Purelab option

TAF (also known as GS-7340) was provided by Gilead Sciences, Inc. TAF and TFV and their stable isotopically labelled (SIL) internal standards (TFV-d6 and TAF-d5) were obtained from Toronto Research Chemicals (Canada). Poly(vinylpyrrolidone) (PVP K29-32; and PVP K90) was provided by Ashland (Kidderminster, UK). Poly(vinyl alcohol) (PVA 9–10 ​kDa) and solvents methanol ≥99.9%, dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) inhibitor-free ≥ 99.9% and acetonitrile (ACN) ​≥ ​99.9% (all HPLC grade), ammonium acetate ≥98%, and Acetic acid ≥99.7% were purchased from Sigma-Aldrich, St. Louis, USA. Two different types of poly(d,l-lactide-co-glycolide) (PLGA) were used, a low viscosity PLGA, Purasorb® PDLG 7502 with a lactide:glycolide ratio of 75:25 and ester end (Purac®, Corbion, Netherlands) (LV-PLGA) and a high viscosity PLGA with a lactide:glycolide ratio of 75:25 and ester end (Viatel® DLG 7503 ​E) (HV-PLGA). Both PLGAs were a donation from Ashland (Kidderminster, UK). All other reagents used in this work were of analytical grade and purchased from Sigma-Aldrich. Elga purified water was used in all cases (Purelab option® Elga LabWater, High Wycombe, UK).

PMEA (M_n = 31 kg/mol, M_w/M_n = 3.33) and poly(butyl acrylate) (PBA) (M_n = 85 kg/mol, M_w/M_n = 1.47) were synthesized by free radical polymerization, as described in a previous report (Tanaka et al., 2000b (link); Sato et al., 2015 (link)). The chemical structure is shown in Supplementary Figure 1. Polymer solutions (0.2% w/v polymer/solvent) were prepared by dissolving PMEA in methanol and PBA in ethanol. Before the film preparation, polyethylene terephthalate (PET) substrates (φ = 14 mm, thickness = 125 μm) were rinsed in ethanol and dried at room temperature for 1 h. Then, the polymer solution (40 μL) was spin-coated twice on PET using a Mikasa Spin Coater MS-A100, as previously reported (Kobayashi et al., 2017 (link)). The static contact angle of the sessile water droplet (purified using PURELAB Option, ELGA Labwater) on the polymer films was measured using a DropMaster DMo-501SA (KYOWA) (Supplementary Table 1). Polymer/PBS interfaces at 37°C were observed using AFM (Cypher, Oxford Inst., Inc.) with an environmental cell. A cantilever of a pyramidal silicon nitride tip, with a spring constant of 0.57 N/m and a resonance frequency of 73 kHz (in air) (TR800PSA, Olympus, Co.), was used.