2.1. Materials
2-Azidoethyl β-D-galactopyranoside was purchased from Synthose Inc. (Canada), polyethyleneimine (Mw 1800 Da) was purchased from Polysciences, Inc. (Germany), polyethyleneimine (PEI), 1.8 kDa, branched was obtained from polyscience (USA), stannous octoate, tetraethyl orthosilicate (TEOS), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), polyvinyl alcohol (PVA), dichloromethane (DCM), MTT, RPMI 1640, DMSO, penicillin/streptomycin solution, N-hydroxylsulfosuccinimide (NHS), fetal bovine serum (FBS) were purchased from Sigma-Aldrich (USA). HO-PEG-COOH was obtained from Rapp Polymere GmbH (Germany). N- hydroxysuccinimide, Folic acid and dicyclohexylcarbodiimide were purchased from Acros (Germany). Agarose gel, PVP, MgCL2, Tris-HCl, and EDTA were purchased from Merck (Germany).