Editorial [Hot Topic: Nanomedicine and Drug Delivery (Executive Editors: A.V. Kabanov and K. Levon)]

A new interdisciplinary field of nanomedicine that promises breakthrough advances to human health has emerged over last years. This field develops innovative nanomaterials, tools and devices operating at the nanoscale to diagnose, treat, prevent and monitor diseases and traumatic injury, relieve pain, and, overall, preserve and improve the human health [1]. This field joins physical and engineering sciences with pharmaceutics and medicine to translate newest discoveries in nanoscience into clinical practice. The “next generation” therapies must be able to deliver drugs, radionuclides, therapeutic proteins and recombinant DNA to focal areas of disease or to tumors to maximize clinical benefit while limiting untoward side effects. It is not surprising therefore that the drug delivery field has attracted great attention of the biomedical community. The development of multifunctional, spatially ordered, architecturally varied nanosystems for targeted drug delivery is also seen as a priority in nanomedicine [1]. The knowledge and experience in interactions of nanosized drug delivery systems is invaluable for the nanomedicine researchers. Several nanosized drug delivery systems have already been approved for clinical use and more nanomaterials are being evaluated in clinics [2]. Thus nanomedicine is not only “futuristic” but also “realistic” field with a near-term prospective to improve human health. A symposium series focusing on the problems of nanomedicine and drug delivery has started several years ago - the Fourth International Nanomedicine Symposium is planned for October 8th-10th, 2006 (www.nanodds.org). By gathering basic and clinical scientists with the common interest of using nanotechnology in the delivery of therapeutic and diagnostic agents this symposium series aims at narrowing the gap between research communities in academia, government and industry. This issue presents a collection of selected review articles by the speakers and attendees of the Second Nanomedicine and Drug Delivery Symposium held in Brooklyn, NY in August 2004. One promising class of nanomaterials for drug delivery are polymer micelles. They were first proposed in 80'-ies as nanocontainers for biological agents by H. Ringsdorf, A. Kabanov and K. Kataoka [3-5], and have now attracted great attention in the literature. Polymer micelles can incorporate drugs into the hydrophobic polymer core protected by a hydrophilic polymer corona. The corona enables long circulation times of the micelles in the body and prevents the affect of the drugs entrapped in the core on the non-target cells. By modifying the surface of the micelles with antibodies, the site specific delivery and release of the payload at the disease site has been achieved. Several polymer micelle systems are now evaluated in clinical trials. The article by S.R. Croy and G.S. Kwon [6] opens the current issue with a comprehensive overview of this rapidly developing field. The second article by C. Allen and colleagues focuses on the problems of drug loading within the micelles and drug release from the micelles [7]. The interactions between the drug and the micelle core are discussed in terms of their influence on the drug loading and release properties of the micelles. The balance between drug loading and micelle stability is highlighted as a critical factor in the optimization of micelle-drug formulations. The methods employed to prepare drug-loaded micelles and the drug release assays are reviewed. The in vivo performance of micelles as delivery systems is evaluated by comparing the pharmacokinetics of free drug and drug administered in micelle-based formulations. A different approach to drug loading and release was realized in a relatively new class of nanosized drug carriers called “nanogels”. First proposed in the end of the 90'-ies the nanogels represent cross-linked networks of water soluble polymers of nanoscale size. These networks are swollen and do not have a hydrophobic core in aqueous dispersions in the absence of the drug. However, the added drug can spontaneously bind to the polymer chains of the nanogels, for example, due to electrostatic interactions, and become entrapped in nanogel particles. This method allows for very high degrees of loading of drugs in nanogels. Nanogels are “ soft ” materials that change shape and volume as the chemical composition of the environment changes or upon interaction with the cell membranes. These properties can be used facilitate the release of the loaded drugs within the target cells. The work on nanogels and other colloidal microgels has been overviewed by S. Vinogradov [8]. The theme of colloidal gels is continued by Kazakov and Levon in the fourth article of this issue [9].........