## 3 Results and Discussion
### In Vitro Transdermal Permeation of Salicylic Acid  
The effect of various electromagnetic field (EMF) configurations on the transdermal permeability of salicylic acid was evaluated using porcine skin and Franz-type diffusion cells over 8 h. These time-dependent effects of electromagnetic field exposure on the cumulative transdermal delivery of salicylic acid are summarized in Figure 3, which illustrates the penetration profiles for each EMF configuration over the 8 h experimental period. Table 3 summarizes the calculated permeation parameters, including the cumulative amount permeated after 24 h (Q24h), steady-state flux (JSS), permeability coefficient (KP), lag time (LT), diffusion coefficient (D), skin partition coefficient (Km), and percentage permeated after 24 h (Q%24h).  
The control sample, which was not exposed to any electromagnetic field, exhibited a cumulative permeation of 335.42 \(\pm\) 38.60 ug and a steady-state flux of 74.29 ug/cm2\({}^{\circ}\)h. Among the tested field types, the statistically significant increased enhancement of salicylic acid permeation was observed in samples treated with pulsed magnetic fields (PMFs), particularly the 5/5 s cycle configuration (5 s on/5 s off), which resulted in the highest permeation (638.75 \(\pm\) 102.54 ug), JSS (132.64 ug/cm2\({}^{\circ}\)h), and KP (13.26 \(\times\) 10\({}^{-3}\) cm/h). This enhancement was accompanied by a relatively short lag time (2.89 h) and moderate values of D and Km, suggesting a favorable balance between skin penetration rate and partitioning.  
Rotating magnetic fields (RMFs) also significantly improved transdermal delivery, especially at higher frequencies (30 Hz and 50 Hz), yielding high flux values (130.18 and 115.20 ug/cm2\({}^{\circ}\)h, respectively) and high permeation efficiencies (Q24h > 330 ug; Q%24h > 3.3%). These effects may be attributed to RMF-induced microfluidic movement within the diffusion medium and structural reorganization within the stratum corneum, facilitating increased drug transport.  
In contrast, oscillating magnetic fields (OMFs) showed limited efficacy in enhancing salicylic acid permeation, particularly at lower frequencies (45 and 55 Hz), which resulted in Q24h values significantly below the control (148.44 \(\pm\) 45.40 ug and 172.93 \(\pm\) 53.55 ug, respectively). Interestingly, the OMF at 65 Hz yielded better results, with improved flux  
Figure 3: The cumulative amount of salicylic acid penetrated through the skin over time under the influence of various electromagnetic field conditions.  
(80.24 \(\mu\)g/cm\({}^{2}\cdot\)h) and permeability (K\({}_{\rm P}\) = 8.02 \(\times\) 10\({}^{-3}\) cm/h), suggesting a frequency-dependent response in the OMF group.  
Static magnetic fields (SMFs) had divergent effects, depending on polarity and voltage. Samples exposed to positive polarity SMFs at higher voltages (15-25 V) demonstrated enhanced permeation compared to other SMF configurations, with Q\({}_{\rm 24h}\) values of 451.03 \(\pm\) 122.69 \(\mu\)g (SMF +15 V) and 268.04 \(\pm\) 39.00 \(\mu\)g (SMF +25 V), significantly higher than those under negative polarity SMFs. The SMF \(-\)5 V and \(-\)15 V variants resulted in the lowest overall permeation (Q\({}_{\rm 24h}\)\(\approx\) 108-129 \(\mu\)g), highlighting the importance of field orientation and intensity in modulating barrier properties.  
The statistical analysis (ANOVA with [PERSON]'s post hoc test, \(\alpha\) = 0.05) revealed significant differences between the control and multiple EMF-treated groups, particularly PMFs and RMFs at optimized settings, which outperformed the control in nearly all permeation parameters.  
Pulsed and rotating magnetic fields significantly enhanced the transdermal delivery of salicylic acid, likely due to their ability to transiently alter the barrier properties of the stratum corneum and improve mass transport. These findings support the potential utility of EMF-based enhancement strategies in topical formulations of ionizable and moderately lipophilic compounds such as salicylic acid.