Preface [Hot topic: Macromolecules in the Medical and Pharmaceutical Biotechnology (Guest Editor: Yoshinori Kato)]

Properties and utilities of macromolecules have been studied in various fields for many years. At the publication of this Issue, articles from PubMed alone related to ‘polymer’ only approximated 170,000 for the last 40 years. These macromolecules have primarily been investigated and used in the medical, pharmaceutical and biotechnology fields to modulate drug delivery and provide optimal safety for human applications. This Special Issue focuses on polymers that are currently available for clinical use. Natural polymers can be classified into two categories, plasma components (e.g., proteins and lipoproteins) and plant- or animal-derived polysaccharides. These polymers have been traditionally studied because of their favorable safety profile. Synthetic polymers, such as poly(lactide-co-glycolide) (PLGA) and N-(2-hydroxypropyl) methacrylamide copolymers (HPMA), have been also throroughly studied. PLGA is for instance currently used in commercial products for cancer treatment (leuprolide acetate formulated with PLGA: Lupron Depot(r) (TAP Pharmaceutical Products Inc., IL, USA), Eligard(r) (Atrix Laboratories, Inc., CO, USA)) and HPMA-drug conjugates are being evaluated in clinical trials. Additional synthetic polymers such as ethylene-co-vinylacetate and polyvinylacohol also possess attractive properties that are exploited in drug delivery systems. Other polymers, usually regarded as ‘intelligent polymers’, that respond with large property changes to small physical and chemical stimuli are increasingly being investigated. In addition to their applications as pharmaceutical drug delivery systems, polymers are also intensively explored in tissue engineering and gene therapy. This Special Issue deals comprehensively with various topics such as in vitro and in vivo characteristics, toxicity, current use and future applications of the above-mentioned polymers. The article titled “Safety and Utilization of Blood Components as Therapeutic Delivery Systems” by Dr. Adams et al. discusses various drug delivery systems using blood components such blood cells and lipoproteins. Dr. Mehvar intriguingly reports on drug delivery systems using polysaccharaides with a central focus on dextran and pullulan in the review titled “Recent Trends in the Use of Polysaccharides for Improved Delivery of Therapeutic Agents: Pharmacokinetic and Pharmacodynamic Perspectives”. Dr. Kato et al. summarize the applications of chitin and chitosan derivatives for hospital preparations and drug carriers, and emphasize the usefulness of these compounds in the review titled “Chitin and chitosan derivatives in the pharmaceutical field”. Dr. Rihova et al. provide an update on Phase I data using N-(2-hydroxypropyl) methacrylamide copolymers in the article titled “Clinical Implications of N-(2-Hydroxypropyl)methacrylamide Copolymers”. The article titled “Contribution of Poly(amino acids) to Advances in Pharmaceutical Biotechnology” by Dr. Chiang et al. describes the role for poly(amino acids) in drug delivery systems including their use in ‘hot topics’ such as vaccine and gene delivery. Dr. Shastri describes the applications of non-biodegradable polymers, including marketable products in the medical field, in the review titled “Non-degradable Biocompatible Polymers in Medicine: Past, Present and Future”. The final contribution from Dr. Bromberg describes an overview on intelligent polymers in the review titled “Intelligent Polyelectrolytes and Gels in Oral Drug Delivery”.