『Cover Story』 New Breakthrough in Femtosecond Laser: Real-Time "Scalpel" for Precise Manipulation of Organelles!

《22 May 2025》

Seohee Ma, Bin Dong, Matthew G. Clark, R. Michael Everly, Shivam Mahapatra, Chi Zhang

The cover of this issue of Small Science features the work by Professor Zhang Chi from Purdue University, titled "Real-Time and Site-Specific Perturbation of Dynamic Subcellular Compartments Using Femtosecond Pulses."  

Research Background  

• In the field of life sciences, a deep understanding of the interaction between lasers and intracellular subcellular structures is of critical importance. It is not only a core element driving optical microscopy toward higher resolution and more precise imaging but also enables more effective therapeutic approaches for phototherapy and serves as the foundation for precise regulation of cellular functions in optogenetics.  
• Currently, continuous-wave lasers primarily rely on linear absorption mechanisms, which have significant limitations in achieving precise manipulation of specific intracellular structures. Although femtosecond (fs) lasers, with their nonlinear multiphoton absorption characteristics, can concentrate energy at the laser focus, providing high axial precision, existing femtosecond laser delivery methods face numerous challenges. On one hand, these methods cannot accurately target dynamically changing molecular entities or automatically select targets, making it difficult to achieve real-time and effective perturbation of frequently moving or complexly distributed biomolecules within cells. On the other hand, existing techniques separate laser pulse delivery from the imaging process, preventing the synchronous recording of cellular responses during laser perturbation and greatly limiting the study of dynamic cellular processes.  

Research Significance  

• This study innovatively introduces the femtosecond real-time precision optical control (fs-RPOC) technology, which ingeniously combines laser-scanning microscopy with a closed-loop feedback mechanism to achieve automated and chemically selective perturbation of subcellular structures. This breakthrough overcomes many limitations of traditional techniques and brings transformative changes to cell biology research.  
• The fs-RPOC technology demonstrates exceptional performance advantages. It offers extremely high spatial precision, enabling fine microsurgery on dynamic targets at the level of individual organelles or even suborganelles, while also allowing precise local molecular regulation. By applying pulse selection methods, this technology can independently and flexibly control the average and peak laser power at any subcellular structure, providing a powerful tool for studying the effects of different laser parameters on cells.  
• Using mitochondria as the research target, fs-RPOC technology has made significant discoveries. It revealed a series of processes induced by femtosecond lasers, including the formation of reactive oxygen species, H₂O₂ diffusion, and the generation of low-density plasma, leading to site-specific molecular responses in mitochondria. These findings not only provide new perspectives and theoretical foundations for understanding the interaction between femtosecond lasers and subcellular structures but also demonstrate the immense potential of fs-RPOC technology in precisely regulating molecular and organelle functions. This technology is expected to advance multiple related fields, such as optical microscopy, phototherapy, and optogenetics, offering more precise and effective technical means for disease treatment and cell biology research.  

Research Outlook  

• In the future, fs-RPOC technology holds broad development prospects and vast exploration potential. In terms of expanding its application scope, it can be further applied to more types of cells and biological models to study its regulatory effects on different organelles and biomolecules, comprehensively evaluating the technology's universality and applicability in the life sciences. This will help deepen the understanding of complex and diverse intracellular physiological processes and pathological mechanisms, providing richer targets and strategies for disease diagnosis and treatment.  
• Another important future research direction is to delve into the molecular mechanisms of the interaction between femtosecond lasers and subcellular structures. Detailed studies on the effects of laser parameters, such as pulse width, wavelength, and repetition rate, on cellular responses will provide solid theoretical support for optimizing technical parameters, thereby further enhancing the precision and effectiveness of fs-RPOC technology.  
• Integrating fs-RPOC technology with other advanced techniques, such as single-cell sequencing (which can analyze cellular changes at the genetic level after laser perturbation) and super-resolution imaging (which can provide higher-resolution cellular structural information), will enable comprehensive and multi-level analysis of cells following laser perturbation. This multi-technique approach will reveal dynamic intracellular changes and molecular regulatory mechanisms more deeply.  
• Conducting translational research on fs-RPOC technology for clinical applications is also crucial. Through preclinical studies, evaluating the safety and efficacy of this technology in areas such as cancer treatment and neurodegenerative disease therapy will help move this cutting-edge technology from laboratory research to clinical application, offering new treatment hopes and better outcomes for patients.
  
  

Cover design process

• The cover design is closely aligned with the paper’s theme—utilizing femtosecond pulses to achieve real-time and site-specific perturbation of dynamic subcellular compartments. The central visual depicts a femtosecond laser beam (represented as a ray of light) acting upon the interior of a cell. A laser-emitting device, designed to resemble a mechanical arm, targets specific intracellular structures such as mitochondria, visually demonstrating the subcellular precision manipulation technology described in the paper. The rendering of internal cellular structures, along with annotations of elements like reactive oxygen species (ROS) and low-density plasma (LDP), further emphasizes the various effects generated during the laser-cell interaction, echoing the research content of the paper.
• The overall color scheme employs deep blue and bluish-purple as the dominant tones, creating a profound and technologically sophisticated atmosphere that aligns with the professional image of a scientific journal. The internal structures of the cell are highlighted in more vivid colors such as purple and orange, drawing attention to key organelles and molecular reaction zones and enabling readers to quickly focus on the core content. The laser beam is rendered in light blue, which contrasts with the background to clearly illustrate its propagation path and direction of action.