Syngene, a subsidiary of Synoptics Ltd., is a prominent supplier of cutting-edge imaging solutions for life science studies. It focuses on imaging systems for capturing and analyzing images of blots, gels, and plates used in numerous molecular biology practices, such as chemiluminescence, fluorescence, and colorimetric detection.
Charged-Coupled Devices or Complementary Metal-Oxide Semiconductors?
Before exploring the benefits and drawbacks of the different sensors it is crucial to understand what the differences between charged-coupled devices (CCDs) and complementary metal-oxide semiconductors (CMOSs) are.
CCDs and CMOSs are two unique camera sensors. CCD sensor technology has existed for many years. With these sensors, light reaches the sensor and is converted into electrical charges, which are transferred across the sensor and read sequentially, creating high-quality images with low noise levels.
CMOS sensors convert light into electrical signals at every pixel, delivering quicker read-out and less power consumption, which are beneficial characteristics.
Image Credit: Synoptics Ltd
Selecting the correct imaging system for each use is key for obtaining sharp, high-quality images. Both technologies have pros and cons, but which works better for chemiluminescence western blotting relies on several crucial considerations.
This article explores the positives and negatives of CCD and CMOS sensors to assist researchers in determining which is more beneficial for western blotting.
Chemiluminescent western blot detection involves light emission caused by a chemical reaction (HRP and luminol). This light is frequently faint and demands sensitive imaging to capture the bands on the blot.
As detailed below, numerous fundamental elements are involved when assessing CCD against CMOS sensors for this use.
Sensitivity
Sensitivity is perhaps the most significant influence in chemiluminescent imaging, as the produced light is frequently weak.
CCD sensors are the conventional option for imaging low-light levels as they identify low-light levels with minimum noise. They usually have high quantum efficiency, making them more fitting for capturing faint chemiluminescent signals.
CMOS sensors are more modern and have lately experienced several sensitivity enhancements but are believed to be insufficient compared to CCD sensors when identifying exceptionally low-intensity light. For uses demanding extreme sensitivity, CCD sensors typically surpass CMOS.
Noise Performance
Bright bands on a smooth, dark background are ideal when imaging chemiluminescent blots. To accomplish this, a high signal-to-noise ratio (SNR) is required.
CCD sensors excel in creating images with extremely low noise because of how they manage charge transfer. This is crucial for image captures demanding extended exposure time, which is normal for chemiluminescence. CCD sensors often generate images with an elevated SNR.
CMOS sensors usually have higher intrinsic noise than CCD sensors, particularly during extended exposure times. Current CMOS designs have improved radically to reduce noise, but CCD sensors have a major advantage when comparing noise levels.
Dynamic Range
Dynamic range is the sensor’s capability to capture faint and bright signals on the same blot simultaneously. Identifying high- and low-abundance proteins in the same image without saturating the stronger signals is critical in chemiluminescent western blot imaging.
CCD sensors are recognised for their extensive dynamic range, which enables them to capture a wide range of signal intensities. This is because of their high full-well capacity (the maximum amount of charge every pixel in the CCD can store before saturation).
CMOS sensors have progressed in expanding dynamic range, but first-rate CCDs still outshine CMOS here. Some high-end CMOS sensors (high dynamic range) have processing systems that increase the dynamic range, but for chemiluminescence, CCDs’ natural dynamic range gives them superiority.
Sensor Pixel Size
A camera sensor’s pixel size is key in chemiluminescence imaging, directly impacting the SNR and sensitivity and positively affecting chemiluminescent image quality.
Image Credit: Synoptics Ltd
CCD cameras usually have larger pixels than CMOS cameras. The benefit of larger pixels is more surface area to gather photons, increasing the amount of light captured per pixel.
When more photons hit a larger pixel, this produces a stronger signal, enhanced SNR, and improved detection of weaker signals. The read-out noise for larger pixels decreases, promoting sensitivity.
CMOS cameras frequently have smaller pixels, which capture less light and have a reduced region to collect photons. CMOS cameras can also possess decreased full-well capacity, storing less charge before saturation.
Regarding pixel size, CCD sensors triumph over CMOS, but CMOS technology is advancing.
Binning
Binning is an approach where neighboring pixels are combined into a “super-pixel” to enhance sensitivity and increase SNR. The drawback is that this frequently causes resolution loss.
In CCDs, binning happens during charge transfer. When adjacent pixels are binned, their electrical charges are joined before being read to enable the sensor to collect more light in the binned pixel region. This increases sensitivity and decreases read-out noise, as the noise is directed to the whole binned area instead of each pixel.
This creates a cleaner signal with reduced background noise, which benefits weak signals such as chemiluminescent Western blots.
In CMOS sensors, binning usually occurs after each pixel has read out the signal. As the read-out noise is applied to each pixel before binning, the noise level stays higher than CCD sensors.
While binning can still enhance signal strength by merging neighboring pixels, CMOS binning does not typically lower the noise as efficiently as CCD binning.
Speed and Frame Rates
Although speed is not of utmost importance in chemiluminescent Western blot imaging (as it usually demands extended exposure times), it can still be fundamental when doing high-throughput experiments or requiring rapid image acquisition.
CCDs, especially high-sensitivity cooled CCDs, are usually slower due to how the charges are transferred and delivered.
CMOS sensors are developed for high-speed read-outs. Each pixel can be read independently, enabling more rapid image capture than CCDs. If speed is of importance, CMOS techniques are more beneficial.
Which is Better for Chemiluminescent Western Blots?
Choosing between CCD and CMOS sensors for imaging chemiluminescent Western blots relies on the experiment’s particular demands and precedence.
A CCD camera is superior if crucial concerns include sensitivity, low noise, and broad dynamic range, and you work with low signals (e.g., low-abundance proteins). CCDs remain the benchmark for high-sensitivity purposes like chemiluminescent Western blots as they capture faint signals with minimum noise.
A CMOS camera could be a more reasonable solution for those who prioritise cost-efficiency, speed, easy-to-use routine or high-throughput experiments, and have strong enough signals.
CMOS cameras are progressing quickly and can still deliver outstanding images for most Western blot purposes, particularly if sensitivity is of lesser concern.
Understanding each sensor type’s strength enables selecting an imaging system that aligns with research requirements and delivers publication-quality results.
This information has been sourced, reviewed and adapted from materials provided by Synoptics Ltd.
For more information on this source, please visit Synoptics Ltd.