▁particle ▁transfer ▁has ▁prompt ed ▁develop ments ▁in ▁nan om edic ine ▁and ▁bi ology ▁to ▁increase ▁skin ▁per me ability . ▁One ▁application ▁of ▁trans cut aneous ▁particle ▁delivery ▁could ▁be ▁to ▁locate ▁and ▁treat ▁cancer . ▁Nan omed ical ▁research ers ▁seek ▁to ▁target ▁the ▁e pid erm is ▁and ▁other ▁layers ▁of ▁active ▁cell ▁division ▁where ▁nan op articles ▁can ▁interact ▁directly ▁with ▁cells ▁that ▁have ▁lost ▁their ▁growth - control ▁mechan isms ▁( can cer ▁cells ). ▁Such ▁direct ▁interaction ▁could ▁be ▁used ▁to ▁more ▁accur ately ▁diagn ose ▁properties ▁of ▁specific ▁tum ors ▁or ▁to ▁treat ▁them ▁by ▁deliver ing ▁dru gs ▁with ▁cell ular ▁specific ity . ▁ ▁Nan op articles ▁ ▁Nan op articles ▁ 4 0   nm ▁in ▁diameter ▁and ▁smaller ▁have ▁been ▁successful ▁in ▁pen etr ating ▁the ▁skin . ▁Research ▁confir ms ▁that ▁nan op articles ▁larger ▁than ▁ 4 0   nm ▁do ▁not ▁pen et rate ▁the ▁skin ▁past ▁the ▁str atum ▁cor neum . ▁Most ▁particles ▁that ▁do ▁pen et rate ▁will ▁diff use ▁through ▁skin ▁cells , ▁but ▁some ▁will ▁travel ▁down ▁hair ▁fol lic les ▁and ▁reach ▁the ▁der mis ▁layer . ▁ ▁The ▁per me ability ▁of ▁skin ▁relative ▁to ▁different ▁shapes ▁of ▁nan op articles ▁has ▁also ▁been ▁studied . ▁Research ▁has ▁shown ▁that ▁spher ical ▁particles ▁have ▁a ▁better ▁ability ▁to ▁pen et rate ▁the ▁skin ▁compared ▁to ▁ob long ▁( elli ps oid al ) ▁particles ▁because ▁spher es ▁are ▁symmetric ▁in ▁all