Santangelo, the tournament's defending champion, was a 6-2, 7-6 (7-4) winner over Shengnan Sun in her first match and moves up the bracket to face Akgul Amanmuradova.
Mirza needed three sets before topping Martina Sucha, 6-4, 4-6, 6-3, and will meet Tatiana Poutchek in the next round.
Third-seeded Vasilisa Bardina was routed 6-1, 6-1 by Tzipora Obziler in a second-round match but No. 4 Kostanic Tosic was a 6-4, 6-1 winner over Dominika Cibulkova. In other second-round matches Wednesday, Yaroslava Shvedova ousted seventh-seeded Tamarine Tanasugarn, 6-4, 3-6, 6-4 and Yurika Sema overcame Yulia Beygelzimer, 1-6, 6-4, 6-1.