Hypothesis: Since naturally hydrophobic surface of polystyrene (PS) substrate is unsuitable for cell adhesion, grafting hydrophilic and biocompatible poly(2-hydroxyethyl methacrylate) (PHEMA) chains through surface-initiated atom transfer radical polymerization (SI-ATRP) can alter the surface properties and enhance the cell behavior 
Methods: Hydroxyl functional groups were introduced through ultraviolet/ozone (UVO) irradiation at a distance of 3 cm. Next, an initiator layer was deposited on the surface, which facilitated PHEMA grafting via SI-ATRP, conducted across various polymerization durations (2, 4, and 6 h) 
Findings: The intensity of carbonyl and hydroxyl peaks in ATR-FTIR spectra increased with increasing UVO irradiation time up to 15 min, where water contact angle (WCA) was about 12°. WCA of PHEMA-modified surface decreased from 56 to 48° as polymerization time increased from 2 to 6 h, and the peaks related to hydroxyl and carbonyl groups in ATR-FTIR analysis became stronger. A thin and relatively uniform PHEMA layer with a thickness of about 90-110 nm was observed for the PS substrate pretreated for 15 min and subsequently polymerized with HEMA for 6 h NIH3T3 cell viability on PHEMA-modified surfaces at polymerization times of 2, 4 and 6 h, with a pretreatment for 15 min, was 300, 250 and 225%, respectively. The cell-covered area percentages of the pristine and the PHEMA-modified PS surfaces at polymerization times of 2 and 6 h were 27%, 75%, and 62%, respectively. Most cells on the virgin PS surface exhibited a flat morphology, while a smaller subset displayed a spindle-shaped form. On the modified surfaces, the cells had a spherical shape differed from the natural shape of fibroblast cells. However, cell alignment on the modified surfaces was different from the natural alignment of cells on tissue culture PS dishes, being elongated and spindle-shaped.