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In neuroscience research, optogenetics and fiber photometry techniques are becoming increasingly popular in modulating and detecting neural activity. Selecting the appropriate fiber-optic cannula for efficient and accurate optical stimulation and recording is crucial for a successful study design.
The fiber-optic cannula are mainly used in optogenetic and fiber photometry experiments. The optic fibers are implanted in brain regions through a stereotaxic instrument and then connected to optical fibers through ceramic sleeves.
The optic fiber mainly consist of the optical fiber and the Ceramic ferrule. In the experiment, the optical fiber is implanted in the target brain region of the animal to transmit excitation light or receive fluorescence. And the Ceramic Ferrule serve as a base for connection to a patch cord through plastic sleeves.
When purchasing your Fiber-Optic Cannula, there are three main parameters to consider:
The Ferrule Diameter of you Fiber-Optic Cannula should simply match the dimension of the connector on your patch cable. Ferrules on the Optic Cannula used for neuroscience has a diameter of either Φ1.25 mm or Φ2.5 mm.
The Optical property of your Ferrule is an important factor that is often over looked. For fiber photometry experiments, auto fluorescence from the ferrule can often elevate the signal floor and increase noise for your signal. Pick low auto-florescence ferrule and use black ferrules when in a pinch to yield the best signal.
The Diameter of the Fiber Core should match that of your patch cable, or any patch cord you use to relay light from your implant site to your light source or senor. This is required for the maximal efficiency during transduction, and will result in the best experimental result.
Another factor to consider when picking your optic fiber diameter is the trade off between signal strength and damage to brain tissue. Fibers with higher diameters have better signals but also causes the most damage when inserted into deep brain regions.
A good rule of thumb we use at RWD Life Science is to use 400um optic fibers for superficial brain regions to ensure the best signal, and to use 100um – 200um fibers for deep brain regions.
The Numerical Aperture (NA) value of your fiber is also an important parameter as it determines the range of tissue that is recorded or stimulated from the fiber tip. Bigger NA values means wider recording or stimulation area.
01 Spot-uniformity
The best state for a fiber-optic cannula 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.
Fiber-Optic Cannula is a sensitive piece of equipment. It is generally a good idea to check your optic fiber before implant, especially if your fiber have been dropped during handling. Here is a few things to look for when checking your fiber:
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 cannula can be considered qualified. The optical power value can be measured by a laser power meter.
Fiber ferrule end quality
The ideal Ferrule surface should be smooth and flat with no polishing fluid remaining. The Ferrule end is connected to the patch cable through a ceramic sleeve. Any scratches or unevenness will affect the tightness of the connection, which will affect the laser transmission efficiency. The residual polishing liquid may enter the recording sleeve, further affecting the light transmission efficiency. A polished and well-preserved cannulae should have a clean and clear end faces without scratches.
Although scratches and dirt are invisible to the naked eye, scratches are very obvious under the microscope. It is necessary to use a microscope to observe whether the end surface is clean, smooth, and flat.
At RWD Life Science. Every Fiber-Optic Cannula is polished and double checked by at least 3 highly trained technicians. This level of attention to detail is what is required to delivery assurance of results to labs around the world.
Features：
• Material: Ceramic, Optical fiber
• Type: White Series/Black Series
• Applicable wavelength: 400-2200nm
• Core diameter: 100um, 200um, 300um, 400um
• Numerical aperture: 0.22, 0.39,0.50
• Outer diameter: 1.25mm (6.4mm long), 2.5mm (10.5mm long)
• Optical fiber length: 2mm-25mm (Φ1.25mm),2mm-20mm (Φ2.5mm).step
0.5mm (Other lengths can be customized)
• Low auto-fluorescence
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