• Microneedle drug delivery system with different drug concentration
  • Hajar Moghadas,1,*
    1. Department of mechanical engineering, Gas and Petroleum Faculty, Yasouj University, 75918-74831, Iran


  • Introduction: Microneedles are new tools for transdermal drug delivery [1]. They are local drug administration. Because of their small dimension, microneedle can’t reach the nerve so they are the pain-free devices that make them more popular than the other kind of drug delivery systems [2]. Different parameters affect the microneedles' drug delivery efficiency, including microneedle shape and material, the loaded drug, and the skin properties [3]. Experimental and numerical investigations can evaluate the effect of each parameter and show the order of their importance [4]. Simulation and numerical analysis are helpful and cost-effective approaches to study the effect of different parameters on the drug delivery ability of the microneedles [5]. In this work, diffusion of the meloxicam (as the sample drug, meloxicam is pain mitigation that is used for some animals like dogs and cats [6]) into the cattle skin is stimulated by the aid of COMSOL software. The effect of the time and drug concentration in the diffusion pattern through the skin is evaluated for a tapered shape microneedle with 250 µm base diameter and 500 µm height.
  • Methods: To simulated drug diffusion from a microneedle in to the skin, COMSOL Multiphasic 5.6 is used. The computational domain is a large rectangular geometry as a piece of skin in which a tapered microneedle is inserted. The microneedle has a 250 µm base diameter and a 500 µm height. The deep of the rectangular domain is chosen 4000 µm and the length of the domain is chosen 5000 µm means 10 times the microneedle base diameter to ensure providing edge effect in the result. The governing equation of the diffusion is applied as bellow: (dc_i)/dt+ ∇∙J_(i )= R_i. (1) And Fick’s first law: J_(i )=-D_i ∇c_i (2) Where c_i is the drug concentration [mol/m3], t is time [s], J_(i )is the flux, Ri [mol/(m3.s)] is the mass source of ci, Di is the diffusion coefficient [m2/s] and ∇ is the gradient operator. The boundary conditions of the computational domain are set as c(0)= 0 for all points in the skin and c(0)= 1∙43×〖10〗^(-4) [mol/m3] for microneedle. Diffusion coefficient of meloxicam is set as D=1∙5×〖10〗^(-9) [m2/s], [6]. The drug diffusion is simulated using Transport of Diluted Species under a time-dependent model for different initial drug concentrations at different time periods.
  • Results: The simulation of the drug diffusion through the cattle skin is shown in figure 1 for initial drug concentration c(0)= 1∙43×〖10〗^(-4) [mol/m3] and c(0)= 2∙86×〖10〗^(-4) [mol/m3] at different time, t=100 s, t=500 s and t=1000 s. After microneedle insertion, the drug will diffuse through the skin. The contours of concentration demonstrate the diffusion pattern by passing time. As illustrated the diffused domain has a circular shape because the skin property is supposed to be isentropic. By increases the time drug diffuse to more region. For higher initial concentration the diffused domain becomes larger at the given time. The obtained simulation results provide valuable data about the effect of microneedle drug concentration on the drug diffusion into the skin.
  • Conclusion: Drug delivery into the skin via a microneedle is simulated at different drug concentrations. The obtained results have valuable data about the drug diffused domain in the skin and the time of the drug insertion. Increasing the time of insertion or initial drug concentration increases the penetration depth of the drug. Microneedles are new pain-free transdermal drug delivery devices and promising powerful tools for modern adjustable and released controllable drug delivery systems into the other organs.
  • Keywords: Microneedle, Drug delivery, Simulation, Concentration