2.1. Synthesis of SPED

Silica particles with encapsulated DNA synthesis (S1 and S2) was performed in adaption of Paunescu et al. ²³ and characterized regarding DNA load, size, and shape. For DNA encapsulation, 4 × 4 ml of silica nanoparticles (110 nm, 50 mg/ml in isopropanol; Pinfire) per batch were surface‐functionalized in 4 separate falcon tubes by adding 40 µg of N‐trimethoxysilylpropyl‐N,N,N‐ trimethylammonium chloride (TMAPS) (50% wt in methanol; abcr) followed by 12 h of stirring at 900 rotations per minute (rpm) at room temperature. For DNA adsorption to the surface, a 2 ml batch of 150 ng/µl corresponding annealed DNA (sequences see Table 2; Microsynth AG) was added to 200 ml ultrapure water (mQ; type 1, 18.2 MΩ·cm at 24°C, Milli‐Q^®; Merck). 0.4 g of the functionalized particles were added to the DNA solution and shaken for 10 s. Subsequently, 4 µl TMAPS were added, then the mix was shaken and sonicated for 20 s. Next, 62.5 µl of tetraethyl orthosilicate (TEOS) (≥99.0%; Sigma‐Aldrich) were added, followed by 5 h of shaking at 600 rpm on a mixer (Vibramax 100; Heidolph) with a universal clamping attachment (VX 8; IKA). In a further step, 10 ml isopropanol and 5.9 ml TEOS were mixed with 484.1 ml mQ water and combined with the previous mixture. The batch was again stirred at 600 rpm for 4 days, before washing twice with water.

DNA sequences encapsulated in silica for SPED synthesis