two storage conditions. Materials and Methods: The effect of various parameters of the lyophilization process on SLN redispersibility was evaluated. A three month stability study was conducted to compare changes in the particle size and drug loading of lyophilized SLNs with SLNs stored as aqueous suspensions at either 4°C or 25°C/60% relative humidity (RH). Results and Discussion: Of nine possible lyoprotectants tested, sucrose was shown to be the most efficient at achieving SLN redispersibility. Higher freezing temperatures, slower freezing rates, and longer secondary drying times were also shown to be beneficial. Loading of the SLNs with Dex-P led to slightly larger particle size and polydispersity index increases, but both parameters remained within an acceptable range. Drug loading and particle shape were maintained following lyophilization, and no large aggregates were detected. During the stability study, significant growth and drug loss were observed for aqueous SLN suspensions stored at 25°C/60% RH. In comparison, lyophilized SLNs stored at 4°C exhibited a consistent particle size and showed <20% drug loss. Other storage conditions led to intermediate results. Conclusions: A lyophilization protocol was developed that allowed SLNs to be reconstituted with minimal changes in their physicochemical properties. During a three month period, lyophilized SLNs stored at 4°C exhibited the greatest stability, showing no change in the particle size and a minimal reduction in drug retention.     

Histopathological evaluation of caffeine-loaded solid lipid nanoparticles in efficient treatment of cellulite

Context: Cellulite refers to dimpled appearance of the skin, usually located in the thighs and buttocks regions of most adult women.

Objective: The aim of this study was to formulate topically used caffeine-loaded solid lipid nanoparticle (SLN) for the treatment of cellulite.

Methods: SLNs were prepared by hot homogenization technique using Precirol® as lipid phase. The physical characterization and stability studies of SLNs as well as in vitro skin permeation and histological studies in rat skin were conducted.

Results: The mean particle size, encapsulation efficiency and loading efficiency percentages for optimized SLN formulation were 94?nm, 86 and 28%, respectively. In vitro drug release demonstrated that caffeine-loaded SLN incorporated into carbopol made hydrogel (caffeine-SLN-hydrogel) exhibited a sustained drug release compared to the caffeine hydrogel over 24?h. Caffeine-loaded SLNs showed a good stability during 12 months of storage at room temperature. The DSC and XRD results showed that caffeine was dispersed in SLN in an amorphous state. In vitro permeation studies illustrated higher drug accumulation in the skin with caffeine-SLN-hydrogel compared to caffeine hydrogel. The flux value of caffeine through rat skin in caffeine-SLN-hydrogel was 3.3 times less than caffeine hydrogel, representing lower systemic absorption. In contrast with caffeine hydrogel, the histological studies showed the complete lysis of adipocytes by administration of caffeine-SLN-hydrogel in the deeper skin layers.

Conclusion: Results of this study indicated that SLNs are promising carrier for improvement of caffeine efficiency in the treatment of cellulite following topical application on the skin.     

Histological assessment of follicular delivery of flutamide by solid lipid nanoparticles: potential tool for the treatment of androgenic alopecia

Abstract

Context: Flutamide is a potent anti-androgen with the several unwanted side effects in systemic administration, therefore, it has attracted special interest in the development of topically applied formulations for the treatment of androgenic alopecia.

Objective: The purpose of this study was to prepare and characterize the solid lipid nanoparticles (SLNs) of Flutamide for follicular targeting in the treatment of the androgenic alopecia.

Methods: Flutamide-loaded SLNs, promising drug carriers for topical application were prepared by hot melt homogenization method. Drug permeation and accumulation in the exercised rat skin and histological study on the male hamsters were performed to assess drug delivery efficiency in vitro and in vivo, respectively.

Results: The optimized Flutamide-loaded SLNs (size 198?nm, encapsulation efficiency percentage 65% and loading efficiency percentage 3.27%) exhibited a good stability during the period of at least 2 months. The results of X-ray diffraction showed Flutamide amorphous state confirming uniform drug dispersion in the SLNs structure. Higher skin drug deposition (1.75 times) of SLN formulation compared to Flutamide hydroalcoholic solution represented better localization of the drug in the skin. The in vivo studies showed more new hair follicle growth by utilizing Flutamide-loaded SLNs than Flutamide hydroalcoholic solution which could be due to the higher accumulation of SLNs in the hair follicles as well as slowly and continues release of the Flutamide through the SLNs maximizing hair follicle exposure by antiandrogenic drug.

