Advanced {ELISA}-like biosensing based on ultra-large pore silica microbeads

In this work, functionalized porous silica-based materials, widely used in the literature as drug and biomolecule nanocarriers, were innovatively used as an effective three-dimensional (3D) substrate for the development of a specific biomolecular assay showing great versatility in terms of detection performance. One-pot synthesis of ultralarge-pore silica microbeads was optimized to develop an enzyme-linked immunosorbent (ELISA)-like DNA detection assay. Cocondensation synthesis enabled introducing thiol functionalities into the silica framework while preserving both the high specific surface area (560 m2/g) and large pore size (17 nm average diameter), which are essential to guaranteeing high loading capability. Indeed, the bead-capturing ability was proved by developing an ELISA-like assay for the detection of short DNA sequences (≈20 bp), both in labeled and label-free configurations. In particular, the suppression of unspecific binding on the bead surface by testing two different blocking agents was a matter of interest. The detection performances were evaluated and compared to the ones obtained by following the same detection protocol on a standard flat surface (two-dimensional, 2D), which is most commonly used for this purpose. The bead-based assay showed a limit of detection two times lower than the flat-surface assay, confirming the promising capturing ability due to the larger active surface area. Furthermore, compared to traditional ELISA, the bead-based assay showed an intrinsic larger dynamic range that can be tailored depending on the final amount of beads used for the colorimetric quantification.