In vitro cytotoxicity and in vivo foreign body responses of BPLP-co-PLGA. (a) MTT assay (570 nm) against human mesenchymal stem cells (hMSCs) cultured on copolymer films for 24 hours (insert, SEM image of hMSCs cultured for 24 hours on BPLP-co-PLGA 75/25-100 film). (b) Normalized cell viability of hMSCs cultured with the presence of different dilutions of BPLP-co-PLGA degradation products, PLGA 75/25 was used as control. (c) Live/Dead assay images of hMSCs cultured with 10× diluted degradation products of PLGA 75/25 and BPLP-co-PLGA 75/25-100 for 1, 3 and 7 days. (d) Foreign body response evaluations: (1) Representative H&E staining images of surrounding tissues of BPLP-co-PLGA and PLGA copolymer films after 1 month of implantation (P: polymer, C: fibrous capsule, M: muscle); (2) Cell numbers in a 200 × 200 µm2 square region (from 400× images of H & E staining) of the skin-side tissue near the implants.