Conclusion: It was concluded Flutamide-loaded SLN formulation can be used as a promising colloidal drug carriers for topical administration of Flutamide in the treatment of androgenic alopecia.     

Optimization of the lyophilization process for long-term stability of solid–lipid nanoparticles

Objectives: To optimize a lyophilization protocol for solid–lipid nanoparticles (SLNs) loaded with dexamethasone palmitate (Dex-P) and to compare the long-term stability of lyophilized SLNs and aqueous SLN suspensions at two storage conditions.

Materials and Methods: The effect of various parameters of the lyophilization process on SLN redispersibility was evaluated. A three month stability study was conducted to compare changes in the particle size and drug loading of lyophilized SLNs with SLNs stored as aqueous suspensions at either 4°C or 25°C/60% relative humidity (RH).

Results and Discussion: Of nine possible lyoprotectants tested, sucrose was shown to be the most efficient at achieving SLN redispersibility. Higher freezing temperatures, slower freezing rates, and longer secondary drying times were also shown to be beneficial. Loading of the SLNs with Dex-P led to slightly larger particle size and polydispersity index increases, but both parameters remained within an acceptable range. Drug loading and particle shape were maintained following lyophilization, and no large aggregates were detected. During the stability study, significant growth and drug loss were observed for aqueous SLN suspensions stored at 25°C/60% RH. In comparison, lyophilized SLNs stored at 4°C exhibited a consistent particle size and showed <20% drug loss. Other storage conditions led to intermediate results.

Conclusions: A lyophilization protocol was developed that allowed SLNs to be reconstituted with minimal changes in their physicochemical properties. During a three month period, lyophilized SLNs stored at 4°C exhibited the greatest stability, showing no change in the particle size and a minimal reduction in drug retention.     

Ceramide–palmitic acid complex based Curcumin solid lipid nanoparticles for transdermal delivery: pharmacokinetic and pharmacodynamic study

Curcumin is an important anti-inflammatory natural compound with low bioavailability which is due to poor solubility and absorption. Solid lipid nanoparticles (SLNs) loaded with Curcumin were formulated and evaluated for physical parameters and in vitro/ex vivo permeation. Further the optimised SLN was assessed for pharmacokinetic/pharmacodynamic considerations. SLNs were formulated by emulsion-solvent evaporation technique and evaluated for physical properties and in vitro drug release. Selected SLNs were evaluated for stability and then characterised for pharmacokinetic parameters and anti-inflammatory activity with reference to a commercial formulation. Spherical SLNs were obtained in the size range of 102–156 nm with negative potential. C-SLN category has shown highest entrapment efficiency. The order of drug release was S-SLN > G-SLN > C-SLN. Selected SLN formulation C-SLN-3 has shown good stability under various conditions. C-SLN-3 has demonstrated highest drug permeation through human skin and 171.623 mg drug content permeated in 24 h. It has also shown lowest lag time 0.375 h. Similarly, it has shown maximum value for C_max in in vivo determination and increased the bioavailability upto 68.12%. C-SLN-3 provided 90.75% edema inhibition in 6 h. Present study shows that nature of lipids and its physical-chemical properties are critical for SLN formulation and can be used for designing better drug delivery systems with optimum transdermal permeation.     

Solid lipid nanoparticle: an efficient carrier for improved ocular permeation of voriconazole

This research focuses on the fabrication and evaluation of solid lipid nanoparticles (SLNs) for improved ocular delivery of voriconazole (VCZ). Compritol and palmitic acid were selected as lipid carriers based on drug solubility and partitioning behavior. Poloxamer and soya lecithin were the choice for surfactant, while sodium taurocholate was used as a co-surfactant. The particle sizes of the SLNs determined by zetasizer and transmission electron microscopy (TEM) were found within the desired range. The in vitro release study of SLNs exhibited a sustained-release property of the drug. The ex vivo studies displayed enhanced corneal drug permeation from SLNs in comparison to the drug suspension. Further, the corneal hydration studies, histopathology and Hen's Egg Test Chorio Allantoic Membrane (HETCAM) assay confirmed the non-irritancy of the nano-formulation. The in vivo study confirmed the higher availability of VCZ (from SLN) in aqueous humor with minimal nasolacrymal drainage in contrast to the drug suspension. A good in-vitro in-vivo correlation (IVIVC) further confirmed the potential of SLN as an effective carrier for ocular delivery.     

