ABSTRACT
It has been widely recognized that boron neutron capture therapy (BNCT) is potentially a promising and powerful binary anticancer therapy in which compounds containing the 10B isotope are selectively introduced into tumor cells and then irradiated with thermal neutrons. The 10B nucleus adsorbs a neutron forming an excited 11B nucleus that undergoes a rapid ™ssion reaction, producing a highenergy α-particle (1.47 MeV) and Li-7 ion (0.84 MeV), in addition to a low-energy gamma γ-ray (478 keV). These particles may cross a cell nucleus and thus destroy a tumor cell, see Figure 7.1 for a proposed cell-killing mechanism. The linear energy transfer (LET) of these heavily charged particles have a range of about one cell diameter [1,2], which con™nes radiation damage to the cell from which they arise, hence minimizing cytotoxic effects on the surrounding tissue. Therefore, if boron can be selectively accumulated, the target region can be dosed with neutrons at a sizeable §ux, but have a minimal effect on the boron-free regions in the beam path. Compared to conventional radiotherapy, boron-10 has the advantages of being nonradioactive without neutron irradiation and easily incorporated with various materials. In principle, the required boron concentration is generally
7.1 Introduction: BNCT Background ......................................................................................... 147 7.2 Nanoscale BNCT Agents ...................................................................................................... 149
7.2.1 Nanoscaled Material-Based Drug Delivery ............................................................. 149 7.2.2 Liposomes-Based BNCT Agents .............................................................................. 149 7.2.3 Dentritic Polymer-Based BNCT Agents ................................................................... 151 7.2.4 Magnetic Nanoparticle-Based BNCT Agents........................................................... 152 7.2.5 Nanotube-Based BNCT Agents ................................................................................ 155
7.2.5.1 Carbon Nanotubes ..................................................................................... 155 7.2.5.2 Boron Nanotubes ....................................................................................... 157 7.2.5.3 Boron Nitride Nanotubes ........................................................................... 157
7.3 Summary .............................................................................................................................. 159 References ...................................................................................................................................... 159
estimated at 10910B atoms (natural abundance 19.9%) per cell, which translates to approximately 35 μg 10B per gram of tissue [3]. To prevent damage to healthy tissue in the path of the neutron beam, the surrounding tissue should contain not more than 5 μg of 10B/g of tissue.
