title: Drug delivery systems for differential release in combination therapy.
abstract: BACKGROUND
  Combination therapy with multiple therapeutic agents has wide applicability in medical and surgical treatment, especially in the treatment of cancer. Thus, new drug delivery systems that can differentially release two or more drugs are desired. Utilizing new techniques to engineer the established drug delivery systems and synthesizing new materials and designing carriers with new structures are feasible ways to fabricate proper multi-agent delivery systems, which are critical to meet requirements in the clinic and improve therapeutic efficacy.
  
  
  METHODS
  This paper aims to give an overview about the multi-agent delivery systems developed in the last decade for differential release in combination therapy. Multi-agent delivery systems from nanoscale to bulk scale, such as liposomes, micelles, polymer conjugates, nano/microparticles and hydrogels, developed over the last 10 years, have been collected and summarized. The characteristics of different delivery systems are described and discussed, including the structure of drug carriers, drug-loading techniques, release behaviors and consequent evaluation in biological assays.
  
  
  CONCLUSIONS
  The chemical structure of drug delivery systems is the key to controlling the release of therapeutic agents in combination therapy, and the differential release of multiple drugs could be realized by the successful design of a proper delivery system. Besides biological evaluation in vitro and in vivo, it is important to speed up practical application of the resulting delivery systems.
authors.affiliation: University of Science and Technology Beijing, School of Materials Science and Engineering, Beijing, PR China.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Zhang
authors.forename: Guojie
authors.initials: G
authors.lastname: Wang
authors.forename: Huai
authors.initials: H
authors.lastname: Yang
mesh_terms: D004337:Drug Carriers / Q000737:chemistry / Q000627:therapeutic use; D004339:Drug Compounding / Q000379:methods / Q000639:trends; D016503:Drug Delivery Systems / Q000379:methods* / Q000639:trends; D004359:Drug Therapy, Combination / Q000379:methods* / Q000639:trends; D036103:Nanotechnology / Q000639:trends
chemical_list: D004337:Drug Carriers