Process Control of Multistep Surface Functionalization on Hydroxyethyl Starch Nanocapsules Determines the Reproducibility of the Biological Efficacy.

Nanocarrier synthesis is highly process-dependent, leading to potential batch-to-batch variability if it is not controlled at each step. This variability affects the reproducibility of subsequent biomodification, resulting in unpredictable biological effects, particularly for bioactive molecules such as interleukin-2 (IL-2). Inconsistent conjugation can lead to variable treatment outcomes and severe side effects. Therefore, precise control of each synthesis step is critical for ensuring a consistent quality and biological performance. Our study demonstrates that dividing nanocarrier synthesis into smaller, controlled steps improves reproducibility. Using this method, we achieved highly reproducible, concentration-dependent growth of CTLL-2 cells with hydroxyethyl starch (HES) nanocapsules functionalized with defined amounts of IL-2. We believe that such detailed, stepwise control in nanocarrier synthesis enhances batch consistency, improving the clinical applicability of the drug delivery systems.