Bimodal porous superparticles with the optimized structure prepared by self-limited aggregation of PEG-coated mesoporous nanofibers for purification of protein–dye conjugates

Abstract

Herein, we report the preparation of micrometer-sized superparticles with bimodal pore distributions and the surfaces being coated with PEG, and their successful application for selective removal of unreacted organic dyes from protein–dye conjugates after the protein labeling reaction (superparticles are the dispersible particles prepared by self-assembly of primary nanoparticles). Starting from polymeric nanofibers with a PEG shell and a cross-linked P4VP core, deposition of negatively charged mesoporous silica (mSiO₂) onto the positively charged nanofibers endows the nanofibers with mesopores and neutralizes the positive charge of the nanofibers. The neutralization results in self-limited aggregation of the hybrid nanofibers into superparticles of tens of micrometers in size, and the stacking of the hybrid nanofibers leads to an open and continuous channel of above 50 nm in size within the superparticles, to which the mesopores are exposed. Furthermore, we confirmed that, the surface of the hybrid nanofibers within the superparticles is still coated by PEG chains. When applied for purifying the protein–dye conjugates, the micrometer-sized superparticles can be conveniently separated from the solutions, the mesopores adsorb the unreacted organic dyes, the stacking macropores accelerate mass transport within the superparticles, and the PEG coating prevents non-specific adsorption of proteins; the superparticles have optimized structures for the purification. In the model systems, the unconjugated dye can be removed completely after adsorption by the superparticles, while more than 97% of the protein–dye conjugates remain in the final solution. The whole process of purification took less than 10 min.