Study Of Complex Light Shaping And Photoacoustic Microscopy For Optical Manipulation Of Cells Into Deep Tissue In Living Animals

Direct imaging and manipulation of individual cells in living animals are highly desirable but challenging for biomedical research.Such technologies play a key role in studying the structure and function of cells and the interaction between cells and tissues in a natural environment,further facilitating insights into the thrombogenesis,metastases of tumor,etc.In 1980s,the invention of the laser tweezers provided a great tool for these studies due to its ability of noninvasive manipulation of individual cells.Recently,the optical tweezers technique has enabled the trapping and manipulation of red blood cells within capillaries in living mice,which creates a new area of optical tweezers for in-vivo research.However,all these studies have so far been limited to the superficial layer of tissue because most biological tissues are highly scattering and the focused Gaussian beam cannot go deeper into the tissues,holding back the actual applications.Besides,the in-vivo manipulation technology involves optical imaging in deep tissues,which also suffers the tissue-scattering problem.It is found that the spatial light engneering brings potential solutions to these issues.In order to achieve optical manipulation in deep tissue in vivo,this thesis focused on the studies of complex wavefront shaping and photoacousitc microscopy technologies.The spectific work and progresses achieved in this thesis including:1.Complex light shaping techniques.The dynamic wavefront shaping techniques are desired for optical manipulation in vivo because the biological tissue is more complicated and always changes dynamically.In this thesis,we proposed and demonstrated some approaches for complex wavefront shaping with a digital micromirror device.Engineering the amplitude,phase,polarization and spatial coherence of the light fields was demonstrated.These methods were then exploited for experimental generation and characteration of various structured light beams.2.Novel optical manipulation with structured light beams.To overcome the limitation of conventional optical tweezers,we combined the optical trapping with structured light beams to realize new trapping configurations.Some new structured beams,for example,optical bottles and symmetric cusp beams,were proposed to trap and manipulate special microparticles.These novel trapping configurations were further exploited for biomedical applications,for example,killing cancer cell.3.Novel photoacousitc microscopy technique in vivo.Based on the complex light shaping,a synthetic-light-needle photoacoustic microscopy(SLN-PAM)was proposed to overcome the strong scattering of biological tissues and to achieve deep tissue imaging.SLN-PAM has a spatially-invariant lateral resolution over a large depth of field.Notably,the lateral resolution of SLN-PAM beats the diffraction limit of the objective lens,achieving sub-diffraction resolution.As a demonstration,a DMD based SLN-PAM prototype was built and applied for volumetric imaging of zebrafish larvae in vivo.The findings and progesses obtained in this thesis will help overcome the limitations of the conventional optical tweezers and lay a foundation for the next step to optical manipulation and imaging of individual cells within deep tissues in vivo.In addition,the novel concepts and approaches proposed here will open up new opportunities for potential applications in optics,biomedical and clinical sciences,etc.