Chitosan hydrochloride

Partially hydrolyzed PVA (Mowiol 26–88 (KURARAY POVAL 26–88)) with a molecular weight of 160,000 g/mol and an 87.7 percent degree of hydrolysis was supplied by ZAUBA (Munchen, Germany) and used as received. Chitosan hydrochloride (Mw = 302.11 kDa, DAC degree = 82%), titanium (IV) oxide nanopowder (21 nm primary particle size), and glacial acetic acid were purchased from Sigma-Aldrich (St. Louis, MO, USA). 3,3′-Diaminodiphenyl sulfone, 4-hydroxybenzaldehyde, tetrahydrofuran anhydrous (THF), N,N-dimethylformamide (DMF), and phenylphosphonic dichloride were purchased from Sigma-Aldrich (Taufkirchen, Germany).
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was purchased from Chemos GmbH, Germany and dehydrated before use. Polyphosphonate additive (PFR-3) has been prepared in our laboratory according to an adopted procedure from a previous work [47 (link)], starting from 3,3′-diaminodiphenyl sulfone and 4-hydroxybenzaldehyde. All other reagents were used as received from commercial sources.

Lysostaphin (720 U/mg) was produced by Shanghai High-Tech United Biotechnological R&D Co. Ltd. (Shanghai, China). Chitosan hydrochloride (degree of deacetylation = 93%; M_w = 110,000–150,000) was purchased from Sigma-Aldrich China Mainland Co. Ltd. (Shanghai, China). Ca(OH)₂, CaCO₃, NaHCO₃, CA, CH₃COOH, NaH₂PO₄, and CaCl₂ were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China); poloxamer (F68) was donated by BSAF (Shanghai, China); sodium pentobarbital was purchased from Aladdin Reagent Co., Ltd. (Shanghai, China). Tissue culture media, simulated body fluid (SBF), phosphate-buffered saline (PBS) and methylthiazol tetrazolium (MTT) reagent kits were supplied by Sangon Biotech Shanghai Co. Ltd. (Shanghai, China). Qdot 625 ITK Carboxyl Quantum Dots were purchased from Life Technologies Corporation (Shanghai, China).
Cells from cell line MC 3T3-E1 (a clone from newborn mouse calvaria, which is often used in bone tissue engineering research [34] (link)) were cultured in Eagle's minimum essential medium (Eagle MEM; BioWhittaker, MD, US) supplemented with 10% newborn calf serum (NBCS; Life Technologies Co., Shanghai, China), 60 µg/mL kanamycin sulfate (Aladdin, Shanghai, China), and 100 µg/mL streptomycin sulfate (Aladdin, Shanghai, China).