Oral solid compritol 888 ATO nanosuspension of simvastatin: optimization and biodistribution studies

The purpose of the present investigation was to develop solid lipid nanoparticles (SLNs) of simvastatin in order to enhance its oral bioavailability by minimizing its first-pass metabolism. To achieve our goal, SLNs were prepared by solvent injection technique and optimized by 2(3) full factorial experimental design using Design Expert software. The SLN formulations were optimized for amount of compritol, concentration of poloxamer, and volume of acetone in order to achieve desired responses of particle size, entrapment efficiency (EE), and cumulative drug release (CDR). Response surface plots were constructed to study the influence of each variable on each response and the interactions between any two variables were also analyzed. Formulation F(10) with particle size of 271.18?nm, % EE of 68.16% and % CDR of 76.23%, and highest desirability value of 0.645 was selected as optimized formulation. The optimized formulation was evaluated for biodistribution and pharmacokinetics by technetium-99m (Tc-99m) radiolabeling technique in mice. The relative bioavailability of simvastatin from optimized SLNs was found to be 220%, substantiating the protective action of SLNs against liver metabolism. However, though the drug initially bypassed the liver metabolism, simvastatin continuously entered in liver to exert its therapeutic action that was evidenced by biodistribution study.     

Oral solid compritol 888 ATO nanosuspension of simvastatin: optimization and biodistribution studies

The purpose of the present investigation was to develop solid lipid nanoparticles (SLNs) of simvastatin in order to enhance its oral bioavailability by minimizing its first-pass metabolism. To achieve our goal, SLNs were prepared by solvent injection technique and optimized by 2³ full factorial experimental design using Design Expert software. The SLN formulations were optimized for amount of compritol, concentration of poloxamer, and volume of acetone in order to achieve desired responses of particle size, entrapment efficiency (EE), and cumulative drug release (CDR). Response surface plots were constructed to study the influence of each variable on each response and the interactions between any two variables were also analyzed. Formulation F₁₀ with particle size of 271.18?nm, % EE of 68.16% and % CDR of 76.23%, and highest desirability value of 0.645 was selected as optimized formulation. The optimized formulation was evaluated for biodistribution and pharmacokinetics by technetium-99m (Tc-99m) radiolabeling technique in mice. The relative bioavailability of simvastatin from optimized SLNs was found to be 220%, substantiating the protective action of SLNs against liver metabolism. However, though the drug initially bypassed the liver metabolism, simvastatin continuously entered in liver to exert its therapeutic action that was evidenced by biodistribution study.     

Targeted SLNs for management of HIV-1 associated dementia

Context: HIV-1 associated dementia (HAD) is an evolving disease in the category of neurological disorders.

Objective: Nifedipine-loaded solid lipid nanoparticles (SLNs) were developed and coated with Tween 80 to facilitate enhanced brain drug delivery for the treatment of HAD.

Materials and methods: SLNs were prepared using solvent injection method. Lipids consisted of tristearin, hydrogenated soya phosphatidylcholine (HSPC) (1.5:1 w/w). Nifedipine was model drug in this study. Tween 80 (0.5% v/v) was taken as key modulator. SLNs were characterized for particle shape, size, zeta potential, entrapment efficiency, in vitro drug release, DNA fragmentation, cytotoxicity potential and in vivo studies.

Results: The SLNs (plain and coated) were found to be in nanometric in size (～120?nm) with more than 70% entrapment efficiency. In vitro drug release profile reflected sustained release up to 48?h. Tween 80-coated SLNs showed higher percentage of DNA fragmentation in vitro and enhanced cell viability in sulforhodamine assay (rat cortical cells) as compared to plain drug and uncoated SLNs due to facilitated uptake of SLNs and reversal of P-gp efflux by virtue of Tween 80. Biodistribution study performed on vital organs, i.e. brain, heart, liver, spleen, lungs and kidney showed increased accumulation of Tween 80-coated SLNs in the brain.

