This article is sponsored by CoolLED.

Is it time to upgrade your fluorescence microscope illumination system?

You might not give the light source for widefield fluorescence much consideration, but more and more research and development laboratories are modernising by replacing toxic and energy-hungry mercury and metal halide lamps with LED illumination technology. Here we explain why, and explore some of the benefits of high-performance LED illumination systems designed especially for fluorescence microscopy.

Simply better control: Unlike lamps, LEDs are solid state which opens the way to sophisticated control options to allow careful optimisation of settings and precise automation. Options include lightning-fast switching between individual channels, 0-100% irradiance modulation, and operation through popular imaging software. Some systems now enable high-speed imaging without expensive motorised components (Figure 1), increasing temporal resolution for fast screening of multiple samples or capturing dynamic events in live samples, which also minimises phototoxicity and photobleaching¹. Operation is simple, with no bulb replacement and a once-only alignment required to ensure homogenous illumination over the field of view.

Cost and energy efficiency: LEDs are highly efficient. For example, white light sources now typically exhibit above 30% efficiency, whereas traditional lamps are mostly below 10%. Unlike lamps, they do not need to be left switched on all day to ensure availability. This saves money, and cost savings of over £30,000 have been calculated where energy efficiency is a key factor².

Sustainability: This aspect has become increasingly significant, as more organisations focus on meeting sustainability targets. Vastly improved energy efficiency helps organisations meet Scope 3 carbon emissions targets, which are emissions arising from their supply chain. Additional sustainability benefits include the substantially longer lifetime and a lack of toxic mercury, which is also a factor in staff safety. The popular CoolLED four-LED pE-400 Series is even ACT Label Certified by My Green Lab, which is like an eco-nutrition label that helps scientists and laboratory managers make sustainable purchasing decisions.

Stability: Precise output translates to precise and reliable data over time, even years, and LEDs offer superior stability compared to lamps (Figure 2). Adding to stability, improved efficiency also results in less aging of a liquid light guide – or direct fit models are available with some systems such as the CoolLED pE-400 Series which removes the need for a liquid light guide completely.

Keeping up to date with LED technology

LED illumination systems for fluorescence microscopy became commercially available in 2006. Since then, the technology has evolved at a rapid pace, overcoming historic limitations such as spectral range and irradiance.

Wavelengths are now available from 340nm up to 770nm in LED illumination systems, and this flexibility futureproofs as new fluorophores emerge. Irradiance has also come a long way, in part thanks to active cooling technology in the most advanced systems. This holds the LEDs at a constant temperature and enables irradiance levels up to five times greater than standard LED illumination systems. Good thermal management means LEDs can be driven more powerfully to increase irradiance, whilst maintaining stability, reliability and lifetime. This also lowers energy consumption.

Customised LED illumination systems

LED illumination is ideal for high content screening (HCS) systems, and manufacturers of this equipment are increasingly moving towards customised LED illumination systems for their setups. Several of the benefits already mentioned are particularly relevant here, such as energy efficiency which will have a bigger impact when the system is running around the clock. CoolLED’s successful off-the-shelf Illumination Systems are available as customised systems, adapted to suit the requirements of individual automated fluorescence systems. The choice of control options enables efficient automation, and the LEDs will be tailored to the applications. Moreover, since LED illumination can be tightly controlled in discrete channels right across the spectrum, fluorophores can be multiplexed in a single sample to maximise the information from each assay. The stability is another factor, and precision is once again vital when analysing and directly comparing many samples.

Summary

Modern LED illumination systems for widefield fluorescence microscopes really are more than just a light source. There are a wide range of benefits from performance to sustainability which can be realised by upgrading this component, and there are many options available. For example, the 4-channel CoolLED pE-400^max is ideal for everyday fluorescence, while the lightning-fast 8-channel pE-800 is optimised for live cell imaging – and customised versions of these products are available for equipment manufacturers too.

For more information, visit www.coolled.com or contact info@coolled.com

References

1. CoolLED (2020). Capturing high-speed multi-labelled events with LED illumination systems.
2. Green Light Laboratories (2017). Mercury versus LED study.