Investigation of porous graphitic carbon at high-temperature liquid chromatography with evaporative light scattering detection for the analysis of the drug combination artesunate—Azithromycin for the treatment of severe malaria

Artesunate combined therapies represent the best option for the treatment of malaria and require the development of new methods of analysis. Retention, selectivity and detection with high-temperature liquid chromatography-porous graphitic carbon-evaporative light scattering detection was studied for artesunate and azithromycin separation. Organic solvent, concentration of organic modifiers, temperature and flow rate were all relevant parameters to optimize this separation. The behaviour of artesunate in the tested conditions appeared close to a neutral compound. In CH₃OH, only azithromycin retention was dramatically altered depending on the [triethylamine]/[formic acid] ratio and on the temperature, whereas in CH₃CN, azithromycin, artesunate, artemisinin and dihydroartemisinin retentions decreased with the temperature increase whatever the organic modifier ratio. The best efficiency was obtained with CH₃CN. 25% variation of the concentration values of the organic modifiers did not significantly influenced the retention. The sensitivity of ELSD increased with the flow rate decrease. Peak area and S/N ratio dramatically decreased with the flow rate increase by 10- and 5-fold for artesunate and azithromycin, respectively. Non-linear calibration curves were obtained for both artesunate and azithromycin.     

Removal of malaria-infected red blood cells using magnetic cell separators: A computational study

High gradient magnetic field separators have been widely used in a variety of biological applications. Recently, the use of magnetic separators to remove malaria-infected red blood cells (pRBCs) from blood circulation in patients with severe malaria has been proposed in a dialysis-like treatment. The capture efficiency of this process depends on many interrelated design variables and constraints such as magnetic pole array pitch, chamber height, and flow rate. In this paper, we model the malaria-infected RBCs (pRBCs) as paramagnetic particles suspended in a Newtonian fluid. Trajectories of the infected cells are numerically calculated inside a micro-channel exposed to a periodic magnetic field gradient. First-order stiff ordinary differential equations (ODEs) governing the trajectory of particles under periodic magnetic fields due to an array of wires are solved numerically using the 1st to 5th order adaptive step Runge-Kutta solver. The numerical experiments show that in order to achieve a capture efficiency of 99% for the pRBCs it is required to have a longer length than 80 mm; this implies that in principle, using optimization techniques the length could be adjusted, i.e., shortened to achieve 99% capture efficiency of the pRBCs.     

Mathematical Modelling of Malaria with Treatment

This paper proposes a Susceptible-Infective-Susceptible (SIS) model to study the malaria transmission with treatment by considering logistic growth of mosquito population. In this work, it is assumed that the treatment rate is proportional to the number of infectives below the capacity and is constant when the number of infectives is greater than the capacity. We find that the system exhibits backward bifurcation if the capacity is small and it gives bi-stable equilibria which makes the system more sensitive to the initial conditions. The existence and stability of the equilibria of the model are discussed in detail and numerical simulations are presented to illustrate the numerical results.