PARTICLESIZE and ShapeThe drug delivery of nano transdermal products areaffected by particle size, shape whichfurther determine physical steadiness and cellular uptake of nano drugs(Escobar Chavez et al 2012).
Nanoformulations can be delivered concurrentlyusing different means/routes owing to their particle size and physicochemicalproperties (Borali 2010). Skin anatomical features only allows freedistribution of the particles <5-7 nm size using transcellular route (Bouwstra and Ponec 2006,Johnson et al 1997), ?36 nm using intercellulat route (Cevc 2004, tang et al. 2001) and > 3-10µm through transfollicular route. Particles having smaller size are preferredsince they provide larger surface area and have higher drug incorporation capacity.Attama et al (2007) reported that solid lipid nanodispersions (SLN) having low particle size are more stable and well tolerated in vivo andincorporate high drug concentration in active formulations (AttamaAA, Schicke BC, Paepenmüller T, Müller-Goymann CC (2007) Solid lipidnanodispersions containing mixed lipid core and a polar heterolipid:Characterization. Eur. J. Pharm.
Biopharm. 67: 48-57). Similar conclusions were made by Maestrelli et al(2009), who investigated ethosomes prepared by different techniques, and foundthat small unilamellar vesicles (SUVs) drug efficacy of benzocaine (BZC) was higher probably due to its small sizeand higher surface area which allowedmore intimate contact with the epithelium and gave drug more time for therapeuticaction (MaestrelliF, Capasso G, Gonzalez-Rodriguez ML, et al., (2009) Effect ofpreparation technique on the properties and in vivo efficacy ofbenzocaine-loaded ethosomes. J Liposome Res 19(4): 253-60). Desai et al.(2010) and Baroli (2010) concluded that nanoparticles lipophilic in naturehaving high partition coefficient and molecular weight <600 Da are bestsuited for TDDS.
Nanoparticles can form different shapes like spherical,ellipsoidal, triangular, needle shaped, cubic and prism like. They are notalways rigid (e.g. lipid particles) and deformable and their shape andorientation greatly influence their aggregation, the choice of penetrationroute and diffusion coefficient (Baroli 2010). Using newer methodsnanoparticles of preferred size and shape for TDDS can be engineered. ZETA POTENTIALZetapotential is the number of charges a particle carries. It is important todetermine the particle size distribution and zeta potential of nanoformulationsbecause it determines the dispersion stabilityof the non-aqueous suspension Attama AA, Schicke BC, Paepenmüller T,Müller-Goymann CC (2007) Solid lipid nanodispersions containing mixed lipidcore and a polar heterolipid: Characterization. Eur.
J. Pharm. Biopharm. 67:48-57.SIZE DISTRIBUTION The sizedistribution of particles formed by different systems are mostly affected bypreparation methods and conditions like temperature, dispersing medium,stirring rate and viscosity of the organic and aqueous phases PintoReis C, Nuefeld RJ, Ribeiro AJ, et al., (2006) Nanoencapsulation 1.
Methods for preparation of drug-loaded polymeric nanoparticles. Nanomedicine.2: 8-21, Maestrelli F, Capasso G,Gonzalez-Rodriguez ML, et al., (2009) Effect of preparationtechnique on the properties and in vivo efficacy of benzocaine-loadedethosomes. J Liposome Res 19(4): 253-60.