## 4 Biological Applications
### Therapeutic Applications
#### 4.2.1 Thermal Treatments
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Application** & **Principle** & **Materials** & **Reference** \\ \hline \multirow{8}{*}{**Sensing**} & LSPR shift & AuAg & [163] \\ \cline{2-3}  & Surface-enhanced Raman scattering (SERS) & AuAg & [76] \\ \cline{2-3}  & & AuAg & [166] \\ \cline{2-3}  & GMR sensor; competition assay & FeCo & [112; 113; 187] \\ \cline{2-3}  & Magnetic capture & FePt & [171] \\ \cline{2-3}  & Magnetically-enhanced colorimetric biosensing & PtCo & [117] \\ \cline{2-3}  & QCM with magnetically controlled permeability & AuCo & [80] \\ \cline{2-3}  & Electrochemical biosensor & PtPd & [96] \\ \hline \multirow{8}{*}{**Imaging**} & An imaging probe screening with dual energy mammography or computed tomography & AuAg & [71] \\ \cline{2-3}  & The optical absorption cross sections & AuAg & [72] \\ \cline{2-3}  & MRI contrast agent (no imaging) & FePt & [103] \\ \cline{2-3}  & & FePt & [105] \\ \cline{2-3}  & MRI in vitro & FeNi & [115] \\ \cline{2-3}  & PtCo & [40] \\ \cline{2-3}  & & AuCu & [84] \\ \cline{2-3}  & MRI in vivo & FeCo & [110] \\ \cline{2-3}  & & FePt & [177] \\ \cline{2-3}  & Dual modal CT/MRI molecular imaging & FePt & [132] \\ \cline{2-3}  & in vitro and in vivo & FeCo & [111] \\ \cline{2-3}  & MRI and near-infrared agents & FeCo & [111] \\ \hline \multirow{8}{*}{**Imaging**} & Multimodal imaging & & \\ \cline{2-3}  & Computed tomography (CT), & & \\ \cline{2-3}  & Magnetic resonance imaging (MRI), & & \\ \cline{2-3}  & Photoacoustic (PA) imaging, & & \\ \cline{2-3}  & High-order multiphoton luminescence & & \\ \cline{2-3}  & (HOMPL) microscopy & & \\ \cline{2-3}  & & in vivo Multimodal SERS-MRI-CT imaging & AuFe & [79] \\ \cline{2-3}  & in vivo NIR thermal imaging and & AuPt & [95] \\ \cline{2-3}  & photoacoustic imaging & & \\ \hline \multirow{8}{*}{**Drug delivery**} & in vitro hyperthermia & FePt & [109] \\ \cline{2-3}  & Photothermal & FePt & [104] \\ \cline{2-3}  & Hyperthermia & CuNi & [119; 188] \\ \cline{2-3}  & Tumor chemo-photothermal therapy & AuPt & [95] \\ \hline \multirow{8}{*}{**Drug delivery**} & Drug carrier by pore structure and release by photothermal conversion & & \\ \cline{2-3}  & Gene delivery by functionalized surface & AuNi & [83] \\ \cline{2-3}  & Drug delivery by pore structure & AuPt & [95] \\ \cline{1-1} \cline{2-3}  & Photothermally enhanced photodynamic therapy & PdAg & [118; 189] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Bimetallic nanoparticles in biological applications. In the presence of an alternating magnetic field, magnetic nanoparticles continuously generate energy as heat due to Neel and Brownian relaxation [37; 190; 191]. The heating efficiency of a magnetic nanoparticle is determined from the specific loss power (SLP), which is a measurement of the change in temperature per unit volume or mass of the nanoparticles [37; 98]. The SLP values are proportional to the M\({}_{\text{s}}\) value but inversely proportional to the size distribution of the nanoparticles [37]. The optimized magnetic anisotropy and size also can enhance the SLP. Therefore, a material with a high SLP value can bring enhanced efficacy with a lower number of nanoparticles. Temperature control in this type of application can be achieved with an intense alternating magnetic field and a particle with a low Curie temperature (T\({}_{\text{c}}\)), typically in the range of 42 to 46 \({}^{\circ}\)C [191; 192; 193]. Magnetic nanoparticles with a low Curie temperature (the temperature at which magnetic materials transition between ferromagnetic and paramagnetic properties) can be effectively heated to a temperature below their T\({}_{\text{c}}\) to prevent damage to neighboring healthy tissues since at these temperatures, there is a decrease in magnetic coupling interactions in the paramagnetic regime. Nanoparticles suitable for magnetic hyperthermia must be biocompatible as well as monodisperse with simultaneously high and self-regulated heating capability, with a desired Curie temperature less than 60 \({}^{\circ}\)C [194].