This invention relates to methods of producing collagen biomaterials by admixing (i) a solution of monomeric collagen, (ii) a solution of polymeric collagen, (ii) cargo particles, and (iv) a non-collagen blocking polymer, to produce a collagen solution. The collagen solution is then allowed to solidify to produce a collagen hydrogel. This may be useful in improving the stiffness of collagen hydrogel constructs and increasing the entrapment and retention of cargo particles.