Publications

@article{Burgess2020-ss,

title = {Covalent attachment of active enzymes to upconversion phosphors 

 allows ratiometric detection of substrates},

author = {Letitia Burgess and Hannah Wilson and Alex R Jones and Peter Harvey and Louise S Natrajan and Sam Hay},

year  = {2020},

date = {2020-11-01},

journal = {Chemistry},

volume = {26},

number = {65},

pages = {14817\textendash14822},

publisher = {Wiley},

abstract = {Upconverting phosphors (UCPs) convert multiple low energy 

 photons into higher energy emission via the process of photon 

 upconversion and offer an attractive alternative to organic 

 fluorophores for use as luminescent probes. Here, UCPs were 

 capped with functionalized silica in order to provide a surface 

 to covalently conjugate proteins with surface-accessible 

 cysteines. Variants of green fluorescent protein (GFP) and the 

 flavoenzyme pentaerythritol tetranitrate reductase (PETNR) were 

 then attached via maleimide-thiol coupling in order to allow 

 energy transfer from the UCP to the GFP or flavin cofactor of 

 PETNR, respectively. PETNR retains its activity when coupled to 

 the UCPs, which allows reversible detection of enzyme substrates 

 via ratiometric sensing of the enzyme redox state.},

keywords = {biosensors, energy transfer, enzymes, lanthanides, upconversion},

pubstate = {published},

tppubtype = {article}

}

@article{Radu2020-iu,

title = {Dynamic quantum sensing of paramagnetic species using 

 nitrogen-vacancy centers in Diamond},

author = {Valentin Radu and Joshua Colm Price and Simon James Levett and Kaarjel Kauslya Narayanasamy and Thomas David Bateman-Price and Philippe Barrie Wilson and Melissa Louise Mather},

year  = {2020},

date = {2020-03-01},

journal = {ACS Sens.},

volume = {5},

number = {3},

pages = {703\textendash710},

publisher = {American Chemical Society (ACS)},

abstract = {Naturally occurring paramagnetic species (PS), such as free 

 radicals and paramagnetic metalloproteins, play an essential 

 role in a multitude of critical physiological processes 

 including metabolism, cell signaling, and immune response. These 

 highly dynamic species can also act as intrinsic biomarkers for 

 a variety of disease states, while synthetic paramagnetic probes 

 targeted to specific sites on biomolecules enable the study of 

 functional information such as tissue oxygenation and redox 

 status in living systems. The work presented herein describes a 

 new sensing method that exploits the spin-dependent emission of 

 photoluminescence (PL) from an ensemble of nitrogen-vacancy 

 centers in diamond for rapid, nondestructive detection of PS in 

 living systems. Uniquely this approach involves simple 

 measurement protocols that assess PL contrast with and without 

 the application of microwaves. The method is demonstrated to 

 detect concentrations of paramagnetic salts in solution and the 

 widely used magnetic resonance imaging contrast agent gadobutrol 

 with a limit of detection of less than 10 attomol over a 100 

 μm $times$ 100 μm field of view. Real-time monitoring 

 of changes in the concentration of paramagnetic salts is 

 demonstrated with image exposure times of 20 ms. Further, 

 dynamic tracking of chemical reactions is demonstrated via the 

 conversion of low-spin cyanide-coordinated Fe3+ to hexaaqua Fe3+ 

 under acidic conditions. Finally, the capability to map 

 paramagnetic species in model cells with subcellular resolution 

 is demonstrated using lipid membranes containing 

 gadolinium-labeled phospholipids under ambient conditions in the 

 order of minutes. Overall, this work introduces a new sensing 

 approach for the realization of fast, sensitive imaging of PS in 

 a widefield format that is readily deployable in biomedical 

 settings. Ultimately, this new approach to nitrogen 

 vacancy-based quantum sensing paves the way toward minimally 

 invasive real-time mapping and observation of free radicals in 

 in vitro cellular environments.},

keywords = {diamond, lanthanides, nitrogen vacancy, paramagnetic, photoluminescence, quantum sensing},

pubstate = {published},

tppubtype = {article}

}