Direct electron transfer glutamate biosensor using platinum nanoparticle and carbon nanotubes
A direct electron transfer amperometric biosensor fabricated using direct write printing technology for in vivo electrochemical monitoring, such as monitoring of neurotransmitters and other biomarkers, e.g., in traumatic spinal cord injury. The biosensor is fabricated by immobilizing glutamate oxidase on nanocomposite electrodes made of platinum nanoparticles, multiwall carbon nanotubes and a conductive polymer on a flexible substrate.
1 . An implantable biosensor comprising a nanocomposite electrode comprising:
a plurality of platinum nanoparticles in a nanocomposite ink;
a plurality of multiwall carbon nanotubes in the nanocomposite ink; and
a conductive polymer in the nanocomposite ink, on a flexible substrate, wherein a greater amount of the conductive polymer is present in the nanocomposite ink than an amount of either or both of the plurality of platinum nanoparticles or the plurality of multiwall carbon nanotubes in the nanocomposite ink such that the conductive polymer forms a binder, while also decreasing tunneling distance,
wherein said nanocomposite electrode comprises glutamate oxidase on its surface and detects L-glutamate via direct electron transfer in response signal to an applied potential.
2 . The implantable biosensor of claim 1 , which detects L-glutamate by amperometric response signal to the applied potential.
3 . The implantable biosensor of claim 2 , which quantifies L-glutamate by the amperometric response signal.
4 . The implantable biosensor of claim 1 , wherein said conductive polymer comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and said flexible substrate comprises one or more of an Ecoflex polydimethylsiloxane (PDMS) composite and a liquid crystal polymer sheet (LCP).
5 . The implantable biosensor of claim 4 , wherein said platinum nanoparticles are 1% wt, said multiwall carbon nanotubes are 1% wt and said substrate Ecoflex PDMS composite is 16% wt.
6 . The implantable biosensor of claim 1 , further comprising a layer of Nafion on its surface upon which the glutamate oxidase enzyme is immobilized.
7 . The implantable biosensor of claim 1 , wherein said applied potential is between 650 mV and −200 mV.
8 . The implantable biosensor of claim 1 , which is sensitive to an L-glutamate concentration of 12.85 nA μM −1 mm −2 .
9 . A method of detecting L-glutamate in a subject, comprising:
providing a biosensor, wherein said biosensor comprises a nanocomposite electrode comprising:
a plurality of platinum nanoparticles in a nanocomposite ink;
a plurality of multiwall carbon nanotubes in the nanocomposite ink; and
a conductive polymer in the nanocomposite ink, on a flexible substrate, wherein a greater amount of the conductive polymer is present in the nanocomposite ink than an amount of either or both of the plurality of platinum nanoparticles or the plurality of multiwall carbon nanotubes in the nanocomposite ink such that the conductive polymer forms a binder while also decreasing tunneling distance,
wherein said nanocomposite electrode comprises glutamate oxidase on its surface; applying a potential to the biosensor;
reading an amperometric response signal generated from direct electron transfer on the nanocomposite electrode surface in response to the applied potential; and
detecting L-glutamate in the subject based on the amperometric response signal.
10 . The method of claim 9 , wherein the biosensor is implanted in the subject.
11 . The method of claim 10 , wherein the subject is human.
12 . The method of claim 9 , further comprising measuring a level of L-glutamate in the subject based on the amperometric response signal.
13 . The method of claim 12 , further comprising determining a risk of traumatic spinal cord injury (SPI) based on the level.
14 . The method of claim 13 , further comprising treating the subject based on the level.
15 . The method of claim 9 , wherein said conductive polymer comprises poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and said flexible substrate comprises one or more of an Ecoflex polydimethylsiloxane (PDMS) composite and a liquid crystal polymer sheet (LCP).
16 . The method of claim 15 , wherein said platinum nanoparticles are 1% wt, said multiwall carbon nanotubes are 1% wt and said substrate Ecoflex PDMS composite is 16% wt.
17 . The method of claim 9 , wherein the nanocomposite electrode further comprises a layer of Nafion on its surface upon which the glutamate oxidase enzyme is immobilized.
18 . The method of claim 9 , wherein said applied potential is between 650 mV and −200 mV.
19 . The method of claim 9 , wherein the L-glutamate concentration is 12.85 nA μM −1 mm −2 or less.
20 . The method of claim 9 , wherein the subject has experienced a traumatic spinal cord injury (SPI).