Ngf β

Aminated PLA electrospinning solution was prepared by dissolving 0.5 g aPLA (Mw = 100 kDa, Mw/Mn = 2.06, Ruixi, Xi’an, China) in 4 g DCM (Sinopharm, Beijing, China), and 2 g N, N-dimethylformamide (DMF, Lingfeng, Shanghai, China) to obtain uniform and stable solution under magnetic stirring at room temperature. The preparation method of PLA (Mw = 100 kDa, Mw/Mn = 1.61, Daigang, Jinan, China) electrospinning solution is the same as above. The preparation of microsol electrospinning started with the preparation of sodium hyaluronate hydrosol (1 wt%) (HA, Mw = 0.5 MDa, Yuancheng, Wuhan, China), which was obtained by dissolving 0.1 g HA in 9.9 g deionized water and rotating to complete dissolution at room temperature⁴⁷ . Rat β-NGF (R&D System, USA) was resuspended in 0.1 wt% bovine serum albumin (BSA; Solarbio, Beijing, China) solution to achieve the final concentration of 100 μg ml⁻¹. The uniform HA-β-NGF hydrosol was obtained by mixing 10 μl resuspended β-NGF with 50 μl HA solution, after which 0.01 g Span-80 (Sigma, USA) and 4 g DCM were added into the mixture and stirred at high speed for 30 min at room temperature to obtain a homogeneous and stable water-in-oil emulsion containing β-NGF microsol particles. The microsol (MS) spinning solution was obtained eventually by adding 0.5 g aPLA and 2 g DMF into the emulsion.

PC12 cells were seeded on the 24-well plate at 1.0 × 10⁴ cells. Twelve h after seeding, the PC12 cells were differentiated by treating with 100 ng/mL NGF-β (Sigma-Aldrich), and each concentration of Pd(bpy) was added simultaneously in DMEM supplemented with 100 unit ml^–1 penicillin and 100 µg ml^–1 streptomycin and 2% FBS. After incubation for 3 days, PC12 cells bearing neurites were randomly selected, and the length of the longest neurite in each cell was measured using ImageJ package Fiji.