Figure 1: Chemical Structure of cross-linkers. 1, 4-bis (maleimido) butane [BMB, M.Wt. 248.23], 1, 11-bis (maleimido) triethyl glycol [BM (PEG)3, M. Wt. 352.13], Tris (2-maleimidoethyl) amine [TMEA, M. Wt. 386.36].