Solid lipid micro-particles carrying insulin formed by solvent-in-water emulsion-diffusion technique

The study aimed to produce solid lipid insulin-loaded micro-particles by the solvent-in-water emulsion-diffusion technique, using isobutyric acid as solvent phase, glyceryl monostearate or cetyl palmitate as lipid, soya lecithin and taurodeoxycholate as emulsifiers. Isobutyric acid, a partially water-miscible solvent with low toxicity, was used due to its high insulin-solubilization capacity. Solid lipid micro-particles of spherical shape were prepared by simple dilution of the emulsion with water. To increase the lipid load the process was conducted at 50 degrees C, and in order to reach sub-micron size, a high-shear homogeniser was used. Insulin encapsulation efficiency was about 80%. Analysis of microsphere content after processing showed that insulin did not undergo any chemical modification within the micro-particles. The in vitro release of insulin from the micro-particles was very low, and an initial burst effect of 20% of the dose was observed. After treatment of the solid lipid micro-particles with pepsin solution, an insulin loss of about 24% of the total englobed insulin was observed. The solid lipid micro-particles appear to have interesting possibilities as delivery systems for oral administration of insulin.     

Solid lipid nanoparticles for pulmonary delivery of insulin

Growing attention has been given to the potential of pulmonary route as an alternative for non-invasive systemic delivery of therapeutic agents. In this study, novel nebulizer-compatible solid lipid nanoparticles (SLNs) for pulmonary drug delivery of insulin were developed by reverse micelle-double emulsion method. The influences of the amount of sodium cholate (SC) and soybean phosphatidylcholine (SPC) on the deposition properties of the nanoparticles were investigated. Under optimal conditions, the entrapment delivery (ED), respirable fraction (RF) and nebulization efficiency (NE) of SLNs could reach 96.53, 82.11 and 63.28%, respectively, and Ins-SLNs remained stable during nebulization. Fasting plasma glucose level was reduced to 39.41% and insulin level was increased to approximately 170 microIU/ml 4h after pulmonary administration of 20 IU/kg Ins-SLNs. A pharmacological bioavailability of 24.33% and a relative bioavailability of 22.33% were obtained using subcutaneous injection as a reference. Incorporating fluorescent-labelled insulin into SLNs, we found that the SLNs were effectively and homogeneously distributed in the lung alveoli. These findings suggested that SLNs could be used as a potential carrier for pulmonary delivery of insulin by improving both in vitro and in vivo stability as well as prolonging hypoglycemic effect, which inevitably resulted in enhanced bioavailability.     

Solid lipid nanoparticles loaded with insulin by sodium cholate-phosphatidylcholine-based mixed micelles: preparation and characterization

Solid lipid nanoparticles (SLNs) loaded with insulin-mixed micelles (Ins-MMs) were prepared by a novel reverse micelle-double emulsion method, in which sodium cholate (SC) and soybean phosphatidylcholine (SPC) were employed to improve the liposolubility of insulin, and the mixture of stearic acid and palmitic acid were employed to prepare insulin loaded solid lipid nanoparticles (Ins-MM-SLNs). Some of the formulation parameters were optimized to obtain high quality nanoparticles. The particle size and zeta potential measured by photon correlation spectroscopy (PCS) were 114.7 ± 4.68 nm and −51.36 ± 2.04 mV, respectively. Nanospheres observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed extremely spherical shape. The entrapment efficiency (EE%) and drug loading capacity (DL%) determined with high performance liquid chromatogram (HPLC) by modified ultracentrifuge method were 97.78 ± 0.37% and 18.92 ± 0.07%, respectively. Differential scanning calorimetry (DSC) of Ins-MM-SLNs indicated no tendency of recrystallisation. The core-shell drug loading pattern of the SLNs was confirmed by fluorescence spectra and polyacrylamide gel electrophoresis (PAGE) which also proved the integrity of insulin after being incorporated into lipid carrier. The drug release behavior was studied by in situ and externally sink method and the release pattern of drug was found to follow Weibull and Higuchi equations. Results of stability evaluation showed a relatively long-term stability after storage at 4 °C for 6 months. In conclusion, SLNs with small particle size, excellent physical stability, high entrapment efficiency, good loading capacity for protein drug can be produced by this novel reverse micelle-double emulsion method in present study.     

