EXPERIMENT 4SOLID LIPID NANOPARTICLESSafety informationThe chemicals listed below will be used in this experiment. The likely hazardsassociated with each of the chemicals are noted and recommended procedures forhandling are given. You must read this page and the experimental descriptioncarefully before starting the experiment and before coming into the laboratory. Noteany potential hazards and adopt precautions as your safe lab practice. When you aresatisfied that you understand any possible difficulties that might arise and therecommended procedures for dealing with them, sign the declaration and have itinitialled by a demonstrator. This must be done prior commencing lab work. At thebeginning of the lab session demonstrators will quiz you about the safety informationand experimental procedure in order to identify your ability to work safely andefficiently. If you fail to prove ability for safe and efficient work you will not beallowed to start lab practical. Please note, that it is your own responsibility tocomplete the lab practical during time that is allocated to you. Be sure to requestinformation or help if you are in doubt on any point. ChemicalHazard PrecautionsGenerally,irritants torespiratoryHarmful ifCauses seriousMay causeirritation.Suspectedfertility orPoloxamersIbuprofen they are not Do not ingest, avoideyes, skin, and skin/eyetract contact, wear glovesswallowed. Eye protection.eye irritation. Wear lab coat andrespirator gloves.Wash face, hands andof damagingany exposed skinthe unborn child.thoroughly afterhandling.Don’t eat, drink orsmoke when usingproduct.Avoid dust formation.(causes inhalation) –Avoid repeated orprolonged breathing ofspray mist or dust.Declaration – I have read and understood the contents of the safety information sheetand the script for the experimentSigned (student): .. ..~~:~:……………Checked (demonstrator): —~ ·-·························33EXPERIMENT 4SOLID LIPID NANOPARTICLESLEARNING AIMSTo gam. farru·1·1ari·tYw1·th preparation and characterisation of Solid LiquidNanoparticlesDIRECTED READINGS Kristl J Preparation and evaluation of nanosuspensions for~::::~:~ ::u:s~::t~:n ~f poorl; soluble drugs. Int J Pharm. 312 (2006) 179-86.Mehnert W, Mader K. Solid lipid nanoparticles Production, characterization andapplications, Adv Drug Deliv Rev. 47 (2001) 165-196Shah, R.; Eldridge, D.; Palombo, E.; Harding, I., Lipid Nanoparticles: Production,Characterization and Stability. 2015.Muller R.H, Mader K, Gohla S. Solid lipid nanoparticles (SLN) for controlled drugdelivery: a review of the state of the art. Eur J Pharm Biopharm. 50 (2000) 161 – 177Harms, M.; Muller-Goymann, C. C., Solid lipid nanoparticles for drug delivery.Journal ofDrug Delivery Science and Technology. 21(1) (2011) 89-99.Muller R.H, Mehnert W, Lucks J.S, Schwarz C, zur Muhlen A, Weyhers H, Freitas C,Ruhl D. Solid lipid micronanoparticles (SLN) – An alternative colloidal carriersystem for controlled drug delivery. Eur J Pharm Biopharm. 41 (1995) 62-69Schwarz, C., Solid lipid nanoparticles (SLN) for controlled drug delivery II. drugincorporation and physicochemical characterization. Journal of Microencapsulation.16(2) (1999) 205-213.INTRODUCTIONSolid Lipid Nanoparticles (SLN) are particles made from solid lipids (i.e. lipids solidat room temperature and also at body temperature) and stabilised by surfactant(s). Bydefinition, the lipids can be highly purified triglycerides, complex glyceride mixturesor even waxes. Recently, SLN based on para-acyl-calixarenes have been prepared andstudied. Through the work of various research groups, the carrier system SLN hasbeen characterised intensively. For detailed information on production,characterisation and application, the reader is referred to the main review papers up todate. Typical atomic force microscopy (AFM) image of SLNs is presented in Figure1.34(o) 101.e- !blf/10.0Figure 1. Typical atomic force microscopy (AFM) image of SLNsSurfactants40,D””‘32&.8″”‘In contrast to emulsions for parenteral nutrition which are normally stabilized bylecithin, the SLN can be stabilized by other surfactants or polymers and theirmixtures. However, as a distinct advantage of SLN compared to polymericnanoparticles they can be produced by high pressure homogenization identical toparenteral 0/W emulsions. This is a technique well established on the large scale andalready available in the pharmaceutical industry. The production lines for parenteralemulsions are in most cases equipped with temperature control units because anincreased temperature facilitates emulsion production, this means that existingproduction lines can be used for producing