Foreword

Drug delivery system (DDS) has contributed to significant progress in the field of medicine. Microspheres, nanospheres and liposomes as useful DDS tools are utilized by the entrapment of varied drugs in each carrier, and achieve active or passive targeting to a target site. Polyethyleneglycol (PEG) is a classical but innovative material used as a DDS carrier and drug modification. PEG has superior properties such as high solubility, low immunogenicity and low toxicity.

In this Current Topics, 5 reviews contribute important information on PEG. Shiraishi and Yokoyama describe the significance of PEG in polymeric micelle carrier systems as well as the accelerated blood clearance phenomenon of the polymeric micelles. Ishihara summarizes the effects of modification with PEG on biopharmaceuticals by comparing two products of interferon-α modified with PEG. Furthermore, he describes the benefits of modification with PEG in Doxil® as a modified product on the market and in clinical trial as a drug carrier. Ishida and Kiwada review the induction of anti-PEG antibody responses by PEG modified substances, including several PEG modified proteins and PEG modified nanoparticles. Hatakeyama et al. summarize various strategies to solve PEG dilemmas as specific problems associated with the use of PEG in the delivery of nucleic acids to tumors. Sugiyama and Sadzuka introduce the correlation between the PEG modification of liposomes and fixed aqueous layer thickness as a factor of circulation time of PEG-modified liposomes in the bloodstream. And they describe the effect of different double arms PEG, as a novel PEG-lipid, with long circulation in the bloodstream and high affinity to tumor cells.

This organizer sincerely expects that these reviews will improve for each reader the study of challenges posed by DDS strategies.