Figure 3: A biocompatible surface coating minimized foreign body reaction and prevents device failure in C57BL/6 mice.

a) Schematic of the chemistry scheme used to modify device surface with biocompatible polymers. Surface initiated ARGET-ATRP was used to grow polymer brushes of four different monomers - carboxybetaine methacrylate (CBMA), sulfobetaine methacrylate (SBMA), methacryloyloxylethyl phosphorylcholine (MPC) and tetrahydropyran phenyl triazole (THPT), the structures of which are shown.

b) Serum concentration of EPO in C57BL/6 mice, 28 d after i.p. transplantation with surface-modified(coated) devices encapsulating HEKepo cells (1×10⁶ per device). Uncoated devices with or without cells (empty) were used for comparison. The THPT-coated devices showed the highest increase in serum EPO compared to the other coatings. Error bar: mean ± s.e.m, Group size (animals) n = 7 (SBMA), 9 (MPC), and 10 (empty, uncoated and THPT) represents combined data from two independent experiments. Statistical analysis: one-way ANOVA with Bonferroni multiple comparison correction. P values are shown for comparison with empty devices.

c) Collagen deposition on retrieved devices quantified by hydroxyproline assay of proteins extracted from the device surface, showing lowest hydroxyproline deposition on THPT-coated devices. Error bar: mean ± s.e.m (n = 5 animals). Statistical analysis: one-way ANOVA with Bonferroni multiple comparison correction. P values are shown for comparison with THPT group.

d) Representative images of the retrieved devices. Bright-field images of intact devices (top panel) along with histological sections of the device mebranes (lower panel, masson’s trichrome) shows minimal fibrosis on the THPT coated devices. Scale bar: 5 mm (BF), 100μm (MT). Experiments were repeated twice with similar results.

e) Nanostring-based analysis for expression of phenotypic markers in cells attached to the device surface 28d post-transplant. Values are normalized to uncoated devices and presented on a base 2 logarithm scale (n = 5 animals per group).

f) Relative proteomic analysis of the protein lysates extracted from retrieved devices, showing levels of major proteins of the extracellular matrix. Values are expressed as fold change over uncoated devices.