Читать книгу Green Nanomaterials - Siddharth Patwardhan - Страница 27

Theragnostics is quite simply the combination of both an imaging/diagnostic modality with a treatment of the disease (figure 2.8(Di)). It stands to reason that once a nanoparticle has been designed to locate a disease and visualised it, it would seem sensible and economical to provide a drug-payload or therapeutic treatment on the same particle, which has already reached its target. There is some debate as to whether or not theragnostics falls between two stools, in the sense that designing a combined ‘all singing, all dancing’ nanoparticle may end up doing both jobs to an okay standard, whereas actually designing a particle for one specific purpose may achieve better results. However, as we have seen throughout this section on nanomedicine, many nanomaterials, as well as coating and drugs, are multifunctional, so many theragnostic treatments are thus widely reported in the literature. For example, MNPs can use magnetic force to target the MNP to the site of a tumour, can be visualised with MRI and MPI, and can be heated with either a magnetic field or photothermia. Gold can be visualised with SPR and heated with photothermia, while both can be decorated with drugs and targeting agents such as biomarkers and antibodies and coated with biocompatible/targeting/smart activating polymers/membranes. Thus, a therapy can quite often couple as a imaging tool/diagnostic without any extra complexity and thus biological or synthetic penalty, and this is where the real advantages lies. The number of theragnostics currently being researched is too vast to describe here, so we will examine one example with multiple features. Figure 2.8(Dii) shows Fe@Si–DOX–CD–PEG [19]. Here a SPION forms a magnetic centre which can be magnetically targeted to the tumour. It can also be used as an MRI contrast enhancer offering targeting and imaging capability. The SPION is then coated in nanoporous silica, in which DOX can be loaded into the pores acting as a drug trap. This particle is then coated with PEG to provide biocompatible and cancer responsive cyclodextrin, which blocks the pores until the nanoparticle reaches the cancer site. At the site the cyclodextrin is cleaved off releasing the DOX from the silica pores [19].