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Fig. S1. Absorbance spectra of BSA, sulfo-SANPAH (SS), and BSA conjugated to SS (BSA-SS) were used to confirm (A) the NHS ester reaction conditions, (B) exposure duration for loss of azide peak, and (C) conjugation to TCPS. A: BSA was reacted with 50 molar excess of sulfo-SANPAH for 5 h and dialyzed against water. The resulting product (BSA-SS) had the azide peak found in pure SS and also had a slight increase in absorbance around 300 nm due to BSA. B: Exposure of BSA-SS in water to ultraviolet light attenuated the azide absorbance peak in a time-dependent manner. Five minutes of exposure was used for all subsequent experiments. C: BSA-SS was dried on a surface and exposed to UV light. The disappearance of the azide peak confirmed the success of the photocrosslinking step for conjugating BSA to a surface.

Fig. S2. Most adsorbed VEGF can be removed in acidic conditions. A solution of VEGF was dried onto TCPS surfaces overnight in a 40°C oven and was either stored dry for 2 days or incubated in acidic solution for 2 days. A: Surfaces were evaluated with an ELISA to determine the amount of correctly folded VEGF proteins remaining on the surface. B: To confirm that VEGF was removed and not just denatured by acidic conditions, a BCA assay was used to assess total protein content after treatment. (*) Indicates that after treatment, surfaces were significantly different (P < 0.05) as determined by a t-test. Error bars indicate 1 SD.

Fig. S3. Surface-bound VEGF did not affect the expression of endothelial proteins or ac-LDL uptake. Expression of endothelial proteins (A) VE-Cadherin, (B) VEGF R2, (C) vWF, (D) the venous marker EphB4, and (E) the arterial marker Eprhin-B1, as well as internalization of (F) DiI-ac-LDL were quantified using populations (n = 3) of at least 100 cells. MSCs (stripes) were differentiated on TCPS (white), TCPS with surface-bound VEGF (gray, defined as s-X where X denotes the surface density in ng VEGF/cm2), or TCPS with 50 or 100 ng/mL soluble VEGF (black, labeled 50 VEGF and 100 VEGF, respectively). Letters indicate statistically similar groups as determined from Tukey's post hoc analysis (P > 0.05) of a two-way ANOVA. (*) Represent groups statistically different from proliferating MSCs (stripes) as determined from Dunnett's post hoc analysis (P < 0.05) of a one-way ANOVA. Error bars indicate 1 SD. The data for the control, or comparison, groups (MSCs, none, 50 VEGF, and 100 VEGF) were previously published by Galas and Liu [2013].

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