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Cancer is a class of diseases in which a group of cells display uncontrolled growth, invasion and sometimes metastasis. It affects people at all ages, with the risk for most types increasing with age, thus can seriously threaten human health. Cancer alone has caused 7.6 million human deaths worldwide in 2007 and according to the American Cancer Society, about 1.5 million new cancer cases are expected to be diagnosed in 2010 in United States. While there have been tremendous advancements in the treatment of cancer over the past 50 years, cancer continues to be a major health concern. Thus, much research efforts have been dedicated to the search for new therapeutic approaches.
The past century has demonstrated that cancer can be effectively treated with surgery, chemotherapy, and radiotherapy. These treatment strategies, when used either alone or in combination, can significantly impact tumor growth and even produce cures. For many solid tumors, as in colon cancer, improved methods for early diagnosis and combination therapies have had an important impact on survival. However, once the tumor has metastasized, treatment becomes more complicated, as more effective and aggressive chemotherapy would be necessary. The efficacy of these treatment procedures are also limited by the problems with drug dosage form, pharmacokinetics, toxicity and drug resistance. Thus, with the emergence of chemotherapeutic engineering, it is hoped that problems facing cancer chemotherapy would be effectively remedied, thereby ensuring recovery and the quality of life of the patients.
Chemotherapeutic engineering can be defined as the application and development of engineering, especially chemical engineering principles and devices for chemotherapy of cancer and other diseases to achieve the best efficacy with the least side effects. Chemotherapeutic engineering involves various technologies: nanotechnology, liposomes, liposomes-in-microspheres and oral chemotherapy. Nanotechnology with its promising research results brings new hope for significant breakthrough in the near future. As a major technology in chemotherapeutic engineering, nanoparticles may provide an ideal solution for the problems encountered in current course of chemotherapy. This paper aims to give an introduction to cancer nanotechnology and nanomedicine as the future medicine for cancer treatment.
1. Cancer Nanotechnology - Nanoparticle Technology for Chemotherapy
There have been numerous researches in the past decades on cancer nanotechnology. On-going research programs at the National Cancer Institute include novel nanodevices capable of various clinically important functions. These include detecting cancer at its earliest stages, establishing its location, delivering anticancer drugs specifically to malignant cells, and determining if these drugs are killing the malignant cells.
The vast knowledge of cancer genomics and proteomics arising as a result of the Human Genome Project has provided many important details of how cancer develops. This allows scientists to better understand the molecular basis of cancer. Thus, with the combination of interdisciplinary efforts between sciences and engineering, it is now possible to turn the knowledge of genomics and nanotechnology into medical devices and technology that can improve mankindâ€™s ability to diagnose, treat, and prevent cancer in the near future.
Nanotechnology refers to the interactions of cellular and molecular components with the engineered material such as atoms, molecules, and molecular fragments at the most fundamental level of biology. Such nanoscale objects, typically with dimensions smaller than 100 nanometers, can be useful by themselves or as part of larger devices containing multiple nanoscale objects.
At the nanoscale, the physical, chemical, and biological properties of materials differ fundamentally and often unexpectedly from those of the corresponding bulk material because the quantum mechanical properties of atomic interactions are influenced by material variations on the nanometer scale. In fact, by creating nanometer-scale structures, it is possible to control fundamental characteristics of a material, including its melting point, magnetic properties, and even color, without changing the materialâ€™s chemical composition.
Nanoscale devices and nanoscale components of larger devices are of the same size as biological entities. As a result, nanoscale devices can readily interact with biomolecules on both the cell surface and within the cell, often in ways that do not alter the behavior and biochemical properties of those molecules. From a scientific viewpoint, the actual construction and characterization of nanoscale devices may contribute to understanding carcinogenesis.
Noninvasive access to the interior of a living cell affords the opportunity for unprecedented gains on both clinical and basic research frontiers. The ability to simultaneously interact with multiple critical proteins and nucleic acids at the molecular scale should provide better understanding of the complex regulatory and signaling networks that govern the behavior of cells in their normal state and as they undergo malignant transformation. Nanotechnology provides a platform for integrating efforts in proteomics with other scientific investigations into the molecular nature of cancer. Similarly, nanoscale devices could prove that they can deliver therapeutic agents that can act within the cell or even within specific organelles.
Nanoscale devices have the potential to radically change cancer therapy for the better and to dramatically increase the number of highly effective therapeutic agents. Nanoscale constructs, for example, should serve as customizable, targeted drug delivery vehicles capable of ferrying large doses of chemotherapeutic agents or therapeutic genes into malignant cells while sparing healthy cells, which would greatly reduce or eliminate the often unpalatable side effects that accompany many current cancer therapies.
Already, research has shown that nanoscale delivery devices, such as dendrimers, silica-coated micelles, ceramic nanoparticles, and cross-linked liposomes, can be targeted to cancer cells. As efforts in proteomics and genomics uncover other molecules unique to cancer cells, targeted nanoparticles could become the method of choice for delivering anticancer drugs directly to tumor cells and their supporting endothelial cells. Eventually, it should be possible to mix and match anticancer drugs with any one of a number of nanotechnology-based delivery vehicles and targeting agents, giving researchers the opportunity to fine-tune therapeutic properties without needing to discover new bioactive molecules.
While work with naturally existing nanostructures is promising, chemists and engineers have already made substantial progress turning synthetic materials into multifunctional nanodevices. Dendrimers, 1- to 10-nanometer spherical polymers of uniform molecular weight made from branched monomers, are proving particularly adept at providing multifunctional modularity. Already, some dendrimer-based constructs are making their way toward clinical trials for treating a variety of cancers.
Such multifunctional nanodevices, sometimes referred to as nanoclinics, may also enable new types of therapeutic approaches or broader application of existing approaches to killing malignant cells. Once these so-called nanoclinics have been taken up by the target cell, they can not only be imaged using MRI, but can also be turned into molecular-scale thermal scalpels and destroy cancerous cells.