A very exciting application of DDS is in cancer treatment. Nanogels have been widely investigated to deliver therapeutic agents specifically to solid tumors to improve efficacy and reduce the severe adverse side effects of cancer treatments. Their mechanical properties were shown to influence the circulation time of the nanoparticles in the blood, their spatiotemporal distribution, tumor penetration and interaction with cancer cells. Soft nanoparticles were shown to persist longer in the vasculature than stiffer counterparts. In accordance, stiffer nanoparticles were found to have superior retention in the spleen compared to soft nanoparticles. This difference was attributed to the ability of soft nanoparticles to squeeze through barriers of the vasculature (including spleen, liver) and remain longer in the blood circulation compared to the low deformable stiff nanoparticles. Therefore, decreasing nanoparticle elasticity was already suggested to reduce their blood clearance and improve their tumor targeting. Soft nanoparticles were also found to achieve a higher penetration depth in tumors .
Overall, the mechanical properties play an important role in different steps of the DDS development and application. The release of the drug can be correlated with the progressive degradation of the polymeric matrix within the body. Tuning the initial mechanical properties and the stability of the matrix can be used to achieve optimal rates of drug release. In the case of nanoparticles, their stiffness can affect their blood availability, tumor targeting and penetration.
A number of DDS are already applied in clinics and the advancements in biomaterials and their characterization tools have broadened the field even more. With the increasing biomaterials systems and target applications, the impact of this technology is likely to increase in the coming years: further changing the scale, efficacy and cost of therapeutics, and improving human health care.
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