Hexamethylene diisocyanate hmdi

Micro cellulose, Avicel, was purchased from Sigma-Aldrich, St. Louis, Missouri, USA, and sulfuric acid (H₂SO₄) was purchased from JUNSEI chemical in Tokyo, Japan. PDEGA for the soft segment of CPPU and hexamethylene diisocyanate (HMDI) for the hard segment of CPPU were obtained from Sigma-Aldrich. Dibutyltin dilaurate (DBDL) for catalysis of urethane reaction was also purchased from Sigma-Aldrich.

Aminopropyl-terminated PDMS (DMS-A31) was purchased from Gelest. Hexamethylene diisocyanate (HMDI, 99%), methanol (99%), 2-amino-4-hydroxy-6-methylpyrimidine (methyl isocytosine, 98%), and silica (SIS6962.0) were purchased from Sigma-Aldrich. Tetrahydrofuran (THF, not stabilised, 99%) was purchased from VWR chemicals. All chemicals were used as received.

l-Lactide (LA, Serva Feinbiochemica) was recrystallized from toluene twice, polyethylene glycol monomethyl ether (mPEG_2k, Sigma-Aldrich) was dried under reduced pressure, and stannous 2-ethylhexanoate (Sn(Oct)₂, ∼95%, Sigma-Aldrich) was dried over molecular sieves. Dicyclohexylcarbodiimide (DCC), 4-(dimethylamino)pyridine (DMAP), ammonium hydroxide, hydrochloric acid (37%), succinic anhydride, p-phenylenediamine, N-phenyl-p-phenylenediamine, and phenyl hydrazine (97%) were all obtained from Sigma-Aldrich and used without further purification; ammonium persulfate, ethanol, and dichloromethane were obtained from VWR. Dimethylformamide (DMF, HPLC, VWR) was dried over CaH₂ and distilled under reduced pressure before use. Methanol (MeOH, HPLC, Fisher Scientific), trichloroacetyl isocyanate (96%, Sigma-Aldrich), 1,6-diphenyl-1,3,5-hexatriene (DPH, 98%, Sigma-Aldrich), chloroform (99%, Fisher Scientific), diethyl ether (99.8%, Sigma-Aldrich), anhydrous tetrahydrofuran (THF, Sigma-Aldrich), and hexamethylene diisocyanate (HMDI, 99%, Sigma-Aldrich) were all used without further purification.

Triol PCL oligomers (Mn = 1160 g mol⁻¹ as determined by ¹H NMR), hexamethylene diisocyanate (HMDI), Span 80, and dibutyltin dilaurate (DBTDL) were obtained from Sigma-Aldrich. All solvents were purchased from Fisher and used as received. Phosphate buffered saline solution (PBS), Dulbecco's modified Eagle's medium (DMEM), fungizone antimycotic (Fz), penicillin (Pen), streptomycin (Strep), and trypsin-EDTA were supplied by Gibco Life Technologies. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium salt), trypan blue, collagenase, and paraformaldehyde (PFA) were purchased from Sigma-Aldrich. Fetal bovine serum (FBS) was obtained from PAN-Biotech GmbH. Human mesenchymal stem cells (hMSCs) were obtained by plastic adhesion from bone marrow samples collected from hematologically normal patients undergoing routine total hip replacement surgery. All samples were obtained, after informed consent, from donors of the “Department of Orthopedic Surgery, Hôpital d'Instruction des Armées Percy” (Clamart, France).

CHO (M_n: 3000 g/moL) was offered by Shandong Hailongyuan Biotechnology Co., Ltd. (Weifang, China), and the degree of deacetylation was about 93.5%. Poly(ε-caprolactone) (PCL, M_n = 2000 g/moL), stannous octoate (Sn(Oct)₂) and hexamethylene diisocyanate (HMDI) were supplied from Sigma-Aldrich (St. Louis, MO USA). Before use, the CHO and PCL were dehydrated thoroughly at 90 °C for 8 h under vacuum. Toluene, obtained from Aladdin Reagent Co. (Beijing, China), was dried with P₂O₅ and re-distilled under vacuum. Phosphate buffered saline (PBS, pH = 7.4) came from Shanghai Yuanmu Biological Technology Co., Ltd., Shanghai, China.
According to our previous publish paper [23 (link)], the biodegradable SPU was prepared by reaction of PCL with well-defined diurethane diisocyanate (HBH) in the presence of Sn(Oct)₂, and the SPU film with a thickness of 0.3 ± 0.03 mm, which was acquired via solvent evaporation. The chemical structure was confirmed by ¹H NMR and FT-IR, and the molecular weight was measured by GPC (M_w = 109,000, M_n = 80,500, M_w/M_n = 1.35).