ABSTRACT: One of the situations in the treatment of disease is the delivery ofefficacious medication of appropriate concentration to the site of action in acontrolled and continual manner. Nanoparticle represents an importantparticulate carrier system, developed accordingly. Nanoparticles are solidcolloidal particles ranging in size from 1 to 1000 nm and composed ofmacromolecular material. Nanoparticles could be polymeric or lipidic (SLNs).Industry estimates suggest that approximately 40% of lipophilic drug candidatesfail due to solubility and formulation stability issues, prompting significantresearch activity in advanced lipophile delivery technologies. Solid lipidnanoparticle technology represents a promising new approach to lipophile drugdelivery. Solid lipid nanoparticles (SLNs) are important advancement in thisarea. The bioacceptable and biodegradable nature of SLNs makes them lesstoxic as compared to polymeric nanoparticles. Supplemented with small sizewhich prolongs the circulation time in blood, feasible scale up for large scaleproduction and absence of burst effect makes them interesting candidates forstudy. In this present review this new approach is discussed in terms of theirpreparation, advantages, characterization and special features.KEYWORDS: Nanotechnology; Colloidal carriers; Solid lipid nanoparticles;Liposomes
Nanoparticles •Nanoparticles are solid polymeric, submicronic colloidal system range between 5-300nm consisting of macromolecular substances that vary in size 10nm to 1000nm. The drug of interest is dissolved, entrapped adsorbed, attached or encapsulated into the nanoparticle matrix Depending upon the method of preparation, nanoparticle, nanosphere or nanocapsule can be obtained with different properties and release characteristics for the encapsulated therapeutic agent. Nanosphere are matrix system in which drug is physically and uniformly dispersed through out, then particles prepared by using different polymers such as polyalkylcyanoacrylate & poly lactides or they can be solid lipid nanosphere prepared using lipids like dipalmitoyl –phosphatidyl choline . Nanocapsule are ultrafine vesicular system with a diameter less than 1 mcm in which the drug is confined to a cavity surrounded by a unique polymer membrane and having aqueous or oily core containing drug substances.Types of NPS as carrier for drug & diagnostic agents • Polymeric NPS • Nanosuspensions and nanocrystals • Polymeric micelles • Ceramic NPS • liposome’s • fullerenes and dendrimers • SLNP (Solid lipid nanoparticles) • Magnetic nanoparticles • Nanoshells coated with gold • Nanomers and carbon nanotubes
Solid lipid nanoparticles: Solid lipid nanoparticles are one of the novel potential colloidal carrierssystems in the range of 100-150nm as alternative materials to polymers which is identical to oil in wateremulsion for parenteral nutrition, but the liquid lipid of the emulsion has been replaced by a solid lipid. Theyhave many advantages such as good biocompatibility, low toxicity and lipophillic drugs are better deliveredby solid lipid nano particles and the system is physically stable. Solid lipid nanoparticles may be a promisingsustained – release and drug targeting system for lipophilic CNS antitumor drugs.Types of solid nanoparticlesThe types of SLNs depend on the chemical nature of the active ingredient and lipid, the solubility of activesin the melted lipid, nature and concentration of surfactants, type of production and the productiontemperature. Therefore 3 incorporation models have been proposed for study.SLN, Type I or homogenous matrix model- The SLN Type I is derived from a solid solution of lipid andactive ingredient. A solid solution can be obtained when SLN are produced by the cold homogenationmethod. A lipid blend can be produced containing the active in a molecularly dispersed form. Aftersolidification of this blend, it is ground in its solid state to avoid or minimize the enrichment of activemolecules in different parts of the lipid nanoparticles.SLN, Type II or drug enriched shell model – It is achieved when SLN are produced by the hot technique,and the active ingredient concentration in the melted lipid is low during the cooling process of the hot o/wnanoemulsion the lipid will precipitate first, leading to a steadily increasing concentration of active moleculesin the remaining melt, an outer shell will solidify containing both active and lipid. The enrichment of the outerarea of the particles causes burst release. The percentage of active ingredient localized in the outer shell canbe adjusted in a controlled shell model is the incorporation of coenzyme Q 10.SLN, Type III or drug enriched core model- Core model can take place when the active ingredientconcentration in the lipid melt is high & relatively close to its saturation solubility. Cooling down of the hotoil droplets will in most cases reduce the solubility of the active in the melt. When the saturation solubilityexceeds, active molecules precipitate leading to the formation of a drug enriched core.
