It is very important to apply drug delivery system (DDS) to modern medicine. Because DDS is useful for transplantation, regeneration and gene therapy. For example, cell transplantation using DDS may cover the shortness of donor for organ transplantation. Regeneration also needs high technology including DDS. Liposome is one of the most promising careers, and has a lot of possibility. Polyethylene glycol (PEG)-coated on the liposomal surface reduces the uptake by reticuloendothelial system to prolong the circulation in blood. As for active targeting following passive targeting to the target site, PEG-immunoliposomes were studied in terms of the targeting and receptor-mediated endocytosis into the target cells. Our data show PEG-immunoliposomes are more effective than PEG-liposomes for systemic fungal infection. Since non-viral vectors such as liposcme have fewer side effects than viral vectors, non-viral vectors are suitable to gene therapy for many patients with common diseases. Alternatively, poor transfection efficiency is the major drawback of non-viral vector. If the transfection efficiency can be improved, the non-viral vectors would have potential of becoming the vectors for choice for gene therapy. We revealed that addition of ligand nr lectin to liposome yields large enhancement of transfection efficiency in human lung cancer cells. These results indicated ligand or lectin-facilitated transfection is an efficient gene delivery strategy. Employment of cell type-specific ligands or lectins may allow for efficient cell type-specific gene targeting. Finally, DDS will be able to play an important role in the modern medicine as long as we keep the right way to use DDS for medicine.

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The objective of regenerative medicine is to assist the regeneration and repairing of body tissue defect in the size as large as impossible to self-repairing or to substitute the biological functions of damaged organs by making use of cells of high potential. However, it is often tough to realize the regeneration of tissue only by giving the cells to a body defect. For successful tissue regeneration, it is key to artificially create a site suitable for regeneration induction at the defect. This can be achieved by combinationally taking advantage of an artificial scaffold with 3-demensional structures for cell proliferation and differentiation as well as growth factors. Tissue engineering is a biomedical form to technologically assist the site creation with biomaterials. Growth factor is often required to promote tissue regeneration while it can also induce angiogenesis which is effective in supplying oxygen and nutrients to survive the cells transplanted for organ substitution. However, one cannot always expect the biological effects of growth factor because of its poor in vivo stability, unless its drug delivery system (DDS) is contrived. This paper describes recent research results of tissue engineering based on the DDS technology to discuss possibility of the clinical applications, briefly overviewing the significant role of biomaterials in tissue engineering.

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Hepatocyte growth factor (HGF) was discoverd and cloned as a hepatotropic factor in our laboratory. HGF is now recognized to play an essential role in tissue repair and organ protection during progression of parenchymal injuries. In the recent 10 years, we have demonstrated that HGF is useful as a therapeutic agent in several organ failures, using animal models. For example, HGF prevents onset of acute organ failure, such as fulminant hepatitis, acute renal failure and myocardial infarction. Furthermore, HGF accelerates tissue repair and stimulates recovery from the organ dysfunctions as a tissue repair factor. Of importance, HGF could improve pathophysiological conditions in chronic fibrotic clisorders (including liver cirrhosis, chronic renal failure, cardiomyopathy and so on), accompanied with parenchymal regeneration and reduction in interstitial fibrosis. Based on the experimental backgrounds, HGF gene therapy has been initiated in Japan, focusing on ASO patients. We discuss herein a possible clinical use of HGF as a self-repair therapy for several injured organs.

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Positron Emission Tomography (PET) is a tool for imaging and evaluation of human physiology and function. It has recently been available in more than thirty hospitals and become popular in Japan. PET utilizes positron-emitting radionuclides such as ¹¹C, ¹³N, ¹⁵O, and ¹⁸F : most of them are constituent of molecules in our body. Radioactive compounds with positron emitter have been developed and used for specific purposes. Blood perfusion, oxygen consumption, and glucose utilization are routinely performed in many institutions and visually expressed by the tomographic map with absolute pixel-by-pixel value. ¹⁸F-FDG uptake correlates with glucose utilization in tissue and is widely used for evaluating malignant tumors as well as brain function and myocardial viability. In the United States, FDA and the Health Care Financing Administration (HCFA) have recently reviewed usefulness and cost-effectiveness of FDG PET for the diagnosis of lung cancer, colon cancer, esophageal cancer, malignant lymphoma, malignant melanoma, head and neck cancer, myocardial viability, and epileptic focus. They decided to request expanded Medicare reimbursement for FDG PET to include these diseases in December 2000. We provide a brief summary of FDG PET literature and clinical examples of these diseases in this article. There have been many tracers available for tumor imaging and some of them are clinically useful. Since PET utilizes radiolabeled molecules specific for disease process, development of new radiopharmaceuticals could makes it possible to use this modality for molecular imaging in the future.

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After the publication of a draft sequence of the complete human genome, many biomedical projects are now in progress in view of a post-genome era. Inherited differences in DNA sequence contribute to phenotypic variation, influencing risk of many diseases and response to the environment, foods and drugs. The analysis and medical application of DNA polymorphisms, especially the single nucleotide polymorphism, are most promising among many post-genome projects. In this review, we discuss the prospects and hopes of the DNA polymorphism analysis to promote the tailor-made medicine. In the field of oncology, the prediction of the susceptibility and progression of prostate cancer may be one of the most interesting aspects of the DNA polymorphism analysis.

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Transdermal drug delivery systems (TDDS) offer several advantages over other administration routes. Clinically, several drugs, e. g. nitroglycerin and tulobuterol etc., have been used successfully in TDDS. However only a limited number of drugs can penetrate the skin sufficiently due to the inherent function of the skin which is to exclude external chemicals. In order for broader classes of drugs to be successfully delivered across the skin, the technology of percutaneous penetration enhancement, both in the form of chemical entities and physical methods has been the subject of research. Although some chemical enhancers or enhancement formulations have been used in TDDS, their potential may not be sufficient for rnacromolecular medicine as used in injection. Therefore, a physical enhancement method provide more potential to deliver drugs though the skin more powerfully and precisely. In this review, we focus on the physical enhancement approach as we believe it is the key to the future development of TDDS. In particular, iontophoresis and sonophoresis technologies are overviewed for their principle mechanisms, characteristics and the present situation of their development. Other physical enhancement approaches, like microneedles and electroporation etc. are also explained briefly.

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Two natural polyelectrolytes, sodium alginate and carboxymethyl cellulose sodium salt, were gelated by entrapping method with vinyl monomer and crosslinker. Those gels repeated shrinkage and swelling under the on-off switching of electric field. The drug included in the gel was released with on-off switching of electric field. The electro-responsive weight change and drug release were affected by voltage of electric field.

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