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In brain and neuroscience research, optogenetics and fiber photometry techniques are becoming increasingly important in modulating neurons and detecting changes in their activity. Selecting the appropriate fiber-optic cannulas for efficient and accurate optical stimulation and recording will become very important.
The fiber-optic cannula—mainly in optogenetic and fiber photometry experiments, are fixed and implanted in specific brain regions through a brain stereotaxic instrument, and then connected to optical fibers through ceramic sleeves.
Referring to the ceramic ferrule structure, it can be divided into two parts, the optical fiber, and the fiber ferrule. In the experiment, the optical fiber is implanted in the target brain region of
Ceramic ferrule is an important carrier for direct implantation into animal brain tissue, giving relevant light stimulation and receiving light signals.
Here’s how to choose a fiber-optic cannula that’s just right for you.
01 Spot-uniformity
The best state for a fiber-optic cannulas is that the spot is uniform and shown as a regular circle. Non-uniform light spots exhibit non-uniform light intensities, which may result in different intensities of neuron stimulation in irradiated brain regions. This leads to the influence of the accuracy of the experiment both in the optogenetics and the fiber photometry experiment, which will affect the final experiment result.
02 Transmission Efficiency
The transmission efficiency refers to the ratio of the light output power at the tip of the optical fiber to the light output power at the end of the fiber cable. Generally speaking, when the transmission efficiency is ≥80%, the luminous power of the fiber-optic cannulas can be considered qualified. The optical power value can be measured by a laser power meter.
03 Fiber ferrule end quality
The identification of the fiber ferrule end mainly observes whether the end surface is smooth and flat and whether there is residual polishing fluid. The end is connected to the end of the fiber cable through a ceramic sleeve. If there are scratches, the connection may not be tight, which will affect the laser transmission efficiency. The residual polishing liquid may enter the aperture of the ceramic end surface, further affecting the light transmission efficiency. A polished and well-preserved cannula with clean and clear end faces without scratches is a qualified one.
In terms of ceramic pin technology, since some scratches and dirt are invisible to the naked eye, subtle scratches and dirt are very obvious under the microscope. It is necessary to use a microscope to observe whether the end surface is clean, smooth, and flat.
04 Optical fiber end quality
The fiber tip needs to be checked to see if its surface is clean, tidy, and whether there is any residue of polishing fluid. The clear and regular surface can ensure that the output spot is round and the light intensity is uniform. Since the polishing liquid is an industrial product, it is necessary to ensure that no polishing liquid remains after the cannula is polished, otherwise it may cause inflammation of the rodent brain, which will affect the progress and results of the experiment.
