title: Comparative in vitro study regarding the biocompatibility of titanium-base composites infiltrated with hydroxyapatite or silicatitanate.
abstract: BACKGROUND
  The development of novel biomaterials able to control cell activities and direct their fate is warranted for engineering functional bone tissues. Adding bioactive materials can improve new bone formation and better osseointegration. Three types of titanium (Ti) implants were tested for in vitro biocompatibility in this comparative study: Ti6Al7Nb implants with 25% total porosity used as controls, implants infiltrated using a sol-gel method with hydroxyapatite (Ti HA) and silicatitanate (Ti SiO2). The behavior of human osteoblasts was observed in terms of adhesion, cell growth and differentiation.
  
  
  RESULTS
  The two coating methods have provided different morphological and chemical properties (SEM and EDX analysis). Cell attachment in the first hour was slower on the Ti HA scaffolds when compared to Ti SiO2 and porous uncoated Ti implants. The Alamar blue test and the assessment of total protein content uncovered a peak of metabolic activity at day 8-9 with an advantage for Ti SiO2 implants. Osteoblast differentiation and de novo mineralization, evaluated by osteopontin (OP) expression (ELISA and immnocytochemistry), alkaline phosphatase (ALP) activity, calcium deposition (alizarin red), collagen synthesis (SIRCOL test and immnocytochemical staining) and osteocalcin (OC) expression, highlighted the higher osteoconductive ability of Ti HA implants. Higher soluble collagen levels were found for cells cultured in simple osteogenic differentiation medium on control Ti and Ti SiO2 implants. Osteocalcin (OC), a marker of terminal osteoblastic differentiation, was most strongly expressed in osteoblasts cultivated on Ti SiO2 implants.
  
  
  CONCLUSIONS
  The behavior of osteoblasts depends on the type of implant and culture conditions. Ti SiO2 scaffolds sustain osteoblast adhesion and promote differentiation with increased collagen and non-collagenic proteins (OP and OC) production. Ti HA implants have a lower ability to induce cell adhesion and proliferation but an increased capacity to induce early mineralization. Addition of growth factors BMP-2 and TGFβ1 in differentiation medium did not improve the mineralization process. Both types of infiltrates have their advantages and limitations, which can be exploited depending on local conditions of bone lesions that have to be repaired. These limitations can also be offset through methods of functionalization with biomolecules involved in osteogenesis.
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania ; University of Medicine and Pharmacy "Iuliu Hatieganu" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Ioana-Carmen
authors.initials: IC
authors.lastname: Brie
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Olga
authors.initials: O
authors.lastname: Soritau
authors.affiliation: Technical University, Cluj-Napoca, Romania.
authors.forename: Noemi
authors.initials: N
authors.lastname: Dirzu
authors.affiliation: University of Medicine and Pharmacy "Iuliu Hatieganu" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Cristian
authors.initials: C
authors.lastname: Berce
authors.affiliation: Faculty of Physics & Institute of Interdisciplinary Research in Bio-Nano-Sciences, Babes Bolyai University, 400084 Cluj-Napoca, Romania.
authors.forename: Adriana
authors.initials: A
authors.lastname: Vulpoi
authors.affiliation: Technical University, Cluj-Napoca, Romania.
authors.forename: Catalin
authors.initials: C
authors.lastname: Popa
authors.affiliation: Faculty of Physics & Institute of Interdisciplinary Research in Bio-Nano-Sciences, Babes Bolyai University, 400084 Cluj-Napoca, Romania.
authors.forename: Milica
authors.initials: M
authors.lastname: Todea
authors.affiliation: Faculty of Physics & Institute of Interdisciplinary Research in Bio-Nano-Sciences, Babes Bolyai University, 400084 Cluj-Napoca, Romania.
authors.forename: Simion
authors.initials: S
authors.lastname: Simon
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Maria
authors.initials: M
authors.lastname: Perde-Schrepler
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Piroska
authors.initials: P
authors.lastname: Virag
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Otilia
authors.initials: O
authors.lastname: Barbos
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Chereches
authors.affiliation: Technical University, Cluj-Napoca, Romania.
authors.forename: Petru
authors.initials: P
authors.lastname: Berce
authors.affiliation: The Institute of Oncology "Prof. Dr. I. Chiricuta" Cluj-Napoca, Cluj-Napoca, Romania ; University of Medicine and Pharmacy "Iuliu Hatieganu" Cluj-Napoca, Cluj-Napoca, Romania.
authors.forename: Valentin
authors.initials: V
authors.lastname: Cernea
keywords: Cell adhesion; Differentiation; Hydroxyapatite; Implants; Mineralization; Osteoblasts; Porous titanium; Silicatitanate