Solid lipid nanoparticles: Production,characterization and applications

Solid lipid nanoparticles (SLN) have attracted increasing attention during recent years. This paper presents an overview about the selection of the ingredients, different ways of SLN production and SLN applications. Aspects of SLN stability and possibilities of SLN stabilization by lyophilization and spray drying are discussed. Special attention is paid to the relation between drug incorporation and the complexity of SLN dispersions, which includes the presence of alternative colloidal structures (liposomes, micelles, drug nanosuspensions, mixed micelles, liquid crystals) and the physical state of the lipid (supercooled melts, different lipid modifications). Appropriate analytical methods are needed for the characterization of SLN. The use of several analytical techniques is a necessity. Alternative structures and dynamic phenomena on the molecular level have to be considered. Aspects of SLN administration and the in vivo fate of the carrier are discussed.     

Solid lipid nanoparticles: production, characterization and applications

Solid lipid nanoparticles (SLN) have attracted increasing attention during recent years. This paper presents an overview about the selection of the ingredients, different ways of SLN production and SLN applications. Aspects of SLN stability and possibilities of SLN stabilization by lyophilization and spray drying are discussed. Special attention is paid to the relation between drug incorporation and the complexity of SLN dispersions, which includes the presence of alternative colloidal structures (liposomes, micelles, drug nanosuspensions, mixed micelles, liquid crystals) and the physical state of the lipid (supercooled melts, different lipid modifications). Appropriate analytical methods are needed for the characterization of SLN. The use of several analytical techniques is a necessity. Alternative structures and dynamic phenomena on the molecular level have to be considered. Aspects of SLN administration and the in vivo fate of the carrier are discussed.     

微乳化技术制备固体脂质纳米粒微乳化技术制备固体脂质纳米粒

目的采用微乳化技术制备固体脂质纳米粒（SLN）。方法以硬脂酸为油相，卵磷脂为乳化剂，乙醇为助乳化剂，蒸馏水为水相，按不同比例混合制备微乳。通过改变卵磷脂与乙醇的配比（K_m），绘制出不同K_m值下的三元相图。从中选择适宜的微乳，将其分散于冷水中制备SLN。考察了工艺因素和处方因素对SLN制备和SLN质量的影响。在单因素考察的基础上，采用正交设计优化工艺，并对优化所得的工艺进行重现性考察。结果水相温度（T_w）、微乳的温度（T_i）、微乳注入速度（r_d）均直接影响SLN的制备，其中水相温度是影响SLN质量的重要因素；微乳各组分的配比、微乳与水相的比例也对SLN的质量有一定影响。结论微乳化技术制备固体脂质纳米粒是可行的。     

Solid lipid nanoparticles (SLNs) derived from para-acyl-calix[9]-arene: preparation and stability

A study of the parameters relating to the preparation of para-acyl-calix[9]arene-based solid lipid nanoparticles (SLNs) has been undertaken. Dynamic light scattering and electron microscopy have shown that the particle size varies between 85 and 215 nm depending on the acyl chain length. Parameters, including the organic solvent, amphiphile concentration and the presence of a co-surfactant affect the size of the SLNs obtained significantly. In contrast, stirring speed and solution viscosity have no effect. The ionic strength of the suspension has been shown to affect SLN stability in a salt-dependent manner. Ultrasonic and ultraviolet and 80°C treatment of the SLN suspensions have no effect on the SLN stability. The SLNs are unstable with respect to freezing–defreezing cycles, but can be reconstituted using mono- or disaccharides as cryoprotectants. Importantly, the temporal stability of these suspensions in water has been shown to be superior to 6 months. With regard to protein interactions, no SLN aggregation was observed in the presence of human serum albumin, with formation of a monolayer of albumin on the surface of the SLNs. Encapsulation was shown using acridine as a fluorescent probe.     

Solid lipid nanoparticles (SLNs) derived from para-acyl-calix[9]-arene: preparation and stability

A study of the parameters relating to the preparation of para-acyl-calix[9]arene-based solid lipid nanoparticles (SLNs) has been undertaken. Dynamic light scattering and electron microscopy have shown that the particle size varies between 85 and 215 nm depending on the acyl chain length. Parameters, including the organic solvent, amphiphile concentration and the presence of a co-surfactant affect the size of the SLNs obtained significantly. In contrast, stirring speed and solution viscosity have no effect. The ionic strength of the suspension has been shown to affect SLN stability in a salt-dependent manner. Ultrasonic and ultraviolet and 80°C treatment of the SLN suspensions have no effect on the SLN stability. The SLNs are unstable with respect to freezing–defreezing cycles, but can be reconstituted using mono- or disaccharides as cryoprotectants. Importantly, the temporal stability of these suspensions in water has been shown to be superior to 6 months. With regard to protein interactions, no SLN aggregation was observed in the presence of human serum albumin, with formation of a monolayer of albumin on the surface of the SLNs. Encapsulation was shown using acridine as a fluorescent probe.     

