Protein surface recognition
Protein surface recognition provides an appealing tool to regulate protein-protein interactions and enzymatic activities. We are interested in using nanoparticle receptors to bind protein surfaces through multivalent interactions and then engineer the protein properties. The binding affinity as well as protein stability is tunable by nanoparticle monolayer composition and functionality and buffer ionic strength. Nanoparticle scaffold can induce the secondary structural changes of bound peptides.
Nucleic acid recognition 
The size of nanoparticles is comparable with that of biomacromolecules, providing an efficient scaffold for biomacromolecular binding. We have found that positively charged nanoparticles can associate with DNA molecules to give highly stable complexes, resulting in the interruption of DNA transcription. Additionally, such complex formation can also be exploited to protect the DNA from enzymatic cleavage. The positively charged nanoparticles can act as vectors to transfer DNA into cells.
Drug and gene carriers 
Nanoparticles have also shown promising applications in drug and gene delivery. Drug molecules can be grafted into the monolayer of nanoparticles and subsequently delivered into cells through a charge-mediated endocytosis process. Intracellular glutathione may serve as an effective releasing agent. We have also used photolabile nanoparticles to transport DNA molecules into living cells. The complex stability can be regulated by light and efficient DNA release followed by nuclear internalization is observed upon UV irradiation.
