Enzyme-Catalyzed in Situ Synthesis of Temporally and Spatially Distinct CdSe Quantum Dots in Biological Backgrounds

Abstract

The cellular machinery of metal metabolism is capable of making a wide range of inorganic nanoparticles and quantum dots. Individual enzymes from these metabolic pathways are being identified with metal reducing activity, and some have been isolated for in situ particle formation and labeling. We previously identified a glutathione reductase like metalloid reductase (GRLMR) from Pseudomonas moravenis stanleyae with a high affinity for the bioavailable selenium thiolate selenodiglutatione and exhibiting NADPH-dependent reduction of selenodiglutathione to Se(0), initiating the growth of pure selenium metal nanoparticles. In this study, we demonstrate that the GRLMR enzyme can further reduce selenium to a Se(2−) oxidative state, which is capable of nucleating with Cd­(2+) to rapidly form CdSe quantum dots. We show that GRLMR can outcompete background sources of cellular selenium reduction (such as glutathione) and can control the kinetics of quantum dot formation in complex media. The resulting particles are of smaller diameter, with a distinguishingly shifted emission spectrum and superior full width at half-maximum. This study indicates that there is great potential for using GRLMR to study and design enzymes capable of controlled biosynthesis of nanoparticles and quantum dots, paving the way for cellularly assembled nanoparticle biosensors and reporters.

Laboratory Evolution of Metalloid Reductase Substrate Recognition and Nanoparticle Product Size

“…Se 2− is rapidly oxidized to Se 0 by dissolved oxygen. 60 The Se 0 species is essentially insoluble in water, so it has a very high propensity to nucleate and grow into SeNPs. 60 In classical nucleation theory, the critical nucleus size describes the size of a particle at which growth becomes favored over dissolution.…”

“…60 The Se 0 species is essentially insoluble in water, so it has a very high propensity to nucleate and grow into SeNPs. 60 In classical nucleation theory, the critical nucleus size describes the size of a particle at which growth becomes favored over dissolution. Particles larger than the critical nucleus size tend to grow, while particles smaller than the critical nucleus size tend to shrink.…”

Cloneable inorganic nanoparticles

“…Enzyme-catalyzed in situ synthesis of temporally and spatially distinct CdSe quantum dots in biological backgrounds 49 Metal chalcogenide semiconductor nanoparticles are often referred to as quantum dots. This naming reflects the observation that electrons within semiconductor nanoparticles behave like a quantum particle in a box.…”

Biogenesis of Quantum Dots: An Update

“…Then, the blend was incubated on a rotary shaker for a day. (Bao et al ., 2010b) [107] . The QDs were isolated by separation of the microorganisms followed by precipitation of CdTe QDs using isopropanol (50 %).…”

“…(Bao et al, 2010b). [107] The QDs were isolated by separation of the microorganisms followed by precipitation of CdTe QDs using isopropanol (50 %). A 1 : 1 ratio of CdTe QDs and isopropanol was centrifuged at 25000 rpm for 10 min.…”