  The use of hyperpolarized agents in magnetic resonance (MR), such as
13C-labeled compounds, enables powerful new imaging and detection modalities
that stem from a 10,000-fold boost in signal. A major challenge for the future
of the hyperpolarizaton technique is the inherently short spin relaxation
times, typically < 60 seconds for 13C liquid-state compounds, which limit the
time that the signal remains boosted. Here, we demonstrate that 1.1% natural
abundance 13C spins in synthetic nanodiamond (ND) can be hyperpolarized at
cryogenic and room temperature without the use of toxic free- radicals, and,
owing to their solid-state environment, exhibit relaxation times exceeding 1
hour. Combined with the already established applications of NDs in the
life-sciences as inexpensive fluorescent markers and non-cytotoxic substrates
for gene and drug delivery, these results extend the theranostic capabilities
of nanoscale diamonds into the domain of hyperpolarized MR.