SLN by the hot homogenization technique.Surfactants and co-surfactants include lecithin, bile salts, but also alcohols such asbutanol. Excipients such as butanol are less favourable with respect to regulatoryaspects. From the technical point of view precipitation of the lipid particles in water isa dilution of the system, that leads to a reduction of solid content of the SLNdispersion. For some technological operations it is highly desirable to have a highlipid solid content, e.g., 30%. An example is the transfer of the SLN dispersion to adry product (e.g., tablet, pellet) by a granulation process. The SLN dispersion can beused as granulation liquid, but in the case of low particle content too much waterneeds to be removed.Surfactants are compounds with two distinct regions in their chemical structure. Oneregion has hydrophilic properties, the other having hydrophobic properties (Figu~e 2).The hydrophilic properties are usually conferred on molecule by the presence of 10n_s,alcohol or carboxyl groups. Hydrophobic properties are due to long chamhydrocarbons which may also have a ring system attached to them.35~-hydrophilicheadhydrophobic · tOI·1Figure 2. Typical structure of a surfactantb d fi dSurfactants can e e me m. to one of two categories·’ either ionic . . or non-ionic . .(F1gure . 3). The 1omc . . group can’ also be sub-divided into catiomc, amomc orzwitterionic (amphoteric) groups.hydrophobe hydrophilelAnionic (phosphates, sulfonatessulfates…)Cationic (quatemary ammonium)lAmphoteric (betaines)Nonionic(Elhoxylates)Figure 3: Different type of surfactantsStability of SLNsThe measurement of the zeta potential allows predictions about the storage stability ofcolloidal dispersion. In general, particle aggregation is less likely to occur for chargedparticles (high zeta potential) due to electric repulsion. However, this rule cannotstrictly apply for systems which contain steric stabilizers because the adsorption of thesteric stabilizer will decrease the zeta potential, due to the shift in the shear plane ofthe particle. The physical stability of SLN dispersions can be investigated intensively,e.g., by measurements of particle size (photon correlation spectroscopy, PCS; laserdiffraction, LD), charge (ZP) and thermal analysis (differential scanning calorimetry,DSC).36LMETHODFormulations by HPI.1/Ultrasonication method~Students will be d1v1ded m two groups and they will swap mid-experiment to useeither HPH or ultrasonication to prepare SLNs.The SLN samples loaded wit? IBU as the model pharmacological active ingredientwill be prepared by the followmg methods:Prepare 50 ml of hot water in a tall-form 100 ml beaker by heating the wateron a hot plate, do not add a magnetic stirrer bar. . lJ~o ·• l g of the SLN ~ompone~ts (IBU/tristearilpoloxamer 407) at a ratio of) .1 y–i0/20/70 (w/w/~) 1s pl~ced ma se~a~ate container and heated to a temperature.i/o·l.- Oabove the meltmg yomt ?f the hp1d (above 70°C) allowing the IBU andpoloxamer 407 to dissolve m the molten lipid.0 • The drug-containing melt lipid is then dispersed in distilled hot water (50ml).This is done by, adding, with aid.of a syringe, the melted SLN components tothe bottom of the beaker of hot water while mixing the water with ahomogeniser, keep the beaker of water on a hot plate at all times. This processhas to be carried out quickly to avoid crystallisation.The sample needs to be homogenised (15,000 rpm) with an Ultra Turrax K25homogenizer to form a pre-emulsion for 3 min. The homogenizer needs to beobserved, as the solution can sometimes overflow from the beaker. A whitemilky solution will be produced.• The same process will be repeated but this time the IBU/lipid components willbe dissolved in 2 ml Et-OH while SLN components will be dissolved in hotdistilled water. (Students will swap to conduct this part of the work i.e., HPHgroup will perform this step using ultrasonic horn and vice versa.)Particle size measurements and zeta potentialThe particle size distribution and the zeta potential of the produced preparations willbe determined by dynamic light scattering (PCS) using a Malvern Zetasizer Nano-ZS.The determined particle size range is 0.6 nm – 6 µm.QUESTIONS• What are advantages of the SLNs compared to other drug delivery systems?• Which preparation SLN method is most suitable for the formulation of IBUnanosuspensions and why?• What is the effect of different surfactants on the obtained SLN particle sizewith the following characteristics: a) Higher surfactant amounts and b)surfactants with longer lipid chains? .• Can SLNs be used for the development of sustained release formulations andhow?37