Solid lipid nanoparticles bearing oxybenzone: In-vitro and in-vivo evaluation

In the present project, Solid Lipid Nanoparticles (SLNs) bearing oxybenzone were prepared by ethanol injection method to improve its effectiveness as sunscreen. SLNs were characterized for particle size, polydispersity index, zeta potential and surface morphology. The optimized SLNs bearing oxybenzone were incorporated into water-removable cream base and compared with SLNs unloaded water-removable cream base for in vitro and in vivo parameters. Cream base formulation containing SLNs (Csd) with 5% oxybenzone showed slow drug release and better sun protecting factor (more than 25) compared to cream base containing 5% oxybenzone. Confocal Laser Scanning Microscopy was used to visualize the distribution of developed formulations in skin. CLSM indicated prolonged retention of SLNs in the stratum corneum as compared to plain cream base. These studies revealed that the cream base bearing SLNs exhibited good skin retention as well as enhanced sun protection effect compared to cream base.     

Solid lipid nanoparticles and nanostructured lipid carriers--innovative generations of solid lipid carriers

The first generation of solid lipid carrier systems in nanometer range, Solid Lipid Nanoparticles (SLN), was introduced as an alternative to liposomes. SLN are aqueous colloidal dispersions, the matrix of which comprises of solid biodegradable lipids. SLN are manufactured by techniques like high pressure homogenization, solvent diffusion method etc. They exhibit major advantages such as modulated release, improved bioavailability, protection of chemically labile molecules like retinol, peptides from degradation, cost effective excipients, improved drug incorporation and wide application spectrum. However there are certain limitations associated with SLN, like limited drug loading capacity and drug expulsion during storage, which can be minimized by the next generation of solid lipids, Nanostructured lipid carriers (NLC). NLC are lipid particles with a controlled nanostructure that improves drug loading and firmly incorporates the drug during storage. Owing to their properties and advantages, SLN and NLC may find extensive application in topical drug delivery, oral and parenteral administration of cosmetic and pharmaceutical actives. Cosmeceuticals is emerging as the biggest application target of these carriers. Carrier systems like SLN and NLC were developed with a perspective to meet industrial needs like scale up, qualification and validation, simple technology, low cost etc. This paper reviews present status of SLN and NLC as carrier systems with special emphasis on their application in Cosmeceuticals; it also gives an overview about various manufacturing techniques of SLN and NLC.     

Solid lipid nanoparticles: an oral bioavailability enhancer vehicle

Introduction: The therapeutic efficacy of perorally administered drugs is often obscured by their poor oral bioavailability (BA) and low metabolic stability in the gastrointestinal tract (GIT). Solid lipid nanoparticles (SLNs) have emerged as potential BA enhancer vehicles for various Class II, III and IV drug molecules.

Area covered: This review examines the recent advancements in SLN technology, with regards to oral drug delivery. The discussion critically examines the effect of various key constituents on SLN absorption and their applications in oral drug delivery. The relationship between the complexity of absorption (and various factors involved during absorption, including particle size), stability and the self-emulsifying ability of the lipids used has been explored.

Expert opinion: The protective effect of SLNs, coupled with their sustained/controlled release properties, prevents drugs/macromolecules from premature degradation and improves their stability in the GIT. An extensive literature survey reveals that direct peroral administration of SLNs improves the BA of drugs by 2- to 25-fold. Overall, the ease of large-scale production, avoidance of organic solvents and improvement of oral BA make SLNs a potential BA enhancer vehicle for various Class II, III and IV drugs.     

