Kits and compositions for producing an alginate gel are disclosed. The kits and compositions comprise soluble alginate and insoluble alginate/gelling ion particles. Methods for dispensing a self-gelling alginate dispersion are disclosed. The methods comprise forming a dispersion of insoluble alginate/gelling ion particles in a solution containing soluble alginate, and dispensing the dispersion whereby the dispersion forms an alginate gel matrix. The methods may include dispensing the dispersion into the body of an individual. An alginate gel having a thickness of greater than 5 mm and a homogenous alginate matrix network and homogenous alginate gels free of one or more of: sulfates citrates, phosphates, lactates, EDTA or lipids are disclosed. Implantable devices comprising a homogenous alginate gel coating are disclosed. Methods of improving the viability of pancreatic islets, or other cellular aggregates or tissue, following isolation and during storage and transport are disclosed.