Development of Biomimetic PHB and PHBV Scaffolds for a Three Dimensional (3-D) In Vitro Human Leukaemia Model
Creators: name: Zubairi, Saiful Irwan
Publisher: name: Imperial College London
Year: 2013

description: Leukaemia is defined as a group of haematological diseases (related to blood and blood-forming tissue) characterized by malignant proliferation of myeloblasts or lymphoblasts that replace normal bone marrow elements and infiltrate normal tissues. The study of leukaemia has been hindered by the lack of appropriate in vitro models, which can mimic this microenvironment. It is hypothesized that the fabrication of porous 3-D scaffolds for the biomimetic growth of leukaemic cells in vitro could facilitate the study of the disease in its simulated native 3-D niche. In this study, polyhydroxyalkanoate (PHA), in particular poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate-co-valerate) (PHBV) porous 3-D scaffolds with an improved thickness (in relative to the conventionally made PHA matrices) are utilized and investigated to model the abnormal 3-D leukaemic cellular growth system in the absence of exogenous cytokines. The polymeric porous 3-D scaffolds were fabricated using an ideal polymer concentration of 4% (w/v). The salt-leaching efficacy and the effect of salt residual on the cell growth media were carried out to validate the significant amount of salt remnant inside the porous materials. The physico-chemical characteristics of the porous 3-D scaffolds such as surface wetting, porosity, BET surface area and pore size distribution were studied by means of drop sessile analyzer (DSA), helium gas pycnometry, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). To increase probability of cellular attachment and proliferation, the polymeric scaffold surfaces were treated with O2-rf-plasma (100 W at 10 min) and NaOH (0.6M). Next, in order to improve the in vitro 3-D leukaemic cell culture, two main bone marrow extracellular matrix (ECM) proteins which are collagen type I or fibronectin were immobilized via physical adsorption on the treated surfaces of the polymeric porous 3-D scaffolds. Meanwhile, the in vitro degradation studies were conducted on both polymeric scaffolds with the hydrolytic degradation media of phosphate buffered saline (PBS) and cell growth media. The scaffolds were analyzed and compared for mass loss, morphology and pH changed of the PBS and cell growth media throughout 45 weeks and 9 weeks of the study respectively. Overall, PHB and PHBV displayed a good seeding efficiency (24 h) and excellent leukaemic cellular growth for up to 6 weeks (protein-coated scaffolds), assessed by MTS assay and SEM. Once the abnormal hematopoietic 3-D model (cell lines) was established, a new model to culture human primary acute myeloid leukaemia mononuclear cells (AML MNCs) was studied, compared and validated. All leukaemic cells grew better in PHBV scaffolds coated with 62.5 μg/ml collagen type I and sustained cell growth in the absence of exogenous cytokines. As a result, it was concluded that PHBV-collagen scaffolds may provide and could be used, as a practical model with which to study the biology and treatment of primary AML in an in vitro mimicry without the use of 2-D culture system and animal models.