MC3T3 E1 cell response to mineralized nanofiber shish kebab structures

Abstract

Block copolymers (BCPs) are of growing interest because of their extensive utility in tissue engineering, particularly in biomimetic approaches where multifunctionality is critical. We synthesized polycaprolactone‐polyacrylic acid (PCL‐b‐PAA) BCP and crystallized it onto PCL nanofibers, making BCP nanofiber shish kebab (BCP NFSK) structures. When mineralized in 2× simulated body fluid, BCP NFSK mimic the structure of mineralized collagen fibrils. We hypothesized that the addition of a calcium phosphate layer of graded roughness on the nano‐structure of the nanofiber shish kebabs would enhance preosteoblast alkaline phosphatase (ALP) activity, which has been shown to be a critical component in bone matrix formation. The objectives in the study were to investigate the effect of mineralization on cell proliferation and ALP activity, and to also investigate the effect of BCP NFSK periodicity, a structural feature describing the distance between PCL‐b‐PAA crystals on the nanofiber core, on cell proliferation, and ALP activity. ALP activity of cells cultured on the mineralized BCP NFSK template was significantly higher than the nonmineralized BCP NFSK templates. Interestingly, no statistical difference was observed in ALP activity when the periodic varied, indicating that surface chemistry seemed to play a larger role than the surface roughness.

Insight on the Role of Poly(acrylic acid) for Directing Calcium Phosphate Mineralization of Synthetic Polymer Bone Scaffolds

“…Both unmineralized and mineralized NSFK mats have demonstrated excellent potential applications in bone tissue engineering. 39,40,44,45 Previously, NFSKs with PCL shish and PCL-b-PAA kebabs (NFSK PCL/PCL-b-PAA ) have been mineralized in 2× concentrated simulated body fluid (2SBF) and a three-stage mineral growth mechanism was proposed: ions enter kebabs and form amorphous calcium phosphate (ACP) over the first 3 days (stage 1), followed by intra-kebab transformation of ACP to carbonated apatite from 3 to 5 days (stage 2), and finally overgrowth of crystalline mineral to the extra-kebab space (stage 3). 38 In the current study, NFSK PCL/PCL-b-PAA are used as the model scaffold, and "free" PAA dissolved in the mineralization solution is introduced as a PILP-forming additive to mimic the effect of NCPs on the mineralization process.…”

“…In particular, when a block copolymer such as poly­(caprolactone)- b -PAA (PCL- b -PAA) containing an ionic block (PAA) is used as the kebab-forming material, controlled polymer crystallization and block copolymer phase separation lead to the formation of sub-10 nm ionic domains that recruit mineral ions for confined mineralization. , NFSKs have demonstrated great utility in controlling both mineral spatial distribution and crystalline orientation, which are the two key characteristics in collagen-mediated biomineralization. Both unmineralized and mineralized NSFK mats have demonstrated excellent potential applications in bone tissue engineering. ,,, …”