title: Functional nanofiber scaffolds with different spacers modulate adhesion and expansion of cryopreserved umbilical cord blood hematopoietic stem/progenitor cells.
abstract: OBJECTIVE
  Nanofiber scaffolds with amino groups conjugated to fiber surface through different spacers (ethylene, butylenes, and hexylene groups, respectively) were prepared and the effect of spacer length on adhesion and expansion of umbilical cord blood hematopoietic stem/ progenitor cells (HSPCs) was investigated.
  
  
  METHODS
  Electrospun polymer nanofiber scaffolds were functionalized with poly(acrylic acid) grafting, followed by conjugation of amino groups with different spacers. HSPCs were expanded on aminated scaffolds for 10 days. Cell proliferation, surface marker expression, clonogenic potential, and nonobese diabetic (NOD)/severe combined immunodeficient (SCID) repopulation potential of the expanded cells were evaluated following expansion culture.
  
  
  RESULTS
  Aminated nanofiber scaffolds with ethylene and butylene spacers showed high-expansion efficiencies (773- and 805-fold expansion of total cells, 200- and 235-fold expansion of CD34+CD45' cells, respectively). HSPC proliferation on aminated scaffold with hexylene spacer was significantly lower (210-fold expansion of total cells and 86-fold expansion of CD34+CD45+ cells), but maintained the highest CD34+CD45+ cell fraction (41.1%). Colony-forming unit granulocyte-erythrocyte-monocyte-megakaryocyte and long-term culture-initiating cell maintenance was similar for HSPCs expanded on all three aminated nanofiber scaffolds; nevertheless, the NOD/SCID mice engraftment potential of HSPCs expanded on aminoethyl and aminobutyl conjugated nanofibers was significantly higher than that on aminohexyl conjugated nanofibers.
  
  
  CONCLUSIONS
  This study demonstrated that aminated nanofibers are superior substrates for ex vivo HSPC expansion, which was correlated with the enhanced HSPC adhesion to these aminated nanofibers. The spacer, through which amino groups were conjugated to nanofiber surface, affected the expansion outcome. Our results highlighted the importance of scaffold topography and cell-substrate interaction to regulating HSPC proliferation and self-renewal in cytokine-supplemented expansion.
authors.affiliation: Division of Bioengineering, National University of Singapore Nanoscience and Nanotechnology Initiative, Singapore.
authors.forename: Kian-Ngiap
authors.initials: KN
authors.lastname: Chua
authors.forename: Chou
authors.initials: C
authors.lastname: Chai
authors.forename: Peng-Chou
authors.initials: PC
authors.lastname: Lee
authors.forename: Seeram
authors.initials: S
authors.lastname: Ramakrishna
authors.forename: Kam W
authors.initials: KW
authors.lastname: Leong
authors.forename: Hai-Quan
authors.initials: HQ
authors.lastname: Mao
mesh_terms: D000588:Amines / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D002448:Cell Adhesion / Q000187:drug effects; D018929:Cell Culture Techniques / Q000379:methods; D049109:Cell Proliferation / Q000187:drug effects; D002999:Clone Cells; D015925:Cryopreservation; D004563:Electrochemistry / Q000379:methods; D006085:Graft Survival; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D011108:Polymers / Q000737:chemistry / Q000494:pharmacology*; D013499:Surface Properties; D014183:Transplantation, Heterologous
chemical_list: D000588:Amines; D001672:Biocompatible Materials; D011108:Polymers