Objective: Chitosan (CS) and polycaprolactone (PCL) were added into a nerve scaffold of poly(L-lactide acid) (PLLA)/polypyrrole (PPy)-based fibre films to solve the unmatch with the nerve strength and the aseptic inflammation from PLLA. Methods: Poly (L-lactide acid)-polycaprolactone (PLLA/PCL) fibre films coated with chitosan (CS) and polypyrrole (PPy) were prepared by electrospinning of aligned PLLA/PCL fibres, electrochemical deposition of PPy nanoparticles and in situ doping of CS in PPy. PC12 cells were electrically stimulated with 100 mV for 2 hours every day via CS/PPy-PLLA/PCL fibre film to promote the neurite growth. Results: The surface conductivity and tensile strength of CS/PPy-PLLA/PCL fibre films were 1.03 s/m and 13 MPa, respectively. CS content in fibre films was about 7.5 mg/cm 2 , improving the pH value (reached to 5.1) of immersion solution of the fibre film at 16 days. Compared with PPy-PLLA/PCL fibre film, more and longer axons were grown out from PC12 cells cultured on CS/PPy-PLLA/PCL fibre film, indicating the positive effect of CS in fibre film on axon growth. The cell differentiation rate and neurite length on CS/PPy-PLLA/PCL fibre film reached to 38% and 75 μm, respectively. These results suggest the promotion of electrical stimulation on neurite growth and alignment. Conclusions:A synergistic mechanism about the promotion of CS, electrical stimulation and aligned fibres on PC12 cells differentiation, axon outgrowth was proposed.These results indicated the potential application of CS/PPy-PLLA/PCL fibre film in the field of the nerve repair and regeneration.

Three isostructural dl-serine covalently functionalized and multinuclear lanthanide (Ln3+)-embedded arsenotungstates, K2[{As4­W44O137­(OH)18(H2O)2­(dl-Ser)2}­{Ln2­(H2O)4(dl-Ser)}2­{Ln(H2O)7}2]·70H2O (Ln = Sm (1), Eu (2), and Gd (3); dl-Ser = C3H7­NO3), were prepared, where the centrosymmetric [{As4W44­O137(OH)18­(H2O)2­(dl-Ser)2}­{Ln2(H2O)4­(dl-Ser)}2]8– polyanion consists of two {As2W19­O59(OH)8­(H2O)}6– fragments, integrated with a two-dl-serine-ornamented [W6O23(OH)2­(dl-Ser)2­{Ln2­(H2O)4}2]8– segment. In addition, the photochromic transformation of solid-state compounds 1–3 was observed from colorless to blue after a UV illumination of 4 min, and the decay process lasted as long as ∼20 h in the dark. The coloration kinetic half-life (t 1/2) values of compounds 1, 2, and 3 were calculated to be 0.597, 0.920, and 0.723 min, respectively. Furthermore, the luminescent properties and energy migration from arsenotungstates and organic chromophores to Sm3+ and Eu3+ ions in 1 and 2 have been intensively investigated. Further analysis manifests that 1 possesses an effective luminescent switchable behavior, triggered by its fast-responsive photochromism effect.

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