The nanodrugs transdermal delivery is affected by its size and shape which further decide physical steadinessand their cellular uptake (Escobar Chavez et al 2012). Nanoformulations can bedelivered concurrently using different means/routes owing to their particlesize and physicochemical properties (Borali 2010). Skin anatomical featuresonly allows free distribution of particles <5-7 nm size throughtranscellular route (Bouwstra and Ponec 2006, Johnson et al 1997), ?36 nm forintercellulat route (Cevc 2004, tang etal. 2001) and > 3-10 µm for transfollicular route. Particles of smaller sizeare preferred since they make available larger surface area hence can have highdrug loading capacity.
Attama et al (2007) reported that low particle size solid lipid nanodispersions (SLN) are more stable and well accepted in vivo and activeformulkation had high drug concentration . Maestrelli et al (2009), who investigated ethosomesprepared by different techniques made similar conclusions and found that smallunilamellar vesicles (SUVs) drug efficacy of benzocaine (BZC) was owing to itssmall size, higher surface area which led to more intimate contact with theepithelium for longer duration of time for therapeutic action. Desai et al.(2010) and Baroli (2010) concluded that lipophilic nanoparticles have highpartition coefficient and drugs having molecular weight <600 Da are bestsuited for TDDS. Nanoparticles come in different shapes like spherical,ellipsoidal, triangular, needle shaped, cubic and prism like. They are notalways rigid (e.g. lipid particles) and deformable.
The shape as well asorientation of the nanoparticles greatly affects their aggregation, penetrationroute and diffusion coefficient (Baroli 2010). Using newer methods of nanomaterialsynthesis, nanoparticles of preferred size and shape for TDDS can beengineered. ZETA POTENTIALZetapotential is defines as the number of charges a particle has and particle size distributionand zeta potential of nanoformulations decidesthe dispersion steadiness of the non-aqueous suspension.SIZE DISTRIBUTION Preparationmethods and synthesis conditions (like temperature, dispersing medium, stirringrate and viscosity of the organic and aqueous phases) affect the sizedistribution of nanoparticles formed by different systems.