Discussion and conclusion: Tween 80 enhanced localization of SLNs in the brain as compared to uncoated SLNs. This approach can be employed effectively to transport chemotherapeutics across the BBB for management of HIV-1 associated dementia and other ailments.     

Enhanced intestinal absorption and bioavailability of raloxifene hydrochloride via lyophilized solid lipid nanoparticles

The current oral therapy with raloxifene hydrochloride (RXH) is less effective due to its poor bioavailability (only 2%). Henceforth, an attempt was made to investigate the utility of triglyceride (trimyristin, tripalmitin and tristearin) based solid lipid nanoparticles (SLNs) for improved oral delivery of RXH. The SLN formulations prepared were evaluated for particle size, zeta potential and % entrapment and the optimized formulation was lyophilized. Solid state characterization studies unravel the transformation of RXH to amorphous or molecular state from the native crystalline form. Further the in situ perfusion studies carried out in rat intestine reveal the potential of SLN for enhanced permeation of raloxifene HCl across gastrointestinal barrier. To derive the conclusions, in vivo pharmacokinetic study was conducted in rats to assess the bioavailability of RXH from SLN formulation compared to drug suspension. Overall a twofold increase in bioavailability with SLN formulations confer their potential for improved oral delivery of RXH.     

Lipid nanoparticles of zaleplon for improved oral delivery by Box–Behnken design: optimization,in vitro and in vivo evaluation

Purpose: Zaleplon (ZL) is a hypnotic drug prescribed for the management of insomnia and convulsions. The oral bioavailability of ZL was low (～30%) owing to poor water solubility and hepatic first-pass metabolism. The cornerstone of this investigation is to develop and optimize solid lipid nanoparticles (SLNs) of ZL with the aid of Box–Behnken design (BBD) to improve the oral bioavailability.

Methods: A design space with three formulation variables at three levels were evaluated in BBD. Amount of lipid (A₁), amount of surfactant (A₂) and concentration of co-surfactant (%) (A₃) were selected as independent variables, whereas, particle size (B₁), entrapment efficiency (B₂) and zeta potential (ZP, B₃) as responses. ZL-SLNs were prepared by hot homogenization with ultrasonication method and evaluated for responses to obtain optimized formulation. Morphology of nanoparticles was observed under SEM. DSC and XRD studies were examined to understand the native crystalline behavior of drug in SLN formulations. Further, in vivo studies were performed in Wistar rats.

Results: The optimized formulation with 132.89?mg of lipid, 106.7?mg of surfactant and 0.2% w/v of co-surfactant ensued in the nanoparticles with 219.9?±?3.7?nm of size, ?25.66?±?2.83?mV surface charge and 86.83?±?2.65% of entrapment efficiency. SEM studies confirmed the spherical shape of SLN formulations. The DSC and XRD studies revealed the transformation of crystalline drug to amorphous form in SLN formulation. In conclusion, in vivo studies in male Wistar rats demonstrated an improvement in the oral bioavailability of ZL from SLN over control ZL suspension.

Conclusions: The enhancement in the oral bioavailability of ZL from SLNs, developed with the aid of BBD, explicated the potential of lipid-based nanoparticles as a potential carrier in improving the oral delivery of this poorly soluble drug.     

Methotrexate-conjugated L-lysine coated iron oxide magnetic nanoparticles for inhibition of MCF-7 breast cancer cells

Methotrexate (MTX), a stoichiometric inhibitor of dihydrofolate reductase enzyme, is a chemotherapeutic agent for treating a diversity of neoplasms. In this study, we design and developed a new formulation of MTX that serves as drug carrier and examined its cytotoxic effect in vitro. This target drug delivery system is dependent on the release of the MTX within the lysosomal compartment. The iron oxide magnetic nanoparticles (IONPs) were first surface-coated with L-lysine and subsequently conjugated with MTX through amidation between the carboxylic acid end groups on MTX and the amine groups on the IONPs surface. MTX-conjugated L-lysine coated IONPs (F-Lys-MTX NPs) was characterized by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, vibrating sample magnetometer, and transmission electron microscopy techniques. The cytotoxicity of the void of MTX and F-Lys-MTX NPs were compared to each other by MTT assay of the treated MCF-7 cell lines. The results showed that the ζ-potential of F-Lys-MTX NPs was about ?5.49?mV and the average size was 43.72?±?4.73?nm. Model studies exhibited the release of MTX via peptide bond cleavage in the presence of proteinase K and at low pH. These studies specify that F-Lys-MTX NPs have a very remarkable anticancer effect, for breast cancer cell lines.     

