Quantum Dots and Gold Nanoparticles as Scaffolds for Enzymatic Enhancement: Recent Advances and the Influence of Nanoparticle Size

Abstract

Nanoparticle scaffolds can impart multiple benefits onto immobilized enzymes including enhanced stability, activity, and recoverability. The magnitude of these benefits is modulated by features inherent to the scaffold–enzyme conjugate, amongst which the size of the nanoscaffold itself can be critically important. In this review, we highlight the benefits of enzyme immobilization on nanoparticles and the factors affecting these benefits using quantum dots and gold nanoparticles as representative materials due to their maturity. We then review recent literature on the use of these scaffolds for enzyme immobilization and as a means to dissect the underlying mechanisms. Detailed analysis of the literature suggests that there is a “sweet-spot” for scaffold size and the ratio of immobilized enzyme to scaffold, with smaller scaffolds and lower enzyme:scaffold ratios generally providing higher enzymatic activities. We anticipate that ongoing studies of enzyme immobilization onto nanoscale scaffolds will continue to sharpen our understanding of what gives rise to beneficial characteristics and allow for the next important step, namely, that of translation to large-scale processes that exploit these properties.

The power of electrified nanoconfinement for energising, controlling and observing long enzyme cascades

“…1a) will enhance the supply of reactants and release of products, an unfortunate consequence being that intermediates escape more easily. Nonetheless, for dispersed systems, it is relatively straightforward to extend established enzyme kinetic models to address systematic influences of nanoconfinement, in particular, of substrate channeling 8,11,[15][16][17][18]42 . Second, and in various systematic bottom-up approaches, the scaffolds and attached enzymes can be preassembled to give structures with known enzyme composition and intersite distances: such an ideal situation is difficult to achieve in pre-deposited tight nanopores, where enzyme cascade composition and intersite distances are currently probabilistic.…”

“…In such a way, the local concentration of each enzyme is massively increased, and in what is often termed substrate channeling, intermediates can be prevented from escaping and the distances they must travel between catalyst partners are minimized. Nanoconfining a package of enzymes in synthetic materials [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] brings these advantages to new technologies where cascade reactions are already attractive [21][22][23][24][25][26][27][28][29] : furthermore, approaches such as directed evolution are producing individual enzymes for completely new functions to increase chemical complexity [30][31][32] . Enzyme cascades are valuable also for synthesis because they offer several advantages such as a decrease in purification steps and quick removal of inhibitory/toxic intermediates 25 .…”

Catalytic Kinetics Considerations and Molecular Tools for the Design of Multienzymatic Cascade Nanoreactors

“…Moreover, QDs are easily biofunctionalized via metal-affinity coordination with polyhistidine tagged proteins . [96] Kang et.al conjugated CdSe-ZnS QDs with the series of enzymes (MenF, MenD, and MenH) that are collectively involved in the menaquinone (also called Vitamin K2) biosynthesis . [97] The enzymes were immobilized via metal-histag affinity driven selfassembly.…”

Direct and Efficient Conjugation of Quantum Dots to DNA Nanostructures with Peptide-PNA

“…This method further enabled highly precise immobilization of QDs, to within a few nanometers of the desired DNA location, as indicated by the FRET measurements, avoiding the bulky and flexible biotin−streptavidin strategy most often realized for QDs. Additionally, the high attachment efficiencies demonstrated here have been achieved with a low peptide-PNA surface density, making this an ideal strategy for immobilization of QDs functionalized with other biological materials such as enzymes for enhanced catalysis 49 or dye-labeled peptides for FRET-based biosensing. 50,51 The success of this strategy may allow for additional properties that can be incorporated through PNA conjugations such as improved rigidity, protection from higher temperatures, and improved resistance to enzyme degradation.…”