Dear Marcia,

In general, 100 ng/uL is not considered a high concentration. We supply our mRNA at 1 mg/mL in 10 mM Tris-HCl, pH 7.5. That said, the mRNA sequence and structure can dictate its solubility. We recommend heating the mRNA for 15 min at 37°C to improve solubility. Long incubations at elevated temperatures should be avoided.

In regards to the diminishing activity of your mRNA, have you checked for degradation?  In addition to the solubility, your issues with mRNA activity may also result from RNA degradation over time. To combat degradation you should use RNase-free reagents and materials and use proper technique. Additionally, we suggest that you aliquot your RNA to limit freeze/thaw cycles.  A higher concentration may also improve stability however  could exacerbate your issues with solubility.

Please let us know if we can help you further.

Regards,

Brea