Improving molecule distribution and accumulation for enhanced intra-spheroid delivery in a progressive manner via...

Drug delivery plays a crucial role in both in-vitro and in-vivo biomedical applications. The complexity of the in-vivo conditions, such as cell-to-microenvironment and cell-to-cell interactions, presents challenges for effective delivery at the tissue and organ level. Various techniques have been developed to improve the delivery efficiency, ranging from physical assistance to biochemical carriers. Of which, combined electric pulses have been successfully employed to enhance the delivery in vivo, though the mechanisms of this process remain inadequately understood. In this study, the improvement on the molecule distribution and progressive delivery dynamics was elucidated in a 3D-cultured spheroid model using modulated electric field, which leveraged an optimized pulse combination of high voltage, short duration pulses (HSP) and low voltage, long duration pulse (LLP). The results demonstrated that modulated electric pulses (MEP strategy) promoted the intra-spheroid distribution and accumulation of molecules though transient delivery was not observed during pulse implementation. The roles of different pulse components were investigated which showed synergistic effects of reversible membrane electroporation and temporary disturbance of intercellular junction proteins, like ZO-1 and E-cadherin. The oriented and asymmetric motion of charged molecules was regulated as well by using LLP. Besides, we validated the enhancement over molecules with different sizes and charges. These findings may provide helpful perspectives for optimizing drug delivery in more complex biological systems and realistic delivery environments.