Abstract
Implant devices containing insulin-secreting β-cells hold great promise for the treatment of diabetes. Using in vitro cell culture, long-term function and viability are enhanced when β-cells are cultured with extracellular matrix (ECM) proteins. Here, our goal is to engineer a favorable environment within implant devices, where ECM proteins are stably immobilized on polymer scaffolds, to better support β-cell adhesion. Four different polymer candidates (low-density polyethylene (LDPE), polystyrene (PS), polyethersulfone (PES) and polysulfone (PSU)) were treated using plasma immersion ion implantation (PIII) to enable the covalent attachment of laminin on their surfaces. Surface characterisation analysis shows the increased hydrophilicity, polar groups and radical density on all polymers after the treatment. Among the four polymers, PIII-treated LDPE has the highest water contact angle and the lowest radical density which correlate well with the non-significant protein binding improvement observed after 2 months of storage. The study found that the radical density created by PIII treatment of aromatic polymers was higher than that created by the treatment of aliphatic polymers. The higher radical density significantly improves laminin attachment to aromatic polymers, making them better substrates for β-cell adhesion.
Highlights
Microencapsulation of insulin secreting β-cells is a promising approach to treating diabetes
We proposed the use of plasma immersion ion implantation (PIII) treatment on polymers to immobilize laminin, a commonly studied extracellular matrices (ECM) for β-cell attachment, proliferation and insulin secretion [3,18]
Ion bombardment from the PIII treatment has been found to induce radical formation within surfaces of polymer structures [10]. Those on the surface are oxidized when exposed to air, resulting in the appearance of polar groups which together with the remaining high energy radicals increase the hydrophilicity of the surfaces [11]
Summary
Microencapsulation of insulin secreting β-cells is a promising approach to treating diabetes. The construction of a microencapsulation device requires that the cells within the implant are protected from immune attack and that it is permeable to glucose and nutrient inflow as well as insulin outflow. The approach we favor is the use of an internal polymer scaffold that is bioactivated with extracellular matrices (ECM) proteins that are recognized by β-cells to cause cell adhesion and trigger a range of beneficial cell responses. To this end, we aim to develop methods of stably immobilizing ECM proteins on candidate polymers
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