Alginate gel beads doped with nanotubes or nanoparticles were prepared using four kinds of dopants: carbon nanotubes (CNTs), silica nanotubes, graphite, or silica nanoparticles (SiO2). The effective diffusion coefficients (D-e) of reduced nicotinamide adenine dinuncleotide (NADH) in hybrid gels were calculated using an unsteady-state model developed by Nguyen and Luong. The maximum De values of NADH in the four kinds of hybrid gels obey the following sequence: D-e (CNTs-alginate) > D-e (silica nanotubesalginate) > D-e (SiO2-alginate) > D-e (graphite-alginate). The effect of the dopant concentration on De was examined at five dopant concentration levels (0.3, 0.5, 0.9, and 1.25) g/L. For the CNTs-alginate and silica nanotubes-alginate gels, the maximum D-e values of NADH were obtained at 0.3 g/L and 0.9 g/L dopant concentrations, respectively. For the silica-alginate and graphite-alginate gels, the maximum D-e values of NADH were obtained at 0.5 g/L dopant concentration. The maximum D-e value of NADH in the CNTs-alginate gel is 50 % larger than the value for the pure alginate gel (D-e0). Owing to their more favorable diffusion characteristics, the doped alginate gels could be used as novel and effective immobilizing carriers for encapsulating biomolecules such as enzymes and cells.