Blending two bioengineered spider silks to develop cancer targeting spheres.

Bioengineered spider silk is a material that combines superb mechanical properties, biocompatibility and biodegradability with simple production and purification procedures. Moreover, genetic engineering enables the functionalization of silk by adding the sequence encoding the desired attribute. Functionalized silk can self-assemble into spheres that may serve as a carrier for targeted cancer diagnostics/therapy. MaSp1- and MaSp2-based bioengineered silk proteins (MS1 and MS2, respectively) and their anti-cancer oriented hybrid variants were studied. A new approach was applied that blended the two functionalized silk types (MS1 and MS2) at different weight ratios. We selected spheres formed by the blending of functionalized MS1 and MS2 silks at a ratio of 8 : 2 that bound to the target cells at the same level as functionalized MS1 spheres but had greatly improved properties, including size, size distribution, colloidal stability and production efficiency. Compared with functionalized MS1 spheres, functionalized MS1:MS2 particles efficiently killed targeted cells when loaded with a drug inducing considerably lower non-specific toxicity. This study indicates that the blending of silk materials might be advantageous because it combines the most favorable characteristics of both silks and can lead to the formation of an optimal drug delivery vehicle.