Application of keratinocyte monolayer-based bioassay to show enhanced bioavailability of ginseng polysaccharides nanoparticles

Panax quinquefolius (North Am. ginseng), is known to contain ginsenosides and polysaccharides (PS). The latter has low bioavailability due to its high hydrophilicity and large molecular size. We have prepared various nanoparticles of ginseng PS (NPPS) and we were able to show enhanced skin penetration and protection against UV-induced skin injury compared to regular PS. In this study, we established an in vitro skin model to study the topical bioavailability of ginseng PS and NPPS. The model consists of HaCaT keratinocytes cultured in a transwell insert with the apical and basolateral side in contact with media. The test materials (PS and NPPS) were added to the apical compartment and sample was collected over a period of 24 hours from the basolateral compartment to determine the accumulation of the test material. Due to the lack of chromophores on ginseng PS molecules, it is difficult to quantite PS. To address this, two analytical methods were used.1. Bioassay based on stimulation of nitrite production by RAW 264.7 cells: it was shown that at similar collection times, the stimulatory effect of NPPS was greater than that of PS. 2. The use of 5-fluorescein-labelled PS and, the measurement of fluorescence intensity to determine analyte concentrations and distribution in vitro. Both methods were able to show seven-fold higher penetration of NPPS across keratinocyte monolayer. Data also suggests that penetration by NPPS was not time dependant. These results in vitro are consistent with our previous in vivo observations in hairless mice after topical application.