This work investigates optimal magnetic nanoparticle (MNP) injection strategies in three-dimensional (3D) tumor models to enhance the magnetic hyperthermia efficacy. We consider three tumor models with increasing geometric complexities: a spherical tumor, a simple irregular tumor (two connected spheres of different sizes), and a complex irregular tumor (three connected spheres of varying sizes). Centrosymmetric MNP distributions are employed for the spherical model, whereas asymmetric distributions are applied for the irregular models. The rapid convergence of the optimization demonstrates the efficiency and effectiveness of this 3D optimization framework. For the spherical tumor model, multi-site injections significantly enhance therapeutic outcomes under a 20-min waiting limit, whereas a single-site injection with a 114.9-min waiting time achieves 100% tumor ablation without damaging adjacent healthy tissue. Two injection sites suffice for the simple irregular tumor model, while a three-site strategy is optimal for the complex irregular model, indicating a relationship between required injection number and tumor geometry. Furthermore, the optimal MNP injection strategies correlate positively with the locations and sizes of the connected spheres. These findings produce more practical optimal strategies and provide broader, clinically relevant guidance for magnetic hyperthermia treatment.

Magnetic hyperthermia is a promising cancer treatment method that involves complex multiphysics phenomena, including interstitial tissue fluid flow, magnetic nanoparticle (MNP) transport, and temperature evolution. However, these intricate processes have rarely been studied simultaneously, primarily due to the lack of a comprehensive simulation tool. To address this issue, we develop a comprehensive numerical framework in this study. Using this framework, we simulate a circular-shaped tumor embedded in healthy tissue. The treatment process is examined under two scenarios: one considering gravity and the other neglecting it. Without gravity, the interstitial tissue flow remains stationary, and hence MNP transport and temperature evolution are determined solely by diffusion. The optimal treatment time, when the tumor cells are completely ablated, decreases with both the Lewis number and the heat source number, following a power law. When gravity is considered, treatment efficacy deteriorates due to buoyancy-induced MNP movement, significantly extending the time required to completely ablate the tumor cells. This required time increases with both the buoyancy ratio and the Darcy ratio, also following a power law. The results from this study could provide valuable guidelines for practical magnetic hyperthermia treatment.

We developed a dedicated computational framework by coupling the lattice-Boltzmann-method (LBM) modeling and the particle-swarm-optimization (PSO) algorithm to search optimal strategies of magnetic nanoparticle (MNP) injection for hyperthermia-based cancer treatment. Two simplified tumor models were considered: a circular model representing geometrically regular tumors and an elliptic model representing geometrically irregular tumors, both sharing the same area. The temperature distribution in the tumor and its surrounding healthy tissue was predicted by solving the Pennes’ bio-heat transfer equation (PBHTE). Both single- and multi-site injection strategies were explored. The results suggest that the multi-site injection strategies generally work well, while the single-site injection strategy fails even on the simplest circular tumor model. The more the injection sites, the better the performance. In particular, when the number of injection sites reaches eight, all temperature requirements can be nearly 100% satisfied in both tumor models. Whether or not including the minimum dose requirement in the objective function only affects the optimization results by less than 2%. The thermal dose was also assessed by considering both temperature and heat exposure time. It was found that the optimal multi-site injection strategies perform reasonably well for both tumor models. Although the setting is only two dimensional and the optimization is on very simplified tumor models, the framework adopted in this present study works well and can provide useful insights into magnetic hyperthermia treatment.

For the relevant properties of pristine and doped (Si, P, Se, Te, As) monolayer WS₂ before and after the adsorption of CO, CO₂, N₂, NO, NO₂ and O₂, density functional theory (DFT) calculations are made. Calculation results reveal that the monolayer WS₂ doped with P and As atoms can be substrate materials for NO and NO₂ gas sensors. However, after the subsequent CDD and ELF calculations, it is found that P-doped monolayer WS₂ adsorbs NO and NO₂ in a chemical way, while As-doped monolayer WS₂ adsorbs NO and NO₂ in a physical way. Also, the charge transfer between As-doped monolayer WS₂ and NO is relatively small and not easily detected. Besides, As-doped monolayer WS₂ system exhibits greater differences in optical properties (the imaginary part of reflectivity and dielectric function) before and after the adsorption of NO₂ gas than before and after adsorption of NO gas. These differences in optical properties assist sensor devices in making gas adsorption-related judgments. Through the analysis of the recovery time, DOS and PDOS, As-doped monolayer WS₂ is also verified to be a promising NO₂ sensing material, whose recovery time is calculated to be as short as 0.169 ms at 300 K.

In this work, the adsorption of toxic gaseous NO₂ and other gas molecules (NO, CO, CO₂, N₂, O₂, SO₂) on pristine and X-doped (X = Si, P, S, Te, As) two-dimensional (2D) WSe₂ have been detailed studied by performing density functional theory (DFT) calculations. Calculation results of adsorption energies and adsorption distances demonstrate that As-doped 2D WSe₂ (As-WSe₂) exhibits high selectivity not only towards NO₂, but also towards NO and SO₂. However, the charge transfer between NO and the substrate is too small to detect, and chemical bond forms between SO₂ and the substrate; both phenomena make As-WSe₂ substrate more suitable as a substrate material of the NO₂ sensor. To eliminate the interference of SO₂ on the adsorption of NO₂, coexistence of NO₂ and SO₂ is simulated. Results reveal that although the interaction between SO₂ and the As-WSe₂ substrate is stronger than that between NO₂ and the substrate, SO₂ molecule hardly interacts with the substrate when co-adsorbed with NO₂. Besides, calculation results of DOS and PDOS further confirm the sensitivity of As-WSe₂ towards NO₂; and those of the recovery time also highlight the extremely fast recovery rate of As-WSe₂ after adsorbing NO₂. The present findings make As-WSe₂ monolayer a potential substrate material of NO₂ gas sensors used in the atmospheric environment.