Methotrexate-grafted-oligochitosan micelles as drug carriers: synthesis and biological evaluations

The novel amphiphilic derivatives of Methotrexate–chitosan oligosaccharide (MTX–CHO) with different molar feeding ratios of MTX were synthesized. The degree of MTX substitution ranged from 4.47 to 13.5 %. MTX–CHO copolymer formed micelles with an average size of 134.6 ± 14.52 to 236.6 ± 30.01 nm, and zeta potential of 20 ± 5 to 16.8 ± 7.74 mV. The critical micelle concentration was found to range from 125 to 0.56 mg/l. Analysis of micelles with different degree of substitutions (DSs) revealed that the size of micelles decreased by increasing DS while zeta potential was reduced. Release study indicated that drug content had effect on the release rate. With increasing amount of loaded drug in the micelle, release rate was decreased. Drug loaded and unloaded MTX–CHO micelles showed significant cytotoxicity on MDA-MB-231. Loaded micelle was more effective than unloaded one which indicated that conjugation could reduce efficacy of MTX. The viability of MDA-MB-231 in presence of drug loaded micelles was significantly decreased and cell viability at 1 µg/ml was 45.17 ± 9 % while the viability of unloaded micelles was 91.86 ± 9.88. These phenomena make MTX–CHO micelles as a good candidate for hydrophobic anticancer drug carrier.     

Evaporative Drying of Aqueous Dispersions of Solid Lipid Nanoparticles

Solid lipid nanoparticles (SLNs) have been proposed as alternative colloidal drug carriers. SLNs are obtained by dispersing warm oil-in-water microemulsions into cold water. The aim of this research was to investigate an evaporative drying process for aqueous dispersions of SLNs. For this purpose, a special apparatus, namely, a thermostatic minidesiccator having alumina as the drying medium, was designed to carry out the evaporative drying at a controlled temperature. Besides the water removal kinetics, the mean particle size and the size distribution of SLNs were measured during the drying with the aim of detecting the highest temperature at which the drying process can be carried out without significantly affecting the SLN average diameter. The SLN dispersions were evaluated with and without a hydrophilic excipient, commonly used as a cryoprotector (trehalose). The drying temperature of 10°C was found to be the most suitable for obtaining SLNs as a powder, maintaining almost the same size as that of the SLNs in dispersion.     

Evaporative drying of aqueous dispersions of solid lipid nanoparticles.

Solid lipid nanoparticles (SLNs) have been proposed as alternative colloidal drug carriers. SLNs are obtained by dispersing warm oil-in-water microemulsions into cold water. The aim of this research was to investigate an evaporative drying process for aqueous dispersions of SLNs. For this purpose, a special apparatus, namely a thermostatic minidesiccator having alumina as the drying medium, was designed to carry out the evaporative drying at a controlled temperature. Besides the water removal kinetics, the mean particle size and the size distribution of SLNs were measured during the during with the aim of detecting the highest temperature at which the drying process can be carried out without significantly affecting the SLN average diameter. The SLN dispersions were evaluated with and without a hydrophilic excipient, commonly used as a cryoprotector (trehalose). The drying temperature of 10 degrees C was found to be the most suitable for obtaining SLNs as a powder, maintaining almost the same size as that of the SLNs in dispersion.     

Physicochemical characterization techniques for solid lipid nanoparticles: principles and limitations

Solid lipid nanoparticles (SLNs) are gaining importance due to numerous advantages they offer as a drug delivery system. SLN incorporate poorly soluble drugs, proteins, biologicals, etc. SLN are prepared by techniques like high-pressure homogenization, sonication and employs a wide range of lipids and surfactants. Physicochemical characterization techniques include particle size analysis, zeta potential and determination of crystallinity/polymorphism. Furthermore, drug loading and drug entrapment efficiency are common parameters used to test the efficiency of SLN. Most importantly, the functionality assay of SLN is essential to predict the activity and performance in vivo. The review presented discusses the importance of SLN in drug delivery with emphasis on principles and limitations associated with their physicochemical characterization.