Solid lipid nanoparticles: an oral bioavailability enhancer vehicle

INTRODUCTION: The therapeutic efficacy of perorally administered drugs is often obscured by their poor oral bioavailability (BA) and low metabolic stability in the gastrointestinal tract (GIT). Solid lipid nanoparticles (SLNs) have emerged as potential BA enhancer vehicles for various Class II, III and IV drug molecules. AREA COVERED: This review examines the recent advancements in SLN technology, with regards to oral drug delivery. The discussion critically examines the effect of various key constituents on SLN absorption and their applications in oral drug delivery. The relationship between the complexity of absorption (and various factors involved during absorption, including particle size), stability and the self-emulsifying ability of the lipids used has been explored. EXPERT OPINION: The protective effect of SLNs, coupled with their sustained/controlled release properties, prevents drugs/macromolecules from premature degradation and improves their stability in the GIT. An extensive literature survey reveals that direct peroral administration of SLNs improves the BA of drugs by 2- to 25-fold. Overall, the ease of large-scale production, avoidance of organic solvents and improvement of oral BA make SLNs a potential BA enhancer vehicle for various Class II, III and IV drugs.     

Alginate microspheres prepared by internal gelation: development and effect on insulin stability

Recombinant human insulin was encapsulated within alginate microspheres by the emulsification/internal gelation technique with the objective of preserving protein stability during encapsulation procedure. The influence of process and formulation parameters was evaluated on the morphology and encapsulation efficiency of insulin. The in vitro release of insulin from microspheres was studied under simulated gastrointestinal conditions and the in vivo activity of protein after processing was assessed by subcutaneous administration of extracted insulin from microspheres to streptozotocin-induced diabetic rats. Microspheres mean diameter, ranging from 21 to 287 microm, decreased with the internal phase ratio, emulsifier concentration, mixer rotational speed and increased with alginate concentration. Insulin encapsulation efficiency, near 75%, was not affected by emulsifier concentration, mixer rotational speed and zinc/insulin hexamer molar ratio but decreased either by increasing internal phase ratio and calcium/alginate mass ratio or by decreasing acid/calcium molar ratio and alginate concentration. A high insulin release, above 75%, was obtained at pH 1.2 and under simulated intestinal pH a complete dissolution of microspheres occurred. Extracted insulin from microspheres decreased hyperglycemia of diabetic rats proving to be bioactive and showing that encapsulation in alginate microspheres using the emulsification/internal gelation is an appropriate method for protein encapsulation.     

Solid lipid nanoparticles: formulation factors affecting cell transfection capacity

Since solid lipid nanoparticles (SLNs) were introduced as non-viral transfection systems, very few reports of their use for gene delivery have been published. In this work different formulations based on SLN-DNA complexes were formulated in order to evaluate the influence of the formulation components on the "in vitro" transfection capacity. SLNs composed by the solid lipid Precirol ATO 5, the cationic lipid DOTAP and the surfactant Tween 80, and SLN-DNA complexes prepared at different DOTAP/DNA ratios were characterized by studying their size, surface charge, DNA protection capacity, transfection and cell viability in HEK293 cultured cells. The incorporation of Tween 80 allowed for the reduction of the cationic lipid concentration. The formulations prepared at DOTAP/DNA ratios 7/1, 5/1 and 4/1 provided almost the same transfection levels (around 15% transfected cells), without significant differences between them (p>0.05). Other assayed formulations presented lower transfection. Transfection activity was dependent on the DOTAP/DNA ratio since it influences the DNA condensation into the SLNs. DNA condensation is a crucial factor which conditions the transfection capacity of SLNs, because it influences DNA delivery from nanoparticles, gene protection from external agents and DNA topology.     

Solid lipid nanoparticles: a possible vehicle for zinc oxide and octocrylene

An efficient sunscreen formulation shows good absorption in the relevant UV range. Efficacy also means that the UV absorber must be easily incorporated in any kind of formulation. In this study, a chemical absorber, octocrylene, and one of the most important physical blockers, zinc oxide, could be successfully incorporated into Solid Lipid Nanoparticle (SLN) systems which themselves have UV blocking potential similar to physical sunscreens, and remained stable for a period of 360 days while providing UVA and UVB protection. Crystalline structure related to the chemical nature of the solid lipid is a key factor to decide whether a sunscreening agent will be expelled or incorporated in the long-term and for a controlled optimization of active ingredient incorporation and loading, intensive characterization of the physical state of the lipid particles was highly essential. Thus, FT-IR, NMR, XRD and DSC analyses were performed and the results did not indicate stability problems. pH values of the SLN systems were found to be between 5.4-5.9 in all formulations which may be buffered by the skin. Transpore test results proved the UV blocking potential of the SLNs with not any active ingredient and the synergistic effects by the incorporation of molecular sunscreens. Therefore, concentration of molecular sunscreens in the formulations was decreased to 0.6%. UVA and UVB screening potentials of octocrylene and zinc oxide formulations were compared in the 290-400 nm wavelength region. Zinc oxide loaded SLN suspensions were found to be more effective in the UVA region while octocrylene loaded ones performed better in the UVB region.     