Preparation of solid lipid nanoparticles Solid lipid nanoparticles made from solid lipids or lipid blends, produced by high pressure homogenation of melted lipids disperse in an aqueous as outer phase stabilized by surfactants as Tween 80, sodium dodecyl sulphate, lecithin etc. High pressure homogenation can produce particle dispersion with a solid content of 20-30%. The drug loaded -lipid melt is dispersed in to surfactant solution to give a preemulsion. This preemulsion is passed through high pressure homogenizer to yield hot oil in water emulsion which cools down. The lipid crystallizes and forms solid lipid nanoparticles. The aqueous solid lipid nanoparticles dispersion can be incorporated in traditional in dosage forms like tablets and pelletes, for producing pellet. The water for extrusion mass is replaced by aqueous solid lipid nano particles dispersion . The pelletes disintegrate and release the SLN completely non aggregated. Alternatively, they can be produce surfactants –free using steric stabilizers (Poloxamer-188) or an or an outer phase of an increased viscosity (Ethyl cellulose solution). Solid lipid nanoparticles can be transformed to a dry product by spray drying or lyophillization. Solid lipid nanoparticles can also be produced in nano aqueous media e.g. PEG 600 production in PEG-600 gives a dispersion which can be directly filled into soft gelatin capsules
Electrolyte- and pH-stabilities of aqueous solid lipidCHARACTERIZATION nanoparticle (SLN) •The influence of artificial gastrointestinal (GI) media on OF SLN PARTICLES the physical stability of solid lipid nanoparticle (SLN) formulations consisting of different lipids and various In vitro and ex vivo surfactants/stabilizers have been investigated in vitro, with respect to ionic strength and pH. Laser diffractometry and methods for the zeta potential measurements were the techniques applied. Some SLN formulations already showed assessment of drug aggregation/particle growth in the presence of electrolytes release from SLNs In vitro at neutral pH . •Other lipid nanodispersions remained physically stable drug release with respect to the influence of electrolytes, but were pH- sensitive. It was possible to produce SLN that were GIT Dialysis tubing- (gastrointestinal tract) stable by an optimized stabilizer composition. Reverse dialysis- • There is no optimal surfactant mixture for stabilization of any lipid, e.g. SLN consisting of the lipid Cutina CP Franz diffusion cell- showed GIT stability in combination with the stabilizer sugar ester S1670, whereas the stabilization with the Ex vivo model for surfactant mixture Tween 80/Span 85 was not effective. Vice versa, the emulsifier Pluronic F68 stabilized the lipid determining permeability Compritol ATO 888 but not the lipid Imwitor 900 sufficiently to avoid aggregation of the SLN dispersion in across the gut artificial GI media. The stabilizing properties depend obviously on the specific interactions of the lipid matrix with the emulsifier, e.g. anchoring of the stabilizer on the lipid surface and density on the surface.
Advantages of Solid lipid Nanoparticle•• The solid matrix provides highest flexibility in Solid Lipid Nanoparticle Stabilitycontrolling the release profile. The slowerdegradation velocity in vivo (e.g. compared to Lipid nanoparticle stability must beliposomes) allows drug release for prolonged considered from two perspectives, theperiods. Further by coating with or attaching particle size distribution and the lipidligands to SLNs there is a increased scope of crystalline state. Particle size is a criticaldrug targetting. safety factor for parenteral administration•• High drug payload. and self life, as noted previously. Particle•• SLN formulation stable for even the years size greatly affects biodistribution andhave been developed. This is of paramountimportance with respect to the other colloidal RES clearance mechanisms. Particle sizecarrier system . also affects the physical appearance of•• SLNs particularly those in the range of the product, since the human eye can120-200nm are not taken up readily by the cells only detect light scattered by particlesof the RES (Reticulo endothelial system) and that are greater than ~ 1. The degree ofthus bypass liver and spleen filtration. polydispersity can impact particle size•• Excellent reproducibility with a cost effective growth via Ostwald ripening and canhigh pressure homogenization method as thepreparation procedure . impact the overall drug release kinetics.•• The feasibility of incorporating both hydrophilic The lipid crystalline state stronglyand hydrophobic drugs correlates with drug incorporation, drug•• The solid matrix can (but need not) protect release, and the particle geometryincorporated active ingredients/ drugs againstchemical degradation. The carrier lipids arebiodegradable and hence safe
Conclusion :Lipid nanoparticle drug delivery technology presents significant opportunities for improvingmedical therapeutics, but the technology’s potential remains unrealized. Several technologychallenges remain unsolved: appropriate control of particle size and size distribution, short-termand long-term lipid crystallinity, drug loading profile, drug release kinetics, and greater controlof biodistribution once. SLNs delivery can be an innovative way to administer molecules into thetarget site in a controlled manner by possibly overcoming or alleviating the solubility,permeability and toxicity problems associated with the respective drug molecules. High physicalstability of these systems is another advantage. On the other hand the use of solid lipids asmatrix material for drug delivery is well known from lipid pellets for oral drug delivery . SoSLNs is a new era technology which has been taken over by the pharmaceutical industry. Thepossibility of incorporating both the lipophillic and hydrophilic molecules and the possibility ofthe several administration make the SLNs delivery system all the more promising. SLNs willopen a new channel for an effective delivery of a vast variety of drug molecules includinganalgesics, antitubercular, anticancerous, antiaging, antianxiety, antibiotics, and antiviralagents to the target site.
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