Poloxamer 338

Polycaprolactone (PCL) with an average molecular weight (M_w) of 80 kDa, was purchased from Huaian Ruanke Trade Co., Ltd. (Huaian City, China). Poloxamer 188 (P188) and poloxamer 338 (P338) were kindly supplied by BASF (Florham Park, NJ, USA). Ibuprofen (IBP) (98% purity) was purchased from Ark Pharm Inc. (Arlington Height, IL, USA). Hexafluoro-2-propanol (HFIP) was purchased from Richest Group Ltd. (Shanghai, China). Phosphate-buffered saline (PBS) buffer solution (pH ~7.4) was purchased from Avantor (Radnor, PA, USA). All the other chemicals were of reagent grade and used as received without further purification.

PB CD34⁺ samples were obtained from healthy donors from plerixafor and G-CSF mobilization. Cells were thawed and plated at 1 × 10⁶ cells/mL on non-tissue culture-treated 96-well plates pre-coated with retronectin (20 μg/mL; Takara Shuzo). Cells were pre-stimulated for 24 h in X-Vivo 15 medium (Lonza) supplemented with 1× glutamine, penicillin, and streptomycin (Gemini Bio-Products), human Flt-3 ligand (50 ng/mL), human SCF (50 ng/mL), human TPO (50 ng/mL), and human IL-3 (20 ng/mL) (cytokines: PeproTech). CD34⁺ cells were transduced with concentrated viral supernatants at transduction concentrations of 2 × 10⁵ TU/mL, 6 × 10⁵ TU/mL, 2 × 10⁶ TU/mL, and 6 × 10⁶ TU/mL with transduction enhancer Poloxamer 338 (1 mg/mL) (BASF, Ludwigshafen, Germany). At 24 h after transduction, cells were washed and plated under myeloid culture conditions. Cells were cultured for 2 weeks after transduction in basal bone marrow media consisting of Iscove-modified Dulbecco’s medium (Lonza) 1× glutamine, penicillin, and streptomycin (Gemini Bio-Products), 20% fetal bovine serum, and 0.52% BSA (Sigma-Aldrich) supplemented with human SCF (25 ng/mL), human IL-3 (5 ng/mL), and human IL-6 (10 ng/mL).