Solid lipid nanoparticles and nanostructured lipid carrier-based nanotherapeutics in treatment of psoriasis: a comparative study

Background: The present work focuses on the development of ultra-small solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) encapsulating cyclosporine and calcipotriol, further incorporated into gel, increasing their penetration through the skin.

Research design and methods: Developed SLN and NLC were characterized regarding particle size, zeta potential, %entrapment efficiency and dispersed into carbopol 934P-NF gel. Gel was further characterized for rheological behavior and spreadability. Ex vivo dermatokinetic by tape stripping method, in vitro efficacy on HaCaT cell lines and in vivo efficacy on imiquimod induced psoriatic model in mice were evaluated.

Results: Ultra-small (size<100 nm) particles were formed with high entrapment efficiency and spherical morphology. Ex vivo dermatokinetic studies revealed deeper and confined drug penetration of lipid formulation gel in epidermal layers as compared to free drug. In vitro study on HaCaT cell lines depicted higher uptake and high efficacy owing to decrease in cell viability for NLC. The anti-psoriatic efficacy in BALB/c mice (evaluated on basis of cytokine levels and skin morphology) highlighted potential of drug-loaded NLC significantly higher as compared to drug loaded SLN and marketed formulation Betagel.

Conclusions: The study demonstrated that NLC gel had higher efficacy in psoriatic management and hold promise for further exploration.     

固体脂质纳米粒的研究进展

目的综述固体脂质纳米粒的最新研究进展。方法以国内外大量有代表性的论文为依据,将固体脂质纳米粒的制备方法、特性分析、药物载入、药物释放及应用情况进行了概括,指出了发展前景和尚待解决的问题。结果固体脂质纳米粒的多种制备方法各有优、缺点,调整制备参数可调整药物的包封率和释药曲线。结论固体脂质纳米粒可供多途径给药,是极有发展前景的新型给药系统。     

异维A酸固体脂质纳米粒的制备和稳定性考察

目的采用固体脂质纳米粒作为异维A酸载体,以提高其稳定性。方法采用纳米乳法制备异维A酸固体脂质纳米粒。结果制得的固体脂质纳米粒为球形粒子,平均粒径为53．23nm,包封率〉97％。25℃和40℃避光贮存6个月,含量和包封率均无明显变化。     

Influence of the stabilizer coating layer on the purification and freeze-drying of poly(D,L-lactic acid) nanoparticles prepared by an emulsion-diffusion technique

Abstract

In this study, the purification by cross-flow filtration (CFF) and freeze drying of poly(D, L-lactic acid) (PLA) nanoparticles prepared by an emulsion-diffusion technique using poly(vinyl alcohol) (PVAL) or poloxamer 188 (P-188) were investigated. The stability of the suspensions was correlated to the affinity of the stabilizers for the nanoparticle surface, the resistance of the coating layer to continuous filtration and to freeze—thawing procedures. The results indicated a clear difference between the two stabilizers, suggesting that the nature of the coating layer has a very important role during CFF and freeze-drying. Nanoparticles prepared with PVAL were filtered and freeze-dried without nanoparticle fusion. This behaviour was attributed to the formation of a stable thick layer (similar to that found for polystyrene latex). In contrast, aggregation of nanoparticles was observed during CFF for the batches prepared with P-188, indicating that the polypropylene oxide blocks present in the copolymer have little affinity for the PLA surface. However, these suspensions were successfully recovered when using stabilizer solutions as diafiltration media, suggesting a dynamic exchange between the P-188–adsorbed chains and those of the identical polymer remaining in the bulk solution. The presence of P-188 did not prevent nanoparticle aggregation after freeze-drying. Therefore, the use of cryoprotectants was necessary. Aggregation may have been due to an increase in the solubility of P-188 in the bulk solution, which provokes a destabilization of the suspension by desorption and partial coverage of the surface. The best cryoprotectants were found to be sugars containing glucose units. The cryoprotective effect was related to the hydrogen bonding capability of these sugars, which prevented aggregation by dehydration of P-188 forcing it to the PLA surface.