Compositions and methods for controlled release of target agent

A composition comprising one or more hydrogel forming polymers, said hydrogel enables sustained release of a target agent, at least one of said one or more hydrogel forming polymers comprises a degradable backbone, and wherein said degradable backbone comprises precursor polymers linked by a degradable linker,

• wherein said hydrogel forming polymer is selected from the group consisting of a polysaccharide, a polyethylene glycol, a derivative thereof, and any combinations thereof;
• comprising at least a first hydrogel forming polymer derivative and a second hydrogel forming polymer derivative, wherein said first hydrogel forming polymer derivative comprises a first modification and said second hydrogel forming polymer derivative comprises a second modification, said first modification is different from said second modification, and said first polymer derivative is capable of reacting with said second polymer derivative to form said hydrogel;
• wherein a mass ratio between said first hydrogel forming polymer derivative and said second hydrogel forming polymer derivative in said composition is from about 3:1 to about 1:3;
• or
• wherein a molar ratio between said first hydrogel forming polymer derivative and said second hydrogel forming polymer derivative in said composition is from about 10:1 to about 1:10;
• or
• wherein a volume ratio between said first hydrogel forming polymer derivative and said second hydrogel forming polymer derivative in said composition is from about 3:1 to about 1:3;
• or
• wherein said first hydrogel forming polymer derivative has a first DM, said second hydrogel forming polymer derivative has a second DM, and a ratio between said first DM and said second DM is from about 3:1 to about 1:3.