Abstract
Brain-derived neurotrophic factor (BDNF) plays a critical role in cognitive processes including learning and memory. However, it has been difficult to detect BDNF in the brains of behaving animals because of its extremely low concentration, i.e., at the sub-nanogram/mL level. Here, we developed an interdigitated microelectrode (IME) biosensor coated with an anti-BDNF an anti-BDNF antibody in a polydimethylsiloxane (PDMS)-based microfluidic channel chip. This sensor could detect BDNF from microliter volumes of liquid samples even at femtogram/mL concentrations with high selectivity over other growth factors. Using this biosensor, we examined whether BDNF is detectable from periodical collection of cerebrospinal fluid microdialysate, sampled every 10 min from the hippocampus of mice during the context-dependent fear-conditioning test. We found that the IME biosensor could detect a significant increase in BDNF levels after the memory task. This increase in BDNF levels was prevented by gene silencing of BDNF, indicating that the IME biosensor reliably detected BDNF in vivo. We propose that the IME biosensor provides a general-purpose probe for ultrasensitive detection of biomolecules with low abundance in the brains of behaving animals.
Highlights
Brain-derived neurotrophic factor (BDNF) is a neurotrophic signalling molecule that is associated with neuronal growth, synapse maturation during development, synaptic plasticity, and axonal targeting[1,2,3,4,5]
The ability to make repeated in vivo measurements of BDNF in the brain has emerged as an important technical challenge, as alterations of BDNF in the cerebrospinal fluid (CSF) can be caused by anxiety and stressors in daily life[12,13]
Because BDNF prepared via microdialysis is diluted by a factor of 10 to 100 by the perfusate[17], high sensitivity and small sample volume consumption are required for the measurement of BDNF in
Summary
Brain-derived neurotrophic factor (BDNF) is a neurotrophic signalling molecule that is associated with neuronal growth, synapse maturation during development, synaptic plasticity, and axonal targeting[1,2,3,4,5]. We evaluated the use of an interdigitated microelectrode (IME) sensor with a microfluidic channel for measurement of BDNF in CSF samples microdialysed from awake, freely moving mice. To maximize sensitivity and reliability, we immobilized the BDNF antibody between the electrodes and compared the IME impedance using more than three IMEs. To accommodate the evaluation of small microliter volumes, we used a polydimethylsiloxane (PDMS)-based microfluidic channel chip in the IME sensor. To accommodate the evaluation of small microliter volumes, we used a polydimethylsiloxane (PDMS)-based microfluidic channel chip in the IME sensor This sensing system was designed to enable simultaneous microdialysis and quantification of BDNF with high sensitivity and consistency
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