Optically Pumped Semiconductor Lasers technology has achieved great success in the market due to its various unique advantages, with over 100000 OPSL devices currently operating in the market. This article introduces the application and new developments of OPSL in the fields of flow cytometry and DNA sequencing.
OPSL has the characteristics of flexible wavelength extension, adjustable power, compact size, high reliability, and high photoelectric conversion efficiency, and has been successfully applied in many life sciences. In addition, OPSL also features low noise, excellent beam quality, direct digital modulation, and fiber coupling options. Its compact structure and intelligent plug and play configuration make it easy to integrate. These characteristics make it perfectly suitable for the fields of flow cytometry and DNA sequencing.
Flow cytometry is an excellent tool for exploring, analyzing, counting, and classifying small particles, including blood cells. The main application areas of cell counting technology are clinical hematology/immunology, and the current relatively new application areas include biofuel research, epidemiology (such as Covid-19), oncology, stem cell research, and pharmaceuticals (supporting rapid high-throughput screening for drug development).
Figure 1 Within numerous flow cytometers, multiple focused lasers cross the flow cell. The photo was provided by Thermo Fisher Scientific.
Instrument manufacturers support these diverse applications through cost-effective desktop instruments. This type of desktop instrument has a universal platform and modular structure, making it easy to achieve factory customization. This modular structure typically includes up to 4 different lasers, a dozen (fluorescence and scattering) detection channels, and multiple input modes, such as microplates for drug development and conventional flow tubes for blood analysis.
It has been proven that plug and play compact laser modules based on OPSL technology (such as the Coherent OBIS series) are highly favored in this field, as these modules are not only convenient for factory customization, but also for instrument upgrades and on-site services. This is because regardless of the wavelength, each device possesses the same optical, mechanical, and electronic properties. The most commonly used wavelengths include 405 nm, 488 nm, 561 nm, and 637 nm. In addition, the digital modulation function of OPSL technology eliminates the cost and complexity of deploying external modulators, supports timing in flow cytometry, and enables multi wavelength laser excitation and detection. Equally important, for end-users from research to clinical use, OPSL's low noise and excellent directional stability can meet their needs for sensitivity and speed.
Instrument manufacturers also hope to improve the performance of multi parameter instruments by using new fluorescent dyes. In larger research instruments, they extend the excitation wavelength to ultraviolet light. The use of ultraviolet excitation expands the bandwidth of multi-color analysis/collection and avoids the use of fluorescent probes for chemical intervention of samples. This is because all living cells contain substances that naturally emit fluorescence after being exposed to ultraviolet light, such as NADH and DNA. For example, sperm can distinguish gender by the amount of endogenous DNA fluorescent substances.
The wavelength extension capability of OPSL technology can flexibly match the required wavelengths for applications, providing excellent support for these two application trends. In addition to OPSL technology, Coherent also uses some other technologies in the OBIS series, including laser diodes and frequency doubling praseodymium (Pr) technology. This allows OBIS series lasers to now have approximately 25 different wavelengths, including four ultraviolet wavelengths: 349 nm, 355 nm, 360 nm, and 375 nm.
The first reading of the human genome was carried out by multiple laboratories, each operating multiple sequencers over a period of more than 10 years, with a total investment of approximately $5 billion. Nowadays, some sequencers can interpret a complete human genome in just one afternoon, with a total cost of approximately $100 to $1000. The innovative technologies of instrument automation and large-scale parallelism have achieved this tremendous change. The new generation sequencer can simultaneously analyze up to hundreds of thousands of DNA strands. There are currently several methods in use, but all commonly used methods are based on laser excitation of fluorescent probes and markers.
Figure 2 Laser based fluorescence excitation is the main detection method in next-generation sequencers and third-generation sequencing technology. This method indicates the addition or reduction of specific bases by emitting wavelength, as shown in this original data trajectory map. The image is provided by Pacific BioSciences.
The scalability of wavelength and power is the main advantage of OPSL. Sequencing depends on whether the fluorescence of four chemical markers (fluorescent dyes) can be excited by laser, targeting one of the four DNA nucleotides ACGT. The accuracy of sequencing depends on whether the four fluorescent dyes can be distinguished, and the sequencing speed depends on whether they can be efficiently excited. Fully improving instrument efficiency means matching the excitation wavelength with the maximum absorption spectrum of each label, rather than attempting reverse matching.
Some methods for sequencing single chains have inherent low signal strength, in which case higher laser power is extremely necessary, especially for applications that often perform large-scale parallel sequencing. In contrast, to avoid losses, some methods only use milliwatt level power. The technological diversity of OBIS lasers is extremely advantageous.
Wavelength: 355nm-1154nm; Power: 10nW-20W
In summary, the application of continuous laser in the field of life sciences is diverse, and each application has a demand for specific lasers. It has been proven that the unique wavelength and power scalability of OPSL technology can effectively address this challenge, thus achieving great success in the market.
Source: Laser Net
