The usefulness of the method is demonstrated in
Figure 6 . The purpose of the experiment was to test how much of the IBMX (40 μM when translated to total concentration in the perfusate) loaded into PNIPAAm latex particles modified with HFBMA would be released at room temperature when the latex particles were dissolved in the perfusate. In
Figure 6A , the effect of IBMX on photoresponse kinetics was first measured at three concentrations (10, 30, and 100 μM). The corresponding calibration function is shown in
Figure 6B . After washout of IBMX and recovery of
t p to the original value, perfusion was switched to a solution containing the latex particles loaded with IBMX. There was a clear increase of
t p in the presence of the IBMX-loaded latex particles, although unloaded latex particles alone had no effect (
Fig. 6A , inset). According to the calibration curve, the free IBMX concentration in the perfusate was approximately 25 ± 1 μM, corresponding to approximately two thirds of the total IBMX loaded into the latex particles.