Versatile Nanoparticle-biomolecule Conjugates for Sensors and Imaging

Applications

The rapid, reliable conjugation of nanoparticles (e.g., semiconductor nanocrystals, quantum dots, nanorods) to biomolecules (e.g., proteins, DNA) is of use in nanoelectronic and nanophotonic devices. Additional applications exist in the generation of fluorescent bioprobes, engineered biosensors, and therapeutic agents. 

Problem Addressed

Existing methods for producing conjugates of nanoparticles and biological molecules (e.g., carbodiimide crosslinker chemistry) are largely inefficient, non-specific, and require multiple steps. This single-step synthetic route uses engineered E. coli to produce molecular linkages that self-assemble to reliably form micron-scale chains of nanoparticle-biomolecule conjugates. The bonds are formed within minutes and are highly specific and stable. 

Technology

Here we describe the production of conjugates between nanoparticles (e.g., semiconductor nanocrystals, quantum dots, nanorods) and biological molecules (e.g., proteins, DNA). In order to generate the conjugates, two separate E.coli constructs are produced. The first E. coli strain generates proteins (e.g., SpyCatcher, Pilin-C) that bind to the surface of nanocrystal shells via cysteine and histidine linkages to form stable, fluorescent nanocrystal-protein conjugates. The second E. coli strain expresses tagged (e.g., SpyTag, isopeptag) amyloid fibrils on its surface. The complementary components of the linkage protein systems (i.e., SpyTag-SpyCatcher; Pilin-C-isopeptag) bind irreversibly when mixed. As such, mixing the two E. coli strains produces conjugates of the fluorescent nanoparticle-protein complex and the tagged amyloid fibril via these molecular linkage proteins. The conjugates can be patterned into higher-order structures by manipulating the expression of the self-assembling amyloid fibrils. The organized, single-step self-assembly of chains of nanoparticles at the micron scale has the potential to expand the applications and potentials of nanoelectronic and nanophotonic devices. 

Advantages

  • Single step synthesis
  • Highly stable conjugates
  • Can be used with a variety of semi-conductor materials
  • Rapid (< 30 minutes) self-assembly of conjugates
  • High binding specificity