. ▁In ▁contrast , ▁low ▁to ▁medium ▁por os ity ▁mic rop orous ▁layers ▁displayed ▁more ▁stable ▁configurations ▁and ▁induced ▁hydro xy apat ite ▁growth . ▁ ▁Bio active ▁ ▁The ▁first ▁sign ▁of ▁por ous ▁sil icon ▁as ▁a ▁bio active ▁material ▁was ▁found ▁in ▁ 1 9 9 5 . ▁In ▁the ▁conducted ▁study , ▁it ▁was ▁found ▁that ▁hydro xy apat ite ▁growth ▁was ▁occurr ing ▁on ▁por ous ▁sil icon ▁areas . ▁It ▁was ▁then ▁suggested ▁that ▁" h yd r ated ▁mic rop orous ▁Si ▁could ▁be ▁a ▁bio active ▁form ▁of ▁the ▁sem icon duct or ▁and ▁suggest ▁that ▁Si ▁itself ▁should ▁be ▁seriously ▁considered ▁for ▁development ▁as ▁a ▁material ▁for ▁w ides p read ▁in ▁v ivo ▁applications ." ▁Another ▁paper ▁published ▁the ▁finding ▁that ▁por ous ▁sil icon ▁may ▁be ▁used ▁a ▁substr ate ▁for ▁hydro xy apat ite ▁growth ▁either ▁by ▁simple ▁so aking ▁process ▁or ▁las er - liqu id - sol id ▁interaction ▁process . ▁ ▁Since ▁then , ▁in - v it ro ▁studies ▁have ▁been ▁conducted ▁to ▁evaluate ▁the ▁interaction ▁of ▁cells ▁with ▁por ous ▁sil icon . ▁A ▁ 1 9 9 5 ▁study ▁of ▁the ▁interaction ▁of ▁B 5 0 ▁rat ▁hi pp oc amp al ▁cells ▁with ▁por ous ▁sil icon ▁found ▁that ▁B 5 0 ▁cells ▁have ▁clear ▁preference ▁for ▁ad hes ion ▁to ▁por ous ▁sil icon ▁over ▁un tre ated ▁surface . ▁The ▁study ▁indicated ▁that ▁por ous ▁sil icon ▁can ▁be ▁suitable ▁for