Evaluation of alkaline pre-treatment of PLLA fibers for biomimetic hydroxyapatite coating

A poly(l-lactic acid) (PLLA) and hydroxyapatite (HA) composite was formed via a biomimetic coating process. Before treatment in a modified-simulated body fluid (m-SBF), the surfaces of the PLLA fibers were etched with alkaline reagents to make the polymer surface easier for apatite to nucleate and grow. Several elements of this etching procedure (including the etching reagent, concentration, and length of pre-treatment) were varied to determine the optimal combination for producing a predictable HA coating with the desired properties of consistent coating distribution and thickness. The alkaline etching reagents used in this study were sodium hydroxide (NaOH), sodium hypochlorite (NaOCl), calcium hydroxide (Ca(OH)2), and calcium hypochlorite (Ca(OCl)2). The weight gained through m-SBF coating, changes in the mechanical properties of the PLLA, and HA coating morphology were observed to determine the effects of different pre-treatment strategies on the biomimetic coating process. It was confirmed that the most effective etching reagents are Ca(OH)2 and Ca(OCl)2. It was also found that decreased etching reagent concentration leads to a decrease in HA coating and increased etching time increases HA deposition.