Thermosensitive biodegradable hydrogels for the delivery of therapeutic agents

Polymeric drug delivery is the most widely studied area of drug delivery in recent years (1). Polymers can be manipulated to possess certain properties that can meet specific criteria for the designing of suitable delivery systems. Polymeric drug delivery systems may provide advantages such as (i) increased efficacy, (ii) reduced side effects and toxicity, and (iii) convenience (1). Like small drugs in general, therapeutic macromolecular drugs require the use of polymeric systems, since these agents have very short half-lives in blood plasma and are susceptible to physical or chemical degradation. Although many therapeutic proteins, peptides, and DNA-based drugs are available due to advances in biotechnology, the conventional routes by which these biotechnologyderived drugs are administered-routes such as intravenous injection, intravenous infusion, subcutaneous injection, and so on-require frequent injections to achieve a therapeutic concentration in blood and may result in poor patient compliance stemming from frequent, painful injections as well as undesirable side effects. Significant research effort has been made to develop implantable or injectable parenteral devices for the sustained and controlled release of protein drugs in order to reduce the frequency of injection (1).