Effect of silk film functionalization on human megakaryocyte adhesion and proplatelet formation. (A-B) Mk adhesion and proplatelet formation on ECM entrapped within silk film followed a similar trend compared with ECM coated on glass coverslip or coated on silk film (average ± SD, n = 4, P = not significant). (C) Representative α-tubulin staining of Mks cultured on coated glass coverslip, coated silk film, or entrapped silk film. Mks were able to sense the proteins entrapped in silk film as they normally spread on type I collagen and form proplatelet on fibrinogen in all tested conditions (scale bar = 50 µm). (D-E) Analysis of silk film functionalization with bone marrow vascular niche ECM components: fibronectin (FNC), type IV collagen (COL IV), and laminin (LAM). Both Mk adhesion and proplatelet formation were not different between the 3 tested ECM components, but significantly higher compared with the nonfunctionalized silk film control only (average ± SD, n = 3, *P < .05). (F) Representative β1-tubulin staining of Mks cultured for 16 hours on functionalized silk films shows that proplatelet morphology was almost similar between the 3 tested conditions (scale bar = 50 µm).