Self-assembling peptide hydrogels are used to directly encapsulate and controllably release model FITC-dextran macromolecules of varying size and hydrodynamic diameters. MAX1 and MAX8 are two peptide sequences with different charge states that have been designed to intramolecularly fold and self assemble into hydrogels at physiological buffer conditions (pH 7.4, 150 mM NaCl). When self-assembly is initiated in the presence of dextran or protein probes, these macromolecules are directly encapsulated in the gel. Self-diffusion studies using fluorescence recovery after photobleaching (FRAP) and bulk release studies indicate that macromolecule mobility within, and release out of, these gels can be modulated by varying the hydrogel mesh size. The average mesh size can be modulated by simply varying the concentration of a given peptide used to construct the gel or by altering the peptide sequence. In addition, results suggest that electrostatic interactions between the macromolecules and the peptide network influence mobility and release. Depending on probe size, release half-lives can be varied from 8h to over a month.