An Er:YAG laser whose wavelength is 2940 nm shows its highest absorption coefficient in the water. Thermal effects such as conduction or diffusion are dominant. This is a potential drawback of a drug delivery system if not properly treated. Growth hormones, namely EGF and HGH, are used to investigate the potential thermal damage done to drugs due to the repeated laser ablation. Figure 8 shows the rate of increase in the gene expression. EC represents an amount of laminin in a cell which is not treated with EGF. The value of EC is set to one as a reference value. HC denotes an amount of elastin in cell which is not treated with HGH. Likewise, the value of HC is set to 1. E10 and E100 are the concentrations of laminin in a cell treated with EGF of 10 and , respectively. Similarly, elastin concentration in a cell treated with HGH is denoted as H10 or H100. Four cases (E100 408 mJ, E10 408 mJ, H100 408 mJ, and H10 408 mJ) are considered: growth factor or hormones are contained in a drug reservoir and discharged using a 408 mJEr:YAG laser. The jet containing the growth factor is injected into the cell and the amounts of laminin and elastin are analyzed. Other cases considered (E100 816 mJ, E10 816 mJ, H100 816 mJ, and H10 816 mJ) are done in a similar manner except the laser energy is 816 mJ. The level of the increase in the rate for jet generation (E100 408 mJ, E10 408 mJ, E100 816 mJ, E10 816 mJ, H100 408 mJ, H10 408 mJ, H100 816 mJ, and H10 816 mJ) is marked the same as that of the regular syringe injection (E100, E10, H100, and H10), as shown in Fig. 8. Here, one confirms that there is no thermal damage associated with injection via the present laser-induced microjet injector.